High-capacity fast-charging type graphite composite negative electrode material and preparation method thereof

Abstract

The invention provides a high-capacity fast-filling graphite composite negative electrode material and a preparation method thereof, and the preparation method comprises the following steps: by taking anthracite and needle coke mixed micro powder as a raw material, pre-carbonizing the mixed raw material, and then physically activating by taking water vapor or carbon dioxide as an activating agent to prepare a porous carbon material with rich micropores and moderate specific surface area; a nitrogen-sulfur cocompound or copolymer is used as a doping agent, and the porous carbon material is doped under a hydrothermal reaction condition to prepare the nitrogen-sulfur co-doped porous carbon material. Performing low-temperature graphitization on the porous carbon under a nitrogen-sulfur co-doped catalytic condition to obtain a graphitized nitrogen-sulfur co-doped porous carbon material; then coating and forming the graphitized nitrogen-sulfur co-doped porous carbon material by taking an organic carbon source as a coating agent, an oxide with a perovskite structure as a catalyst and a lithium salt with high thermal stability as a pre-lithiation agent and adopting a kneading and compacting process; and carrying out high-temperature calcination, crushing and screening to prepare the high-capacity fast-charging graphite composite negative electrode material with the secondary particle structure.

Description

Technical Field

[0001] The present invention relates to the technical field of battery negative electrode material preparation, and in particular to a high-capacity fast-charging graphite composite negative electrode material and a preparation method thereof. Background Art

[0002] With the rapid development of the new energy vehicle market, consumers' demand for fast energy replenishment and long battery life is growing. High-voltage fast charging technology can effectively shorten charging time, improve user experience and solve energy replenishment anxiety. The key to improving battery fast charging performance lies in the negative electrode, but traditional graphite negative electrode materials have problems such as slow lithium ion diffusion rate and easy lithium precipitation during fast charging, which limits the fast charging performance of the battery and affects its cycle life and safety. Therefore, the development of high-voltage fast charging technology urgently needs the research and development of negative electrode materials that take into account both high energy density and fast charging capabilities.

[0003] In view of the concentration polarization, SEI film impedance and structural stability of graphite negative electrode in fast charging scenarios, the current research on high-capacity fast-charging negative electrode materials mainly focuses on multi-scale structural optimization, interface chemical regulation and composite system design. For example, the Chinese patent "A lithium-ion battery negative electrode material and its preparation method and application" (CN117976853B) proposes a graphite negative electrode material with a double-layer coating structure. The inner layer is a carbonized layer of nanocellulose (TEMPO oxidized nanocellulose containing lignin), and the outer layer is a carbonized layer of an organic carbon source (sodium alginate, chitosan, etc.). Through the double-layer coating design, the hydrophilicity of the graphite surface is optimized, the slurry dispersibility is improved, and the lithium ion transmission path is shortened, which significantly improves the fast charging performance. Full battery tests show that the material still maintains stable cycle performance under high-rate charging (such as 6C), but the cost of preparing nanocellulose by this technology is high, and it is difficult to control the stability of large-scale production batches. Chinese patent "Three-dimensional graphene for fast-charging lithium-ion battery negative electrode and its preparation method" (CN112909249B) uses CrO 3 The intercalation-hydrogen peroxide stripping-glucose hydrothermal carbonization process constructs a three-dimensional graphene (TDG) network structure. The three-dimensional structure of this technology breaks through the two-dimensional limitation of traditional graphite, and the concentration polarization is reduced by 40% at high rates. Tests show that the capacity of the TDG negative electrode is maintained at 280mAh / g at a rate of 5C, and it is charged to 60% in 6 minutes. At the same time, the growth of lithium dendrites is inhibited, and the cycle stability is excellent (450 cycles of capacity retention of 96%), but the negative electrode process is complicated and difficult to achieve large-scale industrial production. In the patent "A method for preparing a fast-charging graphite negative electrode material" (CN112713270A), Liu Mengyang et al. mixed alkaline substances with graphite, and then activated the graphite by high-temperature treatment, achieving good rate performance, but the high-temperature alkali activation treatment can only increase the surface lithium insertion sites, and cannot significantly shorten the lithium ion diffusion path, so the improvement of rate performance is limited.

[0004] Therefore, further improving the capacity, fast charging performance of fast charging anodes, and reducing costs are still urgent problems to be solved in this field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-capacity fast-charging graphite composite anode material and a preparation method thereof. Using anthracite and needle coke as raw materials, through physical activation, nitrogen and sulfur co-doping, low-temperature catalytic graphitization, and coating modification, etc., to prepare a high-capacity fast-charging graphite composite anode material with high capacity, high first efficiency, excellent fast charging performance, low production cost, and suitable for large-scale industrialization.

[0006] The present invention provides a high-capacity fast-charging graphite composite anode material and a preparation method thereof, including the following steps:

[0007] (1) Physically mix anthracite and needle coke fine powder evenly in a certain mass ratio and place them in a high-temperature atmosphere furnace. Under a protective gas atmosphere, heat up to the pre-carbonization treatment temperature of 750 °C - 900 °C for 1.5 h - 3.0 h for pre-carbonization treatment. After the pre-carbonization treatment, keep the protective atmosphere and cool to room temperature to obtain a pre-carbonized porous carbon precursor;

[0008] (2) Put the pre-carbonized porous carbon precursor into a fluidized bed reactor. Under the condition of a protective gas atmosphere, heat up to the activation treatment temperature of 800 °C - 1000 °C, and then introduce CO 2 or water vapor as the activation gas for activation reaction for 0.5 h - 4.0 h. After the activation reaction ends, stop introducing the activation gas, keep the protective atmosphere and cool to room temperature to obtain a porous carbon material;

[0009] (3) Configure a mixed solution of the porous carbon material, nitrogen and sulfur dopant, and solvent according to a mass ratio of 100:(5 - 15):(900 - 200). After mixing evenly, inject it into a high-pressure reaction kettle. Under closed conditions, stir and heat the mixed solution to the reaction temperature of 150 - 280 °C at a certain stirring speed and keep the reaction for 2.5 - 4.5 h, then cool to room temperature, wash, dewater, and dry to obtain a nitrogen and sulfur co-doped porous carbon material;

[0010] (4) Under a protective gas atmosphere, place the obtained nitrogen and sulfur co-doped porous carbon material in a medium-frequency induction graphitization furnace for graphitization treatment at a graphitization treatment temperature of 1800 °C - 2300 °C for 1.5 h - 4.0 h. After the graphitization ends, keep the protective atmosphere and wait for the material to cool to obtain a graphitized nitrogen and sulfur co-doped porous carbon material;

[0011] (5) Mix the graphitized nitrogen and sulfur co-doped porous carbon material, organic carbon source, prelithiation agent, and perovskite structure oxide evenly according to a mass ratio of 100:(10 - 30):(3 - 8):(2 - 5), then put the mixture into a kneader, and perform kneading and coating treatment on the mixture under heating conditions. After the kneading is completed and cooled, put the material into a tablet press, and keep it under a certain forming pressure for a certain time to form a green body of the graphitized nitrogen and sulfur co-doped porous carbon composite material coated with organic carbon source / prelithiation agent / perovskite structure oxide;

[0012] (6) Place the green body of the graphitized nitrogen and sulfur co-doped porous carbon composite material coated with organic carbon source / prelithiation agent / perovskite structure oxide in a high-temperature atmosphere furnace, heat it up to the calcination temperature of 750 °C - 1000 °C under a protective gas atmosphere for calcination treatment for 2.0 h - 4.0 h. After the calcination is completed, keep the protective atmosphere in the furnace and cool it to room temperature, then crush, screen, and classify to obtain the final product, a high-capacity and fast-charging graphite composite anode material.

[0013] Preferably, in step (1): The carbon content of the anthracite and needle coke is greater than 97%, the average particle size D50 of the anthracite and needle coke fine powder is 5.0 - 8.0 μm, and the mass ratio of the anthracite and needle coke fine powder is 100:(15 - 50); The solid-phase mixing equipment uses a V-type mixer, a drum mixer, a conical mixer, or a mechanical fusion machine; The heating rate of the pre-carbonization treatment temperature is 5 - 10 °C / min; The protective gas is one or more of nitrogen, helium, neon, argon, krypton, or xenon, and its flow rate is 0.4 - 1.0 m 3 / h; The anthracite uses Ningxia Taixi anthracite.

[0014] Preferably, in step (2): The protective gas is one or more of nitrogen, helium, neon, argon, krypton, or xenon, and its flow rate is 0.6 - 1.5 m 3 / h; The heating rate of the activation treatment temperature is 5 - 10 °C / min; The gas flow rate of the CO 2 activation gas is 3 - 30 L / h, and the gas pressure of the steam activation gas is 0.1 - 0.5 MPa.

[0015] Preferably, in step (3): The solution solvents are ethanol, N-methylpyrrolidone, and dimethylformamide; The nitrogen and sulfur dopants are one or more of thiourea, ammonium thiocyanate, potassium thiocyanate, thioacetamide, polyaniline-polythiourea copolymer, and polypyrrole-polysulfide copolymer; The stirring speed is 150 - 600 r / min.

[0016] Preferably, in step (4): The protective gas is one or two of helium and argon, and its flow rate is 1.0 - 2.5 m 3 / h; The heating rate of the graphitization treatment temperature is 10 - 15 °C / min.

[0017] Preferably, in step (5): The organic carbon source is one or more of polyvinyl alcohol, phenolic resin, epoxy resin, polyacrylonitrile, and styrene-butadiene rubber; the prelithiation agent is one or more of lithium carbonate, lithium nitride, lithium phosphate, and lithium chloride with high thermal stability; the perovskite structure oxide is one or more of barium titanate, strontium titanate, or strontium barium titanate; the temperature of the kneading and coating treatment is 120 - 180 °C, and the kneading time is 1.5 - 4.0 h; the pressure of the green compact is 6 - 20 Mpa; the time of the green compact is 0.5 - 2.0 h.

[0018] Preferably, in step (6): The heating rate of the calcination treatment temperature is 3 - 5 °C / min; the protective gas is one or more of nitrogen, helium, neon, argon, krypton, or xenon, and its flow rate is 0.4 - 1.0 m 3 / h; The average particle size D50 of the high-capacity fast-charging graphite composite anode material is 8.0 - 12.0 μm.

[0019] The present invention also provides a high-capacity fast-charging graphite composite anode material, which is composed of graphitized nitrogen-sulfur co-doped coal-based and needle coke-based porous carbon particles with disordered and uniform distribution, and a prelithiation agent / perovskite structure oxide / amorphous carbon composite coated on the surface of the graphitized nitrogen-sulfur co-doped porous carbon material, and a prelithiation agent / perovskite structure oxide / amorphous carbon composite bridging around the coated graphitized nitrogen-sulfur co-doped porous carbon material.

[0020] The working principle of the present invention: The high-capacity fast-charging graphite composite anode material and its preparation method provided by the present invention use a mixture of anthracite and needle coke fine powder as raw materials. After the raw materials are mixed evenly and pre-carbonized, water vapor or carbon dioxide is used as an activator, and a porous carbon material with rich micropores and moderate specific surface area is prepared by physical activation; a nitrogen-sulfur co-doped porous carbon material is prepared by doping the porous carbon material with a nitrogen-sulfur solid compound or copolymer as a dopant under hydrothermal reaction conditions; the porous carbon is subjected to low-temperature graphitization under the catalytic conditions of nitrogen-sulfur co-doping to obtain a graphitized nitrogen-sulfur co-doped porous carbon material with rich pores, uniform pore size distribution, good conductivity, and high mechanical strength; using an organic carbon source as a coating agent, a perovskite structure oxide as a catalyst, and a high-thermal-stability lithium salt as a prelithiation agent, the graphitized nitrogen-sulfur co-doped porous carbon material is coated and formed by kneading and pressing processes, and then a high-capacity fast-charging graphite composite anode material with a secondary particle structure, excellent processing performance, high mechanical strength, and coated with a prelithiation agent / perovskite structure oxide / amorphous carbon composite is prepared by high-temperature calcination, pulverization, and screening. Among them:

[0021] Step (1): The pulverized anthracite and acicular coke fine powder are uniformly mixed and then pre-carbonized. On the one hand, it can remove volatile components such as moisture and low-molecular-weight organic substances in the raw materials, providing a stable carbon skeleton structure and more initial pore activation sites for subsequent physical activation. At the same time, it can avoid the overly violent high-temperature physical activation reaction in the later stage, which is likely to cause uncontrollable pore size and distribution. On the other hand, the uniformity of the raw materials can effectively ensure the hetero-uniformity of the material after physical activation. This is because there are differences in the structures and reaction activities of anthracite and acicular coke, and their respective reaction degrees are different during the physical activation process, resulting in heterogeneity in the pore size and distribution formed.

[0022] Step (2): Under the action of their respective different reaction activities, anthracite and acicular coke are used to prepare a porous carbon material with a moderate specific surface area of 500 - 800 m 2 / g and a multi-level synergistic distribution of micropores and mesopores. The appropriate porous structure distribution of the substrate can effectively improve the mass transfer efficiency of the composite material and increase the diffusion rate of lithium ions. Among them, the porous carbon prepared in this step is mainly composed of micropores for anthracite-based porous carbon and mainly composed of mesopores for acicular-coke-based porous carbon. At the same time, the porous carbon combines the performance advantages of high mechanical strength of coal-based porous carbon, high conductivity of acicular-coke-based porous carbon, and good toughness.

[0023] Step (3): Under hydrothermal reaction conditions, nitrogen and sulfur dopants introduce nitrogen atoms and sulfur atoms into the pores of the porous carbon material to form covalent bonds. Among them, nitrogen atoms can form various stable chemical bonds with carbon atoms, such as pyridine nitrogen and pyrrole nitrogen. The existence of these chemical bonds enhances the skeleton structure of the porous carbon, improves the chemical stability and thermal stability of the material, and the electronegativity of nitrogen is greater than that of carbon. After doping, it will attract the surrounding electrons, forming a local electron cloud density difference in the porous carbon, producing an effect similar to an "electron trap", which is beneficial to the transport and separation of carriers, and improves the conductivity and electron mobility of the material; while sulfur atoms are doped into the porous carbon, due to its lower electronegativity than carbon, it will provide electrons to the surrounding carbon atoms, changing the electron cloud density of the carbon material and generating a local electron enrichment region. At the same time, due to its outer electron structure characteristics, it can undergo specific chemical reactions or interactions with some metal ions or other chemical substances, thus providing more channels and sites for ion storage and charge transfer.

[0024] Step (4) Due to the synergistic catalytic effect of nitrogen and sulfur co-doping, the migration of carbon atoms and electron rearrangement are promoted, effectively reducing the energy barrier of graphitization of the material and significantly decreasing the graphitization temperature. After the graphitization of the porous carbon, the coal-based porous carbon part retains a rich microporous structure and high mechanical strength due to its relatively low degree of graphitization. The needle coke porous carbon fibrous structure forms a cross-linked network and long-range ordered graphite microcrystals after high-temperature graphitization, compensating for the brittleness defect of the coal-based porous carbon and significantly improving the electron mobility of the composite material, thereby achieving a comprehensive balance of the material's electrical conductivity, electrochemical activity, porosity, and mechanical strength. Although the graphitization of the porous carbon leads to the shrinkage or closure of some pores, it makes the pore size distribution more uniform, and the proportion of micropores increases to more than 80%, enhancing the material stability. Moreover, the pore size gradually decreases from the inside to the outside, and the overall specific surface area of the material decreases to below 100m 2 / g.

[0025] Step (5) Through the extrusion, splitting, and kneading of the kneader, the uniformly compounded organic carbon source, prelithiation agent, and perovskite-structured oxide are heated and softened, and then fully infiltrate into the micropores of the graphitized nitrogen and sulfur co-doped porous carbon to form a paste with high density and good plasticity. At the same time, after the paste cools, the compaction treatment by the tablet press further eliminates the frictional stress between the paste particles, thereby increasing the tapped density. This helps to improve the uniformity and consistency of the prelithiation agent / perovskite-structured oxide / amorphous carbon composite coating layer, while improving the interfacial impedance and performance, reducing the risk of lithium dendrites during fast charging, and effectively enhancing the mechanical strength and rate charge-discharge stability of the final product secondary particles.

[0026] Step (6) The high thermal stability lithium salt prelithiation agent and perovskite-structured oxide have good thermal stability and do not decompose under high-temperature conditions. The organic carbon source, prelithiation agent, and perovskite-structured oxide form a prelithiation agent / perovskite-structured oxide / amorphous carbon composite through high-temperature calcination. The carbon atoms at the interface between the prelithiation agent / perovskite-structured oxide / amorphous carbon composite and the graphitized nitrogen and sulfur co-doped porous carbon material rearrange with each other to form a stable chemical bond structure, connecting and restructuring the graphitized nitrogen and sulfur co-doped porous carbon materials. After crushing and screening, secondary granulation is achieved, making the macroscopic performance of the composite anode material particles more isotropic, and presenting a heterogeneous gradient distribution of porosity in structure. This can effectively improve the mechanical strength and rate cycle stability of the material structure. The perovskite-structured oxide in the prelithiation agent / perovskite-structured oxide / amorphous carbon composite will generate polarization during the charge-discharge process, forming an electric dipole moment to generate a local electric field, which can help to enhance the activity of the prelithiation agent, effectively compensate for the irreversible lithium adsorption during the charge-discharge process of the material, improve the initial charge-discharge efficiency of the material, and promote the formation of a stable SEI film and reduce the interfacial resistance to reduce the risk of lithium dendrites during fast charging. At the same time, it also plays a role in regulating the electronic structure, providing active sites, and stabilizing the electrode interface.

[0027] The high-capacity fast-charging graphite composite anode material prepared by the present invention is a secondary granulated particle, which is composed of graphitized coal-based and needle coke-based porous carbon particles with disordered and uniform nitrogen and sulfur co-doping, a prelithiation agent / perovskite structure oxide / amorphous carbon composite coated on the surface of the graphitized nitrogen and sulfur co-doped porous carbon material, and a prelithiation agent / perovskite structure oxide / amorphous carbon composite bridged around the coated graphitized nitrogen and sulfur co-doped porous carbon material. Among them, nitrogen atoms and sulfur atoms are introduced into the micropores of the substrate graphitized porous carbon material to form covalent bonds. Nitrogen atom doping can form local charge imbalance regions in the carbon skeleton, enhance the electron transport ability, and form rich active sites, improving the electrochemical activity of the redox reaction. Sulfur atom doping can couple with the carbon π-electron system to form a delocalized electron structure to promote charge transfer and inhibit the excessive graphitization of the carbon skeleton to maintain the mechanical strength and stability of the microporous structure. The surface of the disordered and uniformly distributed graphitized nitrogen and sulfur co-doped porous carbon material particles is coated with a dense prelithiation agent / perovskite structure oxide / amorphous carbon composite, and the particles are bridged with each other through the prelithiation agent / perovskite structure oxide / amorphous carbon composite to form secondary particles with controllable particle size distribution, making the macroscopic performance of the composite anode material particles closer to isotropy, effectively relieving the volume stress during the charge and discharge of the active material, improving the mechanical strength and rate cycle stability of the material. At the same time, the perovskite structure oxide in the prelithiation agent / perovskite structure oxide / amorphous carbon composite will generate polarization during the charge and discharge process, forming an electric dipole moment to generate a local electric field, which can help improve the activity of the prelithiation agent, effectively compensate for the irreversible lithium adsorption during the charge and discharge process of the material, improve the initial charge and discharge efficiency of the material, promote the formation of a stable SEI film, reduce the interfacial resistance, and reduce the risk of lithium dendrites during fast charging.

[0028] Advantages of the present invention:

[0029] 1) Using anthracite and needle coke as raw materials, and taking advantage of the differences in their respective performance structures and reaction activities, through physical activation, nitrogen and sulfur doping, and low-temperature catalytic graphitization, the porous carbon structure of the anode material substrate presents a heterogeneous gradient distribution of porosity, combining the advantages of rich porosity and high mechanical strength of coal-based porous carbon, and high conductivity and good toughness of needle coke-based porous carbon, achieving a comprehensive balance of conductivity, electrochemical activity, porosity, and mechanical strength of the composite material.

[0030] 2) The present invention uses a nitrogen-sulfur homogenous compound or copolymer as a dopant, and under hydrothermal reaction conditions, nitrogen atoms and sulfur atoms are introduced into the micropores of the substrate porous carbon material to form covalent bonds. While the nitrogen atom doping enhances the stability of the porous carbon framework structure, it improves the electrochemical stability and thermal stability of the material. Moreover, since the electronegativity of nitrogen atoms is greater than that of carbon atoms, a large number of highly electronegative active sites are generated after the substrate porous carbon is doped, improving the material's electrical conductivity and electron mobility. The electronegativity of sulfur atoms is smaller than that of carbon atoms. After doping, sulfur atoms will provide electrons to the surrounding carbon atoms, causing local changes in the electron cloud density of the substrate porous carbon to generate electron enrichment regions, which can provide more pathways and sites for ion storage and charge transfer, effectively improving the discharge specific capacity, rate charge-discharge performance, and cycling performance of the composite material. In addition, the synergistic catalytic effect of sulfur-nitrogen co-doping can reduce the graphitization energy barrier of the substrate porous carbon, significantly reduce the graphitization temperature, and inhibit the excessive graphitization of the material, enabling the material to maintain high electrochemical activity while having good porosity and reducing the production and preparation costs.

[0031] 3) In the present invention, the surface of the disordered and uniformly distributed nitrogen-sulfur co-doped graphitized coal-based and needle coke-based porous carbon particles is coated with a dense pre-lithiation agent / perovskite structure oxide / amorphous carbon composite. The pre-lithiation agent / perovskite structure oxide / amorphous carbon composite bridges the particles to form secondary particles with a controllable particle size distribution, making the macroscopic performance of the composite anode material particles closer to isotropy. This can effectively relieve the volume stress during the charge and discharge process of the active material and improve the rate cycling stability of the material. The perovskite structure oxide in the pre-lithiation agent / perovskite structure oxide / amorphous carbon composite will generate polarization during the charge and discharge process, forming an electric dipole moment to generate a local electric field, which can help improve the activity of the pre-lithiation agent, effectively compensate for the irreversible lithium adsorption during the charge and discharge process of the material, improve the first charge-discharge efficiency of the material, promote the formation of a stable SEI film, reduce the interfacial resistance, and reduce the risk of lithium dendrites during fast charging.

[0032] 4) The preparation method of the present invention is simple, easy to control, low in cost, and easy to industrialize. Description of the Drawings

[0033] Figure 1 SEM image of the high-capacity fast-charging graphite composite anode material prepared in Example 4. Detailed Embodiments

[0034] In order to make the technical solution of the present invention easier to understand, the technical solution of the present invention will be clearly and completely described below by way of specific embodiments in conjunction with the drawings.

[0035] Example 1:

[0036] The high-capacity fast-charging graphite composite anode material and its preparation method in this example include the following steps:

[0037] (1) Anthracite with an average particle size D50 of 5 μm and acicular coke micropowder were physically mixed evenly by mass ratio of 100:15, and then put into a high-temperature atmosphere furnace. Under the atmosphere protection with a nitrogen flow rate of 0.4 m 3 / h, it was heated from room temperature to 750 °C at a heating rate of 5 °C / min, kept at a constant temperature for 3.0 h, and after the insulation ended, it was cooled to room temperature under the protection atmosphere to obtain a pre-carbonized porous carbon precursor.

[0038] (2) The pre-carbonized porous carbon precursor was put into a fluidized bed reactor. Under the atmosphere protection with a nitrogen flow rate of 0.6 m 3 / h, it was heated from room temperature to 800 °C at a heating rate of 5 °C / min, and then CO with a gas flow rate of 3 L / h was introduced 2 as the activation gas. After activation for 4.0 h, the activation gas was stopped, and it was cooled to room temperature under the protection atmosphere to obtain a porous carbon material.

[0039] (3) According to the mass ratio of porous carbon material, nitrogen and sulfur dopant, and solvent of 100:5:200, the porous carbon material and thiourea were added to an ethanol solvent to prepare a mixed solution. After mixing evenly, it was injected into a high-pressure reactor, and the high-pressure reactor was sealed and heated to 150 °C at a rotation speed of 150 r / min, and the reaction was continued for 4.5 h. After cooling to room temperature, it was washed, de-liquored and dried to obtain a nitrogen and sulfur co-doped porous carbon material.

[0040] (4) The nitrogen and sulfur co-doped porous carbon material was placed in a medium-frequency induction graphitization furnace. Under the atmosphere protection with a helium flow rate of 1.0 m 3 / h, it was heated from room temperature to 1800 °C at a heating rate of 10 °C / min and kept at a constant temperature for 4.0 h. After graphitization ended, the protection atmosphere was maintained, and after the material cooled, a graphitized nitrogen and sulfur co-doped porous carbon material was obtained.

[0041] (5) The graphitized nitrogen and sulfur co-doped porous carbon material, polyvinyl alcohol, lithium carbonate and barium titanate were mixed evenly by mass ratio of 100:10:3:2, and then kneaded and coated at 120 °C for 4.0 h in a kneader. After the material cooled, it was pressed into a billet at a pressure of 6 Mpa for 2.0 h to obtain a billet of a graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide.

[0042] (6) The billet of the graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide was placed in a high-temperature atmosphere furnace. Under the nitrogen flow rate of 0.4 m 3Under an / h atmosphere, the temperature is raised to 750 °C at a heating rate of 3 °C / min and kept at a constant temperature for 4.0 h. After the calcination is completed, the protective atmosphere is maintained until the material cools to room temperature, and then it is crushed, screened and classified to obtain a high-capacity fast-charging graphite composite anode material with an average particle size D50 of 8.0 μm.

[0043] The high-capacity fast-charging graphite composite anode material obtained in Example 1 is subjected to physical and chemical property tests. The tapped density of the anode material powder is 1.04 g / cm 3 , the specific surface area is 1.57 m 2 / g, the initial discharge capacity at 0.1C is 345.4 mAh / g, the initial efficiency is 92.1%, and the capacity retention rate after 200 cycles of 1C charge and discharge is 98.4%. The test results are summarized in Table 1.

[0044] Example 2:

[0045] The high-capacity fast-charging graphite composite anode material and its preparation method in this example include the following steps:

[0046] (1) Anthracite with an average particle size D50 of 5 μm and acicular coke fine powder are physically mixed evenly by mass ratio of 100:25, and then put into a high-temperature atmosphere furnace. Under the atmosphere protection with a helium flow rate of 0.6 m 3 / h, the temperature is raised from room temperature to 780 °C at a heating rate of 6 °C / min and kept at a constant temperature for 2.7 h. After the heat preservation is completed, the protective atmosphere is maintained and cooled to room temperature to obtain a pre-carbonized porous carbon precursor.

[0047] (2) The pre-carbonized porous carbon precursor is put into a fluidized bed reactor. Under the atmosphere protection with a helium flow rate of 0.9 m 3 / h, the temperature is raised from room temperature to 850 °C at a heating rate of 6 °C / min, and then CO with a gas flow rate of 15 L / h is introduced 2 Activating gas, after activating for 3.0 h, the activating gas is stopped, and the protective atmosphere is maintained and cooled to room temperature to obtain a porous carbon material.

[0048] (3) According to the mass ratio of porous carbon material, nitrogen and sulfur dopant and solvent of 100:7:400, the porous carbon material and ammonium thiocyanate are added into ethanol solvent to prepare a mixed solution. After mixing evenly, it is injected into a high-pressure reactor, and the high-pressure reactor is sealed and heated to 200 °C at a rotation speed of 250 r / min, and the reaction is continued for 4.0 h. After cooling to room temperature, it is washed, de-liquefied and dried to obtain a nitrogen and sulfur co-doped porous carbon material.

[0049] (4) The nitrogen and sulfur co-doped porous carbon material is placed in an intermediate frequency induction graphitization furnace. Under a helium flow rate of 1.3 m 3 / Under an h atmosphere protection, the temperature is raised from room temperature to 1900 °C at a heating rate of 11 °C / min and held at a constant temperature for 3.5 h. After the graphitization is completed, the protective atmosphere is maintained, and the graphitized nitrogen and sulfur co-doped porous carbon material is obtained after the material is cooled.

[0050] (5) The graphitized nitrogen and sulfur co-doped porous carbon material, phenolic resin, lithium nitride, and barium titanate are mixed evenly according to a mass ratio of 100:15:4:3, and then placed in a kneader and kneaded and coated at a temperature of 130 °C for 3.5 h. After the material is cooled, it is pressed into a blank at a pressure of 10 Mpa for 1.7 h to obtain a precursor blank of a graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite-structured oxide.

[0051] (6) The precursor blank of the graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite-structured oxide is placed in a high-temperature atmosphere furnace. Under an atmosphere with a helium flow rate of 0.6 m 3 / h, the temperature is raised to 800 °C at a heating rate of 3 °C / min and held at a constant temperature for 3.5 h. After the calcination is completed, the protective atmosphere is maintained until the material is cooled to room temperature, and then it is crushed, screened, and classified to obtain a high-capacity fast-charging graphite composite negative electrode material with an average particle size D50 of 9.0 μm.

[0052] For the high-capacity fast-charging graphite composite negative electrode material obtained in Example 2, physical and chemical property tests are carried out. The tapped density of the negative electrode material powder is 1.07 g / cm 3 , the specific surface area is 1.77 m 2 / g, the first discharge capacity at 0.1C is 347.8 mAh / g, the first efficiency is 92.8%, and the capacity retention rate after 200 cycles of 1C charge and discharge is 99.2%. The test results are summarized in Table 1.

[0053] Example 3:

[0054] The high-capacity fast-charging graphite composite negative electrode material and its preparation method in this example include the following steps:

[0055] (1) Anthracite with an average particle size D50 of 6 μm and acicular coke fine powder are physically mixed evenly according to a mass ratio of 100:30, and then put into a high-temperature atmosphere furnace. Under an atmosphere protection with a neon flow rate of 0.7 m 3 / h, the temperature is raised from room temperature to 810 °C at a heating rate of 7 °C / min and held at a constant temperature for 2.4 h. After the heat preservation is completed, the protective atmosphere is maintained and cooled to room temperature to obtain a pre-carbonized porous carbon precursor.

[0056] (2) The pre-carbonized porous carbon precursor is put into a fluidized bed reactor. Under an atmosphere protection with a neon flow rate of 1.0 m 3 / h, the temperature is raised from room temperature to 900 °C at a heating rate of 7 °C / min, and then CO with a gas flow rate of 30 L / h is introduced 2The activation gas is used for activation. After 2.5 hours of activation, the activation gas is stopped, and the porous carbon material is obtained by cooling under a protective atmosphere to room temperature.

[0057] (3) According to the mass ratio of the porous carbon material, nitrogen and sulfur dopant, and solvent being 100:9:500, the porous carbon material and potassium thiocyanate are added to the N-methylpyrrolidone solvent to prepare a mixed solution. After mixing evenly, it is injected into a high-pressure reactor. The high-pressure reactor is sealed and the mixed solution is heated to 210 °C at a rotation speed of 350 r / min, and the reaction is continued for 3.5 hours. After cooling to room temperature, it is washed, de-liquored, and dried to obtain a nitrogen and sulfur co-doped porous carbon material.

[0058] (4) The nitrogen and sulfur co-doped porous carbon material is placed in an intermediate frequency induction graphitization furnace. Under the protection of a helium gas flow rate of 1.6 m 3 / h atmosphere, it is heated from room temperature to 2000 °C at a heating rate of 12 °C / min and kept at a constant temperature for 3.0 h. After the graphitization is completed, the protective atmosphere is maintained, and the graphitized nitrogen and sulfur co-doped porous carbon material is obtained after the material is cooled.

[0059] (5) After the graphitized nitrogen and sulfur co-doped porous carbon material, epoxy resin, lithium nitride, and strontium titanate are mixed evenly according to the mass ratio of 100:20:5:3, they are kneaded and coated at 150 °C in a kneader for 3.0 h. After the material is cooled, it is pressed into a blank at a pressure of 14 Mpa for 1.4 h to obtain a precursor blank of a graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide.

[0060] (6) The precursor blank of the graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide is placed in a high-temperature atmosphere furnace. Under the atmosphere of a neon gas flow rate of 0.7 m 3 / h, it is heated to 850 °C at a heating rate of 4 °C / min and kept at a constant temperature for calcination for 3.0 h. After the calcination is completed, the protective atmosphere is maintained until the material is cooled to room temperature, and then it is crushed, screened, and classified to obtain a high-capacity fast-charging graphite composite negative electrode material with an average particle size D50 of 10.0 μm.

[0061] For the high-capacity fast-charging graphite composite negative electrode material obtained in Example 3, physical and chemical property tests are carried out. The tap density of the negative electrode material powder is 1.09 g / cm 3 , the specific surface area is 2.02 m 2 / g, the first discharge capacity at 0.1C is 349.2 mAh / g, the first efficiency is 94.1%, and the capacity retention rate after 200 cycles of 1C charge and discharge is 100.2%. The test results are summarized in Table 1.

[0062] Example 4:

[0063] The high-capacity fast-charging graphite composite negative electrode material and its preparation method in this example include the following steps:

[0064] (1) Anthracite and acicular coke fine powder with an average particle size D50 of 7 μm were physically mixed evenly by mass ratio of 100:30, and then put into a high-temperature atmosphere furnace. Under the atmosphere protection with an argon flow rate of 0.7 m 3 / h, the temperature was raised from room temperature to 840 °C at a heating rate of 8 °C / min, held at a constant temperature for 2.1 h, and after the insulation ended, the protective atmosphere was maintained and cooled to room temperature to obtain a pre-carbonized porous carbon precursor.

[0065] (2) The pre-carbonized porous carbon precursor was put into a fluidized bed reactor. Under the atmosphere protection with an argon flow rate of 1.1 m 3 / h, the temperature was raised from room temperature to 900 °C at a heating rate of 8 °C / min, and then steam gas with a gas pressure of 0.5 MPa was introduced. After activation for 2.0 h, the activation gas was stopped, and the protective atmosphere was maintained and cooled to room temperature to obtain a porous carbon material.

[0066] (3) According to the mass ratio of porous carbon material, nitrogen and sulfur dopant, and solvent of 100:11:600, the porous carbon material and thioacetamide were added to N-methylpyrrolidone solvent to prepare a mixed solution. After mixing evenly, it was injected into a high-pressure reactor, and the high-pressure reactor was sealed and heated to 220 °C at a rotation speed of 400 r / min. After continuing the reaction for 3.5 h, it was cooled to room temperature, washed, de-liquefied, and dried to obtain a nitrogen and sulfur co-doped porous carbon material.

[0067] (4) The nitrogen and sulfur co-doped porous carbon material was placed in a medium-frequency induction graphitization furnace. Under the atmosphere protection with an argon flow rate of 1.9 m 3 / h, the temperature was raised from room temperature to 2100 °C at a heating rate of 13 °C / min and held at a constant temperature for 2.5 h. After graphitization, the protective atmosphere was maintained. After the material was cooled, graphitized nitrogen and sulfur co-doped porous carbon material was obtained.

[0068] (5) The graphitized nitrogen and sulfur co-doped porous carbon material, epoxy resin, lithium phosphate, and strontium titanate were mixed evenly by mass ratio of 100:20:6:4, and then kneaded and coated at 150 °C for 2.5 h in a kneader. After the material was cooled, it was pressed into a blank at 14 MPa for 1.1 h to obtain a precursor blank of a graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide.

[0069] (6) The precursor blank of the graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide was placed in a high-temperature atmosphere furnace. Under the atmosphere of 0.7 m 3 / h, the temperature was raised to 900 °C at a heating rate of 4 °C / min and calcined at a constant temperature for 3.0 h. After the calcination ended, the protective atmosphere was maintained. After the material was cooled to room temperature, it was crushed, screened, and classified to obtain a high-capacity fast-charging type graphite composite anode material with an average particle size D50 of 10.0 μm.

[0070] The high-capacity fast-charging graphite composite anode material obtained in Example 4 was subjected to physical and chemical property tests. The tapped density of the anode material powder was 1.10 g / cm 3 , the specific surface area was 2.29 m 2 / g, the initial discharge capacity at 0.1C was 353.2 mAh / g, the initial efficiency was 94.7%, and the capacity retention rate after 100 cycles of 1C charge and discharge was 100.5%. The test results are summarized in Table 1. As Figure 1 shown, the surface of the high-capacity fast-charging graphite composite anode material is relatively flat and smooth, indicating that the organic carbon source kneading coating and compacting treatment make the internal combination of the composite material tight and firm and the coating uniform and dense, and the crushing, screening and classification do not cause great damage to the secondary particle structure, which is extremely beneficial to reducing the interfacial impedance, ensuring the lithium-ion transmission efficiency during the fast charging process of the material, reducing the side reactions between the graphite substrate and substances such as the electrolyte, improving the interfacial stability, and effectively improving the influence of the high specific surface area of the substrate porous carbon on the processing performance of the composite material.

[0071] Example 5:

[0072] The high-capacity fast-charging graphite composite anode material and its preparation method in this example include the following steps:

[0073] (1) Anthracite with an average particle size D50 of 8 μm and acicular coke fine powder were physically mixed evenly by mass ratio of 100:35, and then put into a high-temperature atmosphere furnace. Under the atmosphere protection of a krypton gas flow rate of 0.8 m 3 / h, the temperature was raised from room temperature to 870 °C at a heating rate of 9 °C / min, kept at a constant temperature for 1.8 h, and after the insulation ended, the protective atmosphere was maintained and cooled to room temperature to obtain a pre-carbonized porous carbon precursor.

[0074] (2) The pre-carbonized porous carbon precursor was put into a fluidized bed reactor. Under the atmosphere protection of a krypton gas flow rate of 1.2 m 3 / h, the temperature was raised from room temperature to 950 °C at a heating rate of 9 °C / min, and then water vapor gas with a gas pressure of 0.3 MPa was introduced. After activation for 1.5 h, the activation gas was stopped, and the protective atmosphere was maintained and cooled to room temperature to obtain a porous carbon material.

[0075] (3) According to the mass ratio of porous carbon material, nitrogen and sulfur dopant and solvent of 100:13:700, the porous carbon material and polyaniline-polythiourea copolymer were added to dimethylformamide solvent to prepare a mixed solution. After mixing evenly, it was injected into a high-pressure reaction kettle, and the high-pressure reaction kettle was closed and heated to 230 °C at a rotation speed of 500 r / min. After continuing to react for 3.0 h, it was cooled to room temperature, washed, de-liquored and dried to obtain a nitrogen and sulfur co-doped porous carbon material.

[0076] (4) Place the nitrogen and sulfur co-doped porous carbon material in a medium-frequency induction graphitization furnace. Under the protection of an argon atmosphere with a flow rate of 2.2 m 3 / h, heat it from room temperature to 2200 °C at a heating rate of 14 °C / min and keep it at a constant temperature for 2.0 h. After the graphitization is completed, maintain the protective atmosphere. After the material cools down, the graphitized nitrogen and sulfur co-doped porous carbon material is obtained.

[0077] (5) After uniformly mixing the graphitized nitrogen and sulfur co-doped porous carbon material, polyacrylonitrile, lithium phosphate, and barium strontium titanate in a mass ratio of 100:25:7:4, place them in a kneader and knead and coat them at 170 °C for 2.0 h. After the material cools down, press the blank at a pressure of 16 Mpa for 0.8 h to obtain a precursor blank of a graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite-structured oxide.

[0078] (6) Place the precursor blank of the graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite-structured oxide in a high-temperature atmosphere furnace. Under an atmosphere with a krypton flow rate of 0.8 m 3 / h, heat it to 950 °C at a heating rate of 5 °C / min and keep it at a constant temperature for calcination for 2.5 h. After the calcination is completed, maintain the protective atmosphere until the material cools down to room temperature, then crush, screen, and classify it to obtain a high-capacity fast-charging graphite composite negative electrode material with an average particle size D50 of 11 μm.

[0079] For the high-capacity fast-charging graphite composite negative electrode material obtained in Example 5, physical and chemical property tests were conducted. The tapped density of the negative electrode material powder is 1.05 g / cm 3 , the specific surface area is 2.17 m 2 / g, the first discharge capacity at 0.1C is 350.6 mAh / g, the first efficiency is 93.5%, and the capacity retention rate after 200 cycles of 1C charge and discharge is 99.7%. The test results are summarized in Table 1.

[0080] Example 6:

[0081] The high-capacity fast-charging graphite composite negative electrode material and its preparation method in this example include the following steps:

[0082] (1) Uniformly mix anthracite with an average particle size D50 of 8 μm and needle coke fine powder in a mass ratio of 100:50, and then put them into a high-temperature atmosphere furnace. Under the protection of a nitrogen atmosphere with a flow rate of 1.0 m 3 / h, heat it from room temperature to 900 °C at a heating rate of 10 °C / min, keep it at a constant temperature for 1.5 h, and after the heat preservation is completed, maintain the protective atmosphere and cool it to room temperature to obtain a pre-carbonized porous carbon precursor.

[0083] (2) Put the pre-carbonized porous carbon precursor into a fluidized bed reactor. Under a xenon atmosphere with a flow rate of 1.5 m 3 / Under the protection of an h atmosphere, the temperature was raised from room temperature to 1000 °C at a heating rate of 10 °C / min, and then water vapor gas with a gas pressure of 0.1 MPa was introduced. After activation for 0.5 h, the activation gas was stopped, and the porous carbon material was obtained by cooling to room temperature while maintaining the protective atmosphere.

[0084] (3) According to the mass ratio of porous carbon material, nitrogen and sulfur dopant, and solvent of 100:15:900, the porous carbon material and polypyrrole-polythioether copolymer were added to dimethylformamide solvent to prepare a mixed solution. After mixing evenly, it was injected into a high-pressure reactor, and the high-pressure reactor was sealed and heated to 280 °C at a rotation speed of 600 r / min. After continuing to react for 2.5 h, it was cooled to room temperature, washed, de-liquored, and dried to obtain a nitrogen and sulfur co-doped porous carbon material.

[0085] (4) The nitrogen and sulfur co-doped porous carbon material was placed in a medium-frequency induction graphitization furnace. Under the protection of an argon flow rate of 2.5 m 3 / h atmosphere, the temperature was raised from room temperature to 2300 °C at a heating rate of 15 °C / min and kept at a constant temperature for 1.5 h. After graphitization, the protective atmosphere was maintained, and the graphitized nitrogen and sulfur co-doped porous carbon material was obtained after the material was cooled.

[0086] (5) The graphitized nitrogen and sulfur co-doped porous carbon material, styrene-butadiene rubber, lithium chloride, and barium strontium titanate were mixed evenly according to the mass ratio of 100:30:8:5, and then placed in a kneader and kneaded and coated at 180 °C for 1.5 h. After the material was cooled, it was pressed into a blank at a pressure of 20 Mpa for 0.5 h to obtain a precursor blank of a graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide.

[0087] (6) The precursor blank of the graphitized nitrogen and sulfur co-doped porous carbon composite material coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide was placed in a high-temperature atmosphere furnace. Under the atmosphere of a xenon flow rate of 1.0 m 3 / h, the temperature was raised to 1000 °C at a heating rate of 5 °C / min and kept at a constant temperature for calcination for 2.0 h. After the calcination, the protective atmosphere was maintained until the material was cooled to room temperature, and then it was crushed, screened, and classified to obtain a high-capacity fast-charging graphite composite negative electrode material with an average particle size D50 of 12.0 μm.

[0088] The high-capacity fast-charging graphite composite negative electrode material obtained in Example 6 was subjected to physical and chemical property tests. The tap density of the negative electrode material powder was 0.97 g / cm 3 , the specific surface area was 2.03 m 2 / g, the first discharge capacity at 0.1C was 349.8 mAh / g, the first efficiency was 92.5%, and the cycle capacity retention rate after 200 cycles of 1C charge and discharge was 99.0%. The test results are summarized in Table 1.

[0089] Comparative example:

[0090] The high-capacity fast-charging graphite composite anode material of this embodiment and its preparation method include the following steps:

[0091] (1) Anthracite with an average particle size D50 of 7 μm and acicular coke fine powder are physically mixed evenly in a solid phase according to a mass ratio of 100:30, and then put into a high-temperature atmosphere furnace. Under the atmosphere protection with an argon flow rate of 0.7 m 3 / h, it is heated from room temperature to 840 °C at a heating rate of 8 °C / min, kept at a constant temperature for 2.1 h, and after the heat preservation ends, it is cooled to room temperature while maintaining the protective atmosphere to obtain a pre-carbonized porous carbon precursor.

[0092] (2) The pre-carbonized porous carbon precursor is put into a fluidized bed reactor. Under the atmosphere protection with an argon flow rate of 1.1 m 3 / h, it is heated from room temperature to 900 °C at a heating rate of 8 °C / min, and then water vapor gas with a gas pressure of 0.5 MPa is introduced. After activation for 2.0 h, the activation gas is stopped, and it is cooled to room temperature while maintaining the protective atmosphere to obtain a porous carbon material.

[0093] (3) The porous carbon material is placed in an intermediate frequency induction graphitization furnace. Under the atmosphere protection with an argon flow rate of 1.9 m 3 / h, it is heated from room temperature to 2100 °C at a heating rate of 13 °C / min and kept at a constant temperature for 2.5 h. After graphitization, the protective atmosphere is maintained, and after the material is cooled, a graphitized porous carbon material is obtained.

[0094] (4) After the graphitized porous carbon material, epoxy resin, and lithium phosphate are mixed evenly according to a mass ratio of 100:20:6, they are kneaded and coated at 150 °C in a kneader for 2.5 h. After the material is cooled, it is pressed into a blank at a pressure of 14 Mpa for 1.1 h to obtain a precursor blank of an organic carbon source / pre-lithiation agent-coated graphitized porous carbon composite material.

[0095] (5) The precursor blank of the organic carbon source / pre-lithiation agent-coated graphitized porous carbon composite material is placed in a high-temperature atmosphere furnace. Under the atmosphere with an argon flow rate of 0.7 m 3 / h, it is heated to 900 °C at a heating rate of 4 °C / min and kept at a constant temperature for calcination for 3.0 h. After the calcination ends, the protective atmosphere is maintained until the material is cooled to room temperature, and then it is crushed, screened, and classified to obtain a high-capacity fast-charging graphite composite anode material with an average particle size D50 of 10.0 μm.

[0096] For the material prepared in the comparative example, the tapped density of the powder was measured to be 1.09 g / cm 3 , and the specific surface area was 2.18 m 2 / g. The material prepared in the comparative example was used as the negative electrode active material of the simulated battery to carry out electrochemical performance testing. The 0.1C first discharge capacity was 335.2mAh / g, the first efficiency was 87.3%, and the 200-week cycle capacity retention rate was 94.7%. The test results are shown in Table 1.

[0097] The comparative example did not carry out nitrogen-sulfur co-doping and perovskite structure oxide composite coating. The other material components, proportions and processes were the same as those in Example 4. The first discharge capacity, first efficiency and rate charge and discharge cycle performance of the prepared samples were all inferior to the test results of the samples in Example 4.

[0098] Performance testing method:

[0099] The method of the present invention prepares a high-capacity fast-charging graphite composite negative electrode material, and the morphology of the composite negative electrode material is observed by a Zeiss Gemini SEM 500 field emission scanning electron microscope; the tap density of the composite negative electrode material powder is tested by a Dandong Better BT-312 tap density meter; the specific surface area of ​​the composite negative electrode material is tested by a JW-DX specific surface area tester of Jingwei Gaobo Company; and the buckle electrical performance of the composite negative electrode material is tested by a CT2001A blue dot battery test system of Wuhan Blue Electric Company.

[0100] The negative electrode material samples of Examples 1-6 and Comparative Examples were used to make pole pieces and conduct half-cell tests. According to the active material: acetylene carbon black conductive agent: PVDF binder = 92:3:5, NMP was used as solvent for slurrying, mixed evenly and coated on copper foil, dried at 120°C for 10 hours under vacuum conditions, rolled and punched, and a metal lithium sheet was used as the counter electrode, and a 1mol·L-1LiPF6 / DMC+DEC+EC (volume ratio of 1:1:1) solution was used as the electrolyte. In a German Braun MBRAUN glove box protected by high-purity argon, a CR2032 button-type experimental battery was made. At room temperature (25°C), the charge and discharge voltage range was 0.001-2.0V, and the 0.1C first discharge capacity mAh / g and the first efficiency were measured. After 2 weeks of 0.1C charge and discharge activation, a 1C charge and discharge cycle test was performed, and the 200-week cycle capacity retention rate was calculated using the ratio of the 1C discharge capacity of the composite negative electrode material in the 200th week to the 1C discharge capacity in the first week.

[0101] Table 1 Physical and chemical properties test results of samples of embodiments and comparative examples

[0102]

[0103] It should be noted that the embodiments described herein are only partial embodiments of the present invention, rather than all implementation manners of the present invention. The embodiments are only exemplary, and their function is only to provide a more intuitive and clear way to understand the content of the present invention, rather than a limitation on the technical solutions described in the present invention. Without departing from the concept of the present invention, all other implementation manners that can be thought of by those of ordinary skill in the art without creative work, as well as other simple substitutions and various changes to the technical solutions of the present invention, all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-capacity fast-charging graphite composite negative electrode material, characterized in that: The following steps are involved: (1) anthracite and needle coke powder are mixed in a solid phase in a certain mass ratio and then placed in a high-temperature atmosphere furnace, and the mixture is heated to a pre-carbonization temperature of 750° C. to 900° C. under a protective gas atmosphere for pre-carbonization treatment for 1.5 h to 3.0 h. After the pre-carbonization treatment, the mixture is cooled to room temperature while maintaining the protective atmosphere to obtain a pre-carbonized porous carbon precursor; (2) placing the pre-carbonized porous carbon precursor into a fluidized bed reactor, heating it to an activation treatment temperature of 800°C to 1000°C under a protective gas atmosphere, and then introducing CO2 or water vapor as an activation gas to carry out an activation reaction for 0.5h to 4.0h. After the activation reaction is completed, the introduction of the activation gas is stopped, and the protective atmosphere is maintained to cool to room temperature to obtain a porous carbon material; (3) preparing a porous carbon material, a nitrogen-sulfur dopant and a solvent in a mass ratio of 100:(5-15):(900-200) into a mixed solution, mixing them evenly and injecting them into a high-pressure reactor. The high-pressure reactor is sealed and heated at a certain stirring speed to a reaction temperature of 150-280° C. and the reaction is maintained for 2.5-4.5 hours. The mixture is then cooled to room temperature and washed, dehydrated and dried to obtain a nitrogen-sulfur co-doped porous carbon material. (4) placing the obtained nitrogen-sulfur co-doped porous carbon material in a medium frequency induction graphitization furnace under a protective gas atmosphere and performing graphitization treatment at a graphitization treatment temperature of 1800° C. to 2300° C. for 1.5 h to 4.0 h. After the graphitization is completed, the protective atmosphere is maintained until the material is cooled, thereby obtaining a graphitized nitrogen-sulfur co-doped porous carbon material; (5) mixing the graphitized nitrogen-sulfur co-doped porous carbon material with an organic carbon source, a pre-lithiation agent, and a perovskite structure oxide in a mass ratio of 100:(10-30):(3-8):(2-5) and then putting the mixture into a kneader, kneading and coating the mixture under heating conditions, and putting the material into a tablet press after cooling at a certain molding pressure for a certain period of time to form a graphitized nitrogen-sulfur co-doped porous carbon composite material precursor body coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide; (6) Placing a graphitized nitrogen-sulfur co-doped porous carbon composite material precursor body coated with an organic carbon source / pre-lithiation agent / perovskite structure oxide in a high-temperature atmosphere furnace, heating the body to a calcination temperature of 750°C to 1000°C under a protective gas atmosphere, and calcining the body for 2.0h to 4.0h. After the calcination, the protective atmosphere is maintained in the furnace and the body is cooled to room temperature, and the body is crushed, screened, and graded to obtain the final product, a high-capacity fast-charging graphite composite negative electrode material.

2. The method for preparing a high-capacity fast-charging graphite composite negative electrode material according to claim 1, characterized in that: In step (1): The carbon content of the anthracite and needle coke is greater than 97%, the average particle size D50 of the anthracite and needle coke powder is 5.0-8.0 μm, and the mass ratio of the anthracite and needle coke powder is 100:(15-50); The solid phase mixing equipment adopts a V-type mixer, a drum mixer, a cone mixer or a mechanical fusion machine; The heating rate of the pre-carbonization treatment temperature is 5 to 10°C / min; The protective gas is one or more of nitrogen, helium, neon, argon, krypton or xenon, and its flow rate is 0.4-1.0m 3 / h; The anthracite is Ningxia Taixi anthracite.

3. The method for preparing a high-capacity fast-charging graphite composite negative electrode material according to claim 1, characterized in that: In step (2): The protective gas is one or more of nitrogen, helium, neon, argon, krypton or xenon, and its flow rate is 0.6-1.5m 3 / h; The activation treatment temperature has a heating rate of 5 to 10°C / min; The gas flow rate of the CO2 activated gas is 3 to 30 L / h, and the gas pressure of the water vapor activated gas is 0.1 to 0.5 MPa.

4. The method for preparing a high-capacity fast-charging graphite composite negative electrode material according to claim 1, characterized in that: In step (3): The solution solvents are ethanol, N-methylpyrrolidone, and dimethylformamide; The nitrogen-sulfur dopant is one or more of thiourea, ammonium thiocyanate, potassium thiocyanate, thioacetamide, polyaniline-polythiourea copolymer, and polypyrrole-polythioether copolymer; The stirring speed is 150-600 r / min.

5. The method for preparing a high-capacity fast-charging graphite composite negative electrode material according to claim 1, characterized in that: In step (4): The protective gas is one or both of helium and argon, and its flow rate is 1.0-2.5m 3 / h; The heating rate of the graphitization treatment temperature is 10-15°C / min.

6. The method for preparing a high-capacity fast-charging graphite composite negative electrode material according to claim 1, characterized in that: In step (5): The organic carbon source is one or more of polyvinyl alcohol, phenolic resin, epoxy resin, polyacrylonitrile, and styrene-butadiene rubber; The pre-lithiation agent is one or more of lithium carbonate, lithium nitride, lithium phosphate and lithium chloride, which have high thermal stability; The perovskite structure oxide is one or more of barium titanate, strontium titanate or barium strontium titanate; The temperature of the kneading and coating treatment is 120-180°C, and the kneading time is 1.5-4h; The pressure of the green compact is 6-20 MPa; The time of pressing the green sheets is 0.5 to 2.0 hours.

7. The method for preparing a high-capacity fast-charging graphite composite negative electrode material according to claim 1, characterized in that: In step (6): The heating rate of the calcination treatment temperature is 3-5°C / min; The protective gas is one or more of nitrogen, helium, neon, argon, krypton or xenon, and its flow rate is 0.4-1.0m 3 / h; The average particle size D50 of the high-capacity fast-charging graphite composite negative electrode material is 8.0 to 12.0 μm.

8. A high-capacity fast-charging graphite composite negative electrode material, characterized in that: The high-capacity fast-charging graphite composite negative electrode material is prepared by the preparation method as described in claims 1 to 7. The high-capacity fast-charging graphite composite negative electrode material is composed of disordered and uniformly distributed graphitized nitrogen-sulfur co-doped coal-based and needle-shaped coke-based porous carbon particles, and a pre-lithiation agent / perovskite structure oxide / amorphous carbon complex coated on the surface of the graphitized nitrogen-sulfur co-doped porous carbon material, and a pre-lithiation agent / perovskite structure oxide / amorphous carbon complex bridged around the coated graphitized nitrogen-sulfur co-doped porous carbon material.

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