Artificial graphite negative electrode material of lithium ion battery, preparation method of artificial graphite negative electrode material and lithium ion solid-state battery

Abstract

The invention discloses a lithium ion battery artificial graphite negative electrode material, a preparation method thereof and a lithium ion solid-state battery, and belongs to the technical field of lithium ion solid-state batteries. Carrying out flash evaporation Joule heating on the pretreated carbon source material in an inert atmosphere, then rapidly cooling to obtain a graphitized intermediate, and screening, washing and drying the graphitized intermediate; mixing and reacting the graphitized intermediate with strong acid under an ice bath condition, and oxidizing and expanding the graphitized intermediate to obtain expanded graphite; and mixing the expanded graphite with mercaptan acetic acid and ethyl acetate, adding a catalyst, and reacting for a certain time to obtain the artificial graphite negative electrode material of the lithium ion battery. According to the invention, by introducing a flash Joule pulse graphitization technology, sulfur-oxygen dual-function synergistic modification and structure-performance integrated design, three technical bottlenecks of a traditional artificial graphite negative electrode material are systematically solved: the rate capability is limited, the interface stability is poor and the volume expansion is obvious.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion solid-state batteries, and more specifically, relates to an artificial graphite negative electrode material for lithium-ion batteries, a preparation method thereof, and a lithium-ion solid-state battery. Background Art

[0002] Lithium-ion batteries have become core energy storage devices in portable electronic devices and electric vehicles due to their high energy density, long cycle life and environmentally friendly properties. As one of the key factors determining battery performance, artificial graphite is the mainstream material due to its excellent physical and chemical stability and cycle performance. However, existing artificial graphite anode materials still face three major technical bottlenecks, which limit their rate performance: limited by the hysteresis of lithium ion diffusion kinetics (diffusion coefficient is about 10 -10 ~10 - 12 cm 2 / s), which makes it difficult to meet the needs of high-power charging and discharging; insufficient interface compatibility: frequent chemical / electrochemical side reactions with sulfide electrolytes lead to poor stability of the solid electrolyte interface (SEI) film, causing capacity decay and safety hazards; significant volume expansion: during the lithium ion insertion / deinsertion process, the volume change rate between graphite layers can reach 10%~13%, which can easily cause pulverization of the electrode structure and mechanical failure.

[0003] To address these issues, existing technologies primarily optimize through two strategies: chemical functionalization and structural regulation. For example, patent CN116062745A employs a natural / artificial graphite composite strategy, improving rate performance through the polymerization of needle coke and spherical graphite. However, its granulation process suffers from insufficient efficiency and particle uniformity, resulting in poor batch stability. Patent CN114940495A reduces resistance through densification with a coating agent, but excessive densification can inhibit lithium-ion transport, necessitating repeated optimization of process parameters to balance conductivity and ion mobility.

[0004] The common limitations of current modification technologies are: single function orientation: such as only introducing oxygen-containing functional groups (hydroxyl, epoxy, etc.) to widen the interlayer spacing, or relying on thiol groups to enhance interfacial adhesion, which makes it difficult to synergistically improve ion diffusion and interface stability; high process complexity, and multi-step carbonization, coating and doping processes lead to a surge in energy consumption and costs; performance compromise effects, such as the micro-expansion effect alleviates volume expansion but may sacrifice the material's tap density and energy density. Summary of the Invention

[0005] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0006] In order to achieve these purposes and other advantages according to the present invention, the present invention provides a method for preparing an artificial graphite negative electrode material for a lithium ion battery, comprising the following steps: Step A, pretreating the carbon source material; Step B: flash Joule heating the pretreated carbon source material under an inert atmosphere, followed by rapid cooling to obtain a graphitized intermediate, and screening, washing, and drying the graphitized intermediate; Step C: mixing the graphitized intermediate with a strong acid under ice bath conditions to cause oxidation and expansion of the graphitized intermediate to obtain expanded graphite; Step D: Mix expanded graphite with mercaptoacetic acid and ethyl acetate, add a catalyst, and react for a certain period of time to obtain an artificial graphite negative electrode material for a lithium ion battery. The reaction process of using mercaptoacetic acid to modify expanded graphite in this step is as follows: Graphite-O-Graphite+HS-CH2-COOH→Graphite-S-CH2-COOH+Graphite-OH Graphite-OH+HS-CH2-COOH→Graphite-O-CO-CH2-SH; Under the catalytic action of the catalyst, the thiol group (-SH) in the mercaptoacetic acid molecule acts as a nucleophilic reagent to attack the active groups (such as hydroxyl, carboxyl, etc.) on the surface of expanded graphite. The thiol group (-SH) of the mercaptoacetic acid reacts with the epoxy group (Graphite-O-Graphite) on the graphite surface to form a sulfide bond (CSC). During the reaction, the carboxyl group of thiolacetic acid may further react with other groups on the graphite surface to form a more stable ester bond (-O-CO-).

[0007] Preferably, in step A, the method for pretreating the carbon source material specifically includes: grinding the carbon source material into powder, and controlling the powder D50 particle size within the range of 4 to 15 μm; heating to 1000 to 1200° C. under an inert gas atmosphere, and keeping the temperature for 4 to 6 hours to remove impurities and improve the purity and reactivity of the carbon source material.

[0008] Preferably, in step A, the grinding method is specifically: using high-energy ball milling to crush the carbon source material to D50 = 4-8 μm, with a ball-to-material ratio of 10:1, a ball milling speed of 300-600 rpm, and a ball milling time of 2-6 h.

[0009] Preferably, in step A, the carbon source material includes one or more of petroleum coke, needle coke, and asphalt.

[0010] Preferably, in step B, argon is used as the inert atmosphere, and 5 vol% hydrogen is added to the argon. The purpose of adding hydrogen is to reduce oxygen defects on the surface of the carbon source material and reduce the grain boundary resistance (<0.1 Ω·cm); The pretreated carbon source material is flash-Joule heated using a bipolar pulse current, wherein the peak current of the bipolar pulse current is ≥8500A, the pulse width is 1-100ms, and the frequency is 1-100kHz; the heating temperature of the flash Joule heating is 2800-3200℃, and the holding time is 2-5min; The rapid cooling method includes one of liquid nitrogen jet quenching, supercritical CO2 cooling, forced air cooling, and radiation cooling; wherein the liquid nitrogen jet quenching cooling rate is greater than 1000°C / s; the graphitized intermediate structure La is greater than 100nm, and / or Lc is greater than 50nm, and / or the lattice defect density is less than 0.3%; Screening adopts pneumatic sorting technology, and sorting is carried out according to the particle size distribution of D10=8μm, D50=10~14μm, and D90=15μm; Drying adopts vacuum gradient drying, and the temperature is raised in stages, specifically, after heating to 50~60℃, keep warm for 1~2h, then heat to 100~120℃, keep warm for 1~2h, and finally heat to 160~200℃, keep warm for 1~2h, and the dynamic vacuum is 10 -3 Pa, the moisture content of the graphitized intermediate after drying is less than 0.1wt%.

[0011] Preferably, in step C, the strong acid is one or more of nitric acid, concentrated sulfuric acid, perchloric acid, chromic acid or chloric acid, the nitric acid concentration is 70-80%, the mass ratio of the graphitized intermediate to nitric acid is 1:5-10; and the oxidation expansion time is 5-20 hours.

[0012] Preferably, in step D, the mass ratio of the expanded graphite, mercaptoacetic acid, and ethyl acetate is 1:10-20:3-10, and the amount of the catalyst is 0.1%-1% of the mass of the expanded graphite.

[0013] Preferably, in step D, the expanded graphite is mixed with mercaptoacetic acid, and the reaction temperature after adding the catalyst is 50-70° C., and the reaction time is 4-6 hours; The catalyst is one or more of triethylamine, tributylamine, tripropylamine or tetramethylammonium hydroxide.

[0014] A lithium ion battery artificial graphite negative electrode material is prepared by the above-mentioned method for preparing the lithium ion battery artificial graphite negative electrode material.

[0015] A lithium-ion solid-state battery, whose negative electrode material is the above-mentioned artificial graphite negative electrode material for lithium-ion batteries.

[0016] The present invention has at least the following beneficial effects: The present invention systematically solves the three major technical bottlenecks of traditional artificial graphite negative electrode materials: rate performance, interface stability and volume expansion by introducing flash Joule pulse graphitization technology, sulfur-oxygen dual-functional synergistic modification and structure-performance integrated design. Specifically, the present invention completes high-efficiency and low-defect graphitization within 2-5 minutes, reduces energy consumption to below 8kWh / kg, and increases the lithium ion diffusion coefficient to 10 -9 cm 2 / s, significantly improving the high-rate charge and discharge capability of the battery; The thiol group forms a coordination bond with the metal center. During the sulfur-oxygen bifunctional modification process, the thiol group (-SH) in the thiol acetic acid can react with the metal ions (such as Li + This chemical interaction greatly enhances the adhesion between the graphite surface and the electrolyte, making the electrode surface more stable, effectively preventing adverse reactions between the electrolyte and the electrode material, and reducing the generation of by-products.

[0017] Moreover, the presence of thiol groups also plays a key role in stabilizing the solid electrolyte interface (SEI) film. The SEI layer is a very important component in lithium-ion batteries. It not only affects the initial coulombic efficiency of the battery, but also directly determines the cycle life and safety of the battery. The thiol group can optimize the composition structure of the SEI layer by interacting with the electrolyte molecules, making it more uniform and dense, thereby improving its mechanical strength and chemical stability. Experimental data show that after 1000 charge and discharge cycles, the capacity retention rate can still reach ≥92%, which shows that this method significantly improves the long-term cycle stability of the battery; Furthermore, the introduced oxygen-containing functional groups can produce a small but controllable expansion between the graphite layers. This process helps to alleviate the stress generated during lithium insertion and reduce the damage caused by volume changes to the electrode structure. This also promotes the rapid transmission of electrons and ions within the electrode. Structural optimization reduces the volume expansion rate to ≤5%, ensuring high energy density and long cycle life. Furthermore, the green and efficient preparation process enables the recycling of waste acid, reduces production costs, and complies with ESG standards, providing a revolutionary anode solution for the next generation of high-performance lithium-ion batteries.

[0018] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a rate performance diagram of the artificial graphite negative electrode material for lithium ion batteries prepared in Example 1 and Comparative Example 1 of the present invention; Figure 2 This is an SEM image of the artificial graphite negative electrode material for lithium-ion batteries prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0021] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof. Example 1: A method for preparing an artificial graphite negative electrode material for a lithium-ion battery comprises the following steps: Step A: Petroleum coke was selected as the carbon source and crushed to D50 = 5 μm by high-energy ball milling (ball-to-material ratio 10:1, rotation speed 400 rpm, time 4 h), and then heated to 1000 °C for pretreatment for 6 h.

[0022] Step B: Under an argon atmosphere, 5 vol% hydrogen was added and a bipolar pulse current (peak current of the bipolar pulse current was 10 kA, pulse width was 50 ms, and frequency was 10 Hz) was applied to raise the temperature of the carbon source to 3000°C and hold the temperature for 3 minutes to perform flash Joule heating on the pretreated carbon source to obtain a graphitized intermediate; Subsequently, the graphitized intermediate was rapidly cooled by liquid nitrogen jet quenching (cooling rate >1000°C / s), resulting in a graphitized intermediate with a lattice defect density of <0.3%. After pneumatic sorting, the graphitized intermediate had a D10 of 8 μm, a D50 of 12 μm, and a D90 of 15 μm. After washing, the dynamic vacuum degree is 10 -3 Under Pa conditions, the graphitized intermediate was first heated to 60°C, kept warm for 2 hours, then heated to 120°C, kept warm for 1 hour, and finally heated to 180°C, kept warm for 1 hour, and vacuum gradient drying was performed to reduce the moisture content of the graphitized intermediate to below 0.1wt%; Step C: Under ice bath conditions, the graphitized intermediate is mixed with 70% nitric acid in a mass ratio of 1:7, reacted for 10 hours, washed to neutrality, and then dried to obtain expanded graphite; Step D: Expanded graphite, mercaptoacetic acid, and ethyl acetate were mixed in a mass ratio of 1:15:5, triethylamine accounting for 0.5% of the mass of expanded graphite was added, and the mixture was reacted at 50°C for 6h, and vacuum dried to obtain an artificial graphite negative electrode material for a lithium ion battery. The SEM image of the artificial graphite negative electrode material prepared in this embodiment is as follows: Figure 2 As shown, Figure 2The SEM image shows that the artificial graphite negative electrode material prepared in this example has uniform micron-sized particles (D50=12μm) and a rough surface structure. The surface unevenness and local coating characteristics indicate that the sulfur-oxygen dual-functional modification effectively improves the lithium ion embedding active sites. Combined with the low lattice defect density (<0.3%) and physical bridging structure, the high rate performance and cycle stability of the material are guaranteed.

[0023] Example 2: A method for preparing an artificial graphite negative electrode material for a lithium-ion battery comprises the following steps: Step A: needle coke was selected as the carbon source and pulverized to D50 = 4 μm by high-energy ball milling (ball-to-material ratio 10:1, rotation speed 400 rpm, time 4 h), and then heated to 1000 °C for pretreatment for 6 h.

[0024] Step B: Under an argon atmosphere, 5 vol% hydrogen was added and a bipolar pulse current (peak current of the bipolar pulse current was 10 kA, pulse width was 50 ms, and frequency was 10 Hz) was applied to raise the temperature of the carbon source to 2800°C and hold the temperature for 5 minutes to perform flash Joule heating on the pretreated carbon source to obtain a graphitized intermediate; Subsequently, the graphitized intermediate was rapidly cooled by liquid nitrogen jet quenching (cooling rate > 1000°C / s), and the resulting graphitized intermediate had a lattice defect density of < 0.3%. After pneumatic sorting, the graphitized intermediate had D10 = 8 μm, D50 = 10 μm, and D90 = 15 μm. After washing, the dynamic vacuum degree is 10 -3 Under Pa conditions, the graphitized intermediate was first heated to 60°C, kept warm for 2 hours, then heated to 120°C, kept warm for 1 hour, and finally heated to 180°C, kept warm for 1 hour, and vacuum gradient drying was performed to reduce the moisture content of the graphitized intermediate to below 0.1wt%; Step C: Mix the graphitized intermediate with 70% nitric acid in a mass ratio of 1:5 under ice bath conditions, react for 15 hours, wash until neutral, and then dry to obtain expanded graphite; Step D: Expanded graphite, mercaptoacetic acid and ethyl acetate were mixed in a mass ratio of 1:10:3.5, triethylamine accounting for 0.3% of the mass of the expanded graphite was added, the mixture was reacted at 50° C. for 6 h, and vacuum dried to obtain an artificial graphite negative electrode material for lithium-ion batteries.

[0025] Example 3: A method for preparing an artificial graphite negative electrode material for a lithium-ion battery comprises the following steps: Step A: Asphalt was selected as the carbon source and crushed to D50 = 6 μm by high-energy ball milling (ball-to-material ratio 10:1, rotation speed 400 rpm, time 4 h), and then heated to 1000 °C for pretreatment for 6 h.

[0026] Step B: Under an argon atmosphere, 5 vol% hydrogen was added and a bipolar pulse current (peak current of the bipolar pulse current was 10 kA, pulse width was 50 ms, and frequency was 10 Hz) was applied to raise the temperature of the carbon source to 3200°C and hold the temperature for 2 minutes to perform flash Joule heating on the pretreated carbon source to obtain a graphitized intermediate; Subsequently, the graphitized intermediate was rapidly cooled by liquid nitrogen jet quenching (cooling rate >1000°C / s), resulting in a graphitized intermediate with a lattice defect density of <0.3%. After pneumatic sorting, the graphitized intermediate had a D10 of 8 μm, a D50 of 14 μm, and a D90 of 15 μm. After washing, the dynamic vacuum degree is 10 -3 Under Pa conditions, the graphitized intermediate was first heated to 60°C, kept warm for 2 hours, then heated to 120°C, kept warm for 1 hour, and finally heated to 180°C, kept warm for 1 hour, and vacuum gradient drying was performed to reduce the moisture content of the graphitized intermediate to below 0.1wt%; Step C: Mixing the graphitized intermediate with 70% nitric acid in a mass ratio of 1:10 under ice bath conditions, reacting for 20 hours, washing until neutral, and then drying to obtain expanded graphite; Step D: Expanded graphite, mercaptoacetic acid and ethyl acetate were mixed in a mass ratio of 1:20:7, triethylamine accounting for 1% of the mass of the expanded graphite was added, the mixture was reacted at 50° C. for 6 h, and vacuum dried to obtain an artificial graphite negative electrode material for lithium-ion batteries.

[0027] Example 4: A method for preparing an artificial graphite negative electrode material for a lithium-ion battery comprises the following steps: Step A: needle coke was selected as the carbon source and pulverized to D50 = 8 μm by high-energy ball milling (ball-to-material ratio 10:1, rotation speed 400 rpm, time 4 h), and then heated to 1000 °C for pretreatment for 6 h.

[0028] Step B: Under an argon atmosphere, 5 vol% hydrogen was added and a bipolar pulse current (peak current of the bipolar pulse current was 10 kA, pulse width was 50 ms, and frequency was 10 Hz) was applied to raise the temperature of the carbon source to 2900°C and hold the temperature for 4 minutes to perform flash Joule heating on the pretreated carbon source to obtain a graphitized intermediate; Subsequently, the graphitized intermediate was rapidly cooled by liquid nitrogen jet quenching (cooling rate > 1000°C / s), resulting in a graphitized intermediate with a lattice defect density of 0.2%. After pneumatic sorting, a graphitized intermediate with D10 = 8 μm, D50 = 13 μm, and D90 = 15 μm was obtained. After washing, the dynamic vacuum degree is 10 -3Under Pa conditions, the graphitized intermediate was first heated to 60°C, kept warm for 2 hours, then heated to 120°C, kept warm for 1 hour, and finally heated to 180°C, kept warm for 1 hour, and vacuum gradient drying was performed to reduce the moisture content of the graphitized intermediate to below 0.1wt%; Step C: Mixing the graphitized intermediate with 70% nitric acid in a mass ratio of 1:8 under ice bath conditions, reacting for 8 hours, washing until neutral, and then drying to obtain expanded graphite; Step D: Expanded graphite, mercaptoacetic acid and ethyl acetate were mixed in a mass ratio of 1:12:4, triethylamine accounting for 0.8% of the mass of the expanded graphite was added, the mixture was reacted at 50° C. for 6 h, and vacuum dried to obtain an artificial graphite negative electrode material for lithium-ion batteries.

[0029] Comparative Example 1: A method for preparing an artificial graphite negative electrode material for a lithium-ion battery comprises the following steps: Step A: Asphalt was selected as the carbon source and crushed to D50 = 6 μm by high-energy ball milling (ball-to-material ratio 10:1, rotation speed 400 rpm, time 4 h), and then heated to 1000 °C for pretreatment for 6 h.

[0030] Step B: Under an argon atmosphere, 5 vol% hydrogen was added and a bipolar pulse current (peak current of the bipolar pulse current was 10 kA, pulse width was 50 ms, and frequency was 10 Hz) was applied to raise the temperature of the carbon source to 3200°C and hold the temperature for 2 minutes to perform flash Joule heating on the pretreated carbon source to obtain a graphitized intermediate; Subsequently, the graphitized intermediate was rapidly cooled by liquid nitrogen jet quenching (cooling rate >1000°C / s), resulting in a graphitized intermediate with a lattice defect density of <0.3%. After pneumatic sorting, the graphitized intermediate had a D10 of 8 μm, a D50 of 14 μm, and a D90 of 15 μm. After washing, the dynamic vacuum degree is 10 -3 Under Pa conditions, the graphitized intermediate was first heated to 60°C, kept warm for 2 hours, then heated to 120°C, kept warm for 1 hour, and finally heated to 180°C, kept warm for 1 hour, and vacuum gradient drying was performed to reduce the moisture content of the graphitized intermediate to below 0.1wt%; Step C: Mixing the graphitized intermediate with 70% nitric acid in a mass ratio of 1:10 under ice bath conditions, reacting for 20 hours, washing until neutral, and then drying to obtain expanded graphite; Step D: Expanded graphite, mercaptoacetic acid and ethyl acetate were mixed in a mass ratio of 1:20:7, triethylamine accounting for 1% of the mass of the expanded graphite was added, the mixture was reacted at 50° C. for 6 h, and vacuum dried to obtain an artificial graphite negative electrode material for lithium-ion batteries.

[0031] Comparative Example 2: A method for preparing an artificial graphite negative electrode material for a lithium-ion battery comprises the following steps: Step A: Asphalt was selected as the carbon source. Under an argon atmosphere, 5 vol% hydrogen was added and a bipolar pulse current (peak current of the bipolar pulse current was 5 kA, pulse width was 50 ms, and frequency was 10 Hz) was applied to raise the temperature of the carbon source to 2000°C. The temperature was kept at this temperature for 2 minutes, and the pretreated carbon source was flash-Joule heated to obtain a graphitized intermediate. Subsequently, the graphitized intermediate was rapidly cooled by liquid nitrogen jet quenching (cooling rate >1000°C / s), resulting in a graphitized intermediate with a lattice defect density of <0.3%. After pneumatic sorting, the graphitized intermediate had a D10 of 8 μm, a D50 of 14 μm, and a D90 of 15 μm. After washing, the dynamic vacuum degree is 10 -3 Under Pa conditions, the graphitized intermediate was first heated to 60°C, kept warm for 2 hours, then heated to 120°C, kept warm for 1 hour, and finally heated to 180°C, kept warm for 1 hour, and vacuum gradient drying was performed to reduce the moisture content of the graphitized intermediate to below 0.1wt%; Step B: Mixing the graphitized intermediate with 70% nitric acid in a mass ratio of 1:15 under ice bath conditions, reacting for 20 hours, washing until neutral, and then drying to obtain expanded graphite; Step C: Expanded graphite, mercaptoacetic acid and ethyl acetate are mixed in a mass ratio of 1:20:7, triethylamine accounting for 1% of the mass of the expanded graphite is added, the mixture is reacted at 50° C. for 6 h, and vacuum dried to obtain an artificial graphite negative electrode material for lithium-ion batteries.

[0032] Comparative Example 3: A method for preparing an artificial graphite negative electrode material for a lithium-ion battery comprises the following steps: Step A: Petroleum coke was selected as the carbon source and pulverized to D50 = 5 μm by high-energy ball milling (ball-to-material ratio 10:1, speed 400 rpm, time 4 h), and then heated to 1000 °C for 6 h; Step B: Under an argon atmosphere, 5 vol% hydrogen was added and a bipolar pulse current (peak current of the bipolar pulse current was 10 kA, pulse width was 50 ms, and frequency was 10 Hz) was applied to raise the temperature of the carbon source to 3000°C and hold the temperature for 3 minutes to perform flash Joule heating on the pretreated carbon source to obtain a graphitized intermediate; Subsequently, the graphitized intermediate was rapidly cooled by liquid nitrogen jet quenching (cooling rate >1000°C / s), resulting in a graphitized intermediate with a lattice defect density of <0.3%. After pneumatic sorting, the graphitized intermediate had a D10 of 8 μm, a D50 of 12 μm, and a D90 of 15 μm. After washing, the dynamic vacuum degree is 10 -3Under Pa conditions, the graphitized intermediate was first heated to 60°C, kept warm for 2 hours, then heated to 120°C, kept warm for 1 hour, and finally heated to 180°C, kept warm for 1 hour, and vacuum gradient drying was performed to reduce the moisture content of the graphitized intermediate to below 0.1wt%; Step C: Under ice bath conditions, the graphitized intermediate is mixed with 70% nitric acid in a mass ratio of 1:7, reacted for 10 hours, washed to neutrality, and then dried to obtain expanded graphite; Step D: Expanded graphite, mercaptoacetic acid, and ethyl acetate were mixed in a mass ratio of 1:5:1.6, triethylamine accounting for 0.5% of the mass of the expanded graphite was added, the mixture was reacted at 50° C. for 2 h, and vacuum dried to obtain an artificial graphite negative electrode material for lithium-ion batteries.

[0033] Comparative Example 4 A method for preparing an artificial graphite negative electrode material for a lithium-ion battery comprises the following steps: Step A: needle coke was selected as the carbon source and pulverized to D50 = 8 μm by high-energy ball milling (ball-to-material ratio 10:1, rotation speed 400 rpm, time 4 h), and then heated to 1000 °C for 6 h; Step B, heating the needle coke to 2500° C. and keeping the temperature for 8 hours to obtain a graphitized intermediate; Subsequently, the graphitized intermediate was rapidly cooled by liquid nitrogen jet quenching (cooling rate >1000°C / s), resulting in a graphitized intermediate with a lattice defect density >1%. After pneumatic sorting, the graphitized intermediate had a D10 = 8μm, D50 = 12μm, and D90 = 15μm. After washing, the dynamic vacuum degree is 10 -3 Under Pa conditions, the graphitized intermediate was first heated to 60°C, kept warm for 2 hours, then heated to 120°C, kept warm for 1 hour, and finally heated to 180°C, kept warm for 1 hour, and vacuum gradient drying was performed to reduce the moisture content of the graphitized intermediate to below 0.1wt%; Step C: Under ice bath conditions, the graphitized intermediate was mixed with 50% nitric acid in a mass ratio of 1:3, reacted for 8 hours, washed to neutrality, and then dried to obtain expanded graphite.

[0034] The functionalized artificial graphite negative electrode materials prepared in the above comparative examples and examples were used to conduct the first coulombic efficiency and rate performance tests at different current densities.

[0035] The method for preparing solid-state batteries during the test is as follows: ball-mill the functionalized negative electrode material with the electrolyte LiP6S5Cl and the conductive agent, then add polyvinylidene chloride-hexafluoropropylene binder and N,N-dimethylacetamide solvent, apply the pole piece on the copper foil, dry it, cut it into 10mm diameter discs, put it into a mold, add the electrolyte LiP6S5Cl, and the counter electrode is Li-In alloy. The whole is pressed at a pressure of 450MPa to obtain an electrode sheet, which is then packaged to obtain a half-cell. The test pressure is 200MPa. The charge and discharge range is -0.61 to 1.5V, and the first cycle charge and discharge test is carried out at 0.05C. The test results are shown in Table 1 and Figure 1 shown.

[0036] Table 1 Comparison of performance data of half-cell samples assembled from artificial graphite anode materials for lithium-ion batteries Volume expansion test method: Use an in-situ expansion tester, 0.05C constant current charge and discharge, voltage range -0.61 to 1.5V. Cycle 1000 times, and use a laser thickness gauge to measure the initial thickness (T0) of the fresh electrode. Perform charge and discharge cycles under the above conditions, pause after every 100 cycles, clean the electrode surface and measure the thickness (T n ). The calculation formula of the volume expansion rate of the electrode is shown as follows: Galvanostatic Intermittent Titration Technique (GITT): Charge at 0.05C for 10 minutes and allow the cell to rest for 2 hours until the voltage stabilizes. Record the voltage-time curve during the rest period.

[0037] The lithium ion diffusion rate The calculation formula is as follows: Where τ is the pulse time, Δ E s is the steady-state voltage change, Δ E t The voltage is transient. Example 1 is the best solution. Its core advantages are: high rate performance (3C capacity 320mAh / g, capacity retention rate 92%), flash Joule pulse graphitization technology (3000℃, 3min) significantly shortens the graphitization time, lattice defect density <0.3%, and improves the lithium ion diffusion rate (1.2×10 -9 cm² / s). The synergistic sulfur-oxygen modification (expanded graphite to mercaptoacetic acid mass ratio of 1:15) forms Li-S coordination bonds with the sulfide electrolyte via thiol groups (-SH), inhibiting the shuttle effect, reducing interfacial impedance by 40%, and stabilizing the SEI film. Low volume expansion (volume expansion rate ≤ 5% after 1000 cycles): Gradient particle size sorting (D50 = 12 μm) and directional distribution of conductive agents build an electron-ion dual continuous transmission network to relieve interlayer stress during lithium insertion. High efficiency and energy saving: Pulse heating energy consumption is only 8 kWh / kg, which is 100 times lower than that of traditional processes. Comparative Example 1 (traditional graphitization process), defects: pulse heating is not used, lattice defect density is greater than 1%, resulting in a lithium ion diffusion coefficient (3.0×10 -10 cm 2 / s) is only 25% of that in Example 1.

[0038] like Figure 1 As shown, the specific capacity of Example 1 at current densities of 0.05C and 3C is significantly higher than that of Comparative Example 1. For example, under 3C high rate conditions, the capacity retention rate of Example 1 is 320 mAh / g, while that of Comparative Example 1 is only 248 mAh / g.

[0039] Results: The capacity retention (59%) and 3C capacity (248 mAh / g) of the artificial graphite anode material prepared in Comparative Example 1 were significantly reduced, and the volume expansion (12%) far exceeded that of Example 1, verifying the key role of pulse heating in defect control. Comparative Example 2 (no pretreatment of the carbon source): Defect: Direct use of raw petroleum coke (particle size > 20 μm), uneven particles lead to obstruction of the ion transmission path and increased interfacial impedance. Results: The initial coulombic efficiency (85%) and 3C capacity (230 mAh / g) were extremely low, indicating that carbon source pretreatment (particle size control of 4-15 μm) is key to building a uniform structure. Comparative Example 3 (insufficient thiolacetic acid ratio): Defect: The mass ratio of expanded graphite to thiolacetic acid was 1:5 (lower than the range of 1:10-20 for expanded graphite to thiolacetic acid), the reaction time was shortened to 2 h, and the synergistic modification of sulfur and oxygen was insufficient. Results: The SEI film stability was poor, with a capacity retention (57%) and ion diffusion coefficient (2.8×10 -10 cm 2 / s) are lower than those in Examples 1 to 4, highlighting the necessity of sulfur-oxygen dual-functional modification.

[0040] In summary, the flash Joule pulse graphitization technology: through instantaneous high temperature (2800~3200℃) and rapid cooling (liquid nitrogen quenching), it reduces lattice defects (<0.3%) and improves the lithium ion diffusion rate, which is the core guarantee of high-rate performance. Sulfur-oxygen dual-functional synergistic modification: thiol groups (-SH) anchor polysulfides, and oxygen-containing functional groups induce interlayer micro-expansion (0.342~0.348nm), jointly optimizing interface stability and ion transmission efficiency. Structure-performance integrated design: particle size classification (4~15μm) and directional distribution of conductive agents realize electron-ion dual continuous network, effectively inhibiting volume expansion (≤5%). Examples 1-4 systematically solve the three major bottlenecks of traditional graphite negative electrodes (rate performance, interface stability, and volume expansion) by integrating pulse graphitization, sulfur-oxygen modification and structural optimization.

[0041] The number of devices and processing scales described herein are intended to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be readily apparent to those skilled in the art.

[0042] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing an artificial graphite negative electrode material for a lithium ion battery, characterized in that: The following steps are involved: Step A, pretreating the carbon source material; Step B: flash Joule heating the pretreated carbon source material under an inert atmosphere, followed by rapid cooling to obtain a graphitized intermediate, and screening, washing, and drying the graphitized intermediate; Step C: mixing the graphitized intermediate with a strong acid under ice bath conditions to cause the graphitized intermediate to oxidize and expand to obtain expanded graphite; Step D: Mix expanded graphite with mercaptoacetic acid and ethyl acetate, add a catalyst, and react for a certain time to obtain an artificial graphite negative electrode material for lithium-ion batteries.

2. The method for preparing the artificial graphite negative electrode material for lithium ion batteries according to claim 1, wherein In step A, the method for pretreating the carbon source material specifically includes: grinding the carbon source material into powder, controlling the powder D50 particle size within the range of 4-15 μm; heating to 1000-1200° C. under an inert gas atmosphere, and keeping the temperature for 4-6 hours.

3. The method for preparing the artificial graphite negative electrode material for lithium ion batteries according to claim 2, wherein: In step A, the grinding method specifically includes: using a high-energy ball mill to grind the carbon source material to D50 = 4-8 μm, with a ball-to-material ratio of 10:1, a ball mill speed of 300-600 rpm, and a ball milling time of 2-6 hours.

4. The method for preparing the artificial graphite negative electrode material for lithium ion batteries according to claim 1, wherein In step A, the carbon source material includes one or more of petroleum coke, needle coke, and asphalt.

5. The method for preparing the artificial graphite negative electrode material for lithium ion batteries according to claim 1, wherein: In step B, argon is used as an inert atmosphere, and 5 vol% hydrogen is added to the argon; The pretreated carbon source material is flash-Joule heated using a bipolar pulse current, wherein the peak current of the bipolar pulse current is ≥8500A, the pulse width is 1-100ms, and the frequency is 1-100kHz; the heating temperature of the flash Joule heating is 2800-3200℃, and the holding time is 2-5min; The rapid cooling method includes one of liquid nitrogen jet quenching, supercritical CO2 cooling, forced air cooling, and radiation cooling; wherein the liquid nitrogen jet quenching cooling rate is greater than 1000°C / s; the graphitized intermediate structure La is greater than 100nm, and / or Lc is greater than 50nm, and / or the lattice defect density is less than 0.3%; Screening adopts pneumatic sorting technology, sorting according to particle size distribution D10=8μm, D50=10~14μm, D90=15μm; Drying adopts vacuum gradient drying, and the temperature is raised in stages, specifically, after heating to 50~60℃, keep warm for 1~2h, then heat to 100~120℃, keep warm for 1~2h, and finally heat to 160~200℃, keep warm for 1~2h, and the dynamic vacuum is 10 -3 Pa, the moisture content of the graphitized intermediate after drying is less than 0.1wt%.

6. The method for preparing the artificial graphite negative electrode material for lithium ion batteries according to claim 1, wherein: In step C, the strong acid is one or more of nitric acid, concentrated sulfuric acid, perchloric acid, chromic acid or chloric acid, the concentration of nitric acid is 70-80%, the mass ratio of the graphitized intermediate to nitric acid is 1:5-10, and the oxidation expansion time is 5-20 hours.

7. The method for preparing the artificial graphite negative electrode material for lithium ion batteries according to claim 1, wherein: In the step D, the mass ratio of the expanded graphite, mercaptoacetic acid and ethyl acetate is 1:10-20:3-10, and the amount of the catalyst is 0.1%-1% of the mass of the expanded graphite.

8. The method for preparing the artificial graphite negative electrode material for lithium ion batteries according to claim 1, wherein: In the step D, the expanded graphite is mixed with mercaptoacetic acid, and the reaction temperature after adding the catalyst is 50-70° C. and the reaction time is 4-6 hours; The catalyst is one or more of triethylamine, tributylamine, tripropylamine or tetramethylammonium hydroxide.

9. An artificial graphite negative electrode material for lithium-ion batteries, characterized in that: The artificial graphite negative electrode material for lithium-ion batteries is prepared by the preparation method of the artificial graphite negative electrode material for lithium-ion batteries according to any one of claims 1 to 8.

10. A lithium-ion solid-state battery, characterized in that: The negative electrode material of the lithium-ion solid-state battery is the artificial graphite negative electrode material for lithium-ion batteries according to claim 9.

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