A method for manufacturing a secondary battery and a secondary battery

Abstract

The application discloses a preparation method of a regenerated battery and the regenerated battery, and relates to the technical field of battery recycling and regeneration; and comprises the following steps: obtaining lithium iron phosphate waste and graphite waste based on retired lithium iron phosphate batteries; mixing the lithium iron phosphate waste, lithium carbonate lithium supplement and residual lithium precipitate, adding a composite filling agent and a titanium-lanthanum combined effect modifier for heat treatment to obtain a regenerated lithium iron phosphate material; performing acid pickling, drying and sorting on the graphite waste to obtain graphite powder; obtaining a suspension by mixing the graphite powder, a silane coupling agent and a carboxylated graphene combined agent and a solvent, and performing heat treatment on the suspension to obtain a regenerated graphite material; and preparing a positive electrode sheet and a negative electrode sheet based on the regenerated lithium iron phosphate material and the regenerated graphite material, and assembling the positive electrode sheet, the negative electrode sheet, an electrolyte and a diaphragm into the regenerated battery. The application optimizes the regeneration process of the lithium iron phosphate waste and the graphite waste, so that the electrochemical performance of the regenerated battery is improved.

Description

Technical Field

[0001] This application relates to the technical field of battery recycling and regeneration, specifically to a method for preparing a regenerated battery and the regenerated battery itself. Background Technology

[0002] The lithium, iron, and phosphorus components of the positive electrode and the graphite material of the negative electrode in retired lithium iron phosphate batteries all have extremely high recycling value. While some existing technologies offer recycling solutions for individual recycled materials, they lack designs for the coordinated regeneration and optimization of both positive and negative electrode materials. This fails to fully utilize the resource synergy during the recycling process, and it is difficult to balance process cost and environmental friendliness. Summary of the Invention

[0003] The first aspect of this application provides a method for preparing a regenerated battery, the method comprising the following steps:

[0004] Retired lithium iron phosphate batteries are pretreated to obtain lithium iron phosphate waste and graphite waste.

[0005] A premix is ​​obtained by mixing lithium iron phosphate waste, lithium carbonate lithium supplementer and residual lithium precipitate. A composite filler and titanium-lanthanum combined modifier are added to the premix to obtain a mixture. The mixture is then heat-treated to obtain recycled lithium iron phosphate material.

[0006] The graphite waste is sequentially acid-washed, dried and sorted to obtain graphite powder. A silane coupling agent, a carboxylated graphene coupling agent and a solvent are added to the graphite powder to obtain a suspension. The suspension is then heat-treated to obtain recycled graphite material.

[0007] Positive and negative electrode sheets are prepared based on recycled lithium iron phosphate materials and recycled graphite materials, and the positive electrode sheet, negative electrode sheet, electrolyte and separator are assembled into a recycled battery.

[0008] In some optional embodiments of the first aspect of this application, based on the mass of the premix, the mass fraction of the lithium carbonate supplement is 4% to 6%, and the mass fraction of the residual lithium precipitate is 1.2% to 1.5%.

[0009] The particle size D50 of lithium iron phosphate waste is 3μm~5μm.

[0010] In some optional embodiments of the first aspect of this application, the residual lithium precipitate includes lithium carbonate, and the mass fraction of lithium carbonate in the residual lithium precipitate is not less than 90% based on the mass of the residual lithium precipitate;

[0011] The process of obtaining residual lithium precipitate involves: water leaching of graphite waste, filtration to obtain lithium-containing leachate, evaporation and concentration of the lithium-containing leachate at 80℃~90℃, followed by cooling and crystallization to obtain residual lithium precipitate.

[0012] In some optional embodiments of the first aspect of this application, the amount of composite filler added is 3% to 4% of the mass of the premix, and the amount of titanium-lanthanum synergistic modifier added is 1.5% to 2.5% of the mass of the premix;

[0013] The composite filler consists of cerium-doped carbon nanotubes and modified zinc oxide whiskers, with a mass ratio of cerium-doped carbon nanotubes to modified zinc oxide whiskers of (1.2~1.5):1.

[0014] In some optional embodiments of the first aspect of this application, heat treatment of the mixture includes:

[0015] The mixture was pre-calcined at 320℃~380℃ for 2h~4h in an inert gas atmosphere, and then heated to 760℃~780℃ for 8.5h~9.5h.

[0016] Before heat treatment of the mixture, the preparation method further includes: ball milling the mixture at a ball milling speed of 350 r / min to 450 r / min for a ball milling time of 2.5 h to 3.5 h.

[0017] In some optional embodiments of the first aspect of this application, adding a silane coupling agent, a carboxylated graphene coupling agent, and a solvent to graphite powder to obtain a suspension includes:

[0018] Graphite powder, silane coupling agent and carboxylated graphene co-activator are mixed to obtain graphite mixture, solvent is added to graphite mixture and ultrasonic dispersion is performed to prepare suspension;

[0019] Based on the mass of the graphite mixture, the mass fraction of the silane coupling agent is 0.6%~0.8%, and the mass fraction of the carboxylated graphene coupling agent is 0.6%~0.8%.

[0020] The solvent is a mixture of water and anhydrous ethanol, and the solid content of the suspension is 10%~15%.

[0021] The ultrasonic dispersion time is 35 min to 45 min;

[0022] The particle size D50 of the graphite powder is 10μm~12μm, and the purity of the graphite powder is not less than 99.5%.

[0023] In some optional embodiments of the first aspect of this application, heat treatment of the suspension includes:

[0024] The suspension was dried at 100℃~130℃ for 2h~3h, and then heat-treated at 180℃~220℃ for 2h~4h under an inert gas atmosphere.

[0025] In some optional embodiments of the first aspect of this application, the sequential acid washing, drying, and sorting of graphite waste includes:

[0026] Add graphite waste to the mixed acid solution and stir for 40-50 minutes at a stirring rate of 80-100 r / min. Then filter to obtain filter cake. Wash the filter cake multiple times until the pH of the washing solution is 6.5-7.0.

[0027] The filter cake is dried at 110℃~115℃ for 6.5h~7.5h, and then impurity particles with a particle size <1μm are removed by airflow separation; wherein the separation velocity of airflow separation is 10m / s~12m / s.

[0028] The mixed acid solution includes hydrochloric acid and nitric acid. Based on the mass of the mixed acid solution, the mass fraction of hydrochloric acid is 10%~15%, and the mass fraction of nitric acid is 10%~30%.

[0029] The liquid-solid ratio of the mixed acid solution to the graphite waste is (5~10):1 mL / g.

[0030] In some optional embodiments of the first aspect of this application, the Li / Fe molar ratio of the recycled lithium iron phosphate material is 1.02~1.03, the crystallinity is ≥97%, and the specific surface area is 12m². 2 / g~18m 2 / g;

[0031] The tap density of the recycled graphite material is 1.1 g / cm³. 3 ~1.6g / cm 3 .

[0032] The second aspect of this application provides a regenerable battery prepared by the above-described method for preparing a regenerable battery.

[0033] Beneficial effects:

[0034] In the first aspect of this application, in the regeneration of lithium iron phosphate waste, residual lithium in recycled graphite waste is used as an auxiliary lithium source, combined with precise lithium replenishment of lithium carbonate, to restore the Li / Fe molar ratio to 1.02~1.03; a composite filler fills lattice defects, a titanium-lanthanum combined modifier improves electronic conductivity and structural stability, and staged calcination precisely controls the heating rate and holding time to restore the structural integrity of olivine (crystallinity ≥97%), thereby improving the regeneration effect of lithium iron phosphate waste.

[0035] The first aspect of this application is to optimize the acid washing process in the recycling of graphite waste, which can efficiently remove impurities such as copper and iron at room temperature, and improve the graphite purity to over 99.5%. By using carboxylated graphene and silane coupling agent for synergistic modification, not only is the surface activity of graphite improved, but a continuous conductive network can also be constructed, reducing the interfacial impedance by more than 30%, thus solving the problems of insufficient purity and poor interfacial compatibility of recycled graphite.

[0036] In the recycling method of the first aspect of this application, the positive and negative electrode materials of retired lithium iron phosphate batteries are selectively recycled and regenerated. The synergistic regeneration and precise matching of the positive and negative electrode recycled materials significantly reduce the energy consumption and carbon emissions of the recycling process, achieving efficient and low-carbon battery recycling. At the same time, the combined process of residual lithium recovery and selective lithium replenishment reduces lithium source consumption by 20%, and composite modification and surface modification technologies simultaneously improve the conductivity and interface compatibility of the materials, optimizing the specific surface area of ​​the recycled lithium iron phosphate material to 12m². 2 / g~18m 2 / g, the tap density of recycled graphite material is 1.1g / cm³. 3 ~1.6g / cm 3 .

[0037] The regenerated battery obtained in the second aspect of this application has good electrochemical performance. The initial discharge capacity of the regenerated battery at 0.5C is ≥142mAh / g, the capacity retention rate after 100 cycles is ≥97.5%, and the capacity retention rate after 500 cycles is ≥90%. The discharge capacity at 2C rate is ≥128mAh / g, showing excellent rate performance. The capacity retention rate at -20℃ is ≥88%, and the capacity retention rate after 50 cycles at 60℃ is ≥95%, showing strong wide temperature adaptability. Attached Figure Description

[0038] Figure 1 This is a flowchart of a method for preparing a regenerated battery in one embodiment of this application;

[0039] Figure 2 This is a flowchart of a method for preparing recycled lithium iron phosphate material in one embodiment of this application;

[0040] Figure 3 This is a flowchart of a method for preparing recycled graphite material in one embodiment of this application;

[0041] Figure 4 This is a flowchart of a method for preparing residual lithium precipitate in one embodiment of this application. Detailed Implementation

[0042] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present application and are not intended to limit the present application.

[0043] In one embodiment, such as Figure 1 As shown, a method for preparing a regenerable battery is provided, comprising the following steps:

[0044] Retired lithium iron phosphate batteries are pretreated to obtain lithium iron phosphate waste and graphite waste.

[0045] A premix is ​​obtained by mixing lithium iron phosphate waste, lithium carbonate lithium supplementer and residual lithium precipitate. A composite filler and titanium-lanthanum combined modifier are added to the premix to obtain a mixture. The mixture is then heat-treated to obtain recycled lithium iron phosphate material.

[0046] The graphite waste is sequentially acid-washed, dried and sorted to obtain graphite powder. A silane coupling agent, a carboxylated graphene coupling agent and a solvent are added to the graphite powder to obtain a suspension. The suspension is then heat-treated to obtain recycled graphite material.

[0047] Positive and negative electrode sheets are prepared based on recycled lithium iron phosphate materials and recycled graphite materials, and the positive electrode sheet, negative electrode sheet, electrolyte and separator are assembled into a recycled battery.

[0048] In this embodiment, the lithium iron phosphate waste and graphite waste are derived from retired lithium iron phosphate batteries, which may originate from the same retired lithium iron phosphate battery or from different retired lithium iron phosphate batteries. The retired lithium iron phosphate batteries are recycled through pretreatment processes such as deep discharge, mechanical stripping and crushing, pyrolysis, and sorting to obtain lithium iron phosphate waste and graphite waste. The recycled lithium iron phosphate waste has a low Li / Fe molar ratio and low crystallinity, while the graphite waste has low graphite purity and a high content of impurities such as aluminum and other metal impurities.

[0049] In this embodiment, lithium iron phosphate waste and graphite waste are regenerated to obtain regenerated lithium iron phosphate material and regenerated graphite material. Positive electrode sheet and negative electrode sheet are prepared using the regenerated lithium iron phosphate material and regenerated graphite material as raw materials. The positive electrode sheet, negative electrode sheet, electrolyte and separator are assembled into a regenerated battery. The regenerated battery has good electrochemical performance.

[0050] In the regeneration treatment of lithium iron phosphate waste in this embodiment, such as Figure 2 As shown, lithium iron phosphate waste, lithium carbonate replenishing agent, and residual lithium precipitate are first mixed to obtain a premix. Then, a composite filler and a titanium-lanthanum synergistic modifier are added to the premix to obtain a mixture. The mixture is then heat-treated. During the heat treatment, the lithium carbonate replenishing agent, residual lithium precipitate, composite filler, and titanium-lanthanum synergistic modifier play their roles, resulting in a high-performance recycled lithium iron phosphate material.

[0051] In the recycling process of graphite waste in this embodiment, such as Figure 3 As shown, graphite waste is first acid-washed, dried and sorted to obtain graphite powder with high purity and few impurities. Then, silane coupling agent, carboxylated graphene coupling agent and solvent are added to the graphite powder to form a suspension. The suspension is then heat-treated to obtain recycled graphite material with good performance.

[0052] The synergistic modification of graphite powder, silane coupling agent, and carboxyl-based graphene co-modifier achieves a strong bond between graphite powder and carboxyl-based graphene through the combined effect of "silane coupling agent bridging + chemical bonding + physical coating," ultimately improving the performance of the graphite anode. The principle is as follows:

[0053] (I) Silane coupling agents (such as silane coupling agents KH570, KH550, KH560, KH792, and DL171) undergo hydrolysis in suspension. The alkoxy group (-OR, such as methoxy or ethoxy) of the silane coupling agent reacts with water molecules to generate hydrolysis products containing active hydroxyl groups (-OH), while simultaneously releasing alcohols such as methanol and ethanol. Taking silane coupling agent KH570 (γ-methacryloyloxypropyltrimethoxysilane) as an example, the hydrolysis reaction formula is simplified as follows:

[0054] CH2=C(CH3)COO(CH2)3Si(OCH3)3+3H2O→CH2=C(CH3)COO(CH2)3Si(OH)3+3CH3OH.

[0055] The hydrolyzed silane coupling agent has an inorganic-loving hydroxyl group (-Si-OH) at one end and an organic-loving double bond functional group (such as the acrylic acid double bond of KH570) at the other end, which becomes a "bridge" connecting graphite powder and carboxylated graphene.

[0056] (II) Although the surface of graphite powder is relatively inert, after acid washing, a small number of hydroxyl (-OH) and carboxyl (-COOH) groups are attached to the surface of the graphite powder due to oxidation, providing active sites for the reaction. After hydrolysis, the inorganic-loving hydroxyl (-Si-OH) of the silane coupling agent undergoes a dehydration condensation reaction with the hydroxyl (-OH) on the surface of the graphite powder to form a stable Si-OC covalent bond, "anchoring" the silane coupling agent to the surface of the graphite powder, while releasing water molecules. The reaction formula is simplified as follows:

[0057] Graphite surface -OH+HO-Si-(CH2)3-OOC(CH3)=CH2→Graphite surface -O-Si-(CH2)3-OOC(CH3)=CH2+H2O.

[0058] This reaction allows a large number of organic double-bonded functional groups to be grafted onto the surface of inert graphite, providing active sites for subsequent binding with carboxylated graphene.

[0059] (III) The surface of carboxyl graphene is rich in carboxyl groups (-COOH), hydroxyl groups (-OH), and a small amount of epoxy groups (-O-). These react with the silane coupling agent grafted onto the surface of the graphite powder through double bond addition and hydroxyl dehydration condensation reactions, achieving a strong bond between the graphite powder, the silane coupling agent, and the carboxyl graphene.

[0060] Double bond addition reactions include the acrylic double bond (CH2=C(CH3)-) of silane coupling agents (such as KH570) reacting with the unsaturated carbon bonds generated by oxidation at the edge of carboxylated graphene, which undergoes a free radical addition reaction under heating to form C-C covalent bonds, allowing graphene to partially coat the graphite surface;

[0061] Hydroxyl dehydration condensation reaction: The hydroxyl groups (-OH) on the surface of carboxylated graphene undergo dehydration condensation again with the residual hydroxyl groups (-Si-OH) that have not fully reacted with the silane coupling agent, forming additional Si-OC bonds, which further strengthens the interfacial bonding force and inhibits the aggregation of carboxylated graphene sheets.

[0062] The above-mentioned double bond addition reaction and hydroxyl dehydration condensation reaction work together to avoid the stacking of carboxylated graphene and to form a composite structure between carboxylated graphene and graphite powder.

[0063] It should be noted that the carboxylated graphene in this embodiment is commercially available. For example, if G8 carboxylated graphene is used, the equivalent particle size is about 0.5μm~5μm and the carboxyl content is 4.0wt%.

[0064] In some optional embodiments of this application, the mass fraction of lithium carbonate supplement is 4% to 6% based on the mass of the premix, and the mass fraction of residual lithium precipitate is 1.2% to 1.5%.

[0065] In some optional embodiments of this application, the particle size D50 of the lithium iron phosphate waste is 3μm to 5μm.

[0066] In some optional embodiments of this application, the residual lithium precipitate includes lithium carbonate, and the mass fraction of lithium carbonate in the residual lithium precipitate is not less than 90% based on the mass of the residual lithium precipitate.

[0067] In some optional embodiments of this application, such as Figure 4 As shown, the process of obtaining residual lithium precipitate includes: water leaching of graphite waste, filtration to obtain lithium-containing leachate, evaporation and concentration of lithium-containing leachate at 80℃~90℃, followed by cooling and crystallization to obtain residual lithium precipitate.

[0068] The residual lithium precipitate used in this embodiment originates from the graphite waste recycling process. Its main component is lithium carbonate, with small amounts of LiOH, LiF, and trace amounts of Fe and Al impurities. The residual lithium precipitate exhibits significant advantages in regenerated battery material systems: firstly, its raw material comes from recycling byproducts, significantly reducing the cost of lithium replenishment raw materials; secondly, its compositional characteristics are highly compatible with the regeneration system, ensuring effective lithium replenishment while avoiding performance fluctuations caused by uneven lithium distribution. More importantly, directly utilizing the residual lithium precipitate achieves a closed-loop resource recovery path of "treating waste with waste," significantly reducing the energy consumption and environmental pressure brought about by high-purity lithium salt production.

[0069] It should be noted that the water leaching treatment in this embodiment includes: mixing graphite waste with water and stirring for 20 minutes, and filtering to obtain a lithium-containing leachate, wherein the liquid-solid ratio of water to graphite waste is 8:1 mL / g.

[0070] In some optional embodiments of this application, the amount of composite filler added is 3% to 4% of the mass of the premix, and the amount of titanium-lanthanum synergistic modifier added is 1.5% to 2.5% of the mass of the premix; the composite filler includes cerium-doped carbon nanotubes and modified zinc oxide whiskers, and the mass ratio of cerium-doped carbon nanotubes to modified zinc oxide whiskers is (1.2 to 1.5): 1.

[0071] In this embodiment, the composite filler includes cerium-doped carbon nanotubes and modified zinc oxide whiskers. During the heat treatment stage (pre-calcination + roasting), the one-dimensional conductive network of the cerium-doped carbon nanotubes and the needle-like rigid structure of the modified zinc oxide whiskers fill the lattice defects and pores of the recycled lithium iron phosphate material, inhibiting the volume expansion and particle agglomeration of the recycled lithium iron phosphate material during charging and discharging. The zinc oxide whiskers release some lithium ions through interfacial reactions, replenishing the lithium content lost by the recycled lithium iron phosphate material during the cycling / recycling process, indirectly improving the actual discharge capacity of the cathode. Cerium doping optimizes the electronic conductivity of the material, reduces lithium ion migration resistance, and further enhances the capacity performance after lithium replenishment. The modified zinc oxide whiskers and the surface active groups of the cerium-doped carbon nanotubes adsorb impurities (such as HF) in the electrolyte, reducing side reactions between the cathode and the electrolyte, reducing irreversible growth of the SEI film, and improving the cycle life of the battery after lithium replenishment.

[0072] In this embodiment, the titanium-lanthanum synergistic modifier includes lanthanum titanate. Lanthanum titanate itself contains stable lithium-ion storage sites. During the first charge of the battery, it can directionally release lithium ions to directly fill the lithium vacancies in the regenerated lithium iron phosphate, achieving "targeted lithium replenishment" and significantly improving the first discharge specific capacity and charge / discharge efficiency. The radius of lanthanum ions is close to that of iron ions, allowing them to be doped into the lithium iron phosphate lattice and suppress lattice distortion. Titanium ions can form stable Ti-O bonds with oxygen in the lattice, enhancing the integrity of the lattice structure and reducing lattice collapse during the lithium-ion insertion / extraction process after lithium replenishment. The crystal structure of lanthanum titanate has open lithium-ion channels, and the introduction of lanthanum can reduce the charge transfer impedance of the material, accelerate the migration rate of lithium ions inside the positive electrode and at the electrode-electrolyte interface, and improve the rate performance of the battery after lithium replenishment.

[0073] The lattice doping reaction between the titanium-lanthanum synergistic modifier and lithium iron phosphate materials is as follows: During heat treatment (e.g., 350℃~780℃), lanthanum titanate decomposes to produce La. 3+ Ti 4+ , part of La 3+ Ti 4+ It replaces the iron ion sites in the lithium iron phosphate (LiFePO4) lattice to form a Li(Fe,La,Ti)PO4 solid solution.

[0074] Modified zinc oxide whiskers are grafted with silane coupling agents (such as KH570). The hydroxyl groups (-OH) generated by the hydrolysis of the silane coupling agent (such as KH570) undergo dehydration condensation reactions with the hydroxyl groups on the surface of regenerated lithium iron phosphate and the active groups remaining after titanium-lanthanum modification, forming Si-OP bonds or Si-O-Ti bonds (mainly occurring during the calcination process), reducing interfacial peeling.

[0075] In this embodiment, during the first charge, lithium ions released from lanthanum titanate are inserted into the lattice vacancies of lithium iron phosphate. At the same time, cerium-doped carbon nanotubes in the filler can adsorb fluoride ions in the electrolyte, inhibit the reaction between HF and lithium iron phosphate, reduce irreversible loss of lithium ions, and simultaneously repair the damaged electrode interface.

[0076] In this embodiment, the amount of composite filler added is 3% to 4% of the mass of the premix. By controlling the amount of composite filler within the above range, the appropriate ratio of composite filler provides a sufficient and efficient lithium replenishment carrier, fully repairs lithium vacancies in regenerated lithium iron phosphate, and significantly improves the capacity recovery rate. The appropriate amount of cerium-doped carbon nanotubes and modified zinc oxide whiskers effectively construct a conductive network and enhance the electrode structure without occupying too many positive electrode active sites, thereby maintaining a high unit mass capacity density. At the same time, the composite filler is uniformly distributed and does not accumulate excessively, which helps to form an ordered and interconnected pore structure and promotes rapid lithium ion migration.

[0077] In this embodiment, the amount of titanium-lanthanum synergistic modifier added is 1.5% to 2.5% of the premix mass. By controlling the amount of titanium-lanthanum synergistic modifier within the above range, the appropriate amount of titanium-lanthanum synergistic modifier can effectively utilize the properties of La. 3+ Ti 4+ It stabilizes the lithium iron phosphate lattice, improves lithium-ion insertion / extraction efficiency, and avoids increased internal resistance due to poor conductivity.

[0078] It should be noted that the cerium-doped carbon nanotubes in this embodiment are prepared by a hydrothermal method. The specific preparation steps are as follows: First, pretreat the carbon nanotubes by adding multi-walled carbon nanotubes and concentrated nitric acid to a three-necked flask and reacting at 140°C for 6-12 hours. After the reaction, allow the mixture to stand and filter, wash, and then vacuum dry at 55°C for 24 hours to complete the acidification and purification. Second, prepare the cerium-doped composite material by adding the treated carbon nanotubes to deionized water and ultrasonically dispersing for 2 hours, then adding cerium nitrate hexahydrate, and slowly adding concentrated ammonia to adjust the pH to 10-11. Finally, transfer the mixture to a reaction vessel and react at 180°C for 24 hours. After cooling, filter, wash, and dry to obtain the cerium-doped carbon nanotubes.

[0079] In this embodiment, the modified zinc oxide whiskers are modified with a silane coupling agent, and the preparation steps are as follows: First, aminopropyltrimethoxysilane coupling agent is added to a 1:1 volume ratio water-acetone solution, the pH is adjusted to 3-5, and after hydrolysis, zinc oxide whiskers are added. The mixture is stirred at 60℃-80℃ for 1-2 hours, filtered and dried to obtain amino-modified whiskers. Then, it is added to N,N-dimethylformamide along with 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and triethylamine. The mixture is reacted at 55℃-75℃ for 20-30 hours under a nitrogen atmosphere. After post-treatment, modified zinc oxide whiskers are obtained.

[0080] In this embodiment, the titanium-lanthanum synergistic modifier uses lanthanum titanate as the core product and is prepared by the sol-gel method. The specific preparation is as follows: First, lanthanum hydroxide and tetrabutyl titanate are weighed at a 1:1 molar ratio, dissolved in triethylene glycol, and heated to 60°C. The mixture is stirred for 30 minutes to obtain a mixed suspension. Second, while maintaining the temperature, ammonia water equivalent to 5 times the weight of lanthanum hydroxide is added, and the mixture is stirred continuously at 160°C and 300 r / min for 4 hours to form a lanthanum titanate sol. Third, electrode powder is added, stirred, and allowed to stand. After precipitation and washing, the powder is dried at 160°C for 2 hours, then mixed with sodium borohydride at a 1:1 molar ratio. The mixture is then held at 350°C in a tube furnace for 1 hour, and after cooling, the titanium-lanthanum synergistic modifier is obtained. Alternatively, the process can be simplified by dissolving lanthanum nitrate, titanium acetylacetonate, and citric acid in water, stirring, heating, cross-linking, grinding, and then placing the mixture in a resistance furnace at a rate of 5~20°C / min to 600°C~800°C for calcination for 4~24 hours to directly obtain lanthanum titanate synergistic modified powder.

[0081] In some optional embodiments of this application, heat treatment of the mixture includes:

[0082] The mixture was pre-calcined at 320℃~380℃ for 2h~4h in an inert gas atmosphere, and then heated to 760℃~780℃ for 8.5h~9.5h.

[0083] In this embodiment, the pre-calcination process removes residual moisture and organic matter from the mixture, creating space for the composite filler to enter the lattice defects. The modified zinc oxide whiskers are grafted with silane coupling agents. The silane coupling agents may undergo preliminary hydrolysis to generate -OH, but at this time, the number of hydroxyl groups on the surface of the regenerated lithium iron phosphate is small, and the degree of reaction is limited.

[0084] During the calcination process of regenerated lithium iron phosphate material, the one-dimensional structure of cerium-doped carbon nanotubes and the needle-like structure of modified zinc oxide whiskers are embedded into lattice defects and pores through physical filling, while achieving stable bonding through interfacial interactions at high temperatures. Under high-temperature conditions, the regenerated lithium iron phosphate lattice is reconstructed and exposes a large number of -OH groups, while the residual La from titanium-lanthanum modification remains. 3+ Ti 4+ The active sites are also more reactive. The -OH generated by the hydrolysis of the silane coupling agent undergoes dehydration condensation with these groups to form stable Si-OP (reacting with POH on the surface of lithium iron phosphate) or Si-O-Ti (reacting with the residual Ti-OH of titanium-lanthanum modification) bonds.

[0085] In some optional embodiments of this application, before heat treatment of the mixture, the preparation method further includes: ball milling the mixture at a ball milling speed of 350 r / min to 450 r / min and a ball milling time of 2.5 h to 3.5 h.

[0086] In this embodiment, the ball milling stage only achieves physical uniformity of the composite filler, titanium-lanthanum synergistic modifier, lithium iron phosphate waste, lithium replenishing agent, etc.

[0087] In some optional embodiments of this application, adding a silane coupling agent, a carboxylated graphene co-activator, and a solvent to graphite powder to obtain a suspension includes:

[0088] Graphite powder, silane coupling agent and carboxylated graphene coupling agent are mixed to obtain graphite mixture. Solvent is added to graphite mixture and ultrasonic dispersion is performed to prepare suspension.

[0089] In this embodiment, ultrasonic dispersion achieves uniform suspension of graphite powder, silane coupling agent, and carboxylated graphene in the solvent without chemical bonding reaction. The purpose is to avoid agglomeration of the three components and create contact conditions for subsequent reactions.

[0090] In some optional embodiments of this application, the mass fraction of the silane coupling agent is 0.6% to 0.8% and the mass fraction of the carboxylated graphene coupling agent is 0.6% to 0.8% based on the mass of the graphite mixture.

[0091] By controlling the amounts of silane coupling agent and carboxylated graphene within the above-mentioned range, efficient synergistic modification can be achieved.

[0092] The appropriate amount of silane coupling agent can act as a "molecular bridge" to firmly graft carboxylated graphene onto the graphite surface, while avoiding the formation of an excessively thick organic coating layer. This ensures unobstructed electron conduction and lithium-ion migration channels, and prevents excessive silane coupling agent from self-polymerizing to form tiny organic particles, which could lead to electrode pore blockage and reduced electrolyte wettability.

[0093] With appropriate amounts of carboxyl-based graphene, and under the effective anchoring of silane coupling agents, it is uniformly dispersed without stacking or agglomeration, fully constructing a three-dimensional conductive network, significantly improving the rate performance and structural stability of graphite. The carboxyl groups on the surface of the grafted graphene are effectively "passivated" or participate in covalent bonding, reducing side reactions with the electrolyte, inhibiting excessive SEI film formation, and reducing irreversible capacity loss.

[0094] Silane coupling agents precisely "bridge" to achieve a strong bond between graphite and graphene, inhibiting graphene agglomeration; graphene can be uniformly coated on the graphite surface to form a highly efficient conductive network, improving conductivity and structural stability; the tight interfacial bonding reduces side reactions and balances capacity, rate capability, and cycle performance.

[0095] In some optional embodiments of this application, the solvent is a mixture of water and anhydrous ethanol, and the solid content of the suspension is 10% to 15%. The volume ratio of water to anhydrous ethanol is 1:(1 to 4).

[0096] Silane coupling agents undergo hydrolysis in suspension. The role of anhydrous ethanol in the suspension is to: improve the solubility of the silane coupling agent in the aqueous phase, avoiding excessive local concentration that could lead to self-polymerization; adjust the viscosity of the suspension, facilitating the uniform dispersion of graphite powder and carboxylated graphene coupling agent, without affecting the hydrolysis reaction, but rather providing a stable system for the reaction.

[0097] In some optional embodiments of this application, the ultrasonic dispersion time is 35 min to 45 min.

[0098] In some optional embodiments of this application, the particle size D50 of the graphite powder is 10μm~12μm, and the purity of the graphite powder is not less than 99.5%.

[0099] In some optional embodiments of this application, heat treatment of the suspension includes:

[0100] The suspension was dried at 100℃~130℃ for 2h~3h, and then heat-treated at 180℃~220℃ for 2h~4h under an inert gas atmosphere.

[0101] In this embodiment, during the drying process, solvent water and ethanol are removed, causing the silane coupling agent to hydrolyze (react with residual trace water) to generate -Si-OH. Then, the suspension is heated at 180℃~220℃ for 2h~4h under an inert gas atmosphere. This process drives the hydrolyzed silane coupling agent to undergo dehydration condensation with -OH groups on the graphite surface, and the silane coupling agent to undergo double bond addition and hydroxyl condensation reactions with carboxyl graphene, forming stable covalent bonds.

[0102] In some optional embodiments of this application, the sequential acid washing, drying, and sorting of graphite waste includes:

[0103] Add graphite waste to the mixed acid solution and stir for 40-50 minutes at a stirring rate of 80-100 r / min. Then filter to obtain filter cake. Wash the filter cake multiple times until the pH of the washing solution is 6.5-7.0.

[0104] The filter cake is dried at 110℃~115℃ for 6.5h~7.5h, and then impurity particles with a particle size <1μm are removed by airflow separation; wherein the separation velocity of airflow separation is 10m / s~12m / s.

[0105] In this embodiment, the wastewater generated during the pickling process is recycled after the following treatment: calcium hydroxide neutralizer is added to the wastewater to adjust the pH to 6.5~7.5, the water is allowed to stand for 2 hours to settle, impurities are removed by filtration, and then the water is treated by reverse osmosis membrane filtration (molecular weight cutoff 100 Da) to obtain reclaimed water, which is then recycled for graphite washing or slurry preparation, with a recycling rate of ≥85%.

[0106] In some optional embodiments of this application, the mixed acid solution includes hydrochloric acid and nitric acid, with the hydrochloric acid having a mass fraction of 10% to 15% and the nitric acid having a mass fraction of 10% to 30% based on the mass of the mixed acid solution.

[0107] In some optional embodiments of this application, the liquid-to-solid ratio of the mixed acid solution to the graphite waste is (5~10):1 mL / g.

[0108] In some optional embodiments of this application, the Li / Fe molar ratio of the recycled lithium iron phosphate material is 1.02~1.03, the crystallinity is ≥97%, and the specific surface area is 12m². 2 / g~18m 2 / g;

[0109] The tap density of the recycled graphite material is 1.1 g / cm³. 3 ~1.6g / cm 3 .

[0110] In another embodiment, a regenerable battery is provided, which is prepared by the above-described method for preparing a regenerable battery.

[0111] In this embodiment, the regenerated battery has a positive to negative electrode capacity ratio of (1.06~1.08):1. The electrolyte is made by dissolving 1 mol / L LiPF6 in a mixed carbonate solvent system, with 6 wt%~8 wt% Li6PS5Cl solid electrolyte particles and 0.3 wt%~0.4 wt% vinylene carbonate (VC) additive added. The mixed carbonate solvent system has a volume ratio of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) of 1:1:1. The average interfacial contact angle between the electrolyte and the positive (or negative) electrode is ≤25°, constructing a highly efficient ion transport channel while suppressing side reactions on the electrode surface, thus solving the performance degradation problem caused by the mismatch between the positive and negative electrodes and the high interfacial impedance. In this embodiment, the separator is a ceramic-coated polyethylene separator with a pore size of 0.1 μm~0.3 μm and a porosity of 40%~45%.

[0112] The present application is further illustrated below with reference to embodiments and comparative examples. Unless otherwise specified, the raw materials, reagents, materials and equipment used in this application are all commercially available products conventionally used in the art.

[0113]

Example 1

[0114] 1. Acquisition of lithium iron phosphate waste: Retired lithium iron phosphate batteries were deep discharged to 2.0V, mechanically crushed, and separated by airflow separation to obtain positive electrode sheets; pyrolysis was carried out at 520℃ for 4h under argon atmosphere (heating rate 5℃ / min) to remove PVDF binder and residual electrolyte; aluminum foil was recovered by density separation (separation wind speed 13m / s), and lithium iron phosphate waste with D50=4μm was collected; the lithium iron phosphate waste was tested and found to have an initial Li / Fe molar ratio of 0.88 and a crystallinity of 78%.

[0115] 2. Preparation of regenerated lithium iron phosphate materials and cathode sheets:

[0116] S1: Take 93.7g of lithium iron phosphate waste, add 5g of lithium carbonate supplement and 1.3g of residual lithium precipitate (the lithium carbonate content in the residual lithium precipitate is 92%), and mix in a twin-screw mixer at a speed of 160r / min for 25min to obtain a premix;

[0117] S2: Add 3.5g of composite filler (cerium-doped carbon nanotubes to modified zinc oxide whiskers mass ratio 1.3:1) and 2g of titanium-lanthanum synergistic modifier (Ti:La molar ratio 2:1) to the premix, and ball mill in a planetary ball mill at a speed of 400r / min for 3h (ball-to-material ratio 15:1) to obtain a mixture;

[0118] S3: The mixture was pre-calcined at 350℃ for 3 hours under a nitrogen atmosphere, then heated to 770℃ at a rate of 3℃ / min and calcined for 9 hours. It was then naturally cooled to room temperature (25℃) to obtain recycled lithium iron phosphate material. Testing showed that the recycled lithium iron phosphate material had a Li / Fe molar ratio of 1.025, a crystallinity of 97.3%, and a specific surface area of ​​15 m². 2 / g;

[0119] S4: Weigh out recycled lithium iron phosphate material, acetylene black, and PVDF in a mass ratio of 86:9:5, add N-methylpyrrolidone to prepare a slurry with a solid content of 48%, and coat it onto a 12μm thick aluminum foil using a comma-shaped doctor blade. The coating surface density is 210g / m². 2 After drying with hot air at 80℃ for 30 min, the material was vacuum dried at 120℃ (vacuum degree -0.095MPa) for 12 h, and then rolled under a pressure of 9MPa to obtain a recycled lithium iron phosphate positive electrode sheet with a thickness of 125μm and a compaction density of 2.45g / cm³. 3 .

[0120] 3. Preparation of recycled graphite materials and negative electrode sheets:

[0121] T1: Graphite waste is obtained by mechanically peeling off the negative electrode sheets of retired lithium iron phosphate batteries and airflow sorting (sorting wind speed 9m / s). The graphite waste is tested to have an initial purity of 90% and a total impurity content of 8.5%.

[0122] T2: Take graphite waste, add 1000mL of hydrochloric acid and nitric acid mixed acid solution (13%HCl+25%HNO3), stir at 90r / min for 45min at room temperature (25℃), filter to obtain filter cake, wash the filter cake with deionized water several times until the pH of the washing liquid is 6.8;

[0123] T3: The filter cake was dried by forced air at 112℃ for 7 hours. Impurities with a particle size <1μm were removed by air separation (separation velocity 11m / s) to obtain graphite powder with D50=11μm. The purity of the graphite powder was tested to be 99.6%, and the tap density was 1.12g / cm³. 3 ;

[0124] T4: Add 0.7g of silane coupling agent KH550 and 0.7g of carboxylated graphene coupling agent to 98.6g of graphite powder to obtain a graphite mixture. Add a mixture of water and anhydrous ethanol (volume ratio of water to anhydrous ethanol is 1:3) to the graphite mixture to prepare a suspension with a solid content of 12%. Disperse the suspension by ultrasonication at 300W for 40min, dry it at 100℃ for 2h, and then heat treat it at 200℃ for 2h under a nitrogen atmosphere to obtain recycled graphite material.

[0125] T5: Weigh recycled graphite material, conductive carbon black, and CMC-SBR binder in a mass ratio of 91:4:5, add water to prepare a slurry with a solid content of 42%, and coat it onto an 8μm thick copper foil with a coating surface density of 105g / m². 2 After drying with hot air at 80℃ for 40 min, the material was vacuum dried at 110℃ (vacuum degree -0.095MPa) for 10 h, and then rolled under 7MPa pressure to obtain a repaired graphite negative electrode sheet with a thickness of 95μm and a compaction density of 1.65g / cm³. 3 .

[0126] 4. Battery assembly:

[0127] Stacking: The recycled lithium iron phosphate positive electrode, ceramic-coated polyethylene separator (pore size 0.2μm, porosity 42%), and repaired graphite negative electrode are stacked in sequence, and the positive and negative electrode capacity ratio is controlled to be 1.07:1. The electrode is then installed in an aluminum-plastic film battery case.

[0128] Electrolyte injection: Inject electrolyte (1 mol / L LiPF6 dissolved in EC / EMC / DMC (volume ratio 1:1:1) mixed carbonate solvent system, and add 7 wt% Li6PS5Cl and 0.4 wt% VC) into an argon glove box (water and oxygen content ≤1 ppm). The electrolyte injection volume is 9% of the battery mass. Let stand for 30 min.

[0129] Packaging: Hot-press packaging at 125℃ and 0.4MPa for 4s yields an unformed battery;

[0130] Formation: A stepped formation process is adopted, with constant current charging at 0.05C to 3.2V and resting for 20 minutes; constant current charging at 0.1C to 3.65V and resting for 30 minutes; and constant current discharging at 0.1C to 2.0V.

[0131] Aging: After standing at 25℃ for 24 hours, a 1Ah soft-pack regenerated battery was obtained.

[0132]

Example 2

[0133] 1. Acquisition of lithium iron phosphate waste: Retired lithium iron phosphate batteries were deep discharged to 2.0V, mechanically crushed, and then air-separated to obtain positive electrode sheets; pyrolysis was performed at 500℃ for 4.5h under an argon atmosphere (heating rate 5℃ / min), and aluminum foil was recovered by density separation (wind speed 12m / s). Lithium iron phosphate waste with D50=3μm was collected. The lithium iron phosphate waste was tested and found to have an initial Li / Fe molar ratio of 0.85 and a crystallinity of 75%.

[0134] 2. Preparation of regenerated lithium iron phosphate materials and cathode sheets:

[0135] S1: Take 94.8g of lithium iron phosphate waste, add 4g of lithium carbonate and 1.2g of residual lithium precipitate (the lithium carbonate content in the residual lithium precipitate is 90%), and mix in a twin-screw mixer at a speed of 150r / min for 30min to obtain a premix;

[0136] S2: Add 3g of composite filler (cerium-doped carbon nanotubes: modified zinc oxide whiskers = 1.2:1) and 1.5g of titanium-lanthanum synergistic modifier (Ti:La molar ratio 2:1) to the premix, and ball mill in a planetary ball mill at a speed of 350r / min for 3.5h (ball-to-material ratio 15:1) to obtain a mixture;

[0137] S3: The mixture was pre-calcined at 350℃ for 3 hours in a nitrogen atmosphere, then heated to 760℃ at a rate of 3℃ / min and calcined for 9.5 hours. It was then naturally cooled to room temperature (25℃) to obtain recycled lithium iron phosphate material. Testing showed that the Li / Fe molar ratio of the recycled lithium iron phosphate material was 1.02, the crystallinity was 97.0%, and the specific surface area was 12 m². 2 / g;

[0138] S4: Weigh out recycled lithium iron phosphate material, acetylene black, and PVDF in a mass ratio of 86:9:5, add N-methylpyrrolidone to prepare a slurry with a solid content of 48%, and coat it onto a 12μm thick aluminum foil using a comma-shaped doctor blade. The coating surface density is 210g / m². 2 After being dried with hot air at 80℃ for 30 minutes, it was then vacuum dried at 120℃ (vacuum degree -0.095MPa) for 12 hours, and finally rolled under a pressure of 9MPa to obtain a regenerated lithium iron phosphate positive electrode sheet with a thickness of 125μm and a compaction density of 2.45g / cm³. 3 .

[0139] 3. Preparation of recycled graphite materials and negative electrode sheets:

[0140] T1: Graphite waste is obtained by mechanically peeling and airflow sorting (wind speed 8m / s) the negative electrode sheets of retired lithium iron phosphate batteries. The initial purity of the negative electrode graphite is tested to be 88%, and the impurity content is 11%.

[0141] T2: Take graphite waste, add 1000mL of hydrochloric acid-nitric acid mixed solution (13%HCl+25%HNO3), stir at 90r / min for 45min at 25℃, filter to obtain filter cake, wash the filter cake with deionized water several times until the pH of the washing liquid is 6.5;

[0142] T3: The filter cake was dried by forced air at 110℃ for 7.5 hours. Impurities with a particle size <1μm were removed by air separation (separation velocity 10m / s) to obtain graphite powder with D50=10μm. The purity of the graphite powder was tested to be 99.56%, and the tap density was 1.10g / cm³. 3 ;

[0143] T4: Add 0.6g of silane coupling agent KH550 and 0.6g of carboxylated graphene coupling agent to 98.8g of graphite powder to obtain a graphite mixture. Add a mixture of water and anhydrous ethanol (volume ratio of water to anhydrous ethanol is 1:3) to the graphite mixture to prepare a suspension with a solid content of 10%. Disperse the suspension by ultrasonication at 300W for 35min, dry it at 100℃ for 2h, and then heat-treat it at 200℃ for 2h under a nitrogen atmosphere to obtain recycled graphite material.

[0144] T5: Weigh recycled graphite material, conductive carbon black, and CMC-SBR binder in a mass ratio of 91:4:5, add water to prepare a slurry with a solid content of 42%, and coat it onto an 8μm thick copper foil with a coating surface density of 105g / m². 2 After drying with hot air at 80℃ for 40 min, the material was vacuum dried at 110℃ (vacuum degree -0.095MPa) for 10 h, and then rolled under 7MPa pressure to obtain a repaired graphite negative electrode sheet with a thickness of 95μm and a compaction density of 1.65g / cm³. 3 .

[0145] 4. Battery assembly:

[0146] Stacking: The recycled lithium iron phosphate positive electrode, ceramic-coated polyethylene separator (pore size 0.2μm, porosity 42%), and repaired graphite negative electrode are stacked in sequence, and the positive and negative electrode capacity ratio is controlled to be 1.07:1. The electrode is then installed in an aluminum-plastic film battery case.

[0147] Electrolyte injection: Inject electrolyte (1 mol / L LiPF6 dissolved in EC / EMC / DMC (volume ratio 1:1:1) mixed carbonate solvent system, and add 7 wt% Li6PS5Cl and 0.4 wt% VC) into an argon glove box (water and oxygen content ≤1 ppm). The electrolyte injection volume is 9% of the battery mass. Let stand for 30 min.

[0148] Packaging: Hot-press packaging at 125℃ and 0.4MPa for 4s yields an unformed battery;

[0149] Formation: A stepped formation process is adopted, with constant current charging at 0.05C to 3.2V and resting for 20 minutes; constant current charging at 0.1C to 3.65V and resting for 30 minutes; and constant current discharging at 0.1C to 2.0V.

[0150] Aging: After standing at 25℃ for 24 hours, a 1Ah soft-pack regenerated battery was obtained.

[0151]

Example 3

[0152] 1. Acquisition of lithium iron phosphate waste: Retired lithium iron phosphate batteries were deep discharged to 2.0V, mechanically crushed, and separated by airflow separation to obtain positive electrode sheets; pyrolysis was performed at 550℃ for 4.5h under argon atmosphere (heating rate 5℃ / min) to remove PVDF binder and residual electrolyte; aluminum foil was recovered by density separation (separation wind speed 15m / s), and lithium iron phosphate waste with D50=5μm was collected; the lithium iron phosphate waste was tested and found to have an initial Li / Fe molar ratio of 0.92 and a crystallinity of 82%.

[0153] 2. Regenerated lithium iron phosphate materials and cathode sheets:

[0154] S1: Take 92.5g of lithium iron phosphate waste, add 6g of lithium carbonate supplement and 1.5g of residual lithium precipitate (the lithium carbonate content in the residual lithium precipitate is 93%), and mix in a twin-screw mixer at a speed of 180r / min for 220min to obtain a premix;

[0155] S2: Add 4g of composite filler (cerium-doped carbon nanotubes to modified zinc oxide whiskers mass ratio 1.5:1) and 2.5g of titanium-lanthanum synergistic modifier (Ti:La molar ratio 2:1) to the premix, and ball mill in a planetary ball mill at a speed of 450r / min for 2.5h (ball-to-material ratio 15:1) to obtain a mixture;

[0156] S3: The mixture was pre-calcined at 350℃ for 3 hours under a nitrogen atmosphere, then heated to 780℃ at a rate of 3℃ / min and calcined for 8.5 hours. It was then naturally cooled to room temperature (25℃) to obtain recycled lithium iron phosphate material. Testing showed that the recycled lithium iron phosphate material had a Li / Fe molar ratio of 1.03, a crystallinity of 97.8%, and a specific surface area of ​​18 m². 2 / g;

[0157] S4: Weigh out recycled lithium iron phosphate material, acetylene black, and PVDF in a mass ratio of 86:9:5, add N-methylpyrrolidone to prepare a slurry with a solid content of 48%, and coat it onto a 12μm thick aluminum foil using a comma-shaped doctor blade. The coating surface density is 210g / m². 2 After being dried with hot air at 80℃ for 30 minutes, it was then vacuum dried at 120℃ (vacuum degree -0.095MPa) for 12 hours, and finally rolled under a pressure of 9MPa to obtain a regenerated lithium iron phosphate positive electrode sheet with a thickness of 125μm and a compaction density of 2.45g / cm³. 3 .

[0158] 3. Preparation of recycled graphite materials and negative electrode sheets:

[0159] T1: Graphite waste is obtained by mechanically peeling off the negative electrode sheets of retired lithium iron phosphate batteries and airflow sorting (sorting wind speed 10m / s). The graphite waste is tested to have an initial purity of 92% and a total impurity content of 7%.

[0160] T2: Take graphite waste, add 1000mL of hydrochloric acid-nitric acid mixed solution (13%HCl+25%HNO3), stir at 90r / min for 45min at room temperature (25℃), filter to obtain filter cake, wash the filter cake with deionized water several times until the pH of the washing liquid is 7.0;

[0161] T3: The filter cake was dried by forced air at 115℃ for 6.5 hours. Impurities with a particle size <1μm were removed by air separation (separation velocity 12m / s) to obtain graphite powder with D50=12μm. The purity of the graphite powder was tested to be 99.8%, and the tap density was 1.15g / cm³. 3 ;

[0162] T4: Add 0.8g of silane coupling agent KH550 and 0.8g of carboxylated graphene coupling agent to 98.4g of graphite powder to obtain a graphite mixture. Add a mixture of water and anhydrous ethanol (volume ratio of water to anhydrous ethanol is 1:3) to the graphite mixture to prepare a suspension with a solid content of 15%. Disperse the suspension by ultrasonication at 300W for 45min, dry it at 100℃ for 2h, and then heat treat it at 200℃ for 2h under a nitrogen atmosphere to obtain recycled graphite material.

[0163] T5: Weigh recycled graphite material, conductive carbon black, and CMC-SBR binder in a mass ratio of 91:4:5, add water to prepare a slurry with a solid content of 42%, and coat it onto an 8μm thick copper foil with a coating surface density of 105g / m². 2 After drying with hot air at 80℃ for 40 min, the material was vacuum dried at 110℃ (vacuum degree -0.095MPa) for 10 h, and then rolled under 7MPa pressure to obtain a repaired graphite negative electrode sheet with a thickness of 95μm and a compaction density of 1.65g / cm³. 3 .

[0164] 4. Battery assembly:

[0165] Stacking: The recycled lithium iron phosphate positive electrode, ceramic-coated polyethylene separator (pore size 0.2μm, porosity 42%), and repaired graphite negative electrode are stacked in sequence, and the positive and negative electrode capacity ratio is controlled to be 1.07:1. The electrode is then installed in an aluminum-plastic film battery case.

[0166] Electrolyte injection: Inject electrolyte (1 mol / L LiPF6 dissolved in EC / EMC / DMC (volume ratio 1:1:1) mixed carbonate solvent system, and add 7 wt% Li6PS5Cl and 0.4 wt% VC) into an argon glove box (water and oxygen content ≤1 ppm). The electrolyte injection volume is 9% of the battery mass. Let stand for 30 min.

[0167] Packaging: Hot-press packaging at 125℃ and 0.4MPa for 4s yields an unformed battery;

[0168] Formation: A stepped formation process is adopted, with constant current charging at 0.05C to 3.2V and resting for 20 minutes; constant current charging at 0.1C to 3.65V and resting for 30 minutes; and constant current discharging at 0.1C to 2.0V.

[0169] Aging: After standing at 25℃ for 24 hours, a 1Ah soft-pack regenerated battery was obtained.

[0170] [Comparative Example 1] (Without using collaborative regeneration and adaptation technology)

[0171] 1. Obtaining lithium iron phosphate waste: The lithium iron phosphate waste used in Comparative Example 1 is the same as that used in Example 1.

[0172] 2. Preparation of regenerated lithium iron phosphate materials and cathode sheets:

[0173] 100g of lithium iron phosphate waste was pre-calcined at 350℃ for 3h under a nitrogen atmosphere, then heated to 770℃ at 3℃ / min for 9h, and naturally cooled to room temperature of 25℃ to obtain recycled lithium iron phosphate material. The Li / Fe molar ratio of the recycled lithium iron phosphate material was found to be 0.90 and the crystallinity was 80%.

[0174] The preparation of the positive electrode is the same as step S4 in Example 1.

[0175] 3. Preparation of recycled graphite materials and negative electrode sheets:

[0176] The graphite waste used in Comparative Example 1 is the same as that used in Example 1.

[0177] 100g of graphite waste was washed with water to remove impurities, yielding recycled graphite material. Testing showed the recycled graphite material to have a purity of 95% and a tap density of 0.98g / cm³. 3 .

[0178] 4. Battery assembly:

[0179] Stacking: The recycled lithium iron phosphate positive electrode, ceramic-coated polyethylene separator (pore size 0.2μm, porosity 42%), and repaired graphite negative electrode are stacked in sequence, and the positive and negative electrode capacity ratio is controlled to be 1:1. They are then installed in an aluminum-plastic film battery case.

[0180] Electrolyte injection: Inject electrolyte (1 mol / L LiPF6 dissolved in a mixed carbonate solvent system of EC / EMC / DMC (volume ratio 1:1:1)) into an argon glove box (water and oxygen content ≤1 ppm). The electrolyte injection volume is 9% of the battery mass. Let stand for 30 min.

[0181] Packaging: Hot-press packaging at 125℃ and 0.4MPa for 4s yields an unformed battery;

[0182] Formation: A stepped formation process is adopted, with constant current charging at 0.05C to 3.2V and resting for 20 minutes; constant current charging at 0.1C to 3.65V and resting for 30 minutes; and constant current discharging at 0.1C to 2.0V.

[0183] Aging: After standing at 25℃ for 24 hours, a 1Ah soft-pack regenerated battery was obtained.

[0184]

Comparative Example 2

[0185] 1. Raw material processing:

[0186] Lithium iron phosphate waste (same as in Example 1) was used to prepare recycled lithium iron phosphate using a traditional sulfuric acid leaching-precipitation purification-recrystallization process with a Li / Fe molar ratio of 1.01 and a crystallinity of 95%.

[0187] The specific steps of the traditional sulfuric acid leaching-precipitation purification-recrystallization process are as follows:

[0188] (1) Sulfuric acid leaching: The crushed lithium iron phosphate waste (particle size usually ≤100μm) is added to the reactor, and a 15% sulfuric acid solution is added at a liquid-to-solid ratio (10:1 mL / g). The mixture is stirred at 100r / min and heated to 80℃ for 3h to allow Li to leach out. + Fe 2 + PO4 3- After being fully dissolved in the solution, the reaction formula is simplified to: LiFePO4 + H2SO4 → Li2SO4 + FeSO4 + H3PO4 + H2O; after leaching, the solution is filtered to remove insoluble impurities (such as carbon powder and aluminum foil residue) to obtain a leachate containing lithium, iron and phosphorus.

[0189] (2) Precipitation purification: Add H2O2 oxidant to the leachate to remove Fe 2+ Oxidized to Fe 3+ The pH of the solution was then adjusted to 4 with ammonia to allow Fe to... 3+ Al 3+ After the metallic impurities form hydroxide precipitates, they are separated by filtration; then sodium fluoride is added to the purified solution to remove calcium. 2+ Mg 2+ Impurities (forming fluoride precipitates) are removed, and a second filtration yields a high-purity lithium-phosphorus mixture.

[0190] (3) Recrystallization preparation: Add ammonium dihydrogen phosphate precipitant to the purified lithium-phosphorus mixture, adjust the pH to 8, control the temperature to 80℃, stir the reaction for 2h to generate lithium iron phosphate precursor precipitate; filter and wash the precursor until the pH of the wash liquid is 7.0, and then calcine at 800℃ for 6h in an inert gas atmosphere to obtain regenerated lithium iron phosphate material through crystal reconstruction.

[0191] Graphite waste (same as in Example 1) was purified using a traditional alkali washing-water washing process, achieving a purity of 98% and a tap density of 1.05 g / cm³. 3 .

[0192] The specific steps of the traditional alkaline washing-water washing process for purification are as follows:

[0193] (1) Alkali washing treatment: Add graphite waste into the reactor, add 10% sodium hydroxide solution at a liquid-solid ratio of 15:1 mL / g, stir at 100r / min, heat to 100℃ and react for 2h; use the alkaline solution to react with impurities (such as aluminum, copper oxides, residual PVDF binder hydrolysate) to generate soluble salts (such as sodium aluminate), thereby separating impurities from graphite.

[0194] (2) Water washing and neutralization: After the alkaline washing reaction, the graphite filter cake is obtained by filtration and washed with deionized water multiple times until the pH of the washing liquid is 7.0, so as to completely remove the residual alkaline solution and soluble impurities; if the impurities are high, the "alkaline washing-water washing" cycle can be repeated 1 to 2 times.

[0195] (3) Drying and purification: The washed graphite filter cake was dried at 120°C for 6 hours to remove moisture; then fine powder impurities with a particle size <1μm were removed by air separation or sieving, and finally the recycled graphite material (purity reached 98% in Comparative Example 2) was obtained.

[0196] 2. Battery preparation: The same assembly process as in Example 1 was used, but the acid washing wastewater was not recycled and was directly discharged.

[0197]

Comparative Example 3

[0198] 1. Obtaining lithium iron phosphate waste: The lithium iron phosphate waste used in Comparative Example 1 is the same as that used in Example 1.

[0199] 2. Preparation of regenerated lithium iron phosphate material and cathode: Same as in Example 1.

[0200] 3. Preparation of the negative electrode:

[0201] Weigh out virgin graphite material, conductive carbon black, and CMC-SBR binder in a mass ratio of 91:4:5, add water to prepare a slurry with a solid content of 42%, and coat it onto an 8μm thick copper foil with a coating surface density of 105g / m². 2 After drying with hot air at 80℃ for 40 min, the material was vacuum dried at 110℃ (vacuum degree -0.095MPa) for 10 h, and then rolled under 7MPa pressure to obtain a repaired graphite negative electrode sheet with a thickness of 95μm and a compaction density of 1.65g / cm³. 3 .

[0202] 4. Battery assembly:

[0203] Stacking: The recycled lithium iron phosphate positive electrode, ceramic-coated polyethylene separator (pore size 0.2μm, porosity 42%), and repaired graphite negative electrode are stacked in sequence, and the positive and negative electrode capacity ratio is controlled to be 1.2:1, and then installed into an aluminum-plastic film battery case.

[0204] Electrolyte injection: Inject electrolyte (1 mol / L LiPF6 dissolved in EC / EMC / DMC (volume ratio 1:1:1) mixed carbonate solvent system, and add 7 wt% Li6PS5Cl and 0.4 wt% VC) into an argon glove box (water and oxygen content ≤1 ppm). The electrolyte injection volume is 9% of the battery mass. Let stand for 30 min.

[0205] Packaging: Hot-press packaging at 125℃ and 0.4MPa for 4s yields an unformed battery;

[0206] Formation: A stepped formation process is adopted, with constant current charging at 0.05C to 3.2V and resting for 20 minutes; constant current charging at 0.1C to 3.65V and resting for 30 minutes; and constant current discharging at 0.1C to 2.0V.

[0207] Aging: After standing at 25℃ for 24 hours, a 1Ah soft-pack regenerated battery was obtained.

[0208] [Performance Test Data]

[0209] The regenerated batteries prepared in each embodiment and comparative example were evaluated in terms of capacity characteristics, cycle performance, safety performance, and interface characteristics. Simultaneously, the regeneration methods employed were comprehensively assessed from both environmental and economic perspectives. The results are shown in Tables 1 to 7.

[0210] Table 1

[0211]

[0212] As shown in Table 1, the discharge specific capacity and initial coulombic efficiency of Examples 1 to 3 at different rates are better than those of Comparative Examples 1 to 3, especially the capacity retention ability is stronger at a high rate of 10C, indicating that the regenerated batteries obtained in Examples 1 to 3 have better electrochemical performance.

[0213] Table 2

[0214]

[0215] As shown in Table 2, Examples 1 to 3 are superior to Comparative Examples 1 to 3 in terms of cycle performance and internal resistance stability. The regenerated batteries obtained in each example have better long-cycle stability and lower internal resistance growth, indicating that the regenerated battery structure is more stable and has better electrochemical reversibility.

[0216] Table 3

[0217]

[0218] As shown in Table 3, under low temperature conditions of -20℃ (0.2C) and 0℃ (0.5C), the capacity retention rate of each embodiment was higher than that of each comparative embodiment.

[0219] At a high temperature of 45°C (1°C), the capacity retention of each embodiment was superior to that of the comparative examples. During high-temperature cycling at 60°C, the capacity retention of the embodiments after 50 and 100 cycles was higher than that of the comparative examples. Furthermore, the capacity loss of the embodiments after 7 days of storage at 60°C was only 2.8%–3.5%, lower than that of the comparative examples, and the capacity recovery rate of the embodiments after storage was as high as 98.5%–99.2%, superior to that of the comparative examples. In summary, the embodiments exhibited superior electrochemical stability, cycle durability, and storage performance under both high and low temperature environments.

[0220] Table 4

[0221]

[0222] As shown in Table 4, the embodiment is superior to the comparative example in terms of safety performance: the thermal runaway temperature of the embodiment reaches 210℃~220℃, which is higher than that of the comparative example (185℃~205℃).

[0223] The highest temperature during the short-circuit test in the example was 128℃~142℃, which was significantly lower than the 148℃~210℃ of the comparative example.

[0224] In the needle puncture test, all examples were punctured by a 3mm steel needle without ignition or explosion, while Comparative Example 1 emitted smoke, Comparative Example 2 had an odor, and Comparative Example 3 did not ignite or explode.

[0225] When overcharged to 4.5V, none of the examples showed bulging or leakage, while Comparative Examples 1 and 2 showed bulging but no leakage, and Comparative Example 2 showed both bulging and leakage. In summary, the examples exhibit higher thermal stability, stronger abuse tolerance, and more reliable safety performance.

[0226] Table 5

[0227]

[0228] As shown in Table 5, the average contact angle of the electrolyte in the embodiment is smaller than that in the comparative example, indicating better wettability. The interfacial impedance and charge transfer impedance of the embodiment are both lower than those in the comparative example. Furthermore, the lithium-ion diffusion coefficient of the embodiment is higher than that of the comparative example. In summary, the embodiment exhibits superior electrolyte wettability, lower interfacial and charge transfer impedance, and faster lithium-ion transport kinetics, which are beneficial for improving the rate performance and cycle stability of the battery.

[0229] Table 6

[0230]

[0231] As shown in Table 6, the embodiments outperform the comparative examples in terms of environmental indicators: the wastewater volume per ton of product in the embodiments is lower than that in the comparative examples; the recycling rate of pickling wastewater in the embodiments reaches 85%~90%, while it is 0% in comparative examples 1 and 2, and only 82% in comparative example 3; the lithium resource utilization rate in the embodiments is 83%~86%, which is higher than that in the comparative examples; the graphite recovery rate in the embodiments reaches 92%~93%, which is also significantly better than the 82%~85% in the comparative examples. In summary, the embodiments perform better in reducing wastewater discharge, improving resource recycling, and recovering key materials, and have a greener and more sustainable production process.

[0232] Table 7

[0233]

[0234] As shown in Table 7, the embodiments are significantly more economical than the comparative examples: the energy consumption per ton of product in the embodiments is lower than that in the comparative examples; the process cost is reduced by 25% to 28% compared to the traditional process, while the comparative examples do not show cost optimization; compared with Embodiment 1, the cost per Ah in Comparative Examples 1, 2, and 3 is 42%, 35%, and 45% higher, respectively. In summary, the embodiments not only have lower energy consumption and a significant cost advantage, but also possess stronger industrialization economic competitiveness.

[0235] [Performance Testing Methods]

[0236] All performance parameters involved in this embodiment were measured according to the following standards or methods:

[0237] I. Measurement methods for specific surface area, graphite purity, graphite tap density, capacity ratio of regenerated lithium iron phosphate cathode to regenerated graphite anode, interfacial contact angle between electrolyte and cathode / anode, Li / Fe molar ratio, and crystallinity.

[0238] 1. Specific surface area: The gas adsorption BET method is used. The national standard is GB / T 19587-2017 "Determination of specific surface area of ​​solids by gas adsorption BET method", the international standard is ISO 9277:2022 "Determination of specific surface area of ​​solids by gas adsorption method", and ASTM D6556-19 is also a commonly used international testing standard.

[0239] 2. Graphite purity: The core indicators are carbon content and ash content. Carbon content is detected using a high-frequency infrared carbon-sulfur analyzer, and ash content is detected using a high-temperature ignition method. The national standard is GB / T 3521-2008 "Methods for Chemical Analysis of Graphite," and the international standards include ISO 8005:2005 "Determination of Ash Content in Graphite from Carbon Materials" and ASTM C561-16 "Methods for Chemical Analysis of Graphite Powder."

[0240] 3. Tap density of graphite: Tested using a tap density meter. The national standard is GB / T 5162-2021 "Determination of tap density of metal powders", which is also applicable to the tap density testing of battery powder materials such as graphite powder.

[0241] 4. Capacity ratio of regenerated lithium iron phosphate cathode to regenerated graphite anode: First, measure the discharge specific capacity of the regenerated lithium iron phosphate cathode according to GB / T 42161 "Test Method for First Discharge Specific Capacity and First Charge-Discharge Efficiency of Lithium Iron Phosphate Electrochemical Performance", and measure the discharge specific capacity of the regenerated graphite anode according to relevant electrochemical test methods (such as the half-cell test method in Appendix G). Then, calculate the ratio between the two.

[0242] 5. Electrolyte-to-anode interface contact angle: Measure the static or dynamic contact angle using a contact angle meter. Follow international standards ISO 27448 and ASTM D7334. For domestic standards, refer to GB / T 2792 "Test Method for 180° Peel Strength of Pressure-Sensitive Adhesive Tapes" and other relevant auxiliary standards for interface performance testing.

[0243] 6. Li / Fe molar ratio: Detected by inductively coupled plasma optical emission spectrometry (ICP-OES). Refer to the relevant procedures for lithium ion detection in group standard T / CIECCPA 060-2025. This method can accurately determine the lithium and iron content to calculate their ratio.

[0244] 7. Crystallinity: X-ray diffraction (XRD) was used for analysis, combined with the Scherrer formula. The national standard is GB / T 30904 "X-ray Diffraction Method for Crystal Structure Analysis of Inorganic Chemical Products". For regenerated lithium iron phosphate, the integrity of crystallization can also be determined by referring to the JCPDS (01-83-2092) standard X-ray powder diffraction pattern of lithium iron phosphate.

[0245] II. Capacity Characteristic Test

[0246] 1. Discharge specific capacity (0.5C, 2C, 5C, 10C): Referring to GB / T 42161 "Test Method for First Discharge Specific Capacity and First Charge-Discharge Efficiency of Lithium Iron Phosphate Electrochemical Performance", constant current charge-discharge tests were performed on the battery using a battery tester at a constant temperature of 25℃. During the charging phase, the battery was charged at the corresponding rate with constant current to 3.65V, and during the discharging phase, it was discharged at the same rate with constant current to 2.0V. The discharge capacity was recorded and the specific capacity was calculated (unit: mAh / g).

[0247] 2. Initial Coulombic Efficiency: Based on the above 0.5C charge-discharge test data, it is calculated by "initial discharge capacity / initial charge capacity × 100%".

[0248] III. Cyclic Performance Testing

[0249] 1. Cycle capacity retention (100, 500, 1000 cycles): Referring to GB / T 31241-2024 "Safety Requirements for Lithium-ion Batteries and Battery Packs for Portable Electronic Products", the battery was subjected to charge-discharge cycle tests at 1C rate under 25℃ conditions. Each cycle followed the procedure of "constant current charging to 3.65V → constant current discharging to 2.0V". The discharge capacity was recorded for the first cycle and after the corresponding number of cycles. The capacity retention rate was calculated as "(nth discharge capacity / first discharge capacity) × 100%".

[0250] 2. Internal resistance and internal resistance growth rate: Using an AC impedance meter, within a frequency range of 10... -2 ~10 5 Under Hz conditions, the AC impedance of the battery was tested in its initial state and after 500 cycles at 1C, and the internal resistance data was recorded. The internal resistance growth rate was calculated as "(internal resistance after 500 cycles - initial internal resistance) / initial internal resistance × 100%".

[0251] IV. Wide Temperature Range Performance Test

[0252] 1. Low-temperature capacity retention (-20℃, 0℃): Referring to GB / T 31241-2024, the capacitors were allowed to stand for 2 hours at a constant temperature of -20℃ and 0℃ respectively, followed by constant current discharge at a rate of 0.2C (-20℃) or 0.5C (0℃) to 2.0V, and the low-temperature discharge capacity was recorded. The capacity retention rate was calculated as "low-temperature discharge capacity / 0.5C discharge capacity at 25℃ × 100%".

[0253] 2. High-Temperature Performance Testing: This includes high-temperature capacity retention, high-temperature cycle retention, and high-temperature storage performance. Specifically, the 45℃ capacity retention test follows the low-temperature testing procedure, discharging at a 1C rate; the 60℃ cycle retention test involves 50 or 100 charge-discharge cycles at a 1C rate in a 60℃ environment, calculating the capacity retention after each cycle; the 60℃ / 7-day storage performance test requires storage at 60℃ for 7 days, recording the capacity before and after storage, and calculating the storage capacity loss rate ((capacity before storage - capacity after storage) / capacity before storage × 100%) and the post-storage capacity recovery rate (recovered discharge capacity after storage / capacity before storage × 100%).

[0254] V. Safety Performance Testing

[0255] 1. Thermal runaway temperature: Referring to GB / T 31241-2024, an accelerated calorimeter (ARC) was used to heat the battery at a rate of 5℃ / min, and the battery temperature change was monitored in real time to record the critical temperature at which the battery would experience thermal runaway.

[0256] 2. Short circuit test: Refer to GB / T 31241-2024, short circuit the positive and negative terminals of the battery through an external wire with a resistance ≤50mΩ, monitor the temperature change of the battery in real time during the short circuit, and record the highest temperature.

[0257] 3. Needle penetration test: Referring to GB / T 31241-2024, use a steel needle with a diameter of 3mm to vertically puncture the center of the battery at a speed of 5mm / s, and observe whether the battery exhibits abnormal phenomena such as fire or explosion.

[0258] 4. Overcharge test: Refer to GB / T 31241-2024, charge the battery at a constant current of 0.3C to 4.5V, continuously observe the battery status, and record whether there are any phenomena such as bulging or leakage.

[0259] VI. Interface Feature Testing

[0260] 1. Electrolyte contact angle: Following international standards ISO 27448 and ASTM D7334, a contact angle measuring instrument was used to drop electrolyte onto the surface of the positive and negative electrode plates at room temperature to test the static contact angle. Three different test points were selected for each electrode plate, and the average value was taken as the final result.

[0261] 2. Interface impedance and charge transfer impedance: An AC impedance meter was used to measure the impedance within a frequency range of 10 Hz. -2 ~10 5 The AC impedance spectrum of the battery was tested under Hz conditions, and the total interface impedance and charge transfer impedance data were extracted by equivalent circuit fitting.

[0262] 3. Lithium-ion diffusion coefficient: The diffusion coefficient of lithium ions in the electrode material is calculated based on the impedance spectrum data obtained from AC impedance testing and the Randles-Sevcik equation.

[0263] VII. Environmental Indicator Testing

[0264] 1. Wastewater per ton of product: Using the law of conservation of mass, the total wastewater generated by all processes such as acid washing and washing during the production of 1 ton of regenerated batteries is calculated.

[0265] 2. Pickling wastewater recycling rate: The total amount of pickling wastewater and the amount of wastewater recycled after neutralization-precipitation-reverse osmosis treatment are counted separately by flow metering equipment. The recycling rate is calculated by "recycled water volume / total pickling wastewater volume × 100%".

[0266] 3. Lithium resource utilization rate: Inductively coupled plasma optical emission spectrometry (ICP-OES) was used, referring to the group standard T / CIECCPA 060-2025, to determine the total lithium content in raw materials (cathode recovery materials, lithium supplementation agents, etc.) and the final product, and the result was calculated by "total lithium in the product / total lithium in the raw materials × 100%".

[0267] 4. Graphite recovery rate: The initial mass of the graphite anode recovery material and the final mass of the repaired graphite powder were statistically analyzed using the gravimetric method. The graphite recovery rate was calculated as "mass of repaired graphite powder / initial mass of graphite anode recovery material × 100%". The graphite purity was tested and calibrated according to GB / T 3521-2008 "Methods for Chemical Analysis of Graphite".

[0268] VIII. Economic Indicator Testing

[0269] 1. Energy consumption per ton of product: The total power consumption of all processes such as crushing, roasting, drying, and mixing during the production of 1 ton of recycled batteries is measured in real time by an electricity meter, and the energy consumption per ton of product is calculated.

[0270] 2. Process cost reduction rate: The cost per ton of product (including raw material procurement, energy consumption, environmental treatment, labor and other expenses) of the traditional recycling process and the process of this invention are calculated separately and obtained by "(traditional process cost - process cost of this invention) / traditional process cost × 100%".

[0271] 3. Cost per Ah: The cost per Ah (total production cost / total battery capacity) of each comparative example and Example 1 is calculated separately and obtained by "(cost per Ah of comparative example - cost per Ah of Example 1) / cost per Ah of Example 1 × 100%".

[0272] It should be noted that, in this document, "comprising," "including," or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0273] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0274] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a regenerable battery, characterized in that, The preparation method includes the following steps: Retired lithium iron phosphate batteries are pretreated to obtain lithium iron phosphate waste and graphite waste. The lithium iron phosphate waste, lithium carbonate lithium supplementer and residual lithium precipitate are mixed to obtain a premix, a composite filler and a titanium-lanthanum synergistic modifier are added to the premix to obtain a mixture, and the mixture is heat-treated to obtain recycled lithium iron phosphate material. The graphite waste is sequentially acid-washed, dried and sorted to obtain graphite powder. A silane coupling agent, a carboxylated graphene coupling agent and a solvent are added to the graphite powder to obtain a suspension. The suspension is then heat-treated to obtain recycled graphite material. Positive and negative electrode sheets are prepared based on the regenerated lithium iron phosphate material and the regenerated graphite material, and the positive electrode sheet, the negative electrode sheet, the electrolyte and the separator are assembled into a regenerated battery.

2. The method for preparing a regenerable battery according to claim 1, characterized in that, Based on the mass of the premix, the lithium carbonate supplement has a mass fraction of 4% to 6%, and the residual lithium precipitate has a mass fraction of 1.2% to 1.5%. The particle size D50 of the lithium iron phosphate waste is 3μm~5μm.

3. The method for preparing a regenerable battery according to claim 1, characterized in that, The residual lithium precipitate includes lithium carbonate, and based on the mass of the residual lithium precipitate, the mass fraction of lithium carbonate in the residual lithium precipitate is not less than 90%. The acquisition of the residual lithium precipitate includes: water leaching the graphite waste, filtering to obtain a lithium-containing leachate, evaporating and concentrating the lithium-containing leachate at 80℃~90℃, and then cooling and crystallizing to obtain the residual lithium precipitate.

4. The method for preparing a regenerable battery according to claim 1, characterized in that, The amount of the composite filler added is 3% to 4% of the mass of the premix, and the amount of the titanium-lanthanum synergistic modifier added is 1.5% to 2.5% of the mass of the premix; The composite filler comprises cerium-doped carbon nanotubes and modified zinc oxide whiskers, wherein the mass ratio of the cerium-doped carbon nanotubes to the modified zinc oxide whiskers is (1.2~1.5):

1.

5. The method for preparing a regenerable battery according to claim 1, characterized in that, The heat treatment of the mixture includes: The mixture was pre-calcined at 320℃~380℃ for 2h~4h in an inert gas atmosphere, and then heated to 760℃~780℃ for 8.5h~9.5h. Before heat treatment of the mixture, the preparation method further includes: ball milling the mixture at a ball milling speed of 350 r / min to 450 r / min for a ball milling time of 2.5 h to 3.5 h.

6. The method for preparing a regenerable battery according to claim 1, characterized in that, The step of adding a silane coupling agent, a carboxylated graphene coupling agent, and a solvent to the graphite powder to obtain a suspension includes: The graphite powder, silane coupling agent, and carboxylated graphene synergist are mixed to obtain a graphite mixture. A solvent is added to the graphite mixture and ultrasonically dispersed to prepare the suspension. Based on the mass of the graphite mixture, the mass fraction of the silane coupling agent is 0.6%~0.8%, and the mass fraction of the carboxylated graphene coupling agent is 0.6%~0.8%. The solvent is a mixture of water and anhydrous ethanol, and the solid content of the suspension is 10% to 15%. The ultrasonic dispersion time is 35 min to 45 min; The particle size D50 of the graphite powder is 10μm~12μm, and the purity of the graphite powder is not less than 99.5%.

7. The method for preparing a regenerable battery according to claim 1, characterized in that, The heat treatment of the suspension includes: The suspension is dried at 100℃~130℃ for 2h~3h, and then heat-treated at 180℃~220℃ for 2h~4h in an inert gas atmosphere.

8. The method for preparing a regenerable battery according to claim 1, characterized in that, The process of sequentially acid washing, drying, and sorting the graphite waste includes: Graphite waste is added to the mixed acid solution and stirred for 40 to 50 minutes at a stirring rate of 80 to 100 r / min. Then, the mixture is filtered to obtain a filter cake. The filter cake is washed multiple times until the pH of the washing solution is 6.5 to 7.

0. The filter cake is dried at 110℃~115℃ for 6.5h~7.5h, and then impurity particles with a particle size <1μm are removed by airflow separation; wherein the separation wind speed of the airflow separation is 10m / s~12m / s. The mixed acid solution includes hydrochloric acid and nitric acid, and based on the mass of the mixed acid solution, the mass fraction of hydrochloric acid is 10%~15%, and the mass fraction of nitric acid is 10%~30%. The liquid-to-solid ratio of the mixed acid solution to the graphite waste is (5~10):1mL / g.

9. The method for preparing a regenerable battery according to claim 1, characterized in that, The recycled lithium iron phosphate material has a Li / Fe molar ratio of 1.02~1.03, a crystallinity ≥97%, and a specific surface area of ​​12m². 2 / g~18m 2 / g; The tap density of the recycled graphite material is 1.1 g / cm³. 3 ~1.6g / cm 3 .

10. A regenerable battery, characterized in that, It is prepared by the method for preparing a regenerated battery according to any one of claims 1 to 9.

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