Deep eutectic lithium supplement and method for repairing and regenerating waste lithium ion battery positive electrode material

Abstract

The application belongs to the technical field of comprehensive utilization of waste lithium-ion power battery, and discloses a deep eutectic lithium supplement and a method for repairing and regenerating positive electrode material of waste lithium-ion battery, wherein the deep eutectic lithium supplement is prepared by taking a solid-state reducing organic acid as a hydrogen bond donor and a solid-state lithium source as a hydrogen bond acceptor, mixing the hydrogen bond donor and the hydrogen bond acceptor, and reacting to obtain a deep eutectic melting state system; and the deep eutectic lithium supplement can be used for repairing and regenerating the positive electrode material of the waste lithium-ion battery. The application can prepare a liquid-state deep eutectic lithium supplement by using a solid-state reducing acid and a solid-state lithium source, is green and friendly, can realize self-limiting lithium supplement without strict control of the lithium supplement amount, has low energy consumption in the lithium supplement process, can greatly reduce the cost, and can be used for repairing and regenerating the positive electrode material of the waste lithium-ion battery.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology for the recycling of waste lithium-ion power batteries. More specifically, it relates to a deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials, which can realize the lithium replenishment, repair and regeneration of waste lithium-ion battery cathode materials. Background Technology

[0002] my country's new energy vehicle industry has entered a period of rapid development, with its production and sales volume ranking first in the world in the past five years. Lithium-ion batteries, as the core power system of new energy vehicles, typically have a lifespan of 3-5 years. It is estimated that by 2030, the amount of retired lithium-ion batteries will reach 1.3 million tons. Taking lithium iron phosphate batteries as an example, they account for more than 60% of the total retired batteries. The proportion of other types of lithium-ion batteries (such as ternary lithium batteries and lithium cobalt oxide batteries) is also significant. If a large number of waste batteries are not safely disposed of, they will not only cause enormous harm to the environment and public safety but also result in a waste of resources.

[0003] Currently, domestic and international technologies for the resource recycling of lithium-ion battery electrode materials mainly fall into two categories: one is to recover valuable metals by destroying the cathode structure, i.e., using high temperatures or strong acids to destroy the cathode structure and achieve metal separation and leaching; the other is direct regeneration, i.e., achieving direct regeneration of materials through repair and modification methods. The former typically involves an effective combination of pyrometallurgical and hydrometallurgical processes, and has achieved the commercial recovery of Co, Ni, and Li. These processes usually include dismantling, smelting, acid leaching, chemical precipitation, and extraction separation, finally recovering valuable metals in the form of compounds and using them as precursors to produce new cathode materials. This process is simple to operate, but the recycling cost is high, requiring high-temperature treatment and large amounts of chemical reagents, thus contributing to the greenhouse effect and secondary pollution. Compared to destructive recycling, the method of directly repairing and regenerating waste cathode materials requires less energy, does not require strong acids or alkalis for structural destruction, and restores the structure of the cathode material by adding a certain amount of missing elements. This process is shorter, less polluting, and can bring higher environmental and economic benefits.

[0004] Taking lithium iron phosphate (LFP) batteries as an example, during the charging and discharging process, lithium ions continuously insert and extract, causing a certain degree of change in the structure of the cathode material. Because some lithium ions cannot return to their original structural positions, this leads to lithium deficiency and capacity reduction in the cathode material. Among these, Li vacancy defects and Fe antisite defects are the main reasons for the performance degradation of LFP batteries. Li vacancies not only lead to Fe... 2+ Oxidized to Fe 3+ It also led to some Fe 2+ The migration of vacancies to Li forms a transposition defect, which hinders the Li migration. +The normal migration of lithium iron phosphate (LFP) cathode materials is a common process. Direct regeneration typically involves adding a Li source to the waste LFP cathode material to replenish the missing lithium, followed by structural repair through high-temperature calcination. This often involves direct high-temperature calcination, which is energy-intensive. Due to the uneven and limited solid-phase reaction, the missing lithium amount needs to be pre-detected using instruments like ICP-OES to strictly calculate and control the lithium source content, increasing regeneration costs. Excessive lithium source can also lead to coarse grain structure and decreased electrical performance. Carbon-coated material modification requires high reaction temperatures and results in low graphitization, leading to poor thermal and chemical stability, making the recycling process cumbersome and reducing material usability. Similar situations occur with waste ternary lithium batteries or waste lithium cobalt oxide batteries.

[0005] Therefore, there is an urgent need to develop a new recycling technology for waste lithium-ion battery cathode materials to achieve closed-loop recycling of waste lithium iron phosphate and other battery cathode materials. Summary of the Invention

[0006] To address the shortcomings of existing technologies, such as difficulty in controlling lithium replenishment, high recycling costs, and poor electrical performance of recycled materials, and to meet the need for improvement, this invention aims to provide a deep eutectic lithium replenishment agent and a method for repairing and regenerating waste lithium-ion battery cathode materials. The liquid deep eutectic lithium replenishment agent is prepared using a solid reducing acid and a solid lithium source. This agent is environmentally friendly, achieves self-limiting lithium replenishment without strict control of the replenishment amount, and has low energy consumption, significantly reducing costs. It can be used to repair and regenerate waste lithium-ion battery cathode materials. Taking waste lithium iron phosphate batteries as an example, the lithium iron phosphate cathode materials repaired and regenerated through lithium replenishment exhibit stable cycle performance and high specific capacity, and can be reused to construct lithium iron phosphate batteries, achieving closed-loop regeneration of waste lithium iron phosphate battery cathode materials.

[0007] To achieve the above objectives, according to one aspect of the present invention, a deep eutectic lithium supplement is provided, characterized in that the deep eutectic lithium supplement uses a solid reducing organic acid as a hydrogen bond donor and a solid lithium source as a hydrogen bond acceptor, and obtains a deep eutectic molten system by mixing the hydrogen bond donor and the hydrogen bond acceptor and reacting them.

[0008] As a further preferred embodiment of the present invention, the molar ratio of the reducing organic acid to the lithium source is 0.5 to 4;

[0009] The reaction temperature is 25–150°C, and the reaction time is 0.2–4 h.

[0010] As a further preferred embodiment of the present invention, the pH value of the reducing organic acid is preferably 2 to 5;

[0011] Preferably, the reducing organic acid includes one or more of ascorbic acid, citric acid, tartaric acid, malic acid, and oxalic acid;

[0012] The lithium source includes one or more of lithium carbonate, lithium sulfate, lithium chloride, lithium hydroxide, lithium iodide, and lithium oxalate.

[0013] According to another aspect of the present invention, a method for repairing recycled waste lithium-ion battery cathode materials using a deep eutectic lithium replenishing agent is provided, characterized by comprising the following steps:

[0014] S1: Using solid reducing organic acids as hydrogen bond donors and solid lithium sources as hydrogen bond acceptors, a deep eutectic liquid system is obtained by mixing the hydrogen bond donors and hydrogen bond acceptors and reacting them; this deep eutectic liquid system is the deep eutectic lithium supplement.

[0015] S2: The prepared solid waste lithium-ion battery cathode material is mixed with the deep eutectic lithium replenishing agent to perform lithium replenishment and repair; then a solvent is added to the reaction system for dilution and solid-liquid separation is performed, and the solid material obtained by separation is the waste lithium-ion battery cathode material after lithium replenishment and repair; wherein, the solvent is a polar solvent with a polarity greater than or equal to ethanol;

[0016] S3: After mixing the lithium-repaired waste lithium-ion battery cathode material obtained in step S2 with a carbon source, annealing is performed to obtain lithium-repaired and regenerated lithium-ion battery cathode material.

[0017] As a further preferred embodiment of the present invention, in step S2, the solid waste lithium-ion battery cathode material and the deep eutectic lithium replenishing agent are mixed at a solid-liquid ratio of 10-100:1 by mass.

[0018] The reaction temperature is 50-150℃, and the reaction time is 0.5-3h;

[0019] The reaction is preferably carried out under stirring conditions; stirring is more preferably magnetic stirring, and the stirring speed is 200-500 r / min.

[0020] As a further preferred embodiment of the present invention, the method further includes the step of:

[0021] S4: The liquid system obtained from the solid-liquid separation in step S2 is recycled to obtain a recovered deep eutectic lithium replenishing agent. The recovered deep eutectic lithium replenishing agent can be reused to repair and regenerate waste lithium-ion battery cathode materials.

[0022] Preferably, the recycling process is specifically a distillation process.

[0023] As a further preferred embodiment of the present invention, in step S1, the molar ratio of the reducing organic acid to the lithium source is 0.5 to 4;

[0024] The reaction temperature is 25–150°C, and the reaction time is 0.2–4 h.

[0025] As a further preferred embodiment of the present invention, in step S1, the reducing organic acid includes one or more of ascorbic acid, citric acid, tartaric acid, malic acid and oxalic acid;

[0026] The pH value of the reducing organic acid is preferably 2 to 5;

[0027] The lithium source includes one or more of lithium carbonate, lithium sulfate, lithium chloride, lithium hydroxide, lithium iodide, and lithium oxalate.

[0028] As a further preferred embodiment of the present invention, in step S2, the solid waste lithium-ion battery cathode material is cathode powder obtained by peeling off cathode material obtained by dismantling and separating waste lithium-ion batteries after calcination at 200-500°C.

[0029] Preferably, the waste lithium-ion battery is a waste lithium iron phosphate battery, a waste ternary lithium battery, or a waste lithium cobalt oxide battery.

[0030] As a further preferred embodiment of the present invention, in step S3, the annealing temperature used in the annealing treatment is 600-800°C, and the annealing time is 2-8 hours.

[0031] The carbon source is one or more of sucrose, glucose, and citric acid.

[0032] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0033] (1) This invention utilizes reducing organic acids as hydrogen bond donors and lithium sources as hydrogen bond acceptors. A liquid deep eutectic lithium replenishing agent is obtained by mixing and reacting the two. This lithium replenishing agent is green, environmentally friendly, non-toxic, and harmless. Its application in the repair and regeneration of waste lithium-ion battery cathode materials does not involve strong acids or bases, thus avoiding secondary pollution. Furthermore, this deep eutectic lithium replenishing agent can be synthesized, especially at low temperatures, and the synthesis time is short. The deep eutectic lithium replenishing agent in this invention is a deep eutectic solution, also known as a deep eutectic solvent; it has similar properties to ionic liquids (ILs) and is liquid at room temperature. Eutectic solvents, which consist of a binary system of hydrogen bond donors and hydrogen bond acceptors, have the physical property of a lowered solvent melting point.

[0034] This invention preferably uses reducing organic acids with a pH of 2-5 as hydrogen bond donors to avoid potential damage to the structure of lithium-ion battery cathode materials (e.g., lithium iron phosphate) caused by excessively strong organic acids. Combined with a solid lithium source, the reaction is heated to form a molten state, yielding a deep eutectic solution. Organic acids and lithium sources with low synthesis temperatures and short synthesis times can be selected as preferred solutions. This invention preferably uses ascorbic acid, citric acid, tartaric acid, malic acid, and oxalic acid as reducing organic acids, and lithium carbonate, lithium sulfate, lithium chloride, lithium hydroxide, lithium iodide, and lithium oxalate as lithium sources, all of which feature low synthesis temperatures and short synthesis times.

[0035] (2) Compared with traditional direct solid-state reaction high-temperature calcination for lithium replenishment, the method of the present invention does not require prior determination of the lithium deficiency of the waste lithium-ion battery cathode material to be recycled (that is, the present invention does not require prior determination of the lithium deficiency of the material using sophisticated large-scale instruments such as ICP-OES) and does not require strict control of the lithium source content. Based on the present invention, for the waste lithium-ion battery cathode material to be recycled, the above-mentioned deep eutectic lithium replenishing agent is first used to carry out the lithium replenishment reaction, and then the lithium-replenished waste lithium-ion battery cathode material is calcined. By using the deep eutectic lithium replenishing agent, the lithium replenishment reaction spontaneously stops once the amount of lithium replenished is sufficient, realizing self-limited lithium replenishment and avoiding structural damage caused by excessive lithium replenishment, which affects the electrochemical performance of the material.

[0036] (3) Furthermore, compared to the traditional direct solid-state reaction high-temperature calcination for lithium replenishment, this invention uses a simple, green and environmentally friendly deep eutectic lithium replenishment reagent, which can especially achieve lithium replenishment of waste lithium-ion battery cathode materials under low-temperature and short-time conditions (the temperature of the lithium replenishment reaction can be controlled at 50-150℃ and the reaction time can be controlled at 0.5-3h), without the need for high-temperature conditions during the lithium replenishment stage.

[0037] (4) Taking lithium iron phosphate battery cathode material as an example, compared with waste lithium iron phosphate material, the lithium iron phosphate regenerated by the method of the present invention shows excellent performance improvement. As shown in the following examples, when the lithium iron phosphate cathode material regenerated by lithium replenishment and repair using the method of the present invention is subjected to cycle performance testing, the initial capacity is 158.4 mAh g at a current density of 0.5C. -1 After 200 cycles, it retains 97.22% of its capacity, with a coulombic efficiency approaching 100%. In contrast, under the same conditions, waste lithium iron phosphate cathode material, at a current density of 0.5C, has an initial capacity of 100.9 mAh g⁻¹. -1After 200 cycles, the capacity significantly decreased, with a capacity retention rate of only 88.30%. Compared to discarded lithium iron phosphate cathode materials, the lithium iron phosphate material repaired and regenerated using deep eutectic lithium replenishment agent exhibits stable cycle performance and higher specific capacity, resulting in a significant improvement in the battery's electrochemical performance. In other words, the lithium-ion battery cathode material repaired and regenerated using the method of this invention demonstrates superior electrochemical performance compared to discarded lithium-ion battery cathode materials.

[0038] (4) In addition, the deep eutectic lithium supplementation reagent in this invention can be reused multiple times, which improves the material utilization rate.

[0039] In summary, this invention utilizes a deep eutectic lithium replenishing agent to replenish and regenerate waste lithium-ion battery cathode materials. This shortens the process flow, simplifies the process, reduces costs, and makes it suitable for industrial production. It enables closed-loop recycling of lithium-ion battery cathode materials, laying a solid foundation for the subsequent industrial-scale regeneration of waste lithium-ion batteries. Furthermore, the deep eutectic lithium replenishing agent in this invention is recyclable, improving the utilization rate of reducing agents and lithium sources, and avoiding material waste and secondary pollution. Attached Figure Description

[0040] Figure 1 The images show the XRD patterns of the regenerated lithium iron phosphate cathode material (RLFP, i.e., regenerated LiFePO4) in Example 1 and the waste lithium iron phosphate cathode material (SLFP, i.e., spent LiFePO4) in Comparative Example 2.

[0041] Figure 2 SEM images of the recycled lithium iron phosphate cathode material (RLFP) from Example 1 and the waste lithium iron phosphate cathode material (SLFP) from Comparative Example 2 are shown below; Figure 2 (a) corresponds to ratio 2. Figure 2 (b) in the figure corresponds to Example 1, and the scale bars in the figure all represent 10 μm.

[0042] Figure 3 The graph shows the cycling performance of the recycled lithium iron phosphate cathode material (RLFP) in Example 1 and the waste lithium iron phosphate cathode material (SLFP) in Comparative Example 2 at a current density of 0.5C.

[0043] Figure 4 The graph shows the cycling performance of the recycled lithium cobalt oxide cathode material (RLCO, i.e., regenerated LiCO2) in Example 9 and the waste lithium cobalt oxide cathode material (SLCO, i.e., spent LiCO2) in Comparative Example 3 at a current density of 0.5C.

[0044] Figure 5 Example 10: Regenerated ternary cathode material (RNCM, i.e., regenerated LiNi)x Co y Mn z O2) and Comparative Example 4 waste ternary cathode material (SNCM, i.e., spent LiNi) x Co y Mn z Cyclic performance of O2 at a current density of 0.5C. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention 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 merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0046] The following examples and comparative experiments are conducted using the same batch of discarded lithium iron phosphate batteries as an example. The following examples are mainly carried out according to the following steps:

[0047] S1: Different solid reducing organic acids were selected as hydrogen bond donors, and different lithium sources (such as solid lithium salts) were selected as hydrogen bond acceptors. Deep eutectic lithium replenishing agents were synthesized at different temperatures and times according to different material ratios. Then, waste lithium iron phosphate cathode materials were replenished and repaired under different solid-liquid ratios, reaction temperatures, reaction times, and magnetic stirring speeds.

[0048] S2: Under a protective gas atmosphere, different annealing temperatures and annealing times are used, and a certain amount of carbon source is added to anneal the waste lithium iron phosphate cathode material after lithium replenishment and repair.

[0049] S3: Use the lithium iron phosphate cathode material that has been repaired and regenerated by lithium replenishment for battery assembly and performance testing.

[0050] Example 1

[0051] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0052] (1) Mix citric acid and lithium chloride in a molar ratio of 2:1, place them in an oil bath, and react at 100°C and 350 r / min for 30 min to form a clear and transparent viscous liquid, namely, deep eutectic lithium supplement.

[0053] (2) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) at a solid-liquid ratio of 1 / 20 g / g (mass ratio, the same below), and react at 100°C with magnetic stirring at a speed of 350 r / min for 2 hours.

[0054] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate three times with ultrapure water, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and iron elements by ICP-OES, see Table 1; Ultrapure water was used in this step to facilitate solid-liquid separation (to avoid the deep eutectic lithium supplement being too viscous and affecting the solid-liquid separation effect). Of course, in addition to using ultrapure water for dilution, other polar solvents such as ethanol, DMSO, DMF, etc. can also be used for dilution.

[0055] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0056] (5) Add 10wt% sucrose to the powder obtained by drying in (3), and keep it at 750℃ for 2h under argon protection atmosphere with a heating rate of 5℃ / min to obtain regenerated lithium iron phosphate (RLFP).

[0057] Example 2

[0058] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0059] (1) Mix ascorbic acid and lithium chloride in a molar ratio of 1:1, place them in an oil bath, and react at 150°C and 350 r / min for 1 h to form a clear and transparent viscous liquid, namely, deep eutectic lithium supplement.

[0060] (2) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine it at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) according to the solid-liquid ratio of 1 / 50g / g, and react it at 100°C with magnetic stirring at a speed of 450r / min for 4 hours.

[0061] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate with ultrapure water 3 times, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and iron elements by ICP-OES, see Table 1.

[0062] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0063] (5) Add 10wt% sucrose to the powder obtained by drying in (3), and keep it at 750℃ for 2h under argon protection atmosphere with a heating rate of 5℃ / min to obtain regenerated lithium iron phosphate.

[0064] Example 3

[0065] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0066] (1) Mix citric acid and lithium hydroxide in a molar ratio of 4:1, place them in an oil bath, and react at 120°C and 350 r / min for 1.5 h to form a yellow, fluffy mixture, namely, deep eutectic lithium supplement.

[0067] (2) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine it at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) according to the solid-liquid ratio of 1 / 20g / g, and react it at 100°C with magnetic stirring at a speed of 500r / min for 1 hour.

[0068] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate with ultrapure water 3 times, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and iron elements by ICP-OES, see Table 1.

[0069] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0070] (5) Add 10wt% sucrose to the powder obtained by drying in (3), and keep it at 750℃ for 2h under argon protection atmosphere with a heating rate of 5℃ / min to obtain regenerated lithium iron phosphate.

[0071] Example 4

[0072] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0073] (1) Mix oxalic acid and lithium oxalate in a molar ratio of 0.5:1, place them in an oil bath, and react at 220℃ and 500r / min for 6h to form a clear and transparent viscous liquid, namely, deep eutectic lithium supplement.

[0074] (2) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine it at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) according to the solid-liquid ratio of 1 / 20g / g, and react it at 100°C with magnetic stirring at a speed of 500r / min for 4 hours.

[0075] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate with ultrapure water 3 times, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and iron elements by ICP-OES, see Table 1.

[0076] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0077] (5) Add 10wt% sucrose to the powder obtained by drying in (3), and keep it at 750℃ for 2h under argon protection atmosphere with a heating rate of 5℃ / min to obtain regenerated lithium iron phosphate.

[0078] Example 5

[0079] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0080] (1) Mix malic acid and lithium iodide in a molar ratio of 2:1, place them in an oil bath, and react at 160°C and 500r / min for 5h to form a clear and transparent viscous liquid, namely, deep eutectic lithium supplement.

[0081] (2) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine it at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) at a solid-liquid ratio of 1 / 60 g / g, and react it at 100°C with magnetic stirring at a speed of 300 r / min for 4 hours.

[0082] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate with ultrapure water 3 times, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and iron elements by ICP-OES, see Table 1.

[0083] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0084] (5) Add 10wt% sucrose to the powder obtained by drying in (3), and keep it at 750℃ for 2h under argon protection atmosphere with a heating rate of 5℃ / min to obtain regenerated lithium iron phosphate.

[0085] Example 6

[0086] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0087] (1) Tartaric acid and lithium sulfate are mixed in a molar ratio of 3:1 and placed in an oil bath. The mixture is reacted at 150°C and 400r / min for 6 hours to form a clear and transparent viscous liquid, namely, a deep eutectic lithium supplement.

[0088] (2) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine it at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) according to the solid-liquid ratio of 1 / 50g / g, and react it at 100°C with magnetic stirring at a speed of 350r / min for 4 hours.

[0089] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate with ultrapure water 3 times, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and iron elements by ICP-OES, see Table 1.

[0090] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0091] (5) Add 10wt% sucrose to the powder obtained by drying in (3), and keep it at 750℃ for 2h under argon protection atmosphere with a heating rate of 5℃ / min to obtain regenerated lithium iron phosphate.

[0092] Example 7

[0093] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0094] (1) Mix citric acid and lithium chloride in a molar ratio of 1:4, place them in an oil bath, and react at 100°C and 350 r / min for 30 min to form a clear and transparent viscous liquid, namely, deep eutectic lithium supplement.

[0095] (2) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) according to the solid-liquid ratio of 1 / 20g / g, and react at 100°C with magnetic stirring at a speed of 350r / min for 2 hours.

[0096] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate with ultrapure water 3 times, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and iron elements by ICP-OES, see Table 1.

[0097] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0098] (5) Add 10wt% sucrose to the powder obtained by drying in (3), and keep it at 650℃ for 2h under argon protection atmosphere with a heating rate of 5℃ / min to obtain regenerated lithium iron phosphate (RLFP).

[0099] Example 8

[0100] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0101] (1) The deep eutectic lithium supplement obtained by distillation in Example 1 was reused and placed in an oil bath. It was heated to 100°C and 350r / min for 30 minutes to melt it, and a clear and transparent viscous liquid was obtained again.

[0102] (2) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) according to the solid-liquid ratio of 1 / 20g / g, and react at 100°C with magnetic stirring at a speed of 350r / min for 2 hours.

[0103] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate with ultrapure water 3 times, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and iron elements by ICP-OES, see Table 1.

[0104] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0105] (5) Add 10wt% sucrose to the powder obtained by drying in (3), and keep it at 750℃ for 2h under argon protection atmosphere with a heating rate of 5℃ / min to obtain regenerated lithium iron phosphate (RLFP).

[0106] The deep eutectic lithium replenishing agent in this invention has a good effect on waste lithium iron phosphate battery cathode materials when it is reused 3-5 times.

[0107] Example 9

[0108] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0109] (1) Mix citric acid and lithium chloride in a molar ratio of 2:1, place them in an oil bath, and react at 100°C and 350 r / min for 30 min to form a clear and transparent viscous liquid, namely, deep eutectic lithium supplement.

[0110] (2) Disassemble the waste lithium cobalt oxide battery, separate the positive electrode, place it in a tube furnace, calcine at 450°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) at a solid-liquid ratio of 1 / 20 g / g (mass ratio, the same below), and react at 100°C with magnetic stirring at a speed of 350 r / min for 2 hours.

[0111] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate three times with ultrapure water, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium and cobalt elements by ICP-OES, see Table 2; Ultrapure water was used in this step to facilitate solid-liquid separation (to avoid the deep eutectic lithium supplement being too viscous and affecting the solid-liquid separation effect). Of course, in addition to using ultrapure water for dilution, other polar solvents such as ethanol, DMSO, DMF, etc. can also be used for dilution.

[0112] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0113] (5) The powder obtained by drying in (3) is heated at 850°C for 6 hours under an argon protective atmosphere at a heating rate of 5°C / min to obtain the regenerated lithium cobalt oxide cathode material (RLCO).

[0114] Example 10

[0115] A deep eutectic lithium replenishing agent and a method for repairing and regenerating waste lithium-ion battery cathode materials are described below:

[0116] (1) Mix citric acid and lithium chloride in a molar ratio of 2:1, place them in an oil bath, and react at 100°C and 350 r / min for 30 min to form a clear and transparent viscous liquid, namely, deep eutectic lithium supplement.

[0117] (2) Disassemble the waste ternary lithium battery, separate the positive electrode, place it in a tube furnace, calcine at 350°C for 5 hours, peel off the positive electrode material, and place it in the deep eutectic lithium supplement agent synthesized in (1) at a solid-liquid ratio of 1 / 20 g / g (mass ratio, the same below), and react at 100°C with magnetic stirring at a speed of 350 r / min for 2 hours.

[0118] (3) Add 30 mL of ultrapure water to the mixture obtained in (2), mix well and centrifuge, collect the supernatant, wash the lower precipitate three times with ultrapure water, place it in an oven and dry at 90 °C for 12 h, and determine the content of lithium, nickel, cobalt and manganese by ICP-OES, see Table 3; Ultrapure water was used in this step to facilitate solid-liquid separation (in order to avoid the deep eutectic lithium supplement being too viscous and affecting the solid-liquid separation effect). Of course, in addition to using ultrapure water for dilution, other polar solvents such as ethanol, DMSO, DMF, etc. can also be used for dilution.

[0119] (4) Distill the supernatant obtained in (3) to obtain a reusable deep eutectic lithium supplement.

[0120] (5) The powder obtained by drying in (3) is heated at 800°C for 4 hours under an argon protective atmosphere at a heating rate of 5°C / min to obtain the regenerated ternary cathode material (RNCM).

[0121] Comparative Example 1

[0122] Comparative Example 1 uses waste lithium iron phosphate cathode material that has not undergone deep eutectic lithium replenishment treatment. The process is as follows:

[0123] (1) Disassemble the waste lithium iron phosphate battery, separate the positive electrode, place it in a tube furnace, calcine at 350℃ for 5h, and then peel off the positive electrode material. The lithium and iron content is determined by ICP-OES. Then, lithium carbonate and 10wt% sucrose are added according to the lithium to iron molar ratio of 1.05:1. Under the protection of argon, the temperature is increased at 5℃ / min and held at 750℃ for 2h to obtain regenerated lithium iron phosphate. The lithium and iron content is determined by ICP-OES, as shown in Table 1.

[0124] Comparative Example 2

[0125] Comparative Example 2 is a waste lithium iron phosphate cathode material (SLFP) without any treatment. The lithium and iron content in it was determined by ICP-OES, as shown in Table 1.

[0126] Comparative Example 3

[0127] Comparative Example 3 is untreated waste lithium cobalt oxide cathode material (SLCO). The lithium and cobalt content in it was determined by ICP-OES, as shown in Table 2.

[0128] Comparative Example 4

[0129] Comparative Example 4 is a waste ternary cathode material (SNCM) without any treatment. The contents of lithium, nickel, cobalt and manganese in it were determined by ICP-OES, as shown in Table 3.

[0130] The lithium iron phosphate cathode material repaired and regenerated using a deep eutectic lithium replenishing agent in Example 1 and Comparative Example 2 were used as test objects. XRD and SEM were performed on the repaired and regenerated lithium iron phosphate cathode material and the waste lithium iron phosphate cathode material to observe their crystal structure and microstructure. The test results are shown in [Figure 1]. Figure 1 and Figure 2 The recycled lithium iron phosphate from Example 1 and the waste lithium iron phosphate from Comparative Example 2 were used as cathode materials to assemble batteries, and their electrochemical performance was tested. The test results are shown in [Figure 1]. Figure 3 Specifically:

[0131] Figure 1 The images show the XRD patterns of lithium iron phosphate after lithium replenishment and regeneration in Example 1 and waste lithium iron phosphate in Comparative Example 2. The XRD results show that the structure of the waste lithium iron phosphate cathode material did not change significantly after long cycling. After lithium replenishment and regeneration, the crystallinity of lithium iron phosphate was better and the impurity peaks were reduced.

[0132] Figure 2 (a) is the SEM image of the comparative example 2SLFP. After cycling, the lithium iron phosphate particles are severely aggregated and have uneven coarseness. Figure 2 (b) is a SEM image of RLFP from Example 1. The SEM results show that after RLFP was repaired and regenerated, the particle size became smaller and the distribution became more uniform.

[0133] Figure 3 The electrochemical performance of batteries assembled using SLFP (Example 2) and RLFP (Example 1) as cathode materials is compared. It can be seen that at a current density of 0.5C, the initial capacity of RLFP is 158.4 mAh g⁻¹. -1 After 200 cycles, it retains 97.22% of its capacity, with a coulombic efficiency approaching 100%. In contrast, under the same conditions, waste lithium iron phosphate cathode material, at a current density of 0.5C, has an initial capacity of 100.9 mAh g⁻¹. -1 After 200 cycles, the capacity decayed significantly, with a capacity retention of only 88.30% (the coulombic efficiency was slightly lower than that of Example 1 RLFP). Figure 3 (The coulombic efficiency data of the RLFP in Example 1 are basically the same). Compared with the waste lithium iron phosphate cathode material, the recycled lithium iron phosphate material has stable cycle performance and high specific capacity, and the electrochemical performance of the battery is significantly improved. Figure 4 To compare the electrochemical performance of batteries assembled using SLCO (Example 3) and RLCO (Example 9) as cathode materials, at a current density of 0.5C, the initial capacity of SLCO was 141.1 mAh / g, while the initial capacity of RLCO was increased to 162.6 mAh / g. Figure 5The electrochemical performance of batteries assembled using SNCM (Example 4) and RNCM (Example 10) as cathode materials was measured. At a rate of 0.5C, the initial capacity of SNCM was 162.9 mAh / g, while the initial capacity of RNCM was increased to 173.7 mAh / g.

[0134] The lithium and iron contents in Examples 1, 2, 3, 4, 5, 6, 7, 8 and Comparative Examples 1 and 2 were analyzed by ICP-OES, as shown in Table 1. It can be seen that the lithium to iron molar ratio in the waste lithium iron phosphate cathode material of Comparative Examples 1 and 2 was 0.89:1 (although lithium carbonate was added to the reaction system in the comparative examples at a lithium to iron molar ratio of 1.05:1, the experimental results showed no corresponding lithium replenishment effect, which is speculated to be due to the volatilization of lithium carbonate). After lithium replenishment with the deep eutectic lithium replenishing agent, the lithium to iron molar ratio increased. The lithium to iron molar ratio in Example 1 was 1.04, close to the lithium to iron ratio (1.05:1) in commercial lithium iron phosphate. The lithium to iron molar ratios of the products in other examples also increased. This indicates that the deep eutectic lithium replenishing agent of this invention, which uses reducing organic acids as hydrogen bond donors and lithium sources as hydrogen bond acceptors, can play a role in replenishing and repairing waste lithium iron phosphate.

[0135] In addition, compared with Example 1, Example 7 only changed the molar ratio of citric acid and lithium chloride in step (1). In Example 7, the molar ratio of citric acid and lithium chloride was 1:4, and the lithium source was obviously in excess. However, as shown in Table 1, the lithium and iron molar ratio of the product in Example 7 was the same as that in Example 1, which was 1.04:1. It can be seen that even if the lithium source content is in excess, the reaction will spontaneously stop after the lithium supplementation reaction is completed based on the method of the present invention.

[0136] Tables 2 and 3 show that, in addition to lithium iron phosphate, the deep eutectic lithium replenishing agent in this invention can also be applied to the regeneration of other types of lithium-ion battery cathode materials, such as ternary batteries and lithium cobalt oxide batteries. After the action of the deep eutectic lithium replenishing agent, the lithium-cobalt ratio of waste lithium cobalt oxide is 0.99:1, and the lithium content of waste ternary batteries also increases.

[0137] Table 1 shows the lithium and iron content and lithium-iron molar ratio in the unit mass product of Examples 1-8 and Comparative Examples 1-2.

[0138]

[0139]

[0140] Table 2 shows the lithium and cobalt content and the lithium-cobalt molar ratio in the unit mass product of Example 9 and Comparative Example 3.

[0141] Example 9 39847.65 mg / kg 340257.26 mg / kg 0.99:1 Comparative Example 3 35746.58 mg / kg 339278.95mg / kg 0.88:1

[0142] Table 3 shows the content of lithium, nickel, cobalt, and manganese per unit mass of the product in Example 10 and Comparative Example 4, as well as the molar ratio of lithium, nickel, cobalt, and manganese.

[0143]

[0144] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A deep eutectic lithium replenishing agent for the repair and regeneration of waste lithium-ion battery cathode materials, characterized in that, This deep eutectic lithium supplement uses a solid reducing organic acid as a hydrogen bond donor and a solid lithium source as a hydrogen bond acceptor. The deep eutectic molten state system is obtained by mixing the hydrogen bond donor and the hydrogen bond acceptor and reacting them. The reducing organic acid has a pH value of 2 to 5, which can avoid damaging the structure of the positive electrode material of the lithium-ion battery; the molar ratio of the reducing organic acid to the lithium source is 0.5 to 4. The reducing organic acids include one or more of ascorbic acid, citric acid, tartaric acid, malic acid, and oxalic acid. The lithium source includes one or more of lithium carbonate, lithium sulfate, lithium chloride, lithium hydroxide, lithium iodide, and lithium oxalate.

2. The deep eutectic lithium replenishing agent for the repair and regeneration of waste lithium-ion battery cathode materials as described in claim 1, characterized in that, The reaction temperature is 25~150℃, and the reaction time is 0.2~4 h.

3. The method for repairing and regenerating waste lithium-ion battery cathode materials using a deep eutectic lithium replenishing agent as described in claim 1 or 2, characterized in that, Includes the following steps: S1: Prepare a deep eutectic lithium replenishing agent for the repair and regeneration of waste lithium-ion battery cathode materials as described in claim 1 or 2; S2: The prepared solid waste lithium-ion battery cathode material is mixed with the deep eutectic lithium replenishing agent to perform lithium replenishment and repair; then a solvent is added to the reaction system for dilution and solid-liquid separation is performed, and the solid material obtained by separation is the waste lithium-ion battery cathode material after lithium replenishment and repair; wherein, the solvent is a polar solvent with a polarity greater than or equal to ethanol; S3: After mixing the lithium-repaired waste lithium-ion battery cathode material obtained in step S2 with a carbon source, annealing is performed to obtain lithium-repaired and regenerated lithium-ion battery cathode material.

4. The method as described in claim 3, characterized in that, In step S2, the solid waste lithium-ion battery cathode material and the deep eutectic lithium replenishing agent are mixed at a solid-liquid ratio of 10-100:1 by mass. In step S2, the reaction temperature is 50-150℃ and the reaction time is 0.5-3 h.

5. The method as described in claim 4, characterized in that, In step S2, the reaction is carried out under stirring conditions.

6. The method as described in claim 5, characterized in that, In step S2, the stirring is magnetic stirring, and the stirring speed is 200-500 r / min.

7. The method as described in claim 3, characterized in that, The method further includes the following steps: S4: The liquid system obtained from the solid-liquid separation in step S2 is recycled to obtain a recovered deep eutectic lithium replenishing agent. This recovered deep eutectic lithium replenishing agent can be reused to repair and regenerate waste lithium-ion battery cathode materials.

8. The method as described in claim 7, characterized in that, In step S4, the recovery process is specifically a distillation process.

9. The method as described in claim 3, characterized in that, In step S2, the solid waste lithium-ion battery cathode material is cathode powder obtained by calcining the cathode material separated from the waste lithium-ion battery at 200-500°C and then peeling it off. The waste lithium-ion batteries specifically refer to waste lithium iron phosphate batteries, waste ternary lithium batteries, or waste lithium cobalt oxide batteries.

10. The method as described in claim 3, characterized in that, In step S3, the annealing temperature used in the annealing process is 600~800 ℃, and the annealing time is 2~8 h; The carbon source is one or more of sucrose, glucose, and citric acid.

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