Recycled silicon-carbon anode material for lithium-ion batteries and method and use thereof

Abstract

The application belongs to the field of waste battery material recycling, and particularly relates to a method for repairing waste silicon-carbon negative electrode material. The waste silicon-carbon negative electrode material is subjected to acid treatment to obtain acid-treated material. The acid-treated material and a compound of formula 1 are mixed in liquid phase, and then are closed in a pressure-resistant container to perform first-stage heat treatment to obtain first-stage heat-treated material. The first-stage heat-treated material is subjected to second-stage heat treatment in an oxygen-containing atmosphere to obtain second-stage heat-treated material. The second-stage heat-treated material is subjected to acid pickling and carbon coating to obtain repaired silicon-carbon negative electrode material. The application also discloses the material obtained by the method and application of the material. The recycled material has excellent electrochemical performance, particularly excellent high-area-load electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium-ion battery recycling, and specifically relates to a method for efficient recycling and structural repair of waste silicon-carbon anode materials. Background Technology

[0002] Since its invention in the 1970s, lithium-ion batteries have developed rapidly and are now widely used in portable electronic devices, transportation, energy storage power stations, and aerospace. Graphite is currently the mainstream anode material. However, with the development and widespread application of 8-series and 9-series high-nickel ternary cathode materials, the specific capacity of traditional graphite anodes has approached their theoretical capacity, making it difficult to meet the current demand for high-energy-density lithium-ion batteries in the power and energy storage markets. Silicon anodes, due to their ultra-high theoretical capacity (4200 mAh / g), are considered the most effective and feasible material for improving the electrochemical performance of lithium-ion batteries. To overcome the problems of large variations in the lithium insertion / extraction system, poor conductivity, and unstable surface solid electrolyte film in silicon anodes, silicon, graphite, and carbon are commonly used to construct silicon-carbon composite anode materials.

[0003] Currently, the production of silicon-based composite anode materials is mainly concentrated in China, Japan, and South Korea, with China taking the lead. In recent years, BTR, Shin-Etsu Chemical, and Daejoo of South Korea have accounted for nearly 80% of global silicon-based anode shipments. Silicon-carbon composite materials (silicon-carbon anodes) are the fastest-growing preparation method in industrialization due to their advantages such as good stability, small volume change, and excellent conductivity. The sponge silicon anode released by GAC Group and the silicon anode patents held by SiILion, acquired by Tesla in 2021, are essentially composite structures formed by combining silicon and carbon materials.

[0004] The global market for silicon-based anode materials reached $433 million in 2022 and is projected to reach $4.254 billion by 2029, representing a compound annual growth rate (CAGR) of 41.89% (2023-2029). Due to its relatively high price compared to artificial graphite anode materials, silicon-based anode materials are currently primarily used in consumer electronics and power tools, with limited application in power batteries. However, with advancements in nano-silicon production technology and corresponding cost reductions, the application scale of silicon-carbon composite anode materials will be substantial. Simultaneously, developing efficient recycling and structural / functional restoration technologies for failed silicon-carbon anode materials from retired lithium-ion batteries is crucial for resource recycling and environmental protection. Currently, the recycling of spent lithium-ion batteries mainly focuses on recovering valuable metals from the cathode and graphite from the anode; research on the recycling of silicon-carbon anode materials is limited, the technology is not mature, and related technological reserves are insufficient. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this invention is to provide a method for preparing silicon-carbon-based regenerated active materials using silicon-carbon anode waste, with the aim of utilizing silicon-carbon waste regeneration to prepare high-performance anode active materials.

[0006] The second objective of this invention is to provide a silicon-carbon waste-based recycled active material obtained by the method and its application in lithium secondary batteries.

[0007] A third objective of this invention is to provide a lithium secondary battery comprising the aforementioned silicon-carbon waste-based recycled active material, as well as its negative electrode and negative electrode material.

[0008] The failed silicon-carbon anode material used in this invention suffers from several defects. During repeated charge-discharge cycles, a solid electrolyte film forms on the particle surface, and structural defects develop in the graphite microstructure. Furthermore, the silicon particles expand and pulverize during repeated charge-discharge cycles. Additionally, impurities are introduced into the anode powder during upstream battery crushing and sieving, leading to material performance degradation and making direct reuse difficult. Moreover, the recovered silicon-carbon material, due to limitations in the repair process, struggles to meet stability requirements under high load conditions. To address these issues, this invention provides the following solution:

[0009] A method for repairing waste silicon-carbon anode materials, comprising the following steps:

[0010] Step (1): The waste silicon-carbon anode material (also known as waste silicon-carbon anode material) is acid-treated to obtain acid-treated material;

[0011] Step (2): Mix the acid-treated material and the liquid phase of the compound of Formula 1 and seal them together in a pressure-resistant container for the first stage of heat treatment to obtain the first stage heat-treated material. Then, carry out the second stage heat treatment in an oxygen-containing atmosphere to obtain the second stage heat-treated material.

[0012]

[0013] In Formula 1, R1 is phenyl, substituted phenyl, C2-C20 alkyl, substituted alkyl or F; R2-R4 are individually C1-C10 alkyl, C1-C10 alkoxy, phenyl or halogen; the substituents in the substituted phenyl and substituted alkyl are halogen, alkoxy, phenyl, cyano or nitro.

[0014] Step (3): The two-stage heat-treated material is pickled and carbon-coated to obtain the repaired silicon-carbon anode material.

[0015] To address the problem of the difficulty in recycling and regenerating high-performance active materials from long-term cycle-failed waste silicon-carbon anode materials, this invention innovatively treats the waste silicon-carbon anode materials with acid, then performs a first-stage liquid-phase heat treatment with the assistance of an additive of Formula 1, followed by a second-stage heat treatment in an oxygen-containing atmosphere. This process helps to repair the damaged structure of the waste silicon-carbon materials and form a protective layer with a suitable pore structure. Further acid washing and carbon coating treatments can then yield a regenerated active material with excellent electrochemical performance, especially exhibiting excellent stability even under high loading.

[0016] In this invention, the waste silicon-carbon anode material is the material stripped from the anode of a waste battery that uses silicon-carbon material as the anode active material.

[0017] The waste battery can be any battery containing a silicon-carbon negative electrode, such as a waste lithium-ion battery.

[0018] In this invention, the silicon-carbon material can be a composite material containing silicon (elemental silicon, oxides, and other silicon-containing components introduced during charge-discharge cycles, such as silicates) and carbon (mainly at least one of amorphous and graphitized carbon). The composite form of the two can be arbitrary, for example, it can be a physical mixture, or they can be mutually loaded or coated.

[0019] Preferably, the waste silicon-carbon material may contain, in addition to the negative electrode active material, at least one of the following: conductive agent, binder, current collector, electrolyte, and positive electrode material element.

[0020] The content of negative electrode active material in the waste silicon-carbon material described in this invention is not particularly required. Considering the processing value, it can be controlled at more than 50 wt.%, and more specifically, it can be 60-90 wt%.

[0021] In this invention, in step (1), the acid solution in the acid treatment stage is an aqueous solution of at least one of hydrochloric acid, sulfuric acid, and nitric acid. As an example embodiment, the concentration of the solute in the acid solution is 0.05–5 M, and more preferably 0.5–2 M. An oxidizing agent may also be added to the acid solution, preferably hydrogen peroxide (its content can be, for example, 5–25 vol%). The liquid-to-solid ratio (mass ratio of solution to powder) in the acid treatment stage is 1–10:1. The temperature in the acid treatment stage is 25–40°C.

[0022] This invention also found that the acid treatment stage is carried out under ultrasonic assistance, which helps to further combine with subsequent processes and can further improve the electrochemical performance of the repaired silicon-carbon materials, especially the electrochemical performance under high loading.

[0023] In this invention, the acidified material is pre-treated in a liquid phase system with the assistance of Formula 1, followed by solid-liquid separation. The resulting solid is then subjected to a second heat treatment in an oxygen-containing atmosphere. This process can unexpectedly repair the damaged structure. Moreover, it facilitates the physicochemical modification of the microstructure, thereby improving the electrochemical performance of the repaired material. In particular, it can better solve the problem of large volume expansion caused by high silicon loading, and can also obtain excellent high areal loading electrochemical performance.

[0024] The study also found that controlling the first stage of heat treatment (Formula 1) and the solvent can be combined with the subsequent second stage of heat treatment under an oxygen-containing atmosphere and other processes to further improve the repair effect of waste silicon-carbon materials and help to further improve the electrochemical performance under high loading.

[0025] In the compound of Formula 1, R1 to R4 contain at least F and a benzene ring. The F can be directly attached to Si, attached to the benzene ring, or attached to other substituents; in this invention, the preferred structure may unexpectedly exhibit superior electrochemical performance.

[0026] Preferably, Formula 1 comprises at least one of the following structural compounds;

[0027]

[0028] In the aforementioned Formula 1-C, R is a C1 to C6 alkyl group.

[0029] In this invention, the mass ratio of the compound of Formula 1 to the acid-treated material can be 0.05 to 2:100, preferably 1 to 2:100.

[0030] In this invention, step (2): the solvent in the liquid phase mixing stage is at least one of water and organic solvent;

[0031] The organic solvent is a water-miscible solvent, preferably at least one of C1-C4 alcohols, acetone, and THF;

[0032] Preferably, the solvent is a mixture of water and organic solvent, and more preferably a mixture of water and ethylene glycol. Studies have found that the preferred system can achieve better modification effects and help to further improve the performance of the prepared material.

[0033] More preferably, the volume ratio of water to organic solvent in the solvent is 100:5 to 20, and more preferably 100:8 to 12;

[0034] In this invention, the liquid mixture is filled into a pressure-resistant container, sealed, and then heated to carry out the reaction. There are no special requirements for the content of the liquid mixture; considering the preparation efficiency, it can be 30-90 v%, and more specifically, 50-75 v%.

[0035] Preferably, the temperature of the first heat treatment is 120–220°C, more preferably 150–200°C, and the treatment time is 2–6 hours, preferably 2–4 hours.

[0036] In this invention, the oxygen-containing atmosphere is at least one of oxygen, air, a mixture of oxygen and dilution gas, or a mixture of air and dilution gas. The dilution gas is, for example, nitrogen, an inert gas, or other gas that cannot participate in the reaction.

[0037] Preferably, in the oxygen-containing atmosphere, the volume concentration of oxygen is 5-30%, and more preferably 10-25%.

[0038] Preferably, the temperature of the second heat treatment is 300–600°C, more preferably 350–550°C;

[0039] Preferably, the heat treatment time is 0.5 to 3 hours, more preferably 1 to 2 hours;

[0040] Preferably, the second heat treatment process includes two heat preservation platforms, wherein the oxygen concentration of the first heat preservation platform is 5-15 vol%, the temperature is 300-350°C, and the atmosphere of the second heat preservation platform is air, the temperature is 380-450°C;

[0041] Preferably, the time for the first insulation platform and the second insulation platform is 0.5 to 1.5 hours, respectively.

[0042] In this invention, the acid solution used in step (3), the pickling stage, has no special requirements; for example, it can be a solution containing HF. Its concentration can be, for example, 0.1–2 M.

[0043] The pickling process can be carried out at room temperature, either by pulping and filtration or by rinsing.

[0044] In this invention, after pickling, water washing can be selectively performed, preferably with a neutral filtrate during water washing, followed by drying to obtain the pickled material.

[0045] In this invention, the pickled material can be carbon-coated using known processes to obtain the recycled material. For example, in the carbon-coating process of this invention, the pickled material and a carbon source are mixed and heated for carbon-coating; or, the pickled material is heated in a carbon source atmosphere for carbon-coating.

[0046] As an example, the carbon source is a liquid carbon source and / or a solid carbon source with a melting point of 100–400°C. The solid carbon source is, for example, at least one of asphalt, ABS, and PLA. The liquid carbon source can be a carbon source that is itself liquid or a soluble carbon source solution. The carbon source that is itself liquid is, for example, at least one of coal tar and liquid-phase resin; the soluble carbon source solution is, for example, a solution of at least one of glucose and flour.

[0047] In this invention, the weight ratio of pickling material to carbon source is 100:5 to 12;

[0048] Preferably, the carbon coating process includes a first heat preservation process at temperature T1 and a second heat preservation process at temperature T2;

[0049] Preferably, the temperature of T1 is 200–500°C, more preferably 200–400°C;

[0050] Preferably, the temperature of T2 is 800–1050°C, more preferably 900–1000°C;

[0051] Preferably, the first heat preservation process is at normal pressure, and the pressure of the second heat preservation process is greater than 1 atm, preferably 1.5 to 4 atm.

[0052] There are no specific time requirements for the carbon coating process, as long as the organic matter is fully carbonized. Considering the preparation efficiency, it can be more than 1 hour, and further can be 2 to 20 hours. When the preferred two-stage carbon coating process is used, the holding time for each stage can be 1 to 10 hours.

[0053] The present invention also provides a repaired silicon-carbon anode material prepared by the repair method described above.

[0054] In this invention, the method described can endow the prepared material with special physicochemical properties, and the material with special properties prepared by this method can unexpectedly exhibit excellent electrochemical performance, especially improving the electrochemical stability under high loading.

[0055] The present invention also includes the application of the repaired silicon-carbon anode material obtained by the repair method described above in the preparation of lithium-ion batteries.

[0056] As a typical application approach, the present invention also provides a negative electrode for a lithium-ion battery, including a current collector and a negative electrode material composited on its surface, wherein the negative electrode material includes an active material, and the active material includes a repaired silicon-carbon negative electrode material prepared by the repair method of the present invention.

[0057] Preferably, the negative electrode material further comprises a binder and a conductive agent;

[0058] In this invention, the content of the repaired silicon-carbon anode material in the anode material is not particularly required, for example, it can be above 50 wt.%, and more specifically, it can be 60-95 wt%.

[0059] In the aforementioned negative electrode, the electrode sheet compaction density of the repaired silicon-carbon negative electrode material can reach 1.58 g / cm3 or higher. Considering the excellent inhibition of system expansion and structural stability of the active material of the present invention, the areal loading can be increased to preferably 1.62-1.68 g / cm3 or higher.

[0060] As a solution to the same application concept, the present invention also provides a lithium-ion battery comprising a negative electrode containing the silicon-carbon negative electrode material repaired according to the present invention.

[0061] In this invention, the repaired silicon-carbon anode material can be used as an active anode material, and based on known processes and principles, the desired lithium-ion battery and its anode components can be prepared. That is, the lithium-ion battery and its anode described in this invention, apart from containing the repaired silicon-carbon anode material, all other components and structural parts can be known.

[0062] The beneficial effects of the technical solution of this invention are as follows:

[0063] This invention innovatively involves acid treatment of waste silicon-carbon anode material, followed by a novel pre-treatment in a liquid phase with an additive of Formula 1, and then a second-stage heat treatment in an oxygen-containing atmosphere. This process facilitates the repair of the damaged structure of the waste silicon-carbon material and forms a protective layer with a suitable pore structure. Further acid washing and carbon coating treatments effectively modify the damaged structure of the silicon-carbon and facilitate the repair and modification of its physicochemical properties. Research by this invention shows that the material obtained using the repair method described herein exhibits excellent stability even under high loading conditions.

[0064] In this invention, further optimization and control of the structure of Formula 1 and the solvent system in the first heat treatment stage, and / or the mechanism of the second heat treatment stage, can further improve the control of the composition of waste materials and the repair and modification of the physicochemical structure, which helps to further improve the resistance to system expansion and structural stability of the prepared materials, and can further improve the electrochemical performance of the prepared materials under high surface loading. Attached Figure Description

[0065] Figure 1 Example 1: SEM image of the raw material of the failed silicon-carbon anode material;

[0066] Figure 2 SEM image of the regenerated silicon-carbon sample obtained in Example 1; Detailed Implementation

[0067] The following examples illustrate the specific steps of the present invention. It should be understood that these examples are merely illustrative and not intended to limit the scope of the invention in any way. Various processes and methods not described in detail in this invention are conventional methods known in the art.

[0068] In this invention, the waste silicon-carbon material can be obtained by stripping it from the negative electrode of a waste lithium-ion battery using known methods. The silicon-carbon active material is a composite containing silicon and carbon (graphite and / or amorphous carbon).

[0069] In this invention, there are no special requirements for the original capacity and silicon content of the failed silicon-carbon anode waste. Considering the maximization of process economic value, the silicon content in the failed silicon-carbon anode waste is preferably ≥10%, and can be 10-30%.

[0070] In this invention, there are no special requirements for the content of silicon-carbon anode active material in the waste silicon-carbon material obtained by stripping. Considering the recycling value of the process, it can be above 50 wt%, for example, it can be 50 to 90 wt%.

[0071] In this invention, waste silicon-carbon material is innovatively treated with acid, then subjected to a first stage of liquid-phase treatment and a second stage of heat treatment in an oxygen-containing atmosphere, followed by acid washing and carbon coating to obtain repaired silicon-carbon material.

[0072] In this invention, as an example, it may specifically include the following steps:

[0073] S1. First, the failed silicon-carbon anode powder is placed in an acidic solution for ultrasonic treatment, then solid-liquid separation is performed, and the resulting filter cake is dried.

[0074] S2. Place the obtained dried powder (acid-treated material) in a neutral liquid medium, add a certain amount of Formula 1, and carry out the first stage of heat treatment reaction. After the reaction is completed, the solid and liquid are separated, and the resulting filter cake is dried.

[0075] S3. Place the obtained material in an oxygen-containing atmosphere for heat treatment (second stage heat treatment);

[0076] S4. Place the heat-treated material in an acid solution for pickling;

[0077] S5. The pickled material and the liquefiable carbon source are subjected to two-stage heat treatment to finally obtain the repaired silicon-carbon composite anode material.

[0078] The acidic solution mentioned in S1 refers to one or more of hydrochloric acid, sulfuric acid, nitric acid, etc., with a concentration of 0.05 to 2M; preferably, it is a mixed solution of hydrochloric acid and hydrogen peroxide, wherein the volume fraction of hydrogen peroxide is 0.5 to 10%.

[0079] The ultrasonic treatment described in S1 is a process performed under the action of ultrasonic waves, with a treatment temperature of 20-60℃ and a treatment time of 0.5-6h.

[0080] In S2, the mass ratio of Formula 1 to powder is 0.05 to 2:100.

[0081] The neutral liquid medium described in S2 is water or a water-ethylene glycol mixed solvent. Preferably, the volume ratio of water to ethylene glycol is 100:5 to 20.

[0082] The first stage of heat treatment described in S2 has a treatment temperature of 120–220°C and a treatment time of 2–6 hours.

[0083] The oxygen-containing atmosphere described in S3 is air, or an oxygen volume concentration of 5-30%, with the remainder being one or more of nitrogen, hydrogen, helium, argon, etc.; the heat treatment temperature is 300-600℃, and the treatment time is 0.5-3h.

[0084] The acid concentration described in S4 is 0.1–2 M, and the treatment time is 0.5–2 h.

[0085] The liquefiable carbon source described in S5 is a precursor that can be melted by heating to 100-400℃, such as asphalt, ABS, PLA, etc.; or a carbon source precursor that is itself liquid, such as coal tar, liquid resin, etc.; or a carbon source that can be dissolved in certain solvents, such as glucose, flour, etc.

[0086] The mass ratio of the pickled material to the liquefiable carbon source described in S5 is 100:5 to 12.

[0087] The two-stage heat treatment described in S5 consists of a first stage of pressurized heat treatment and a second stage of atmospheric pressure heat treatment; the first stage of pressurized heat treatment has a temperature of 200–500°C and a pressure greater than 1 atm; the second stage of atmospheric pressure heat treatment has a temperature of 800–1050°C.

[0088] The present invention also provides the application of the regenerated active material based on the failed silicon-carbon anode waste obtained by the method, which is used as an anode active material for the preparation of lithium secondary batteries.

[0089] In this invention, recycled materials can be used as negative electrode active materials to prepare lithium secondary batteries and their negative electrodes and negative electrode materials using existing conventional methods.

[0090] The present invention also provides a lithium secondary battery anode, comprising a current collector and an anode material loaded thereon, characterized in that the anode material comprises a regenerated active material based on waste silicon-carbon anode material obtained by the method described in the present invention.

[0091] In this invention, the current collector in the negative electrode can be of a type known in the industry.

[0092] In this invention, the negative electrode material, in addition to the active material, may also contain at least one of a conductive agent and a binder. Both the conductive agent and the binder can be components known in the industry.

[0093] In this invention, the content of the active material in the negative electrode material can be 60-95 wt.%.

[0094] The present invention also provides a lithium secondary battery, comprising a positive electrode, a separator and a negative electrode sequentially combined, wherein the negative electrode is the negative electrode containing the regenerated active material as described in the present invention.

[0095] In this invention, the lithium secondary battery, apart from containing the negative electrode active material recycled by this invention, can have other conventional components and structural parts.

[0096] The following are typical examples:

[0097] In this invention, the waste silicon-carbon material can be any silicon-carbon-containing material stripped from waste batteries. The following example, as a typical embodiment, unless otherwise stated, uses failed silicon-carbon anode powder obtained from the anode sheets of waste lithium-ion batteries before repair. It contains silicon-carbon anode active material, as well as conductive agents, binders, and other components that make up the anode material. The content of the active material is between 75 and 85 wt.%. SEM images of the silicon-carbon anode active material before repair are shown below. Figure 1 The silicon content is between 10 and 20 wt.%.

[0098] In this invention, there are no special requirements for the liquid-to-solid ratio during steps 1 and 2. Considering cost, it can be controlled within the range of 2 to 10:1 (mass ratio of solution to powder). There are no special requirements for the temperature during the processing. Considering the simplicity of the process, it can be at room temperature, for example, 25 to 40°C.

[0099] In this invention, there are no special requirements for the heating rate, for example, it can be 1 to 10 °C / min, and for the sake of preparation efficiency, it can be 4 to 6 °C / min.

[0100] Example 1

[0101] Step (1): Remove the failed silicon-carbon anode powder (see SEM image). Figure 1 After being fully dried, the mixture is broken up and placed in 1M hydrochloric acid (acid) and 5% hydrogen peroxide solution. After ultrasonic treatment in an ultrasonic disperser for 2 hours, the solid and liquid are separated and the filter cake is dried.

[0102] Step (2): Disperse the above powder in a mixed solvent of water and ethanol (treatment medium, water to ethanol volume ratio of 10:1, and the liquid-solid ratio of powder to mixed solvent of 5-10 ml / g), and add 1% (based on the weight of the powder in Step 1) of additive (Formula A). After stirring evenly, the mixture is sealed in a pressure-resistant device (the filling volume is 60-70% of the filling chamber volume of the pressure-resistant device), and the temperature is kept at 180℃ for 3 hours. After the reaction is completed, the solid and liquid are separated, the filter cake is washed, dried, and broken up for later use.

[0103] Step (3): Place the powder obtained in the previous step in a muffle furnace, heat it to 400°C at a rate of 5°C / min under an air atmosphere, and keep it at that temperature for 2 hours.

[0104] Step (4): Place the obtained powder in a 0.5M hydrofluoric acid aqueous solution, react at room temperature for 0.5h, then separate the solid and liquid, wash the filter cake with water until the filtrate is neutral, dry it, and break it up for later use.

[0105] Step (5): Mix the obtained powder with 5% of its weight of coal tar evenly and place it in an atmosphere furnace. Under the temperature conditions of 220℃ (marked as T1, heating rate of 5℃ / min), set the system pressure to 2atm and maintain it under these conditions for 1h. Then, program the temperature to 1000℃ (marked as T2, heating rate of 5℃ / min) and maintain it under these conditions for 2h. After cooling to room temperature, the regenerated silicon-carbon anode material is obtained.

[0106] Regenerated silicon-carbon electrode: Regenerated silicon-carbon negative electrode material is used as the active material, and is mixed with conductive agent (50% acetylene black, 50% CNTs) and binder (50% CMC, 50% LA133) in a weight ratio of 92:4:4, then water is added to form a slurry, which is then coated onto a copper current collector and dried to obtain the working electrode (the electrode sheet compaction density is 1.65 g / cm3).

[0107] CR2025 coin cells were assembled in an argon-filled dry glove box using the regenerated silicon-carbon electrode as the working electrode, lithium metal as the negative electrode, 1 mol / L LiPF6 EC / EMC (volume ratio 1:1, with 10% FEC added) as the electrolyte, and a PE-PP composite membrane as the separator. Electrochemical performance was tested at room temperature within a voltage range of 0.001-2.0V and a charge / discharge rate of 0.2C: the initial reversible capacity was 512.7 mAh / g, the coulombic efficiency was 92.1%, and the capacity retention after 200 cycles was 95.3%.

[0108] Example 2

[0109] Compared with Example 1, the only difference is that the processing conditions in step (1) are changed; other operations and parameters are the same as in Example 1. The experimental groups are as follows:

[0110] Group A: The acid used is an equal amount of 2M nitric acid.

[0111] Group B: Lack of ultrasound treatment, and treatment time extended to 4 hours;

[0112] Electrochemical performance was tested according to the method in Example 1, and the results are as follows:

[0113] Group A: Initial reversible capacity was 511.3 mAh / g, coulombic efficiency was 91.8%; capacity retention after 200 cycles was 94.8%.

[0114] Group B: Initial reversible capacity was 502.5 mAh / g, coulombic efficiency was 91.3%; capacity retention after 200 cycles was 93.6%.

[0115] Example 3

[0116] Compared with Example 1, the only difference is that the parameters in step 2 are changed; all other operations and parameters are the same as in Example 1. The experimental groups are as follows:

[0117] Group A: The treatment medium used is pure water;

[0118] Group B: The treatment medium used is water-ethylene glycol with a volume ratio of 10:1.

[0119] Group C: The additive used is formula B

[0120] Group D: Compared with Group B, the additive used is a mixture of Formula A and Formula B in a weight ratio of 1:0.2, and the amount of additive added is 0.8 wt.% compared with the powder in step 1.

[0121] Group E: Processing temperature 160℃, time 4h.

[0122] All other operations and parameters were the same as in Example 1, and the electrochemical performance was tested according to the method in Example 1. The results were as follows:

[0123] A: The initial reversible capacity is 510.1 mAh / g with a coulombic efficiency of 91.1%; the capacity retention rate after 200 cycles is 92.1%.

[0124] B: The initial reversible capacity is 524.2 mAh / g, with a coulombic efficiency of 93.1%; the capacity retention rate after 200 cycles is 96.0%.

[0125] C: The initial reversible capacity is 518.9 mAh / g, with a coulombic efficiency of 91.8%; the capacity retention rate after 200 cycles is 95.6%.

[0126] D: Initial reversible capacity is 525.3 mAh / g, coulombic efficiency is 93.6%; capacity retention after 200 cycles is 96.5%.

[0127] E: Initial reversible capacity is 522.3 mAh / g, coulombic efficiency is 91.6%; capacity retention after 200 cycles is 93.4%.

[0128] As demonstrated in Examples 1 and 3, using a combination of Formula A and Formula B, and / or a water-ethylene glycol solvent system, can unexpectedly further improve the repair and regeneration effect, and can further improve the electrochemical performance of the prepared material.

[0129] Example 4

[0130] Compared with Example 1, the only difference is that the operating parameters of step (3) are changed, and the experimental groups are as follows:

[0131] A: The processing atmosphere used is 10% oxygen and 90% nitrogen;

[0132] B: The heat treatment temperature is 550℃ and the time is 0.5h.

[0133] C: Other preferred solutions, for example, two-stage treatment: preheating at 320°C for 1 hour in a 10% O2-Ar atmosphere, followed by heating at 400°C for 1 hour in an air atmosphere;

[0134] All other operations and parameters were the same as in Example 1, and the electrochemical performance was tested according to the method in Example 1. The results were as follows:

[0135] A: The initial reversible capacity is 513.6 mAh / g, the coulombic efficiency is 91.9%, and the capacity retention rate after 200 cycles is 94.1%.

[0136] B: The initial reversible capacity is 518.5 mAh / g, the coulombic efficiency is 92.2%, and the capacity retention rate after 200 cycles is 94.0%.

[0137] C: The initial reversible capacity is 533.2 mAh / g, the coulombic efficiency is 93.5%, and the capacity retention rate after 200 cycles is 96.6%.

[0138] Example 5

[0139] Compared with Example 1, the only difference is that in step 5, the carbon source used is asphalt (addition amount is 10%), the temperature of T1 is 400°C, the pressure is 1.5 atm, and the treatment time at this temperature and pressure is 1.5h; T2 is 950°C, and the heat preservation time at this temperature is 3h.

[0140] All other operations and parameters were the same as in Example 1, and the electrochemical performance was tested according to the method in Example 1. The results were: the initial reversible capacity was 518.5 mAh / g, the coulombic efficiency was 92.1%, and the capacity retention rate after 200 cycles was 94.6%.

[0141] Comparative Example 1

[0142] Compared to Example 1, the only difference is that step 1 is omitted.

[0143] The same tests were performed on the obtained material, and the results showed that the initial reversible capacity was 387.9 mAh / g and the coulombic efficiency was 73.5%.

[0144] Comparative Example 2

[0145] Compared to Example 1, the only difference is that step 2 is omitted.

[0146] The same tests were performed on the obtained material, and the results showed that the initial reversible capacity was 321.6 mAh / g and the coulombic efficiency was 64.3%.

[0147] Comparative Example 3

[0148] Compared with Example 1, the only difference is that Formula 1 is not added in step 2.

[0149] The same tests were performed on the obtained material, and the results showed that the initial reversible capacity was 335.7 mAh / g and the coulombic efficiency was 66.3%.

[0150] Comparative Example 4

[0151] Compared with Example 1, the only difference is that in step 2, the additive is a comparative formula C with an equal amount of additive. Other operations and parameters are the same as in Example 1;

[0152] The same tests were performed on the obtained material, and the results showed that the initial reversible capacity was 342.6 mAh / g and the coulombic efficiency was 71.7%.

[0153] Comparative Example 5

[0154] Compared to Example 1, the only difference is that step 3 is not performed.

[0155] The same tests were performed on the obtained material, and the results showed that the initial reversible capacity was 351.5 mAh / g and the coulombic efficiency was 73.3%.

[0156] Comparative Example 6

[0157] Compared to Example 1, the only difference is that step 3 uses an oxygen-free high-purity argon atmosphere.

[0158] The same tests were performed on the obtained material, and the results showed that the initial reversible capacity was 355.9 mAh / g and the coulombic efficiency was 75.2%.

[0159] The capacity and coulombic efficiency of the materials in Comparative Examples 1 to 6 decreased significantly, and the capacity retention rate after 100 cycles all decreased to below 70%.

Claims

1. A method for repairing a waste silicon-carbon negative electrode material, characterized by the steps of The method comprises the following steps: Step (1): acid treatment of the waste silicon-carbon negative electrode material to obtain an acid-treated material; Step (2): mixing the acid-treated material and a compound of formula 1 in a liquid phase, then sealing them in a pressure-resistant container for first-stage heat treatment, obtaining a first-stage heat-treated material, and then performing second-stage heat treatment in an oxygen-containing atmosphere to obtain a second-stage heat-treated material; Formula 1 In Formula 1, R1 is phenyl, substituted phenyl, or C2~C1. 20 Alkyl, substituted alkyl, or F; R2~R4 are individually C1~C 10 Alkyl, C1~C 10 The alkoxy, phenyl, or halogen; the substituents in the substituted phenyl and substituted alkyl groups are halogen, alkoxy, phenyl, cyano, or nitro; wherein R1-R4 at least contain F and a benzene ring; Step (3): acid washing and carbon coating of the second-stage heat-treated material to obtain a repaired silicon-carbon negative electrode material.

2. The method for repairing the waste silicon-carbon negative material according to claim 1, characterized in that, The waste silicon-carbon negative electrode material is a material peeled from the negative electrode of a waste battery using silicon-carbon material as the negative electrode active material.

3. The method for repairing the waste silicon-carbon negative material according to claim 2, characterized in that, The waste battery is a waste lithium ion battery.

4. The method for repairing the waste silicon-carbon negative material according to claim 2, characterized in that, The waste silicon-carbon negative electrode material may further contain at least one of a conductive agent, a binder, a current collector, an electrolyte, and a positive electrode material element in addition to the negative electrode active material.

5. The method for repairing the waste silicon-carbon negative material according to claim 2, characterized in that, The content of the negative electrode active material in the waste silicon-carbon material is greater than 50 wt.%.

6. The method for repairing the waste silicon-carbon negative material according to claim 1, characterized in that, In step (1), the acid solution in the acid treatment stage is at least one of an aqueous solution of hydrochloric acid, sulfuric acid, and nitric acid.

7. The method for repairing the waste silicon-carbon negative material according to claim 6, characterized in that, The concentration of the solute in the acid solution is 0.05-5 M.

8. The method for repairing the waste silicon-carbon negative material according to claim 6, characterized in that, An oxidizing agent is added to the acid solution.

9. The method for repairing the waste silicon-carbon negative material according to claim 8, characterized in that, The oxidizing agent is hydrogen peroxide.

10. The method for repairing the waste silicon-carbon negative material according to claim 1, characterized in that, The temperature in the acid treatment stage is 25-40°C.

11. The method of claim 1, wherein the old silicon-carbon negative material is a silicon-carbon composite material. The acid treatment stage is performed under ultrasonic assistance.

12. The method of claim 1, wherein the old silicon-carbon negative material is a silicon-carbon composite material. Formula 1 contains at least one of the following compounds: Formula 1-A Formula 1-B Formula 1-C In formula 1-C, R is an alkyl group with 1-6 carbon atoms.

13. The method of claim 1, wherein the old silicon-carbon negative material is a silicon-carbon composite material. In step (2), the solvent in the liquid phase mixing stage is at least one of water and an organic solvent. The organic solvent is a water-miscible solvent.

14. The method for repairing a waste silicon-carbon negative material according to claim 13, wherein The organic solvent is at least one of an alcohol with 1-4 carbon atoms, acetone, and THF.

15. The method for repairing the waste and old silicon-carbon negative material according to claim 14, characterized in that, The solvent is a mixed solvent of water and an organic solvent.

16. The method for repairing a waste silicon-carbon anode material according to claim 15, wherein The solvent is a mixed solvent of water and ethylene glycol.

17. The method of claim 13, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. In the solvent, the volume ratio of water to the organic solvent is 100:5-20.

18. The method of claim 1, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. The temperature of the first heat treatment is 120-220°C, and the treatment time is 2-6 h.

19. The method of claim 1, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. The oxygen-containing atmosphere is at least one of oxygen, air, a mixture of oxygen and a dilution gas, and a mixture of air and a dilution gas.

20. The method of claim 1, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. In the oxygen-containing atmosphere, the volume concentration of oxygen is 5-30%.

21. The method of claim 1, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. The temperature of the second heat treatment is 300-600°C.

22. The method of claim 1, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. The heat treatment time is 0.5-3 h.

23. The method of claim 1, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. The second heat treatment process includes two holding platforms, wherein the oxygen concentration of the first holding platform is 5-15 vol%, and the temperature is 300-350°C; the atmosphere of the second holding platform is air, and the temperature is 380-450°C.

24. The method of claim 23, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. The time of the first holding platform and the second holding platform is 0.5-1.5 h, respectively.

25. The method of claim 1, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. In step (3), the acid solution used in the acid washing stage is a solution containing HF.

26. The method of claim 25, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. In the acid solution, the concentration of HF is 0.1-2 M.

27. The method of claim 1, wherein the waste silicon-carbon anode material is a waste silicon-carbon anode material of a lithium ion battery. In the carbon coating process, the acid-washed material is mixed with a carbon source and heated for carbon coating; or the acid-washed material is heated in a carbon source atmosphere for carbon coating.

28. The method for repairing waste silicon-carbon anode materials as described in claim 27, characterized in that, The carbon source is a liquid carbon source and / or a solid carbon source with a melting point of 100-400°C, and the solid carbon source is at least one of pitch, ABS, and PLA.

29. The method for repairing waste silicon-carbon anode materials as described in claim 28, characterized in that, The liquid carbon source is a liquid carbon source or a soluble carbon source solution, the liquid carbon source is at least one of coal tar and liquid resin, and the soluble carbon source solution is a solution in which at least one of glucose and flour is dissolved.

30. The method for repairing waste silicon-carbon anode materials as described in claim 27, characterized in that, The weight ratio of the pickling material to the carbon source is 100:5-12.

31. The method for repairing waste silicon-carbon anode materials as described in claim 27, characterized in that, The carbon coating process comprises a first holding process at T1 and a second holding process at T2.

32. The method for repairing waste silicon-carbon anode materials as described in claim 31, characterized in that, The temperature T1 is 200-500°C. The temperature T2 is 800-1050°C.

33. The method for repairing waste silicon-carbon anode materials as described in claim 32, characterized in that, The first holding process is under normal pressure, and the pressure of the second holding process is greater than 1 atm.

34. A repaired silicon-carbon negative electrode material prepared by the repairing method of any one of claims 1-33.

35. A negative electrode for a lithium-ion battery comprising a current collector and a negative electrode material complexed on the surface thereof, the negative electrode material comprising an active material, characterized in that, The active material comprises the repaired silicon-carbon negative electrode material prepared by the repairing method of any one of claims 1-33.

36. The anode of a lithium-ion battery of claim 35, wherein the carbon-based material is selected from the group consisting of graphite, hard carbon, soft carbon, and combinations thereof. The negative electrode material further comprises a binder and a conductive agent.

37. The anode of a lithium-ion battery of claim 36, wherein the carbon-based material is selected from the group consisting of graphite, hard carbon, soft carbon, and combinations thereof. The content of the repaired silicon-carbon negative electrode material in the negative electrode material is more than 50wt.%, and the surface loading of the repaired silicon-carbon negative electrode material is 1.58g / cm 3 The above.

38. The anode of a lithium-ion battery of claim 37, wherein the carbon-based material is selected from the group consisting of graphite, hard carbon, soft carbon, and combinations thereof. In the negative electrode material, the content of the repaired silicon-carbon negative electrode material is 60-95 wt.%. The surface loading of the repaired silicon-carbon negative electrode material is 1.62-1.68 g / cm 3 .

39. A lithium-ion battery, characterized by, The battery comprises the negative electrode of any one of claims 35-38.

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