Hard carbon negative electrode material and preparation method and application thereof
By using a core-shell structured hard carbon anode material, an isotropic core is formed through the cross-linking reaction of modifiers and lithium additives. Furthermore, the problem of low initial efficiency and large specific surface area of hard carbon anode materials is solved through the treatment of an amorphous carbon coating layer, thereby achieving high rate performance and high initial efficiency of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN SHINZOOM TECH
- Filing Date
- 2021-07-02
- Publication Date
- 2026-05-15
AI Technical Summary
Existing hard carbon anode materials have low initial efficiency during the first charge and discharge cycle and a large specific surface area, which is not conducive to improving the rate performance of lithium-ion batteries.
The hard carbon anode material adopts a core-shell structure, with an amorphous carbon shell and a lithium-containing hard carbon core. By adding modifiers and lithium additives to the raw materials, an isotropic core is formed by the cross-linking reaction between the modifier and the substrate material, and chemical bonds are formed during the carbonization process. The specific surface area of the shell is reduced by coating with CVD.
It improves the initial efficiency and rate performance of lithium-ion batteries, reduces the consumption of lithium in the battery system, and has a simple and low-cost manufacturing process, making it suitable for industrial production.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a hard carbon anode material, its preparation method, and its application. Background Technology
[0002] Lithium-ion batteries have a wide range of applications in the new energy field. Graphite, as the most widely used negative electrode material in lithium-ion batteries, has a stable voltage platform and long-cycle stability characteristics. However, its theoretical capacity is only 372 mAh / g, which cannot meet the needs of humans for high-energy-density energy storage.
[0003] Carbon-based anode materials have significant research value. Among them, hard carbon materials can theoretically achieve a capacity of 500 mAh / g, mainly due to the combined lithium storage capacity of the interlayer pore structure and interlayer spacing. CN112573517A discloses a method for preparing a pitch-based hard carbon-coated natural graphite anode material, including the following steps: Step 1, pulverization, pulverizing pitch to an average particle size of 6–10 μm; Step 2, mixing, mixing pitch powder and natural graphite at a mass ratio of 6:100–10:100; Step 3, heating and coating, heating the mixture in an air atmosphere at 250–350℃ in a drum furnace or horizontal reactor while stirring for 2–4 hours, with an air flow rate of 0.5–1.5 m³ / g. 3 / h, to complete the uniform coating of asphalt on natural graphite and the cross-linking and curing of asphalt; Step 4, carbonization, the coated natural graphite is carbonized in a pusher kiln or roller kiln at 1100℃ to obtain asphalt-based hard carbon coated natural graphite anode material. The modified natural graphite prepared by the method shown in this invention has a much better cycle performance than the modified natural graphite prepared by the traditional process, which can meet the actual application of power lithium-ion batteries. CN109037603A discloses a new method for asphalt-based spherical porous doped modified hard carbon anode material, including the following steps: (1) Cross-linking oxidation preparation: after pulverizing high-temperature coal-based asphalt, a cross-linking agent is added under N protection, the asphalt is stirred and heated to melt, the asphalt and the cross-linking agent undergo a cross-linking reaction to prepare cross-linked asphalt, then an oxidant is added, and O2 is introduced, and the reaction is stirred at a constant temperature to obtain cross-linked oxidized asphalt; (2) Spray granulation; (3) Carbonization of asphalt microspheres; (4) Coating and graphitization of asphalt-based hard carbon. Regularly shaped porous pitch-based microspheres were prepared using a low-temperature spray granulation method. After carbonization and coating, spherical hard carbon was prepared, exhibiting a compaction density greater than 1.1 g / cm³, high reversible specific capacity greater than 400 mAh / g, initial coulombic efficiency greater than 80%, capacity retention greater than 85% after 500 cycles, and 30C / 1C capacity retention greater than 98%. It also demonstrated superior electrochemical performance, safety, environmental friendliness, economic efficiency, and a simple process suitable for large-scale industrial production. However, due to some structural defects in the core material used during preparation, the resulting hard carbon anode material exhibited a relatively low initial efficiency during the first charge-discharge cycle.
[0004] CN111439738A discloses a biomass hard carbon, a lithium-ion battery, and their preparation method and application. The preparation method includes the following steps: biomass powder is impregnated in a mixed solution, then filtered, washed until neutral, and dried to obtain material A; material A is pre-carbonized and pulverized to obtain carbon-containing biomass powder with a D50 of 5-8 μm; a mixture of carbon-containing biomass powder, lithium-containing compound, N-containing compound, and P-containing compound is carbonized to obtain the final product; the concentration of silicon-removing substances in the mixed solution is 1-10 mol / L, the concentration of metal-removing substances in the mixed solution is 1-10 mol / L, and the impregnation time is 5-72 h. This preparation method is low-cost, safe, reliable, simple, and suitable for industrial production; the resulting hard carbon material has better performance. However, the biomass hard carbon prepared by this patent is not a core-shell structure, but only contains amorphous carbon, which has certain defects and a large specific surface area, which is not conducive to improving the battery's initial efficiency and rate performance. Therefore, developing a hard carbon anode material with small structural defects that can improve the first-efficiency performance of lithium-ion batteries is a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a hard carbon anode material, its preparation method, and its applications. The hard carbon anode material comprises a shell and a core. The shell is amorphous carbon, and the core is lithium-containing hard carbon. The raw materials for preparing the core include a combination of a substrate material, a modifier, and a lithium additive. This method adds a lithium additive to the raw materials, introducing a lithium active source in the early stages. In subsequent processes, the lithium active source reacts with the substrate material to replenish lithium to the anode material, reducing lithium salt consumption in the electrolyte due to defects in the hard carbon material. Furthermore, by adding a modifier to the substrate material, the substrate material can react with the modifier to obtain an isotropic core, which can then be carbon-coated. This effectively improves the rate performance and initial efficiency of lithium-ion batteries, possessing significant research value.
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] In a first aspect, the present invention provides a hard carbon anode material, wherein the hard carbon anode material has a core-shell structure, the core-shell structure comprising a shell layer and a core; the shell layer is amorphous carbon, and the core is lithium-containing hard carbon;
[0008] The core preparation raw materials include a combination of base material, modifier, and lithium additive;
[0009] The base material includes bitumen and / or tar;
[0010] The lithium additive includes lithium-containing compounds;
[0011] The modifier includes any one or a combination of at least two of the following: polystyrene, polyethylene, polyamide, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinylpyrrolidone, chitosan, polyimide, polyamide, PET, or phenolic resin.
[0012] Preferably, the raw materials for preparing the core include the following components by weight: 1-8 parts by weight of base material, 2-10 parts by weight of modifier and 0.1-0.5 parts by weight of lithium additive.
[0013] The base material may be 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight or 7 parts by weight, and specific values between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values included in the range.
[0014] The modifier may be 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, or 9 parts by weight, as well as specific values between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values included in the range.
[0015] The lithium additive may be 0.15 parts by weight, 0.2 parts by weight, 0.25 parts by weight, 0.3 parts by weight, 0.35 parts by weight, 0.4 parts by weight, or 0.45 parts by weight, as well as specific values between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values included in the range.
[0016] The core raw materials for preparing the core-shell structured hard carbon anode material provided by this invention include a combination of a substrate material, a modifier, and a lithium additive. This is achieved by adding a substrate material made of asphalt and / or tar, and a modifier consisting of any one or at least two of the following: polystyrene, polyethylene, polyamide, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinylpyrrolidone, chitosan, polyimide, polyamide, PET, or phenolic resin. The active functional groups in the modifier can undergo a polycondensation reaction with the oxygen-containing functional groups in the substrate material. This allows the polymer chain structure in the modifier to be grafted onto the aromatic molecular structure of the substrate material. During subsequent carbonization, the modified material... This method can interfere with the directional arrangement of small carbon molecules, prevent the formation of large planar sheet structures, suppress the preparation of anisotropic structural materials, and ultimately obtain isotropic core materials. This reduces the internal defects of the negative electrode material and helps improve the rate performance of lithium-ion batteries. In this scheme, lithium additives are added to the raw materials for core preparation. Lithium additives are added in the front-end preparation process. In the subsequent carbonization process, lithium additives undergo a reduction reaction with the substrate material, and finally form chemical bonds with the defect sites inside the hard carbon material, filling the internal defect sites of the material, reducing the consumption of lithium salts in the electrolyte, and avoiding the large consumption of lithium elements in the later battery system, thereby improving the first efficiency of the battery. This method has important research value.
[0017] Preferably, the lithium-containing compound includes any one or a combination of at least two of Li₂CO₃, LiOH, LiHCO₃, LiCl, lithium nitrate, lithium sulfate, lithium acetate, or organolithium salts.
[0018] Preferably, the raw materials for preparing the shell include any one or a combination of at least two of methane, ethane, propane, ethylene, propylene, butadiene, or acetylene.
[0019] As a preferred technical solution of the present invention, the raw materials for preparing the shell layer of the hard carbon anode material provided by the present invention include any one or a combination of at least two of methane, ethane, propane, ethylene, propylene, butadiene or acetylene. By using the above materials as raw materials to obtain an amorphous carbon coating layer to coat the core, the specific surface area of the material can be further reduced and the first-time efficiency of the battery can be improved.
[0020] In a second aspect, the present invention provides a method for preparing the hard carbon anode material as described in the first aspect, the method comprising the following steps:
[0021] (1) The base material, modifier and lithium additive are mixed, extruded and carbonized to obtain the core material;
[0022] (2) The core material obtained in step (1) is coated to obtain the hard carbon anode material.
[0023] The method for preparing hard carbon anode material provided by this invention firstly involves mixing, extruding, and carbonizing the three core raw materials to complete the crosslinking reaction between the modifier and the substrate material, as well as lithium addition. During carbonization, the lithium additive reacts with the substrate material, ultimately forming a lithium-containing hard carbon core material. The second step involves coating the isotropic core material obtained in the first step. This step further fills in the defects of the core material, reduces its specific surface area, and improves the battery's initial efficiency and rate performance. Furthermore, the preparation method is simple, low-cost, and suitable for mass industrial production and application.
[0024] Preferably, the extrusion in step (1) is performed using a twin-screw extruder.
[0025] Preferably, the extrusion temperature in step (1) is 100 to 300°C, for example 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C or 280°C, and specific values between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values included in the range.
[0026] As a preferred embodiment of the present invention, a better isotropic core material can be obtained when the extrusion temperature is between 100 and 300°C. During the extrusion process, the main purpose of heating is to form a liquid phase in the base material, but it is necessary to ensure that the light components inside the base material do not volatilize. On the one hand, if the temperature is too high, above 300°C, the small molecular weight aromatic molecules inside the base material will volatilize; on the other hand, if the temperature is too low, below 100°C, the base material will not be able to form a liquid phase, thus failing to react sufficiently with the modifier.
[0027] The extrusion speed in step (1) is 0.1 to 2 m / min, for example 0.2 m / min, 0.4 m / min, 0.6 m / min, 0.8 m / min, 1 m / min, 1.2 m / min, 1.4 m / min, 1.6 m / min or 1.8 m / min, and specific values between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values included in the range.
[0028] Preferably, the screw speed of the extrusion in step (1) is 100 to 800 rpm, for example 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm or 750 rpm, and specific values between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values included in the range.
[0029] As a preferred embodiment of the present invention, the screw speed during extrusion is 100–800 rpm to better obtain isotropic materials, because excessively high or low screw speeds will lead to insufficient mixing and reaction between materials. Under the high-speed operation inside the twin-screw extruder, the heated, fluidized base material undergoes an effective polycondensation reaction with the modifier containing active functional groups. The rotation of the screw generates strong shear forces, which can temporarily release small aromatic molecules within the base material from the van der Waals forces between the lamellar structures. This process better leverages the polycondensation reaction between the functional groups on the lamellar material and the modifier, thereby achieving better modification of the isotropic material.
[0030] Preferably, the carbonization process in step (1) is carried out under inert gas protection conditions.
[0031] Preferably, the carbonization process in step (1) is carried out under heated conditions.
[0032] Preferably, the heating method includes: first heating the system to 400–700°C (e.g., 430°C, 460°C, 490°C, 530°C, 560°C, or 590°C), holding it at this temperature for 1–5 hours (e.g., 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or 4.5 hours), during which the lithium additive undergoes a reduction reaction with the substrate material; then heating the system a second time to 900–1300°C (e.g., 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, or 1300°C), holding it at this temperature for 4–12 hours (e.g., 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or 11 hours), the purpose of which is to achieve carbonization of the material;
[0033] Preferably, the heating rates of the first and second heating are each independently 1 to 10°C / min, for example 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min or 9°C / min, and specific values between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values included in the range.
[0034] Preferably, the coating process in step (2) is CVD coating.
[0035] Preferably, the coating process in step (2) is carried out under heated conditions.
[0036] Preferably, the heating method includes: heating the system to 700–1200°C (e.g., 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, or 1150°C, etc.), and holding at that temperature for 5–20 hours (e.g., 7 hours, 9 hours, 11 hours, 13 hours, 15 hours, 17 hours, or 19 hours, etc.) to complete the heating process.
[0037] Preferably, the heating rate is 1 to 10°C / min, for example 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min or 9°C / min, and specific values between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values included in the range.
[0038] Preferably, the pyrolysis gas source for the coating treatment in step (2) includes any one or a combination of two of methane, ethane, propane, ethylene, propylene, butadiene or acetylene.
[0039] As a preferred technical solution of the present invention, the coating process in step (2) of the preparation method provided by the present invention using CVD under heating conditions has two main functions: First, the carbon coating layer formed by using any one or at least two of methane, ethane, propane, ethylene, propylene, butadiene or acetylene as the cracking gas source can treat the defects on the surface of the isotropic core material obtained in step (1), reduce the specific surface area of the core material, and improve the first efficiency of the lithium-ion battery when it is applied to the lithium-ion battery; at the same time, a protective layer structure can be formed on the surface of the isotropic core material obtained in step (1) to prevent the lithium-containing isotropic material from contacting the air and causing damage to the material.
[0040] As a preferred technical solution, the preparation method includes the following steps:
[0041] (1) The base material, modifier and lithium additive are mixed and extruded through a twin-screw extruder at 100-300℃, extrusion speed of 0.1-2m / min and screw speed of 100-800rpm. The mixture is then carbonized under inert gas and heating conditions to obtain the core material. The heating method includes: heating the system to 400-700℃ for the first time and holding it for 1-5h; heating the system to 900-1300℃ for the second time and holding it for 4-12h to complete the heating.
[0042] (2) The core material obtained in step (1) is subjected to CVD coating under heating conditions to obtain the hard carbon anode material; the cracked gas source for coating treatment includes any one or a combination of two of methane, ethane, propane, ethylene, propylene, butadiene or acetylene; the heating method includes heating the system to 700-1200℃ and holding it at that temperature for 5-20h to complete the heating.
[0043] Thirdly, the present invention provides a lithium-ion battery, wherein the negative electrode material of the lithium-ion battery includes the hard carbon negative electrode material as described in the first aspect.
[0044] Compared with the prior art, the present invention has the following beneficial effects:
[0045] (1) The core of the hard carbon anode material with a core-shell structure provided by the present invention is lithium-containing hard carbon; the raw materials for preparing the core include a combination of base material, modifier and lithium additive; further, by selecting asphalt and / or tar as base material, and selecting any one or at least two combinations of polystyrene, polyethylene, polyamide, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinylpyrrolidone, chitosan, polyimide, polyamide, PET or phenolic resin as modifier, the base material and modifier can undergo cross-linking reaction during processing, disrupting the regularity of the structure. In addition, lithium additive is added, and the reaction between lithium additive and base material is used to finally form chemical bonds between lithium carbon materials to achieve the purpose of lithium replenishment, reduce the internal defects of carbon materials, avoid the large consumption of lithium elements during battery cycling, thereby improving the first efficiency and rate performance of the battery;
[0046] (2) The shell of the hard carbon anode material provided by the present invention has an amorphous carbon coating layer. The amorphous carbon coating layer can treat the surface defects of the core material, reduce the specific surface area of the core material, and form a protective layer structure on the surface of the core to prevent the lithium-containing core material from contacting the air and causing damage to the material. This improves the first efficiency of the lithium-ion battery when it is applied to the lithium-ion battery. Moreover, the preparation process of the hard carbon anode material is simple and low in cost. It can achieve the dual gains of high rate and high first efficiency, which has important research significance.
[0047] (3) Specifically, the lithium-ion battery prepared using the hard carbon anode material provided by the present invention has a 0.1C capacity of 400-530 mAh / g, a first-cycle efficiency of 75-85.7%, and a 5C / 0.5C rate of 28-44%. Detailed Implementation
[0048] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.
[0049] Example 1
[0050] A hard carbon anode material with a core-shell structure, comprising a core and a shell;
[0051] The core raw materials for preparation include the following components by weight:
[0052] 4 parts by weight of asphalt;
[0053] 5 parts by weight of phenolic resin
[0054] 0.3 parts by weight of Li2CO3;
[0055] The preparation method of the hard carbon anode material provided in this embodiment includes the following steps:
[0056] (1) Asphalt, phenolic resin (CAS:9003-35-4) and Li2CO3 are mixed and extruded through a twin-screw extruder at 200℃, an extrusion speed of 1m / min and a screw speed of 400rpm. The mixture is then carbonized under argon and heating conditions to obtain the core material. The heating method includes: heating the system to 600℃ at a heating rate of 5℃ / min and holding it at that temperature for 2.5h; then heating the system to 1000℃ and holding it at that temperature for 8h to complete the heating process.
[0057] (2) The core material obtained in step (1) is subjected to CVD coating under the conditions of heating and cracking gas source of methane to obtain the hard carbon anode material; the heating method includes: heating the system to 900°C and holding it for 10 hours to complete the heating.
[0058] Example 2
[0059] A hard carbon anode material with a core-shell structure, comprising a core and a shell;
[0060] The core raw materials for preparation include the following components by weight:
[0061] 1 part by weight of tar;
[0062] 2 parts by weight of polyimide
[0063] 0.1 parts by weight of LiOH;
[0064] The preparation method of the hard carbon anode material provided in this embodiment includes the following steps:
[0065] (1) Tar, polyimide (Zhejiang Jiari Fluoroplastics Co., Ltd.) and LiOH are mixed and extruded through a twin-screw extruder at 100℃, an extrusion speed of 0.1m / min and a screw speed of 800rpm. The mixture is then carbonized under argon and heating conditions to obtain the core material. The heating method includes: heating the system to 400℃ at a heating rate of 1℃ / min and holding it at that temperature for 5h; heating the system to 900℃ and holding it at that temperature for 12h to complete the heating process.
[0066] (2) The core material obtained in step (1) is subjected to CVD coating under the conditions of heating and cracking gas source of acetylene to obtain the hard carbon anode material; the heating method includes: heating the system to 700°C and holding it for 20 hours to complete the heating.
[0067] Example 3
[0068] A hard carbon anode material with a core-shell structure, comprising a core and a shell;
[0069] The core raw materials for preparation include the following components by weight:
[0070] 8 parts by weight of asphalt;
[0071] 10 parts by weight of polyamide
[0072] 0.5 parts by weight of LiHCO3;
[0073] The preparation method of the hard carbon anode material provided in this embodiment includes the following steps:
[0074] (1) Asphalt, polyamide (CAS: 63428-84-2) and LiHCO3 are mixed and extruded through a twin-screw extruder at 300℃, an extrusion speed of 2m / min and a screw speed of 100rpm. The mixture is then carbonized under argon and heating conditions to obtain the core material. The heating method includes: heating the system to 700℃ at a heating rate of 10℃ / min and holding it at that temperature for 1h; heating the system to 900℃ and holding it at that temperature for 4h to complete the heating process.
[0075] (2) The core material obtained in step (1) is subjected to CVD coating under the conditions of heating and pyrolysis gas source of propane to obtain the hard carbon anode material; the heating method includes: heating the system to 800°C and holding it for 5 hours to complete the heating.
[0076] Example 4
[0077] A hard carbon anode material, which differs from Example 1 only in that the extrusion temperature in step (1) is 100°C, while the other components, amounts and preparation methods are the same as in Example 1.
[0078] Example 5
[0079] A hard carbon anode material, which differs from Example 1 only in that the extrusion temperature in step (1) is 300°C, while the other components, amounts and preparation methods are the same as in Example 1.
[0080] Example 6
[0081] A hard carbon anode material, which differs from Example 1 only in that the extrusion temperature in step (1) is 50°C, while the other components, amounts and preparation methods are the same as in Example 1.
[0082] Example 7
[0083] A hard carbon anode material, which differs from Example 1 only in that the extrusion temperature in step (1) is 400°C, while the other components, amounts and preparation methods are the same as in Example 1.
[0084] Example 8
[0085] A hard carbon anode material, which differs from Example 1 only in that the screw speed of extrusion in step (1) is 100 rpm, while the other components, dosages and preparation methods are the same as in Example 1.
[0086] Example 9
[0087] A hard carbon anode material, which differs from Example 1 only in that the screw speed during extrusion in step (1) is 800 rpm, while the other components, dosages and preparation methods are the same as in Example 1.
[0088] Example 10
[0089] A hard carbon anode material, which differs from Example 1 only in that the screw speed of extrusion in step (1) is 50 rpm, while the other components, dosages and preparation methods are the same as in Example 1.
[0090] Example 11
[0091] A hard carbon anode material, which differs from Example 1 only in that the screw speed during extrusion in step (1) is 900 rpm, while the other components, dosages and preparation methods are the same as in Example 1.
[0092] Comparative Example 1
[0093] A hard carbon anode material with a core-shell structure, comprising a core and a shell;
[0094] The core raw materials for preparation include the following components by weight:
[0095] 9 parts by weight of asphalt;
[0096] 0.3 parts by weight of Li2CO3;
[0097] The preparation method of the hard carbon anode material provided in this embodiment includes the following steps:
[0098] (1) Asphalt and Li2CO3 are mixed and extruded through a twin-screw extruder at 200℃, an extrusion speed of 1m / min and a screw speed of 400rpm. The mixture is then carbonized under argon and heating conditions to obtain the core material. The heating method includes: heating the system to 600℃ at a heating rate of 5℃ / min and holding it at that temperature for 2.5h; and heating the system to 1200℃ and holding it at that temperature for 8h to complete the heating process.
[0099] (2) The core material obtained in step (1) is subjected to CVD coating under the conditions of heating and cracking gas source of methane to obtain the hard carbon anode material; the heating method includes: heating the system to 1000℃ and holding it for 10h to complete the heating.
[0100] Comparative Example 2
[0101] A hard carbon anode material with a core-shell structure, comprising a core and a shell;
[0102] The core raw materials for preparation include the following components by weight:
[0103] 4 parts by weight of asphalt;
[0104] 5 parts by weight of chitosan;
[0105] The preparation method of the hard carbon anode material provided in this embodiment includes the following steps:
[0106] (1) Asphalt and chitosan are mixed and extruded through a twin-screw extruder at 200°C, an extrusion speed of 1 m / min and a screw speed of 400 rpm. The mixture is then carbonized under argon and heating conditions to obtain the core material. The heating method includes: heating the system to 600°C at a heating rate of 5°C / min and holding it at that temperature for 2.5 h; and heating the system to 1200°C and holding it at that temperature for 8 h to complete the heating process.
[0107] (2) The core material obtained in step (1) is subjected to CVD coating under the conditions of heating and cracking gas source of methane to obtain the hard carbon anode material; the heating method includes: heating the system to 1000℃ and holding it for 10h to complete the heating.
[0108] Comparative Example 3
[0109] A hard carbon anode material, the raw materials for which are prepared include the following components in parts by weight:
[0110] 4 parts by weight of asphalt;
[0111] 5 parts by weight of chitosan
[0112] 0.3 parts by weight of Li2CO3;
[0113] The preparation method of the hard carbon anode material provided in this embodiment includes: mixing asphalt, chitosan and Li2CO3, extruding the mixture through a twin-screw extruder at 200°C, an extrusion speed of 1 m / min and a screw speed of 400 rpm, and then carbonizing the mixture under argon and heating conditions to obtain the hard carbon anode material; the heating method includes: heating the system to 600°C at a heating rate of 5°C / min and holding it at that temperature for 2.5 h; then heating the system to 1200°C and holding it at that temperature for 8 h to complete the heating process.
[0114] Application Examples 1-11
[0115] A lithium-ion battery, wherein the negative electrode material is the hard carbon negative electrode material prepared in Examples 1 to 11, and the process conditions are as follows:
[0116] The hard carbon anode materials prepared in Examples 1 to 11 were mixed with SBR, CMC and SP in a ratio of 94.5:2.5:1.5:1.5 to form a uniform mixture. The mixture was then coated onto copper foil, dried, rolled, and cut to form an electrode sheet with a diameter of 12 mm. The electrode sheet was then assembled with a lithium metal sheet to form a button cell. The electrolyte was a conventional lithium-ion battery electrolyte, and the separator was a PP separator.
[0117] Comparative Application Examples 1-3
[0118] A lithium-ion battery, wherein the negative electrode material is a hard carbon negative electrode material prepared in Comparative Examples 1 to 3; the preparation process conditions of the lithium-ion battery are the same as those in Application Example 1.
[0119] Performance testing:
[0120] (1) 0.1C capacity, first-week efficiency and 5C / 0.5C rate: tested using a Blue Electric tester.
[0121] The performance of lithium-ion batteries provided in Application Examples 1-3 were compared with those provided in the above test methods and corresponding test cases 1-11. The results are shown in Table 1.
[0122] Table 1
[0123]
[0124]
[0125] As can be seen from the data in Table 1, the batteries prepared using the core-shell structured hard carbon anode material provided by this invention have high first-cycle efficiency and rate performance. Specifically, the lithium-ion batteries obtained in Examples 1 to 11 have a 0.1C capacity of 400 to 530 mAh / g, a first-cycle efficiency of 75 to 85.7%, and a 5C / 0.5C rate of 28 to 44%.
[0126] Comparing Application Example 1 and Comparative Application Example 1, it can be seen that the lithium-ion battery obtained in Comparative Application Example 1 has a significant decrease in 0.1C capacity, first-cycle efficiency, and 5C / 0.5C rate capability. This indicates that unmodified asphalt as a negative electrode material is not conducive to improving the rate performance and capacity of the battery.
[0127] Comparing Application Example 1 and Comparative Application Example 2, it can be seen that the lithium-ion battery obtained in Comparative Application Example 2 has a significant decrease in 0.1C capacity, first-cycle efficiency, and 5C / 0.5C rate capability. This proves that hard carbon anode materials without lithium additives in the early stage are also not conducive to improving the rate performance and capacity of the battery.
[0128] Comparing Application Example 1 and Comparative Application Example 3, it can be seen that the lithium-ion battery prepared with the uncoated hard carbon anode material has a significant decrease in 0.1C capacity, first-cycle efficiency, and 5C / 0.5C rate capability.
[0129] Further comparison of Application Example 1 and Application Examples 4-7 reveals that the 0.1C capacity, first-cycle efficiency, and 5C / 0.5C rate of the lithium-ion batteries obtained in Application Examples 6 and 7 are all lower than those in Application Examples 1 and 4-5. This indicates that only by extruding at a specific temperature can the highest-performing hard carbon anode material be obtained, thereby resulting in a lithium-ion battery with excellent electrical performance.
[0130] Further comparison of Application Examples 2 and 8-11 reveals that the 0.1C capacity, first-cycle efficiency, and 5C / 0.5C rate of the lithium-ion batteries obtained in Application Examples 10 and 11 are all lower than those in Application Examples 1 and 8-9. This demonstrates that only by extruding at a specific screw speed can the highest-performing hard carbon anode material be obtained, thereby leading to lithium-ion batteries with excellent electrical performance.
[0131] The applicant declares that this invention illustrates a hard carbon anode material, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.
Claims
1. A hard carbon anode material, characterized in that, The hard carbon anode material has a core-shell structure, which includes a shell and a core. The shell is amorphous carbon; The core is lithium-containing hard carbon; The core preparation raw materials are a combination of base material, modifier and lithium additive; The base material includes bitumen and / or tar; The lithium additive is a lithium-containing compound; The modifier includes any one or a combination of at least two of the following: polystyrene, polyethylene, polyamide, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinylpyrrolidone, chitosan, polyimide, polyamide, PET, or phenolic resin. In this process, the base material and the modifier react to obtain an isotropic core; The lithium-containing compound is any one or a combination of at least two of the following: Li₂CO₃, LiOH, LiHCO₃, LiCl, lithium nitrate, lithium sulfate, lithium acetate, or organolithium salts; The hard carbon anode material is prepared by the following method, the method comprising: (1) The base material, modifier and lithium additive are mixed, extruded and carbonized to obtain the core material; (2) The core material obtained in step (1) is coated to obtain the hard carbon anode material; The extrusion temperature in step (1) is 100~300℃; The screw speed for extrusion in step (1) is 100~800 rpm.
2. The hard carbon anode material as described in claim 1, characterized in that, The raw materials for the preparation of the core are as follows by weight: 1-8 parts by weight of base material, 2-10 parts by weight of modifier and 0.1-0.5 parts by weight of lithium additive.
3. The hard carbon anode material according to claim 1, characterized in that, The raw materials for preparing the shell include any one or a combination of at least two of methane, ethane, propane, ethylene, propylene, butadiene, or acetylene.
4. A method for preparing the hard carbon anode material as described in any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: (1) The base material, modifier and lithium additive are mixed, extruded and carbonized to obtain the core material; (2) The core material obtained in step (1) is coated to obtain the hard carbon anode material; The extrusion temperature in step (1) is 100~300℃; The screw speed for extrusion in step (1) is 100~800 rpm.
5. The preparation method according to claim 4, characterized in that, The extrusion in step (1) is carried out by a twin-screw extruder.
6. The preparation method according to claim 4, characterized in that, The extrusion speed in step (1) is 0.1~2 m / min.
7. The preparation method according to claim 4, characterized in that, The carbonization process described in step (1) is carried out under inert gas protection.
8. The preparation method according to claim 4, characterized in that, The carbonization process described in step (1) is carried out under heated conditions.
9. The preparation method according to claim 8, characterized in that, The heating method includes: heating the system to 400~700℃ for the first time and holding it at that temperature for 1~5 h; heating the system to 900~1300℃ for the second time and holding it at that temperature for 4~12 h, thus completing the heating process.
10. The preparation method according to claim 9, characterized in that, The heating rates for the first and second heating cycles are each 1~10℃ / min.
11. The preparation method according to claim 4, characterized in that, The coating process in step (2) is CVD coating.
12. The preparation method according to claim 4, characterized in that, The coating process described in step (2) is carried out under heated conditions.
13. The preparation method according to claim 12, characterized in that, The heating method includes: heating the system to 700~1200℃ and holding it at that temperature for 5~20 h to complete the heating.
14. The preparation method according to claim 12, characterized in that, The heating rate is 1~10℃ / min.
15. The preparation method according to claim 4, characterized in that, The pyrolysis gas source for the coating treatment in step (2) includes any one or a combination of two of methane, ethane, propane, ethylene, propylene, butadiene or acetylene.
16. The preparation method according to claim 4, characterized in that, The preparation method includes the following steps: (1) The base material, modifier and lithium additive are mixed and extruded through a twin-screw extruder at 100~300℃, extrusion speed of 0.1~2m / min and screw speed of 100~800 rpm, and carbonized under inert gas and heating conditions to obtain the core material; The heating method includes: heating the system to 400~700℃ for the first time and holding it at that temperature for 1~5 hours; heating the system to 900~1300℃ for the second time and holding it at that temperature for 4~12 hours to complete the heating process; (2) The core material obtained in step (1) is subjected to CVD coating under heating conditions to obtain the hard carbon anode material; the cracked gas source for coating treatment includes any one or a combination of two of methane, ethane, propane, ethylene, propylene, butadiene or acetylene; the heating method includes heating the system to 700~1200℃ and holding it at that temperature for 5~20 h to complete the heating.
17. A lithium-ion battery, characterized in that, The negative electrode material of the lithium-ion battery includes the hard carbon negative electrode material as described in any one of claims 1 to 3.