A method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries and its application

Abstract

The present invention discloses a method for regenerating waste lithium-ion battery silicon-carbon negative electrode materials and its application, comprising the following steps: S1. Mixing waste lithium-ion battery silicon-carbon negative electrode materials with an alkaline substance and calcining them in a non-oxidizing atmosphere to obtain a calcined mixture; S2. Washing the calcined mixture until neutral, performing solid-liquid separation to obtain a graphite material and a silicon-containing solution; S3. Adjusting the pH of the silicon-containing solution to a level that allows silicate precipitation, heating the solution for reaction, performing solid-liquid separation, and collecting the silicic acid precipitate; S4. Mixing the silicic acid precipitate with silicon, grinding it into a micron-sized powder, calcining it under vacuum conditions, and collecting the generated silicon oxide; S5. Carbon-coating the silicon oxide and the graphite material obtained in step S2 to obtain a regenerated silicon-carbon negative electrode material. This method successfully converts waste silicon-carbon negative electrode materials into high-quality recycled materials that can be directly used in the production of new batteries.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to a method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries and applications thereof. Background Art

[0002] Lithium-ion batteries, with their significant advantages, including high energy and power density, excellent cycle stability, high operating voltage, outstanding safety performance, and environmental friendliness, have been widely and deeply applied in various fields, including electric vehicles, portable electronic devices, and energy storage systems. However, as consumable products, lithium-ion batteries inevitably have a limited service life. As their service life gradually exhausts, if a large number of scrapped batteries are not properly handled and recycled, the hazardous substances they contain may leak into the environment, posing a serious threat to soil, water sources, and ecosystems, and in turn affecting human health.

[0003] At the same time, key materials such as lithium, cobalt, copper, and silicon-carbon contained in used lithium batteries have demonstrated extremely high recycling value in an era of increasing global resource constraints. These materials are not only essential raw materials for manufacturing new batteries, but recycling them can also significantly reduce the need for virgin resource extraction, energy consumption, and environmental pollution. Therefore, the scientific and effective management and disposal of used lithium batteries can not only effectively alleviate environmental pressures and protect the ecological environment, but also achieve resource recycling, bringing significant environmental and economic benefits.

[0004] At present, the main focus of recycling waste lithium batteries is on the positive electrode materials and the metal elements therein, while there is relatively little research on the silicon-carbon materials for the negative electrode. Silicon-carbon materials have shown great application potential in high-energy-density lithium-ion batteries due to their theoretical capacity of up to 4200mAh / g and a low platform potential of 0.5V. However, silicon-carbon materials undergo significant volume expansion during the charge and discharge cycle, causing the negative electrode materials to crack or even pulverize after long-term cycling. This not only destroys the structural stability of the battery, but also forms a thick solid electrolyte interface (SEI) film on the surface of the negative electrode material, further hindering the transmission of lithium ions and resulting in a large loss of silicon and lithium elements. At the same time, during the battery cycle and disassembly process, silicon-carbon negative electrode materials may also deposit and adsorb other metal elements, increasing the difficulty of recycling.

[0005] Therefore, collected waste silicon-carbon anode materials require further processing using advanced treatment technologies to restore their original performance and quality. This not only helps meet the recycling and reuse requirements of silicon-carbon anode materials and improves resource utilization, but also reduces the negative environmental impact of waste batteries and promotes the sustainable development of the lithium-ion battery industry. However, few relevant reports exist in the prior art. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for regenerating silicon-carbon negative electrode materials from waste lithium-ion batteries, which can effectively regenerate silicon-carbon negative electrode materials.

[0007] The present invention also proposes an application of the above method.

[0008] According to the first embodiment of the present invention, the method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries comprises the following steps:

[0009] S1, mixing the waste lithium-ion battery silicon-carbon negative electrode material with an alkaline substance, and calcining the mixture in a non-oxidizing atmosphere to obtain a calcined mixture;

[0010] S2, washing the calcined mixture until it is neutral, and performing solid-liquid separation to obtain a graphite material and a silicon-containing solution;

[0011] S3, adjusting the pH of the silicon-containing solution to a level that causes silicate precipitation, reacting under heating, separating the solid and liquid, and collecting the silicic acid precipitate;

[0012] S4, mixing the silicic acid precipitate with silicon, grinding the mixture into a micron-sized powder, calcining the mixture under vacuum conditions, and collecting the generated silicon oxide;

[0013] S5. Carbon-coating the silicon monoxide and the graphite material obtained in step S2 to obtain a regenerated silicon-carbon negative electrode material.

[0014] The preparation method according to an embodiment of the present invention has at least the following beneficial effects: The present invention proposes an innovative solution that cleverly utilizes a series of chemical and physical treatment steps to efficiently recover and reuse waste silicon-carbon anode materials. This solution first mixes the waste silicon-carbon anode materials with an alkaline substance and calcines them in a non-oxidizing atmosphere. This step not only helps effectively remove impurities from the material but also partially changes its structure, laying a solid foundation for subsequent processing. During the calcination process, the silicon component is converted into silicate. Subsequently, a simple water immersion treatment can easily separate the graphite material from the silicon-containing solution. Furthermore, by adjusting the pH value of the silicon-containing solution, a silicic acid precipitate can be precipitated. The precipitation reaction is carried out under heating conditions. Increasing the temperature of the reaction system promotes hydrolysis, accelerates the reaction rate, and makes the reaction more thorough. It also accelerates the coagulation of the product from a colloidal substance to a precipitate, accelerating the aging process and facilitating subsequent filtration and separation. This silicic acid precipitate is calcined together with elemental silicon to produce silicon dioxide. The entire treatment process is easy to operate and does not require the introduction of too many complex reagents, but it successfully achieves the effective separation and reuse of silicon and carbon, significantly simplifies the recycling process, and improves economic benefits.

[0015] Another highlight of the present invention is that, through a clever combination of steps, silicon and lithium are recovered from waste materials and reintegrated into new silicon-carbon anode materials. Furthermore, the recovered graphite material is directly used for carbon coating, maximizing the recovery and utilization of the material's useful components. In particular, the recovered graphite material is reused to coat the surface of silicon dioxide particles, forming a protective layer. This protective layer not only effectively mitigates the volume expansion of silicon and prevents the cracking and pulverization of the anode material, but also significantly enhances the overall structural stability of the material, enabling it to maintain excellent performance during long-term cycling.

[0016] In summary, the present invention successfully transforms waste silicon-carbon anode materials into high-quality recycled materials through a series of carefully designed chemical and physical treatment steps. This recycled material can be directly used in the production of new batteries, reducing the difficulty and cost of recycling while achieving efficient regeneration and recycling of the material, which is of great significance for promoting the sustainable development of the battery industry.

[0017] According to some embodiments of the present invention, the alkaline substance in step S1 includes at least one of an alkali metal base or an alkali metal carbonate.

[0018] According to some embodiments of the present invention, the alkaline substance in step S1 includes at least one of sodium hydroxide, lithium hydroxide or sodium carbonate.

[0019] According to some embodiments of the present invention, in step S1, the mass ratio of the silicon-carbon negative electrode material of the waste lithium-ion battery to the alkaline substance is 5:1 to 5:6.

[0020] According to some embodiments of the present invention, the non-oxidizing atmosphere comprises at least one of carbon dioxide, nitrogen or an inert gas.

[0021] According to some embodiments of the present invention, the calcination temperature in step S1 is 300° C. to 700° C.; and / or the calcination time is 4 to 5 hours.

[0022] According to some embodiments of the present invention, the washing in step S2 is water washing.

[0023] According to some embodiments of the present invention, the water washing is performed 3 to 5 times.

[0024] According to some embodiments of the present invention, during the water washing process, the liquid-to-solid ratio of water to the calcined mixture is 4:1 to 8:1.

[0025] According to some embodiments of the present invention, in step S3, the pH is adjusted to 1.5-3.0.

[0026] According to some embodiments of the present invention, acid is used to adjust the pH in step S3.

[0027] According to some embodiments of the invention, the acid is sulfuric acid, hydrochloric acid or nitric acid solution.

[0028] According to some embodiments of the present invention, the concentration of the sulfuric acid solution is 1 mol / L to 2.5 mol / L, the concentration of the hydrochloric acid solution is 1 mol / L to 4 mol / L, and the concentration of the nitric acid solution is 1 mol / L to 2 mol / L. Hydrochloric acid and nitric acid are easily volatile under heating conditions, so sulfuric acid is preferably used.

[0029] According to some embodiments of the present invention, the heating temperature in step S3 is 70-90°C.

[0030] According to some embodiments of the present invention, in step S4, the silicic acid precipitate is mixed with silicon element in a molar ratio of 1:0.8 to 1:1.2.

[0031] According to some embodiments of the present invention, in step S4, the calcination temperature is 1200-1800°C.

[0032] According to some embodiments of the present invention, in step S4, the calcination time is 4 to 5 hours.

[0033] According to some embodiments of the present invention, in step S5, the silicon monoxide and the graphite material are mixed in a mass ratio of 10:1 to 10:1.4.

[0034] According to some embodiments of the present invention, in step S5, the carbon coating treatment includes sintering, and the sintering conditions include at least one of the following conditions:

[0035] 1) Sintering in a CVD atmosphere furnace (chemical vapor deposition atmosphere furnace);

[0036] 2) The sintering temperature is 1000-1200°C;

[0037] 3) The sintering time is 8 to 10 hours.

[0038] Carbon coating can provide better electronic conductivity while reducing the formation of SEI film, thereby improving the transmission efficiency of lithium ions. Using a CVD furnace, reaction conditions such as temperature, gas flow rate, reaction time, etc. can be precisely controlled, thereby achieving precise control of the thickness, structure and properties of the carbon coating layer.

[0039] The application of the embodiment according to the second aspect of the present invention includes the application of the above method in the preparation of lithium-ion batteries.

[0040] According to the application of the embodiment of the present invention, there are at least the following beneficial effects: the lithium-ion battery negative electrode material regeneration method of the present invention has shown broad application prospects in the field of preparation and recycling of lithium-ion batteries. This method significantly reduces costs by optimizing the regeneration process, while improving the overall economic benefits. Specifically, it can not only effectively recycle silicon, lithium, graphite, etc. in waste lithium-ion battery negative electrode materials, but also realize the efficient reuse of these materials through innovative regeneration technology, thereby significantly reducing the cost of raw materials while ensuring battery performance. In addition, the method also pays attention to environmental protection and sustainability, reduces waste emissions, conforms to the development trend of green manufacturing, and further enhances its market competitiveness and economic benefits. Therefore, the lithium-ion battery regeneration method of the present invention is not only cost-effective, but also provides strong support for the sustainable development of the lithium-ion battery industry.

[0041] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0043] Figure 1 This is an SEM image of the collected waste silicon-carbon negative electrode material before treatment in Example 1 of the present invention;

[0044] Figure 2 This is an SEM image of the regenerated silicon-carbon negative electrode material obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the concept of the present invention and the technical effects produced in conjunction with the embodiments, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. Unless otherwise specified, the test methods used in the embodiments are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials obtained from commercial channels. Unless otherwise specified, the same parameter in each embodiment has the same value. The embodiments described below are exemplary and are only used to explain the present invention, and are not to be understood as limitations of the present invention.

[0046] In the description of the present invention, reference to the term "some embodiments" or the like indicates that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0047] The silicon-carbon negative electrode materials of waste lithium-ion batteries in the following embodiments are from the same source and all parameters are consistent.

[0048] Example 1

[0049] This example provides a method for regenerating silicon-carbon negative electrode materials from waste lithium-ion batteries and its application. The specific operation of the regeneration method is as follows:

[0050] (1) Collect the waste silicon-carbon negative electrode materials (the SEM image of which is as follows) Figure 1 The mixture was uniformly mixed with flaky sodium hydroxide solid in a mass ratio of 5:5, and calcined at a high temperature in a carbon dioxide atmosphere at a calcination temperature of 600° C. for 4 h to obtain a calcined mixture.

[0051] (2) The calcined mixture was washed with deionized water at a liquid-to-solid ratio of 5:1 for multiple times until it became neutral, and then filtered to obtain graphite material for sintering to prepare lithium-ion battery negative electrode material and silicon-containing leaching solution.

[0052] (3) The pH of the silicon-containing leachate was adjusted to 1.5 with 1 mol / L sulfuric acid solution, and the reaction temperature was 80°C to completely precipitate the silicate. The silicic acid precipitate was obtained by filtration and dried.

[0053] (4) The silicic acid precipitate and silicon element are mixed uniformly in a 1:1 molar ratio, ground into micron-sized powder, and calcined under vacuum conditions at a calcination temperature of 1600°C for 4 hours. The generated gas is collected and cooled to obtain silicon dioxide solid.

[0054] (5) The silicon dioxide solid and the graphite material recovered in step (2) are subjected to carbon coating treatment, the silicon dioxide solid and the graphite material are mixed uniformly in a mass ratio of 10:1.2, ground into micron-sized powder, and sintered in a CVD atmosphere furnace at a calcination temperature of 1200°C for 10 hours. After the sintered product is naturally cooled to room temperature, it is passed through a 300-mesh sieve to obtain a recycled product SiOx@C material.

[0055] A button-type simulated cell (O2 < 0.01 ppm, H2O < 0.01 ppm) was assembled in an argon-filled glove box using a regenerated SiOx@C silicon-carbon electrode as the working electrode, metallic lithium as the negative electrode, a conductive agent, a binder, an electrolyte (1 mol / L LiPF6 dissolved in a 1:1:1 volume ratio EC:DEC:DMC solvent), and a 2500-type separator. The electrochemical performance was tested using a constant current charge-discharge method with a cutoff voltage of 0.01 to 2.00 V. The material exhibited an initial reversible capacity of 2450.4 mAh / g. After 300 cycles at a current density of 1.0 A / g, it still retained a reversible capacity of 2314.8 mAh / g, with a capacity retention rate of 94.5%.

[0056] Example 2

[0057] This example provides a method for regenerating silicon-carbon negative electrode materials from waste lithium-ion batteries and its application. The difference from Example 1 is that the type of alkaline substance is different. Specifically, the operation is as follows:

[0058] (1) The collected waste silicon-carbon negative electrode material and sodium carbonate solid were mixed evenly in a mass ratio of 5:5, and calcined at high temperature in a carbon dioxide atmosphere at a calcination temperature of 600°C and a calcination time of 4 hours to obtain a calcined mixture.

[0059] (2) The calcined mixture was washed with deionized water at a liquid-to-solid ratio of 5:1 for multiple times until it became neutral, and then filtered to obtain graphite material for sintering to prepare lithium-ion battery negative electrode material and silicon-containing leaching solution.

[0060] (3) The pH of the silicon-containing leachate was adjusted to 1.5 with 1 mol / L sulfuric acid solution, and the reaction temperature was 80°C to completely precipitate the silicate. The silicic acid precipitate was obtained by filtration and dried.

[0061] (4) The silicic acid precipitate and silicon element are mixed uniformly in a 1:1 molar ratio, ground into micron-sized powder, and calcined under vacuum conditions at a calcination temperature of 1600°C for 4 hours. The generated gas is collected and cooled to obtain silicon dioxide solid.

[0062] (5) The silicon dioxide solid and the graphite material in step b) are carbon-coated, and the silicon dioxide solid and the graphite material are evenly mixed in a mass ratio of 10:1.2, ground into micron-scale powder, and sintered in a CVD atmosphere furnace at a calcination temperature of 1200°C for 10 hours. After the sintered product is naturally cooled to room temperature, it is passed through a 300-mesh sieve to obtain a recycled product SiOx@C material.

[0063] The regenerated SiOx@C silicon-carbon electrode was used as the working electrode, metallic lithium was used as the negative electrode, and a conductive agent, a binder, an electrolyte (1 mol / L LiPF6 dissolved in a 1:1:1 EC:DEC:DMC solvent by volume), and a 2500-type diaphragm were assembled in an argon-filled glove box to form a button-type simulated battery (O2 < 0.01 ppm, H2O < 0.01 ppm). The electrochemical performance was tested using a constant current charge and discharge method with a cutoff voltage of 0.01 to 2.00 V. The material had an initial reversible capacity of 1650.9 mAh / g. After 300 cycles at a current density of 1.0 A / g, it still retained a reversible capacity of 1281.2 mAh / g, with a capacity retention rate of 77.6%.

[0064] Example 3

[0065] This example provides a method for regenerating silicon-carbon negative electrode materials from waste lithium-ion batteries and its application. The difference between this method and Example 1 is that the type and concentration of the acid solution in step (3) are different.

[0066] (1) The collected waste silicon-carbon negative electrode material and the flaky sodium hydroxide solid were mixed evenly in a mass ratio of 5:5, and calcined at a high temperature in a carbon dioxide atmosphere at a calcination temperature of 600°C and a calcination time of 4 hours to obtain a calcined mixture.

[0067] (2) The calcined mixture was washed with deionized water at a liquid-to-solid ratio of 5:1 for multiple times until it became neutral, and then filtered to obtain graphite material for sintering to prepare lithium-ion battery negative electrode material and silicon-containing leaching solution.

[0068] (3) The pH of the silicon-containing leachate was adjusted to 1.5 with a 2 mol / L hydrochloric acid solution, and the reaction temperature was 80°C to completely precipitate the silicate. The silicic acid precipitate was obtained by filtration and dried.

[0069] (4) The silicic acid precipitate and silicon element are mixed uniformly in a 1:1 molar ratio, ground into micron-sized powder, and calcined under vacuum conditions at a calcination temperature of 1600°C for 4 hours. The generated gas is collected and cooled to obtain silicon dioxide solid.

[0070] (5) The silicon dioxide solid and the graphite material in step b) are carbon-coated. The silicon dioxide solid and the graphite material are evenly mixed in a mass ratio of 10:1.2, ground into micron-sized powder, and sintered in a CVD atmosphere furnace at a calcination temperature of 1200°C for 10 hours. After the sintered product is naturally cooled to room temperature, it is passed through a 300-mesh sieve to obtain a recycled product SiOx@C material.

[0071] The regenerated SiOx@C silicon-carbon electrode was used as the working electrode, metallic lithium was used as the negative electrode, and a conductive agent, a binder, an electrolyte (1 mol / L LiPF6 dissolved in a 1:1:1 EC:DEC:DMC solvent by volume), and a 2500-type diaphragm were assembled in an argon-filled glove box to form a button-type simulated battery (O2 < 0.01 ppm, H2O < 0.01 ppm). The electrochemical performance was tested using a constant current charge and discharge method with a cutoff voltage of 0.01 to 2.00 V. The material had an initial reversible capacity of 1982.2 mAh / g. After 300 cycles at a current density of 1.0 A / g, it still retained a reversible capacity of 1591.7 mAh / g, with a capacity retention rate of 80.3%.

[0072] Example 4

[0073] This example provides a method for regenerating silicon-carbon negative electrode materials from waste lithium-ion batteries and its application. The difference from Example 1 is that in step (4), the silicic acid precipitate and silicon element are mixed in a molar ratio of 1:1.2. Other operations and parameters are the same as in Example 1.

[0074] (1) The collected waste silicon-carbon negative electrode material and the flaky sodium hydroxide solid were mixed evenly in a mass ratio of 5:5, and calcined at a high temperature in a carbon dioxide atmosphere at a calcination temperature of 600°C and a calcination time of 4 hours to obtain a calcined mixture.

[0075] (2) The calcined mixture was washed with deionized water at a liquid-to-solid ratio of 5:1 for multiple times until it became neutral, and then filtered to obtain graphite material for sintering to prepare lithium-ion battery negative electrode material and silicon-containing leaching solution.

[0076] (3) The pH of the silicon-containing leachate was adjusted to 1.5 with 1 mol / L sulfuric acid solution, and the reaction temperature was 80°C to completely precipitate the silicate. The silicic acid precipitate was obtained by filtration and dried.

[0077] (4) The silicic acid precipitate and silicon element are mixed uniformly in a 1:1 molar ratio, ground into micron-sized powder, and calcined under vacuum conditions at a calcination temperature of 1600°C for 4 hours. The generated gas is collected and cooled to obtain silicon dioxide solid.

[0078] (5) The silicon dioxide solid and the graphite material in step b) are carbon-coated. The silicon dioxide solid and the graphite material are evenly mixed in a mass ratio of 10:1.2, ground into micron-sized powder, and sintered in a CVD atmosphere furnace at a calcination temperature of 1200°C for 10 hours. After the sintered product is naturally cooled to room temperature, it is passed through a 300-mesh sieve to obtain a recycled product SiOx@C material.

[0079] The regenerated SiOx@C silicon-carbon electrode was used as the working electrode, metallic lithium was used as the negative electrode, and a conductive agent, a binder, an electrolyte (1 mol / L LiPF6 dissolved in a 1:1:1 EC:DEC:DMC solvent by volume), and a 2500-type diaphragm were assembled in an argon-filled glove box to form a button-type simulated battery (O2 <0.01ppm, H2O <0.01ppm). The electrochemical performance was tested using a constant current charge and discharge method with a cutoff voltage of 0.01 to 2.00V. The material had an initial reversible capacity of 2138.5mAh / g. After 300 cycles at a current density of 1.0A / g, it still retained a reversible capacity of 1925.3mAh / g, with a capacity retention rate of 90.03%.

[0080] Example 5

[0081] This example provides a method for regenerating silicon-carbon negative electrode materials from waste lithium-ion batteries and its application. The method differs from Example 1 only in that, in step (5), the silicon dioxide solid and the graphite material are mixed uniformly at a mass ratio of 10:1. Other operations and parameters are the same as in Example 1.

[0082] (1) The collected waste silicon-carbon negative electrode material and the flaky sodium hydroxide solid were mixed evenly in a mass ratio of 5:5, and calcined at a high temperature in a carbon dioxide atmosphere at a calcination temperature of 600°C and a calcination time of 4 hours to obtain a calcined mixture.

[0083] (2) The calcined mixture was washed with deionized water at a liquid-to-solid ratio of 5:1 for multiple times until it became neutral, and then filtered to obtain graphite material for sintering to prepare lithium-ion battery negative electrode material and silicon-containing leaching solution.

[0084] (3) The pH of the silicon-containing leachate was adjusted to 1.5 with 1 mol / L sulfuric acid solution, and the reaction temperature was 80°C to completely precipitate the silicate. The silicic acid precipitate was obtained by filtration and dried.

[0085] (4) The silicic acid precipitate and silicon element are mixed uniformly in a 1:1 molar ratio, ground into micron-sized powder, and calcined under vacuum conditions at a calcination temperature of 1000°C for 4 hours. The generated gas is collected and cooled to obtain silicon dioxide solid.

[0086] (5) The silicon dioxide solid and the graphite material in step b) are carbon-coated. The silicon dioxide solid and the graphite material are evenly mixed in a mass ratio of 10:1, ground into micron-sized powder, and sintered in a CVD atmosphere furnace at a calcination temperature of 1200°C for 10 hours. After the sintered product is naturally cooled to room temperature, it is passed through a 300-mesh sieve to obtain a recycled product SiOx@C material.

[0087] The regenerated SiOx@C silicon-carbon electrode was used as the working electrode, metallic lithium was used as the negative electrode, and a conductive agent, a binder, an electrolyte (1 mol / L LiPF6 dissolved in a 1:1:1 EC:DEC:DMC solvent by volume), and a 2500-type diaphragm were assembled in an argon-filled glove box to form a button-type simulated battery (O2 <0.01ppm, H2O <0.01ppm). The electrochemical performance was tested using a constant current charge and discharge method with a cutoff voltage of 0.01 to 2.00V. The material had an initial reversible capacity of 2075.6mAh / g. After 300 cycles at a current density of 1.0A / g, it still retained a reversible capacity of 1830.3mAh / g, with a capacity retention rate of 88.2%.

[0088] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the scope of the present invention.

Claims

1. A method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries, characterized by: The steps include: S1, mixing the waste lithium-ion battery silicon-carbon negative electrode material with an alkaline substance, and calcining the mixture in a non-oxidizing atmosphere to obtain a calcined mixture; S2, washing the calcined mixture until it is neutral, and performing solid-liquid separation to obtain a graphite material and a silicon-containing solution; S3, adjusting the pH of the silicon-containing solution to a level that causes silicate precipitation, reacting under heating, separating the solid and liquid, and collecting the silicic acid precipitate; S4, mixing the silicic acid precipitate with silicon, grinding the mixture into a micron-sized powder, calcining the mixture under vacuum conditions, and collecting the generated silicon oxide; S5. Carbon-coating the silicon monoxide and the graphite material obtained in step S2 to obtain a regenerated silicon-carbon negative electrode material.

2. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, wherein: The alkaline substance in step S1 includes at least one of an alkali metal base or an alkali metal carbonate.

3. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, wherein: The alkaline substance in step S1 includes at least one of sodium hydroxide, lithium hydroxide or sodium carbonate.

4. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, wherein: In step S1, the mass ratio of the silicon-carbon negative electrode material of the waste lithium-ion battery to the alkaline substance is 5:1 to 5:

6.

5. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, wherein: The non-oxidizing atmosphere includes at least one of carbon dioxide, nitrogen or an inert gas.

6. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, wherein: In step S1, the calcination temperature is 300° C. to 700° C.; and / or the calcination time is 4 to 5 hours.

7. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, characterized in that: In step S3, the pH is adjusted to 1.5-3.

0.

8. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, wherein: The heating temperature in step S3 is 70-90°C.

9. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, characterized in that: In the step S4, the calcination temperature is 1200-1800° C.; and / or the calcination time is 4-5 hours.

10. The method for regenerating silicon-carbon negative electrode materials of waste lithium-ion batteries according to claim 1, characterized in that: In step S5, the carbon coating treatment includes sintering, and the sintering conditions include at least one of the following conditions: 1) The silicon oxide and the graphite material are mixed in a mass ratio of 10:1 to 10:1.4; 2) Sintering in a CVD atmosphere furnace; 3) Sintering temperature is 1000~1200℃; 4) The sintering time is 8~10h.

11. Use of the method according to any one of claims 1 to 10 in preparing lithium ion batteries.

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