Preparation method of fast-charging negative electrode material, fast-charging negative electrode material and lithium ion battery

Abstract

This application provides a method for preparing a fast-charging negative electrode material, the fast-charging negative electrode material, and a lithium-ion battery. The method includes mixing and reacting artificial graphite, an oxidant, an intercalating agent, and a fluorine-containing dopant to obtain micro-expanded graphite; adding a catalyst to the micro-expanded graphite and graphitizing it to obtain a graphite material; depositing lithium salt on the surface of the graphite material, carbonizing and dispersing it to obtain the fast-charging negative electrode material. Compared to existing technologies, this application can simultaneously dope the micro-expanded graphite using a fluorine-containing dopant, thereby improving the electronic conductivity of the material. The micro-expanded graphite can expand the lithium-ion intercalation / extraction pathway, improve the rate capability of the material, and the deposition of lithium salt can increase the ionic conductivity, thus improving the fast-charging performance of the material.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery materials, specifically to the preparation method of fast-charging negative electrode materials, fast-charging negative electrode materials, and lithium-ion batteries. Background Technology

[0002] Common lithium-ion battery anode materials are typically made of artificial graphite. During charging and discharging, lithium-ion intercalation and deintercalation usually occur between the graphite layers. Since the interlayer spacing of graphite is usually smaller than the lithium-ion particle size, the anode material expands by about 25% due to the movement of lithium ions between the layers, negatively impacting the stability of the lithium-ion battery. Furthermore, the current interlayer intercalation and deintercalation paths for lithium ions are generally long, resulting in a slower lithium-ion diffusion rate and reducing the rate performance of the anode material.

[0003] Modifying the carbon layer structure, improving isotropy, and reducing the sheet size can improve the lithium-ion insertion and extraction pathways. Therefore, during the preparation of anode materials, engineers typically coat graphite with multiple layers of amorphous carbon and dope them with various elements to improve the material's isotropy and increase the lithium-ion diffusion rate, thereby enhancing the material's power performance. However, these methods are very complex to prepare and do not effectively improve the material's ionic conductivity, thus their improvement on anode material performance remains limited. Summary of the Invention

[0004] This application mainly provides a method for preparing fast-charging anode materials, fast-charging anode materials, and lithium-ion batteries, which can improve the lithium-ion insertion / extraction pathway and ionic conductivity of the materials, thereby improving the rate performance of the materials.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a method for preparing a fast-charging negative electrode material, including mixing artificial graphite, oxidant, intercalating agent and fluorine-containing dopant to react and obtain micro-expanded graphite; adding a catalyst to the micro-expanded graphite and graphitizing it to obtain a graphite material; depositing lithium salt on the surface of the graphite material, carbonizing and dispersing it to obtain a fast-charging negative electrode material.

[0006] In one specific embodiment, the fluorine-containing dopant includes at least one of cobalt fluoride, ammonium fluoride, ammonium hydrofluoride, nickel fluoride, and iron fluoride.

[0007] In one specific embodiment, the oxidant includes at least one selected from peracetic acid, benzoyl peroxide, cyclohexanone peroxide, tert-butanol peroxide, and methyl ethyl ketone peroxide.

[0008] In one specific embodiment, the intercalating agent includes at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium hydrogen sulfate, and N,N-dimethyldodecylamine.

[0009] In one specific embodiment, the catalyst includes at least one selected from ferrocene, nickel dicene, cobalt acetate tetrahydrate, and bismuth 2-ethylhexanoate.

[0010] In one specific embodiment, the deposition of lithium salt on the surface of the graphite material includes heating the graphite material to 800-1500°C in a reaction vessel with a vacuum of 0.1-10 Pa; introducing lithium source gas into the reaction vessel at a flow rate of 10-100 SCCM; and performing deposition for 30-300 minutes.

[0011] In one specific embodiment, the lithium source gas includes at least one of lithium oxide, lithium tetraborate, lithium tert-pentylene oxide, and lithium thioethoxylate.

[0012] In one specific embodiment, the step of adding a catalyst to the micro-expanded graphite and graphitizing it to obtain graphite material includes mixing the micro-expanded graphite with the catalyst and heating it until the catalyst melts, pressing it into blocks under a pressure of 10-30 MPa to obtain a first mixture; heating the first mixture to 1500-2000°C to perform a graphitization process for 12-48 hours, and then cooling it to room temperature and breaking it up to obtain the graphite material.

[0013] To solve the above-mentioned technical problems, another technical solution adopted in this application is to provide a fast-charging negative electrode material, which is prepared by the method described in any one of the above-mentioned methods.

[0014] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide a lithium-ion battery, the lithium-ion battery including a negative electrode sheet, the negative electrode sheet including a fast-charging negative electrode material prepared by the method described in any one of the above-mentioned methods.

[0015] The beneficial effects of this application are as follows: Unlike existing technologies, this application provides a method for preparing fast-charging negative electrode materials, the fast-charging negative electrode material itself, and a lithium-ion battery. It utilizes oxidants and intercalating agents to prepare micro-expanded graphite, reducing material expansion and improving lithium-ion insertion / extraction pathways. Furthermore, it employs fluorine-containing dopants to enhance the electronic conductivity of the material, and deposits lithium salts on the surface of the micro-expanded graphite to further improve the ionic conductivity, thereby improving the rate capability. This significantly enhances the fast-charging performance of the material. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1This is a SEM schematic diagram of an embodiment of the fast-charging negative electrode material provided in this application;

[0018] Figure 2 This is a schematic flowchart of an embodiment of the preparation method of the fast-charging negative electrode material provided in this application. Detailed Implementation

[0019] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0020] The terms "first," "second," and "third" in this application are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. A process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0021] In this document, the term "implementation" means that a specific feature, structure, or characteristic described in connection with an implementation may be included in at least one implementation of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same implementation, nor is it a separate or alternative implementation mutually exclusive with other implementations. It will be explicitly and implicitly understood by those skilled in the art that the implementations described herein can be combined with other implementations.

[0022] Please see Figure 2 , Figure 2 This is a schematic flowchart of an embodiment of the preparation method of the fast-charging negative electrode material provided in this application. It should be noted that if substantially the same result is obtained, this embodiment is not necessarily identical. Figure 2 The illustrated process sequence is limited. For example... Figure 2 As shown, this embodiment includes:

[0023] S100: Artificial graphite, oxidant, intercalating agent and fluorine-containing dopant are mixed and reacted to obtain micro-expanded graphite.

[0024] Artificial graphite, an oxidant, an intercalating agent, and a fluorine-containing dopant are mixed uniformly and then reacted to obtain micro-expanded graphite. The oxidant and intercalating agent are used to create pores in the artificial graphite, thereby preparing micro-expanded graphite to reduce material expansion. In this step, a fluorine-containing dopant is added to the material to utilize the fluorine element to improve the electronic conductivity and enhance the material's properties.

[0025] Optionally, the fluorine-containing dopant may include at least one of cobalt fluoride, ammonium fluoride, ammonium hydrofluoride, nickel fluoride, and iron fluoride. When the fluorine-containing dopant is a fluoride, the fluorine element in the fluorine-containing dopant has good electrical conductivity. When the fluorine-containing dopant participates in the reaction, it can dope fluorine element between the layers of artificial graphite, thereby improving the electronic conductivity of the material and helping to improve the material performance.

[0026] Optionally, the oxidant may include at least one of peracetic acid, benzoyl peroxide, cyclohexanone peroxide, tert-butanol peroxide, and methyl ethyl ketone peroxide. When used as an oxidant, these organic peroxides can generate oxygen free radicals during carbonization. These oxygen free radicals can undergo cross-linking reactions with carbon, creating pores in the artificial graphite. These pores can then be used to improve the lithium storage capacity and kinetic performance of the material. However, more common oxidants such as hydrogen peroxide, concentrated sulfuric acid, and concentrated nitric acid are too strong and can form hydroxyl and / or carboxyl groups on the surface of the artificial graphite during the reaction. These groups readily react with the electrolyte, posing a risk of reducing the initial efficiency of the battery.

[0027] Optionally, the intercalating agent may include at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium hydrogen sulfate, and N,N-dimethyldodecylamine. The intercalating agent used in this embodiment contains nitrogen, and ammonia gas is released during step S100. This ammonia gas is then used to intercalate and expand the layered structure of the artificial graphite, and nitrogen-containing compounds remain in the generated micro-expanded graphite. These nitrogen-containing compounds can then be used to further achieve nitrogen doping, which is beneficial for improving the electronic conductivity of the material.

[0028] Optionally, the mass ratio of artificial graphite, oxidant, intercalating agent, and fluorine-containing dopant can be artificial graphite: oxidant: intercalating agent: fluorine-containing dopant = 100:13~30:100~500:1~10. Mixing these four components thoroughly before preparing micro-expanded graphite facilitates the reaction.

[0029] Optionally, the reaction temperature for preparing micro-expanded graphite can be 25–80°C, and the reaction time can be 30–300 minutes. After the reaction, the product can be washed with deionized water, filtered, and the filter residue can be vacuum dried to obtain micro-expanded graphite with less impurities, thereby reducing the probability of subsequent side reactions.

[0030] S200: Adding a catalyst to micro-expanded graphite and graphitizing it to obtain graphite material.

[0031] A catalyst is added to the micro-expanded graphite obtained in step S100, and the graphitization process is carried out under the action of the catalyst to obtain a graphite material. During the graphitization process, the catalyst can further promote the formation of a porous structure in the micro-expanded graphite, thereby improving the lithium-ion intercalation / extraction pathway and enhancing the rate performance of the material.

[0032] Optionally, the catalyst may include at least one of ferrocene, nickel ferrocene, cobalt acetate tetrahydrate, and bismuth 2-ethylhexanoate. Such organic catalysts can undergo reduction during graphitization, producing gases and catalytically active elemental metals, which can have a certain pore-forming effect. Furthermore, the newly reduced elemental metals are more reactive than those used directly as catalysts, thus better catalyzing graphitization. Moreover, compared to inorganic catalysts, organic catalysts have advantages such as lower impurity content, lower boiling points, and easier catalysis, making them better suited to the requirements and reaction environment of the graphitization process.

[0033] Optionally, the mass ratio of micro-expanded graphite to catalyst can be 100:1 to 5. Before graphitization, the micro-expanded graphite and catalyst can be mixed in a ball mill to facilitate the reaction.

[0034] In one embodiment, step S200 may specifically involve: mixing micro-expanded graphite with a catalyst and heating the mixture until the catalyst melts, then pressing it into blocks under a pressure of 10–30 MPa to obtain a first mixture. The first mixture is then heated to 1500–2000°C for a graphitization process of 12–48 hours, followed by cooling to room temperature and dispersing to obtain a graphite material.

[0035] The catalyst melting temperature range can be 180–250℃. Melting the catalyst allows for a more uniform distribution of the catalyst within the micro-expanded graphite, which is beneficial for catalytic graphitization. Simultaneously, the molten catalyst can enhance the bonding force between the micro-expanded graphites during the briquetting process. Briquetting before graphitization increases the loading capacity during graphitization and also ensures more uniform heating, thereby improving the quality of the graphitization process.

[0036] S300: Lithium salt is deposited on the surface of graphite material, carbonized and dispersed to obtain a fast-charging negative electrode material.

[0037] Lithium salt is deposited on the surface of the graphite material obtained in step S200, followed by carbonization and dispersion of the graphite material to obtain the desired fast-charging anode material. By depositing lithium salt on the surface of the graphite material, the ionic conductivity of the material is improved, thereby significantly enhancing the fast-charging performance of the obtained fast-charging anode material. It can also reduce the irreversible capacity of the fast-charging anode material, thereby improving the first-cycle efficiency.

[0038] In one embodiment, the process of depositing lithium salts on the surface of graphite material can be as follows: graphite material is placed in a reaction vessel, a vacuum is drawn to a degree of 0.1–10 Pa, and the graphite material is heated to 800–1500°C. Then, lithium source gas is introduced into the reaction vessel at a flow rate of 10–100 SCCM for deposition for 30–300 minutes. This embodiment utilizes atomic vapor deposition to deposit lithium salts on the surface of graphite material, which has advantages such as good deposition uniformity, good consistency, process controllability, and high density of the deposited layer. Therefore, relying on the high conductivity of lithium salt ions, the fast-charging performance of the material can be improved.

[0039] Optionally, the lithium source gas may include at least one of lithium oxide, lithium tetraborate, lithium tert-pentylene oxide, and lithium thioethoxylate. These lithium compounds are readily available, and under reduced pressure, they can vaporize at appropriate temperatures to form a lithium source gas for use in atomic vapor deposition.

[0040] Optionally, during the depressurization and heating process before introducing the lithium source gas, the atmosphere in the reactor can be a mixture of hydrogen and inert gas. After graphitization in step S200, the surface of the graphite may have residual oxidizing chemical groups, which leads to increased material impedance. Hydrogen can reduce the oxidizing chemical groups, thereby removing the chemical groups from the graphite surface and maintaining the performance of the graphite material.

[0041] The volume ratio of hydrogen to inert gas can be 1:9.

[0042] Using the method provided in this embodiment, oxidants, intercalating agents, and fluorine-containing dopants work together to form oxygen-containing groups, expand the interlayer spacing of the material, and improve electronic conductivity. During the graphitization process, a catalyst is used to promote the formation of pores in the material, improving the lithium-ion insertion and extraction pathway. Then, lithium salts are deposited on the surface of the graphite material. Taking advantage of the high ionic conductivity of lithium salts, the fast-charging performance of the material is improved. All steps work together to prepare a fast-charging negative electrode material with good rate performance and excellent ionic conductivity, thus achieving an effective performance improvement.

[0043] This application also provides a fast-charging anode material. This fast-charging anode material can be prepared using the preparation method provided in any of the above embodiments. Specifically, the interlayer spacing of this fast-charging anode material is 0.3356–0.3366 nm, its specific capacity is greater than or equal to 355 mAh / g, and its initial efficiency is greater than or equal to 95%. Under favorable lithium-ion insertion / extraction pathways, it exhibits good specific capacity and initial efficiency, and can be used to prepare anode sheets for lithium-ion batteries.

[0044] This application also provides a lithium-ion battery. The lithium-ion battery includes a negative electrode sheet, which may include a fast-charging negative electrode material prepared using the above-described preparation method. During the preparation of this fast-charging negative electrode material, it is doped with a fluorine-containing dopant, thus improving electronic conductivity. Simultaneously, it utilizes micro-expanded graphite as the core of the material, exhibiting low expansion. Furthermore, lithium salt is deposited on the surface of the material, which improves the ionic conductivity, thereby enhancing both the rate performance and fast-charging performance of the fast-charging negative electrode material.

[0045] The following Examples 1-3 prepared fast-charging anode materials that can be applied to lithium-ion batteries.

[0046] Example 1

[0047] Step S1: Mix 100g of artificial graphite, 20g of peracetic acid, 300g of hexadecyltrimethylammonium bromide and 5g of cobalt fluoride evenly, then react at 50℃ for 150min, filter, wash with deionized water, and dry the resulting filter residue under vacuum at 80℃ for 24h to obtain micro-expanded graphite.

[0048] Step S2: Add 100g of micro-expanded graphite and 3g of ferrocene to a ball mill and mix. Then heat to 200℃ to melt and press into blocks at a pressure of 20MPa for 2 hours. Then heat the resulting material to 1800℃ for low-temperature graphitization for 24 hours, cool to room temperature, and break it up to obtain graphite material.

[0049] Step S3: Place the graphite material in a vacuum reactor with a vacuum degree of 1 Pa. Under a reducing atmosphere of hydrogen mixed atmosphere (volume ratio, hydrogen:argon = 1:9), heat to 1200℃, then introduce lithium oxide gas and deposit for 120 min at a flow rate of 50 SCCM. After that, grade to obtain fast-charging negative electrode material.

[0050] Example 2

[0051] Step S1: Mix 100g of artificial graphite, 10g of benzoyl peroxide, 100g of hexadecyltrimethylammonium chloride and 1g of ammonium fluoride evenly, then react at 25℃ for 300min, filter, wash with deionized water, and dry the resulting filter residue under vacuum at 80℃ for 24h to obtain micro-expanded graphite.

[0052] Step S2: Add 100g of micro-expanded graphite and 1g of nickel dicene to a ball mill and mix. Then heat to 180℃ to melt and press into blocks at a pressure of 30MPa for 3h. Then heat the resulting material to 1500℃ for low-temperature graphitization for 48h, cool to room temperature, and break it up to obtain graphite material.

[0053] Step S3: Place the graphite material in a vacuum reactor with a vacuum degree of 0.1 Pa. Under a reducing atmosphere of mixed hydrogen (volume ratio of hydrogen:argon = 1:9), heat to 800°C, then introduce lithium tetraborate gas and deposit for 300 min at a flow rate of 10 SCCM. After classification, obtain the fast-charging negative electrode material.

[0054] Example 3

[0055] Step S1: Mix 100g of artificial graphite, 30g of cyclohexanone peroxide, 500g of hexadecyltrimethylammonium hydrogen sulfate and 10g of nickel fluoride evenly, then react at 80℃ for 30min, filter, wash with deionized water, and vacuum dry the resulting filter residue at 80℃ for 24h to obtain micro-expanded graphite.

[0056] Step S2: Add 100g of micro-expanded graphite and 5g of cobalt acetate tetrahydrate to a ball mill and mix. Then heat to 250℃ to melt and press into blocks at a pressure of 10MPa for 3h. Then heat the resulting material to 2000℃ for low-temperature graphitization for 12h, cool to room temperature, and break it up to obtain graphite material.

[0057] Step S3: Place the graphite material in a vacuum reactor with a vacuum degree of 10 Pa. Under a reducing atmosphere of hydrogen mixed atmosphere (volume ratio, hydrogen:argon = 1:9), heat to 1500℃, then introduce tert-pentyl lithium oxide gas and deposit for 30 min at a flow rate of 100 SCCM. After that, disperse to obtain the fast-charging negative electrode material.

[0058] Two comparative examples are provided below for comparison with the embodiments of the preparation method of the fast-charging negative electrode material described in this application.

[0059] Comparative Example 1: Unlike Example 1, step S1 was omitted. Instead, in step S2, artificial graphite was used instead of micro-expanded graphite to prepare the graphite composite anode material. Other conditions and operations were the same as in Example 1.

[0060] Comparative Example 2: Unlike Example 1, lithium oxide gas was not introduced in step S3, i.e., lithium salt was not deposited by atomic vapor deposition to prepare graphite composite anode material. Other conditions and operations were the same as in Example 1.

[0061] The materials prepared in the above embodiments and comparative examples were subjected to the following performance tests.

[0062] The tests include:

[0063] (1) SEM (Scanning Electron Microscopy) test

[0064] The fast-charging negative electrode material prepared in Example 1 was subjected to SEM testing, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the material has a single-particle structure with a small amount of fine powder on the surface, with a particle size of about 10μm.

[0065] (2) Physicochemical performance testing

[0066] The conductivity, specific surface area, and degree of graphitization of the fast-charging anode materials in Examples 1-3 and the graphite composite anode materials in Comparative Examples 1 and 2 were tested according to the test methods in standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". Simultaneously, the D002 and D004 of the materials were calculated using XRD (X-ray diffraction), and the OI value of the powder was also calculated. The test results are shown in Table 1.

[0067] Table 1

[0068]

[0069] As can be seen from Table 1, the conductivity and OI value of the fast-charging negative electrode materials prepared in Examples 1 to 3 are significantly better than those of the comparative examples. This is because the doping of lithium salt on the surface of the material increases the ionic conductivity of the material, while the doping of metal fluoride in the core improves the electronic conductivity of the material and reduces the OI value of the powder.

[0070] (3) Button cell battery test

[0071] The fast-charging negative electrode materials prepared in Examples 1-3 and the graphite composite negative electrode materials in Comparative Examples 1 and 2 were assembled into coin cells according to the following method: The fast-charging negative electrode materials in Examples 1-3 and the graphite composite negative electrode materials prepared in Comparative Examples 1 and 2 were used as negative electrodes and assembled into coin cells with lithium sheets, electrolytes, and separators in a glove box with argon and water contents both below 0.1 ppm. The separator was Celegard 2400; the electrolyte was a LiPF6 solution with a LiPF6 concentration of 1 mol / L, and the solvent was a mixed solution obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DMC) in a weight ratio of 1:1.

[0072] The fabricated coin cells were tested using a blue-light tester. The test conditions were: 0.1C charge-discharge rate, voltage range of 0.005-2V, 3 cycles, followed by testing the discharge capacity at 1C. The 1C / 0.1C rate performance and cycle performance (25±3℃, 0.2C / 0.2C, 100 cycles) were calculated. The test results are shown in Table 2.

[0073] Table 2

[0074]

[0075] As shown in Table 2, the coin cells using the fast-charging negative electrode materials of Examples 1-3 exhibit significantly higher discharge specific capacity, initial efficiency, and rate performance than the coin cells using the graphite composite negative electrode materials of Comparative Examples 1 and 2. The experimental results indicate that this is because coating the material surface with lithium salt reduces its irreversible capacity and improves initial efficiency, while the use of micro-expanded graphite reduces expansion.

[0076] (4) Performance testing of pouch batteries

[0077] Using the fast-charging negative electrode materials of Examples 1-3 and the graphite composite negative electrode materials of Comparative Examples 1 and 2 as negative electrode active materials, and the positive electrode active material ternary material (LiNi) 1 / 3 Co 1 / 3 Mn 1 / 3 O2), electrolyte, and separator are assembled into a 5Ah pouch battery.

[0078] The separator was Celegard 2400, and the electrolyte was a LiPF6 solution (a 1:1 volume ratio of EC and DEC, with a LiPF6 concentration of 1.1 mol / L). The fabricated pouch cell was tested for cycle and rate performance; the results are detailed in Table 2.

[0079] 4.1 Cyclic performance:

[0080] The battery's 500-cycle performance was tested at a charge / discharge rate of 1C / 1C, a voltage range of 2.8V-4.2V, and a temperature of 25±3℃; see Table 2 for details.

[0081] Table 2

[0082] Example 500-week retention rate Initial cycle DCR(mΩ) Example 1 93.6％ 8.98 Example 2 93.1％ 9.45 Example 3 94.2％ 8.01 Comparative Example 1 91.6％ 10.12 Comparative Example 2 90.2％ 12.87

[0083] As can be seen from Table 2, the cycle performance of the fast-charging anode material in the embodiment is significantly better than that of the graphite composite anode material in the comparative embodiment. This is because the fast-charging anode material in the embodiment has low expansion and high powder conductivity, which improves the lithium-ion transport rate during charging and discharging and thus improves cycle performance.

[0084] 4.2 HPPC Test:

[0085] Test procedure: 1C CC to 4.2V, CV to 0.05C → Rest for 30min → 1C DC for 3min → Rest for 30min → 4C DC for 10s → Rest for 40s → 3C CC for 10s → Repeat step 10-15 for 10% DOD (cycle 1 times). Test the DCR of charging at different SOCs (5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%). See Table 3 for details.

[0086] Table 3

[0087]

[0088]

[0089] As can be seen from Table 3, the DCR of the fast-charging negative electrode material in the embodiment is lower than that of the graphite composite negative electrode material in the comparative embodiment. The reason is that the fast-charging negative electrode material in the embodiment is doped with a fluorine-containing dopant with high electronic conductivity and coated with lithium salt in the shell, which can improve the electronic conductivity and ionic conductivity of the fast-charging negative electrode material, and improve the isotropy of the material by using a low OI value, thereby reducing the material impedance and improving the rate performance.

[0090] The above description is only a partial embodiment of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or directly or indirectly applied to other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A method for preparing a fast-charging negative electrode material, characterized by, include: Micro-expanded graphite is obtained by mixing artificial graphite, oxidant, intercalating agent and fluorine dopant and reacting them. A catalyst was added to the micro-expanded graphite and graphitized to obtain a graphite material; Lithium salt is deposited on the surface of the graphite material, carbonized, and dispersed to obtain the fast-charging negative electrode material; The deposition of lithium salt on the surface of the graphite material includes: The graphite material is heated to 800-1500°C in a reaction vessel with a vacuum of 0.1-10 Pa. Lithium source gas is introduced into the reactor at a flow rate of 10~100 SCCM for deposition for 30~300 minutes. 2.The method of claim 1, wherein the method is characterized by, The fluorine-containing dopant includes at least one of cobalt fluoride, ammonium fluoride, ammonium hydrofluoride, nickel fluoride, and iron fluoride.

3. The method for preparing the fast-charging negative electrode material according to claim 1, characterized in that, The oxidizing agent includes at least one of peracetic acid, benzoyl peroxide, cyclohexanone peroxide, tert-butanol peroxide, and methyl ethyl ketone peroxide. 4.The method of claim 1, wherein the method is characterized by, The intercalating agent includes at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium hydrogen sulfate, and N,N-dimethyldodecylamine. 5.The method of claim 1, wherein the method is characterized by, The catalyst includes at least one of ferrocene, nickel calcitonin, cobalt acetate tetrahydrate, and bismuth 2-ethylhexanoate. 6.The method of claim 1, wherein the method is characterized by, The lithium source gas includes at least one of lithium oxide, lithium tetraborate, lithium tert-pentylene oxide, and lithium thioethoxylate. 7.The method of claim 1, wherein the method is characterized by, The process of adding a catalyst to the micro-expanded graphite and graphitizing it to obtain the graphite material includes: The micro-expanded graphite is mixed with the catalyst and heated until the catalyst melts. The mixture is then pressed into blocks under a pressure of 10-30 MPa to obtain a first mixture. The first mixture is heated to 1500~2000℃ for a graphitization process of 12~48 hours, then cooled to room temperature and dispersed to obtain the graphite material.

8. A fast-charging anode material, characterized in that, Prepared using the preparation method of the fast-charging negative electrode material according to any one of claims 1 to 7; The fast-charging negative electrode material has an interlayer spacing of 0.3356~0.3366nm, a specific capacity of ≥355mAh / g, and an initial efficiency of ≥95%.

9. A lithium-ion battery, characterized by It includes a negative electrode sheet, wherein the negative electrode sheet includes the fast-charging negative electrode material as described in claim 8.

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