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WO2024221435A1 - 硅碳复合材料及其制备方法、负极极片、二次电池和用电装置 - Google Patents

硅碳复合材料及其制备方法、负极极片、二次电池和用电装置 Download PDF

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WO2024221435A1
WO2024221435A1 PCT/CN2023/091726 CN2023091726W WO2024221435A1 WO 2024221435 A1 WO2024221435 A1 WO 2024221435A1 CN 2023091726 W CN2023091726 W CN 2023091726W WO 2024221435 A1 WO2024221435 A1 WO 2024221435A1
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silicon
composite material
carbon composite
carbon
battery
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PCT/CN2023/091726
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English (en)
French (fr)
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叶永煌
云亮
孙信
林逵
吴李力
董苗苗
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2023/091726 priority Critical patent/WO2024221435A1/zh
Publication of WO2024221435A1 publication Critical patent/WO2024221435A1/zh

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  • the present application relates to the technical field of secondary batteries, and in particular to a silicon-carbon composite material, a preparation method thereof, a negative electrode sheet, a secondary battery and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • Negative electrode active materials are important components of secondary batteries. In order to further improve the energy density of batteries, silicon-based negative electrode active materials have been widely studied. However, due to their large volume expansion, silicon-based materials will affect the electrochemical performance of the battery during use.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a silicon-carbon composite material, which has excellent electron transmission performance, is beneficial to reducing the fast charging time of the battery, increasing the number of battery cycles, and can improve the battery's rate performance and cycle performance, and comprehensively improve the battery's electrochemical performance.
  • the first aspect of the present application provides a silicon-carbon composite material, including a porous carbon skeleton; a silicon-based material, at least partially arranged in the pores of the porous carbon skeleton; and a doping element, at least part of which is distributed in the porous carbon skeleton; wherein the doping element satisfies: the lithium ion diffusion coefficient of the doping element at 25°C is greater than the lithium ion diffusion coefficient of silicon at 25°C.
  • silicon-carbon composite materials have a stable porous skeleton structure with strong support capacity, which is manifested as high stress resistance, and have excellent mechanical properties and conductivity; the pore structure in the porous carbon skeleton provides more space for setting silicon particles, which can be used for Large amounts of silicon can be stored; when the porous carbon skeleton is compounded with silicon particles, the silicon particles are not easy to agglomerate and can be evenly dispersed in the pores of the porous carbon skeleton; after the porous carbon skeleton is compounded with silicon particles, the conductivity of the silicon-carbon composite material can be improved, and at the same time, the volume effect of silicon in the process of lithium insertion and extraction can be alleviated, and the stress changes of silicon-based materials can be fully withstood, thereby ensuring the structural stability of the silicon-carbon composite material, improving the cycle stability and lithium storage capacity of the silicon-carbon composite material, and extending the cycle life of the battery; on the other hand, doping the silicon-carbon composite material with an element
  • the lithium ion diffusion coefficient of the doping element at 25°C is greater than 10-14 cm2 /S, optionally greater than 10-14 cm2 /S and less than or equal to 10-13 cm2 /S; and/or the lithium ion diffusion coefficient of the silicon at 25°C is less than 10-14 cm2 /S, optionally greater than 10-15 cm2 / S and less than 10-14 cm2 /S.
  • the doping element includes at least one of Sn, Ge, Sb, Bi, and Sr.
  • the lithium ion diffusion coefficients of the above-mentioned doping elements at 25°C are all greater than the lithium ion diffusion coefficient of silicon at 25°C, and can all be doped into the silicon-carbon composite material, thereby reducing the migration barrier and migration energy of lithium ions in the silicon-carbon composite material, increasing the lithium ion solid phase diffusion coefficient of the silicon-carbon composite material, improving the migration kinetics of lithium ions, improving the rate performance of the battery, and improving the kinetic performance of the battery.
  • At least part of the doping elements form grains in the silicon-carbon composite material; optionally, the size of the grains is less than or equal to 10 nm, and more optionally 3 nm-7 nm.
  • the doping elements exist in the silicon-carbon composite material in the form of grains. Compared with the doping elements existing in an amorphous form, the grain state can effectively improve the electronic and ionic conductivity of the doping elements, further improve the conductivity of the material, and improve the rate performance of the battery.
  • controlling the grain size formed by the doping elements in the silicon-carbon composite material within a suitable range is conducive to reducing the migration barrier and migration energy of lithium ions in the silicon-carbon composite material, greatly improving the solid phase diffusion coefficient of lithium ions in the silicon-carbon composite material, and improving the migration kinetics of lithium ions. Improve the rate performance of the battery.
  • the doping elements exist in the form of small-sized grains, which will not cause major changes in the silicon-carbon structure, nor will it cause major changes in the phase properties of the material. It can well maintain the structural stability of the material, and is not easy to pulverize during the charge and discharge process, thus improving the cycle performance of the battery and extending the cycle life of the battery.
  • the mass fraction of the doping element is less than or equal to 7%, and may be 1%-3%.
  • Controlling the mass fraction of doping elements within an appropriate range can not only reduce the migration barrier and migration energy of lithium ions in silicon-carbon composite materials, and significantly improve the solid-phase diffusion coefficient of lithium ions in silicon-carbon composite materials, but also avoid the internal structure of the material being changed due to excessively high mass fraction of doping elements, which affects the battery cycle performance.
  • Doping elements with an appropriate mass content range can take into account both battery rate performance and cycle performance, and comprehensively improve battery performance.
  • the porous carbon framework is spherical or spheroidal.
  • the spherical or quasi-spherical porous carbon skeleton is beneficial to forming a smooth void structure in the negative electrode film layer, improving the solid-phase diffusion rate and liquid-phase transmission performance of lithium ions, enhancing the battery's fast charging capability, and improving the battery's rate performance.
  • the mass fraction of the silicon-based material is greater than or equal to 30%, and can be optionally 35%-50%; and/or, based on the total mass of the silicon-carbon composite material, the mass fraction of the porous carbon skeleton is greater than or equal to 30%, and can be optionally 40%-60%.
  • the mass content of the silicon-based material is within an appropriate range, so that the silicon-carbon composite material has a high gram capacity, thereby improving the energy density of the battery.
  • the volume expansion of the silicon-carbon composite material is limited to a certain range, so that the silicon-carbon composite material has a certain structural stability.
  • Controlling the mass fraction of silicon-based materials within an appropriate range can take into account both the battery's cycle performance and energy density.
  • the mass content of the porous carbon skeleton is within a suitable range, so that the silicon-carbon composite material has a sufficient porous carbon skeleton to accommodate the silicon-based material and the doping elements, and the silicon-based composite material has a high gram capacity.
  • the mass content of the porous carbon skeleton is within a suitable range, which can improve the conductivity of the silicon-carbon composite material and improve the kinetic performance of the battery.
  • the battery's cycle performance, rate performance and energy density can be taken into account.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material is less than or equal to 5 ⁇ m, and can be optionally 1 ⁇ m-3 ⁇ m.
  • Controlling the volume distribution particle size Dv50 of the silicon-carbon composite material within an appropriate range is beneficial to further reduce the solid phase migration path of lithium ions in the silicon-carbon composite material and improve the battery rate performance.
  • the silicon-carbon composite material satisfies at least one of the following (1)-(4):
  • the specific surface area of the porous carbon skeleton is 1000m 2 /g-2500m 2 /g;
  • the pore size of the porous carbon skeleton is 0.5nm-100nm
  • the pore volume of the porous carbon framework is 0.5 cm 3 /g-8.5 cm 3 /g;
  • the volume distribution particle size Dv50 of the porous carbon skeleton is 0.3 ⁇ m-5 ⁇ m.
  • Controlling the specific surface area, pore size, pore volume and particle size of the porous carbon skeleton within a suitable range facilitates the uniform distribution of silicon-based materials and doping elements, and the battery has excellent cycle performance and rate performance, and the battery has a high energy density.
  • the silicon-carbon composite material has a carbon layer on at least a portion of its surface.
  • the carbon layer coated on the silicon-carbon composite material is beneficial to improving the conductivity of the silicon-carbon composite material and improving the rate performance of the material. At the same time, the carbon layer can also enhance the stability between the silicon-carbon composite material and the electrolyte and improve the cycle performance of the battery.
  • a second aspect of the present application provides a method for preparing a silicon-carbon composite material, comprising the following steps:
  • a lithium ion diffusion coefficient of a single substance of the doping element at 25° C. is greater than a lithium ion diffusion coefficient of a single substance of silicon at 25° C.
  • the silicon-carbon composite material is obtained by depositing a silicon-based material in the pores of the porous carbon skeleton.
  • the silicon-carbon composite material obtained in the above preparation method has a stable porous bone
  • the porous carbon skeleton has a strong supporting capacity, which is manifested in a high stress capacity, and has excellent mechanical properties and electrical conductivity; the pore structure in the porous carbon skeleton provides more space for setting silicon particles, and can be used for large-scale silicon storage; when the porous carbon skeleton is composited with silicon particles, the silicon particles are not easy to agglomerate and can be evenly dispersed in the pores of the porous carbon skeleton.
  • the electrical conductivity of the silicon-carbon composite material can be improved, and the volume effect of silicon in the process of lithium insertion and extraction can be alleviated, and the stress changes of silicon-based materials can be fully withstood, the structural stability of the silicon-carbon composite material is ensured, the cycle stability and lithium storage capacity of the silicon-carbon composite material are improved, and the cycle life of the battery is extended; on the other hand, doping the silicon-carbon composite material with an element whose lithium ion diffusion coefficient is greater than that of silicon alone is beneficial to reducing the migration barrier and migration energy of lithium ions in the silicon-carbon composite material, greatly improving the lithium ion solid phase diffusion coefficient of the silicon-carbon composite material, improving the migration kinetics of lithium ions, and improving the battery rate performance.
  • the preparation of the porous carbon skeleton includes solvothermal reaction, activation pore formation and high temperature carbonization.
  • Solvothermal reaction mixing a resin containing an unsaturated group and/or a sugar, a solvent, and an aqueous solution containing a doping element, and performing a solvent thermal reaction to obtain a first product;
  • Activation pore creation introducing water vapor into the first product to perform activation pore creation treatment to obtain the second product;
  • High temperature carbonization The second product is subjected to high temperature carbonization treatment to obtain a porous carbon skeleton.
  • the above preparation method can obtain a porous carbon skeleton, and the preparation method is simple and easy to industrialize and apply.
  • reaction temperature of the solvothermal reaction is 400° C.-750° C.; and/or the reaction time of the solvothermal reaction is 4 h-10 h.
  • the structural parameters of the porous carbon skeleton such as volume distribution particle size Dv50, specific surface area, pore size and pore volume, can be controlled within a suitable range, which is beneficial to the subsequent deposition of silicon-based materials.
  • the mass ratio of the resin containing unsaturated groups to the sugar is (2:8)-(9:1), and can be optionally (4:6)-(6:4).
  • the porous carbon skeleton has a suitable specific surface area, pore size, pore volume and particle size, which is beneficial to the subsequent deposition of silicon.
  • the resin containing unsaturated groups includes at least one of phenolic resin, furfural resin, and lignin-based activated carbon; and/or the sugar includes at least one of sucrose, glucose, and chitosan.
  • the treatment temperature of the activation pore-forming is 400° C.-500° C.; and/or, the treatment time of the activation pore-forming is 4 h-8 h; and/or, the flow rate of the water vapor is 0.5 g/min-1 g/min.
  • the deposition temperature of the vapor deposited silicon is 500° C.-900° C.; and/or the deposition time of the vapor deposited silicon is 6 h-24 h.
  • the deposition time and temperature of vapor-deposited silicon are controlled within a suitable range so that silicon is evenly dispersed in the pores of the porous carbon skeleton, and the silicon-carbon composite material has excellent structural parameters.
  • the preparation method further comprises preparing a carbon layer
  • Carbon coating treatment is performed on the surface of the silicon-carbon composite material.
  • the carbon layer coated on the surface of the silicon-carbon composite material is beneficial to improving the conductivity of the silicon-carbon composite material and improving the rate performance of the material. At the same time, the carbon layer can also enhance the stability between the silicon-carbon composite material and the electrolyte and improve the cycle performance of the battery.
  • the third aspect of the present application provides a negative electrode plate, which includes a negative electrode collector and a negative electrode film layer arranged on the surface of the negative electrode collector, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes the silicon-carbon composite material described in the first aspect of the present application or the silicon-carbon composite material prepared according to the preparation method described in the second aspect of the present application.
  • a fourth aspect of the present application provides a secondary battery, comprising the negative electrode plate of the third aspect of the present application.
  • a fifth aspect of the present application provides an electrical device, comprising the secondary battery of the fourth aspect of the present application.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • FIG. 7 is a scanning electron microscope image of the porous carbon skeleton shown in Example 1 of the present application.
  • ranges are defined in the form of lower limits and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined in this way can be inclusive or exclusive of the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also expected.
  • the numerical range “ab” represents an abbreviation of any real number combination between a and b, where a and b are both real numbers.
  • the numerical range "0-5" means All real numbers between "0-5" have been listed in this application, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application are open-ended or closed-ended.
  • the “include” and “comprising” may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • Silicon-carbon composite material is one of the commonly used active materials. At present, the preparation of silicon-carbon composite materials mainly involves mixing silicon directly with carbon materials. These silicon-carbon materials need to have certain restrictions on the silicon content. When the silicon content is too high, the expansion is still large, which will cause the electrode structure to be damaged and the cycle life of the battery to be deteriorated. In addition, the conductivity of the silicon-carbon composite material itself is poor, which seriously limits its further application. Therefore, it is necessary to design a new silicon-carbon composite material to meet the needs of the new generation of electrochemistry.
  • the present application proposes a silicon-carbon composite material, including a porous carbon skeleton; a silicon-based material, at least part of the silicon-based material is arranged in the pores of the porous carbon skeleton; and a doping element, at least part of the doping element is distributed in the porous carbon skeleton; wherein the doping element satisfies: the lithium ion diffusion coefficient of the doping element at 25°C is greater than the lithium ion diffusion coefficient of silicon at 25°C.
  • the silicon-carbon composite material has a stable porous skeleton structure with strong supporting capacity, which is manifested as high stress resistance, and has excellent mechanical properties and conductivity; the pore structure in its porous carbon skeleton provides more space for the deposition of silicon particles and can be used for large-scale silicon storage; when silicon is deposited on the porous carbon skeleton, the silicon particles are not easy to agglomerate and can be evenly dispersed in the pores of the porous carbon skeleton; after the porous carbon skeleton is composited with silicon particles, the conductivity of the silicon-carbon composite material can be improved, the rate performance of the material can be improved, and the volume effect of silicon in the process of lithium insertion and extraction can be alleviated, and the stress changes of silicon particles can be fully withstood to ensure the structural stability of the silicon-carbon composite material; on the other hand, doping the silicon-carbon composite material with an element whose lithium ion diffusion coefficient is greater than that of silicon element is beneficial to reducing the migration barrier and migration energy of lithium
  • the silicon-carbon composite material of the present application can reduce the fast charging time of the battery, improve the rate performance of the battery, increase the number of cycles of the battery, extend the cycle life of the battery, and comprehensively improve the performance of the battery.
  • silicon-carbon composite material refers to a material in which the mass content of silicon element and carbon element are both greater than 10% based on the total mass of the silicon-carbon composite material.
  • porous carbon framework means that the main component of the framework is carbon and the framework contains a plurality of pores.
  • the porous carbon skeleton structure of the silicon-carbon composite material can be tested using equipment and methods known in the art. For example, it can be tested by using a scanning electron microscope (such as ZEISS Sigma 300). As an example, the following steps can be followed: first, the negative electrode sheet containing the silicon-carbon composite material is cut into a sample to be tested of a certain size (such as 6mm ⁇ 6mm), clamp the sample to be tested with two conductive and heat-conductive thin sheets (such as copper foil), stick the sample to be tested and the thin sheets with glue (such as double-sided tape), press with a certain mass (such as about 400g) of flat iron block for a certain time (such as 1h) to make the gap between the sample to be tested and the copper foil as small as possible, then trim the edges with scissors, stick it on the sample stage with conductive glue, and the sample slightly protrudes from the edge of the sample stage.
  • a scanning electron microscope such as ZEISS Sigma 300.
  • the sample stage into the sample holder and lock it, turn on the power of the argon ion cross-section polisher (such as IB-19500CP) and evacuate it, set the argon gas flow (such as 0.15MPa) and voltage (such as 8KV) and polishing time (such as 2 hours), adjust the sample stage to the swing mode to start polishing, and after polishing, use a scanning electron microscope (such as ZEISS Sigma 300) to obtain the ion polishing cross-sectional morphology (CP) picture of the sample to be tested.
  • the argon gas flow such as 0.15MPa
  • voltage such as 8KV
  • polishing time such as 2 hours
  • lithium ion diffusion coefficient refers to an important parameter used to characterize the kinetic behavior of a material, which is manifested in that the larger the diffusion coefficient of the material, the better the large current discharge capability of the battery, the higher the power density of the material, and the better the high-rate performance.
  • the type of "doping element” in the present application refers to an element whose lithium ion diffusion coefficient of a single substance formed by the element is greater than the lithium ion diffusion coefficient of a single substance of silicon.
  • the lithium ion diffusion coefficient of a material has a well-known meaning in the art and can be tested by methods known in the art.
  • the lithium ion diffusion coefficient of a single material composed of doped elements is measured by constant current intermittent titration (GITT) in this application.
  • the lithium ion diffusion coefficient of the single substance of the doping element at 25° C. is greater than 10 ⁇ 14 cm 2 /S, and may be greater than 10 ⁇ 14 cm 2 /S and less than or equal to 10 ⁇ 13 cm 2 /S.
  • the lithium ion diffusion coefficient of silicon at 25° C. is less than 10 ⁇ 14 cm 2 /S, and may be greater than 10 ⁇ 15 cm 2 /S and less than 10 ⁇ 14 cm 2 /S.
  • the lithium ion diffusion coefficient of the simple substance of the doping element at 25° C. may be any value of 2 ⁇ 10 -14 cm 2 /S, 3 ⁇ 10 -14 cm 2 /S, 4 ⁇ 10 -14 cm 2 /S, 5 ⁇ 10 -14 cm 2 /S, 6 ⁇ 10 -14 cm 2 /S, 7 ⁇ 10 -14 cm 2 /S, 8 ⁇ 10 -14 cm 2 /S, 9 ⁇ 10 -14 cm 2 /S, 10 -13 cm 2 /S, or a range consisting of any two of them.
  • the lithium ion diffusion coefficient of silicon at 25° C. may be any value selected from 2 ⁇ 10 -15 cm 2 /S, 3 ⁇ 10 -15 cm 2 /S, 4 ⁇ 10 -15 cm 2 /S, 5 ⁇ 10 -15 cm 2 /S, 6 ⁇ 10 -15 cm 2 /S, 7 ⁇ 10 -15 cm 2 /S, 8 ⁇ 10 -15 cm 2 /S, 9 ⁇ 10 -15 cm 2 /S or more. The range of any two values.
  • the doping element includes at least one of Sn, Ge, Sb, Bi, and Sr.
  • the doping element includes at least two of Sn, Ge, Sb, Bi, and Sr.
  • the doping element may include Sn and Ge, Sn and Sb, Sn and Bi, Sn and Sr, Ge and Sb, Ge and Bi, Ge and Sr, Sb and Bi, Sb and Sr, or Bi and Sr.
  • the above doping elements have excellent lithium ion diffusion coefficients, can effectively improve the conductivity of silicon-carbon composite materials, and improve the rate performance of batteries.
  • the raw materials are abundant and easy to obtain, suitable for various batteries, and have excellent application prospects.
  • At least a portion of the doping element forms grains in the silicon-carbon composite material.
  • doping elements in crystalline form have better electronic and ionic conductivity, which can effectively improve the conductivity of silicon-carbon composite materials and improve the rate performance of batteries.
  • the size of the grains is less than or equal to 10 nm.
  • the size of the grains is well known in the art and can be tested by methods known in the art.
  • an X-ray powder diffractometer XRD
  • the model of the X-ray powder diffractometer is the American X'pertPROo.
  • the detailed test process of the grain size is as follows: a. Measurement of the actual width Bm of the silicon-carbon composite material sample. Set the instrument scanning rate to 2 degrees/minute, obtain the XRD spectrum of the sample to be tested, use the JADE software to deduct the CuKa2 background, and obtain the Bm of each diffraction peak; b. Instrument broadening Bs measurement.
  • the size of the grains may be selected to be any one of less than or equal to 0.1 nm, less than or equal to 0.5 nm, less than or equal to 1 nm, less than or equal to 1.5 nm, less than or equal to 2 nm, less than or equal to 2.5 nm, less than or equal to 3 nm, less than or equal to 3.5 nm, less than or equal to 4 nm, less than or equal to 4.5 nm, less than or equal to 5 nm, less than or equal to 5.5 nm, less than or equal to 6 nm, less than or equal to 6.5 nm, less than or equal to 7 nm, less than or equal to 7.5 nm, less than or equal to 8 nm, less than or equal to 8.5 nm, less than or equal to 9 nm, less than or equal to 9.5 nm, or less than or equal to 10 nm.
  • Controlling the grain size formed by the doping elements in the silicon-carbon composite material within a suitable range is conducive to reducing the migration barrier and migration energy of lithium ions in the silicon-carbon composite material, greatly improving the solid-phase diffusion coefficient of lithium ions in the silicon-carbon composite material, improving the lithium ion migration kinetics, and improving the rate performance of the battery.
  • the doping elements exist in the form of small-sized grains, which will not cause major changes in the silicon-carbon structure, will not cause major changes in the phase characteristics of the material, can well maintain the structural stability of the material, is not easy to pulverize during the charge and discharge process, improve the cycle performance of the battery, and extend the cycle life of the battery.
  • the size of the grains may be 3 nm to 7 nm.
  • the size of the grains may be 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, or a value in a range consisting of any two of the above points.
  • Controlling the grain size within an appropriate range will help further increase the battery's cycle times and discharge time, reduce the battery's fast charge time, and further improve the battery's rate performance and cycle performance.
  • the mass fraction of the doping element is less than or equal to 7%, based on the total mass of the silicon-carbon composite material.
  • the mass content of the doping element can be tested by methods and equipment known in the art, for example, it can be measured with reference to EPA 6010D-2014 standard; specifically, ICP-OES (element analysis-inductively coupled plasma emission spectrometry) can be used for testing, firstly dissolving the sample to be tested into liquid with a strong acid, and then introducing the liquid into an ICP light source by atomization.
  • the gaseous atoms to be tested are further ionized and excited in a strong magnetic field, and then recover from the excited state to the ground state; in the above process, energy is released and recorded as different characteristic spectral lines for quantitative element analysis.
  • the mass fraction of the doping element can be selected to be any one of less than or equal to 1%, less than or equal to 1.5%, less than or equal to 2%, less than or equal to 2.5%, less than or equal to 3%, less than or equal to 3.5%, less than or equal to 4%, less than or equal to 4.5%, less than or equal to 5%, less than or equal to 5.5%, less than or equal to 6%, less than or equal to 6.5%, and less than or equal to 7%.
  • Doping elements with a suitable mass content can improve the electrical conductivity of silicon-carbon composite materials, improve the lithium ion transmission capacity of the material, and improve the cycle performance and rate performance of the battery. At the same time, doping elements with a suitable mass content will not change the internal structure and crystal phase of the material, thereby improving the cycle performance of the battery.
  • the mass fraction of the doping element is 1%-3%, based on the total mass of the silicon-carbon composite material.
  • the mass fraction of the doping element may be 1%, 1.5%, 2%, 2.5%, 3% or a value in a range consisting of any two of the above points.
  • Controlling the mass content of the doping elements within an appropriate range will help further increase the battery's cycle times and discharge time, reduce the battery's fast charging time, and further improve the battery's rate performance and cycle performance.
  • the porous carbon framework is spherical or spheroidal.
  • the term "spherical" means that the distance from the center of the sphere to any point on the sphere is equal.
  • the term "quasi-spherical" means that the distance from the center of the sphere to the farthest point on the sphere is R1, the distance from the center of the sphere to the closest point on the sphere is R2, and the absolute value of the difference between R1 and R2 divided by the average value of R1 and R2 is less than 1%.
  • the spherical or quasi-spherical porous carbon skeleton is beneficial to forming a smooth void structure in the negative electrode film layer, improving the solid-phase diffusion rate and liquid-phase transmission performance of lithium ions, enhancing the battery's fast charging capability, and improving the battery's rate performance.
  • the mass fraction of the silicon-based material is greater than or equal to 30%, based on the total mass of the silicon-carbon composite material.
  • the mass content of silicon-based materials can be tested by methods and equipment known in the art, for example, it can be measured with reference to EPA 6010D-2014 standard; specifically, ICP-OES (elemental analysis-inductively coupled plasma optical emission spectrometry) testing can be used.
  • the sample to be tested is first dissolved into a liquid with a strong acid, and then the liquid is introduced into an ICP light source by atomization.
  • the gaseous atoms to be tested are further ionized and excited in a strong magnetic field, and then recovered from the excited state to the ground state. In the above process, energy is released and recorded as different characteristic spectral lines for elemental quantitative analysis.
  • the mass fraction of the silicon-based material may be selected to be any one of greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 45%, and greater than or equal to 50%.
  • the mass content of the silicon-based material is within a suitable range, so that the silicon-carbon composite material has a high gram capacity, thereby improving the energy density of the battery.
  • the volume expansion of the silicon-carbon composite material is limited to a certain range, so that the silicon-carbon composite material has a certain structural stability, and the battery has a high energy density and excellent cycle performance.
  • the mass fraction of the silicon-based material is 35%-50%, based on the total mass of the silicon-carbon composite material.
  • the mass fraction of the silicon-based material may be selected to be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or a value in the range formed by any two of the above points.
  • Controlling the mass fraction of silicon-based materials within an appropriate range can balance the energy density and cycle life of the battery and comprehensively improve the performance of the battery.
  • the mass fraction of the porous carbon skeleton is greater than or equal to 30%, based on the total mass of the silicon-carbon composite material.
  • the mass fraction of the porous carbon skeleton can be selected as any one of greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 45%, and greater than or equal to 50%.
  • the mass content of the porous carbon skeleton can be tested by methods and equipment known in the art, for example, it can be measured with reference to EPA 6010D-2014 standard; specifically, ICP-OES (elemental analysis-inductively coupled plasma optical emission spectrometry) testing can be used.
  • the sample to be tested is first dissolved into a liquid with a strong acid, and then the liquid is introduced into an ICP light source by atomization.
  • the gaseous atoms to be tested are further ionized and excited in a strong magnetic field, and then recovered from the excited state to the ground state. In the above process, energy is released and recorded as different characteristic spectral lines for elemental quantitative analysis.
  • the mass content of the porous carbon skeleton is within a suitable range, so that the silicon-carbon composite material has a sufficient porous carbon skeleton to accommodate the silicon-based material and the doping elements, and the silicon-based composite material has a high gram capacity.
  • the mass content of the porous carbon skeleton is within a suitable range, which can improve the conductivity of the silicon-carbon composite material and improve the kinetic performance of the battery.
  • the mass fraction of the porous carbon skeleton may be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, or a value in a range consisting of any two of the above points.
  • the battery's cycle performance, rate performance and energy density can be taken into account.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material is less than or equal to 5 ⁇ m.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material can be selected to be any one of less than or equal to 1 ⁇ m, less than or equal to 1.5 ⁇ m, less than or equal to 2 ⁇ m, less than or equal to 2.5 ⁇ m, less than or equal to 3 ⁇ m, less than or equal to 3.5 ⁇ m, less than or equal to 4 ⁇ m, less than or equal to 4.5 ⁇ m, and less than or equal to 5 ⁇ m.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material is well known in the art and can be tested by methods known in the art.
  • the silicon-carbon composite material sample is measured according to the GB/T 19077-2016/ISO 13320:2009 standard, and the testing equipment can be a laser particle size analyzer (such as Malvern Master Size 3000).
  • the volume distribution particle size Dv50 of the silicon-carbon composite material is controlled to be less than or equal to 5 ⁇ m, so that the silicon-carbon composite material has a shorter lithium ion solid phase migration path, further improving the battery's multiple rate performance and improve the kinetic performance of the battery.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material is 1 ⁇ m-3 ⁇ m.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material can be selected as 1 ⁇ m, 1.2 ⁇ m, 1.4 ⁇ m, 1.5 ⁇ m, 1.6 ⁇ m, 1.8 ⁇ m, 2 ⁇ m, 2.2 ⁇ m, 2.4 ⁇ m, 2.5 ⁇ m, 2.6 ⁇ m, 2.8 ⁇ m, 3 ⁇ m, or a value in the range formed by any two of the above points.
  • Controlling the volume distribution particle size Dv50 of the silicon-carbon composite material to 1 ⁇ m-3 ⁇ m is beneficial to further increase the discharge time of the battery and reduce the fast charging time of the battery, improve the battery's rate performance, and improve the battery's kinetic performance.
  • the porous carbon framework has a specific surface area of 1000 m 2 /g to 2500 m 2 /g.
  • the specific surface area of the porous carbon skeleton may be 1000 m2 /g, 1100 m2 /g, 1200 m2 /g, 1300 m2/g, 1400 m2 /g, 1500 m2 /g, 1600 m2 /g, 1700 m2 /g, 1800 m2 /g, 1900 m2 /g, 2000 m2/g, 2100 m2 /g, 2200 m2 /g, 2300 m2 /g, 2400 m2 / g, 2500 m2 /g, or a value in a range consisting of any two of the above points.
  • the specific surface area of the porous carbon skeleton is a well-known meaning in the art and can be tested by methods known in the art.
  • the specific surface area of the porous carbon skeleton is tested using a 3Flex specific surface area analyzer from Mack, USA.
  • the specific surface area BET of the porous carbon skeleton is obtained by fitting the T-Plot method.
  • Controlling the specific surface area of the porous carbon skeleton within an appropriate range can shorten the migration distance of lithium ions and improve the rate performance of the battery.
  • an appropriate specific surface area can also expose more lithium ion reaction active sites, increase the gram capacity of the electrode, and increase the energy density of the battery.
  • an appropriate range of specific surface area can also reduce side reactions between the electrolyte and the material and reduce the loss of irreversible capacity.
  • the pore size of the porous carbon framework is 0.5 nm to 100 nm.
  • the pore size of the porous carbon skeleton can be selected to be 0.5nm, 1nm, 2nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, or a value in a range consisting of any two of the above points.
  • the pore size of the porous carbon skeleton is well known in the art and can be measured using instruments and methods well known in the art.
  • a certain amount of the porous carbon skeleton prepared as above is taken as a sample, and the porous carbon skeleton sample is analyzed using a scanning electron microscope (SEM) to obtain a SEM image, and then the pore size is statistically drawn to form a normal distribution curve, and the median pore size on the normal distribution curve is taken as the pore size of the porous carbon skeleton.
  • SEM scanning electron microscope
  • the pore size of the porous carbon skeleton is within an appropriate range, which is conducive to the subsequent silicon particles entering the pores of the porous carbon skeleton, reducing the risk of silicon deposition on the surface of the porous carbon skeleton; and is conducive to the porous carbon skeleton particles approaching full deposition, thereby improving the material's electronic and ionic conductivity and improving the material's rate performance.
  • the porous carbon framework has a pore volume of 0.5 cm 3 /g to 8.5 cm 3 /g.
  • the pore volume of the porous carbon skeleton can be selected as 0.5 cm 3 /g, 1 cm 3 /g, 1.5 cm 3 /g, 2 cm 3 /g, 2.5 cm 3 /g, 3 cm 3 /g, 3.5 cm 3 /g, 4 cm 3 /g, 4.5 cm 3 /g, 5 cm 3 /g, 5.5 cm 3 /g, 6 cm 3 /g, 6.5 cm 3 /g, 7 cm 3 /g, 7.5 cm 3 /g, 8 cm 3 /g, 8.5 cm 3 /g or a value in a range consisting of any two of the above points.
  • the pore volume of the porous carbon skeleton is a well-known meaning in the art and can be measured using instruments and methods known in the art.
  • the test method can refer to GB/T 19587-2004, using the mesopore pore size distribution test BJH (Barret Joyner Halenda), using the gas adsorption and desorption method under the micro-mesopore model and selecting the adsorption branch data to obtain the pore volume of the material.
  • the pore volume of the porous carbon skeleton is within an appropriate range, which can not only ensure the stability of the skeleton structure but also meet the capacity of deposited silicon. Silicon particles are attached to the pores, and the silicon particles and the porous carbon skeleton can work synergistically to improve the capacity and conductivity of the silicon-carbon composite material and improve the battery's rate performance and energy density.
  • the volume distribution particle size Dv50 of the porous carbon framework is 0.3 ⁇ m-5 ⁇ m.
  • the volume distribution particle size Dv50 of the porous carbon skeleton can be selected as 0.3 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m or a value in the range formed by any two of the above points.
  • the volume distribution particle size Dv50 of the porous carbon skeleton is well known in the art and can be tested by methods known in the art.
  • the porous carbon skeleton sample is measured according to the GB/T 19077-2016/ISO 13320:2009 standard, and the testing equipment can be a laser particle size analyzer (such as Malvern Master Size 3000).
  • the volume distribution particle size Dv50 of the porous carbon skeleton meets the above range, the volume distribution particle size Dv50 of the silicon-carbon composite material is within an appropriate range, the structure of the silicon-carbon composite material is relatively stable, and the dynamic performance is relatively good, which is beneficial to improving the rate performance of the silicon-carbon composite material.
  • the silicon-carbon composite material has a carbon layer on at least a portion of its surface.
  • the carbon layer completely covers the outer surface of the porous carbon framework.
  • the carbon layer is coated on a portion of the outer surface of the porous carbon framework.
  • the carbon layer coated on the outer surface of the porous carbon skeleton is beneficial to improving the conductivity of the silicon-carbon composite material and improving the rate performance of the material. At the same time, the carbon layer can also enhance the stability between the silicon-carbon composite material and the electrolyte and improve the cycle performance of the battery.
  • the porous carbon framework includes one or more of graphite, soft carbon, and hard carbon.
  • the porous carbon framework includes hard carbon.
  • a method for preparing a silicon-carbon composite material comprising the following steps:
  • a porous carbon skeleton containing a doping element is prepared, wherein the doping element satisfies: a lithium ion diffusion coefficient of a single substance of the doping element at 25° C. is greater than a lithium ion diffusion coefficient of a single substance of silicon at 25° C.;
  • Silicon-based materials are deposited between the pores of the porous carbon skeleton to obtain a silicon-carbon composite material.
  • the silicon-carbon composite material obtained by the above preparation method has a stable porous skeleton structure, which has a strong supporting capacity, manifested as a high stress capacity, and has excellent mechanical properties and electrical conductivity; the pore structure in the porous carbon skeleton provides more space for setting silicon particles, which can be used for large-scale silicon storage; when the porous carbon skeleton is composited with silicon particles, the silicon The particles are not easy to agglomerate and can be evenly dispersed in the pores of the porous carbon skeleton; after the porous carbon skeleton is compounded with silicon particles, the conductivity of the silicon-carbon composite material can be improved, the rate performance of the material can be improved, and the volume effect of silicon in the process of lithium insertion and extraction can be alleviated, and the stress changes of silicon-based materials can be fully withstood, thereby ensuring the structural stability of the silicon-carbon composite material, improving the cycle stability and lithium storage capacity of the silicon-carbon composite material, and extending the cycle life of the battery; on
  • the preparation of the porous carbon skeleton includes solvothermal reaction, activation pore formation and high temperature carbonization.
  • Solvothermal reaction mixing a resin containing an unsaturated group and/or a sugar, a solvent, and an aqueous solution containing a doping element, and performing a solvent thermal reaction to obtain a first product;
  • Activation pore creation introducing water vapor into the first product to perform activation pore creation treatment to obtain the second product;
  • High temperature carbonization The second product is subjected to high temperature carbonization treatment to obtain a porous carbon skeleton.
  • the term "unsaturated group” refers to a group that can react with a hydroxyl group in a saccharide, including but not limited to an aldehyde group, a hydroxyl group, a carboxyl group or an acyl chloride group.
  • sucrose refers to polyhydroxy (two or more) aldehyde or ketone compounds.
  • the above-mentioned method for preparing the porous carbon skeleton can obtain a porous carbon skeleton, which is beneficial to the subsequent deposition of silicon.
  • the preparation of the porous carbon skeleton specifically includes solvent thermal reaction, activation pore formation and high temperature carbonization.
  • Solvothermal reaction a resin containing an unsaturated group, a sugar, a solvent, and an aqueous solution containing a doping element are mixed and subjected to a solvent thermal reaction to obtain a first product;
  • Activation pore creation introducing water vapor into the first product to perform activation pore creation treatment to obtain the second product;
  • High temperature carbonization The second product is subjected to high temperature carbonization treatment to obtain a porous carbon skeleton.
  • the resin containing unsaturated groups includes at least one of phenolic resin, furfural resin, and lignin-based activated carbon; and the sugar includes at least one of sucrose, glucose, and chitosan.
  • phenolic resin refers to a general term for a class of polymers prepared by addition condensation reaction of phenolic compounds (such as phenol, cresol, xylenol, resorcinol, tert-butylphenol, bisphenol A, etc.) and aldehyde compounds (such as formaldehyde, acetaldehyde, polyformaldehyde, furfural, etc.) in the presence of alkaline or acidic catalysts.
  • phenolic compounds such as phenol, cresol, xylenol, resorcinol, tert-butylphenol, bisphenol A, etc.
  • aldehyde compounds such as formaldehyde, acetaldehyde, polyformaldehyde, furfural, etc.
  • furfural resin refers to a furan resin polymer obtained by polycondensation or copolymerization using furfuryl alcohol or furfural as the main raw material.
  • the resin containing unsaturated groups includes phenolic resin; and the sugar includes sucrose.
  • the resin containing unsaturated groups includes furfural resin; and the sugar includes sucrose.
  • the furfural resin containing unsaturated groups; and the sugar includes glucose.
  • the resin containing unsaturated groups includes phenolic resin and furfural resin; and the sugar includes glucose.
  • the resin containing unsaturated groups includes phenolic resin; and the sugar includes sucrose and glucose.
  • the phenolic resin includes at least one of a phenol-formaldehyde resin, a resorcinol-formaldehyde resin, and a hydroquinone-formaldehyde resin.
  • the furfural resin comprises a phenol-furfural resin.
  • the lignin-based activated carbon comprises alkali lignin activated carbon.
  • the solvent comprises alcohol and water
  • the alcohol comprises at least one of ethanol, ethylene glycol, isopropanol, and n-butanol.
  • Alcohol and water are used as solvents for the resin containing unsaturated groups and sugars, respectively, to promote their dissolution in the solvent. At the same time, since alcohol and water are miscible, the dispersibility between the resin containing unsaturated groups and sugars is improved, thereby improving the electrochemical properties of the final silicon-carbon composite material.
  • Resins and sugars with unsaturated groups are used as raw materials, and cross-linking reactions are fully carried out through solvent thermal reaction. After high-temperature carbonization treatment, hard carbon materials with spherical or quasi-spherical structures are prepared. Because the reactants dispersed in the solvent have high reactivity under the solvent thermal critical conditions, during the solvent thermal reaction, The long-chain structure of the resin containing unsaturated groups is rearranged, the hydroxyl groups in the sugars react with the unsaturated groups in the resin, and the product slowly crystallizes to obtain spherical or quasi-spherical particles with a smooth surface.
  • the final spherical or quasi-spherical porous carbon skeleton has the advantage of a shorter ion diffusion path and a larger interlayer spacing, which is beneficial to the embedding/ejection and rapid migration of ions, and is beneficial to the formation of an unobstructed void structure in the negative electrode film layer, thereby increasing the solid-phase diffusion rate and liquid-phase transmission performance of lithium ions, improving the battery's rapid charging capability, and improving the battery's rate performance.
  • a resin containing an unsaturated group, a solvent, and an aqueous solution containing a doping element are mixed and subjected to a solvothermal reaction to obtain a first product, and the first product is carbonized to obtain a porous carbon skeleton.
  • sugars, solvents, and an aqueous solution containing doping elements are mixed and subjected to a solvothermal reaction to obtain a first product, and the first product is carbonized to obtain a porous carbon skeleton.
  • a non-spherical or non-quasi-spherical porous carbon skeleton can be obtained by solvent thermal reaction of a single resin or sugar.
  • the preparation method is simple and is conducive to industrial promotion.
  • the reaction temperature of the solvothermal reaction is 400°C-750°C.
  • the reaction time of the solvothermal reaction is 4 h to 10 h.
  • the reaction temperature of the solvothermal reaction can be selected as 400°C, 450°C, 500°C, 550°C, 600°C, 700°C, 750°C or a value in the range formed by any two of the above points
  • the reaction time can be selected as 4h, 5h, 6h, 7h, 8h, 9h, 10h or a value in the range formed by any two of the above points.
  • the structural parameters of the porous carbon skeleton such as the volume distribution particle size Dv50, specific surface area, pore size and pore volume, are within an appropriate range, which is beneficial to the subsequent silicon deposition process.
  • the reaction time and reaction temperature within an appropriate range, the size of the grains formed by the doped elements can also be controlled within an appropriate range, thereby improving the rate performance and cycle performance of the material.
  • the mass ratio of the resin containing unsaturated groups to the sugar is (2:8)-(9:1), and can be optionally (4:6)-(6:4).
  • the mass ratio of the resin containing unsaturated groups to the sugar can be Select 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 or a value in the range formed by any two of the above points.
  • the mass ratio of the resin containing unsaturated groups to the saccharide is (4:6)-(6:4). In some embodiments, the mass ratio of the resin containing unsaturated groups to the saccharide is 4:6, 5:5, 6:4 or a value in the range consisting of any two of the above points.
  • the molar ratio of the resin containing unsaturated groups to the sugar is controlled within a suitable range so that the porous carbon skeleton has a suitable specific surface area, pore size, pore volume and particle size, which is beneficial to the subsequent deposition of silicon or element doping process.
  • the treatment temperature for activation pore formation is 400°C-500°C.
  • the activation pore-forming treatment time is 4 h to 8 h.
  • the flow rate of water vapor is 0.5 g/min-1 g/min.
  • the pore size and pore volume in the porous carbon skeleton can be within appropriate ranges, thereby obtaining a porous carbon skeleton with excellent structural properties.
  • the carbonization treatment time is 400° C.-700° C.
  • the carbonization treatment temperature is 4 h-12 h.
  • vapor phase silicon deposition specifically includes:
  • a silicon-containing gas is used as a silicon source to perform vapor deposition on the porous carbon skeleton.
  • silicon deposition specifically includes:
  • a silicon-containing gas is used as a silicon source, and a vapor containing a doping element is used as a doping element source to perform vapor deposition on a porous carbon skeleton.
  • the silicon-containing gas includes one or more of monosilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane.
  • the flow rate of the silicon-containing gas is 0.5-30 L/min.
  • the flow rate of nitrogen or argon is 0.5-30 L/min.
  • the deposition temperature of the vapor deposited silicon is 500°C to 900°C.
  • the deposition time of vapor deposited silicon is 6-24 hours.
  • Silicon deposition is carried out under appropriate reaction conditions so that silicon is evenly dispersed in the porous carbon skeleton.
  • the holes in the frame can improve the structural properties of the silicon-carbon composite material and the rate performance of the material.
  • the preparation method further comprises preparing a carbon layer
  • Carbon coating treatment is performed on the surface of the silicon-carbon composite material.
  • the carbon coating process includes any one of chemical vapor deposition carbon coating, pyrolysis carbon coating, hydrothermal carbon coating, and polyelectrolyte modification carbon coating.
  • the surface of the silicon-carbon composite material is coated with a carbon layer, which is beneficial to improving the conductivity of the silicon-carbon composite material and improving the rate performance of the material.
  • the carbon layer can also enhance the stability between the silicon-carbon composite material and the electrolyte and improve the cycle performance of the battery.
  • a secondary battery is provided.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material for a battery known in the art.
  • the positive electrode active material may include the following materials: At least one: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 /3Co1 / 3Mn1/ 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ), LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.2Mn0.3O2 ) , LiNi0.5Co0.2M
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-carbon composite material in some embodiments.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the mass content of the silicon-carbon composite material is greater than or equal to 20%, based on the total mass of the negative electrode active material.
  • the mass content of the silicon-carbon composite material may be selected to be greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 8 ... Any one of 90%, 95% or more.
  • the silicon-carbon composite material is controlled within a suitable range so that its battery has excellent energy density and cycle performance.
  • the mass content of the silicon-carbon composite material is 25%-90%, based on the total mass of the negative electrode active material.
  • the mass content of the silicon-carbon composite material can be selected to be 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or a value in the range formed by any two of the above points.
  • both the energy density and cycle life of the battery can be taken into account, thereby comprehensively improving the electrochemical performance of the battery.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a conductive agent which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the compaction density of the negative electrode sheet is 1.2 g/cm 3 , 1.25 g/cm 3 , 1.3 g/cm 3 , 1.35 g/cm 3 , 1.4 g/cm 3 , 1.45 g/cm 3 , 1.5 g/cm 3 , 1.55 g/cm 3 , 1.6 g/cm 3 , 1.65 g/cm 3 , 1.7 g/cm 3 or a value in a range consisting of any two of the foregoing.
  • the battery has excellent energy density.
  • the negative electrode sheet can be prepared by the following method: dispersing the above components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components in a solvent (such as deionized water) to form a negative electrode slurry; The negative electrode slurry is coated on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the films are laminated, the materials of the layers may be the same or different without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • a secondary battery includes a positive electrode sheet, an electrolyte, a separator, and a negative electrode sheet in some embodiments.
  • the secondary battery comprises a lithium-ion battery.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the energy density of the secondary battery is 400-550 Wh/kg.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. However, they can also be arranged in any other manner. Further, the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are battery packs 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.
  • the lithium ion diffusion coefficient of Sn element at 25°C is 1 ⁇ 10 -13 cm 2 /S;
  • the lithium ion diffusion coefficient of Ge element at 25°C is 5 ⁇ 10 -14 cm 2 /S;
  • the lithium ion diffusion coefficient of the Sb element at 25°C is 7 ⁇ 10 -14 cm 2 /S;
  • the lithium ion diffusion coefficient of Bi element at 25°C is 4 ⁇ 10 -13 cm 2 /S;
  • the lithium ion diffusion coefficient of the Sr element at 25°C is 6 ⁇ 10 -13 cm 2 /S;
  • the lithium ion diffusion coefficient of element B at 25°C is 10 -16 cm 2 /S;
  • the lithium ion diffusion coefficient of silicon alone at 25°C is 2 ⁇ 10 -15 cm 2 /S.
  • the positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O 2 (NCM), the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 97%:1%:2% to obtain a positive electrode slurry; the slurry is then coated on a positive electrode collector, dried, cold pressed, and cut to obtain a positive electrode sheet.
  • Dissolve 30g of tin sulfate in 100g of water to obtain an aqueous solution add the aqueous solution to the mixed solution and stir for 30min, place the mixed solution in a reactor and react at 600°C for 8h to obtain a powder, then pass water vapor at 450°C for 6 hours to activate pore formation, wherein the flow rate of water vapor is 1g/min, place the treated product in a muffle furnace under nitrogen protection, and carbonize at 1200°C for 4h to obtain a spherical or Spherical porous carbon skeleton.
  • the silicon-carbon composite material is obtained by vapor deposition in a tube furnace with monosilane as a silicon source and nitrogen as a protective gas, wherein the flow rate of monosilane is 0.06 L/min, the flow rate of the protective gas is 4 L/min, the temperature of the vapor deposition is 450°C, and the time is 6 hours.
  • vapor deposition of the carbon source was carried out in a tubular furnace, wherein the flow rate of methane was 6 L/min, the flow rate of the protective gas was 15 L/min, the temperature of the vapor deposition was 900°C, the time was 6 h, and the gas source was turned off to cool down to obtain a silicon-carbon composite material.
  • Graphite and the silicon-carbon composite material prepared in the above step 1) are mixed in a mass ratio of 3:7 to obtain a negative electrode active material, wherein the mass fraction of the silicon-carbon composite material is 70% based on the total mass of the negative electrode active material.
  • the mixed negative electrode active material, conductive agent carbon black, carbon nanotubes (CNT), binder styrene butadiene rubber (SBR), and thickener sodium hydroxymethyl cellulose (CMC) are added into deionized water at a weight ratio of 94.5%:1%:0.375%:2.8%:1.325% and mixed evenly to obtain a negative electrode slurry; the slurry is coated on the negative electrode current collector, and the negative electrode sheet is obtained through drying, cold pressing, and slitting.
  • Polypropylene film is used as the isolation film.
  • the positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a battery cell, the battery cell is welded with a pole ear, and the battery cell is placed in an aluminum shell, and then the electrolyte is injected and sealed. After standing, cold pressing, forming, shaping, capacity testing and other processes, a lithium-ion secondary battery is obtained. Pool.
  • Example 2-3 The preparation parameters in Example 2-3 are basically the same as those in Example 1, but the preparation parameters of the silicon-carbon composite material are adjusted. The specific parameters are shown in Table 1.
  • Example 4-7 The preparation parameters in Examples 4-7 are substantially the same as those in Example 1, but the preparation parameters of the silicon-carbon composite material are adjusted, and the tin sulfate in Example 1 is replaced with germanium sulfate, antimony sulfate, bismuth sulfate, or tin sulfate+antimony sulfate.
  • the preparation parameters in Examples 8-13 are basically the same as those in Example 1, but the preparation parameters of the silicon-carbon composite material are adjusted, and the mass of tin sulfate in Examples 10 and 12 is adjusted to 10 g and 70 g, wherein the carbon source in Example 13 is sucrose, and the prepared porous carbon skeleton is a non-spherical or non-spherical structure, as follows:
  • the silicon-carbon composite material is obtained by vapor deposition in a tube furnace with monosilane as a silicon source and nitrogen as a protective gas, wherein the flow rate of monosilane is 0.06 L/min, the flow rate of the protective gas is 4 L/min, the temperature of the vapor deposition is 450°C, and the time is 6 hours.
  • vapor deposition of the carbon source was carried out in a tubular furnace, wherein the flow rate of methane was 6 L/min, the flow rate of the protective gas was 15 L/min, the temperature of the vapor deposition was 900°C, the time was 6 h, and the gas source was turned off to cool down to obtain a silicon-carbon composite material.
  • Comparative Example 1-2 The preparation parameters in Comparative Example 1-2 are basically the same as those in Example 1, but the silicon-carbon composite
  • the preparation parameters of the composite material are shown in Table 1.
  • the specific preparation method is as follows:
  • Comparative Example 1 The difference from Example 1 is that tin sulfate is replaced by boric acid.
  • Comparative Example 2 The difference from Example 1 is that tin sulfate is not added.
  • button cell Mix the single material formed by each doping element or silicon element, binder, and conductive agent in a ratio of 8:1:1 and add them to deionized water, mix and stir to obtain negative electrode slurry; apply it on one surface of the negative electrode current collector copper foil, dry, cold press, and cut to obtain negative electrode sheet, and use a punching die to obtain a small negative electrode disc with a certain area (153.86 mm2 is used in this application).
  • Use metal lithium sheet as the counter electrode, PP film as the isolation membrane, and the electrolyte formula is: ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, FEC are mixed into a solvent in a volume ratio of 1:1:1:1, and LiPF6 is used as the lithium salt dissolved in the above solvent to prepare a solution with a concentration of 1 mol/L, and assembled into a CR2032 button cell in an argon-protected glove box.
  • D Li is the lithium ion diffusion coefficient
  • S is the area of the small disc in the button battery prepared above
  • Ziq is the specific capacity of each single material
  • Ziq can be tested by the following steps: at 25°C, the button battery prepared above is charged with a constant current of 0.1C current until the battery voltage is less than 0.05V, and then allowed to stand for 120 minutes; then the button battery prepared above is discharged with a constant current of 0.1C current until the battery voltage is greater than 1.5V, and the specific capacity of the button battery at this time is measured and recorded as Ziq .
  • the grain size formed by the doping elements in the carbon-silicon composite material is tested by X-ray powder diffractometer (XRD).
  • XRD X-ray powder diffractometer
  • the model of X-ray powder diffractometer is X'pertPROo from the United States.
  • the detailed test process of grain size is as follows:
  • Instrument width Bs measurement Use the same material and grain size as the silicon-carbon composite material sample.
  • the standard sample is measured under the same experimental conditions as the silicon-carbon composite material sample, and the XRD spectrum of the standard sample is obtained from the spectrum;
  • the measurement is carried out with reference to EPA 6010D-2014 standard; specifically, ICP-OES (elemental analysis-inductively coupled plasma optical emission spectrometry) testing can be used.
  • the sample to be tested is first dissolved into liquid with a strong acid, and then the liquid is introduced into an ICP light source by atomization.
  • the gaseous atoms to be tested are further ionized and excited in a strong magnetic field, and then restored to the ground state from the excited state.
  • energy is released and recorded as different characteristic spectral lines, and quantitative analysis of doped elements, silicon-based materials and porous carbon skeletons is performed.
  • the batteries of the embodiments and comparative examples were charged and discharged for the first time at a current of 1C (i.e., the current value at which the rated capacity is completely discharged within 1 hour), specifically comprising: charging the battery at a constant current of 1C to a voltage of 4.3V, then charging at a constant voltage to a current of ⁇ 0.05C, standing for 5 minutes, and then discharging at a constant current of 0.33C to a voltage of 2.8V, and recording its actual capacity as C0.
  • a current of 1C i.e., the current value at which the rated capacity is completely discharged within 1 hour
  • the battery is charged with constant current at 2.0C0, 2.5C0, 3.0C0, 3.5C0, 4.0C0, 4.5C0, 5.0C0, 5.5C0, in sequence to a full battery charge cut-off voltage of 4.3V or a negative electrode cut-off potential of 0V (whichever is reached first).
  • a full battery charge cut-off voltage of 4.3V or a negative electrode cut-off potential of 0V (whichever is reached first).
  • the negative electrode potential corresponding to charging to 10%, 20%, 30%, ..., 80% SOC (State of Charge) at different charging rates is recorded, and the charging rate-negative electrode potential curve under different SOC states is drawn. After linear fitting, the charging rate corresponding to the negative electrode potential of 0V under different SOC states is obtained.
  • the charging rate is the charging window under the SOC state, which is recorded as C20 % SOC, C30 % SOC, C40 % SOC, C50 % SOC, C60% SOC, C70 % SOC, respectively.
  • SOC, C 80% SOC according to the formula (60/C 20% SOC+60/C 30% SOC+60/C 40% SOC+60/C 50% SOC+60/C 60% SOC+60/C 70% SOC+60/C 80% SOC) ⁇ 10%, the charging time T of the battery from 10% SOC to 80% SOC is calculated in min. The shorter the time, the better the fast charging performance of the battery.
  • the secondary battery prepared in each embodiment and comparative example is charged at a constant current of 0.5C to a charge cut-off voltage of 4.25V, then charged at a constant voltage to a current of ⁇ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage of 2V, left to stand for 5 minutes. This is a charge and discharge cycle.
  • the battery is tested for cyclic charge and discharge according to this method until the battery capacity decays to 80%. The number of cycles at this time is the cycle life of the battery at 25°C.
  • the batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Tables 1, 2 and 3 below.
  • the silicon-carbon composite materials in Examples 1-13 all include a porous carbon skeleton; a silicon-based material, at least part of the silicon-based material is arranged in the pores of the porous carbon skeleton; and the porous carbon skeleton includes at least one of the doping elements Sn, Ge, Sb, and Bi, and the lithium ion diffusion coefficient of the single substance of Sn, Ge, Sb or Bi at 25°C is greater than the lithium ion diffusion coefficient of the single substance of silicon at 25°C.
  • the silicon-carbon composite material of the present application is beneficial to reducing the fast charging time of the battery, extending the discharge time of the battery, improving the rate performance of the battery, increasing the number of cycles of the battery, and extending the cycle life of the battery.
  • the doping elements include one or two of Sn, Ge, Sb, and Bi, which are beneficial to increasing the number of battery cycles and 40% SOC discharge time, reducing the fast charging time of the battery, and improving the battery's cycle performance and rate performance.
  • the mass fraction of the doping element is controlled to be less than or equal to 7%, so that the battery has a lower fast charge time, a higher discharge time and a larger number of cycles, so that the battery has excellent rate performance and cycle performance. From the comparison of Examples 10-11 and Example 12, it can be seen that controlling the mass fraction of the doping element to 1%-3% is conducive to further improving the number of cycles and 40% SOC discharge time of the battery, reducing the fast charge time of the battery, and further improving the rate performance and cycle performance of the battery.
  • the porous carbon skeleton is spherical or quasi-spherical, which is beneficial to further increase the 40% SOC discharge time and reduce the fast charging time of the battery, improve the battery's rate performance, and extend the battery's cycle life.
  • Example 1-2 and Example 3 From the comparison between Example 1-2 and Example 3, it can be seen that controlling the volume distribution particle size Dv50 of the silicon-carbon composite material to be less than or equal to 5 ⁇ m is conducive to further improving the 40% SOC discharge time and reducing the fast charging time of the battery, improving the rate performance of the battery, improving the cycle life of the battery, and improving the cycle performance of the battery. From the comparison between Example 1 and Example 2-3, it can be seen that controlling the volume distribution particle size Dv50 of the silicon-carbon composite material to be 1 ⁇ m-3 ⁇ m is conducive to further improving the 40% SOC discharge time and reducing the fast charging time of the battery, improving the rate performance of the battery, and improving the dynamic performance of the battery.

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Abstract

一种硅碳复合材料及其制备方法、负极极片、二次电池和用电装置。硅碳复合材料包含多孔碳骨架、硅基材料以及掺杂元素，至少部分硅基材料设置于多孔碳骨架的孔隙中，至少部分掺杂元素分布在多孔碳骨架中；其中，掺杂元素满足：掺杂元素的单质在25℃下的锂离子扩散系数大于硅单质在25℃下的锂离子扩散系数。

Description

硅碳复合材料及其制备方法、负极极片、二次电池和用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种硅碳复合材料、及其制备方法、负极极片、二次电池和用电装置。
背景技术
近年来，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。
负极活性材料是二次电池的重要组分，为了进一步提高电池的能量密度，硅基负极活性材料被广泛研究，但是硅基材料因其自身的体积膨胀较大，会影响电池在使用过程中的电化学性能。
发明内容
本申请是鉴于上述课题而进行的，其目的在于提供一种硅碳复合材料，该硅碳复合材料具有优异的电子传输性能，有利于降低电池的快充时间，提高电池的循环圈数，能够提高电池的倍率性能和循环性能，综合改善电池的电化学性能。
为了达到上述目的，本申请的第一方面提供了一种硅碳复合材料，包括多孔碳骨架；硅基材料，至少部分设置于多孔碳骨架孔隙中；以及掺杂元素，至少部分掺杂元素分布在所述多孔碳骨架中；其中，所述掺杂元素满足：掺杂元素的单质在25℃下的锂离子扩散系数大于硅单质在25℃下的锂离子扩散系数。
一方面，硅碳复合材料具有稳定的多孔骨架结构，其支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性；其多孔碳骨架中的孔隙结构，可供设置硅颗粒的空间较多，可以用于 大量储硅；在多孔碳骨架与硅颗粒复合时，硅颗粒不易发生团聚，能够均匀分散于多孔碳骨架的孔中；在多孔碳骨架与硅颗粒复合后，可以提高硅碳复合材料的导电性，同时还可以缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅基材料的应力变化，保证硅碳复合材料的结构稳定性，提高硅碳复合材料的循环稳定性和储锂能力，延长电池的循环寿命；另一方面，在硅碳复合材料中掺杂锂离子扩散系数大于硅单质的元素，有利于降低锂离子在硅碳复合材料中的迁移势垒和迁移能，大大提高了硅碳复合材料的锂离子固相扩散系数，改善锂离子的迁移动力学，缩短电池的快充时间，提高材料的倍率性能。
在任意实施方式中，所述掺杂元素的单质的在25℃下的锂离子扩散系数大于10-14cm2/S，可选为大于10-14cm2/S且小于等于10- 13cm2/S；和/或，所述硅单质在25℃下的锂离子扩散系数小于10- 14cm2/S，可选为大于10-15cm2/S且小于10-14cm2/S。
在任意实施方式中，掺杂元素包括Sn、Ge、Sb、Bi、Sr中的至少一种。
上述掺杂元素的单质在25℃下的锂离子扩散系数均大于硅单质在25℃下的锂离子扩散系数，均可掺杂在硅碳复合材料中，从而降低锂离子在硅碳复合材料中的迁移势垒和迁移能，提高硅碳复合材料的锂离子固相扩散系数，改善锂离子的迁移动力学，提高电池的倍率性能，改善电池的动力学性能。
在任意实施方式中，至少部分掺杂元素在硅碳复合材料中形成晶粒；可选地，晶粒的尺寸小于等于10nm，更可选为3nm-7nm。
掺杂元素在硅碳复合材料以晶粒形式存在，相比于以无定形形式存在的掺杂元素，晶粒状态能够有效提高掺杂元素的导电子性和导离子性，进一步改善材料的导电性，改善电池的倍率性能，另外控制掺杂元素在硅碳复合材料中形成的晶粒尺寸在合适的范围内，有利于降低锂离子在硅碳复合材料中的迁移势垒和迁移能，大幅提高硅碳复合材料的锂离子固相扩散系数，提高锂离子迁移动力学， 改善电池的倍率性能。另外掺杂元素以小尺寸的晶粒形式存在，不会引起硅碳结构产生大的改变，不会导致材料的物相特性发生大的改变，能够很好地维持材料的结构稳定，不易在充放电过程中粉化，改善电池的循环性能，延长电池的循环寿命。
在任意实施方式中，基于硅碳复合材料的总质量计，掺杂元素的质量分数小于等于7％，可选为1％-3％。
控制掺杂元素的质量分数在合适的范围，既能够降低锂离子在硅碳复合材料中的迁移势垒和迁移能，大幅提高硅碳复合材料的锂离子固相扩散系数；又可以避免掺杂元素质量分数过高导致材料的内部结构发生改变，造成对电池循环性能的影响。具有合适质量含量范围的掺杂元素可兼顾电池倍率性能和循环性能，综合改善电池的性能。
在任意实施方式中，多孔碳骨架为球形或类球形。
球形或类球形的多孔碳骨架有利于使负极膜层形成通畅的空隙结构，提高锂离子固相扩散速度和液相传输性能，提升电池的快速充电能力，提高电池的倍率性能。
在任意实施方式中，基于所述硅碳复合材料的总质量计，硅基材料的质量分数大于等于30％，可选为35％-50％；和/或，基于所述硅碳复合材料的总质量计，多孔碳骨架的质量分数大于等于30％，可选为40％-60％。
硅基材料的质量含量在合适范围内，使得硅碳复合材料具有高的克容量，提高电池的能量密度，同时使得硅碳复合材料的体积膨胀受限于一定范围，使得硅碳复合材料具有一定的结构稳定性。
控制硅基材料的质量分数在合适的范围，可以兼顾电池的循环性能和能量密度。
多孔碳骨架的质量含量在合适范围内，使得硅碳复合材料具有足够的多孔碳骨架用于容纳硅基材料和掺杂元素，硅基复合材料具有高的克容量，同时多孔碳骨架的质量含量在合适范围内，可以提高硅碳复合材料的导电性，改善电池的动力学性能。
控制硅基材料的质量分数在合适的范围，可以兼顾电池的循环性能、倍率性能和能量密度。
在任意实施方式中，硅碳复合材料的体积分布粒径Dv50小于等于5μm，可选为1μm-3μm。
控制硅碳复合材料的体积分布粒径Dv50在合适范围内，有利于进一步降低硅碳复合材料中锂离子固相迁移路径，提高电池倍率性能。
在任意实施方式中，所述硅碳复合材料满足下述(1)-(4)中的至少一项：
(1)多孔碳骨架的比表面积为1000m2/g-2500m2/g；
(2)多孔碳骨架的孔径为0.5nm-100nm；
(3)多孔碳骨架的孔容为0.5cm3/g-8.5cm3/g；
(4)多孔碳骨架的体积分布粒径Dv50为0.3μm-5μm。
控制多孔碳骨架的比表面积、孔径、孔容和粒径在合适的范围内，便于硅基材料和掺杂元素的均匀分布，电池具有优异的循环性能和倍率性能，电池具有高的能量密度。
在任意实施方式中，硅碳复合材料的至少一部分表面上具有碳层。
包覆于硅碳复合材料上的碳层有利于提高硅碳复合材料的导电性，改善材料的倍率性能，同时碳层还可以提升硅碳复合材料与电解液之间的稳定性，改善电池的循环性能。
本申请第二方面提供一种硅碳复合材料的制备方法，包括如下步骤：
制备含有掺杂元素的多孔碳骨架，其中，所述掺杂元素满足：掺杂元素的单质在25℃下的锂离子扩散系数大于硅单质在25℃下的锂离子扩散系数；
在所述多孔碳骨架的孔隙中沉积硅基材料，得到所述硅碳复合材料。
一方面，上述制备方法中得到硅碳复合材料具有稳定的多孔骨 架结构，其支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性；其多孔碳骨架中的孔隙结构，可供设置硅颗粒的空间较多，可以用于大量储硅；在多孔碳骨架与硅颗粒复合时，硅颗粒不易发生团聚，能够均匀分散于多孔碳骨架的孔中，在多孔碳骨架与硅颗粒复合后，可以提高硅碳复合材料的导电性，同时缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅基材料的应力变化，保证硅碳复合材料的结构稳定性，提高硅碳复合材料的循环稳定性和储锂能力，延长电池的循环寿命；另一方面，在硅碳复合材料中掺杂锂离子扩散系数大于硅单质的元素，有利于降低锂离子在硅碳复合材料中的迁移势垒和迁移能，大大提高了硅碳复合材料的锂离子固相扩散系数，改善锂离子的迁移动力学，改善电池倍率性能。
在任意实施方式中，多孔碳骨架的制备包括溶剂热反应、活化造孔和高温碳化，
溶剂热反应：将含有不饱和基团的树脂和/或糖类、溶剂、含掺杂元素的水溶液混合，进行溶剂热反应，得到第一产物；
活化造孔：向第一产物中通入水蒸气进行活化造孔处理，得到第二产物；
高温碳化：将第二产物进行高温碳化处理，得到多孔碳骨架。
上述制备方法可得到多孔碳骨架，且制备方法简单，易于工业化应用。
在任意实施方式中，溶剂热反应的反应温度为400℃-750℃；和/或，所述溶剂热反应的反应时间为4h-10h。
控制反应时间和/或反应温度在合适范围内，可以控制多孔碳骨架的体积分布粒径Dv50、比表面积、孔径和孔容等结构参数在合适范围内，利于后续的硅基材料的沉积。
在任意实施方式中，含有不饱和基团的树脂与糖类的质量比为(2:8)-(9:1)，可选为(4:6)-(6:4)。
控制含有不饱和基团的树脂与糖类的摩尔比在合适的范围内， 以使多孔碳骨架具有合适的比表面积、孔径、孔容和粒径，利于后续的硅的沉积。
在任意实施方式中，含有不饱和基团的树脂包括酚醛树脂、糠醛树脂、木质素基活性炭中的至少一种；和/或糖类包括蔗糖、葡萄糖、壳聚糖中的至少一种。
在任意实施方式中，活化造孔的处理温度为400℃-500℃；和/或，所述活化造孔的处理时间为4h-8h；和/或，所述水蒸气的流速为0.5g/min-1g/min。
在任意实施方式中，气相沉积硅的沉积温度为500℃-900℃；和/或，所述气相沉积硅的沉积时间为6h-24h。
控制气相沉积硅的沉积时间和沉积温度在合适范围内，使得硅均匀分散于多孔碳骨架的孔隙中，硅碳复合材料具有优异的结构参数。
在任意实施方式中，制备方法还包括制备碳层，
制备碳层：在硅碳复合材料表面进行碳包覆处理。
硅碳复合材料表面包覆碳层有利于提高硅碳复合材料的导电性，改善材料的倍率性能，同时碳层还可以提升硅碳复合材料与电解液之间的稳定性，改善电池的循环性能。。
本申请第三方面提供一种负极极片，负极极片包括负极集流体和设置在负极集流体表面的负极膜层，负极膜层包括负极活性材料，负极活性材料包括本申请第一方面所述的硅碳复合材料或根据本申请第二方面所述的制备方法制备得到的硅碳复合材料。
本申请第四方面提供一种二次电池，包括本申请第三方面的负极极片。
本申请的第五方面提供一种用电装置，包括本申请第四方面的二次电池。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
图7是本申请的实施例1所示的多孔碳骨架的扫描电镜图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳
体；52电极组件；53顶盖组件
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的硅碳复合材料、及其制备方法、负极极片、二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示 本申请中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
硅碳复合材料是常用的活性材料之一。目前，硅碳复合材料的制备方面主要是将硅直接与碳材料进行混合，这些硅碳材料对硅的含量需要有一定限制，当硅含量过高时，膨胀仍然较大，会导致电极结构破坏，恶化电池的循环寿命，另外，硅碳复合材料本身的导电性较差，严重限制了其进一步应用。因此，需要设计一种新的硅碳复合材料，以满足新一代电化学的需求。
[硅碳复合材料]
基于此，本申请提出了硅碳复合材料，包括多孔碳骨架；硅基材料，至少部分硅基材料设置于多孔碳骨架孔隙中；以及掺杂元素，至少部分掺杂元素分布在多孔碳骨架中；其中，所述掺杂元素满足：掺杂元素的单质在25℃下的锂离子扩散系数大于硅单质在25℃下的锂离子扩散系数。
一方面，硅碳复合材料具有稳定的多孔骨架结构，其支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性；其多孔碳骨架中的孔隙结构，可供沉积硅颗粒的空间较多，可以用于大量储硅；硅沉积于多孔碳骨架时，硅颗粒不易发生团聚，能够均匀分散于多孔碳骨架的孔中；在多孔碳骨架与硅颗粒复合后，可以提高硅碳复合材料的导电性，改善材料的倍率性能，同时还可以缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅颗粒的应力变化，保证硅碳复合材料的结构稳定性；另一方面，在硅碳复合材料中掺杂锂离子扩散系数大于硅单质的元素，有利于降低锂离子在硅碳复合材料中的迁移势垒和迁移能，大大提高了硅碳复合材料的锂离子固相扩散系数，改善锂离子的迁移动力学，提高材料的倍率性能。
综上所述，本申请的硅碳复合材料能够降低电池的快充时间，提高电池的倍率性能，提高电池的循环圈数，延长电池的循环寿命，综合改善电池的性能。
在本申请中，术语“硅碳复合材料”是指基于硅碳复合材料的总质量计，硅元素和碳元素的质量含量均大于10％的材料。
在本申请中，术语“多孔碳骨架”是指骨架的主要成分为碳，且骨架中含有多个孔。
硅碳复合材料的多孔碳骨架结构可以采用本领域已知的设备和方法进行测试。例如，可以通过使用扫描电子显微镜(例如ZEISS Sigma 300)进行测试。作为示例，可以按照如下步骤操作：首先将包含所述硅碳复合材料的负极极片裁成一定尺寸的待测样品(例如 6mm×6mm)，用两片导电导热的薄片(如铜箔)将待测样品夹住，将待测样品与薄片之间用胶(如双面胶)粘住固定，用一定质量(如400g左右)平整铁块压一定时间(如1h)，使待测样品与铜箔间缝隙越小越好，然后用剪刀将边缘剪齐，粘在具有导电胶的样品台上，样品略突出样品台边缘即可。然后将样品台装进样品架上锁好固定，打开氩离子截面抛光仪(例如IB-19500CP)电源并抽真空，设置氩气流量(例如0.15MPa)和电压(例如8KV)以及抛光时间(例如2小时)，调整样品台为摇摆模式开始抛光，抛光结束后，使用扫描电子显微镜(例如ZEISS Sigma 300)得到待测样品的离子抛光断面形貌(CP)图片。
在本申请中，“锂离子扩散系数”指的是用于表征材料动力学行为的重要参数，表现在材料的扩散系数越大，电池的大电流放电能力越好，材料的功率密度越高，高倍率性能越好。
在本申请中的“掺杂元素”的种类是指：由该元素形成的单质的锂离子扩散系数大于硅元素的单质的锂离子扩散系数的一类元素。
材料的锂离子扩散系数具有本领域公知的含义，可以采用本领域已知的方法进行测试。作为示例，本申请中采用恒流间歇滴定法(GITT)对由掺杂元素构成的单质材料进行锂离子扩散系数的测定。
在一些实施方式中，掺杂元素的单质在25℃下的锂离子扩散系数大于10-14cm2/S，可选为大于10-14cm2/S且小于等于10-13cm2/S。
在一些实施方式中，硅单质在25℃下的锂离子扩散系数小于10- 14cm2/S，可选为大于10-15cm2/S且小于10-14cm2/S。
在一些实施方式中，掺杂元素的单质在25℃下的锂离子扩散系数可选为2×10-14cm2/S、3×10-14cm2/S、4×10-14cm2/S、5×10- 14cm2/S、6×10-14cm2/S、7×10-14cm2/S、8×10-14cm2/S、9×10- 14cm2/S、10-13cm2/S中的任意值或其中任意两值组成的范围。
在一些实施方式中，硅单质在25℃下的锂离子扩散系数可选为2×10-15cm2/S、3×10-15cm2/S、4×10-15cm2/S、5×10-15cm2/S、6×10- 15cm2/S、7×10-15cm2/S、8×10-15cm2/S、9×10-15cm2/S中的任意值或 其中任意两值组成的范围。
在一些实施方式中，掺杂元素包括Sn、Ge、Sb、Bi、Sr中的至少一种。
在一些实施方式中，掺杂元素包括Sn、Ge、Sb、Bi、Sr中的至少两种。例如，掺杂元素可以同时包括Sn和Ge，Sn和Sb，Sn和Bi，Sn和Sr，Ge和Sb，Ge和Bi，Ge和Sr，Sb和Bi，Sb和Sr，或者Bi和Sr。
上述掺杂元素具有优异的锂离子扩散系数，能够有效改善硅碳复合材料的导电性能，提高电池的倍率性能。且原材料丰富易得，适用于各种电池中，具有优异的应用前景。
在一些实施方式中，至少部分掺杂元素在硅碳复合材料中形成晶粒。
相比于以无定形形式存在的掺杂元素，以晶粒形式存在的掺杂元素，其导电子性和导离子性更优异，能够有效改善硅碳复合材料的导电性，改善电池的倍率性能。
在一些实施方式中，晶粒的尺寸小于等于10nm。
晶粒的尺寸为本领域公知的含义，可以采用本领域已知的方法测试。作为示例，采用X射线粉末衍射仪(XRD)测试掺杂元素在碳硅元素在硅碳复合材料中形成的晶粒尺寸，X射线粉末衍射仪的型号为美国的X'pertPROo。晶粒尺寸的详细测试过程如下：a、硅碳复合材料样品实测宽度Bm的测量。设置仪器扫描速率为2度/分钟，得到待测样品的XRD谱图，用JADE软件扣除CuKa2背底，得到各个衍射峰的Bm；b、仪器宽化Bs测量。用与硅碳复合材料样品同物质、晶粒度在的标样，在与硅碳复合材料样品相同实验条件下，测定标样的XRD图谱，由图谱得到Bs；c、半高宽B的计算。B＝Bm-Bs；(注：如果计算出B的单位是角度，需转换成弧度)，d、晶粒尺寸的计算；使用谢乐公式D＝Kλ/Bcosθ，其中K取0.89，θ为衍射角，λ＝0.154056nm，代入B，即可得到单个衍射峰所代表的晶 面法向的晶粒厚度，取多个衍射峰分别计算取平均值后即得晶粒尺寸。
在一些实施方式中，晶粒的尺寸可选为小于等于0.1nm、小于等于0.5nm、小于等于1nm、小于等于1.5nm、小于等于2nm、小于等于2.5nm、小于等于3nm、小于等于3.5nm、小于等于4nm、小于等于4.5nm、小于等于5nm、小于等于5.5nm、小于等于6nm、小于等于6.5nm、小于等于7nm、小于等于7.5nm、小于等于8nm、小于等于8.5nm、小于等于9nm、小于等于9.5nm、小于等于10nm中的任意一种。
控制掺杂元素在硅碳复合材料中形成的晶粒尺寸在合适的范围内，有利于降低锂离子在硅碳复合材料中的迁移势垒和迁移能，大幅提高硅碳复合材料的锂离子固相扩散系数，提高锂离子迁移动力学，改善电池的倍率性能。另外掺杂元素以小尺寸的晶粒形式存在，不会引起硅碳结构产生大的改变，不会导致材料的物相特性发生大的改变，能够很好地维持材料的结构稳定，不易在充放电过程中粉化，改善电池的循环性能，延长电池的循环寿命。
在一些实施方式中，晶粒的尺寸可选为3nm-7nm。
在一些实施方式中，晶粒的尺寸可选为3nm、3.5nm、4nm、4.5nm、5nm、5.5nm、6nm、6.5nm、7nm或由上述任意两点构成的范围中的数值。
控制晶粒的尺寸在合适的范围内，有利于进一步提升电池的循环圈数和放电时间、降低其电池的快充时间，进一步改善电池的倍率性能和循环性能。
在一些实施方式中，掺杂元素的质量分数小于等于7％，基于硅碳复合材料的总质量计。
掺杂元素的质量含量可以采用本领域已知的方法和设备测试，例如可参考EPA 6010D-2014标准进行测定；具体地，可以采用ICP-OES(元素分析-电感耦合等离子体发射光谱法)测试，先将待测样品用强酸溶解为液体，随后通过雾化的方式将液体引入ICP光源， 进一步待测气态原子在强磁场中发生电离和激发后，由激发态恢复到基态；在上述过程中释放能量并被记录为不同的特征谱线，进行元素定量分析。
在一些实施方式中，基于硅碳复合材料的总质量计，掺杂元素的质量分数可选为小于等于1％、小于等于1.5％、小于等于2％、小于等于2.5％、小于等于3％、小于等于3.5％、小于等于4％、小于等于4.5％、小于等于5％、小于等于5.5％、小于等于6％、小于等于6.5％、小于等于7％中的任意一种。
掺杂元素具有合适的质量含量，可以提高硅碳复合材料的电导率，提高材料的锂离子传输能力，改善电池的循环性能和倍率性能，同时合适质量含量的掺杂元素并不会使材料内部结构和晶相发生改变，改善电池的循环性能。
在一些实施方式中，掺杂元素的质量分数为1％-3％，基于硅碳复合材料的总质量计。
在一些实施方式中，基于硅碳复合材料的总质量计，掺杂元素的质量分数可选为1％、1.5％、2％、2.5％、3％或由上述任意两点构成的范围中的数值。
控制掺杂元素的质量含量在合适范围内，有利于进一步提升电池的循环圈数和放电时间、降低电池的快充时间，进一步改善电池的倍率性能和循环性能。
在一些实施方式中，多孔碳骨架为球形或类球形。
在本申请中，术语“球形”是指球心到球面任意一点的距离相等。
在本申请中，术语“类球形”是指球心到球面最远一点的距离为R1，球心到球面最近一点的距离为R2，R1与R2差值的绝对值除以R1与R2的平均值小于1％。
球形或类球形的多孔碳骨架有利于使负极膜层形成通畅的空隙结构，提高锂离子固相扩散速度和液相传输性能，提升电池的快速充电能力，提高电池的倍率性能。
在一些实施方式中，硅基材料的质量分数大于等于30％，基于硅碳复合材料的总质量计。
硅基材料的质量含量可以采用本领域已知的方法和设备测试，例如可参考EPA 6010D-2014标准进行测定；具体地，可以采用ICP-OES(元素分析-电感耦合等离子体发射光谱法)测试，先将待测样品用强酸溶解为液体，随后通过雾化的方式将液体引入ICP光源，进一步待测气态原子在强磁场中发生电离和激发后，由激发态恢复到基态；在上述过程中释放能量并被记录为不同的特征谱线，进行元素定量分析。
在一些实施方式中，基于硅碳复合材料的总质量计，硅基材料的质量分数可选为大于等于30％、大于等于40％、大于等于45％、大于等于50％中的任意一种。
硅基材料的质量含量在合适范围内，使得硅碳复合材料具有高的克容量，提高电池的能量密度，同时使得硅碳复合材料的体积膨胀受限于一定范围，使得硅碳复合材料具有一定的的结构稳定性，电池具有高的能量密度和优异的循环性能。
在一些实施方式中，硅基材料的质量分数为35％-50％，基于硅碳复合材料的总质量计。
在一些实施方式中，基于硅基复合材料的总质量计，硅基材料的质量分数可选为35％、36％、37％、38％、39％、40％、41％、42％、43％、44％、45％、46％、47％、48％、49％、50％、或由上述任意两点构成的范围中的数值。
控制硅基材料的质量分数在合适范围内，可以兼顾电池的能量密度和循环寿命，综合改善电池的性能
在一些实施方式中，多孔碳骨架的质量分数大于等于30％，基于硅碳复合材料的总质量计。
在一些实施方式中，基于硅碳复合材料的总质量计，多孔碳骨架的质量分数可选为大于等于30％、大于等于40％、大于等于45％、大于等于50％中的任意一种。
多孔碳骨架的质量含量可以采用本领域已知的方法和设备测试，例如可参考EPA 6010D-2014标准进行测定；具体地，可以采用ICP-OES(元素分析-电感耦合等离子体发射光谱法)测试，先将待测样品用强酸溶解为液体，随后通过雾化的方式将液体引入ICP光源，进一步待测气态原子在强磁场中发生电离和激发后，由激发态恢复到基态；在上述过程中释放能量并被记录为不同的特征谱线，进行元素定量分析。
多孔碳骨架的质量含量在合适范围内，使得硅碳复合材料具有足够的多孔碳骨架用于容纳硅基材料和掺杂元素，硅基复合材料具有高的克容量，同时多孔碳骨架的质量含量在合适范围内，可以提高硅碳复合材料的导电性，改善电池的动力学性能。
在一些实施方式中，基于硅碳复合材料的总质量计，多孔碳骨架的质量分数可选为40％、41％、42％、43％、44％、45％、46％、47％、48％、49％、50％、51％、52％、53％、54％、55％、56％、57％、58％、59％、60％、或由上述任意两点构成的范围中的数值。。
控制多孔碳骨架的质量分数在合适的范围，可以兼顾电池的循环性能、倍率性能和能量密度。
在一些实施方式中，硅碳复合材料的体积分布粒径Dv50小于等于5μm。
在一些实施方式中，硅碳复合材料的体积分布粒径Dv50可选为小于等于1μm、小于等于1.5μm、小于等于2μm、小于等于2.5μm、小于等于3μm、小于等于3.5μm、小于等于4μm、小于等于4.5μm、小于等于5μm中的任意一种。
硅碳复合材料的体积分布粒径Dv50为本领域公知的含义，可以采用本领域已知的方法测试。作为示例，例如按照GB/T 19077-2016/ISO 13320:2009标准对硅碳复合材料样品进行测定，测试设备可以采用激光粒度分析仪(如Malvern Master Size 3000)。
控制硅碳复合材料的体积分布粒径Dv50小于等于5μm，以使硅碳复合材料具有较短的锂离子固相迁移路径，进一步提高电池的倍 率性能，改善电池的动力学性能。
在一些实施方式中，硅碳复合材料的体积分布粒径Dv50为1μm-3μm。
在一些实施方式中，硅碳复合材料的体积分布粒径Dv50可选为1μm、1.2μm、1.4μm、1.5μm、1.6μm、1.8μm、2μm、2.2μm、2.4μm、2.5μm、2.6μm、2.8μm、3μm、或由上述任意两点构成的范围中的数值。
控制硅碳复合材料的体积分布粒径Dv50为1μm-3μm，有利于进一步提升电池的放电时间和降低其电池的快充时间，提高电池的倍率性能，改善电池的动力学性能。
在一些实施方式中，多孔碳骨架的比表面积为1000m2/g-2500m2/g。
在一些实施方式中，多孔碳骨架的比表面积可选为1000m2/g、1100m2/g、1200m2/g、1300m2/g、1400m2/g、1500m2/g、1600m2/g、1700m2/g、1800m2/g、1900m2/g、2000m2/g、2100m2/g、2200m2/g、2300m2/g、2400m2/g、2500m2/g或由上述任意两点构成的范围中的数值。
多孔碳骨架的比表面积为本领域公知的含义，可以采用本领域已知的方法测试。作为示例，使用美国麦克公司的3Flex比表面积分析仪测试多孔碳骨架的比表面积。通过T-Plot法拟合得到多孔骨碳架的比表面积BET。
控制多孔碳骨架的比表面积在合适范围内，缩短锂离子迁移距离，改善电池的倍率性能，另外合适的比表面积也可以暴露出多的锂离子反应活性位点，提高极片的克容量，提高电池的能量密度，同时合适范围的比表面积，还能减少电解液与材料之间的副反应，减少不可逆容量的损失。
在一些实施方式中，多孔碳骨架的孔径为0.5nm-100nm。
在一些实施方式中，多孔碳骨架的孔径可选为0.5nm、1nm、2nm、5nm、10nm、15nm、20nm、25nm、30nm、35nm、40nm、 45nm、50nm、55nm、60nm、65nm、70nm、75nm、80nm、85nm、90nm、95nm、100nm或由上述任意两点构成的范围中的数值。
多孔碳骨架的孔径为本领域公知的含义，可以采用本领域公知的仪器和方法测定。作为示例，取一定量上述制备的多孔碳骨架作为样品，采用扫描电子显微镜(Scanning Electron Microscope，简称SEM)分析多孔碳骨架样品，得到SEM图片，然后统计孔尺寸画正态分布曲线，取正态分布曲线上的中值孔径即为多孔碳骨架的孔径。
多孔碳骨架的孔径在合适范围内，有利于后续硅颗粒进入多孔碳骨架的孔中，降低硅沉积于多孔碳骨架表面的风险；且有利于多孔碳骨架颗粒趋近于沉积饱满，提高材料的导电子性和导离子性，改善材料的倍率性能。
在一些实施方式中，多孔碳骨架的孔容为0.5cm3/g-8.5cm3/g。
在一些实施方式中，多孔碳骨架的孔容可选为0.5cm3/g、1cm3/g、1.5cm3/g、2cm3/g、2.5cm3/g、3cm3/g、3.5cm3/g、4cm3/g、4.5cm3/g、5cm3/g、5.5cm3/g、6cm3/g、6.5cm3/g、7cm3/g、7.5cm3/g、8cm3/g、8.5cm3/g或由上述任意两点构成的范围中的数值。
多孔碳骨架的孔容为本领域公知的含义，可以采用本领域公知的仪器和方法测定。例如，测试方法可以参考GB/T 19587-2004，采用介孔孔径分布测试BJH(Barret joyner Halenda)，在微-介孔模型下采用气体吸脱附方法测试并选取吸附支数据，得到材料的孔容积。
多孔碳骨架的孔容在合适范围内，既能够保证骨架结构的稳定性，又能够满足沉积硅的容量，硅颗粒附着于孔中，硅颗粒和多孔碳骨架可以协同发挥作用，从而提高硅碳复合材料的容量和导电性，改善电池的倍率性能和能量密度。
在一些实施方式中，多孔碳骨架的体积分布粒径Dv50为0.3μm-5μm。
在一些实施方式中，多孔碳骨架的体积分布粒径Dv50可选为0.3μm、0.5μm、1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm或由上述任意两点构成的范围中的数值。
多孔碳骨架的体积分布粒径Dv50为本领域公知的含义，可以采用本领域已知的方法测试。例如按照GB/T 19077-2016/ISO 13320:2009标准对多孔碳骨架样品进行测定，测试设备可以采用激光粒度分析仪(如Malvern Master Size 3000)。
多孔碳骨架的体积分布粒径Dv50满足上述范围时，使得硅碳复合材料的体积分布粒径Dv50在合适范围内，硅碳复合材料的结构相对稳定，动力学性能相对较好，有利于提高硅碳复合材料的倍率性能。
在一些实施方式中，硅碳复合材料至少一部分表面上具有碳层。
在一些实施方式中，碳层完全包覆于多孔碳骨架外表面。
在一些实施方式中，碳层包覆于部分多孔碳骨架外表面。
包覆于多孔碳骨架外表面上的碳层有利于提高硅碳复合材料的导电性，改善材料的倍率性能，同时碳层还可以提升硅碳复合材料与电解液之间的稳定性，改善电池的循环性能。
在一些实施方式中，多孔碳骨架包括石墨、软碳和硬碳中的一种或几种。
在一些实施方式中，多孔碳骨架包括硬碳。
上述材料在制备成多孔结构时，有利于硅颗粒设置于多孔结构的孔中；且其结构稳定性相对较高。
本申请一些实施方式中提供一种硅碳复合材料的制备方法，包括如下步骤，
制备含有掺杂元素的多孔碳骨架，其中，掺杂元素满足：掺杂元素的单质在25℃下的锂离子扩散系数大于硅单质在25℃下的锂离子扩散系数；
在多孔碳骨架的孔隙间沉积硅基材料，得到硅碳复合材料。
一方面，上述制备方法得到的硅碳复合材料具有稳定的多孔骨架结构，其支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性；其多孔碳骨架中的孔隙结构，可供设置硅颗粒的空间较多，可以用于大量储硅；在多孔碳骨架与硅颗粒复合时，硅 颗粒不易发生团聚，能够均匀分散于多孔碳骨架的孔中；在多孔碳骨架与硅颗粒复合后，可以提高硅碳复合材料的导电性，改善材料的倍率性能，同时还可以缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅基材料的应力变化，保证硅碳复合材料的结构稳定性，提高硅碳复合材料的循环稳定性和储锂能力，延长电池的循环寿命；另一方面，在硅碳复合材料中掺杂锂离子扩散系数大于硅单质的元素，有利于降低锂离子在硅碳复合材料中的迁移势垒和迁移能，大大提高了硅碳复合材料的锂离子固相扩散系数，改善锂离子的迁移动力学，改善电池倍率性能。
在一些实施方式中，多孔碳骨架的制备包括溶剂热反应、活化造孔和高温碳化，
溶剂热反应：将含有不饱和基团的树脂和/或糖类、溶剂、含掺杂元素的水溶液混合，进行溶剂热反应，得到第一产物；
活化造孔：向第一产物中通入水蒸气进行活化造孔处理，得到第二产物；
高温碳化：将第二产物进行高温碳化处理，得到多孔碳骨架。
在本申请中，术语“不饱和基团”是指可以与糖类中的羟基发生反应的基团，包括但不限于醛基、羟基、羧基或酰氯基团。
在本申请中，术语“糖类”是指多羟基(2个或2个以上)的醛类或酮类化合物。
上述多孔碳骨架的制备方法可得到多孔碳骨架，有利于后续的进行硅的沉积。
在一些实施方式中，制备多孔碳骨架具体包括溶剂热反应、活化造孔和高温碳化，
溶剂热反应：将含有不饱和基团的树脂、糖类、溶剂、含掺杂元素的水溶液混合，进行溶剂热反应，得到第一产物；
活化造孔：向第一产物中通入水蒸气进行活化造孔处理，得到第二产物；
高温碳化：将第二产物进行高温碳化处理，得到多孔碳骨架。
在一些实施方式中，含有不饱和基团的树脂包括酚醛树脂、糠醛树脂、木质素基活性炭中的至少一种；糖类包括蔗糖、葡萄糖、壳聚糖中的至少一种。
在本申请中，术语“酚醛树脂”是指由酚类化合物(如苯酚、甲酚、二甲酚、间苯二酚、叔丁酚、双酚A等)与醛类化合物(如甲醛、乙醛、多聚甲醛、糠醛等)在碱性或酸性催化剂作用下，经加成缩聚反应制得的一类聚合物的统称。
在本申请中，术语“糠醛树脂”是指以糠醇或糠醛为主要原料通过缩聚或共聚得到的一种呋喃树脂聚合物。
在一些实施方式中，含有不饱和基团的树脂包括酚醛树脂；糖类包括蔗糖。在一些实施方式中，含有不饱和基团的树脂包括糠醛树脂；糖类包括蔗糖。在一些实施方式中，含有不饱和基团的糠醛树脂；糖类包括葡萄糖。在一些实施方式中，含有不饱和基团的树脂包括酚醛树脂和糠醛树脂；糖类包括葡萄糖。在一些实施方式中，含有不饱和基团的树脂包括酚醛树脂；糖类包括蔗糖和葡萄糖。
在一些实施方式中，酚醛树脂包括苯酚-甲醛树脂、间苯二酚-甲醛树脂、对苯二酚-甲醛树脂中的至少一种。
在一些实施方式中，糠醛树脂包括苯酚-糠醛树脂。
在一些实施方式中，木质素基活性炭包括碱木质素活性炭。
在一些实施方式中，溶剂包括醇和水，醇包括乙醇、乙二醇、异丙醇和正丁醇中的至少一种。
醇和水分别作为含有不饱和基团的树脂和糖类的溶剂，促进二者在溶剂中溶解，同时由于醇和水互溶，进而提高含有不饱和基团的树脂和糖类之间的分散性，进而提高最终得到的硅碳复合材料的电化学性能。
将自身都带有不饱和基团的树脂和糖类作为原料，通过溶剂热反应，使其充分发生交联反应，后经高温碳化处理的方式，制备出具有球形或类球形结构的硬炭材料。因为分散在溶剂中的反应物在溶剂热临界条件下具有较高的反应活性，所以在溶剂热反应过程中， 含有不饱和基团的树脂的长链结构发生重排，糖类中的羟基和树脂中的不饱和基团发生反应，产物缓慢结晶，得到表面光滑的球形或类球形颗粒，最终得到的球形或类球形多孔碳骨架具有离子扩散路径较短的优势，同时具有较大的层间距，有利于离子的嵌入/脱出和快速迁移，有利于使负极膜层形成通畅的空隙结构，提高锂离子固相扩散速度和液相传输性能，提升电池的快速充电能力，提高电池的倍率性能。
在一些实施方式中，将含有不饱和基团的树脂、溶剂、含掺杂元素的水溶液混合，进行溶剂热反应，得到第一产物，将第一产物进行碳化处理，得到多孔碳骨架。
在一些实施方式中，将糖类、溶剂、含掺杂元素的水溶液混合，进行溶剂热反应，得到第一产物，将第一产物进行碳化处理，得到多孔碳骨架。
单独的树脂或糖类进行溶剂热反应，可以得到非球形或非类球形的多孔碳骨架，制备方法简单，利于工业化推广。
在一些实施方式中，溶剂热反应的反应温度为400℃-750℃。
在一些实施方式中，溶剂热反应的反应时间为4h-10h。
在一些实施方式中，溶剂热反应的反应温度可选为400℃、450℃、500℃、550℃、600℃、700℃、750℃或由上述任意两点构成的范围中的数值，反应时间可选为4h、5h、6h、7h、8h、9h、10h或由上述任意两点构成的范围中的数值。
控制溶剂热反应中的反应温度和反应时间，使得多孔碳骨架的体积分布粒径Dv50、比表面积、孔径和孔容等结构参数在合适范围内，利于后续的沉积硅过程，另外控制反应时间和反应温度在合适范围内，还可以控制掺杂元素的形成的晶粒的尺寸在合适范围内，改善材料的倍率性能和循环性能。
在一些实施方式中，含有不饱和基团的树脂与糖类的质量比为(2:8)-(9:1)，可选为(4:6)-(6:4)。
在一些实施方式中，含有不饱和基团的树脂与糖类的质量比可 选为2:8、3:7、4:6、5:5、6:4、7:3、8:2、9:1或由上述任意两点构成的范围中的数值。
在一些实施方式中，含有不饱和基团的树脂与糖类的质量比为(4:6)-(6:4)。在一些实施方式中，含有不饱和基团的树脂与糖类的质量比为4:6、5:5、6:4或由上述任意两点构成的范围中的数值。
控制含有不饱和基团的树脂与糖类的摩尔比在合适的范围内，以使多孔碳骨架具有合适的比表面积、孔径、孔容和粒径，利于后续的沉积硅或元素掺杂过程。
在一些实施方式中，活化造孔的处理温度为400℃-500℃。
在一些实施方式中，活化造孔的处理时间为4h-8h。
在一些实施方式中，水蒸气的流速为0.5g/min-1g/min。
控制活化凿空的处理温度、处理时间、水蒸气的流速在合适范围内，可以使得多孔碳骨架中的孔径、孔容在合适范围内，得到具有优异结构性能的多孔碳骨架。
在一些实施方式中，碳化处理的时间为400℃-700℃，碳化处理的温度为4h-12h。
在一些实施方式中，气相硅沉积具体包括：
在氮气或者氩气的气氛下，含硅气体作为硅源，在多孔碳骨架上进行气相沉积。
在一些实施方式中，硅沉积具体包括：
在氮气或者氩气的气氛下，含硅气体作为硅源，含掺杂元素的蒸气作为掺杂元素源，在多孔碳骨架上进行气相沉积。
在一些实施方式中，含硅气体包括甲硅烷、丙硅烷、二氯硅烷、三氯硅烷、四氯硅烷中的一种或多种。
在一些实施方式中，含硅气体的流速为0.5-30L/min。
在一些实施方式中，氮气或者氩气的流速0.5-30L/min。
在一些实施方式中，气相沉积硅的沉积温度为500℃-900℃。
在一些实施方式中，气相沉积硅的沉积时间为6-24小时。
在合适的反应条件下进行硅沉积，使得硅均匀分散于多孔碳骨 架的孔中，提高硅碳复合材料的结构性能，提高材料的倍率性能。
在一些实施方式中，制备方法还包括制备碳层，
制备碳层：在硅碳复合材料表面进行碳包覆处理。
在一些实施方式中，碳包覆处理包括化学气相沉积法包碳、热解法包碳、水热法包碳、聚电解质修饰包碳中的任意一种方法。
硅碳复合材料表面包覆有碳层有利于提高硅碳复合材料的导电性，改善材料的倍率性能，同时碳层还可以提升硅碳复合材料与电解液之间的稳定性，改善电池的循环性能。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的 至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO2)、锂镍氧化物(如LiNiO2)、锂锰氧化物(如LiMnO2、LiMn2O4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi1/3Co1/3Mn1/3O2(也可以简称为NCM333)、LiNi0.5Co0.2Mn0.3O2(也可以简称为NCM523)、LiNi0.5Co0.25Mn0.25O2(也可以简称为NCM211)、LiNi0.6Co0.2Mn0.2O2(也可以简称为NCM622)、LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi0.85Co0.15Al0.05O2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料，负极活性材料包括一些实施方式中的硅碳复合材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，硅碳复合材料的质量含量大于等于20％，基于负极活性材料的总质量计。
在一些实施方式中，基于负极活性材料的总质量计，硅碳复合材料的质量含量可选为大于等于20％、大于等于25％、大于等于30％、大于等于35％、大于等于40％、大于等于45％、大于等于50％、大于等于55％、大于等于60％、大于等于65％、大于等于70％、大于等于75％、大于等于80％、大于等于85％、大于等于 90％、大于等于95％中的任意一种。
控制硅碳复合材料在合适的范围内，以使其电池具有优异的能量密度和循环性能。
在一些实施方式中，硅碳复合材料的质量含量为25％-90％，基于负极活性材料的总质量计。
在一些实施方式中，以负极活性材料的总质量计，硅碳复合材料的质量含量可选为25％、30％、40％、50％、60％、70％、80％、90％或由上述任意两点构成的范围中的数值。
控制硅碳复合材料在合适的范围内，可以兼顾电池的能量密度和循环寿命，综合改善电池的电化学性能。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，负极极片的压实密度为1.2g/cm3、1.25g/cm3、1.3g/cm3、1.35g/cm3、1.4g/cm3、1.45g/cm3、1.5g/cm3、1.55g/cm3、1.6g/cm3、1.65g/cm3、1.7g/cm3或由上述任意两点构成的范围中的数值。
控制负极极片的压实密度在合适的范围内，电池具有优异的能量密度。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将 负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复 合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池，包括正极极片、电解液、隔离膜和一些实施例方式中的负极极片。
在一些实施方式中，二次电池包括锂离子电池。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，二次电池的能量密度为400-550Wh/kg。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当 然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
下述实施例采用的各掺杂元素的单质和硅单质的锂离子扩散系数数据如下：
Sn元素的单质在25℃下的锂离子扩散系数为1×10-13cm2/S；
Ge元素的单质在25℃下的锂离子扩散系数为5×10-14cm2/S；
Sb元素的单质在25℃下的锂离子扩散系数为7×10-14cm2/S；
Bi元素的单质在25℃下的锂离子扩散系数为4×10-13cm2/S；
Sr元素的单质在25℃下的锂离子扩散系数为6×10-13cm2/S；
B元素的单质在25℃下的锂离子扩散系数为10-16cm2/S；
硅单质在25℃下的锂离子扩散系数为2×10-15cm2/S。
一、制备方法
实施例1
(1)正极极片的制备
将正极活性材料LiNi0.95Co0.04Mn0.01O2(NCM)、导电剂碳黑、粘结剂聚偏二氟乙烯(PVDF)按质量比为97％：1％：2％，加入N-甲基吡咯烷酮并混合均匀，得到正极浆料；之后将其涂覆于正极集流体上，经烘干、冷压、分切，得到正极极片。
(2)负极极片的制备
1)硅碳复合材料的制备
将酚醛树脂500g溶于2000ml乙醇中分散均匀，将蔗糖500g溶于水搅拌均匀得到混合液。将30g硫酸锡溶解于100g水中得到水溶液，将水溶液加入混合液中混合搅拌30min，把混合溶液置于反应釜中600℃反应8h得到粉末，然后在450℃下通入水蒸气进行活化造孔处理6小时，其中水蒸气的流速为1g/min，将处理后的产物置于马弗炉中在氮气保护下，于1200℃的温度下碳化4h，得到球状或 类球状多孔碳骨架。
含甲硅烷作为硅源，以氮气为保护气，在管式炉中进行气相沉积，得到硅碳复合材料。其中，甲硅烷的流速为0.06L/min；保护气的流速为4L/min；气相沉积的温度为450℃，时间为6小时。
将甲烷作为碳源，以氮气为保护气，在管式炉中进行碳源的气相沉积，其中甲烷的流速为6L/min，保护气的流速为15L/min，气相沉积的温度为900℃下，时间为6h，关闭气源进行降温得到硅碳复合材料。
2)负极极片的制备
将石墨、上述步骤1)制备的硅碳复合材料按照3：7的质量比混合得到负极活性材料，其中基于负极活性材料的总质量计，硅碳复合材料的质量分数为70％。
将上述混合后的负极活性材料、导电剂碳黑、碳纳米管(CNT)、粘结剂丁苯橡胶(SBR)、增稠剂羟甲基纤维素钠(CMC)，按照重量比为94.5％:1％:0.375％:2.8％:1.325％加入到去离子水中并混合均匀，得到负极浆料；将浆料涂覆在负极集流体上，经过烘干、冷压、分切得到负极极片。
(3)隔离膜
以聚丙烯膜作为隔离膜。
(4)电解液的制备
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将有机溶剂碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯，氟代碳酸乙烯酯(FEC)按照体积比1:1:1:1混合均匀，加入LiPF6溶解于有机溶剂中搅拌均匀，使得电解液的浓度为1mol/L，得到实施例1的电解液。
(5)电池的制备
将上述制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到电芯，给电芯焊接极耳，并将电芯装入铝壳中，随即注入电解液并封口，经过静置、冷压、化成、整形、容量测试等工序，获得锂离子二次电 池。
实施例2-3
实施例2-3中制备参数与实施例1基本相同，但是调整了硅碳复合材料的制备参数，具体参数见表1。
实施例4-7
实施例4-7中制备参数与实施例1基本相同，但是调整了硅碳复合材料的制备参数，并且将实施例1中的硫酸锡替换成硫酸锗、硫酸锑、硫酸铋、硫酸锡+硫酸锑。
实施例8-13
实施例8-13中制备参数与实施例1基本相同，但是调整了硅碳复合材料的制备参数，且实施例10、12中将硫酸锡的质量调整为10g和70g，其中实施例13中的碳源为蔗糖，制备的多孔碳骨架为非球形或非类球形结构，具体如下：
1)硅碳复合材料的制备
将蔗糖500g溶于水搅拌均匀得到混合液，将30g硫酸锡溶解于100g水中得到水溶液，将水溶液加入混合液中混合搅拌30min，把混合溶液置于反应釜中600℃反应8h得到粉末，然后在450℃下通入水蒸气进行活化造孔处理6小时，其中水蒸气的流速为1g/min，将处理后的产物置于马弗炉中在氮气保护下，于1200℃的温度下碳化4h得到非球形或非类球形的多孔碳骨架。
含甲硅烷作为硅源，以氮气为保护气，在管式炉中进行气相沉积，得到硅碳复合材料。其中，甲硅烷的流速为0.06L/min；保护气的流速为4L/min；气相沉积的温度为450℃，时间为6小时。
将甲烷作为碳源，以氮气为保护气，在管式炉中进行碳源的气相沉积，其中甲烷的流速为6L/min，保护气的流速为15L/min，气相沉积的温度为900℃下，时间为6h，关闭气源进行降温得到硅碳复合材料。
对比例1-2
对比例1-2中制备参数与实施例1基本相同，但是调整了硅碳复 合材料的制备参数，具体参数见表1，具体制备方法如下：
对比例1：与实施例1的区别在于将硫酸锡替换成硼酸。
对比例2：与实施例1的区别在于不加入硫酸锡。
二、性能测试
1、各元素的单质的锂离子扩散系数
(1)扣式电池的制备：将各掺杂元素或硅元素形成的单质材料、粘结剂、导电剂按照8：1：1的比例进行混合并加入到去离子水中，混合搅拌均匀得到负极浆料；将其涂覆在负极集流体铜箔的一个表面上，经过烘干、冷压、分切得到负极极片，利用冲片模具获得一定面积(本申请采用153.86mm2)的负极小圆片。以金属锂片为对电极、PP膜为隔离膜、电解液配方为：将碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯，FEC按照体积比1：1：1：1混合成溶剂，采用LiPF6作为锂盐溶于上述溶剂中，配置成浓度为1mol/L的溶液，在氩气保护的手套箱中组装成CR2032型的扣式电池。
(2)根据下述公式计算得到各掺杂元素或硅元素形成的单质材料的锂离子扩散系数：DLi＝1/(1000×S×Ziq)，
其中：DLi为锂离子扩散系数；S为上述制备的扣式电池中小圆片的面积；Ziq为各单质材料的比容量；
其中，Ziq可以采用如下步骤测试：在25℃下，采用0.1C电流对上述制备的扣式电池恒流充电至电池电压小于0.05V，然后静置120min；再用0.1C电流对上述制备的扣式电池恒流放电至电池电压大于1.5V，测量此时扣式电池的比容量记为Ziq。
2、掺杂元素在硅碳复合材料中形成的晶粒尺寸的测试
采用X射线粉末衍射仪(XRD)测试掺杂元素在碳硅元素在硅碳复合材料中形成的晶粒尺寸，X射线粉末衍射仪的型号为美国的X'pertPROo。晶粒尺寸的详细测试过程如下：
a、硅碳复合材料样品实测宽度Bm的测量。设置仪器扫描速率为2度/分钟，得到待测样品的XRD谱图，用JADE软件扣除CuKa2背底，得到各个衍射峰的Bm；
b、仪器宽化Bs测量。用与硅碳复合材料样品同物质、晶粒度在的标样，在与硅碳复合材料样品相同实验条件下，测定标样的XRD图谱，由图谱得到Bs；
c、半高宽B的计算。B＝Bm-Bs；(注：如果计算出B的单位是角度，需转换成弧度)
d、晶粒尺寸的计算；使用谢乐公式D＝Kλ/Bcosθ，其中K取0.89，θ为衍射角，λ＝0.154056nm，代入B，即可得到单个衍射峰所代表的晶面法向的晶粒厚度，取多个衍射峰分别计算取平均值后即得晶粒尺寸。
3、掺杂元素、硅基材料、多孔碳骨架的质量含量
参考EPA 6010D-2014标准进行测定；具体地，可以采用ICP-OES(元素分析-电感耦合等离子体发射光谱法)测试，先将待测样品用强酸溶解为液体，随后通过雾化的方式将液体引入ICP光源，进一步待测气态原子在强磁场中发生电离和激发后，由激发态恢复到基态；在上述过程中释放能量并被记录为不同的特征谱线，进行掺杂元素、硅基材料和多孔碳骨架的定量分析。
4、电池40％SOC放电时间
将电池单体以0.33C恒流放电至2.8V，静置30min；以0.33C恒流充电至4.25V而后以0.05C恒压直至电压稳定，静置30min；以0.33C恒流放电至2.8V，此时读取初始容量C0，静置30min；以0.33C恒流充电至4.25V而后以0.05C恒压直至电压稳定，静置30min；以0.33C恒流放电至0.4C0Ah(40％)SOC静置60min；4.5C恒流放电至2.8V，记录放电时间。
5、电池快充时间
25℃下，将各实施例和对比例的电池以1C(即1h内完全放掉额定容量的电流值)的电流进行第一次充电和放电，具体包括：将电池以1C倍率恒流充电至电压4.3V，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至电压2.8V，记录其实际容量为C0。
然后将电池依次以2.0C0、2.5C0、3.0C0、3.5C0、4.0C0、4.5C0、5.0C0、5.5C0、恒流充电至全电池充电截止电压4.3V或者0V负极截止电位(以先达到者为准)，每次充电完成后需以1C 0放电至全电池放电截止电压2.8V，记录不同充电倍率下充电至10％、20％、30％、……、80％SOC(State of Charge，荷电状态)时所对应的负极电位，绘制出不同SOC态下的充电倍率-负极电位曲线，线性拟合后得出不同SOC态下负极电位为0V时所对应的充电倍率，该充电倍率即为该SOC态下的充电窗口，分别记为C20％SOC、C30％SOC、C40％SOC、C50％SOC、C60％SOC、C70％SOC、C80％SOC，根据公式(60/C20％SOC+60/C30％SOC+60/C40％SOC+60/C50％SOC+60/C60％SOC+60/C70％SOC+60/C80％SOC)×10％计算得到该电池从10％SOC充电至80％SOC的充电时间T，单位为min。该时间越短，则电池的快速充电性能越优秀。
6、电池25℃循环性能测试
将各实施例和对比例制备得到的二次电池以0.5C倍率恒流充电至充电截止电压4.25V，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至放电截止电压2V，静置5min，此为一个充放电循环。按照此方法对电池进行循环充放电测试，直至电池容量衰减至80％。此时的循环圈数即为电池在25℃下的循环寿命。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表1、表2和表3。
表1
表2
表3
根据上述结果可知，实施例1-13中的硅碳复合材料均包含多孔碳骨架；硅基材料，至少部分硅基材料设置于多孔碳骨架孔隙；以及多孔碳骨架包括掺杂元素Sn、Ge、Sb、Bi中的至少一种，Sn、Ge、Sb或Bi的单质在25℃下的的锂离子扩散系数大于硅的单质在25℃下的的锂离子扩散系数。
从实施例1-13与对比例1-2的对比可见，本申请的硅碳复合材料有利于降低电池的快充时间，延长电池的放电时间，提高电池的倍率性能，提高电池的循环圈数，延长电池的循环寿命。
从实施例1、4-7与对比例1-2的对比可见，掺杂元素包括Sn、Ge、Sb、Bi中的一种或两种，均有利于提升电池的循环圈数和40％SOC放电时间、降低其电池的快充时间，改善电池的循环性能和倍率性能。
从实施例8-9、11与实施例1的对比可见，控制晶粒的尺寸小于等于10nm，有利于提升电池的循环圈数和40％SOC放电时间、降低其电池的快充时间，改善电池的倍率性能和循环性能。从实施例8、11与实施例1、9的对比可见，进一步控制晶粒的尺寸为3nm-7nm，有利于进一步提升电池的循环圈数和40％SOC放电时间、降低其电池的快充时间，进一步改善电池的倍率性能和循环性能。
从实施例10-12中可见，基于硅碳复合材料的总质量计，控制掺杂元素的质量分数小于等于7％，以使其电池具有较低的快充时间、较高的放电时间和较多的循环圈数，使得电池具有优异的倍率性能和循环性能。从实施例10-11与实施例12的对比可见，控制掺杂元素的质量分数为1％-3％，有利于进一步提升电池的循环圈数和40％SOC放电时间、降低其电池的快充时间，进一步改善电池的倍率性能和循环性能。
从实施例1-3与实施例13对比可见，多孔碳骨架为球形或类球形，有利于进一步提升40％SOC放电时间和降低其电池的快充时间，提高电池的倍率性能，延长电池的循环寿命。
从实施例1-2与实施例3对比可见，控制硅碳复合材料的体积分布粒径Dv50小于等于5μm，有利于进一步提升40％SOC放电时间和降低其电池的快充时间，提高电池的倍率性能，提高电池的循环寿命，改善电池的循环性能。从实施例1与实施例2-3的对比可见，控制硅碳复合材料的体积分布粒径Dv50为1μm-3μm，有利于进一步提升40％SOC放电时间和降低其电池的快充时间，提高电池的倍率性能，改善电池的动力学性能。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的 构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (20)

  1. 一种硅碳复合材料，所述硅碳复合材料包括：
    多孔碳骨架；
    硅基材料，至少部分所述硅基材料设置于所述多孔碳骨架的孔隙中；以及
    掺杂元素，至少部分所述掺杂元素分布在所述多孔碳骨架中；
    其中，所述掺杂元素满足：掺杂元素的单质在25℃下的锂离子扩散系数大于硅单质在25℃下的锂离子扩散系数。
  2. 根据权利要求1所述的硅碳复合材料，其特征在于，
    所述掺杂元素的单质的在25℃下的锂离子扩散系数大于10- 14cm2/S，可选为大于10-14cm2/S且小于等于10-13cm2/S；和/或，
    所述硅单质在25℃下的锂离子扩散系数小于10-14cm2/S，可选为大于10-15cm2/S且小于10-14cm2/S。
  3. 根据权利要求1或2所述的硅碳复合材料，其特征在于，所述掺杂元素包括Sn、Ge、Sb、Bi、Sr中的至少一种。
  4. 根据权利要求1至3中任一项所述的硅碳复合材料，其特征在于，至少部分所述掺杂元素在所述硅碳复合材料中形成晶粒；
    可选地，所述晶粒的尺寸小于等于10nm，更可选为3nm-7nm。
  5. 根据权利要求1至4中任一项所述的硅碳复合材料，其特征在于，基于所述硅碳复合材料的总质量计，所述掺杂元素的质量分数小于等于7％，可选为1％-3％。
  6. 根据权利要求1至5中任一项所述的硅碳复合材料，其特征在于，所述多孔碳骨架为球形或类球形。
  7. 根据权利要求1至6中任一项所述的硅碳复合材料，其特征在于，基于所述硅碳复合材料的总质量计，所述硅基材料的质量分数大于等于30％，可选为35％-50％；和/或，
    基于所述硅碳复合材料的总质量计，所述多孔碳骨架的质量分数大于等于30％，可选为40％-60％。
  8. 根据权利要求1至7中任一项所述的硅碳复合材料，其特征在于，所述硅碳复合材料的体积分布粒径Dv50小于等于5μm，可选为1μm-3μm。
  9. 根据权利要求1至8中任一项所述的硅碳复合材料，其特征在于，所述硅碳复合材料满足下述(1)-(4)中的至少一项：
    (1)所述多孔碳骨架的比表面积为1000m2/g-2500m2/g；
    (2)所述多孔碳骨架的孔径为0.5nm-100nm；
    (3)所述多孔碳骨架的孔容为0.5cm3/g-8.5cm3/g；
    (4)所述多孔碳骨架的体积分布粒径Dv50为0.3μm-5μm。
  10. 根据权利要求1至9中任一项所述的硅碳复合材料，其特征在于，所述硅碳复合材料的至少一部分表面上具有碳层。
  11. 一种硅碳复合材料的制备方法，其特征在于，包括如下步骤：
    制备含有掺杂元素的多孔碳骨架，其中，所述掺杂元素满足：掺杂元素的单质在25℃下的锂离子扩散系数大于硅单质在25℃下的锂离子扩散系数；
    在所述多孔碳骨架的孔隙中沉积硅基材料，得到所述硅碳复合材料。
  12. 根据权利要求11所述的制备方法，其特征在于，所述多孔碳骨架的制备包括溶剂热反应、活化造孔和高温碳化；
    溶剂热反应：将含有不饱和基团的树脂和/或糖类、溶剂、含掺杂元素的水溶液混合，进行溶剂热反应，得到第一产物；
    活化造孔：向所述第一产物中通入水蒸气进行活化造孔处理，得到第二产物；
    高温碳化：将所述第二产物进行高温碳化处理，得到多孔碳骨架。
  13. 根据权利要求12所述的制备方法，其特征在于，所述溶剂热反应的反应温度为400℃-750℃；和/或，所述溶剂热反应的反应时间为4h-10h。
  14. 根据权利要求12或13所述的制备方法，其特征在于，所述含有不饱和基团的树脂与糖类的质量比为(2:8)-(9:1)，可选为(4:6)-(6:4)。
  15. 根据权利要求12至14中任一项所述的制备方法，其特征在于，所述含有不饱和基团的树脂包括酚醛树脂、糠醛树脂、木质素基活性炭中的至少一种；和/或，所述糖类包括蔗糖、葡萄糖、壳聚糖中的至少一种。
  16. 根据权利要求12至15中任一项所述的制备方法，其特征在于，所述活化造孔的处理温度为400℃-500℃；和/或，
    所述活化造孔的处理时间为4h-8h；和/或，
    所述水蒸气的流速为0.5g/min-1g/min。
  17. 根据权利要求11至16中任一项所述的制备方法，其特征在于，所述气相沉积硅的沉积温度为500℃-900℃；和/或，所述气相 沉积硅的沉积时间为6h-24h。
  18. 根据权利要求11至17中任一项所述的制备方法，其特征在于，所述制备方法还包括制备碳层：在所述硅碳复合材料的表面进行碳包覆处理。
  19. 一种二次电池，包括负极极片，所述负极极片包括负极集流体和设置在所述负极集流体表面的负极膜层，所述负极膜层包括负极活性材料，所述负极活性材料包括如权利要求1至10中任一项所述的硅碳复合材料或根据权利要求11至18中任一项所述的制备方法制备得到的硅碳复合材料。
  20. 一种用电装置，其特征在于，包括权利要求19所述的二次电池。
PCT/CN2023/091726 2023-04-28 2023-04-28 硅碳复合材料及其制备方法、负极极片、二次电池和用电装置 WO2024221435A1 (zh)

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US20110223494A1 (en) * 2010-03-12 2011-09-15 Energ2, Inc. Mesoporous carbon materials comprising bifunctional catalysts
CN103840140A (zh) * 2012-11-21 2014-06-04 清华大学 多孔碳硅复合材料及其制备方法
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