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WO2017050260A1 - 一种复合石墨的制备方法、复合石墨及锂离子电池 - Google Patents

一种复合石墨的制备方法、复合石墨及锂离子电池 Download PDF

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WO2017050260A1
WO2017050260A1 PCT/CN2016/099767 CN2016099767W WO2017050260A1 WO 2017050260 A1 WO2017050260 A1 WO 2017050260A1 CN 2016099767 W CN2016099767 W CN 2016099767W WO 2017050260 A1 WO2017050260 A1 WO 2017050260A1
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Prior art keywords
coke
carbon powder
weight
ultrafine carbon
graphite
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PCT/CN2016/099767
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English (en)
French (fr)
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周海辉
苗恒
潘修军
谯渭川
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深圳市贝特瑞新能源材料股份有限公司
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Publication of WO2017050260A1 publication Critical patent/WO2017050260A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a method for preparing composite graphite and composite graphite prepared by the method, and a lithium ion battery including the composite graphite.
  • the anode material has a significant impact on the performance of lithium-ion batteries.
  • new high-capacity anodes such as Si-based, Sn-based and Al-based have not been popularized due to their cost and technical factors, while traditional graphite-based anode materials Due to its stable performance, mature technology and low cost, it will continue to dominate the negative electrode market for a period of time.
  • the actual capacity of the graphite-based anode is close to the theoretical capacity, and further increasing the volume-to-weight energy density under the condition that the mass ratio is the same as the energy density is one of the possible improvement directions.
  • graphite particles undergo a layer spacing change and SEI film thickening during deintercalation of lithium, which in turn leads to expansion of the negative electrode tab, SEI film cracking or even active material peeling and membrane breakage, affecting cycle performance and safety performance.
  • the practice of preserving the expansion space of the pole piece in the battery design is mainly adopted, and the method cannot solve the problem of pole piece expansion fundamentally, and also limits the increase of energy density.
  • the patent CN1645653A proposes a method of combining sheet-like or flat-shaped coke-like particles into a spherical or spheroidal precursor by a binder, and then graphitizing to obtain composite secondary graphite particles, the secondary particles having macroscopic Isotropic.
  • the anisotropic graphite raw material is obtained by pulverization, classification and sieving to obtain ultrafine graphite powder with an average particle diameter of 2-10 ⁇ m, and then treated by secondary granulation technology to improve the isotropicity of graphite particles and graphite.
  • the end/base ratio of the particles to improve the material during the intercalation process Volume expansion and contraction effects and high current charge and discharge properties of materials.
  • the raw materials used in this scheme are artificial graphite or natural graphite.
  • the raw material cost is high, the bonding strength between graphite and binder is poor, and the ratio of binder required for compounding is high, which limits the further improvement of tap density and specific capacity, only from isotropy.
  • the angle improves the lithium insertion rate and the rate performance is limited.
  • Patent CN103855369A heats and stirs a mixture of carbon powder, binder and catalyst, press molding, carbonization and graphitization.
  • the solution has the problems of low specific capacity, low initial effect and low compaction density.
  • Patent CN103682347A mixes the optimized proportion of needle coke, isotropic coke and natural graphite uniformly, and puts the mixture material into the graphitization furnace for graphitization and purification treatment, and finally obtains the negative electrode material of lithium ion secondary battery, further after graphitization
  • the powder is shaped, classified, and sieved to obtain a composite lithium ion battery anode material.
  • the graphite particles prepared by the method have limited performance improvement and cannot improve the orientation.
  • the object of the present invention is to provide a method for preparing composite graphite.
  • the composite graphite prepared by the method has high energy density, good liquid absorption and liquid retention performance, good isotropic performance, and large magnification charging and discharging. Good performance, low expansion rate during charging and discharging.
  • a method for preparing composite graphite which comprises the following steps:
  • the ultrafine carbon powder comprises green coke and/or mesocarbon microspheres
  • the present invention also provides a composite graphite prepared by the above method.
  • the present invention also provides a lithium ion battery comprising a positive electrode, a separator and a negative electrode which are sequentially stacked; the negative electrode includes a negative electrode current collector and a negative electrode material on the negative electrode current collector, the negative electrode material including as before The composite graphite.
  • the raw material used contains raw coke and/or mesocarbon microspheres, and the raw coke or mesocarbon microspheres are fully utilized to reduce the binder usage. It is beneficial to reduce costs, increase tapping, compaction density and specific capacity. And adding a catalyst to the coke and When the composite treatment is carried out, the catalyst can partially enter the inside of the coke particles, the catalysis is more uniform, and the catalyst utilization rate is higher.
  • the invention realizes the secondary granulation of the ultrafine carbon powder by mixing the ultrafine carbon powder and the binder, thereby facilitating the improvement of the isotropic performance, the improvement of the rate performance and the reduction of the pole piece expansion ratio.
  • the secondary granulation of superfine carbon powder and the addition of catalyst increase the porosity, improve the liquid absorption and liquid retention performance, and improve the charge and discharge performance of large magnification; the post-treatment adopts the spheroidization and coating process to make up for the secondary particle tapping,
  • the shortcoming of the first effect is low.
  • the present invention combines isotropic particles with anisotropic particles to provide more lithium ion insertion channels and to ensure the specific capacity and compaction of the finished product.
  • the composite graphite prepared by the method disclosed by the invention has a first specific capacity of more than 360 mAg/g, a first efficiency of more than 95%, and a pole piece compaction density of more than 1.75 g/cc. Its outstanding features are high porosity, good liquid retention and liquid retention, good isotropic performance, good charge and discharge performance at large rate, and low expansion rate during charge and discharge. It is of positive significance for lithium batteries to further increase energy density and shorten charging time.
  • FIG. 1 is a graph showing the rate performance test of a lithium ion battery prepared by using the composite graphite prepared in Examples 1-6 and Comparative Examples 1-2 of the present invention
  • Example 2 is an SEM image of the composite graphite prepared in Example 6 provided by the present invention.
  • the preparation method of the composite graphite provided by the invention comprises the following steps:
  • the ultrafine carbon powder comprises green coke and/or mesocarbon microspheres
  • the above ultrafine carbon powder contains at least coke and/or mesocarbon microspheres.
  • the raw coke may be one or more of needle coke focus, pitch coke coke, and homogenous coke coke.
  • the coke viscosity can be fully utilized, the amount of binder can be reduced, and the cost can be reduced. Improve tapping, compaction density and specific capacity.
  • the ultrafine carbon powder may include various carbon materials, for example, one or more of needle coke, pitch coke, isotropic coke, natural graphite, artificial graphite, and mesocarbon microbeads. .
  • the needle coke is needle coke and/or needle coke; the pitch coke is pitch coke and/or pitch coke; the homologous coke is isotropic coke and/or isotropic coke Cooked coke.
  • the volatile matter of the above various green cokes is 5 to 40%. If the above various cooked cokes are used, the volatile content is less than 5%. Further preferably, the needle coke, the pitch coke, and the homologous coke used in the ultrafine carbon powder are both coke and have a volatile content of 5-20%.
  • the ash content is less than 0.5%.
  • the crystallinity is less than 30%.
  • the ultrafine carbon powder necessarily contains other kinds of green coke or mesocarbon microspheres.
  • the pitch coke is pitch coke or the same coke is coke.
  • the ultrafine carbon powder if there is no mesocarbon microbeads in the ultrafine carbon powder, at least one of the above cokes is inevitably contained.
  • the ultrafine carbon powder includes one or more of natural graphite, needle coke, isotropic coke, and mesocarbon microbeads.
  • the natural graphite content is 70% by weight or less
  • the needle coke content is 70% by weight or less
  • the isotropic coke content is 30% by weight or less
  • the mesophase carbon microspheres have a green ball content of 70% by weight or less.
  • the above natural graphite contains 0 to 10% by weight of microcrystalline graphite based on the total weight of the ultrafine carbon powder.
  • the same-focus coke provides more lithium-ion insertion channels, but its capacity is lower.
  • Mesophase carbon microspheres provide more lithium ion intercalation channels with high capacity but higher cost.
  • the needle coke has a high capacity and good circulation, but its rate performance is poor.
  • Natural graphite increases capacity and compaction density, but its rate performance and cycle performance are poor.
  • isotropic particles for example, homo- or co-phase carbon microspheres
  • anisotropic particles for example, natural graphite or needle coke
  • the sum of the weight of the natural graphite and the needle coke focus is 70 to 90% by weight, and the isotropic coke content is 10 to 30% by weight.
  • the sum of the mesophase carbon microspheres and the natural graphite weight is greater than 50% by weight, the isotropic coke content is less than 20% by weight, and the isotropic coke and/or needle coke content is less than 30% by weight.
  • the ratio of the total weight of the green coke to the mesophase carbon microspheres is 50-70 wt%, the ratio of natural graphite is 30-50 wt%, and the ratio of cooked coke is less than 20%.
  • the ratio of the mesophase carbon microspheres to the total weight of the ultrafine carbon powder is more than 30% by weight.
  • the ultrafine carbon powder has a D 50 of from 2 to 10 ⁇ m, more preferably from 7 to 8 ⁇ m.
  • the above ultrafine carbon powder can be directly obtained by purchasing various raw material powders satisfying the above conditions and obtained by mixing. It can also be prepared by using a conventional raw material, for example, obtaining various raw materials of a desired ratio, and then mixing, pulverizing, classifying, sieving, and spheroidizing to obtain an ultrafine carbon powder. According to the actual situation, it is preferable that the ultrafine carbon powder obtained after spheroidization has a D 50 of 2 to 10 ⁇ m.
  • step S2 After obtaining the above ultrafine carbon powder as described in step S2, it further comprises mixing the ultrafine carbon powder with a binder to obtain a mixture A, and the mixture A and the catalyst are mixed to obtain a mixture B.
  • the above binder may be any of various binders conventionally known in the art, and for example, one or more of medium-low temperature asphalt, phenol resin, epoxy resin, polyester resin or polyamide resin may be specifically used. As is known to those skilled in the art, when the above binder is used, it may be dissolved by an organic solvent and then mixed according to a specific case.
  • the above binder is a medium-low temperature asphalt.
  • the medium-low temperature asphalt may be coal-based or oil-based pitch. More preferably, the medium-low temperature asphalt has a softening point of 50 to 100 °C.
  • the ultrafine carbon powder contains coke and/or mesocarbon microspheres, it is only necessary to use a relatively small amount of binder to prepare a product composite graphite having excellent properties.
  • the ratio of the binder content to the ultrafine carbon powder is less than 20% by weight.
  • the catalyst may be a conventional catalyst, for example, one or more selected from the group consisting of silicon, a silicon compound, iron, an iron compound, boron, and a boron compound.
  • the ratio of the catalyst content to the ultrafine carbon powder is less than 30% by weight.
  • the catalyst is a silicon compound.
  • the ratio of the catalyst content to the ultrafine carbon powder is 5 to 20% by weight.
  • the above ultrafine carbon powder contains coke and/or mesocarbon microspheres, and after the catalyst is added and combined, the catalyst can partially enter the inside of the coke particles, and the catalytic effect is more uniform.
  • the catalyst utilization rate is higher.
  • the amount of catalyst used can be reduced and the cost can be reduced.
  • the mixture B is subjected to a composite treatment to obtain a precursor.
  • the composite treatment may adopt various existing composite treatment methods, for example, one selected from the group consisting of solid phase kneading, liquid phase kneading, sheet rolling, fusion, spray drying, molding, isostatic pressing, and carbonization. A variety.
  • the composite treatment may include first performing liquid phase kneading and then molding. More preferably, the mixture B is first subjected to liquid phase kneading, followed by rolling, molding, isostatic pressing, and carbonization to obtain the precursor.
  • liquid phase kneading it is preferably at a temperature of from 100 to 300 ° C for a period of from 1 to 2 h.
  • the binder is a medium-low temperature asphalt
  • the liquid phase kneading temperature is 50-90 ° C higher than the softening point of the medium-low temperature asphalt.
  • the invention combines the ultrafine carbon powder with the binder and then combines the treatment, the secondary granulation of the ultrafine carbon powder is realized, which is advantageous for improving the isotropic performance, and is advantageous for improving the rate performance and reducing the expansion rate of the pole piece.
  • the secondary granulation of superfine carbon powder and the addition of catalyst increase the porosity, improve the liquid absorption and liquid retention performance, and improve the charge and discharge performance of large magnification; the post-treatment adopts the spheroidization and coating process to make up for the secondary particle tapping,
  • the shortcoming of the first effect is low.
  • the precursor is subjected to graphitization to obtain a semi-finished product.
  • the above described methods of graphitization are well known in the art.
  • the temperature of the graphitization treatment is 2700 to 3200 °C.
  • step S4 the semi-finished product is pulverized, spheroidized, coated, and sieved to obtain the composite graphite.
  • the semi-finished product can be mechanically pulverized, ball milled, and then spheroidized.
  • the above coating treatment may specifically be one of conventional liquid phase, solid phase coating or mechanical fusion.
  • the coating material used in the coating treatment is selected from one or more of asphalt, resin, and conductive graphite.
  • the coating material is medium-low temperature asphalt and conductive graphite, or resin and medium-low temperature asphalt.
  • the coating treatment is a liquid phase coating
  • a carbonization treatment is further included before the sieving treatment after the liquid phase coating.
  • the above carbonization treatment temperature is preferably from 600 to 1500 °C.
  • the sieve particle size D 50 is preferably from 4 to 30 ⁇ m.
  • the post-treatment of the invention adopts the spheroidization and coating process to make up for the shortcomings of secondary particle tapping and low first effect.
  • the present invention also provides a composite graphite prepared by the above method.
  • the present invention also provides a lithium ion battery comprising a positive electrode, a separator and a negative electrode which are sequentially stacked; the negative electrode includes a negative electrode current collector and a negative electrode material on the negative electrode current collector, the negative electrode material including as before The composite graphite.
  • the materials, structures and preparation methods of the lithium ion battery can adopt various methods in the prior art, and the present invention will not be described again.
  • This embodiment is for explaining the preparation method of the composite graphite disclosed in the present invention.
  • Step 1 Mixing the same-focus coke and coke-like coke raw materials, respectively, using mechanical pulverization and jet pulverization to a D 50 of 4-5 ⁇ m to obtain ultrafine carbon powder.
  • a dry powder: low temperature Asphalt 100:20 was added to the molten low-temperature asphalt, and after kneading for 1 hour, it was taken out and subjected to press molding to obtain a precursor.
  • Step 3 The block precursor obtained in the step 2 is graphitized to obtain a semi-finished product.
  • Step 4 The semi-finished product obtained in the step 3 is sequentially mechanically crushed and sieved to obtain a composite graphite product having a D 50 of 12-13 ⁇ m.
  • This embodiment is for explaining the preparation method of the composite graphite disclosed in the present invention.
  • Step 1 Mixing the same-focus coke, needle coke and needle coke raw materials, respectively, using mechanical pulverization and jet pulverization to a D 50 of 4-5 ⁇ m to obtain ultrafine carbon powder.
  • Step 3 The block precursor obtained in the step 2 is graphitized to obtain a semi-finished product.
  • Step 4 The semi-finished product obtained in the step 3 is sequentially mechanically crushed and sieved to obtain a composite graphite product having a D 50 of 12-13 ⁇ m.
  • This embodiment is for explaining the preparation method of the composite graphite disclosed in the present invention.
  • Step 1 Mixing the same-focus coke and coke-like coke raw materials, respectively, using mechanical pulverization and airflow pulverization to a D 50 of 4-5 ⁇ m to obtain ultrafine carbon powder.
  • Step 3 The block precursor obtained in the step 2 is graphitized to obtain a semi-finished product.
  • Step 4 The semi-finished product obtained in the step 3 is sequentially mechanically crushed and sieved to obtain a composite graphite product having a D 50 of 12-13 ⁇ m.
  • This embodiment is for explaining the preparation method of the composite graphite disclosed in the present invention.
  • Step 1 Mixing the homogenous coke coke and the needle coke cooked coke raw material, and using mechanical pulverization and jet pulverization to a D 50 of 4-5 ⁇ m to obtain an ultrafine carbon powder.
  • a dry powder: low temperature Asphalt 100:20 was added to the molten low-temperature pitch, kneaded for 2 hours, and then taken out for rolling, pulverization, and compression molding to obtain a precursor.
  • Step 3 The block precursor obtained in the step 2 is graphitized, and the graphitization temperature is 3000 ° C for 14 d to obtain a semi-finished product.
  • Step 4 The semi-finished product obtained in the step 3 is mechanically crushed, spheroidized, and sieved to obtain a composite graphite product having a D 50 of 12-13 ⁇ m.
  • This embodiment is for explaining the preparation method of the composite graphite disclosed in the present invention.
  • Step 1 Mixing needle coke, coke coke and natural graphite raw materials, and mechanically pulverizing and jet milling to a D 50 of 7-8 ⁇ m to obtain ultrafine carbon powder.
  • Step 3 The block precursor obtained in the step 2 is graphitized, and the graphitization temperature is 3000 ° C for 14 d to obtain a semi-finished product.
  • Step 4 The semi-finished product obtained in the step 3 is sequentially mechanically crushed, spheroidized, sieved, and the composite graphite having a D 50 of 12-13 ⁇ m is finished.
  • This embodiment is for explaining the preparation method of the composite graphite disclosed in the present invention.
  • Step 1 The needle coke coke, the mesophase carbon microsphere green ball and the natural graphite raw material are mixed, and mechanically pulverized and air jet pulverized to a D 50 of 7-8 ⁇ m to obtain an ultrafine carbon powder.
  • Step 3 The block precursor obtained in the step 2 is graphitized, and the graphitization temperature is 3000 ° C for 14 d to obtain a semi-finished product.
  • Step 4 The semi-finished product obtained in the step 3 is mechanically crushed, spheroidized, coated with solid phase asphalt, coated with 1.5%, carbonized at 1100 ° C, and sieved to obtain a composite graphite product having a D 50 of 12-13 ⁇ m.
  • the obtained physical and chemical indicators are shown in Table 1.
  • the rate performance is shown in Figure 1.
  • the SEM morphology is shown in Figure 2.
  • This comparative example is used to compare and explain the preparation method of the composite graphite disclosed in the present invention.
  • Step 1 Mixing the same-focus coke and coke-like coke raw materials, respectively, using mechanical pulverization and jet pulverization to a D 50 of 4-5 ⁇ m to obtain ultrafine carbon powder.
  • a dry powder: low temperature asphalt 100: 40 was added to melt low-temperature asphalt, kneaded for 1 hour, and then taken out for press molding to obtain a precursor.
  • Step 3 The block precursor obtained in the step 2 is graphitized to obtain a semi-finished product.
  • Step 4 The semi-finished product obtained in the step 3 is sequentially mechanically crushed and sieved to obtain a composite graphite product having a D 50 of 12-13 ⁇ m.
  • This comparative example is used to compare and explain the preparation method of the composite graphite disclosed in the present invention.
  • Step 3 The block precursor obtained in the step 2 is graphitized, and the graphitization temperature is 3000 ° C for 14 d to obtain a semi-finished product.
  • Step 4 The semi-finished product obtained in the step 3 is sequentially mechanically crushed and sieved to obtain a composite graphite product having a D 50 of 12-13 ⁇ m.
  • the composite graphite prepared in the above Examples 1-6 and Comparative Example 1-2 was observed by Hitachi S4800 scanning electron microscope to observe the surface morphology and particle size of the sample; X-ray diffractometer X'Pert Pro, PANalytical test material was used. Graphitization and degree of anisotropy; the specific surface area of the material was tested using the Tristar 3000 fully automatic surface area and porosity analyzer from Mike Instruments. The particle size range of the material and the average particle size of the raw material particles were measured using a Malvern laser particle size tester MS 2000. The tap density of the material was tested using a Quantachrome AutoTap tap density meter.
  • the composite graphite prepared in the above Examples 1-6 and Comparative Example 1-2, CMC (solid content: 1.2%), and binder SBR (solid content: 50%) were respectively mixed at a mass ratio of 96.5:1.5:2.
  • the slurry was then uniformly coated on a 11 ⁇ m thick copper foil and dried to obtain an areal density of 70 g/m 2 , and a pole piece of 1.75 g/cm 3 was compacted and then punched into a circular pole piece having a diameter of 16 mm and dried in a vacuum. Dry in a box at 120 ° C for 10 hours.
  • the pole piece prepared above was used as the working electrode, the lithium piece was used as the counter electrode, and the electrolyte was made of EC/DMC/EMC (volume ratio of 1:1:1) of 1 mol/L LiPF 6 in the German Braun glove box.
  • the two-electrode electrolytic cell was assembled and subjected to constant current charge and discharge at a current density of 0.1 C.
  • the voltage range was from 0.001 V to 2.5 V, and the first delithiation capacity of the material and the first coulombic efficiency were measured.
  • the pole piece prepared above was used as the working electrode, the lithium cobaltate positive electrode was used as the counter electrode, and the electrolyte was made of 1 mol/L LiPF 6 EC/DMC/EMC (volume ratio: 1:1), in Braun, Germany.
  • the electrode displacement measuring cell is assembled in the glove box.
  • the above battery is subjected to constant current charge and discharge at a current density of 0.1 C, and the voltage range is from 0.001 V to 2.5 V.
  • the second cycle starts with a constant current charge and discharge cycle at a current density of 0.5 C. After 20 cycles, the battery is directly measured by electrode displacement. Readings, calculate the expansion rate before and after the pole piece cycle.

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Abstract

一种复合石墨的制备方法以及通过该方法制备得到的复合石墨以及锂离子电池，该方法包括如下步骤：S1、提供超细碳粉；所述超细碳粉包括生焦和/或中间相碳微球生球；S2、将超细碳粉与粘结剂混合，得到混合物A，混合物A和催化剂混合，得到混合物B，然后对混合物B进行复合处理，得到前驱体；S3、对前驱体进行石墨化处理，得到半成品；S4、对半成品进行粉碎、球形化、包覆、筛分，得到所述复合石墨。该方法克服了现有技术中的方法制备得到的复合石墨具有能量密度低、大倍率充放性能差、充放电过程中膨胀率高的问题，通过该方法制备得到的复合石墨能量密度高、吸液保液性能好、各向同性性能好、大倍率充放性能好、充放电过程中膨胀率低。

Description

一种复合石墨的制备方法、复合石墨及锂离子电池 技术领域
本发明涉及一种复合石墨的制备方法和通过该方法制备得到的复合石墨，以及包括该复合石墨的锂离子电池。
背景技术
近年来随移动通讯及便携电子设备的发展，对提供能源的锂离子电池性能提出了更高的要求。负极材料对锂离子电池性能有重大影响，在已有负极材料中Si基、Sn基和Al基等新型高容量负极因其成本和技术因素迟迟得不到推广应用，而传统石墨类负极材料因其性能稳定、技术成熟、成本低等特点将在一段时间内继续主导负极市场。
目前石墨类负极实际容量已经接近理论容量，在质量比能量密度不变的情况下进一步提高体积比能量密度，是可能的改进方向之一。众所周知石墨颗粒在脱嵌锂过程中会发生层间距改变和SEI膜增厚，进而导致负极极片膨胀、SEI膜破裂甚至活性物质剥离和隔膜断裂，影响循环性能和安全性能。为了预防负极极片膨胀导致的电池性能恶化，目前主要采用在电池设计中预留极片膨胀空间的做法，该方法无法从根本解决极片膨胀问题，也限制了能量密度的提升。
以苹果手机为代表的新一代数码通讯设备发展，使石墨负极充电速度慢的问题日益成为影响用户体验的严重问题。
为了解决上述问题，专利CN1645653A提出了将片状或平板状焦类颗粒通过粘结剂组合成具有球形或类球形前驱体，进而石墨化得到复合二次石墨颗粒的方法，该二次颗粒具有宏观各向同性。
在实际生产中，焦类颗粒与粘结剂结合性差，成品球形度较低，在石墨化后的破碎及球化工艺中易发生破裂粉碎，重新变为各向异性的片状或平板状石墨颗粒。
专利CN103811758A将各向异性石墨原材料通过粉碎、分级、筛分处理得到平均粒径为2-10μm的超细石墨粉后，再通过二次造粒技术处理，来提高石墨颗粒的各向同性及石墨颗粒的端面/基面比例，从而来改善材料在嵌脱锂过程中 体积膨胀收缩效应及材料的大电流充放电性能。
该方案所用原料为人造石墨或天然石墨，原料成本高，石墨与粘结剂结合力差，复合所需粘结剂比例高，限制了振实密度和比容量的进一步提高，仅从各向同性角度改善嵌锂速率，倍率性能提高有限。
专利CN103855369A将炭粉、粘结剂和催化剂的混合物加热搅拌，压制成型，炭化，石墨化即可。
该方案存在成品比容量低，首效低、压实密度低的问题。
专利CN103682347A将优化比例的针状焦、同性焦、天然石墨进行混合均匀，将混合物物料置于石墨化炉中进行石墨化纯化处理，最终制得锂离子二次电池负极材料，进一步对石墨化后的粉料进行整形、分级、筛分，得到复合锂离子电池负极材料。
该方法制备得到的石墨颗粒的性能提高有限，且无法改善取向性。
发明内容
针对现有技术的不足，本发明的目的在于提供一种复合石墨的制备方法，该方法制备得到的复合石墨具有能量密度高、吸液保液性能好、各向同性性能好、大倍率充放性能好、充放电过程中膨胀率低的特点。
本发明解决上述技术问题所采用的技术方案如下：
提供一种复合石墨的制备方法，其特征在于，包括如下步骤：
S1、提供超细碳粉；所述超细碳粉包括生焦和/或中间相碳微球生球；
S2、将超细碳粉与粘结剂混合，得到混合物A，混合物A和催化剂混合，得到混合物B，然后对混合物B进行复合处理，得到前驱体；
S3、对前驱体进行石墨化处理，得到半成品；
S4、对半成品进行粉碎、球形化、包覆、筛分，得到所述复合石墨。
同时，本发明还提供了一种通过上述方法制备得到的复合石墨。
另外，本发明还提供了一种锂离子电池，包括依次叠置的正极、隔膜和负极；所述负极包括负极集流体以及位于所述负极集流体上的负极材料，所述负极材料包括如前所述的复合石墨。
本发明提供的复合石墨的制备方法中，采用的原料中含有生焦和/或中间相碳微球生球，充分利用生焦或中间相碳微球生球黏性，降低粘结剂使用量，有利于降低成本、提高振实、压实密度和比容量。并且，在生焦中加入催化剂并 进行复合处理，催化剂可以部分进入生焦颗粒内部，催化作用更加均匀、催化剂利用率更高。
同时，本发明通过将超细碳粉与粘结剂混合后复合处理，实现超细碳粉二次造粒，有利于提高各向同性性能，有利于提高倍率性能和降低极片膨胀率。
超细碳粉二次造粒和催化剂的加入，提高了孔隙率，改善吸液保液性能、提高大倍率充放电性能；后处理采用球形化及包覆工艺，弥补了二次颗粒振实、首效偏低的缺点。
另外，本发明将各向同性颗粒与各向异性颗粒复合，既提供更多锂离子嵌入通道，又保证了成品的比容量、压实。
本发明公开的方法制备得到的复合石墨首次比容量大于360mAg/g，首次效率大于95％，极片压实密度大于1.75g/cc。其突出特点为孔隙率较高、吸液保液性能好、各向同性性能好、大倍率充放性能好、充放电过程中膨胀率低。对锂电池进一步提高能量密度、缩短充电时间有积极意义。
附图说明
图1是分别采用本发明实施例1-6及对比例1-2制备得到的复合石墨制备得到的锂离子电池的倍率性能测试图；
图2是本发明提供的实施例6制备得到的复合石墨的SEM图。
具体实施方式
为了使本发明所解决的技术问题、技术方案及有益效果更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明提供的复合石墨的制备方法包括如下步骤：
S1、提供超细碳粉；所述超细碳粉包括生焦和/或中间相碳微球生球；
S2、将超细碳粉与粘结剂混合，得到混合物A，混合物A和催化剂混合，得到混合物B，然后对混合物B进行复合处理，得到前驱体；
S3、对前驱体进行石墨化处理，得到半成品；
S4、对半成品进行粉碎、球形化、包覆、筛分，得到所述复合石墨。
根据本发明，上述超细碳粉中至少含有生焦和/或中间相碳微球生球。其中，生焦可采用针状焦生焦、沥青焦生焦、同性焦生焦中的一种或多种。
本发明中，通过在含有生焦和/或中间相碳微球生球的超细碳粉基础上制备复合石墨，可充分利用生焦黏性，降低粘结剂使用量，有利于降低成本、提高振实、压实密度和比容量。
具体的，上述超细碳粉可包括各种碳素材料，例如具体可以包括针状焦、沥青焦、同性焦、天然石墨、人造石墨、中间相碳微球生球中的一种或多种。
上述针状焦为针状焦生焦和/或针状焦熟焦；所述沥青焦为沥青焦生焦和/或沥青焦熟焦；所述同性焦为同性焦生焦和/或同性焦熟焦。
本发明中，优选情况下，上述各种生焦的挥发份为5-40％。若采用上述各种熟焦，其挥发份小于5％。进一步优选情况下，上述超细碳粉中采用的针状焦、沥青焦、同性焦均为生焦，其挥发份为5-20％。
对于上述针状焦，优选其灰分小于0.5％。对于上述同性焦，优选其结晶度小于30％。
可以理解的，当上述针状焦为针状焦熟焦时，超细碳粉中必然含有其他种类的生焦或者中间相碳微球生球。同样的情况适用于沥青焦为沥青焦熟焦或者同性焦为同性焦熟焦的情形。相反，若超细碳粉中无中间相碳微球生球时，则必然含有上述生焦中的至少一种。
本发明中，优选情况下，上述超细碳粉包括天然石墨、针状焦、同性焦、中间相碳微球生球中的一种或多种。进一步优选情况下，按质量比，天然石墨含量为70wt％以下，针状焦含量为70wt％以下，同性焦含量为30wt％以下，中间相碳微球生球含量为70wt％以下。更优选情况下，上述天然石墨中含有占超细碳粉总重量0-10wt％的微晶石墨。
同性焦可提供更多锂离子嵌入通道，但其容量偏低。中间相碳微球可提供更多锂离子嵌入通道，容量高，但其成本较高。针状焦的容量高、循环好，但其倍率性能较差。而天然石墨可提高容量和压实密度，但其倍率性能和循环性能较差。
本发明中通过将上述多种原料配合使用，各向同性颗粒(例如同性焦或中间相碳微球生球)与各向异性颗粒(例如天然石墨或针状焦)复合，既提供更多锂离子嵌入通道，又保证了成品的比容量、压实，且具有优异的循环性能和倍率性能。
根据本发明，优选情况下，上述超细碳粉中，天然石墨与针状焦生焦重量之和为70-90wt％，同性焦生焦含量为10-30wt％。
或者，中间相碳微球生球与天然石墨重量之和大于50wt％，同性焦生焦含量小于20wt％，同性焦熟焦和/或针状焦含量小于30wt％。
更优选的，生焦与中间相碳微球生球总重量所占比例为50-70wt％，天然石墨比例为30-50wt％，熟焦比例小于20％。其中，中间相碳微球生球比例占超细碳粉总重量的比例大于30wt％。
根据本发明，优选情况下，上述超细碳粉的D50为2-10μm，进一步优选为7-8μm。
本发明中，上述超细碳粉可直接购买符合上述条件的各种原料粉末，经混合后得到。也可以采用常规原料制备得到，例如，获取所需配比的各种原料，然后混合，经粉碎、分级、筛分、球形化，得到超细碳粉。根据实际情况，优选情况下，球形化后得到的超细碳粉的D50为2-10μm。
上述粉碎、分级、筛分、球形化的具体工艺步骤和方法为本领域所公知的，本发明中不再赘述。
如步骤S2所述，获得上述超细碳粉后，还包括将超细碳粉与粘结剂混合，得到混合物A，混合物A和催化剂混合，得到混合物B。
上述粘结剂可采用现有技术中所常规的各种粘结剂，例如，具体可以采用中低温沥青、酚醛树脂、环氧树脂、聚酯树脂或聚酰胺树脂中的一种或多种。如本领域技术人员所知晓的，当上述粘结剂在使用时，可根据具体情况，先采用有机溶剂溶解，然后再进行混合。
本发明中，优选情况下，上述粘结剂采用中低温沥青。上述中低温沥青可采用煤系或者油系沥青。更优选情况下，所述中低温沥青的软化点为50-100℃。
根据本发明，如前所述，由于超细碳粉中含有生焦和/或中间相碳微球生球，只需采用较少含量的粘结剂即可制备得到性能优良的产品复合石墨。优选情况下，所述混合物B中，粘结剂含量占超细碳粉的比例小于20wt％。
上述混合物B中，催化剂可采用常规的各种催化剂，例如，可以选自硅、硅化合物、铁、铁化合物、硼、硼化合物中的一种或多种。所述混合物B中，催化剂含量占超细碳粉的比例小于30wt％。
本发明中，优选情况下，所述催化剂为硅化合物。所述混合物B中，催化剂含量占超细碳粉的比例为5-20wt％。
如前所述，上述超细碳粉中含有生焦和/或中间相碳微球生球，加入催化剂并进行复合处理后，催化剂可以部分进入生焦颗粒内部，催化作用更加均匀、 催化剂利用率更高。另一方面也可减少催化剂的使用量，降低成本。
根据本发明，获得上述混合物B后，需对混合物B进行复合处理，得到前驱体。
具体的，所述复合处理可以采用现有的各种复合处理方法，例如可选自固相混捏、液相混捏、轧片、融合、喷雾干燥、模压、等静压、碳化中的一种或多种。
本发明中，优选情况下，复合处理可以包括先进行液相混捏，然后再模压。更优选为，先对混合物B进行液相混捏，然后进行轧片、模压、等静压、碳化处理，得到上述前驱体。
对于上述液相混捏，优选情况下，其温度为100-300℃，时间为1-2h。当粘结剂采用中低温沥青时，更优选为液相混捏温度比中低温沥青软化点高50-90℃。
由于本发明通过将超细碳粉与粘结剂混合后复合处理，实现超细碳粉二次造粒，有利于提高各向同性性能，有利于提高倍率性能和降低极片膨胀率。
超细碳粉二次造粒和催化剂的加入，提高了孔隙率，改善吸液保液性能、提高大倍率充放电性能；后处理采用球形化及包覆工艺，弥补了二次颗粒振实、首效偏低的缺点。
根据本发明，如步骤S3，需对前驱体进行石墨化处理，得到半成品。上述石墨化的工艺方法为本领域所公知的。本发明中，优选情况下，所述石墨化处理的温度为2700-3200℃。
通过上述石墨化处理，即可得到本成品。最后，如步骤S4，对半成品进行粉碎、球形化、包覆、筛分，得到所述复合石墨。
具体的，可先对半成品进行机械粉碎、球磨，然后再球形化。
上述包覆处理具体可以采用常规的液相、固相包覆或机械融合中的一种。所述包覆处理所采用的包覆材料选自沥青、树脂、导电石墨中的一种或多种。优选情况下，上述包覆材料为中低温沥青和导电石墨，或者树脂和中低温沥青。
根据本发明，优选情况下，所述包覆处理为液相包覆，在所述液相包覆之后筛分处理之前还包括碳化处理。
上述碳化处理温度优选为600-1500℃。所述筛分粒度D50优选为4-30μm。
本发明后处理采用球形化及包覆工艺，弥补了二次颗粒振实、首效偏低的缺点。
同时，本发明还提供了通过上述方法制备得到的复合石墨。
另外，本发明还提供了一种锂离子电池，包括依次叠置的正极、隔膜和负极；所述负极包括负极集流体以及位于所述负极集流体上的负极材料，所述负极材料包括如前所述的复合石墨。
锂离子电池的材料、结构及制备方法可采用现有技术中的各种方法，本发明不再赘述。
以下通过实施例对本发明进行进一步的说明。
实施例1
本实施例用于说明本发明公开的复合石墨的制备方法。
步骤1、将同性焦生焦和针状焦熟焦原料混合，分别采用机械粉碎和气流粉碎至D50为4-5μm，得到超细碳粉。
步骤2、将步骤1所得超细碳粉，按照同性焦生焦∶针状焦熟焦∶三氧化二铁＝30∶70∶15比例加入混捏机，加热至200℃，按照混合物A干粉∶低温沥青＝100∶20加入熔化低温沥青，混捏1h后，取出进行模压成型，得到前驱体。
步骤3、将步骤2所得块状前驱体，进行石墨化，得到半成品。
步骤4、将步骤3所得半成品依次进行机械破碎，筛分，得到D50为12-13μm的复合石墨成品。
所得物化指标见表1，倍率性能见图1。
实施例2
本实施例用于说明本发明公开的复合石墨的制备方法。
步骤1、将同性焦生焦、针状焦生焦和针状焦熟焦原料混合，分别采用机械粉碎和气流粉碎至D50为4-5μm，得到超细碳粉。
步骤2、将步骤1所得超细碳粉，按照同性焦生焦∶针状焦生焦∶针状焦熟焦∶三氧化二硼＝30∶40∶30∶15比例加入混捏机，加热至200℃，按照混合物A干粉∶低温沥青＝100∶10加入熔化低温沥青，进行混捏1h后，取出进行模压成型，得到前驱体。
步骤3、将步骤2所得块状前驱体，进行石墨化，得到半成品。
步骤4、将步骤3所得半成品依次进行机械破碎，筛分，得到D50为12-13μm的复合石墨成品。
所得物化指标见表1，倍率性能见图1。
实施例3
本实施例用于说明本发明公开的复合石墨的制备方法。
步骤1、将同性焦生焦和针状焦生焦原料混合，分别采用机械粉碎和气流粉碎至D50为4-5μm，得到超细碳粉
步骤2、将步骤1所得超细碳粉，按照同性焦生焦∶针状焦生焦∶三氧化二硼＝30∶70∶15比例加入混捏机，加热至200℃，不加粘结剂，进行混捏1h后，取出进行模压成型，得到前驱体。
步骤3、将步骤2所得块状前驱体，进行石墨化，得到半成品。
步骤4、将步骤3所得半成品依次进行机械破碎，筛分，得到D50为12-13μm的复合石墨成品。
所得物化指标见表1，倍率性能见图1
实施例4
本实施例用于说明本发明公开的复合石墨的制备方法。
步骤1、将同性焦生焦和针状焦熟焦原料混合，采用机械粉碎和气流粉碎至D50为4-5μm，得到超细碳粉。
步骤2、将步骤1所得超细碳粉，按照同性焦生焦∶针状焦熟焦∶三氧化二铁＝30∶70∶15比例加入混捏机，加热至200℃，按照混合物A干粉∶低温沥青＝100∶20加入熔化低温沥青，混捏2h后，取出进行轧片、粉碎、模压成型，得到前驱体。
步骤3、将步骤2所得块状前驱体，进行石墨化，石墨化温度3000℃，时间14d，得到半成品。
步骤4、将步骤3所得半成品依次进行机械破碎，球形化，筛分，得到D50为12-13μm的复合石墨成品。
所得物化指标见表1，倍率性能见图1
实施例5
本实施例用于说明本发明公开的复合石墨的制备方法。
步骤1、将针状焦生焦、同性焦生焦和天然石墨原料混合，采用机械粉碎和 气流粉碎至D50为7-8μm，得到超细碳粉。
步骤2、将步骤1所得超细碳粉，按照同性焦生焦∶针状焦生焦∶天然石墨∶碳化硅＝20∶30∶50∶15比例加入混捏机，加热至200℃，按照混合物A干粉∶低温沥青＝100∶15加入熔化低温沥青，混捏2h后，取出进行轧片、粉碎、模压成型，得到前驱体。
步骤3、将步骤2所得块状前驱体，进行石墨化，石墨化温度3000℃，时间14d，得到半成品。
步骤4、将步骤3所得半成品依次进行机械破碎，球形化，筛分，D50为12-13μm的复合石墨成品。
所得物化指标见表1，倍率性能见图1
实施例6
本实施例用于说明本发明公开的复合石墨的制备方法。
步骤1、将针状焦生焦、中间相碳微球生球和天然石墨原料混合，采用机械粉碎和气流粉碎至D50为7-8μm，得到超细碳粉。
步骤2、将步骤1所得超细碳粉，按照中间相碳微球生球∶针状焦生焦∶天然石墨∶碳化硅＝40∶20∶30∶10比例加入混捏机，加热至200℃，按照混合物A干粉∶低温沥青＝100∶5加入熔化低温沥青，混捏2h后，取出进行轧片、粉碎、模压成型，得到前驱体。
步骤3、将步骤2所得块状前驱体，进行石墨化，石墨化温度3000℃，时间14d，得到半成品。
步骤4、将步骤3所得半成品依次进行机械破碎，球形化，固相法沥青包覆，包覆量为1.5％，1100℃碳化，筛分，得到D50为12-13μm的复合石墨成品。
所得物化指标见表1，倍率性能见图1，SEM形貌见图2
对比例1
本对比例用于对比说明本发明公开的复合石墨的制备方法。
步骤1、将同性焦熟焦和针状焦熟焦原料混合，分别采用机械粉碎和气流粉碎至D50为4-5μm，得到超细碳粉。
步骤2、将步骤1所得超细碳粉，按照同性焦熟焦∶针状焦熟焦∶碳化硅＝30∶70∶15比例加入混捏机，加热至200℃，按照混合物A干粉∶低温沥青＝100∶ 40加入熔化低温沥青，混捏1h后，取出进行模压成型，得到前驱体。
步骤3、将步骤2所得块状前驱体，进行石墨化，得到半成品。
步骤4、将步骤3所得半成品依次进行机械破碎，筛分，得到D50为12-13μm的复合石墨成品。
所得物化指标见表1，倍率性能见图1
对比例2
本对比例用于对比说明本发明公开的复合石墨的制备方法。
步骤1、将天然石墨和同性焦熟焦、针状焦熟焦混合，采用机械粉碎和气流粉碎至D50＝3-5μm，得到超细碳粉。
步骤2、将步骤1所得超细碳粉，按照同性焦熟焦∶针状焦熟焦∶天然石墨∶碳化硅＝50∶20∶30∶15比例加入混捏机，加热至200℃，按照混合物A干粉∶低温沥青＝100∶40加入熔化低温沥青，混捏1h后，取出进行模压成型，得到前驱体。
步骤3、将步骤2所得块状前驱体，进行石墨化，石墨化温度3000℃，时间14d，得到半成品。
步骤4、将步骤3所得半成品依次进行机械破碎，筛分，得到D50为12-13μm的复合石墨成品。
所得物化指标见表1，倍率性能见图1
性能测试
分别将上述实施例1-6和对比例1-2中制备的复合石墨采用日立公司S4800扫描电子显微镜观察样品的表面形貌、颗粒大小等；采用X射线衍射仪X′Pert Pro，PANalytical测试材料的石墨化以及各项异性程度；采用美国麦克仪器公司的Tristar3000全自动比表面积和孔隙度分析仪测试材料的比表面积。采用马尔文激光粒度测试仪MS 2000测试材料粒径范围以及原料颗粒的平均粒径。采用Quantachrome AutoTap振实密度仪测试材料的振实密度。
材料的电化学性能测试
分别将上述实施例1-6和对比例1-2中制备的复合石墨、CMC(固含量为1.2％)、粘结剂SBR(固含量为50％)按质量比96.5∶1.5∶2混合制浆，然后均匀涂覆在11μm厚的铜箔上并烘干，制成面密度70g/m2，压实1.75g/cm3的极片 后冲成直径为16mm圆形极片，在真空干燥箱中120℃干燥10小时备用。
以上述制备的极片为工作电极，锂片为对电极，电解液采用1mol/L的LiPF6的EC/DMC/EMC(体积比为1∶1∶1)，在德国布劳恩手套箱中组装两电极电解池，以0.1C电流密度进行恒电流充放电，电压范围为0.001V-2.5V，测得材料的首次脱锂容量以及首次库伦效率。
以上述制备的极片为工作电极，钴酸锂正极片为对电极，电解液采用1mol/L的LiPF6的EC/DMC/EMC(体积比为1∶1∶1)，在德国布劳恩手套箱中组装电极变位测量电池。上述电池以0.1C电流密度进行恒电流充放电，电压范围为0.001V-2.5V，第二周开始以0.5C电流密度进行恒电流充放电循环，循环20周后，通过电极变位测量电池直接读数，计算极片循环前后的膨胀率。
实施例1-6及对比例1-2所制备的物化测试结果如表1所示。
表1
Figure PCTCN2016099767-appb-000001
从表1的测试结果可以看出，实施例1-6制备的复合石墨在压实、脱锂比容量、倍率、极片膨胀率方面综合性能明显优于对比例1-2。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (12)

  1. 一种复合石墨的制备方法，其特征在于，包括如下步骤：
    S1、提供超细碳粉；所述超细碳粉包括生焦和/或中间相碳微球生球；
    S2、将超细碳粉与粘结剂混合，得到混合物A，混合物A和催化剂混合，得到混合物B，然后对混合物B进行复合处理，得到前驱体；
    S3、对前驱体进行石墨化处理，得到半成品；
    S4、对半成品进行粉碎、球形化、包覆、筛分，得到所述复合石墨。
  2. 根据权利要求1所述的制备方法，其特征在于，所述步骤S1中，超细碳粉的D50为2-10μm；所述生焦的挥发份为5-40％。
  3. 根据权利要求1或2所述的制备方法，其特征在于，所述超细碳粉包括针状焦、沥青焦、同性焦、天然石墨、人造石墨、中间相碳微球生球中的一种或多种；
    所述针状焦为针状焦生焦和/或针状焦熟焦；所述沥青焦为沥青焦生焦和/或沥青焦熟焦；所述同性焦为同性焦生焦和/或同性焦熟焦；
    所述针状焦灰分小于0.5％；所述同性焦结晶度小于30％。
  4. 根据权利要求3所述的制备方法，其特征在于，按质量比，天然石墨含量为70wt％以下，针状焦含量为70wt％以下，同性焦含量为30wt％以下，中间相碳微球生球含量为70wt％以下。
  5. 根据权利要求4所述的制备方法，其特征在于，所述超细碳粉中，天然石墨与针状焦生焦重量之和为70-90wt％，同性焦生焦含量为10-30wt％。
  6. 根据权利要求4所述的制备方法，其特征在于，所述超细碳粉中，中间相碳微球生球与天然石墨重量之和大于50wt％，同性焦生焦含量小于20wt％，同性焦熟焦和/或针状焦含量小于30wt％。
  7. 根据权利要求1-6中任意一项所述的制备方法，其特征在于，所述步骤S2中，所述粘结剂选自中低温沥青、酚醛树脂、环氧树脂、聚酯树脂或聚酰胺 树脂中的一种或多种；
    优选地，所述中低温沥青的软化点为50-100℃。
  8. 根据权利要求1-7中任意一项所述的制备方法，其特征在于，所述步骤S2中，所述催化剂选自硅、硅化合物、铁、铁化合物、硼、硼化合物中的一种或多种；
    所述混合物B中，粘结剂含量占超细碳粉的比例小于20wt％；催化剂含量占超细碳粉的比例小于30wt％。
  9. 根据权利要求1-8中任意一项所述的制备方法，其特征在于，所述步骤S2中，所述复合处理选自固相混捏、液相混捏、轧片、融合、喷雾干燥、模压、等静压、碳化中的一种或多种；所述液相混捏温度为100-300℃，液相混捏时间为1-2h；
    所述步骤S3中，所述石墨化处理的温度为2700-3200℃；
    所述步骤S4中，所述包覆处理选自液相包覆、固相包覆或机械融合中的一种；所述包覆处理所采用的包覆材料选自沥青、树脂、导电石墨中的一种或多种；
    所述筛分粒度D50为4-30μm。
  10. 根据权利要求9所述的制备方法，其特征在于，所述包覆处理为液相包覆，在所述液相包覆之后筛分处理之前还包括碳化处理；所述碳化处理的温度为600-1500℃。
  11. 一种复合石墨，其特征在于，所述复合石墨通过权利要求1-10中任意一项所述的方法制备得到。
  12. 一种锂离子电池，其特征在于，包括依次叠置的正极、隔膜和负极；所述负极包括负极集流体以及位于所述负极集流体上的负极材料，所述负极材料包括权利要求11所述的复合石墨。
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CN111232969A (zh) * 2018-11-28 2020-06-05 上海杉杉科技有限公司 复合中间相负极材料、锂离子二次电池、制备方法和应用
CN114162814B (zh) * 2020-08-20 2024-05-10 洛阳月星新能源科技有限公司 一种石墨的改性方法
CN114162814A (zh) * 2020-08-20 2022-03-11 洛阳月星新能源科技有限公司 一种石墨的改性方法
CN114203979B (zh) * 2020-09-17 2024-05-17 湖南中科星城石墨有限公司 一种石墨负极材料及其制备方法和应用
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CN114702316A (zh) * 2022-03-23 2022-07-05 湖南大学 一种低成本高纯石墨材料的制备方法及应用
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