Process for recycling and regenerating waste lithium iron phosphate positive electrode material by using specific chelating agent

Abstract

The invention relates to a process for recycling and regenerating a waste lithium iron phosphate positive electrode material by using a specific chelating agent. The method comprises the following steps: carrying out heat treatment on a waste lithium iron phosphate positive electrode material, putting separated waste lithium iron phosphate powder into a ball milling tank, adding organic acid and a chelating agent, and carrying out ball milling; after the ball milling is finished, adding hydrogen peroxide, uniformly stirring and mixing, adjusting the pH value to 2-3 by using nitric acid, and filtering to obtain a filter cake which is iron phosphate; adding saturated sodium carbonate into the filtrate, precipitating, and recovering lithium carbonate; putting the iron phosphate, the lithium carbonate, the iron source, the lithium source and the phosphorus source in the step S3 into a ball mill for ball milling, and performing high-temperature solid-phase sintering after ball milling to obtain a regenerated lithium iron phosphate material; the chelating agent disclosed by the invention is prepared from (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid, 2-mercaptobenzimidazole carboxylic acid, an ethylene boric anhydride pyridine complex and potassium persulfate. The regenerated lithium iron phosphate material prepared by the method has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling of lithium iron phosphate cathode materials, and in particular to a recycling and regeneration preparation process for waste lithium iron phosphate cathode materials using a specific chelating agent. Background Art

[0002] Background Art of a Recycling and Regeneration Preparation Process for Waste Lithium Iron Phosphate Cathode Materials Using a Specific Chelating Agent

[0003] In recent years, with the booming development of the new energy vehicle industry, lithium iron phosphate power batteries have continuously increased their market share due to their advantages such as high safety and low cost. BYD's blade batteries and CATL's CPT technology have further broken through the bottleneck of the relatively low energy density of lithium iron phosphate power batteries, strongly promoting their wide application. However, the current situation of relatively scarce lithium resources in China has become an important factor restricting the sustainable development of the industry. In this context, recycling and reusing the lithium resources in waste lithium-ion batteries is undoubtedly an important strategic measure to alleviate the scarcity of lithium resources.

[0004] Currently, there are already some related patented technologies for recycling waste lithium-ion batteries, which are as follows:

[0005] 1. A Recycling and Regeneration Preparation Process for Waste Lithium Iron Phosphate Cathode Materials Using a Specific Chelating Agent, Chinese Patent CN118183660A: This patent relates to the technical field of recycling waste lithium-ion batteries and discloses a method and application for preparing iron phosphate using a lithium iron phosphate cathode material. The specific method is as follows: First, perform a first acid leaching, oxidation reaction, and first solid-liquid separation on the lithium iron phosphate cathode material to obtain material A; then perform a second acid leaching on material A; then add iron powder to the reaction system of the second acid leaching to obtain acid leaching solution B; subsequently, adjust the pH of acid leaching solution B to 1-3, and add phosphate (phosphate includes phosphopeptide and / or hydroxyphosphopeptide) to acid leaching solution B to obtain a mixed solution C; then add fluoride salt to mixed solution C and perform a complexation reaction to obtain mixed solution D; finally, add hydrogen phosphate and an oxidizing agent to mixed solution D and perform a heating precipitation reaction, first washing, and second solid-liquid separation to obtain material E.

[0006] 2. Recycling and Regeneration Preparation Process of Waste Lithium Iron Phosphate Cathode Material Using Specific Chelating Agent Chinese Patent CN117638288A A recycling and regeneration preparation process of waste lithium iron phosphate cathode material using specific chelating agent: Belonging to the technical field of battery materials, a method for recycling and regenerating waste lithium iron phosphate cathode material is disclosed. In the recycling and regeneration process of the present invention, first, waste lithium iron phosphate is recycled and regenerated to obtain iron oxide and lithium dihydrogen phosphate; then, iron oxide and lithium dihydrogen phosphate react to obtain porous lithium iron phosphate; then, p-nitrochlorobenzene is successively reacted with mono-terminal amino polyethylene glycol and hydrogen bromide and then polymerized and deposited on the surface of porous lithium iron phosphate to obtain polystyrene ethylene-coated lithium iron phosphate; then, the nitro group of polystyrene ethylene-coated lithium iron phosphate is reduced and successively reacted with 4-bromopyridine and zinc acetate to obtain modified porous polystyrene ethylene-coated lithium iron phosphate; finally, the modified porous polystyrene ethylene-coated lithium iron phosphate, polyvinylidene fluoride, and acetylene black are formulated into a positive electrode slurry, which is coated and solidified to obtain a regenerated lithium iron phosphate cathode material.

[0007] 3. Recycling and Regeneration Preparation Process of Waste Lithium Iron Phosphate Cathode Material Using Specific Chelating Agent Chinese Patent CN115583640A A recycling and regeneration preparation process of waste lithium iron phosphate cathode material using specific chelating agent: A method for recycling waste lithium iron phosphate black powder with multiple impurities is disclosed. The steps of the method are as follows: First, the waste lithium iron phosphate black powder is subjected to one-stage oxidation leaching in an inorganic acid and hydrogen peroxide system, and solid-liquid separation is carried out to obtain a first-stage leaching solution and a first-stage leaching residue; then, the first-stage leaching residue is subjected to second-stage low-acid pre-removal of impurities leaching to obtain a second-stage leaching residue, and the second-stage leaching residue is subjected to high-acid leaching to obtain a solution containing Fe and P, and P and Fe are supplemented, and the pH of the solution is controlled to prepare iron phosphate; finally, the first-stage leaching solution obtained in step (1) is subjected to impurity removal by adjusting the pH, and the impurity removal solution is obtained by chemical precipitation to obtain lithium products.

[0008] However, the above patents and existing related technologies have many deficiencies: A large amount of electrolyte waste gas is generated during the recycling process, causing pollution to the atmospheric environment; A large amount of inorganic acids or organic extractants are used during the recycling process, which easily leads to wastewater pollution problems; And the overall process flow is relatively complex, with high requirements for equipment, and at the same time, the added value is low and the cost remains high. These problems need to be solved urgently to achieve the green, efficient and sustainable development of the recycling and utilization of waste lithium-ion batteries. Summary of the Invention

[0009] To solve the above problems, the present invention provides a recycling and regeneration preparation process of waste lithium iron phosphate cathode material using specific chelating agent, and its operation steps are as follows:

[0010] S1: Under the protection of argon, the waste lithium iron phosphate cathode material is heat-treated to separate the waste lithium iron phosphate powder from the current collector;

[0011] S2: Place 15 - 25 parts of the separated waste lithium iron phosphate powder into a ball mill tank, add 30 - 40 parts of organic acid and 0.2 - 2 parts of chelating agent, and conduct ball milling.

[0012] S3: After the ball milling is completed, add 1 - 5 parts of hydrogen peroxide, stir and mix evenly, adjust the pH value to 2 - 3 with nitric acid, and filter. The filter cake is iron phosphate.

[0013] S4: Add 10 - 15 parts of saturated sodium carbonate to the filtrate for precipitation to recover lithium carbonate.

[0014] S5: Weigh 5 - 10 parts of the iron phosphate from S3, 1 - 5 parts of lithium carbonate, 5 - 10 parts of iron source, 10 - 16 parts of lithium source, and 10 - 20 parts of phosphorus source by weight, put them into a ball mill for ball milling, and perform high - temperature solid - state sintering after ball milling to obtain the recycled lithium iron phosphate material.

[0015] The heat treatment temperature is 600 - 900 °C and the time is 40 - 70 min.

[0016] The organic acid is citric acid or oxalic acid.

[0017] The iron source is ferric chloride or ferric nitrate.

[0018] The lithium source is lithium carbonate or lithium hydroxide.

[0019] The phosphorus source includes one of potassium phosphate, sodium phosphate, and magnesium phosphate.

[0020] The ratio of powder to ball is 15 - 20:1, the ball milling speed is 200 - 400 rpm, and the time is 60 - 90 min.

[0021] The temperature of the high - temperature calcination is 500 - 700 °C and the time is 5 - 10 h.

[0022] The preparation method of the chelating agent is as follows:

[0023] After introducing nitrogen into the reaction kettle, add 10 - 20 parts of (9ci)-2-(2 - propenyl)-1 - cyclopentene - 1 - carboxylic acid CAS No.: 90969 - 23 - 6, 6 - 12 parts of 2 - mercaptobenzimidazole carboxylic acid CAS No.: 58089 - 25 - 1, 0.02 - 0.2 parts of ethylene boronic anhydride pyridine complex, 0.5 - 2 parts of potassium persulfate, and 200 - 300 parts of ethanol. Heat up to 60 - 70 °C, stir and react for 100 - 120 minutes, and then distill off the ethanol to obtain the chelating agent.

[0024] Reaction mechanism

[0025] The preparation method of the chelating agent is realized through the thiol-ene click chemical reaction between (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid or vinylboric anhydride pyridine complex and 2-mercaptobenzimidazole carboxylic acid to generate a stable chelating agent; this method is efficient, mild and suitable for large-scale industrial production.

[0026] 2-Mercaptobenzimidazole carboxylic acid provides a thiol functional group in the reaction, undergoes an addition reaction with the olefin double bond of (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid to generate the target chelating agent; the benzimidazole ring structure increases the molecular stability and chelating ability, making it perform excellently in metal ion capture.

[0027] (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid provides the olefin functional group required for the reaction and participates in the thiol-ene click chemical reaction; its cyclic structure and carboxylic acid group improve the selectivity and yield of the reaction, endowing the final product with good water solubility and chemical stability, which is helpful for subsequent applications.

[0028] Technical effects

[0029] A recycling and regeneration preparation process of waste lithium iron phosphate cathode materials using a specific chelating agent according to the present invention has the following remarkable effects compared with the prior art:

[0030] In the molecular structure of the chelating agent prepared by the present invention, the cyclopentene group and the benzimidazole ring are connected by covalent bonds to form a complex structure with multiple ligand sites; these ligand sites can effectively bind to metal ions to form stable chelates, thereby improving the solubility and stability of metal ions. Specific embodiments

[0031] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in combination with examples and comparative examples:

[0032] Using lithium iron phosphate cathode material as the active substance, Super-P as the conductive electrode, and polyvinylidene fluoride as the binder, they are mixed with N-methylpyrrolidone in a ratio of 80:10:10 in sequence and ground to obtain a slurry; the slurry is coated on the current collector aluminum foil, dried at 120 °C under vacuum for 12 h, punched to prepare a positive electrode; using a lithium sheet as the negative electrode, a polypropylene diaphragm, and an electrolyte of 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio 1:1:1), electrochemical performance tests are carried out on a Neware battery test system BTS-3000: charge and discharge experiments are carried out under the condition of a 1C current density to test the initial discharge capacity and the capacity retention rate after 100 cycles; the capacity retention rate = the discharge capacity after 100 cycles / the initial discharge capacity.

[0033] Example 1

[0034] A recycling and regeneration preparation process of waste lithium iron phosphate cathode material using a specific chelating agent, and its operation steps are as follows:

[0035] S1: Under the protection of argon, the waste lithium iron phosphate cathode material is heat-treated to separate the waste lithium iron phosphate powder from the current collector;

[0036] S2: Place 15 g of the separated waste lithium iron phosphate powder in a ball mill tank, add 30 g of organic acid and 0.2 g of chelating agent, and carry out ball milling;

[0037] S3: After the ball milling is completed, add 1 g of hydrogen peroxide, stir and mix evenly, adjust the pH value to 2 with nitric acid, and filter. The filter cake is iron phosphate;

[0038] S4: Add 10 g of saturated sodium carbonate to the filtrate to precipitate and recover lithium carbonate;

[0039] S5: Weigh 5 g of the iron phosphate from S3, 1 g of lithium carbonate, 5 g of iron source, 10 g of lithium source, and 10 g of phosphorus source, put them into a ball mill for ball milling, and carry out high-temperature solid-phase sintering after ball milling to obtain the recycled lithium iron phosphate material.

[0040] The heat treatment temperature is 600 °C and the time is 40 min.

[0041] The organic acid is citric acid.

[0042] The iron source is ferric chloride.

[0043] The lithium source is lithium carbonate.

[0044] The phosphorus source includes potassium phosphate.

[0045] The powder-to-ball ratio is 15:1, the ball milling speed is 200 rpm, and the time is 60 min.

[0046] The temperature of the high-temperature calcination is 500 °C and the time is 5 h.

[0047] The preparation method of the chelating agent is as follows:

[0048] After introducing nitrogen into the reaction kettle, add 10 g of (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid CAS No.: 90969-23-6, 6 g of 2-mercaptobenzimidazole carboxylic acid CAS No.: 58089-25-1, 0.02 g of ethylene boronic anhydride pyridine complex, 0.5 g of potassium persulfate, and 200 g of ethanol. Heat up to 60 °C and stir and react for 100 minutes, then distill off the ethanol to obtain the chelating agent.

[0049] Example 2

[0050] A recycling and regeneration preparation process of waste lithium iron phosphate cathode material using a specific chelating agent, and its operation steps are as follows:

[0051] S1: Under the protection of argon, heat-treat the waste lithium iron phosphate cathode material to separate the waste lithium iron phosphate powder and the current collector;

[0052] S2: Place 18 g of the separated waste lithium iron phosphate powder in a ball mill tank, add 33 g of organic acid and 1 g of chelating agent, and carry out ball milling;

[0053] S3: After the ball milling is completed, add 2 g of hydrogen peroxide, stir and mix evenly, adjust the pH value to 2 with nitric acid, and filter. The filter cake is iron phosphate;

[0054] S4: Add 12 g of saturated sodium carbonate to the filtrate to precipitate and recover lithium carbonate;

[0055] S5: Weigh 6 g of the iron phosphate in S3, 2 g of lithium carbonate, 6 g of iron source, 12 g of lithium source, and 13 g of phosphorus source, put them into a ball mill for ball milling, and after ball milling, carry out high-temperature solid-phase sintering to obtain the recycled lithium iron phosphate material.

[0056] The heat treatment temperature is 700 °C and the time is 50 min.

[0057] The organic acid is citric acid.

[0058] The iron source is ferric chloride.

[0059] The lithium source is lithium carbonate.

[0060] The phosphorus source includes sodium phosphate.

[0061] The ball-to-powder ratio is 16:1, the ball milling speed is 250 rpm, and the time is 70 min.

[0062] The temperature of the high-temperature calcination is 550 °C and the time is 6 h.

[0063] The preparation method of the chelating agent is as follows:

[0064] After introducing nitrogen into the reaction kettle, add 13 g of (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid CAS No.: 90969-23-6, 8 g of 2-mercaptobenzimidazole carboxylic acid CAS No.: 58089-25-1, 0.1 g of ethylene borate pyridine complex, 1 g of potassium persulfate, and 240 g of ethanol. Heat up to 65 °C and stir and react for 105 minutes, then distill off the ethanol to obtain the chelating agent.

[0065] Example 3

[0066] A recycling and regeneration preparation process of waste lithium iron phosphate cathode material using a specific chelating agent, and its operation steps are as follows:

[0067] S1: Under the protection of argon, the waste lithium iron phosphate cathode material is heat-treated to separate the waste lithium iron phosphate powder and the current collector;

[0068] S2: Put 23 g of the separated waste lithium iron phosphate powder into a ball mill tank, add 38 g of organic acid and 1.5 g of chelating agent, and carry out ball milling;

[0069] S3: After the ball milling is completed, add 4 g of hydrogen peroxide, stir and mix evenly, adjust the pH value to 3 with nitric acid, and filter. The filter cake is iron phosphate;

[0070] S4: Add 14 g of saturated sodium carbonate to the filtrate to precipitate and recover lithium carbonate;

[0071] S5: Weigh 9 g of the iron phosphate in S3, 4 g of lithium carbonate, 9 g of iron source, 14 g of lithium source, and 18 g of phosphorus source, put them into a ball mill for ball milling, and after ball milling, carry out high-temperature solid-phase sintering to obtain the recycled lithium iron phosphate material.

[0072] The heat treatment temperature is 800 °C and the time is 60 min.

[0073] The organic acid is oxalic acid.

[0074] The iron source is iron nitrate.

[0075] The lithium source is lithium hydroxide.

[0076] The phosphorus source includes sodium phosphate.

[0077] The ball-to-powder ratio is 18:1, the ball milling speed is 350 rpm, and the time is 80 min.

[0078] The temperature of the high-temperature calcination is 650 °C and the time is 9 h.

[0079] The preparation method of the chelating agent is as follows:

[0080] After introducing nitrogen into the reaction kettle, add 18 g of (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid CAS No.: 90969-23-6, 10 g of 2-mercaptobenzimidazole carboxylic acid CAS No.: 58089-25-1, 0.15 g of ethylene borate pyridine complex, 1.5 g of potassium persulfate, and 280 g of ethanol. Heat up to 65 °C, stir and react for 115 minutes, and then distill off the ethanol to obtain the chelating agent.

[0081] Example 4

[0082] A recycling and regeneration preparation process of waste lithium iron phosphate cathode materials using a specific chelating agent, and its operation steps are as follows:

[0083] S1: Under the protection of argon, the waste lithium iron phosphate cathode materials are heat-treated to separate the waste lithium iron phosphate powder and the current collector;

[0084] S2: Put 25 g of the separated waste lithium iron phosphate powder into a ball milling tank, add 40 g of organic acid and 2 g of chelating agent, and carry out ball milling;

[0085] S3: After the ball milling is completed, add 5 g of hydrogen peroxide, stir and mix evenly, adjust the pH value to 3 with nitric acid, and filter. The filter cake is iron phosphate;

[0086] S4: Add 15 g of saturated sodium carbonate to the filtrate to precipitate and recover lithium carbonate;

[0087] S5: Weigh 10 g of the iron phosphate in S3, 5 g of lithium carbonate, 10 g of iron source, 16 g of lithium source, and 20 g of phosphorus source, put them into a ball mill for ball milling, and carry out high-temperature solid-phase sintering after ball milling to obtain the regenerated lithium iron phosphate material.

[0088] The heat treatment temperature is 900 °C and the time is 70 min.

[0089] The organic acid is oxalic acid.

[0090] The iron source is iron nitrate.

[0091] The lithium source is lithium hydroxide.

[0092] The phosphorus source includes magnesium phosphate.

[0093] The ball-to-powder ratio is 20:1, the ball milling speed is 400 rpm, and the time is 90 min.

[0094] The temperature of the high-temperature calcination is 700 °C and the time is 10 h.

[0095] The preparation method of the chelating agent is as follows:

[0096] After introducing nitrogen into the reaction kettle, add 20 g of (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid CAS No.: 90969-23-6, 12 g of 2-mercaptobenzimidazole carboxylic acid CAS No.: 58089-25-1, 0.2 g of ethylene boronic anhydride pyridine complex, 2 g of potassium persulfate, and 300 g of ethanol. Heat up to 70 °C and stir and react for 120 minutes, then distill off the ethanol to obtain the chelating agent.

[0097] Comparative Example 1

[0098] Do not add the chelating agent, and the others are the same as in Example 1.

[0099] Comparative Example 2

[0100] Without adding (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid, and the others are the same as in Example 1.

[0101] Comparative Example 3

[0102] Without adding 2-mercaptobenzimidazole carboxylic acid, and the others are the same as in Example 1.

[0103] <![CDATA[Initial capacitance / mAh·g -1 > Capacity retention rate / % Example 1 166.3 97.9 Example 2 167.5 98.5 Example 3 168.6 98.8 Example 4 169.8 99.5 Comparative Example 1 139.5 88.8 Comparative Example 2 158.2 93.6 Comparative Example 3 159.7 94.4

[0104] Through the data analysis of the above examples and comparative examples, the regenerated lithium iron phosphate material prepared by the present invention has excellent electrochemical performance.

[0105] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A recycling and regeneration process for waste lithium iron phosphate positive electrode materials using a specific chelating agent, the operating steps of which are: S1: Under the protection of argon, the waste lithium iron phosphate positive electrode material is heat-treated to separate the waste lithium iron phosphate powder and the current collector; S2: placing 15-25 parts of the separated waste lithium iron phosphate powder in a ball mill, adding 30-40 parts of an organic acid and 0.2-2 parts of a chelating agent, and ball milling; S3: After the ball milling is completed, 1-5 parts of hydrogen peroxide are added, stirred and mixed evenly, and the pH value is adjusted to 2-3 with nitric acid, and filtered. The filter cake is iron phosphate; S4: adding 10-15 parts of saturated sodium carbonate to the filtrate, precipitating, and recovering lithium carbonate; S5: According to weight, weigh 5-10 parts of iron phosphate of S3, 1-5 parts of lithium carbonate, 5-10 parts of iron source, 10-16 parts of lithium source, and 10-20 parts of phosphorus source, put them into a ball mill and ball mill them, and then perform high-temperature solid-phase sintering to obtain regenerated lithium iron phosphate material.

2. The process for recycling and regenerating waste lithium iron phosphate cathode materials using a specific chelating agent according to claim 1, characterized in that: The heat treatment temperature is 600-900°C and the time is 40-70 minutes.

3. The process for recycling and regenerating waste lithium iron phosphate cathode materials using a specific chelating agent according to claim 1, characterized in that: The organic acid is citric acid or oxalic acid.

4. The process for recycling and regenerating waste lithium iron phosphate cathode materials using a specific chelating agent according to claim 1, characterized in that: The iron source is ferric chloride or ferric nitrate.

5. The process for recycling and regenerating waste lithium iron phosphate cathode materials using a specific chelating agent according to claim 1, characterized in that: The lithium source is lithium carbonate or lithium hydroxide.

6. The process for recycling and regenerating waste lithium iron phosphate cathode materials using a specific chelating agent according to claim 1, characterized in that: The phosphorus source includes one of potassium phosphate, sodium phosphate and magnesium phosphate.

7. The process for recycling and regenerating waste lithium iron phosphate cathode materials using a specific chelating agent according to claim 1, characterized in that: The ball-to-powder ratio is 15-20:1, the ball milling speed is 200-400 rpm, and the time is 60-90 min.

8. The process for recycling and regenerating waste lithium iron phosphate cathode materials using a specific chelating agent according to claim 1, characterized in that: The high temperature calcination temperature is 500-700°C and the time is 5-10h.

9. The process for recycling and regenerating waste lithium iron phosphate cathode materials using a specific chelating agent according to claim 1, characterized in that: The preparation method of the chelating agent is: After nitrogen is introduced into the reaction kettle, 10-20 parts of (9ci)-2-(2-propenyl)-1-cyclopentene-1-carboxylic acid, 6-12 parts of 2-mercaptobenzimidazole carboxylic acid, 0.02-0.2 parts of ethylene boric anhydride pyridine complex, 0.5-2 parts of potassium persulfate, and 200-300 parts of ethanol are added, the temperature is raised to 60-70° C., the reaction is stirred for 100-120 minutes, and the ethanol is distilled off to obtain the chelating agent.