Method for in-situ repairing of lithium ion battery negative electrode material

Abstract

The invention discloses a method for in-situ repair of a lithium ion battery negative electrode material, and relates to the technical field of lithium ion battery negative electrode material repair, and the method specifically comprises the following steps: S1, carrying out inactivation treatment on a lithium ion battery; and S2, disassembling the lithium ion battery, and sorting out a waste graphite negative electrode material from the disassembled and crushed waste lithium battery electrode material. According to the method for in-situ remediation of the lithium ion battery negative electrode material, obtained waste graphite is purified by adopting a sulfuric acid curing-acid leaching method, so that metals and oxides in the waste graphite can be converted into corresponding soluble sulfates, and the soluble sulfates are leached by sulfuric acid and enter a solution, so that the purification of the graphite is realized; compared with a traditional direct acid leaching mode, the sulfuric acid curing acid leaching technology can promote conversion of oxides and metal elements into sulfate, so that the oxides and the metal elements are leached more efficiently and finally converted into soluble sulfate in an acid environment, the impurity removal effect is effectively improved, and meanwhile generation of solid waste is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery negative electrode material repair, and in particular to a method for in-situ repairing lithium ion battery negative electrode material. Background Art

[0002] Referring to a Chinese patent for a method for in-situ repair of waste lithium battery negative electrode materials with supercritical water (Announcement No.: CN114639889B), the existing recycling and processing technology pays little attention to the resource utilization of waste lithium battery negative electrode materials. It is difficult to remove amorphous carbon on the graphite surface, lithium salts in the microstructure and lithium-containing SEI film. The recycling and processing process is relatively complex, energy-intensive and has a series of environmental pollution problems. First, the waste negative electrode materials are sorted out from the disassembled and crushed waste lithium battery electrode materials, and then placed in a supercritical water system for in-situ repair, and the content of related elements in the supercritical water system is measured. The repair and measurement are repeated until the content of the related elements measured meets the standard value, and finally, the product is filtered and dried after flotation to obtain the product. The invention relates to a kind of negative electrode material of lithium battery, which can realize the in-situ repair and regeneration of negative electrode material, thereby reducing the recycling cost of negative electrode material and improving the battery recycling efficiency; referring to a method for plasma repairing negative electrode graphite of lithium cobalt oxide battery in China (Announcement No.: CN115636412A), the waste battery is disassembled, and the waste positive electrode powder and waste negative electrode graphite are connected with wires to form an external circuit at a temperature of 318-323°C, and recombined into a primary battery with a molten sodium hydroxide-lithium nitrate mixture as an electrolyte, so as to achieve the purpose of repairing the waste negative electrode graphite; finally, product 1 battery-grade negative electrode graphite, product 2 electrolyte and product 3 lithium salt are obtained, and the current generated by the reaction can be used back in the repair process. However, the impurities contained in the repaired graphite material are not completely removed, and a large amount of solid waste is generated. For this reason, the present invention proposes a method for in-situ repairing negative electrode material of lithium ion battery to solve the above-mentioned problems. Summary of the invention 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a method for in-situ repairing of negative electrode materials of lithium-ion batteries, which solves the problems mentioned in the above background technology.

[0003] (II) Technical solution To achieve the above objectives, the present invention is implemented by the following technical scheme: a method for in-situ repair of negative electrode materials of lithium-ion batteries, specifically comprising the following steps: S1. Inactivate the lithium-ion battery; S2, dismantling the lithium-ion battery, and separating the waste graphite negative electrode material from the dismantled and crushed waste lithium battery electrode materials; S3, washing the obtained waste graphite negative electrode material in dimethyl carbonate to remove the electrolyte on its surface, and soaking it in deionized water, ethanol and 0.5 mol / L sulfuric acid solution after drying; S4, separating the waste graphite negative electrode material from the copper current collector, filtering to obtain a graphite cake, drying and grinding, and then sieving to obtain waste graphite; S5. Purifying the obtained waste graphite by sulfuric acid aging-acid leaching method.

[0004] Preferably, the specific purification method for waste graphite in step S5 is: (1) Mix the obtained waste graphite with a certain amount of sulfuric acid, add 20% of the total mass of deionized water, and stir for 20 minutes; (2) Take out the mixture of waste graphite and sulfuric acid and ripen it in a muffle furnace; (3) taking out the calcined material after aging, leaching it in a sulfuric acid solution, and filtering it after leaching; (4) The obtained filter residue is washed with deionized water until it becomes neutral, and then placed in a calcining furnace for calcination to obtain purified graphite.

[0005] Preferably, in step S5 (1), the mass ratio of waste graphite to sulfuric acid is 1:1 to 1:1.5.

[0006] Preferably, in step S5 (2), the internal temperature of the muffle furnace is 50 to 250° C., and the aging time is 6 to 30 hours.

[0007] Preferably, the calcination time in step S5 (4) is 1 to 3 hours, and the calcination temperature is 400 to 500°C.

[0008] Preferably, the method for separating the waste graphite negative electrode material and the copper current collector in step S4 can adopt any one of ultrasonic and stirring methods.

[0009] Preferably, the sieving mesh number in S4 is 400-600 meshes.

[0010] (III) Beneficial effects The present invention provides a method for in-situ repair of negative electrode materials of lithium-ion batteries. Compared with the prior art, it has the following beneficial effects: (1) The method for in-situ repairing negative electrode materials of lithium-ion batteries, by soaking the waste graphite negative electrode materials in a mixture of deionized water, ethanol and sulfuric acid solution, can effectively reduce the degree of corrosion to lithium-ion batteries, reduce the loss of metal elements and the leakage of organic pollutants, and improve the subsequent recovery and utilization of lithium in the negative electrode materials.

[0011] (2) The method for in-situ repair of negative electrode materials for lithium-ion batteries comprises the following steps: purifying the obtained waste graphite by a sulfuric acid aging-acid leaching method, so that the metals and oxides in the waste graphite can be converted into corresponding soluble sulfates and leached into the solution through sulfuric acid, thereby achieving the purification of graphite. Compared with the traditional direct acid leaching method, the sulfuric acid aging-acid leaching technology can promote the conversion of oxides and metal elements into sulfates, making them more efficiently leached. Finally, they are converted into soluble sulfates in an acidic environment, which effectively improves the impurity removal effect and reduces the generation of solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A graph showing the relationship between the aging time and the metal element content provided for a method for in-situ repair of a negative electrode material of a lithium-ion battery of the present invention; Figure 2 A method for in-situ repair of negative electrode materials of lithium-ion batteries provided by the present invention provides a relationship diagram between aging temperature and metal element content; Figure 3 A method for in-situ repairing of negative electrode materials of lithium-ion batteries provided by the present invention provides a comparison chart of metal element contents of waste graphite after direct acid leaching and mature acid leaching. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] See also Figure 1-Figure 3 , the embodiment of the present invention provides the following three technical solutions: Embodiment 1: A method for in-situ repairing of negative electrode materials of lithium-ion batteries comprises the following steps: S1. Inactivate the lithium-ion battery. The lithium-ion battery can be inactivated by discharging, freezing with liquid nitrogen, dismantling in an inert atmosphere, etc. Completely discharging the waste lithium-ion battery before recycling can release all the stored chemical energy so that no reaction occurs inside the battery. The discharge method includes connecting an external resistor or soaking the battery in a salt electrolyte solution. S2. Disassemble the lithium-ion battery and sort out the waste graphite negative electrode material from the disassembled and crushed waste lithium battery electrode materials; lithium-ion power batteries are usually composed of many monomers, and disassembly can remove and classify the battery monomers for subsequent operations; including manual disassembly and mechanical disassembly, through disassembly, different components in the battery can also be recycled separately, such as positive electrode, negative electrode, diaphragm, metal battery shell and aluminum-plastic composite film; S3, washing the electrolyte on the surface of the obtained waste graphite negative electrode material in dimethyl carbonate, and soaking it in deionized water, ethanol and 0.5 mol / L sulfuric acid solution after drying; the mixed solution has excellent discharge performance, and can effectively reduce the corrosion degree of lithium-ion batteries, reduce the loss of metal elements and the leakage of organic pollutants, and improve the recovery and utilization of lithium in the subsequent negative electrode material; S4, separating the waste graphite negative electrode material from the copper current collector, filtering to obtain a graphite cake, drying and grinding, and then sieving to obtain waste graphite; S5. Purifying the obtained waste graphite by sulfuric acid aging-acid leaching method.

[0015] In the embodiment of the present invention, the specific purification method for waste graphite in step S5 is: (1) Mix the obtained waste graphite with a certain amount of sulfuric acid, add 20% of the total mass of deionized water, and stir for 20 minutes; (2) taking out a mixture of waste graphite and sulfuric acid and aging it in a muffle furnace; wherein the concentration of sulfuric acid is 200 g / L; (3) taking out the calcined material after aging, leaching it in a sulfuric acid solution, and filtering it after leaching; (4) The obtained filter residue is washed with deionized water until it becomes neutral, and then placed in a calcining furnace for calcination to remove the residual binder and electrolyte on the surface of the waste graphite, thereby obtaining purified graphite.

[0016] Under extremely low oxygen and sulfur dioxide partial pressures, metals and oxides in waste graphite can be converted into corresponding soluble sulfates and leached into the solution through sulfuric acid, thereby achieving graphite purification. Compared with direct acid leaching, sulfuric acid aging acid leaching technology has great advantages in impurity removal.

[0017] Through sulfuric acid aging acid leaching, concentrated sulfuric acid can destroy the inherent lattice structure of the residues (such as Nio, Co304 and MnO2) during the aging process, and then release most of the Ni, Co and Mn in the form of lattice. In particular, the Co element is reduced from a high valence state to a low valence state. In addition, metals (Cu, Fe and AI) are also oxidized from a single state to an ionic state. In other words, increasing the temperature and extending the time within a certain range can promote the conversion of oxides and metal elements to sulfates, making them more efficiently leached, and finally, converted into soluble sulfates in an acidic environment.

[0018] Among them, the calculation formula of the metal element leaching rate X in waste graphite is: 00%; Where: X is the leaching efficiency of metal impurities (%); C is the mass concentration of the measured element in the leaching solution (g / L); V is the total volume of the leaching solution (L); m is the mass of waste graphite added to the leaching solution (g); is the mass fraction (wt.%) of the element being measured.

[0019] In the embodiment of the present invention, the mass ratio of waste graphite to sulfuric acid in step S5 (1) is 1:1.

[0020] In the embodiment of the present invention, the internal temperature of the muffle furnace in step S5 (2) is 50° C., and the aging time is 6 hours.

[0021] In the embodiment of the present invention, the calcination time in step S5 (4) is 1 hour, and the calcination temperature is 400° C.

[0022] In the embodiment of the present invention, the method for separating the waste graphite negative electrode material and the copper current collector in step S4 can adopt an ultrasonic separation method.

[0023] In the embodiment of the present invention, the sieving mesh number in S4 is 400 meshes.

[0024] Embodiment 2: A method for in-situ repairing of negative electrode materials of lithium-ion batteries comprises the following steps: S1. Inactivate the lithium-ion battery. The lithium-ion battery can be inactivated by discharging, freezing with liquid nitrogen, dismantling in an inert atmosphere, etc. Completely discharging the waste lithium-ion battery before recycling can release all the stored chemical energy so that no reaction occurs inside the battery. The discharge method includes connecting an external resistor or soaking the battery in a salt electrolyte solution. S2. Disassemble the lithium-ion battery and sort out the waste graphite negative electrode material from the disassembled and crushed waste lithium battery electrode materials; lithium-ion power batteries are usually composed of many monomers, and disassembly can remove and classify the battery monomers for subsequent operations; including manual disassembly and mechanical disassembly, through disassembly, different components in the battery can also be recycled separately, such as positive electrode, negative electrode, diaphragm, metal battery shell and aluminum-plastic composite film; S3, washing the electrolyte on the surface of the obtained waste graphite negative electrode material in dimethyl carbonate, and soaking it in deionized water, ethanol and 0.5 mol / L sulfuric acid solution after drying; the mixed solution has excellent discharge performance, and can effectively reduce the corrosion degree of lithium-ion batteries, reduce the loss of metal elements and the leakage of organic pollutants, and improve the recovery and utilization of lithium in the subsequent negative electrode material; S4, separating the waste graphite negative electrode material from the copper current collector, filtering to obtain a graphite cake, drying and grinding, and then sieving to obtain waste graphite; S5. Purifying the obtained waste graphite by sulfuric acid aging-acid leaching method.

[0025] In the embodiment of the present invention, the specific purification method for waste graphite in step S5 is: (1) Mix the obtained waste graphite with a certain amount of sulfuric acid, add 20% of the total mass of deionized water, and stir for 20 minutes; (2) taking out a mixture of waste graphite and sulfuric acid and aging it in a muffle furnace; wherein the concentration of sulfuric acid is 200 g / L; (3) taking out the calcined material after aging, leaching it in a sulfuric acid solution, and filtering it after leaching; (4) The obtained filter residue is washed with deionized water until it becomes neutral, and then placed in a calcining furnace for calcination to remove the residual binder and electrolyte on the surface of the waste graphite, thereby obtaining purified graphite.

[0026] Under extremely low oxygen and sulfur dioxide partial pressures, metals and oxides in waste graphite can be converted into corresponding soluble sulfates and leached into the solution through sulfuric acid, thereby achieving graphite purification. Compared with direct acid leaching, sulfuric acid aging acid leaching technology has great advantages in impurity removal.

[0027] Through sulfuric acid aging acid leaching, concentrated sulfuric acid can destroy the inherent lattice structure of the residues (such as Nio, Co304 and MnO2) during the aging process, and then release most of the Ni, Co and Mn in the form of lattice. In particular, the Co element is reduced from a high valence state to a low valence state. In addition, metals (Cu, Fe and AI) are also oxidized from a single state to an ionic state. In other words, increasing the temperature and extending the time within a certain range can promote the conversion of oxides and metal elements to sulfates, making them more efficiently leached, and finally, converted into soluble sulfates in an acidic environment.

[0028] Among them, the calculation formula of the metal element leaching rate X in waste graphite is: 00%; Where: X is the leaching efficiency of metal impurities (%); C is the mass concentration of the measured element in the leaching solution (g / L); V is the total volume of the leaching solution (L); m is the mass of waste graphite added to the leaching solution (g); is the mass fraction (wt.%) of the element being measured.

[0029] In the embodiment of the present invention, the mass ratio of waste graphite to sulfuric acid in step S5 (1) is 1:1.25.

[0030] In the embodiment of the present invention, the internal temperature of the muffle furnace in step S5 (2) is 150° C. and the aging time is 18 h.

[0031] In the embodiment of the present invention, the calcination time in step S5 (4) is 2 hours, and the calcination temperature is 450° C.

[0032] In the embodiment of the present invention, the method for separating the waste graphite negative electrode material and the copper current collector in step S4 can adopt a stirring separation method.

[0033] In the embodiment of the present invention, the sieving mesh number in S4 is 500 meshes.

[0034] Embodiment 3: A method for in-situ repairing of negative electrode materials of lithium-ion batteries comprises the following steps: S1. Inactivate the lithium-ion battery. The lithium-ion battery can be inactivated by discharging, freezing with liquid nitrogen, dismantling in an inert atmosphere, etc. Completely discharging the waste lithium-ion battery before recycling can release all the stored chemical energy so that no reaction occurs inside the battery. The discharge method includes connecting an external resistor or soaking the battery in a salt electrolyte solution. S2. Disassemble the lithium-ion battery and sort out the waste graphite negative electrode material from the disassembled and crushed waste lithium battery electrode materials; lithium-ion power batteries are usually composed of many monomers, and disassembly can remove and classify the battery monomers for subsequent operations; including manual disassembly and mechanical disassembly, through disassembly, different components in the battery can also be recycled separately, such as positive electrode, negative electrode, diaphragm, metal battery shell and aluminum-plastic composite film; S3, washing the electrolyte on the surface of the obtained waste graphite negative electrode material in dimethyl carbonate, and soaking it in deionized water, ethanol and 0.5 mol / L sulfuric acid solution after drying; the mixed solution has excellent discharge performance, and can effectively reduce the corrosion degree of lithium-ion batteries, reduce the loss of metal elements and the leakage of organic pollutants, and improve the recovery and utilization of lithium in the subsequent negative electrode material; S4, separating the waste graphite negative electrode material from the copper current collector, filtering to obtain a graphite cake, drying and grinding, and then sieving to obtain waste graphite; S5. Purifying the obtained waste graphite by sulfuric acid aging-acid leaching method.

[0035] In the embodiment of the present invention, the specific purification method for waste graphite in step S5 is: (1) Mix the obtained waste graphite with a certain amount of sulfuric acid, add 20% of the total mass of deionized water, and stir for 20 minutes; (2) taking out a mixture of waste graphite and sulfuric acid and aging it in a muffle furnace; wherein the concentration of sulfuric acid is 200 g / L; (3) taking out the calcined material after aging, leaching it in a sulfuric acid solution, and filtering it after leaching; (4) The obtained filter residue is washed with deionized water until it becomes neutral, and then placed in a calcining furnace for calcination to remove the residual binder and electrolyte on the surface of the waste graphite, thereby obtaining purified graphite.

[0036] Under extremely low oxygen and sulfur dioxide partial pressures, metals and oxides in waste graphite can be converted into corresponding soluble sulfates and leached into the solution through sulfuric acid, thereby achieving graphite purification. Compared with direct acid leaching, sulfuric acid aging acid leaching technology has great advantages in impurity removal.

[0037] Through sulfuric acid aging acid leaching, concentrated sulfuric acid can destroy the inherent lattice structure of the residues (such as Nio, Co304 and MnO2) during the aging process, and then release most of the Ni, Co and Mn in the form of lattice. In particular, the Co element is reduced from a high valence state to a low valence state. In addition, metals (Cu, Fe and AI) are also oxidized from a single state to an ionic state. In other words, increasing the temperature and extending the time within a certain range can promote the conversion of oxides and metal elements to sulfates, making them more efficiently leached, and finally, converted into soluble sulfates in an acidic environment.

[0038] Among them, the calculation formula of the metal element leaching rate X in waste graphite is: 00%; Where: X is the leaching efficiency of metal impurities (%); C is the mass concentration of the measured element in the leaching solution (g / L); V is the total volume of the leaching solution (L); m is the mass of waste graphite added to the leaching solution (g); is the mass fraction (wt.%) of the element being measured.

[0039] In the embodiment of the present invention, the mass ratio of waste graphite to sulfuric acid in step S5 (1) is 1:1.5.

[0040] In the embodiment of the present invention, the internal temperature of the muffle furnace in step S5 (2) is 200°C, the aging time is 30h, and Figure 1 and Figure 2 It can be seen that the leaching amount of metal elements is the largest at this time, which reduces the content of metal elements in the waste graphite.

[0041] In the embodiment of the present invention, the calcination time in step S5 (4) is 3 hours and the calcination temperature is 500° C.

[0042] In the embodiment of the present invention, the method for separating the waste graphite negative electrode material and the copper current collector in step S4 can adopt an ultrasonic separation method.

[0043] In the embodiment of the present invention, the sieving mesh number in S4 is 600 meshes.

[0044] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0045] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0046] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for in-situ repair of negative electrode materials of lithium-ion batteries, characterized in that: The specific steps include: S1. Inactivate the lithium-ion battery; S2, dismantling the lithium-ion battery, and separating the waste graphite negative electrode material from the dismantled and crushed waste lithium battery electrode materials; S3, washing the obtained waste graphite negative electrode material in dimethyl carbonate to remove the electrolyte on its surface, and soaking it in deionized water, ethanol and 0.5 mol / L sulfuric acid solution after drying; S4, separating the waste graphite negative electrode material from the copper current collector, filtering to obtain a graphite cake, drying and grinding, and then sieving to obtain waste graphite; S5. Purifying the obtained waste graphite by sulfuric acid aging-acid leaching method.

2. The method for in-situ repair of negative electrode materials of lithium-ion batteries according to claim 1, characterized in that: The specific purification method for waste graphite in step S5 is: (1) Mix the obtained waste graphite with a certain amount of sulfuric acid, add 20% of the total mass of deionized water, and stir for 20 minutes; (2) Take out the mixture of waste graphite and sulfuric acid and ripen it in a muffle furnace; (3) taking out the calcined material after aging, leaching it in a sulfuric acid solution, and filtering it after leaching; (4) The obtained filter residue is washed with deionized water until it becomes neutral, and then placed in a calcining furnace for calcination to obtain purified graphite.

3. The method for in-situ repairing of negative electrode materials of lithium-ion batteries according to claim 2, characterized in that: In step S5 (1), the mass ratio of waste graphite to sulfuric acid is 1:1 to 1:1.

5.

4. The method for in-situ repair of negative electrode materials of lithium-ion batteries according to claim 2, characterized in that: In step S5 (2), the internal temperature of the muffle furnace is 50 to 250° C., and the aging time is 6 to 30 hours.

5. The method for in-situ repair of negative electrode materials of lithium-ion batteries according to claim 2, characterized in that: The calcination time in step S5 (4) is 1 to 3 hours, and the calcination temperature is 400 to 500°C.

6. The method for in-situ repair of negative electrode materials of lithium-ion batteries according to claim 1, characterized in that: The method for separating the waste graphite negative electrode material and the copper current collector in step S4 can be any one of ultrasonic and stirring methods.

7. The method for in-situ repair of negative electrode materials of lithium-ion batteries according to claim 1, characterized in that: The sieving mesh number in S4 is 400 to 600 meshes.

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