CN105870427B - Lithium ion battery negative electrode material, preparation method thereof and lithium ion battery - Google Patents

Abstract

The invention provides a lithium ion battery negative electrode material, which includes an inner core and an outer shell, and a hollow layer is contained between the inner core and the outer shell; the outer shell is made of carbon material, and the inner core is made of porous silicon material. The inner core and the hollow layer cooperate to accommodate the huge volume change of silicon particles during charging and discharging. The outer shell can buffer the volume change, reduce stress, stabilize the structure of silicon-carbon composite materials, improve the cycle stability of the electrode, and reduce the active material and electrolysis. The contact with the liquid can obtain a stable solid electrolyte interface film (SEI film), improve the Coulombic efficiency of the electrode, prevent the agglomeration of nanoparticles, and improve the conductivity of the electrode. The negative electrode material prepared by using this core-shell structure has a high specific capacity, and at the same time, the lithium ion battery made by this negative electrode material has good electrochemical cycle performance. Moreover, the preparation method disclosed by the invention is simple and easy, and is beneficial to large-scale production.

Description

A kind of negative electrode material of lithium ion battery, its preparation method and lithium ion battery

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery negative electrode material, a preparation method thereof and a lithium ion battery.

Background technique

In the study of anode materials for lithium-ion batteries, silicon-based anode materials have attracted much attention due to their huge lithium storage capacity (4200mAh/g), slightly higher discharge platform than carbon materials, and abundant reserves in the earth's crust. However, during the charge and discharge process, the lithium-deintercalation reaction of silicon will be accompanied by a volume change of 310%, which will easily cause the cracking of the electrode and the shedding of the active material, resulting in the rapid deterioration of the cycle performance of the electrode.

One of the approaches to solve the above problems is to synthesize silicon-based composites to buffer the volume expansion of the electrodes and improve the cycling stability of the electrodes. Carbon materials have the advantages of flexibility, good electronic conductivity, small density, small volume expansion, and appropriate lithium intercalation ability, making silicon-carbon composites the best choice for silicon-based negative electrode materials.

For silicon-carbon composites, reasonable structural design is the key to obtain excellent electrochemical performance, and the core-shell structure is one of the structures to obtain excellent electrochemical performance. In the prior art, in the prepared silicon-carbon composite material with core-shell structure, the inner core is usually granular silicon material. When the obtained core structure is porous silicon, the carbon layer in the obtained core-shell structure covers all surfaces of the silicon material, including the inner pore wall surface of the silicon material, forming a filling coating. The preparation of silicon-carbon composites of these two core-shell structures usually adopts a template method, such as: after using silicon dioxide as a sacrificial template to obtain a carbon shell, then remove silicon dioxide to obtain a silicon-carbon composite material with a core-shell structure ( See N.Liu, Z.Lu, J.Zhao, M.T.McDowell, H.W.Lee, W.Zhao and Y.Cui, Nature Nanotechnology, 2014, 9, 187; Z.D.Lu, N.Liu, H.W.Lee, J.Zhao, W.Y.Li , Y.Z.Li and Y.Cui, ACS Nano, 2015, 9, 2540; N.Liu, H.Wu, M.T.McDowell, Y.Yao, C.M.Wang and Y.Cui, Nano Letters, 2012, 12, 3315; H. Kim, B. Han, J. Choo, J. Cho, Angew. Chem. Int. Ed., 2008(52):10151-10154). The silicon-carbon composite material with core-shell structure prepared by this method can effectively alleviate the problem caused by the volume expansion of silicon, and obtain better cycle performance and higher specific capacity. However, this preparation method is complicated to operate, and the available template materials are less and difficult to synthesize. The removal of the template requires the use of highly corrosive hydrofluoric acid, which has high cost and low yield. At the same time, the removal process of the template is easy to destroy the core-shell structure. . Obviously, this method significantly restricts the commercial application of the core-shell structure. However, how to prepare large-scale silicon-carbon composites with core-shell structure with excellent properties by a simple method is still an urgent problem to be solved.

Contents of the invention

In view of this, the technical problem to be solved in the present invention is to provide a negative electrode material for a lithium ion battery, a preparation method thereof, and a lithium ion battery. At the same time, the lithium-ion battery made of this negative electrode material has better electrochemical cycle performance.

The invention provides a negative electrode material for a lithium ion battery, comprising an inner core and an outer shell, and a hollow layer is contained between the inner core and the outer shell;

The outer shell is made of carbon material, and the inner core is made of porous silicon material.

Preferably, the thickness of the shell is 100 nm˜5 μm.

Preferably, the particle diameter of the inner core is 500 nm-10 μm, and the pore diameter of the inner core is 10 nm-100 nm.

The present invention provides a kind of preparation method of above-mentioned negative electrode material of lithium ion battery, comprises the following steps:

A) Alkali treatment of calcium silicide to obtain pre-treated calcium silicide;

B) heating the pre-treated calcium silicide, and passing gaseous hydrocarbon compounds to carry out chemical vapor deposition to obtain chemical vapor deposition products;

C) Pickling the chemical vapor deposition product to obtain a lithium ion battery negative electrode material.

Preferably, the particle size of the pre-treated calcium silicide is 500nm-10μm.

Preferably, in step B), heating the pre-treated calcium silicide specifically includes: placing the pre-treated calcium silicide in a high-temperature tube furnace and heating in the presence of protective gas.

Preferably, the temperature of the chemical vapor deposition is 600° C. to 1000° C.; the time of the chemical vapor deposition is 10 min to 120 min.

Preferably, the acid solution used in the pickling treatment is selected from one or more of hydrochloric acid, nitric acid, hydrobromic acid and hydroiodic acid.

Preferably, the mass percentage of the acid solution is 5%-36%.

The present invention also provides a lithium ion battery, including a positive electrode, a negative electrode, a diaphragm and an electrolyte, and the negative electrode includes the above lithium ion battery negative electrode material or the lithium ion battery negative electrode material prepared by the above preparation method.

The invention provides a lithium ion battery negative electrode material, which includes an inner core and an outer shell, and a hollow layer is contained between the inner core and the outer shell; the outer shell is made of carbon material, and the inner core is made of porous silicon material. There is a hollow layer between the inner porous silicon material and the outer carbon material. The inner core and the hollow layer work together to accommodate the huge volume change of silicon particles during charging and discharging, which is very critical for lithium-ion battery anode materials to obtain good cycle performance. The shell can buffer the volume change, reduce the stress, stabilize the structure of the silicon-carbon composite material, improve the cycle stability of the electrode, reduce the contact between the active material and the electrolyte, obtain a stable solid electrolyte interface film (SEI film), and improve the Coulomb of the electrode Efficiency, it can also prevent the agglomeration of nanoparticles and improve the conductivity of the electrode. The negative electrode material prepared by using this core-shell structure has a high specific capacity, and at the same time, the lithium ion battery made by this negative electrode material has good electrochemical cycle performance.

The present invention also provides a preparation method for the negative electrode material of the lithium ion battery, comprising the following steps: A) performing alkali treatment on calcium silicide to obtain pre-treated calcium silicide; B) heating the pre-treated calcium silicide, and passing gas hydrocarbons The compound is subjected to chemical vapor deposition to obtain a chemical vapor deposition product; C) the chemical vapor deposition product is subjected to pickling treatment to obtain a lithium ion battery negative electrode material. The existing template method is complicated to operate, there are few template materials available and the synthesis is difficult. The removal of the template requires the use of highly corrosive and highly toxic hydrofluoric acid, which has high cost and low yield. At the same time, the removal process of the template is easy destroy the core-shell structure. Obviously, this method significantly restricts the commercial application of the core-shell structure. Compared with the prior art, the preparation method disclosed in the present invention is simple and easy to implement, is beneficial to large-scale production, and the prepared negative electrode material has a higher specific capacity, and at the same time, the lithium ion battery made by this negative electrode material has better performance. electrochemical cycle performance.

Description of drawings

Fig. 1 is the SEM picture of the negative electrode material that the embodiment of the present invention 1 prepares;

Fig. 2 is the XRD pattern of the negative electrode material prepared in Example 1 of the present invention;

Fig. 3 is the initial charging and discharging curve diagram of the lithium-ion battery prepared in Example 1 of the present invention;

Fig. 4 is the cycle graph of the lithium-ion battery prepared in Example 1 of the present invention;

Fig. 5 is a graph showing charge-discharge specific capacity curves of the lithium-ion battery prepared in Example 1 of the present invention at different rates.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The invention provides a negative electrode material for a lithium ion battery, comprising an inner core and an outer shell, and a hollow layer is contained between the inner core and the outer shell;

The outer shell is made of carbon material, and the inner core is made of porous silicon material.

The lithium ion battery negative electrode material disclosed by the invention has a core-shell structure, and the core-shell structure contains a hollow layer, which separates the shell from the core; the shell is made of carbon material, and the core is made of porous silicon material. On the pore walls of the porous silicon material, no carbon material is attached.

The carbon material in the present invention is obtained from gaseous hydrocarbon compounds through chemical vapor deposition. The present invention has no special limitation on the gaseous hydrocarbon compounds, and the gaseous hydrocarbon compounds well-known to those skilled in the art can be used. In the present invention, one or more of methane, ethylene and acetylene is preferably used.

The particle size of the lithium ion battery negative electrode material disclosed by the present invention is preferably 1 μm to 20 μm, more preferably 3 μm to 10 μm; the thickness of the shell is 100 nm to 5 μm, preferably 1 μm to 3 μm; the particle size of the inner core is 500 nm to 10 μm, preferably 1 μm˜5 μm; the pore diameter of the core is 10 nm˜100 nm, preferably 20 nm˜50 nm.

The lithium-ion battery negative electrode material disclosed by the present invention has a core-shell structure, that is, the carbon material wrapping layer is outside the entire inner core, and there is no carbon material attached to the surface of the hole wall inside the inner core, which is a non-filled wrapping. There is a hollow layer between the inner porous silicon material and the outer carbon material. The inner core and the hollow layer work together to accommodate the huge volume change of silicon particles during charging and discharging, which is very critical for lithium-ion battery anode materials to obtain good cycle performance. The shell can buffer the volume change, reduce the stress, stabilize the structure of the silicon-carbon composite material, improve the cycle stability of the electrode, reduce the contact between the active material and the electrolyte, obtain a stable SEI film, improve the Coulombic efficiency of the electrode, and prevent nano The particles are agglomerated to improve the conductivity of the electrode. The negative electrode material prepared by using this core-shell structure has a high specific capacity, and at the same time, the lithium ion battery made by this negative electrode material has good electrochemical cycle performance.

The present invention provides a kind of preparation method of above-mentioned negative electrode material of lithium ion battery, comprises the following steps:

A) Alkali treatment of calcium silicide to obtain pre-treated calcium silicide;

B) heating the pre-treated calcium silicide, and passing gaseous hydrocarbon compounds to carry out chemical vapor deposition to obtain chemical vapor deposition products;

C) Pickling the chemical vapor deposition product to obtain a lithium ion battery negative electrode material.

The above-mentioned calcium silicide is preferably ball-milled calcium silicide, which is obtained by ball-milling calcium silicide particles, more preferably, ball-milling calcium silicide particles in a protective atmosphere. The present invention has no special limitation on the calcium silicide particles used, and the calcium silicide particles well known to those skilled in the art can be used. The calcium silicide particles preferably used in the present invention are purchased from Sinopharm Chemical Reagent Co., Ltd. (Ca≈30%). The particle size of the calcium silicide particles is preferably 1 μm to 100 μm. The present invention has no special limitation on the ball milling method, and the ball milling method well known to those skilled in the art can be used. The present invention preferably adopts high-energy mechanical ball milling. The rotational speed of the ball mill is preferably 300-600 rpm, more preferably 350-450 rpm; the time of the ball mill is preferably 6-10 hours, more preferably 7-9 hours. In the present invention, there is no special limitation on the protective gas used in the protective atmosphere, and the protective gas well known to those skilled in the art can be used. The present invention preferably uses nitrogen or argon.

After the above calcium silicide is obtained, it is subjected to alkali treatment. The method of the present invention has no special limitation on the method of the alkali treatment, and the alkali treatment method well known to those skilled in the art can be used. The present invention preferably reacts with stirring in an alkaline solution. The present invention has no special limitation on the alkaline solution used, and the alkaline solution well known to those skilled in the art can be used. The present invention preferably adopts one or more of sodium hydroxide solution, potassium hydroxide solution and lithium hydroxide solution. The concentration of the alkaline solution is preferably 0.1-5 mol/L, more preferably 1-3 mol/L. The solvent of the alkaline solution is preferably water. The mass ratio of the solute of the alkaline solution to the calcium silicide particles is preferably 2-6:1-4, more preferably 3-5:2-3.

The alkali treatment time is preferably 10-48 hours, more preferably 16-24 hours. The temperature of the alkali treatment is preferably 15-35°C, more preferably 20-30°C.

The particle size of the pretreated calcium silicide obtained above is preferably 500 nm to 10 μm, more preferably 1 μm to 5 μm.

Then, the pre-treatment calcium silicide is heated, specifically: placing the pre-treatment calcium silicide in a high-temperature tube furnace, and heating in the presence of protective gas. The present invention has no special limitation on the high-temperature tube furnace, and a high-temperature tube furnace well known to those skilled in the art can be used. The present invention preferably uses a quartz tube furnace. The present invention has no special limitation on the protective gas used, and the protective gas well known to those skilled in the art can be used. The present invention preferably uses nitrogen or argon. The gas flow rate of the protective gas is preferably 200 scc min ^-1 , and after the heating, the rate of temperature rise is preferably 5°C min ^-1 to 15°C min ^-1 , more preferably 10°C min ^-1 .

After being heated to the temperature of chemical vapor deposition, the gaseous hydrocarbon compound is introduced to carry out chemical vapor deposition to obtain chemical vapor deposition products. The method of chemical vapor deposition is not particularly limited in the present invention, and the method of chemical vapor deposition well known to those skilled in the art can be used. The present invention is preferably atmospheric pressure vapor deposition. The present invention has no special limitation on the gaseous hydrocarbon compounds, and the gaseous hydrocarbon compounds well-known to those skilled in the art can be used. In the present invention, one or more of methane, ethylene and acetylene is preferably used. The flow rate of the gaseous hydrocarbon compound is preferably 100 scc min ^-1 to 300 scc min ^-1 , more preferably 150 scc min ^-1 to 250 scc min ^-1 . The volume-to-mass ratio of the gaseous hydrocarbon compound to the pretreatment calcium silicide is preferably 1L-36L: 1g-10g, more preferably 6.75L-22.5L: 3g-8g.

The time when the gaseous hydrocarbon compound is introduced is the time for chemical vapor deposition, preferably 10 min to 120 min, more preferably 45 min to 90 min, more preferably 45 min; the temperature of the chemical vapor deposition is preferably 600°C to 1000°C , more preferably 800°C to 900°C.

After the chemical vapor deposition is completed, the obtained product is preferably cooled to room temperature with a high-temperature tube furnace to obtain a chemical vapor deposition product.

The chemical vapor deposition product is subjected to pickling treatment to obtain a lithium ion battery negative electrode material.

Specifically, the chemical vapor deposition product is stirred and reacted in an acid solution to obtain a lithium ion battery negative electrode material.

The function of the pickling treatment is to remove calcium carbide to obtain a core porous silicon material. The acid solution used in the pickling treatment is selected from one or more of hydrochloric acid, nitric acid, hydrobromic acid and hydroiodic acid; the mass percentage of the acid solution is preferably 5% to 36%, more preferably 15% ~20%. The volume-to-mass ratio of the acid solution to the chemical vapor deposition product is preferably 100mL-300mL: 3g-12g, more preferably 150mL-250mL: 5g-10g.

The time for the acid washing is the time for stirring and reacting in the acid solution, preferably 2h-12h, more preferably 3h-6h. After the stirring reaction in the acid solution, the reacted product is preferably filtered, washed and dried to obtain the lithium ion battery negative electrode material.

The present invention also provides a lithium ion battery, including a positive electrode, a negative electrode, a diaphragm and an electrolyte, and the negative electrode includes the above lithium ion battery negative electrode material or the lithium ion battery negative electrode material prepared by the above preparation method.

The present invention does not have special limitation to the kind of described positive electrode, separator and electrolyte, as, described positive electrode can adopt lithium sheet; Described separator can adopt polypropylene microporous membrane; Described electrolyte can adopt ethylene carbonate (EC ) and dimethyl carbonate (DMC) mixture. Specifically, in the present invention, the above-mentioned lithium ion battery negative electrode material and binder (styrene-butadiene rubber (SBR): sodium carboxymethyl cellulose (CMC) = 3:7 mass ratio), conductive agent Super P according to 80:10: Mix at a weight ratio of 10, add an appropriate amount of water as a dispersant to make a slurry, and then evenly coat it on a copper foil current collector, and vacuum-dry and roll to prepare a negative electrode sheet; use metal lithium as a counter electrode, 1mol/ The mixed solvent of L LiPF ₆ (EC: DMC = 1:1 volume ratio) was used as the electrolyte, and the polypropylene microporous membrane (Celgard 2400) was used as the separator, and a simulated battery was assembled in an argon-protected glove box.

In the present invention, a constant current charging and discharging experiment is carried out on the obtained simulated battery to test the cycle performance of the lithium ion battery, the charging and discharging voltage is limited to 0.001-1.5 volts, and the charging and discharging current density is 150mA/g. The electrochemical performance of the battery was tested with a Land tester (Wuhan Xinnuo Electronics Co., Ltd.), and the test condition was room temperature. Experimental results show that the first discharge specific capacity of the lithium-ion battery provided by the present invention is not less than 1254mAh/g, and after 100 cycles of charge and discharge, the capacity retention rate is not less than 80.3%, and the Coulombic efficiency is not less than 99.4%. cycle performance.

At the same time, the present invention also investigates the cycle performance of the obtained lithium-ion battery at different rates. The experimental results show that the lithium-ion battery provided by the present invention has relatively high performance at 0.1C, 0.2C, 0.5C, 1C and 2C. High specific capacity, not less than 650mAh/g after 50 2C cycles, good rate performance.

The invention provides a lithium ion battery negative electrode material, which includes an inner core and an outer shell, and a hollow layer is contained between the inner core and the outer shell; the outer shell is made of carbon material, and the inner core is made of porous silicon material. The core-shell structure disclosed in the present invention means that the carbon material wrapping layer is outside the entire inner core, and does not include the inner hole wall surface of the inner core, which is a non-filled wrapping. There is a hollow layer between the inner porous silicon material and the outer carbon material. The inner core and the hollow layer work together to accommodate the huge volume change of silicon particles during charging and discharging, which is very critical for lithium-ion battery anode materials to obtain good cycle performance. The shell can buffer the volume change, reduce the stress, stabilize the structure of the silicon-carbon composite material, improve the cycle stability of the electrode, reduce the contact between the active material and the electrolyte, obtain a stable SEI film, improve the Coulombic efficiency of the electrode, and prevent nano The particles are agglomerated to improve the conductivity of the electrode. The negative electrode material prepared by using this core-shell structure has a high specific capacity, and at the same time, the lithium ion battery made by this negative electrode material has good electrochemical cycle performance. At the same time, the preparation method disclosed by the invention is simple and easy to implement, and is beneficial to large-scale production. Experimental results show that under the condition that the charging and discharging voltage is 0.001-1.5 volts and the charging and discharging current density is 150mA/g, the first discharge specific capacity of the lithium-ion battery provided by the present invention is not less than 1254mAh/g, and the cycle charging and discharging is 100 After several times, the capacity retention rate is not lower than 80.3%, the Coulombic efficiency is not lower than 99.4%, and has good cycle performance.

In order to further illustrate the present invention, a lithium ion battery negative electrode material provided by the present invention, its preparation method and lithium ion battery are described in detail below in conjunction with the examples, but it should not be understood as limiting the protection scope of the present invention.

Example 1

Calcium silicide particles with a calcium content of 30% were placed in a ball milling tank, then absolute ethanol was added as a ball milling medium, and under the protection of an argon atmosphere, high-energy mechanical ball milling was performed at a speed of 400 rpm for 8 hours to obtain a calcium silicide slurry with a low particle size.

Add the obtained low particle size calcium silicide slurry into 2 mol/L sodium hydroxide aqueous solution, stir and react at 25°C for 20 hours, then filter and vacuum dry to obtain pretreated calcium silicide with a particle size of 3 μm, in which the hydroxide The mass ratio of sodium to calcium silicide particles is 8:5.

Place the pre-treated calcium silicide in a quartz tube furnace and heat it in an argon atmosphere. The flow rate of argon is controlled at 200scc min ^-1 , the rate of temperature rise after heating is controlled at 10°C min ^-1 , and heated to 900°C After that, stop heating and keep warm, feed ethylene gas, and control the flow rate to 200scc min ^-1 , after 60min, stop feeding ethylene gas, cool the product to room temperature with the furnace, and obtain the chemical vapor deposition product, wherein the ethylene gas The volume-to-mass ratio of the pre-treatment calcium silicide is 12L:8g.

The chemical vapor deposition product was added to hydrochloric acid with a mass fraction of 20%, stirred and reacted at room temperature for 4 hours, then filtered, washed several times to neutrality, and the product was dried to obtain a lithium ion battery negative electrode material, wherein hydrochloric acid and chemical vapor deposition The volume to mass ratio of the product is 200mL: 10g.

The present invention carries out scanning electron microscope scanning analysis to the obtained lithium ion battery negative electrode material, and the result is as shown in Figure 1, and Figure 1 is the SEM figure of the lithium ion battery negative electrode material prepared by Example 1 of the present invention, as can be seen from Figure 1, the inner core The porous silicon material, the outer carbon material and the hollow layer between them form a core-shell structure composite material with a particle size of 1 μm to 20 μm.

The obtained lithium-ion battery negative electrode material was analyzed by X-ray diffractometer, and the XRD pattern of the negative electrode material in Example 1 of the present invention was obtained, as shown in FIG. 2 . It can be seen from FIG. 2 that the diffraction peaks of the prepared lithium-ion battery negative electrode material are corresponding peaks of silicon.

The particle size D50 and specific surface area of the obtained lithium-ion battery negative electrode material were tested, and the test results were: the median particle size D50 of the lithium-ion battery negative electrode material was 5 μm, and the specific surface area was 5.4 m ² /g.

In the present invention, the above lithium ion battery negative electrode material is mixed with a binder (SBR:CMC=3:7 mass ratio) and a conductive agent Super P according to a weight ratio of 80:10:10, and an appropriate amount of water is added as a dispersant to prepare a slurry , and then uniformly coated on the copper foil current collector, and vacuum-dried and rolled to prepare a negative electrode sheet; with metal lithium as the counter electrode, a mixed solvent of 1mol/L LiPF ₆ (EC:DMC=1:1 volume ratio) as the electrolyte, polypropylene microporous membrane (Celgard 2400) as the separator, and assembled into a simulated battery in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan ^Xinnuo Electronics Co., Ltd.). The charge-discharge curve is shown in Figure 3; the obtained cycle performance curve is shown in Figure 4.

Experimental results show that the lithium-ion battery provided by the present invention has a specific capacity of 1527mAh/g for the first discharge, and a coulombic efficiency of 80.7% for the first time; after 100 cycles of charging and discharging, the capacity retention rate is 90.1%, and the coulombic efficiency is 99.9%. cycle performance.

At the same time, the present invention also investigates the charge-discharge cycle performance of the obtained lithium-ion battery at different rates, as shown in FIG. 5 . Experimental results show that the lithium ion battery provided by the invention has high specific capacity at 0.1C, 0.2C, 0.5C, 1C and 2C, and it is still not less than 650mAh/g after 50 cycles at 2C, and the rate performance is good.

Example 2

Calcium silicide particles with a calcium content of 30% were placed in a ball milling tank, then absolute ethanol was added as a ball milling medium, and under the protection of an argon atmosphere, high-energy mechanical ball milling was performed at a speed of 400 rpm for 8 hours to obtain a calcium silicide slurry with a low particle size.

Add the obtained low particle size calcium silicide slurry into 2 mol/L sodium hydroxide aqueous solution, stir and react at 25°C for 20 hours, then filter and vacuum dry to obtain pretreated calcium silicide with a particle size of 3 μm, in which the hydroxide The mass ratio of sodium to calcium silicide particles is 8:5.

Place the pre-treated calcium silicide in a quartz tube furnace and heat it in an argon atmosphere. The flow rate of argon is controlled at 200scc min ^-1 , the rate of temperature rise after heating is controlled at 10°C min ^-1 , and heated to 800°C After that, stop heating and keep warm, feed ethylene gas, and control the flow rate to 200scc min ^-1 , after 60min, stop feeding ethylene gas, cool the product to room temperature with the furnace, and obtain the chemical vapor deposition product, wherein the ethylene gas The volume-to-mass ratio of the pre-treatment calcium silicide is 12L:8g.

The chemical vapor deposition product was added to hydrochloric acid with a mass fraction of 20%, stirred and reacted at room temperature for 4 hours, then filtered, washed several times to neutrality, and the product was dried to obtain a lithium ion battery negative electrode material, wherein hydrochloric acid and chemical vapor deposition The volume to mass ratio of the product is 200mL: 10g.

The present invention tests the particle size D50 and specific surface area of the obtained lithium ion battery negative electrode material, and the test results are: the median particle size D50 of the lithium ion battery negative electrode material is 3 μm, and the specific surface area is 5.4 m ² /g.

In the present invention, the above lithium ion battery negative electrode material and binder (styrene-butadiene rubber (SBR): sodium carboxymethyl cellulose (CMC) = 3:7 mass ratio), conductive agent Super P according to the weight of 80:10:10 Mixing, adding an appropriate amount of water as a dispersant to make a slurry, and then evenly coating on the copper foil current collector, and vacuum drying, rolling, to prepare a negative electrode sheet; with metal lithium as the counter electrode, 1mol/L LiPF A mixed solvent of ₆ (EC:DMC=1:1 volume ratio) was used as the electrolyte, and a polypropylene microporous membrane (Celgard 2400) was used as the separator, and a simulated battery was assembled in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). The charge and discharge current density was 150mAg ^-1 , and the charge and discharge voltage range was 0.001-1.5V.

Experimental results show that the lithium-ion battery provided by the invention has a specific capacity of 1254mAh/g for the first discharge, and a coulombic efficiency of 76.2% for the first time; after 100 cycles of charging and discharging, the capacity retention rate is 87.6%, and the coulombic efficiency is 99.6%, which has a good cycle performance.

Example 3

Calcium silicide particles with a calcium content of 30% were placed in a ball milling tank, then absolute ethanol was added as a ball milling medium, and under the protection of an argon atmosphere, high-energy mechanical ball milling was performed at a speed of 400 rpm for 10 hours to obtain a calcium silicide slurry with a low particle size.

Add the obtained low particle size calcium silicide slurry into 5 mol/L sodium hydroxide aqueous solution, stir and react at 15°C for 35 hours, then filter and vacuum dry to obtain pretreated calcium silicide with a particle size of 2 μm. The mass ratio of sodium to calcium silicide particles is 1:1.

Place the pre-treated calcium silicide in a quartz tube furnace and heat it in an argon atmosphere. The flow rate of argon is controlled at 200scc min ^-1 , the rate of temperature rise after heating is controlled at 15°C min ^-1 , and heated to 1000°C After that, stop heating and keep warm, feed ethylene gas, and control the flow rate to 200scc min ^-1 , after 25 minutes, stop feeding ethylene gas, and cool the product to room temperature with the furnace to obtain chemical vapor deposition products, in which ethylene gas The volume-to-mass ratio of the pre-treatment calcium silicide is 5L:6g.

The chemical vapor deposition product was added to hydrochloric acid with a mass fraction of 10%, stirred and reacted at room temperature for 8 hours, then filtered, washed several times until neutral, and the product was dried to obtain a lithium ion battery negative electrode material, wherein hydrochloric acid and chemical vapor deposition The volume to mass ratio of the product is 150mL:5g.

The present invention tests the particle size D50 and specific surface area of the obtained lithium-ion battery negative electrode material, and the test results are: the median particle size D50 of the lithium-ion battery negative electrode material is 8 μm, and the specific surface area is 5.4 m ² /g.

In the present invention, the above lithium ion battery negative electrode material and binder (styrene-butadiene rubber (SBR): sodium carboxymethyl cellulose (CMC) = 3:7 mass ratio), conductive agent Super P according to the weight of 80:10:10 Mixing, adding an appropriate amount of water as a dispersant to make a slurry, and then evenly coating on the copper foil current collector, and vacuum drying, rolling, to prepare a negative electrode sheet; with metal lithium as the counter electrode, 1mol/L LiPF A mixed solvent of ₆ (EC:DMC=1:1 volume ratio) was used as the electrolyte, and a polypropylene microporous membrane (Celgard 2400) was used as the separator, and a simulated battery was assembled in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). The charge and discharge current density was 150mAg ^-1 , and the charge and discharge voltage range was 0.001-1.5V.

Experimental results show that the lithium-ion battery provided by the invention has a specific capacity of 1467mAh/g for the first discharge, and a coulombic efficiency of 79.5% for the first time; after 100 cycles of charging and discharging, the capacity retention rate is 80.3%, and the coulombic efficiency is 99.4%, which has a good performance. cycle performance.

Example 4

Calcium silicide particles with a calcium content of 30% were placed in a ball milling tank, then absolute ethanol was added as a ball milling medium, and under the protection of an argon atmosphere, high-energy mechanical ball milling was performed at a speed of 400 rpm for 8 hours to obtain a calcium silicide slurry with a low particle size.

Add the obtained low particle size calcium silicide slurry into 2 mol/L sodium hydroxide aqueous solution, stir and react at 25°C for 20 hours, then filter and vacuum dry to obtain pretreated calcium silicide with a particle size of 3 μm, in which the hydroxide The mass ratio of sodium to calcium silicide particles is 3:1.

Place the pre-treated calcium silicide in a quartz tube furnace and heat it in an argon atmosphere. The flow rate of argon is controlled at 200scc min ^-1 , the rate of temperature rise after heating is controlled at 10°C min ^-1 , and heated to 900°C After that, stop heating and keep warm, feed ethylene gas, and control the flow rate to 200scc min ^-1 , after 90min, stop feeding ethylene gas, cool the obtained product to room temperature with the furnace, and obtain chemical vapor deposition products, in which ethylene gas The volume-to-mass ratio of pre-treatment calcium silicide is 18L:8g.

The chemical vapor deposition product was added to hydrochloric acid with a mass fraction of 20%, stirred and reacted at room temperature for 4 hours, then filtered, washed several times to neutrality, and the product was dried to obtain a lithium ion battery negative electrode material, wherein hydrochloric acid and chemical vapor deposition The volume to mass ratio of the product is 200mL:12g.

The present invention tests the particle size D50 and specific surface area of the obtained lithium ion battery negative electrode material, and the test results are: the median particle size D50 of the lithium ion battery negative electrode material is 4 μm, and the specific surface area is 5.4 m ² /g.

In the present invention, the above lithium ion battery negative electrode material and binder (styrene-butadiene rubber (SBR): sodium carboxymethyl cellulose (CMC) = 3:7 mass ratio), conductive agent Super P according to the weight of 80:10:10 Mixing, adding an appropriate amount of water as a dispersant to make a slurry, and then evenly coating on the copper foil current collector, and vacuum drying, rolling, to prepare a negative electrode sheet; with metal lithium as the counter electrode, 1mol/L LiPF A mixed solvent of ₆ (EC:DMC=1:1 volume ratio) was used as the electrolyte, and a polypropylene microporous membrane (Celgard 2400) was used as the separator, and a simulated battery was assembled in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). The charge and discharge current density was 150mAg ^-1 , and the charge and discharge voltage range was 0.001-1.5V.

Experimental results show that the lithium-ion battery provided by the present invention has a specific capacity of 1326mAh/g for the first discharge, and a coulombic efficiency of 78.9% for the first time; after 100 cycles of charging and discharging, the capacity retention rate is 84.2%, and the coulombic efficiency is 99.7%. cycle performance.

Example 5

Calcium silicide particles with a calcium content of 30% were placed in a ball milling tank, then absolute ethanol was added as a ball milling medium, and under the protection of an argon atmosphere, high-energy mechanical ball milling was performed at a speed of 400 rpm for 8 hours to obtain a calcium silicide slurry with a low particle size.

Add the obtained low particle size calcium silicide slurry into 2 mol/L sodium hydroxide aqueous solution, stir and react at 25°C for 20 hours, then filter and vacuum dry to obtain pretreated calcium silicide with a particle size of 3 μm, in which the hydroxide The mass ratio of sodium to calcium silicide particles is 10:4.

Place the pre-treated calcium silicide in a quartz tube furnace and heat it in an argon atmosphere. The flow rate of argon is controlled at 200scc min ^-1 , the rate of temperature rise after heating is controlled at 10°C min ^-1 , and heated to 900°C After that, stop heating and keep warm, feed ethylene gas, and control the flow rate to 200scc min ^-1 , after 45min, stop feeding ethylene gas, and cool the product to room temperature with the furnace to obtain a chemical vapor deposition product, in which ethylene gas The volume-to-mass ratio of the pre-treated calcium silicide is 24L:8g.

The chemical vapor deposition product was added to hydrochloric acid with a mass fraction of 20%, stirred and reacted at room temperature for 4 hours, then filtered, washed several times to neutrality, and the product was dried to obtain a lithium ion battery negative electrode material, wherein hydrochloric acid and chemical vapor deposition The volume to mass ratio of the product is 250mL:10g.

The present invention tests the particle size D50 and specific surface area of the obtained lithium ion battery negative electrode material, and the test results are: the median particle size D50 of the lithium ion battery negative electrode material is 4 μm, and the specific surface area is 5.4 m ² /g.

In the present invention, the above lithium ion battery negative electrode material and binder (styrene-butadiene rubber (SBR): sodium carboxymethyl cellulose (CMC) = 3:7 mass ratio), conductive agent Super P according to the weight of 80:10:10 Mixing, adding an appropriate amount of water as a dispersant to make a slurry, and then evenly coating on the copper foil current collector, and vacuum drying, rolling, to prepare a negative electrode sheet; with metal lithium as the counter electrode, 1mol/L LiPF A mixed solvent of ₆ (EC:DMC=1:1 volume ratio) was used as the electrolyte, and a polypropylene microporous membrane (Celgard 2400) was used as the separator, and a simulated battery was assembled in an argon-protected glove box. The assembled simulated battery was subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd.). The charge and discharge current density was 150mAg ^-1 , and the charge and discharge voltage range was 0.001-1.5V.

Experimental results show that the lithium-ion battery provided by the present invention has a first discharge specific capacity of 1633mAh/g, and a first coulombic efficiency of 81.8%; after 100 cycles of charge and discharge, the capacity retention rate is 92.6%, and the coulombic efficiency is 99.9%, which has a good cycle performance.

Example 6

Calcium silicide particles with a calcium content of 30% were placed in a ball milling tank, then absolute ethanol was added as a ball milling medium, and under the protection of an argon atmosphere, high-energy mechanical ball milling was performed at a speed of 400 rpm for 6 hours to obtain a calcium silicide slurry with a low particle size.

Add the obtained low particle size calcium silicide slurry into 0.5 mol/L sodium hydroxide aqueous solution, stir and react at 35°C for 10 hours, then filter and vacuum dry to obtain pretreated calcium silicide with a particle size of 5 μm, in which hydrogen The mass ratio of sodium oxide to calcium silicide particles is 8:5.

Place the pre-treated calcium silicide in a quartz tube furnace and heat it in an argon atmosphere. The flow rate of argon is controlled at 200scc min ^-1 , the rate of temperature rise after heating is controlled at 7°C min ^-1 , and heated to 900°C After that, stop heating and keep warm, feed ethylene gas, and control the flow rate to 200scc min ^-1 , after 60min, stop feeding ethylene gas, cool the product to room temperature with the furnace, and obtain the chemical vapor deposition product, wherein the ethylene gas The volume-to-mass ratio of the pre-treated calcium silicide is 36L:4g.

The chemical vapor deposition product was added to hydrochloric acid with a mass fraction of 30%, stirred and reacted at room temperature for 2 hours, then filtered, washed several times to neutrality, and the product was dried to obtain a lithium ion battery negative electrode material, wherein hydrochloric acid and chemical vapor deposition The volume to mass ratio of the product is 200mL: 10g.

The present invention tests the particle size D50 and specific surface area of the obtained lithium ion battery negative electrode material, and the test results are: the median particle size D50 of the lithium ion battery negative electrode material is 8 μm, and the specific surface area is 3.2 m ² /g.

In the present invention, the above lithium ion battery negative electrode material and binder (styrene-butadiene rubber (SBR): sodium carboxymethyl cellulose (CMC) = 3:7 mass ratio), conductive agent Super P according to the weight of 80:10:10 Mixing, adding an appropriate amount of water as a dispersant to make a slurry, and then evenly coating on the copper foil current collector, and vacuum drying, rolling, to prepare a negative electrode sheet; with metal lithium as the counter electrode, 1mol/L LiPF A mixed solvent of ₆ (EC:DMC=1:1 volume ratio) was used as the electrolyte, and a polypropylene microporous membrane (Celgard 2400) was used as the separator, and a simulated battery was assembled in an argon-protected glove box. The assembled simulated battery is subjected to a constant current charge and discharge test on a Land tester (Wuhan Xinnuo Electronics Co., Ltd., please confirm with the inventor). The charge and discharge current density is 150mA g ^-1 , and the charge and discharge voltage range is 0.001 to 1.5 V.

Experimental results show that the lithium-ion battery provided by the invention has a specific capacity of 1358mAh/g for the first discharge, and a coulombic efficiency of 77.6% for the first time; after 100 cycles of charging and discharging, the capacity retention rate is 88.3%, and the coulombic efficiency is 99.8%. cycle performance.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. a preparation method of lithium ion battery negative electrode material, is characterized in that, comprises the following steps: A) Alkali treatment of calcium silicide to obtain pre-treated calcium silicide; B) heating the pre-treated calcium silicide, and passing gaseous hydrocarbon compounds to carry out chemical vapor deposition to obtain chemical vapor deposition products; C) Pickling the chemical vapor deposition product to obtain a lithium-ion battery negative electrode material; the acid solution used in the pickling treatment is selected from one or more of hydrochloric acid, nitric acid, hydrobromic acid and hydroiodic acid ; The negative electrode material of the lithium ion battery includes an inner core and a shell, and a hollow layer is included between the inner core and the shell; The outer shell is made of carbon material, and the inner core is made of porous silicon material; There is no carbon material attached to the surface of the inner hole wall of the inner core. 2 . The preparation method of lithium ion battery negative electrode material according to claim 1 , characterized in that, the particle diameter of the pre-treated calcium silicide is 500 nm˜10 μm. 3 . 3. The preparation method of lithium-ion battery negative electrode material according to claim 1, characterized in that, in step B), heating the pre-treated calcium silicide is specifically: placing the pre-treated calcium silicide in a high-temperature tubular In the furnace, heat in the presence of protective gas. 4 . The preparation method of the lithium ion battery negative electrode material according to claim 1 , characterized in that, the temperature of the chemical vapor deposition is 600° C. to 1000° C.; the time of the chemical vapor deposition is 10 min to 120 min. 5. The preparation method of lithium ion battery negative electrode material according to claim 1, characterized in that, the mass percentage of the acid solution is 5%-36%. 6 . The preparation method of lithium ion battery negative electrode material according to claim 1 , characterized in that, the thickness of the shell is 100 nm˜5 μm. 7 . 7 . The preparation method of lithium ion battery negative electrode material according to claim 1 , characterized in that, the particle diameter of the inner core is 500 nm to 10 μm, and the pore diameter of the inner core is 10 nm to 100 nm.