Fast-charging anode materials, their preparation methods and lithium-ion batteries

Abstract

This invention provides a fast-charging anode material, its preparation method, and a lithium-ion battery. The preparation method of the fast-charging anode material includes: obtaining bulk porous graphite, wherein the specific surface area of ​​the bulk porous graphite is 1-2 m². 2 / g; Under inert atmosphere and vacuum conditions, a first suspension containing a metal element is atomized and deposited onto bulk porous graphite to obtain a metal layer. The metal element is selected from one or more of tin, silver, and copper. A second suspension containing a catalyst is atomized and deposited onto the metal layer to obtain a metal / catalyst-doped graphite precursor material. The metal / catalyst-doped graphite precursor material is then carbonized to obtain a fast-charging anode material. The fast-charging anode material prepared by the above method has low impedance, high energy density, and high structural stability and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and more specifically, to a fast-charging negative electrode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] In the field of fast charging for electric vehicles, graphite materials are required not only to have high energy density but also high fast charging performance. Currently, commercially available artificial graphite is mainly improved through the following measures to enhance fast charging performance: reducing the particle size of the material, shortening the insertion and extraction path, and coating the solid or liquid phase of the material with amorphous carbon to increase the diffusion rate of lithium ions during charging and discharging.

[0003] Existing literature (CN115385330 A) provides a method for preparing a high-energy-density, low-expansion, and fast-charging graphite anode, comprising the following steps: pulverizing calcined coke and homogenizing it with a modifier to obtain material A; heating material A under an inert atmosphere to obtain material B; sieving material B and then mechanically fusing it to obtain material C; graphitizing material C, followed by sieving and mixing to obtain the finished product. The graphite anode material obtained by this method is a secondary particle with high energy density, strong isotropy, good rate capability, and low expansion rate.

[0004] Existing literature (CN 110429265 A) provides a MEG / Si / C composite anode material for lithium-ion batteries and its preparation method. This composite anode material comprises the following components by mass fraction: 2-20% nano-silicon powder, 1-3% surfactant, and 10-30% carbon source, with the balance being micro-expanded graphite. Micro-expanded graphite is prepared using a chemical oxidation intercalation method and a low-temperature thermal expansion technique. Then, the micro-expanded graphite / silicon / carbon (MEG / Si / C) composite anode material for lithium-ion batteries is prepared by mechanical ball milling and a high-temperature carbonization method. This invention not only effectively alleviates the volume expansion and contraction effects of lithium intercalation / deintercalation in graphite layers but also increases lithium intercalation / deintercalation channels, which is beneficial for high-current charging and discharging, ensuring appropriate volumetric energy density and coulombic efficiency of the anode material.

[0005] Existing literature (CN 103072974 A) provides a surface coating method for artificial graphite carbon anode materials, employing an in-situ polymerization coating method: First, artificial graphite is added to a certain concentration of H2O2 and stirred rapidly at a speed of 200–500 rpm for 0.5–2 hours; then, it is filtered and washed, and the oxidized artificial graphite is added to a certain concentration of phenol solution, heated and stirred at a temperature of 70–100℃ at a speed of 200–500 rpm for 10–60 minutes; then, formaldehyde solution is added dropwise according to a stoichiometric ratio, followed by hydrochloric acid solution, controlling the pH of the solution at 1.9–2.3, and stirred again for 0.5–2 hours; then, an appropriate amount of hexamethylenetetramine (urotropine) is added to cure the phenolic resin. After complete curing, the sample is washed and separated, then dried and carbonized to obtain a uniformly coated modified artificial graphite anode material.

[0006] Although the above methods can improve the performance of anode materials to some extent, these improvement measures have reached their limits and are difficult to significantly improve or only slightly improve the performance. They also have defects such as uneven coating thickness. Summary of the Invention

[0007] The main objective of this invention is to provide a fast-charging anode material, its preparation method, and a lithium-ion battery, in order to solve the problems that the energy density of graphite anode materials prepared by existing processes is difficult to improve significantly or the improvement is not significant, and the coating layer has uneven thickness.

[0008] To achieve the above objectives, the present invention provides a method for preparing a fast-charging negative electrode material, comprising: obtaining bulk porous graphite, wherein the specific surface area of ​​the bulk porous graphite is 1-2 m². 2 / g; Under inert atmosphere and vacuum conditions, a first suspension containing a metal element is atomized and deposited on bulk porous graphite to obtain a metal layer. The metal element is selected from one or more of tin, silver and copper. A second suspension containing a catalyst is atomized and deposited on the metal layer to obtain a metal / catalyst-doped graphite precursor material. The metal / catalyst-doped graphite precursor material is carbonized to obtain a fast-charging negative electrode material.

[0009] Further, the first suspension comprises: a metal element, an organic solvent, and a dispersant, wherein the content of the metal element in the first suspension is 1-10 wt%; preferably, the particle size of the metal element is 500-2000 nm; preferably, the metal element is selected from one or more of tin, silver, and copper; preferably, the organic solvent is selected from one or more of carbon tetrachloride, benzene, acetone, propylene glycol propyl ether, and ethylene glycol propyl ether; preferably, the dispersant is selected from one or more of sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, and polyethylene glycol-type polyols.

[0010] Furthermore, the second suspension includes a catalyst and an alcohol solvent, and the catalyst content in the second suspension is 1 to 10 wt%; the catalyst is selected from one or more of ferric chloride, nickel chloride and cobalt chloride; the alcohol solvent is selected from one or more of methanol, 1,4-butanediol, isopropanol and 1,3-butanediol.

[0011] Furthermore, during the first deposition process, the vacuum level was 100–1000 Pa, the temperature was 100–200 °C, and the deposition time was 10–60 min; during the second deposition process, the deposition time was 30–300 min.

[0012] Furthermore, the carbonization process includes reacting carbon-based gas with a metal / catalyst-doped graphite precursor material to obtain a fast-charging anode material.

[0013] Furthermore, the carbon-based gas is selected from one or more of methane, ethane, ethylene, and acetylene.

[0014] Furthermore, the carbonization process is carried out at a temperature of 700–1100℃ for 1–6 hours.

[0015] Furthermore, the weight ratio of bulk porous graphite, elemental metal, dispersant and catalyst is 100:(1~10):(0.5~2):(0.5~2).

[0016] A second aspect of this application also provides a fast-charging negative electrode material, comprising bulk porous graphite and a coating layer, wherein the coating layer is coated on the surface of the bulk porous graphite, and wherein the coating layer is a mixture of elemental metal, carbon nanotubes and amorphous carbon, wherein the content of elemental metal is 10-50% and the content of carbon nanotubes is 1-10% by weight percentage of the coating layer, or the fast-charging negative electrode material is prepared by the above preparation method.

[0017] A third aspect of this application also provides a lithium-ion battery, including a negative electrode material, the negative electrode material including the aforementioned fast-charging negative electrode material.

[0018] By applying the technical solution of this invention, a specific elemental metal is deposited in the pores and surface of bulk porous graphite using a gas-state atomization method. The high electronic conductivity of this metal reduces the impedance of the core graphite. Simultaneously, a catalyst deposited on the surface acts as a catalyst during the carbonization stage, growing carbon nanotubes and further reducing impedance to improve fast-charging performance. The outer carbon nanotubes have a large specific surface area and form a network structure with amorphous carbon doping, enhancing the material's structural stability and cycle performance. Furthermore, the gas-state atomization method for depositing the metal and catalyst allows for a more controllable and efficient process. Based on this, the fast-charging anode material prepared using the above method exhibits lower impedance, higher energy density, and better structural stability and cycle performance. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 This is a SEM image of the graphite composite material prepared in Example 1. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0022] As described in the background section, graphite anode materials prepared using existing processes suffer from limitations in significantly improving energy density or exhibiting only minor improvements, and the coating layer suffers from uneven thickness. To address these technical problems, this application provides a method for preparing a fast-charging anode material, comprising: obtaining bulk porous graphite with a specific surface area of ​​1–2 m². 2 / g; Under inert atmosphere and vacuum conditions, a first suspension containing a metal element is atomized and deposited on bulk porous graphite to obtain a metal layer. The metal element is selected from one or more of tin, silver and copper. A second suspension containing a catalyst is atomized and deposited on the metal layer to obtain a metal / catalyst-doped graphite precursor material. The metal / catalyst-doped graphite precursor material is carbonized to obtain a fast-charging negative electrode material.

[0023] In the above preparation method, a specific elemental metal is deposited in the pores and surface of bulk porous graphite via gas atomization, leveraging its high electronic conductivity to reduce the impedance of the core graphite. Simultaneously, a catalyst deposited on the surface acts as a catalyst during the carbonization stage, growing carbon nanotubes and further reducing impedance to improve fast-charging performance. The outer carbon nanotubes have a large specific surface area and form a network structure with amorphous carbon doping, enhancing the material's structural stability and cycle performance. Furthermore, the gas atomization method for depositing the metal and catalyst results in a thin deposition thickness, having minimal impact on the battery's energy density, and the entire process is controllable and more efficient. Based on these advantages, the fast-charging anode material prepared using this method exhibits low impedance, high energy density, and superior structural stability and cycle performance.

[0024] In a preferred embodiment, the first suspension comprises: a metal element, an organic solvent, and a dispersant, wherein the content of the metal element in the first suspension is 1–10 wt%. Using a first suspension with the above composition is beneficial for improving the dispersion performance of the metal element, thereby enhancing the uniformity of the dispersion of the specific metal element on the bulk porous graphite during the first deposition process, increasing the density of the metal layer, and further reducing its impedance, increasing battery capacity and lifespan.

[0025] To further improve the dispersion performance of elemental metals, preferably, the particle size of elemental metals is 500–2000 nm.

[0026] The organic solvents and dispersants mentioned above can be selected from those commonly used in the art. Preferably, the organic solvents include, but are not limited to, one or more of carbon tetrachloride, benzene, acetone, propylene glycol propyl ether, and ethylene glycol propyl ether; the dispersants include, but are not limited to, one or more of sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, and polyethylene glycol-type polyols.

[0027] In a preferred embodiment, the second suspension comprises a catalyst and an alcohol solvent, wherein the catalyst content in the second suspension is 1–10 wt%. Dispersing the catalyst in an alcohol solvent to form a suspension further improves the catalyst's dispersibility, thereby further improving the uniformity of catalyst dispersion in the metal / catalyst-doped graphite precursor material during the second deposition process. In a preferred embodiment, the catalyst includes, but is not limited to, one or more of ferric chloride, nickel chloride, and cobalt chloride. Using the above-mentioned catalysts enables the polymerization of carbon-based gases to form carbon nanotubes, and exhibits higher catalytic activity compared to other catalysts.

[0028] The alcohol solvents mentioned above can be selected from those commonly used in the art. Preferably, the alcohol solvent is selected from one or more of methanol, 1,4-butanediol, isopropanol, and 1,3-butanediol.

[0029] In a preferred embodiment, during the first deposition process, the vacuum level is 100–1000 Pa, the temperature is 100–200 °C, and the deposition time is 10–60 min; during the second deposition process, the deposition time is 30–300 min.

[0030] Under the above conditions, performing the first and second deposition processes is beneficial to improving the deposition rate and dispersion uniformity of specific metal elements and catalysts on bulk porous graphite.

[0031] In a preferred embodiment, the carbonization process includes reacting a carbon-based gas with a metal / catalyst-doped graphite precursor material to obtain a fast-charging anode material. During the carbonization process, under the action of a catalyst, at least a portion of the carbon-based gas polymerizes to form carbon nanotubes, while the remaining carbon-based gas forms amorphous carbon. Preferably, the carbon-based gas includes, but is not limited to, one or more of methane, ethane, ethylene, and acetylene.

[0032] In a preferred embodiment, the carbonization process is carried out at a temperature of 700–1100°C for 1–6 hours. The temperature and time of the carbonization process include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to further improve the coating efficiency of the carbon coating layer (carbon nanotubes and amorphous carbon), thereby further reducing the internal resistance of the formed negative electrode material.

[0033] In a preferred embodiment, the weight ratio of bulk porous graphite, elemental metal, dispersant, and catalyst is 100:(1-10):(0.5-2):(0.5-2). The weight ratio of bulk porous graphite, elemental metal, dispersant, and catalyst is not limited to the above range, but limiting it to the above range is beneficial for further improving the energy density, structural stability, and cycle performance of the formed negative electrode material.

[0034] The bulk porous graphite used in this application can be prepared in-house or a commercially available product. In a preferred embodiment, the bulk porous graphite is prepared by the following method: etching the surface of the graphite with a concentrated nitric acid / hydrochloric acid gas (volume ratio 1:1, hydrochloric acid concentration 10wt%) for 1–6 hours to obtain porous graphite; and then pressing the porous graphite into blocks using a hot press to obtain bulk porous graphite. More preferably, the pressure during the pressing process is 1–5T, the temperature is 80–150℃, and the holding time is 60–480 min.

[0035] A second aspect of this application also provides a fast-charging negative electrode material, comprising bulk porous graphite and a coating layer coated on the surface of the bulk porous graphite, wherein the coating layer is a mixture of elemental metal, carbon nanotubes and amorphous carbon, wherein the content of elemental metal is 10-50% and the content of carbon nanotubes is 1-10% by weight percentage of the coating layer, or the fast-charging negative electrode material is prepared by the above-described preparation method.

[0036] Fast-charging anode materials with the above composition or prepared by the above method have low impedance, high energy density, and high structural stability and cycle performance.

[0037] A third aspect of this application also provides a lithium-ion battery, including a negative electrode material, wherein the negative electrode material includes the aforementioned fast-charging negative electrode material. Because the aforementioned fast-charging negative electrode material has low impedance, high energy density, and high structural stability and cycle performance, using it as a negative electrode material in a lithium-ion battery is beneficial for further improving the overall performance of the lithium-ion battery.

[0038] A fourth aspect of this application also provides an electric drive device, including a power source comprising at least one of the aforementioned lithium-ion batteries. Because the aforementioned lithium-ion batteries have low impedance, they have high charging efficiency and long service life. Simultaneously, they possess high energy density, structural stability, and high cycle performance, which can, to a certain extent, increase the single-charge capacity of the electric drive device, while also improving its performance stability and the number of charging cycles. Preferably, the aforementioned electric drive device is an electric vehicle.

[0039] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0040] Example 1

[0041] A method for preparing a fast-charging graphite composite material includes:

[0042] (1) Artificial graphite (Shanghai Shanshan Technology Co., Ltd., QCG-X9) was transferred into a reaction chamber, and a gas mixture of concentrated nitric acid / hydrochloric acid (volume ratio 1:1) was introduced to etch its surface for 3 hours to obtain porous graphite; then, a hot press was used to press the porous graphite into blocks at a pressure of 3T and a temperature of 100℃ for 240 minutes to obtain blocky porous graphite (specific surface area 1.5m²). 2 / g).

[0043] (2) 5g of nano-tin metal powder was added to 100mL of carbon tetrachloride organic flux, and then 1g of sodium tripolyphosphate was added to obtain a 5% metal suspension (first suspension); 1g of ferric chloride was added to 20mL of propylene glycol propyl ether organic flux and dispersed evenly to obtain a 5% ferric chloride catalyst solution (second suspension); then, 100g of blocky porous graphite was transferred to the reaction chamber by gas atomization. Under an inert atmosphere and a vacuum of 500pa, the temperature was heated to 150℃. First, the metal suspension was atomized through gas path M and introduced into the reaction chamber for deposition for 30min; then, gas path M was stopped and gas path N was changed to atomize the ferric chloride catalyst solution and introduce catalyst gas for deposition to obtain metal / catalyst-doped graphite precursor material A.

[0044] (3) Precursor material A was transferred to a tube furnace. First, argon inert gas was introduced to purge the air from the tube. Then, methane carbon source gas was introduced, and carbonization was carried out at 950℃ for 3 hours. The mixture was then allowed to cool naturally to room temperature, cleaned with dilute hydrochloric acid, dried, and pulverized to obtain a metal-doped amorphous carbon-coated graphite composite material (hereinafter referred to as: graphite composite material). The SEM image of the obtained graphite composite material is shown below. Figure 1 .

[0045] Example 2

[0046] A method for preparing a fast-charging graphite composite material includes:

[0047] (1) Artificial graphite (Shanghai Shanshan Technology Co., Ltd., QCG-X9) was transferred into a reaction chamber, and a gas mixture of concentrated nitric acid / hydrochloric acid (volume ratio 1:1) was introduced to etch its surface for 1 hour. After washing with deionized water, porous graphite was obtained. Then, a hot press was used to press the porous graphite into blocks at a pressure of 1T and a temperature of 80℃ for 480 minutes to obtain blocky porous graphite (specific surface area 1.0 m²). 2 / g).

[0048] (2) 1g of nano-silver metal powder was added to 100mL of propylene glycol propyl ether organic flux and 0.5g of sodium hexametaphosphate dispersant to obtain a 1% metal suspension (first suspension); 0.5g of nickel chloride was added to 50mL of propylene glycol propyl ether organic flux and dispersed evenly to obtain a 1% nickel chloride catalyst solution (second suspension); then, 100g of blocky porous graphite was transferred to the reaction chamber by gas atomization. Under an inert atmosphere and a vacuum of 100pa, the temperature was heated to 200℃. First, the metal suspension was atomized through gas path M and introduced into the reaction chamber for deposition for 10min; then, gas path M was stopped and gas path N was changed to atomize the nickel chloride catalyst solution and introduce nickel chloride catalyst gas for deposition to obtain metal / catalyst-doped graphite precursor material A.

[0049] (3) The precursor material A is transferred to a tube furnace. First, argon inert gas is introduced to remove the air in the tube. Then, ethylene gas is introduced. The material is carbonized at 700℃ for 6 hours. After cooling to room temperature, it is washed with dilute hydrochloric acid, dried, and pulverized to obtain the metal and its amorphous carbon-doped amorphous carbon-coated graphite composite material (abbreviated as: graphite composite material).

[0050] Example 3

[0051] A method for preparing a fast-charging graphite composite material includes:

[0052] (1) Artificial graphite (Shanghai Shanshan Technology Co., Ltd., QCG-X9) was transferred into a reaction chamber, and a gas mixture of concentrated nitric acid / hydrochloric acid (volume ratio 1:1) was introduced to etch its surface for 6 hours. After washing with deionized water, porous graphite was obtained. Then, a hot press was used to press the porous graphite into blocks at a pressure of 5T and a temperature of 150℃ for 60 minutes to obtain blocky porous graphite (specific surface area 2m²). 2 / g).

[0053] (2) 10g of copper powder was added to 100mL of ethylene glycol propyl ether organic flux, followed by 2g of sodium pyrophosphate dispersant to obtain a 10% metal suspension (first suspension); 2g of cobalt chloride was added to 20mL of ethylene glycol propyl ether organic flux and dispersed evenly to obtain a 10% cobalt chloride catalyst solution (second suspension); then, 100g of blocky porous graphite was transferred to the reaction chamber by gas atomization. Under an inert argon atmosphere and a vacuum of 1000pa, the temperature was heated to 200℃. First, the metal suspension was atomized through gas path M and introduced into the reaction chamber for deposition for 60min; then, gas path M was stopped, and gas path N was changed to atomize the cobalt chloride catalyst solution and introduce catalyst gas for deposition to obtain metal / catalyst-doped graphite precursor material A.

[0054] (3) The precursor material A is transferred to a tube furnace. First, argon inert gas is introduced to remove the air in the tube. Then, ethane gas is introduced. The material is carbonized at 1100℃ for 1 hour. It is then cooled to room temperature naturally. The material is cleaned with dilute hydrochloric acid, dried, and pulverized to obtain the metal and its amorphous carbon-doped amorphous carbon-coated graphite composite material (abbreviated as: graphite composite material).

[0055] Comparative Example 1

[0056] Take 100g of the metal / catalyst-doped graphite precursor material A from step (2) of Example 1 and 5g of petroleum asphalt, mix them evenly in a ball mill, then transfer them to a carbonization furnace, and carbonize them at 750°C for 3 hours under an inert argon atmosphere. Then cool them down to room temperature under an argon atmosphere to obtain the metal and its amorphous carbon-doped amorphous carbon-coated graphite composite material (hereinafter referred to as: graphite composite material).

[0057] Comparative Example 2

[0058] The process is the same as steps (1) and (3) in Example 1, with the main difference being that the liquid phase method replaces the gas atomization method for preparing the metal / catalyst-doped graphite precursor material A. The main differences are:

[0059] Using the liquid phase method: 100g of blocky porous graphite, 100mL of 5% ferric chloride catalyst solution, and 100mL of 5% nano-tin metal suspension from step 1 of Example 1 were weighed and added to a high-pressure reactor. The reaction was carried out at 150℃ and 3MPa for 3h. After filtration, the mixture was vacuum dried at 80℃ for 24h to obtain metal / catalyst-doped graphite precursor material A. Other steps were the same as in Example 1, and a metal and its amorphous carbon-doped amorphous carbon-coated graphite composite material (hereinafter referred to as: graphite composite material) were prepared.

[0060] Physicochemical performance testing:

[0061] (1) SEM testing

[0062] The graphite composite material prepared in Example 1 was subjected to SEM testing, and the test results are shown in the attached figure. Figure 1 As shown in the figure, the graphite composite material exhibits a granular structure with a uniform size distribution, and its particle size is between (8-18) μm.

[0063] (2) Powder conductivity test

[0064] The electrical conductivity of the graphite composite materials in Examples 1-3 and Comparative Examples 1-2 was tested. The method for testing the electrical conductivity of the powder was to press the powder into a block structure on a powder compaction density meter under a pressure of 2T, and then use a four-probe tester to test the electrical conductivity of the powder. The test results are shown in Table 1.

[0065] (3) Tap density, specific surface area, and degree of graphitization

[0066] According to GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". The test results are shown in Table 1.

[0067] Table 1

[0068]

[0069] As shown in Table 1, the electrical conductivity and tap density of the graphite composite materials prepared in Examples 1-3 of this invention are significantly higher than those in the comparative example. This is because the embodiments used a gas atomization method to deposit highly conductive metal elements, thereby improving the material's electrical conductivity. Furthermore, the high density of the metal elements, deposited on the surface of porous graphite, increases the tap density. Simultaneously, the metal elements themselves have a catalytic effect, increasing the graphitization degree and specific surface area of ​​the material.

[0070] Button cell battery test

[0071] The graphite materials from Examples 1-3 and Comparative Examples 1-2 were assembled into coin cells A1, A2, A3, B1, and B2, respectively. The assembly method was as follows: a binder, conductive agent, and solvent were added to the negative electrode material, stirred to form a slurry, coated onto copper foil, and then dried and rolled to obtain the negative electrode sheet. The binder used was LA132 binder, the conductive agent was SP, the negative electrode material was the graphite material from Examples 1-3 and Comparative Examples 1-2, and the solvent was double-distilled water. The proportions of each component were: negative electrode material: SP: LA132: double-distilled water = 95g: 1g: 4g: 220mL; the electrolyte was LiPF6 / EC+DEC (LiPF6 concentration was 1.2mol / L, EC and DEC volume ratio was 1:1), the lithium metal sheet was used as the counter electrode, and the separator was a polyethylene (PE), polypropylene (PP), or polyethylene propylene (PEP) composite membrane. The button cell assembly was carried out in an argon-filled glove box. Electrochemical performance testing was conducted on a Wuhan Landian CT2001A battery tester, with a charge / discharge voltage range of 0.005V to 2.0V and a charge / discharge rate of 0.1C. The test results are shown in Table 2.

[0072] Table 2

[0073]

[0074] As can be seen from Table 2, the first discharge capacity and first charge-discharge efficiency of the lithium-ion battery using the composite negative electrode materials obtained in Examples 1-3 are significantly higher than those of the comparative example. This is because the metal compounds deposited by the gas atomization method have a catalytic effect, which reduces impedance and improves the material's intercalation and deintercalation capacity, thereby improving the material's discharge specific capacity and first efficiency. At the same time, the gas atomization method can reduce the irreversible capacity of the metal compounds deposited on the porous graphite surface and improve the first efficiency.

[0075] Soft-pack battery testing

[0076] Negative electrode sheets were prepared using the graphite composite materials from Examples 1-3 and Comparative Examples 1-2 as the negative electrode material. Ternary materials (LiNi) were also used. 1 / 3 Co 1 / 3 Mn 1 / 3 Using O2 as the positive electrode, a LiPF6 solution (solvent: EC+DEC, volume ratio 1:1, LiPF6 concentration 1.3 mol / L) as the electrolyte, and Celegard 2400 as the separator, 5Ah pouch cells A4, A5, A6 and B4, B5 were prepared. The cycle performance and rate performance of the pouch cells were then tested.

[0077] Cyclic performance test conditions: charge / discharge current 1C / 1C, voltage range 2.8-4.2V, 500 cycles. The initial DCR and post-cycle DCR of the battery were tested. Test results are detailed in Table 3.

[0078] Table 3

[0079]

[0080] As can be seen from Table 3, the pouch battery prepared by the graphite material of the present invention has better cycle performance than the comparative example. The reason is that, in terms of 1C / 1C rate cycle performance, the deposition of metal compounds on the porous graphite surface by gas atomization reduces surface defects and improves electronic conductivity, thereby reducing side reactions and DCR. At the same time, the metal compounds promote the insertion and extraction of lithium ions during charging and discharging, reduce impedance and improve the structural stability of the material, thereby improving cycle performance. In addition, the material of the example has a high specific surface area, which improves the liquid retention performance of the material and thus improves cycle performance.

[0081] Rate performance test conditions: charging rate: 1C / 3C / 5C / 8C, discharging rate: 1C; voltage range: 2.8-4.2V.

[0082] The test results are shown in Table 4.

[0083] Table 4

[0084]

[0085] As can be seen from Table 4, the soft-pack batteries prepared from the graphite materials in Examples 1-3 of this invention have a better constant current ratio. The reason is that the metal deposited on the surface of the material in the examples reduces its impedance and the amorphous carbon deposited in the vapor phase has a high density. At the same time, the deposited catalyst becomes carbon nanotube material after the carbon source is introduced, which further reduces the impedance and improves the constant current ratio.

[0086] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: A specific elemental metal is deposited in the pores and surface of bulk porous graphite using a gas-state atomization method, relying on its high electronic conductivity to reduce the impedance of the core graphite; simultaneously, the catalyst deposited on its surface acts as a catalyst during the carbonization stage and grows carbon nanotubes, further reducing impedance and improving fast-charging performance. The outer carbon nanotubes have a large specific surface area and form a network structure with amorphous carbon doping, improving the structural stability and cycle performance of the material. Furthermore, the gas-state atomization method for depositing metal and catalyst results in a thin deposition thickness, having little impact on the battery's energy density, and the entire process is controllable and more efficient. Based on this, the fast-charging negative electrode material prepared by the above method has advantages such as low impedance, high energy density, and high structural stability and cycle performance.

[0087] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a fast-charging negative electrode material, characterized in that, The preparation method of the fast-charging negative electrode material includes: Bulk porous graphite is obtained, wherein the specific surface area of ​​the bulk porous graphite is 1-2 m². 2 / g; Under inert atmosphere and vacuum conditions, a first suspension containing a metallic element is atomized and then deposited on the bulk porous graphite to obtain a metal layer, wherein the metallic element is selected from one or more of tin, silver and copper. The catalyst-containing second suspension is atomized and then deposited a second time on the metal layer to obtain a metal / catalyst-doped graphite precursor material; the catalyst is selected from one or more of ferric chloride, nickel chloride, and cobalt chloride; The metal / catalyst-doped graphite precursor material is carbonized to obtain the fast-charging negative electrode material; The carbonization process includes reacting a carbon-based gas with the metal / catalyst-doped graphite precursor material to obtain the fast-charging negative electrode material.

2. The method for preparing the fast-charging negative electrode material according to claim 1, characterized in that, The first suspension comprises: the metal element, an organic solvent, and a dispersant, wherein the content of the metal element in the first suspension is 1 to 10 wt%.

3. The method for preparing the fast-charging negative electrode material according to claim 2, characterized in that, At least one of the following conditions must be met: (1) The particle size of the metallic element is 500-2000 nm; (2) The organic solvent is selected from one or more of carbon tetrachloride, benzene, acetone, propylene glycol propyl ether, and ethylene glycol propyl ether; (3) The dispersant is selected from one or more of sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, and polyethylene glycol-type polyols.

4. The method for preparing the fast-charging negative electrode material according to any one of claims 1 to 3, characterized in that, The second suspension comprises the catalyst and an alcohol solvent, and the content of the catalyst in the second suspension is 1-10 wt%. The alcohol solvent is selected from one or more of methanol, 1,4-butanediol, isopropanol and 1,3-butanediol.

5. The method for preparing the fast-charging negative electrode material according to claim 1, characterized in that, During the first deposition process, the vacuum level was 100–1000 Pa, the temperature was 100–200 °C, and the deposition time was 10–60 min. The deposition time for the second deposition process is 30–300 min.

6. The method for preparing the fast-charging negative electrode material according to claim 1, characterized in that, The carbon-based gas is selected from one or more of methane, ethane, ethylene, and acetylene.

7. The method for preparing the fast-charging negative electrode material according to claim 1, characterized in that, The carbonization process is carried out at a temperature of 700–1100℃ for 1–6 hours.

8. The method for preparing the fast-charging negative electrode material according to claim 2, characterized in that, The weight ratio of the blocky porous graphite, the metallic element, the dispersant, and the catalyst is 100:(1-10):(0.5-2):(0.5-2).

9. A fast-charging negative electrode material, characterized in that, The fast-charging negative electrode material is prepared by any one of claims 1 to 8.

10. A lithium-ion battery, comprising a negative electrode material, characterized in that, The negative electrode material includes the fast-charging negative electrode material as described in claim 9.

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