Method for recycling positive electrode material of waste lithium iron phosphate battery based on organic solvent soaking

Abstract

The invention provides a method for recycling a waste lithium iron phosphate battery positive electrode material based on organic solvent soaking. The method comprises the following steps: mixing waste lithium iron phosphate positive electrode material powder and a crown ether chelating type co-dissolving agent to obtain a leaching solution; hydrogen peroxide is added into the leachate, the pH is adjusted, a diammonium hydrogen phosphate solution is added, and iron phosphate and filtrate containing lithium ions are obtained; adding sodium carbonate into the filtrate containing lithium ions, and adjusting the pH value to obtain lithium carbonate; mixing the iron phosphate with a phosphoric acid solution to obtain purified iron phosphate; and mixing the purified iron phosphate, lithium carbonate and acetylene black to obtain the regenerated lithium iron phosphate positive electrode material. According to the method for recycling the positive electrode material of the waste lithium iron phosphate battery based on soaking of the organic solvent, the leaching rate of the lithium element is effectively increased, the selectivity to other metal ions is low, and the regenerated positive electrode material of the lithium iron phosphate battery has relatively high discharge capacity and good cycling stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium iron phosphate materials, and in particular relates to a method for recovering waste lithium iron phosphate battery positive electrode materials based on organic solvent immersion. Background Art

[0002] With the rapid development of new energy vehicles and the energy storage industry, lithium iron phosphate batteries have gained widespread adoption due to their safety, low cost, and long cycle life. However, as batteries age, a large number of used lithium iron phosphate batteries are facing retirement. Improper disposal of these used batteries not only wastes valuable metal resources like lithium, iron, and phosphorus, but also seriously pollutes the environment with toxic and hazardous substances.

[0003] At present, the recycling methods of waste lithium iron phosphate battery positive electrode materials mainly include pyrometallurgical recycling, wet recycling and biological recycling. Pyrometallurgical recycling is one of the main treatment methods for recycling waste lithium iron phosphate battery positive electrode materials. The invention patent application with publication number CN106785167A discloses a method for recovering lithium from waste lithium battery positive electrode materials. The method involves calcining the waste lithium battery positive electrode materials, separating and recovering the lithium from lithium nickel cobalt manganese oxide by ball milling and water leaching, and then high-temperature roasting the lithium-ion batteries that have undergone simple mechanical crushing, and screening to obtain a fine powder containing metals and metal oxides. Similar high-temperature calcination processes are relatively simple and suitable for large-scale processing. However, the purification process steps during the calcination process are cumbersome, and the energy consumption of high-temperature calcination treatment batteries is high.

[0004] Wet recycling can recover the active substances in the cathode materials of used lithium iron phosphate batteries. Patent application CN107196007A discloses a lithium battery recycling and reuse method. The method involves mechanically crushing the lithium batteries, washing with an organic solvent, separating them through airflow grinding, soaking them in sulfuric acid and hydrogen peroxide solutions, and then using alkaline solution precipitation to recover different ions in batches. This increases the yield of each element and improves the purity of the recovered Co. After the discarded batteries are crushed, they are selectively dissolved using appropriate chemical reagents to separate the metal elements in the leachate. While the hydrometallurgical method offers good process stability and is suitable for small- to medium-scale recycling of used lithium batteries, the process requires repeated use of acid and alkali additives, which poses certain risks to human health and the ecological environment.

[0005] Bioleaching, a type of hydrometallurgy, relies on the metabolites produced by microbial metabolism to transform insoluble cathode materials into soluble metal ion solutions. The metal elements are then recovered through solvent extraction or chemical precipitation. While bioleaching is environmentally friendly, it suffers from long recovery cycles and low efficiency.

[0006] In summary, the existing recycling process for spent lithium iron phosphate battery cathode materials is complex, resulting in the waste of valuable metal resources and the generation of toxic and hazardous substances, which seriously pollutes the environment and limits the development of the spent lithium iron phosphate battery cathode material recycling industry. Therefore, there is an urgent need to develop an efficient, environmentally friendly, and economical method for recycling and repurposing spent lithium iron phosphate battery cathode materials. Summary of the Invention

[0007] In order to solve the above technical problems existing in the prior art, the present invention provides a method for recycling waste lithium iron phosphate battery positive electrode materials based on organic solvent soaking.

[0008] The present invention provides a method for preparing a crown ether chelate dissolution aid for recycling waste lithium iron phosphate battery positive electrode materials through soaking in an organic solvent, comprising the following steps: (1) Mix 0.35-1.51 parts of 4-acrylamidebenzo-18-crown ether, 100-200 parts of dimethyl sulfoxide, 2-5 parts of 2-amino-4-methylsulfonylphenol and 1-3 parts of triethylamine; (2) Heat treatment under an inert atmosphere to form a mixed ligand containing a crown ether chelate structure; (3) After the reaction is completed, the water is removed to obtain a crown ether chelating solubilizing agent; Triethylamine acts as an organic base to deprotonate the amino group of 2-amino-4-methylsulfonylphenol, generating a more nucleophilic amino anion. The amino anion attacks the carbon-carbon double bond of 4-acrylamidebenzo-18-crown ether, forming a carbon anion intermediate. The intermediate takes a proton from the dimethyl sulfoxide solvent or triethylamine conjugate acid to generate a mixed ligand containing an amino addition structure while retaining the 18-crown-6 ring structure. Furthermore, in the crown ether chelate solubilizer system, methylsulfonylphenol and 18-crown-6 form a "crown ether chelate-Li + " and "phenolic hydroxyl / methylsulfone coordinated -Fe 3+ / PO4 3- "Synergistic effect: Crown ethers preferentially chelate Li + , destroying the LiFePO4 lattice and promoting the rapid dissolution of lithium; methylsulfonylphenol coordinates Fe 3+ and PO4 3- , promote the dissolution of FePO4, avoid its residue in the form of precipitation, and finally achieve Li + 、Fe 3+ PO4 3- Dimethyl sulfoxide swells the carbon coating, loosening its structure and facilitating acid penetration.

[0009] Preferably, the mixture is stirred at a temperature of 50-70°C for 1-3 hours until uniform; The heat treatment temperature is 90-100°C, and the heat treatment time is 2-5 h.

[0010] Optionally, the inert atmosphere is argon.

[0011] Optionally, after the reaction is completed, the mixture is cooled and water is removed by adsorbing water through molecular sieves to obtain a crown ether chelating solubilizing agent.

[0012] The invention provides a crown ether chelate dissolution aid prepared by the preparation method.

[0013] The present invention provides a method for recovering waste lithium iron phosphate battery positive electrode materials based on soaking in an organic solvent, using the crown ether chelate dissolution aid, comprising the following steps: (1) Discharging and dismantling waste lithium iron phosphate batteries to obtain waste lithium iron phosphate positive electrode material powder; (2) mixing 12-16 parts of lithium iron phosphate cathode material powder and 0.1-0.5 parts of a crown ether chelate dissolution aid to obtain a leachate; (3) adding 35-45 parts of hydrogen peroxide to the leachate, adjusting the pH value to 2-3, and adding 70-80 parts of diammonium hydrogen phosphate solution to obtain iron phosphate and a filtrate containing lithium ions; (4) adding sodium carbonate to the filtrate containing lithium ions and adjusting the pH value to 10-11 to obtain lithium carbonate; (5) mixing 10-15 parts of the ferric phosphate in step (3) with 60-80 parts of a phosphoric acid solution to obtain purified ferric phosphate; (6) Mix 30-40 parts of purified iron phosphate, 20-30 parts of lithium carbonate and 5-10 parts of acetylene black to obtain a regenerated lithium iron phosphate positive electrode material.

[0014] By using a crown ether chelate dissolving agent and stirring, the lithium, iron, phosphorus and other components in the positive electrode material can be fully dissolved. In the dissolution process, the hydrolysis tendency of the metal ions is reduced to avoid the formation of hydroxide precipitation. At the same time, it has a dispersing and stabilizing effect on the tiny carbon particles produced by the dissolution, preventing them from agglomerating and clogging the filter medium. Hydrogen peroxide is further added to the leachate to oxidize the ferrous ions into ferric ions, which react with phosphate ions to form iron phosphate precipitates, thereby achieving efficient separation of iron phosphate and lithium ion components.

[0015] Preferably, step (1) specifically comprises: discharging the waste lithium iron phosphate battery, then disassembling it to separate the waste lithium iron phosphate positive electrode sheets; soaking 10-20 parts of the waste lithium iron phosphate positive electrode sheets in 60-80 parts of an organic solvent, stirring at 50-60° C. for 2-3 hours, and filtering and drying to obtain lithium iron phosphate positive electrode material powder.

[0016] By soaking and stirring in an organic solvent, the positive electrode material is removed from the aluminum foil, and the lithium iron phosphate positive electrode material powder and aluminum foil are obtained by filtration, thereby achieving efficient stripping of the positive electrode material in waste lithium iron phosphate batteries.

[0017] More preferably, the organic solvent is at least one of dimethyl sulfoxide, N,N-dimethylformamide, acetone, 1,3-dimethyl-2-imidazolidinone, 1-methyl-2-pyrrolidone, and N-methylpyrrolidone.

[0018] Preferably, in step (2), 80-120 parts of sulfuric acid solution are added during mixing, and the mixture is stirred at 80-90° C. for 3-4 hours.

[0019] Further preferably, in step (2), the mass proportion of sulfuric acid in the sulfuric acid solution is 10%-15%.

[0020] Under acidic conditions, mixing and stirring with a crown ether chelate dissolution aid can fully dissolve the lithium, iron, phosphorus and other components in the positive electrode material.

[0021] Preferably, in step (3), the mass proportion of hydrogen peroxide in hydrogen peroxide is 5%-8%.

[0022] Select hydrogen peroxide of the above specifications to oxidize ferrous ions into ferric ions.

[0023] Preferably, in step (3), the mass proportion of diammonium hydrogen phosphate in the diammonium hydrogen phosphate solution is 10%-20%.

[0024] A diammonium hydrogen phosphate solution of the above specifications is selected to react iron ions with phosphate ions to generate iron phosphate precipitate, and then the iron phosphate precipitate and the filtrate containing lithium ions are separated by filtration.

[0025] Optionally, in step (3), 70-80 parts of diammonium hydrogen phosphate solution are added to form iron phosphate precipitate, which is washed with deionized water 3-5 times and dried at 80-90° C. to obtain iron phosphate.

[0026] Optionally, step (4) specifically includes: adding sodium carbonate to the filtrate containing lithium ions, adjusting the pH value to 10-11, filtering to obtain lithium carbonate precipitate, and washing and drying to obtain lithium carbonate.

[0027] Preferably, in step (5), the mass proportion of phosphoric acid in the phosphoric acid solution is 10%-15%.

[0028] Optionally, in step (5), the ferric phosphate precipitate is washed 2-3 times with deionized water and dried at 80-90° C. to obtain purified ferric phosphate.

[0029] Preferably, in step (6), after mixing, 30-40 parts of deionized water are added to form a uniform slurry, and then dried at 100-110°C; After drying, calcination is carried out at a temperature of 600-700°C and a calcination time of 7-10 h.

[0030] The present invention also provides a positive electrode material for a lithium iron phosphate battery prepared according to the method for recovering waste positive electrode materials for lithium iron phosphate batteries by soaking them in an organic solvent.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) High selectivity to promote lithium dissolution: The crown ether chelate dissolution aid prepared by the present invention can effectively improve the leaching rate of lithium elements, and has low selectivity for other metal ions, reducing impurity interference.

[0032] (2) Improve solid-liquid separation performance: Improve the dispersion of carbon impurities, increase filtration flux, and effectively reduce the difficulty of subsequent separation processes.

[0033] (3) The lithium iron phosphate battery cathode material prepared by the present invention has an initial discharge capacity of up to 136.5 mAh g at a rate of 0.2 C. -1 The capacity retention rate after 100 cycles is 99.1%, which shows excellent electrochemical performance. DETAILED DESCRIPTION

[0034] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention object, the following is a detailed description in conjunction with examples and comparative examples: Example 1 (1) A method for preparing a crown ether chelating dissolution aid comprises the following steps: H1: Place 0.35 g of 4-acrylamidebenzo-18-crown ether, 100 g of dimethyl sulfoxide, 2 g of 2-amino-4-methylsulfonylphenol, and 1 g of triethylamine in a reaction vessel and stir at 50 °C for 1 h. H2: Dry nitrogen was introduced and the temperature was raised to 90°C for 2 h to form a mixed ligand containing a crown ether chelate structure; H3: After the reaction is completed, cool the mixture and add molecular sieves to absorb moisture to obtain a crown ether chelating solubilizing agent.

[0035] (2) This embodiment provides a method for recovering waste lithium iron phosphate battery positive electrode materials by soaking in an organic solvent, which specifically includes the following steps: S1 pretreatment: The used lithium iron phosphate batteries were discharged and then disassembled to separate the used lithium iron phosphate positive electrode sheets. 10 g of the positive electrode sheets were immersed in 60 g of dimethyl sulfoxide and stirred at 50°C for 2 h to allow the positive electrode material to fall off the aluminum foil. The lithium iron phosphate positive electrode material powder and aluminum foil were then filtered and dried. S2 component separation and extraction: 12 g of lithium iron phosphate cathode material powder, 80 g of 10% sulfuric acid solution and 0.1 g of crown ether chelate dissolution aid were mixed and stirred at 80 ° C for 3 h to fully dissolve the lithium, iron, phosphorus and other components in the cathode material. The leachate was filtered to obtain the leachate; 35 g of 5% hydrogen peroxide was added to the leachate to oxidize the ferrous ions to ferric ions. The pH of the leachate was then adjusted to 2. 70 g of 10% diammonium hydrogen phosphate solution was added to allow the ferric ions to react with the phosphate ions to form ferric phosphate precipitates. The ferric phosphate precipitates and the filtrate containing lithium ions were separated by filtration. S3 Lithium extraction: Add sodium carbonate solution to the filtrate containing lithium ions, adjust the pH value to 10, and allow the lithium ions to react with carbonate ions to form lithium carbonate precipitate, filter the lithium carbonate precipitate, wash the lithium carbonate precipitate with deionized water three times, and then dry it at 80°C to obtain lithium carbonate; S4 Iron phosphate purification: Wash the iron phosphate precipitate three times with deionized water and then dry it at 80°C. Mix 10 g of the dried iron phosphate with 60 g of a 10% phosphoric acid solution and stir at 60°C for 1 h. Filter the purified iron phosphate precipitate, wash it twice with deionized water, and dry it at 80°C. S5 positive electrode material was re-prepared: 30 g of purified iron phosphate, 20 g of lithium carbonate and 5 g of conductive agent acetylene black were mixed, 30 g of deionized water was added to make a uniform slurry, and then the slurry was dried at 100 ° C, ground, and calcined at high temperature. The high-temperature calcination temperature was 600 ° C and the high-temperature calcination time was 7 h to obtain regenerated lithium iron phosphate positive electrode material.

[0036] (3) Preparation of positive electrode sheets and assembly of batteries: Regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive electrode, and polyvinylidene fluoride is used as the binder. They are mixed with N-methylpyrrolidone in a ratio of 80:10:10 and ground to obtain a slurry; the slurry is coated on the current collector aluminum foil and dried at 120°C in vacuum for 12 h; then the electrode sheet is punched into a positive electrode sheet using a punching machine to obtain the positive electrode; the lithium sheet is used as the negative electrode, the separator is polypropylene, and the electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio is 1:1:1).

[0037] Example 2 (1) A method for preparing a crown ether chelating dissolution aid comprises the following steps: H1: 0.63 g of 4-acrylamidebenzo-18-crown ether, 140 g of dimethyl sulfoxide, 3 g of 2-amino-4-methylsulfonylphenol, and 2 g of triethylamine were placed in a reaction vessel and stirred at 55 °C for 2 h. H2: Dry nitrogen was introduced and the temperature was raised to 95°C for 3 h to form a mixed ligand containing a crown ether chelate structure; H3: After the reaction is completed, cool the mixture and add molecular sieves to absorb moisture to obtain a crown ether chelating solubilizing agent.

[0038] (2) This embodiment provides a method for recovering waste lithium iron phosphate battery positive electrode materials by soaking in an organic solvent, which specifically includes the following steps: S1 pretreatment: The used lithium iron phosphate batteries were discharged and then disassembled to separate the used lithium iron phosphate positive electrode sheets. 13 g of the positive electrode sheets were immersed in 65 g of N,N-dimethylformamide and stirred at 55°C for 2.5 h to allow the positive electrode material to fall off the aluminum foil. The lithium iron phosphate positive electrode material powder and aluminum foil were obtained by filtration and drying. S2 component separation and extraction: 13 g of lithium iron phosphate cathode material powder, 90 g of 12% sulfuric acid solution, and 0.2 g of crown ether chelate dissolution aid were mixed and stirred at 85°C for 3.5 h to fully dissolve the lithium, iron, phosphorus and other components in the cathode material. The leachate was filtered to obtain the leachate. 38 g of 6% hydrogen peroxide was added to the leachate to oxidize the ferrous ions to ferric ions. The pH of the leachate was then adjusted to 2. 73 g of 15% diammonium hydrogen phosphate solution was added to allow the ferric ions to react with the phosphate ions to form ferric phosphate precipitates. The ferric phosphate precipitates and the filtrate containing lithium ions were separated by filtration. S3 Lithium extraction: Add sodium carbonate solution to the filtrate containing lithium ions, adjust the pH value to 10, and allow the lithium ions to react with carbonate ions to form lithium carbonate precipitate, filter the lithium carbonate precipitate, wash the lithium carbonate precipitate with deionized water four times, and then dry it at 85°C to obtain lithium carbonate; S4 Iron phosphate purification: Wash the iron phosphate precipitate four times with deionized water and then dry it at 85°C. Mix 12 g of the dried iron phosphate with 65 g of a 12% phosphoric acid solution and stir at 65°C for 1.5 h. Filter the purified iron phosphate precipitate, wash it twice with deionized water, and dry it at 85°C. S5 positive electrode material was re-prepared: 34 g of purified iron phosphate, 24 g of lithium carbonate and 6 g of conductive agent acetylene black were mixed, 34 g of deionized water was added to make a uniform slurry, and then the slurry was dried at 105 ° C, ground, and calcined at high temperature. The high-temperature calcination temperature was 640 ° C and the high-temperature calcination time was 8 h to obtain regenerated lithium iron phosphate positive electrode material.

[0039] (3) Preparation of positive electrode sheets and assembly of batteries: Regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive electrode, and polyvinylidene fluoride is used as the binder. They are mixed with N-methylpyrrolidone in a ratio of 80:10:10 and ground to obtain a slurry; the slurry is coated on the current collector aluminum foil and dried at 120°C in vacuum for 12 h; then the electrode sheet is punched into a positive electrode sheet using a punching machine to obtain the positive electrode; the lithium sheet is used as the negative electrode, the separator is polypropylene, and the electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio is 1:1:1).

[0040] Example 3 (1) A method for preparing a crown ether chelating dissolution aid comprises the following steps: H1: Place 1.3 g of 4-acrylamidebenzo-18-crown ether, 180 g of dimethyl sulfoxide, 4 g of 2-amino-4-methylsulfonylphenol, and 2 g of triethylamine in a reaction vessel and stir at 65 °C for 2 h. H2: Dry nitrogen was introduced and the temperature was raised to 95°C for 4 h to form a mixed ligand containing a crown ether chelate structure; H3: After the reaction is completed, cool the mixture and add molecular sieves to absorb moisture to obtain a crown ether chelating solubilizing agent.

[0041] (2) This embodiment provides a method for recovering waste lithium iron phosphate battery positive electrode materials by soaking in an organic solvent, which specifically includes the following steps: S1 pretreatment: The used lithium iron phosphate batteries were discharged and then disassembled to separate the used lithium iron phosphate positive electrode sheets. 18 g of the positive electrode sheets were immersed in 75 g of acetone and stirred at 55°C for 2.5 h to allow the positive electrode material to fall off the aluminum foil. The lithium iron phosphate positive electrode material powder and aluminum foil were obtained by filtration and drying. S2 component separation and extraction: 15 g of lithium iron phosphate cathode material powder, 110 g of 14% sulfuric acid solution, and 0.4 g of crown ether chelate dissolution aid were mixed and stirred at 85 ° C for 3.5 h to fully dissolve the lithium, iron, phosphorus and other components in the cathode material. The leachate was filtered to obtain the leachate; 43 g of 7% hydrogen peroxide was added to the leachate to oxidize the ferrous ions to ferric ions. The pH of the leachate was then adjusted to 3. 78 g of 15% diammonium hydrogen phosphate solution was added to allow the ferric ions to react with the phosphate ions to form ferric phosphate precipitates. The ferric phosphate precipitates and the filtrate containing lithium ions were separated by filtration. S3 Lithium extraction: Add sodium carbonate solution to the filtrate containing lithium ions, adjust the pH value to 11, and allow the lithium ions to react with carbonate ions to form lithium carbonate precipitate, filter the lithium carbonate precipitate, wash the lithium carbonate precipitate with deionized water four times, and then dry it at 85°C to obtain lithium carbonate; S4 Iron phosphate purification: Wash the iron phosphate precipitate four times with deionized water and then dry it at 85°C. Mix 14 g of the dried iron phosphate with 75 g of a 14% phosphoric acid solution and stir at 65°C for 1.5 h. Filter the purified iron phosphate precipitate, wash it three times with deionized water, and dry it at 85°C. S5 positive electrode material was re-prepared: 38 g of purified iron phosphate, 28 g of lithium carbonate and 8 g of conductive agent acetylene black were mixed, and 38 g of deionized water was added to make a uniform slurry. The slurry was then dried at 105°C, ground, and calcined at high temperature. The high-temperature calcination temperature was 680°C and the high-temperature calcination time was 9 h to obtain regenerated lithium iron phosphate positive electrode material.

[0042] (3) Preparation of positive electrode sheets and assembly of batteries: Regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive electrode, and polyvinylidene fluoride is used as the binder. They are mixed with N-methylpyrrolidone in a ratio of 80:10:10 and ground to obtain a slurry; the slurry is coated on the current collector aluminum foil and dried at 120°C in vacuum for 12 h; then the electrode sheet is punched into a positive electrode sheet using a punching machine to obtain the positive electrode; the lithium sheet is used as the negative electrode, the separator is polypropylene, and the electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio is 1:1:1).

[0043] Example 4 (1) A method for preparing an aza-conjugated dissolution aid, comprising the following steps: H1: Place 1.51 g of 4-acrylamidebenzo-18-crown ether, 200 g of dimethyl sulfoxide, 5 g of 2-amino-4-methylsulfonylphenol, and 3 g of triethylamine in a reaction vessel and stir at 70 °C for 3 h. H2: Dry nitrogen was introduced and the temperature was raised to 100°C for 5 h to form a mixed ligand containing a crown ether chelate structure; H3: After the reaction is completed, cool the mixture and add molecular sieves to absorb moisture to obtain a crown ether chelating solubilizing agent.

[0044] (2) This embodiment provides a method for recovering waste lithium iron phosphate battery positive electrode materials by soaking in an organic solvent, which specifically includes the following steps: S1 pretreatment: The used lithium iron phosphate batteries were discharged and then disassembled to separate the used lithium iron phosphate positive electrode sheets. 20 g of the positive electrode sheets were immersed in 80 g of N-methylpyrrolidone and stirred at 60°C for 3 h to allow the positive electrode material to fall off the aluminum foil. The lithium iron phosphate positive electrode material powder and aluminum foil were obtained by filtration and drying. S2 component separation and extraction: 16 g of lithium iron phosphate cathode material powder, 120 g of 15% sulfuric acid solution and 0.5 g of crown ether chelate dissolution aid were mixed and stirred at 90 ° C for 4 h to fully dissolve the lithium, iron, phosphorus and other components in the cathode material. The leachate was filtered to obtain the leachate; 45 g of 8% hydrogen peroxide was added to the leachate to oxidize the ferrous ions to ferric ions. The pH of the leachate was then adjusted to 3. 80 g of 20% diammonium hydrogen phosphate solution was added to allow the ferric ions to react with the phosphate ions to form ferric phosphate precipitates. The ferric phosphate precipitates and the filtrate containing lithium ions were separated by filtration. S3 Lithium extraction: Add sodium carbonate solution to the filtrate containing lithium ions, adjust the pH value to 11, and allow the lithium ions to react with carbonate ions to form lithium carbonate precipitate, filter the lithium carbonate precipitate, wash the lithium carbonate precipitate with deionized water 5 times, and then dry it at 90°C to obtain lithium carbonate; S4 Iron phosphate purification: Wash the iron phosphate precipitate with deionized water five times and then dry it at 90°C. Mix 15 g of the dried iron phosphate with 80 g of a 15% phosphoric acid solution and stir at 70°C for 2 h. Filter the purified iron phosphate precipitate, wash it with deionized water three times, and dry it at 90°C. S5 positive electrode material was re-prepared: 40 g of purified iron phosphate, 30 g of lithium carbonate and 10 g of conductive agent acetylene black were mixed, 40 g of deionized water was added to make a uniform slurry, and then the slurry was dried at 110°C, ground, and calcined at high temperature. The high-temperature calcination temperature was 700°C and the high-temperature calcination time was 10 h to obtain regenerated lithium iron phosphate positive electrode material.

[0045] (3) Preparation of positive electrode sheets and assembly of batteries: Regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive electrode, and polyvinylidene fluoride is used as the binder. They are mixed with N-methylpyrrolidone in a ratio of 80:10:10 and ground to obtain a slurry; the slurry is coated on the current collector aluminum foil and dried at 120°C in vacuum for 12 h; then the electrode sheet is punched into a positive electrode sheet using a punching machine to obtain the positive electrode; the lithium sheet is used as the negative electrode, the separator is polypropylene, and the electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio is 1:1:1).

[0046] Comparative Example 1 (1) Comparative Example 1 provides a method for recovering waste lithium iron phosphate battery positive electrode materials by soaking in an organic solvent, in which a crown ether chelate type dissolution aid is not used. The method specifically comprises the following steps: S1 pretreatment: The used lithium iron phosphate batteries were discharged and then disassembled to separate the used lithium iron phosphate positive electrode sheets. 10 g of the positive electrode sheets were immersed in 60 g of dimethyl sulfoxide and stirred at 50°C for 2 h to allow the positive electrode material to fall off the aluminum foil. The lithium iron phosphate positive electrode material powder and aluminum foil were then filtered and dried. S2 component separation and extraction: 12 g of lithium iron phosphate cathode material powder and 80 g of 10% sulfuric acid solution were mixed and stirred at 80°C for 3 h to fully dissolve the lithium, iron, phosphorus and other components in the cathode material. The leachate was filtered to obtain the leachate. 35 g of 5% hydrogen peroxide was added to the leachate to oxidize the ferrous ions to ferric ions. The pH of the leachate was then adjusted to 2. 70 g of 10% diammonium hydrogen phosphate solution was added to allow the ferric ions to react with the phosphate ions to form ferric phosphate precipitates. The ferric phosphate precipitates and the filtrate containing lithium ions were separated by filtration. S3 Lithium extraction: Add sodium carbonate solution to the filtrate containing lithium ions, adjust the pH value to 10, and allow the lithium ions to react with carbonate ions to form lithium carbonate precipitate, filter the lithium carbonate precipitate, wash the lithium carbonate precipitate with deionized water three times, and then dry it at 80°C to obtain lithium carbonate; S4 Iron phosphate purification: Wash the iron phosphate precipitate three times with deionized water and then dry it at 80°C. Mix 10 g of the dried iron phosphate with 60 g of a 10% phosphoric acid solution and stir at 60°C for 1 hour. Filter the purified iron phosphate precipitate, wash it twice with deionized water, and dry it at 80°C. S5 positive electrode material was re-prepared: 30 g of purified iron phosphate, 20 g of lithium carbonate and 5 g of conductive agent acetylene black were mixed, 30 g of deionized water was added to make a uniform slurry, and then the slurry was dried at 100 ° C, ground, and calcined at high temperature. The high-temperature calcination temperature was 600 ° C and the high-temperature calcination time was 7 h to obtain regenerated lithium iron phosphate positive electrode material.

[0047] (2) Preparation of positive electrode sheets and assembly of batteries: 70 g of lithium iron phosphate positive electrode material regenerated in S5, 5 g of acetylene black and 5 g of polyvinylidene fluoride were added to 20 g of N-methylpyrrolidone, mixed and ground evenly, then coated on aluminum foil and dried at 100°C for 3 h; then the electrode sheet was punched into a positive electrode sheet using a punching machine; in a vacuum glove box, the positive electrode sheet, metal lithium negative electrode, electrolyte, and glass fiber separator were assembled into a button-type battery, where the electrolyte was 1 mol / L LiPF6 / EC+DEC+DMC, and the volume ratio was 1:1:1.

[0048] Comparative Example 2 (1) The preparation method of the dissolution aid 1 comprises the following steps: H1: Place 0.35 g of 4-acrylamide benzo-18-crown ether, 100 g of dimethyl sulfoxide, and 1 g of triethylamine in a reaction vessel and stir at 50 °C for 1 h; H2: Dry nitrogen was introduced and the temperature was raised to 90°C for 2 h to form a mixed ligand containing a crown ether chelate structure; H3: After the reaction is completed, cool the mixture and add molecular sieves to absorb moisture to obtain dissolution aid 1.

[0049] (2) Comparative Example 2 provides a method for recovering waste lithium iron phosphate battery positive electrode materials by soaking in an organic solvent, using a dissolving agent 1, which specifically includes the following steps: S1 pretreatment: The used lithium iron phosphate batteries were discharged and then disassembled to separate the used lithium iron phosphate positive electrode sheets. 10 g of the positive electrode sheets were immersed in 60 g of dimethyl sulfoxide and stirred at 50°C for 2 h to allow the positive electrode material to fall off the aluminum foil. The lithium iron phosphate positive electrode material powder and aluminum foil were then filtered and dried. S2 component separation and extraction: 12 g of lithium iron phosphate cathode material powder, 80 g of 10% sulfuric acid solution and 0.1 g of dissolution aid 1 were mixed and stirred at 80°C for 3 h to fully dissolve the lithium, iron, phosphorus and other components in the cathode material. The leachate was filtered to obtain the leachate. 35 g of 5% hydrogen peroxide was added to the leachate to oxidize the ferrous ions to ferric ions. The pH of the leachate was then adjusted to 2. 70 g of 10% diammonium hydrogen phosphate solution was added to allow the ferric ions to react with the phosphate ions to form ferric phosphate precipitates. The ferric phosphate precipitates and the filtrate containing lithium ions were separated by filtration. S3 Lithium extraction: Add sodium carbonate solution to the filtrate containing lithium ions, adjust the pH value to 10, and allow the lithium ions to react with carbonate ions to form lithium carbonate precipitate, filter the lithium carbonate precipitate, wash the lithium carbonate precipitate with deionized water three times, and then dry it at 80°C to obtain lithium carbonate; S4 Iron phosphate purification: Wash the iron phosphate precipitate three times with deionized water and then dry it at 80°C. Mix 10 g of the dried iron phosphate with 60 g of a 10% phosphoric acid solution and stir at 60°C for 1 h. Filter the purified iron phosphate precipitate, wash it twice with deionized water, and dry it at 80°C. S5 positive electrode material was re-prepared: 30 g of purified iron phosphate, 20 g of lithium carbonate and 5 g of conductive agent acetylene black were mixed, 30 g of deionized water was added to make a uniform slurry, and then the slurry was dried at 100 ° C, ground, and calcined at high temperature. The high-temperature calcination temperature was 600 ° C and the high-temperature calcination time was 7 h to obtain regenerated lithium iron phosphate positive electrode material.

[0050] (3) Preparation of positive electrode sheets and assembly of batteries: Regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive electrode, and polyvinylidene fluoride is used as the binder. They are mixed with N-methylpyrrolidone in a ratio of 80:10:10 and ground to obtain a slurry; the slurry is coated on the current collector aluminum foil and dried at 120°C in vacuum for 12 h; then the electrode sheet is punched into a positive electrode sheet using a punching machine to obtain the positive electrode; the lithium sheet is used as the negative electrode, the separator is polypropylene, and the electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio is 1:1:1).

[0051] Comparative Example 3 (1) The preparation method of the dissolution aid 2 comprises the following steps: H1: Place 0.35 g of 4-acrylamidebenzo-18-crown ether, 2 g of 2-amino-4-methylsulfonylphenol, and 1 g of triethylamine in a reaction vessel and stir at 50 °C for 1 h; H2: Dry nitrogen was introduced and the temperature was raised to 90°C for 2 h to form a mixed ligand containing a crown ether chelate structure; H3: After the reaction is completed, cool and add molecular sieves to absorb moisture to obtain dissolution aid 2.

[0052] (2) Comparative Example 3 provides a method for recovering waste lithium iron phosphate battery positive electrode materials by soaking in an organic solvent, using a dissolving agent 2, which specifically includes the following steps: S1 pretreatment: The used lithium iron phosphate batteries were discharged and then disassembled to separate the used lithium iron phosphate positive electrode sheets; 10 g of the positive electrode sheets were immersed in 60 g of dimethyl sulfoxide and stirred at 50 ° C for 2 h to allow the positive electrode material to fall off the aluminum foil, and the lithium iron phosphate positive electrode material powder and aluminum foil were obtained by filtration and drying; S2 component separation and extraction: 12 g of lithium iron phosphate cathode material powder, 80 g of 10% sulfuric acid solution, and 0.1 g of dissolution aid 2 were mixed and stirred at 80°C for 3 h to fully dissolve the lithium, iron, phosphorus and other components in the cathode material. The mixture was filtered to obtain a leachate. 35 g of 5% hydrogen peroxide was added to the leachate to oxidize the ferrous ions to ferric ions. The pH of the leachate was then adjusted to 2. 70 g of 10% diammonium hydrogen phosphate solution was added to allow the ferric ions to react with the phosphate ions to form ferric phosphate precipitates. The ferric phosphate precipitates and the filtrate containing lithium ions were separated by filtration. S3 Lithium extraction: Add sodium carbonate solution to the filtrate containing lithium ions, adjust the pH value to 10, and allow the lithium ions to react with carbonate ions to form lithium carbonate precipitate, filter the lithium carbonate precipitate, wash the lithium carbonate precipitate with deionized water three times, and then dry it at 80°C to obtain lithium carbonate; S4 Iron phosphate purification: Wash the iron phosphate precipitate three times with deionized water and then dry it at 80°C. Mix 10 g of the dried iron phosphate with 60 g of a 10% phosphoric acid solution and stir at 60°C for 1 h. Filter the purified iron phosphate precipitate, wash it twice with deionized water, and dry it at 80°C. S5 positive electrode material was re-prepared: 30 g of purified iron phosphate, 20 g of lithium carbonate and 5 g of conductive agent acetylene black were mixed, 30 g of deionized water was added to make a uniform slurry, and then the slurry was dried at 100 ° C, ground, and calcined at high temperature. The high-temperature calcination temperature was 600 ° C and the high-temperature calcination time was 7 h to obtain regenerated lithium iron phosphate positive electrode material.

[0053] (3) Preparation of positive electrode sheets and assembly of batteries: Regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive electrode, and polyvinylidene fluoride is used as the binder. They are mixed with N-methylpyrrolidone in a ratio of 80:10:10 and ground to obtain a slurry; the slurry is coated on the current collector aluminum foil and dried at 120°C in vacuum for 12 h; then the electrode sheet is punched into a positive electrode sheet using a punching machine to obtain the positive electrode; the lithium sheet is used as the negative electrode, the separator is polypropylene, and the electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio is 1:1:1).

[0054] Test Example 1 Electrochemical performance tests were performed on Examples 1-4 and Comparative Examples 1-3: Electrochemical performance tests were performed on a NEWARE tester: at a 0.2C rate, the initial discharge specific capacity and the capacity retention rate after 100 cycles were tested.

[0055] The test results of Test Example 1 and Test Example 2 are shown in Table 1.

[0056] Table 1

[0057] Through the data analysis of the above examples and comparative examples, the regenerated lithium iron phosphate positive electrode material prepared by the present invention has excellent electrochemical properties.

[0058] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a crown ether chelate dissolution aid, characterized in that: Calculated by mass, comprising the following steps: (1) Mix 0.35-1.51 parts of 4-acrylamidebenzo-18-crown ether, 100-200 parts of dimethyl sulfoxide, 2-5 parts of 2-amino-4-methylsulfonylphenol and 1-3 parts of triethylamine; (2) Heat treatment under an inert atmosphere to form a mixed ligand containing a crown ether chelate structure; (3) After the reaction is completed, the water is removed to obtain a crown ether chelating solubilizing agent.

2. The method for preparing a crown ether chelate dissolution aid according to claim 1, wherein When mixing, stir at a temperature of 50-70°C for 1-3 hours until the mixture is evenly mixed; The heat treatment temperature is 90-100°C, and the heat treatment time is 2-5 h.

3. The crown ether chelate solubilizing agent prepared according to the preparation method of claim 1 or 2.

4. A method for recovering waste lithium iron phosphate battery cathode materials by soaking in an organic solvent, using the crown ether chelate dissolution aid according to claim 3, comprising the following steps, calculated by weight: (1) Discharging and dismantling waste lithium iron phosphate batteries to obtain waste lithium iron phosphate positive electrode material powder; (2) mixing 12-16 parts of lithium iron phosphate cathode material powder and 0.1-0.5 parts of a crown ether chelate dissolution aid to obtain a leachate; (3) adding 35-45 parts of hydrogen peroxide to the leachate, adjusting the pH value to 2-3, and adding 70-80 parts of diammonium hydrogen phosphate solution to obtain iron phosphate and a filtrate containing lithium ions; (4) adding sodium carbonate to the filtrate containing lithium ions and adjusting the pH value to 10-11 to obtain lithium carbonate; (5) mixing 10-15 parts of the ferric phosphate in step (3) with 60-80 parts of a phosphoric acid solution to obtain purified ferric phosphate; (6) Mix 30-40 parts of purified iron phosphate, 20-30 parts of lithium carbonate and 5-10 parts of acetylene black to obtain a regenerated lithium iron phosphate positive electrode material.

5. The method for recovering waste lithium iron phosphate battery positive electrode materials based on organic solvent soaking according to claim 4, characterized in that: The organic solvent is at least one of dimethyl sulfoxide, N,N-dimethylformamide, acetone, 1,3-dimethyl-2-imidazolidinone, 1-methyl-2-pyrrolidone, and N-methylpyrrolidone.

6. The method for recovering waste lithium iron phosphate battery positive electrode materials based on organic solvent soaking according to claim 4, characterized in that: In step (2), 80-120 parts of sulfuric acid solution are added during mixing, and the mixture is stirred at 80-90° C. for 3-4 hours, wherein the mass proportion of sulfuric acid in the sulfuric acid solution is 10%-15%.

7. The method for recovering waste lithium iron phosphate battery positive electrode materials based on organic solvent soaking according to claim 4, characterized in that: In step (3), the mass proportion of hydrogen peroxide in hydrogen peroxide is 5%-8%; The mass proportion of diammonium hydrogen phosphate in the diammonium hydrogen phosphate solution is 10%-20%.

8. The method for recovering waste lithium iron phosphate battery positive electrode materials based on organic solvent soaking according to claim 4, characterized in that: In step (5), the mass proportion of phosphoric acid in the phosphoric acid solution is 10%-15%.

9. The method for recovering waste lithium iron phosphate battery positive electrode materials based on organic solvent soaking according to claim 4, characterized in that: In step (5), the mixture is stirred at 60-70° C. for 1 h-2 h for mixing.

10. The method for recovering waste lithium iron phosphate battery positive electrode materials based on organic solvent soaking according to claim 4, characterized in that: In step (6), after mixing, 30-40 parts of deionized water are added to form a uniform slurry, and then dried at 100-110°C; After drying, calcination is carried out at a temperature of 600-700°C and a calcination time of 7-10 h.

Images