Recycling method of positive pole piece of lithium battery

Abstract

The invention provides a lithium battery positive pole piece recovery method, which comprises: S1, providing an eutectoid solution, the eutectoid solution comprising a quaternary ammonium salt compound, an amine compound and a lithium salt; s2, the positive pole piece of the lithium battery is heated in air and subjected to heat preservation treatment, and the positive pole piece reinforced by the binder is obtained; and S3, immersing the positive pole piece strengthened by the binder obtained in the S2 into the eutectic melt solution, and carrying out heating treatment to obtain the lithium-supplemented positive pole piece. According to the method, the pole powder and the current collector do not need to be separated from the positive pole piece through a mechanical method or binder degradation, energy consumption and pollution generated in the treatment process from the pole piece to the pole powder in the process of repairing the positive pole material are avoided, the operation is simple, the cost is low, wastewater pollutants are not generated, and the method is an ideal direct recovery scheme for the positive pole piece.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium batteries, and in particular relates to a method for recycling positive electrode sheets of lithium batteries. Background Art

[0002] With the rapid growth of lithium-ion batteries in electric vehicles and other fields, a large number of power lithium-ion batteries will be close to or reach the end of their life in the next few years. Recycling key materials, especially the most valuable cathode materials, has become a difficult and necessary task. Efficient and environmentally friendly recycling and reuse of lithium-ion battery materials can timely supplement the supply chain, and at the same time avoid the toxicity of discarded battery materials causing greater pollution to people and the environment, as well as the waste of resources caused by discarded battery materials.

[0003] At present, the widely used recycling methods mainly include pyrometallurgy, hydrometallurgy and direct recycling to recycle lithium-ion battery positive electrode materials. Among them, pyrometallurgy extracts precious metal materials through high-temperature smelting and multi-stage purification and separation processes, which consumes a lot of energy and lithium resources cannot be effectively protected; while hydrometallurgy recovers valuable metal elements through acid leaching and subsequent complicated extraction and precipitation steps. Although it has a higher recovery efficiency than pyrometallurgy, it still has a lot of wastewater treatment problems; direct recycling combines the physical separation process to separate and collect positive electrode materials, as well as the subsequent lithium supplementation process to repair the composition and structural defects of electrode materials, which greatly shortens the recycling process and reduces energy consumption and emissions.

[0004] Current lithium-ion battery repair technologies often focus on the processing of electrode powder materials. However, in actual working conditions, many waste lithium-ion batteries will fail due to the particularity of the use scenario, such as the failure of the negative electrode, electrolyte, battery cell structure or other comprehensive reasons, while the positive electrode material still maintains a good structure and performance, or only has minor usage defects. Therefore, its performance can be restored by directly processing the positive electrode sheet. Existing studies have found that possible defects in the positive electrode sheet include: a small amount of lithium ion loss, microcracks on the particle surface, and mechanical detachment caused by local failure of the binder. Existing recycling schemes often start from the electrode black powder layer, without targeted repairs for different lithium-ion battery failure modes, resulting in waste of resources and excessive processing. Therefore, it is of great significance to develop a simple, environmentally friendly, and low-cost method for recycling the positive electrode materials of waste lithium-ion batteries to improve the recycling efficiency of waste batteries and realize the recycling of key materials. Summary of the invention

[0005] In view of the problems existing in the prior art, this application aims to provide an environmentally friendly, simple process and low-cost lithium battery positive electrode plate recycling solution. This application aims to complete the repair and lithium replenishment at the positive electrode plate level of waste lithium batteries. Compared with the prior art, this method does not require the positive electrode plate to be separated from the active material powder and the current collector by mechanical methods or binder degradation, avoiding the energy consumption and pollution generated by the processing process from the plate to the active material powder in the positive electrode material repair.

[0006] In a first aspect, the present application provides a method for recycling a lithium battery positive electrode sheet, comprising:

[0007] S1, providing a eutectic solution, wherein the eutectic solution comprises a quaternary ammonium salt compound, an amine compound and a lithium salt;

[0008] S2, heating the positive electrode sheet of the lithium battery in air and performing heat preservation treatment to obtain a positive electrode sheet strengthened with a binder;

[0009] S3, immersing the binder-reinforced positive electrode sheet obtained in S2 into the eutectic solution, and performing a heating treatment to obtain a lithium-supplemented positive electrode sheet.

[0010] In some embodiments of the present application, in S1, raw materials including quaternary ammonium salt compounds and amine compounds are mixed to obtain a mixed solution, and then raw materials including lithium salts are added to the mixed solution to obtain the low eutectic solution.

[0011] In some embodiments of the present application, in S1, raw materials including quaternary ammonium salt compounds and amine compounds are first mixed at 50°C to 90°C to obtain a mixed solution, and then raw materials including lithium salts are added to the mixed solution, and mixed at 100°C to 130°C until the lithium salts are completely dissolved, thereby obtaining the low eutectic solution.

[0012] In some embodiments of the present application, the quaternary ammonium salt compound includes: choline chloride, choline acetate or acetylcholine, or a mixture of several thereof.

[0013] In some embodiments of the present application, the amine compound includes: urea, ethanolamine, triethanolamine, or a mixture of several thereof.

[0014] In some embodiments of the present application, the lithium salt includes at least one of lithium chloride, lithium bromide, lithium iodide, lithium hydroxide, lithium nitrate, lithium carbonate, and lithium perchlorate.

[0015] In some embodiments of the present application, the quaternary ammonium salt compound is choline chloride.

[0016] In some embodiments of the present application, the amine compound is urea.

[0017] In some embodiments of the present application, the lithium salt is lithium chloride.

[0018] In some embodiments of the present application, the molar ratio of the choline chloride, urea and lithium chloride is 1:(0.5-5):(0.1-2).

[0019] In some embodiments of the present application, in S2, the heating and heat preservation treatment in air includes heating to 130° C. to 190° C. in air and keeping the temperature for 4 to 6 hours. The heating and heat preservation temperature coincides with the melting temperature range of the binder in the positive electrode sheet.

[0020] In some embodiments of the present application, the binder in the positive electrode plate includes at least one of polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, and polypropylene.

[0021] In some embodiments of the present application, in S3, the heating treatment includes slowly stirring at 50°C to 80°C for 1 hour to 6 hours; after the heating treatment, taking out the heated positive electrode plate, washing it with an organic solvent and vacuum drying it.

[0022] In some embodiments of the present application, the organic solvent is ethanol.

[0023] In some embodiments of the present application, the positive electrode plate of the waste battery includes a positive electrode material, and the positive electrode material includes one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds.

[0024] In some embodiments of the present application, the lithium transition metal oxide is selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof.

[0025] In some embodiments of the present application, the olivine-structured lithium-containing phosphate is selected from one or more of lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and modified compounds thereof.

[0026] In a second aspect, the present application provides a secondary battery, which includes a positive electrode sheet recovered according to the method described in the first aspect.

[0027] Beneficial effects:

[0028] The technical solution of the present application is based on the inherent characteristics of the positive electrode sheet and its failure mechanism. It uses a low-temperature heating method to make the binder molten, so that it flows and migrates between the positive electrode particles, connects the detached particle plates, and infiltrates and wraps the particle microcracks on the positive electrode sheet, thereby avoiding direct contact with the electrolyte, and achieving the reconnection of the structural failure area by the binder, as well as the covering and protection of the microcracks. In addition, the low eutectic solution (DES) has shown advantages such as green, energy-saving, and degradable in recent years, and has therefore attracted everyone's attention and been widely used. The present application immerses the positive electrode sheet of the waste lithium-ion battery in a low eutectic solution and heats and stirs it to achieve lithium replenishment and repair of the positive electrode sheet under low temperature conditions. After the treatment of the positive electrode plate layer in the above two steps, a repaired and regenerated positive electrode plate can be obtained. This method does not need to separate the active material and the current collector by mechanical methods or binder degradation of the positive electrode plate, avoiding the energy consumption and pollution generated in the process from the plate to the active material powder in the positive electrode material repair. It is simple to operate, low-cost, and does not produce wastewater pollutants. It is an ideal direct recycling solution for positive electrode plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 A flow chart of a method for recycling positive electrode sheets of lithium batteries according to the present application is shown. DETAILED DESCRIPTION

[0031] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0032] The term "about" is used to describe and illustrate small changes. When used in conjunction with an event or situation, the term may refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very approximately. For example, when used in conjunction with a numerical value, the term may refer to a range of variation of less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. In addition, amounts, ratios, and other numerical values ​​are sometimes presented in this article in a range format. It should be understood that such a range format is for convenience and simplicity, and should be flexibly understood to include not only numerical values ​​explicitly designated as range limits, but also all individual numerical values ​​or subranges encompassed within the range, as if each numerical value and subrange were explicitly designated.

[0033] In the present application, the term "positive electrode sheet reinforced with a binder" refers to a lithium battery positive electrode sheet that is heated and heat-insulated in air, wherein the heating end temperature is set to be near the melting point of the binder, so that the binder is in a molten state and flows and migrates between the positive electrode particles, connecting the detached particle plates and penetrating and wrapping the particle microcracks on the positive electrode sheet, thereby avoiding direct contact with the electrolyte. Therefore, the positive electrode sheet after this step is called a "positive electrode sheet reinforced with a binder".

[0034] The present application is further described below in conjunction with specific implementations. It should be understood that these specific implementations are only used to illustrate the present application and are not used to limit the scope of the present application.

[0035] 1. Recycling method of lithium battery positive electrode

[0036] Taking the waste ternary lithium-ion battery as an example, the waste ternary lithium-ion battery is first discharged and disassembled into three parts, namely ① shell and diaphragm, etc.; ② waste positive electrode plate and ③ waste negative electrode plate. Among them, ① shell and diaphragm, etc. and ③ waste negative electrode plate are recycled by other means. Then, ② waste positive electrode plate is cleaned with dimethyl carbonate solvent and then treated as follows: Figure 1 The following steps are processed as shown:

[0037] S1, providing a eutectic solution, wherein the eutectic solution comprises a quaternary ammonium salt compound, an amine compound and a lithium salt;

[0038] S2, heating the positive electrode sheet of the lithium battery in air and performing heat preservation treatment to obtain a positive electrode sheet strengthened with a binder;

[0039] S3, immersing the binder-reinforced positive electrode sheet obtained in S2 into the eutectic solution, and performing a heating treatment to obtain a lithium-supplemented positive electrode sheet.

[0040] The technical solution of the present application is based on the inherent characteristics of the positive electrode plate and its failure mechanism. The binder is molten by low-temperature heating, so that it flows and migrates between the positive electrode particles, connects the detached particle plates and infiltrates and wraps the particle microcracks on the positive electrode plate, thereby avoiding direct contact with the electrolyte, and realizing the reconnection of the structural failure area by the binder, as well as the covering and protection of the microcracks. The present application immerses the positive electrode plate of the waste lithium-ion battery in a low eutectic solution for heating and stirring, and realizes the lithium replenishment and repair of the positive electrode plate under low temperature conditions. After the treatment of the positive electrode plate layer in the above two steps, a repaired and regenerated positive electrode plate can be obtained. This method does not require the positive electrode plate to be separated from the active material and the current collector by mechanical methods or binder degradation, avoiding the energy consumption and pollution generated in the process of processing from the plate to the active material powder in the repair of the positive electrode material, and is simple to operate, low cost, and does not produce wastewater pollutants. It is an ideal direct recovery solution for positive electrode plates.

[0041] In some embodiments of the present application, in S1, the raw materials including quaternary ammonium salt compounds and amine compounds are first stirred and mixed at 50°C to 90°C for about 20min to 60min, until a clear colorless liquid is formed to obtain a mixed solution, and then the raw materials including lithium salts are added to the mixed solution, and stirred for 5h to 7h at 100°C to 130°C until the lithium salts are completely dissolved, thereby obtaining the low eutectic solution. In some embodiments, the mixing temperature of the raw materials including quaternary ammonium salt compounds and amine compounds can be 50°C, 60°C, 70°C, 80°C, 90°C or any value between these values, and the stirring and mixing time can be 20min, 30min, 40min, 50min, 60min or any value between these values. In some embodiments, in the process of dissolving lithium salts, the heating temperature can be 100°C, 110°C, 120°C, 130°C or any value between these values, and the heating and stirring time can be 5h, 6h, 7h or any value between these values. In the preparation of eutectic solution, if the temperature is too low, the lithium replenishment reaction may occur too slowly from the perspective of kinetics; if the temperature is too high, the positive electrode material may dissolve in the eutectic solution. In recent years, deep eutectic solvent (DES) has shown advantages such as green, energy-saving and biodegradable, and has therefore attracted everyone's attention and been widely used.

[0042] In some embodiments of the present application, the quaternary ammonium salt compound includes: one or a mixture of choline chloride, choline acetate or acetylcholine. The amine compound includes: one or a mixture of urea, ethanolamine, triethanolamine. The lithium salt includes: at least one of lithium chloride, lithium bromide, lithium iodide, lithium hydroxide, lithium nitrate, lithium carbonate, and lithium perchlorate.

[0043] In some embodiments of the present application, the quaternary ammonium salt compound is choline chloride; the amine compound is urea; and the lithium salt is lithium chloride. Urea and choline chloride are combined as hydrogen bond donors and acceptors to form a low eutectic solvent system, which can be used as a solvent to dissolve the lithium salt. Lithium chloride is dissolved in the low eutectic solvent system as a lithium source to form a low eutectic solution of lithium chloride, which has good solubility and stability, and provides a lithium replenishment environment for waste electrode sheets.

[0044] In some embodiments of the present application, the molar ratio of the choline chloride, urea and lithium chloride is 1: (0.5-5): (0.1-2). Within this range, the best eutectic effect can be achieved. In some embodiments of the present application, in step S2, the heating and heat preservation treatment in the air includes heating to 130°C to 190°C in the air and keeping warm for 4h to 6h. In some embodiments, the heating treatment temperature can be 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or any value between these values, and the heat preservation time can be 4h, 5h, 6h or any value between these values. The purpose of heating is to make the binder molten, so that it flows and migrates between the positive electrode particles, connects the detached particle plates and infiltrates and wraps the particle microcracks on the positive electrode plate, thereby avoiding direct contact with the electrolyte, realizing the reconnection of the binder to the structural failure area, and covering and protecting the microcracks.

[0045] In some embodiments of the present application, in step S3, the heating treatment includes slowly stirring at 50°C to 80°C for 1h to 6h; after the heating treatment, the heated positive electrode plate is taken out, cleaned with ethanol and vacuum dried. In some embodiments, the heating treatment temperature can be 50°C, 60°C, 70°C, 80°C or any value between these values, and the heating time can be 1h, 2h, 3h, 4h, 5h, 6h or any value between these values. By immersing the positive electrode plate of the waste lithium-ion battery in a low eutectic solution and heating and stirring, the lithium replenishment and repair of the positive electrode plate can be achieved under low temperature conditions.

[0046] In some embodiments of the present application, the positive electrode plate of the waste battery includes a positive electrode material, and the positive electrode material includes one or more of a lithium transition metal oxide, a lithium-containing phosphate with an olivine structure, and their respective modified compounds. The lithium transition metal oxide is selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. The lithium-containing phosphate with an olivine structure is selected from one or more of lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their modified compounds.

[0047] 2. Secondary battery

[0048] The repaired positive electrode sheet is used to assemble a new secondary battery, which includes the repaired positive electrode sheet, the negative electrode sheet, a separator stacked between the positive electrode and the negative electrode, and an electrolyte.

[0049] Some embodiments of the present application provide a negative electrode sheet comprising the current collector and a negative electrode active material layer coated on the surface of the current collector. The negative electrode active material layer comprises a negative electrode active material, a conductive agent and a binder, and of course may also include other additives that are beneficial to the electrochemical performance of the negative electrode.

[0050] In some embodiments, the negative electrode active material may be a commonly used negative electrode active material, including but not limited to: graphite, carbon material, silicon-based material, metal oxide, tin-based material. For example, silicon-based composite materials include but are not limited to silicon-carbon composite materials, silicon-metal oxide composite materials, silicon alloy composite materials, wherein the mass content of silicon in the composite material is 1-85wt%. For example, metal oxides include but are not limited to iron oxide, lithium titanate, copper oxide, etc., which are regarded as all metal oxides capable of lithium extraction and storage.

[0051] In some embodiments, the conductive agent can be a commonly used conductive agent, including but not limited to: metal-based materials, carbon-based materials, conductive polymers and mixtures thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, nickel, copper, aluminum or silver. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, acetylene black, Ketjen black, carbon black, carbon fiber or any combination thereof. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0052] In some embodiments, the binder can be a commonly used binder, including but not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, ethylene oxide-containing polymers, carboxylated polyvinyl chloride, polyvinyl pyrrolidone, polyurethane, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin or nylon, etc.

[0053] In some embodiments, the electrolyte includes a lithium salt and a solvent.

[0054] In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalatoborate), or lithium difluorooxalatoborate.

[0055] In some embodiments, the solvent can be selected from one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0056] The secondary battery can be prepared using common methods in the prior art, such as assembling the battery pole pieces into the battery core, and then pouring the electrolyte into the battery core.

[0057] In some embodiments, the preparation method of the secondary battery includes: placing or winding the positive electrode sheet of the present application and the separator together to form an electrode assembly. Then, the electrode assembly is placed in, for example, an aluminum-plastic film, and an electrolyte is injected, followed by vacuum packaging, standing, forming, shaping, and other processes to obtain the secondary battery.

[0058] The electrolyte and the separator used in the present application are not particularly limited and can be prepared using materials, structures and manufacturing methods known in the art.

[0059] In some embodiments, the electrolyte includes a lithium salt and a solvent.

[0060] In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), bistrifluoromethanesulfonyl imide lithium LiN(CF3SO2)2 (LiTFSI), bis(fluorosulfonyl)imide lithium Li(N(SO2F)2)(LiFSI), lithium bis(oxalate borate) LiB(C2O4)2 (LiBOB) or lithium difluorooxalate borate LiBF2(C2O4) (LiDFOB). In some embodiments, the concentration of the lithium salt in the electrolyte is: about 0.5mol / L to 3mol / L, about 0.5mol / L to 2mol / L, or about 0.8mol / L to 1.5mol / L.

[0061] In some embodiments, the solvent can be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0062] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature performance, etc.

[0063] According to some embodiments of the present application, the secondary battery is a lithium metal secondary battery or a sodium metal secondary battery. In some embodiments, the lithium metal secondary battery includes, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

[0064] According to some embodiments of the present application, the secondary battery may include an outer package, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0065] According to some embodiments of the present application, the shape of the secondary battery is not particularly limited, and it can be cylindrical, square, or any other shape.

[0066] In some embodiments, the present application further provides a battery module. The battery module includes the above-mentioned secondary battery. The battery module of the present application uses the above-mentioned secondary battery, and therefore has at least the same advantages as the secondary battery. The number of secondary batteries contained in the battery module of the present application can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0067] In some embodiments, the present application further provides a battery pack, which includes the above-mentioned battery module. The number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0068] 3. Device

[0069] The present application also provides a device, which includes the secondary battery mentioned above.

[0070] In some embodiments, the device includes but is not limited to: electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, etc. In order to meet the device's requirements for high power and high energy density of lithium-ion batteries, a battery pack or battery module may be used.

[0071] In some embodiments, the device may be a tablet computer, a mobile phone, a laptop computer, etc. The device is usually required to be light and thin, and a lithium-ion battery may be used as a power source.

[0072] 4. Embodiment

[0073] Battery performance test

[0074] In an argon-filled glove box, the positive electrode sheets, graphite negative electrode sheets obtained in the examples and comparative examples of the present application and the Cellgard 2400 polypropylene film were assembled into 2032 button-type batteries, and then the electrochemical performance of the batteries was tested at a constant temperature of 25°C.

[0075] Embodiment 1:

[0076] S1, preparation of a low eutectic solvent: 400 g of choline chloride and 340 g of urea were mixed and stirred at 80° C. for about 30 minutes to form a clear colorless liquid, and then 35 g of lithium chloride was added to the solution. The mixture was stirred at 120° C. for 6 hours until the lithium chloride was completely dissolved. The preparation of a low eutectic solution of lithium chloride was completed. In this embodiment, the molar ratio of choline chloride, urea and lithium chloride was 1:1.98:0.29.

[0077] S2, take about 100g of waste ternary lithium-ion battery positive electrode sheet (NCM523), heat it to 170℃ in air, and keep it warm for 5h, so that the organic binder polyvinyl fluoride (PVDF) is molten and flows and migrates between the positive electrode particles, and the positive electrode sheet reinforced with the binder is obtained, so that the binder can reconnect the structural failure area and cover and protect the microcracks.

[0078] S3, immersing the positive electrode sheet reinforced with the binder into a low eutectic solution of lithium chloride, slowly stirring and reacting at 70°C for about 5 hours, taking out the positive electrode sheet, cleaning it with ethanol, and vacuum drying it for 1 hour to obtain the positive electrode sheet after lithium supplementation, and characterizing and testing it.

[0079] Embodiment 2:

[0080] The difference from Example 1 is that in S2, the positive electrode plate used is heated to 130° C. in air and kept warm for 5 hours. Other content parameters are the same as in Example 1.

[0081] Embodiment 3:

[0082] The difference from Example 1 is that in S3, the reaction is slowly stirred at 50°C for about 5 hours, and other content parameters are the same as in Example 1.

[0083] Embodiment 4:

[0084] The difference from Example 1 is that in S3, the reaction is slowly stirred at 70°C for about 1 hour, and other content parameters are the same as in Example 1.

[0085] Comparative Example 1:

[0086] About 100 g of waste ternary lithium-ion battery positive electrode sheets (NCM523) were taken, heated to 170°C in air, and kept warm for 5 hours, so that the organic binder polyvinyl fluoride (PVDF) was molten and flowed and migrated between the positive electrode particles, and the binder-reinforced positive electrode sheets were obtained, which were directly characterized and tested.

[0087] Comparative Example 2:

[0088] 400 g of choline chloride and 340 g of urea were mixed and stirred at 80 ° C for about 30 minutes to form a clear colorless liquid, and then 35 g of lithium chloride was added to the solution, and the stirring was continued at 120 ° C for 6 hours until the lithium chloride was completely dissolved, that is, the low eutectic solution of lithium chloride was prepared. In this embodiment, the molar ratio of choline chloride, urea and lithium chloride is 1:1.98:0.29.

[0089] Take about 100g of the positive electrode sheet (NCM523) of the waste ternary lithium-ion battery, immerse it in a low eutectic solution of lithium chloride, slowly stir and react at 70°C for about 5h, take out the positive electrode sheet, wash it with ethanol, and then vacuum dry it for 1h to obtain the positive electrode sheet after lithium supplementation, and characterize and test it.

[0090] Comparative Example 3

[0091] The difference from Example 1 is that in S3, the reaction is slowly stirred at 25°C for about 5 hours, and other content parameters are the same as in Example 1.

[0092] Comparative Example 4

[0093] About 100 g of waste ternary lithium-ion battery positive electrode (NCM523) was taken and characterized and tested directly without any treatment.

[0094] Test methods:

[0095] 1. ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) element content test:

[0096] Place a certain amount of the sample to be tested in a digestion container, add an acid solution (such as hydrochloric acid, nitric acid or sulfuric acid), seal it, and heat and digest it in a microwave digester or oven. After the digestion is completed, transfer the digestion solution to a volumetric flask and perform the volume adjustment and shake steps. Use ICP-OES equipment to test the trace element content of the digestion solution. For liquid phase samples such as leaching solutions, use ICP-OES equipment to test the trace element content of the digestion solution after dilution.

[0097] 2. Electrochemical test

[0098] The waste positive electrode sheets and commercial new electrode sheets were cut into circular electrode sheets, assembled with standard graphite negative electrode sheets, Cellgard 2400 polypropylene membrane and commercial new electrolyte into 2032 button batteries, and then the electrochemical performance of the batteries was tested at a constant temperature of 25°C. The results are shown in Tables 1 and 2, where TM represents transition metal elements other than lithium.

[0099] Table 1 ICP-OES element measurement results

[0100] Li Ni Co Mn Li / TM Example 1 1.018 0.554 0.151 0.312 1.002 Example 2 0.952 0.546 0.151 0.306 0.949 Example 3 0.973 0.553 0.155 0.311 0.970 Example 4 0.937 0.561 0.154 0.307 0.918 Comparative Example 1 0.815 0.559 0.152 0.313 0.795 Comparative Example 2 0.927 0.542 0.156 0.311 0.919 Comparative Example 3 0.855 0.558 0.145 0.317 0.872 Comparative Example 4 0.815 0.551 0.153 0.312 0.802 Commercial new pole piece 1.022 0.564 0.147 0.305 1.006

[0101] Table 2 Electrochemical test data

[0102]

[0103] According to the ICP-OES electrode material element content data before and after the reaction shown in Table 1, it can be seen that the lithium element content and transition metal content ratio of the waste positive electrode plate in Comparative Example 4 are attenuated and missing to a certain extent compared with the commercial new plate. In the repaired plates shown in Examples 1 to 4, the content ratio of lithium metal to transition metals such as nickel, cobalt, and manganese has been increased and restored to a certain extent compared with the waste positive electrode plate in Comparative Example 4, and is close to the content ratio of the commercial new plate. Specifically, according to different conditions of the embodiments, the recovery of the lithium content and the transition metal ratio is not exactly the same.

[0104] It can be seen from the electrochemical test data shown in Table 2 that the electrochemical performance of the materials after repair under the conditions of different embodiments has been restored to varying degrees. Among them, the electrochemical charge and discharge performance and the first cycle coulomb efficiency of the positive electrode of Example 1 have reached a level basically equal to that of a commercial new electrode.

[0105] The description of the above embodiments is not intended to limit the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments, or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for recycling a lithium battery positive electrode sheet, comprising: S1, providing a eutectic solution, wherein the eutectic solution comprises a quaternary ammonium salt compound, an amine compound and a lithium salt; S2, heating the positive electrode sheet of the lithium battery in air and performing heat preservation treatment to obtain a positive electrode sheet strengthened with a binder; S3, immersing the binder-reinforced positive electrode sheet obtained in S2 into the eutectic solution, and performing a heating treatment to obtain a lithium-supplemented positive electrode sheet.

2. The method according to claim 1, wherein: In S1, raw materials including quaternary ammonium salt compounds and amine compounds are mixed to obtain a mixed solution, and then raw materials including lithium salts are added to the mixed solution to obtain the eutectic solution.

3. The method according to claim 2, wherein: In S1, raw materials including quaternary ammonium salt compounds and amine compounds are first mixed at 50° C. to 90° C. to obtain a mixed solution, and then raw materials including lithium salts are added to the mixed solution and mixed at 100° C. to 130° C. until the lithium salts are completely dissolved, thereby obtaining the low eutectic solution.

4. The method according to any one of claims 1 to 3, wherein: The quaternary ammonium salt compound includes: one or a mixture of choline chloride, choline acetate or acetylcholine; and / or The amine compound includes: urea, ethanolamine, triethanolamine, one or a mixture of several thereof; and / or The lithium salt includes at least one of lithium chloride, lithium bromide, lithium iodide, lithium hydroxide, lithium nitrate, lithium carbonate and lithium perchlorate.

5. The method according to claim 4, wherein: The quaternary ammonium salt compound is choline chloride; and / or The amine compound is urea; and / or The lithium salt is lithium chloride.

6. The method according to claim 5, wherein: The molar ratio of the choline chloride, urea and lithium chloride is 1:(0.5-5):(0.1-2).

7. The method according to claim 1, wherein: In S2, the heating and heat preservation treatment in air includes heating to 130° C. to 190° C. in air and keeping the temperature for 4 h to 6 h.

8. The method according to claim 1, wherein: In S3, the heating treatment includes slowly stirring at 50°C to 80°C for 1h to 6h; after the heating treatment, taking out the heated positive electrode plate, washing it with an organic solvent and vacuum drying it to obtain a lithium-supplemented positive electrode plate.

9. The method according to claim 1, wherein: The positive electrode plate of the lithium battery includes a positive electrode material, and the positive electrode material includes one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds; Furthermore, the lithium transition metal oxide is selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof; The lithium-containing phosphate with olivine structure is selected from one or more of lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and modified compounds thereof.

10. A secondary battery comprising a positive electrode sheet recovered by the method according to any one of claims 1 to 9.

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