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

Abstract

The application provides a method for recycling waste positive electrode material of lithium iron phosphate battery based on organic solvent soaking, and the method comprises the following steps: mixing waste lithium iron phosphate positive electrode material powder and crown ether chelate type dissolution aid to obtain a leaching solution; adding hydrogen peroxide to the leaching solution, adjusting pH, adding diammonium hydrogen phosphate solution, and obtaining iron phosphate and filtrate containing lithium ions; adding sodium carbonate to the filtrate containing lithium ions, adjusting pH, and obtaining lithium carbonate; mixing the iron phosphate and phosphoric acid solution to obtain purified iron phosphate; and mixing the purified iron phosphate, lithium carbonate and acetylene black to obtain regenerated lithium iron phosphate positive electrode material. The method for recycling waste positive electrode material of lithium iron phosphate battery based on organic solvent soaking can effectively improve the leaching rate of lithium element, has low selectivity to other metal ions, and the regenerated positive electrode material of lithium iron phosphate battery has high discharge capacity and good cycle stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium iron phosphate materials, and particularly relates to a method for recycling positive electrode materials of waste lithium iron phosphate batteries based on organic solvent soaking. BACKGROUND

[0002] With the rapid development of new energy vehicles and energy storage industries, lithium iron phosphate batteries are widely used due to their high safety, low cost, long cycle life and other advantages. However, as the service life of the batteries increases, a large number of waste lithium iron phosphate batteries face retirement. If these waste batteries are not properly treated, not only will the valuable metal resources such as lithium, iron and phosphorus be wasted, but also the toxic and harmful substances contained therein will cause serious pollution to the environment.

[0003] At present, the recycling methods of waste lithium iron phosphate battery positive electrode materials mainly include pyrometallurgical recovery, hydrometallurgical recovery and biological recovery. As one of the main treatment methods for recycling waste lithium iron phosphate battery positive electrode materials, the pyrometallurgical recovery is disclosed in the patent application with the publication number CN106785167A. The lithium in the waste lithium battery positive electrode material is recovered by calcining the waste lithium battery positive electrode material, ball milling and water immersion to separate and recover lithium from nickel-cobalt-manganese lithium, and high-temperature roasting of the lithium ion battery after simple mechanical crushing to obtain fine powder containing metal and metal oxide. The similar high-temperature calcination process is relatively simple and suitable for large-scale treatment. However, the calcination process has complicated steps and high energy consumption for treating the battery at high temperature.

[0004] The hydrometallurgical recovery can recover the effective substances of waste lithium iron phosphate battery positive electrode materials. The patent application with the publication number CN107196007A discloses a lithium battery recycling method. The lithium battery is mechanically crushed, washed with an organic solvent, crushed and separated by an air flow mill, soaked in a sulfuric acid and hydrogen peroxide solution, and then different ions are recovered in batches by using an alkali solution to precipitate, thereby increasing the yield of each element and improving the purity of the recovered Co. The waste battery is crushed, and the metal elements in the leaching solution are selectively dissolved by using appropriate chemical reagents. The hydrometallurgical process has good stability and is suitable for recycling small and medium-sized waste lithium batteries. However, the process method needs to repeatedly use acid and alkali reagents, which is harmful to human health and the ecological environment.

[0005] Biological leaching belongs to a type of hydrometallurgy, which relies on the metabolic products produced by microorganisms to change the insoluble positive electrode material into a soluble metal ion solution, and then recovers the metal elements by solvent extraction or chemical precipitation. Although the biological recovery is green and environmentally friendly, it has a long recovery period and low recovery efficiency.

[0006] In summary, the recovery of waste lithium iron phosphate positive electrode material in the prior art has the problems of complex process, waste of valuable metal resources, generation of toxic and harmful substances, serious pollution to the environment, and limitation of the development of the waste lithium iron phosphate positive electrode material recovery industry. Therefore, it is urgent to develop an efficient, environmentally friendly and economical method for recycling and preparing waste lithium iron phosphate battery positive electrode material. SUMMARY

[0007] To solve the above technical problems in the prior art, the application provides a method for recycling waste lithium iron phosphate battery positive electrode material based on organic solvent soaking.

[0008] The application provides a preparation method of a crown ether chelate type dissolution aid for recycling waste lithium iron phosphate battery positive electrode material based on organic solvent soaking, comprising the following steps:

[0009] (1) uniformly mix 0.35-1.51 parts of 4-acrylamide benzene-18-crown ether, 100-200 parts of dimethyl sulfoxide, 2-5 parts of 2-amino-4-methylsulfonyl phenol and 1-3 parts of triethylamine;

[0010] (2) heat treatment under inert atmosphere to form a mixed ligand containing crown ether chelate structure;

[0011] (3) after the reaction is completed, remove the water to obtain the crown ether chelate type dissolution aid;

[0012] The triethylamine as an organic base deprotonates the amino group of the 2-amino-4-methylsulfonyl phenol to generate a more nucleophilic amino anion, which attacks the carbon-carbon double bond of the 4-acrylamide benzene-18-crown ether to form a carbon anion intermediate, which abstracts a proton from the dimethyl sulfoxide solvent or the triethylamine conjugate acid to generate a mixed ligand containing an amino addition structure, while retaining the 18-crown-6 ring structure. Further, in the crown ether chelate type dissolution aid system, the methylsulfonyl phenol and the 18-crown-6 form a synergistic effect of "crown ether chelate-Li + " and "phenolic hydroxyl / methylsulfonyl ligand-Fe 3+ / PO4 3- ", in which the crown ether preferentially chelates Li + , destroys the LiFePO4 lattice and promotes the rapid dissolution of lithium; the methylsulfonyl phenol coordinates Fe 3+ and PO4 3- , promotes the dissolution of FePO4 and avoids its residue in the form of a precipitate, and finally realizes the synchronous and efficient dissolution of Li + , Fe 3+ and PO4 3- . The dimethyl sulfoxide has a swelling effect on the carbon coating layer, making its structure relaxed and facilitating the penetration of the acid solution.

[0013] Preferably, the mixing is uniform when stirring at a temperature of 50-70℃ for 1-3 h;

[0014] The temperature of the heat treatment is 90-100℃, and the time of the heat treatment is 2-5 h.

[0015] Optionally, the inert atmosphere is argon.

[0016] Optionally, after the reaction is completed, the water is removed by cooling and adsorbing the water by molecular sieves to obtain the crown ether chelate type cosolvent.

[0017] The application provides a crown ether chelate type cosolvent prepared by the preparation method.

[0018] The application provides a method for recycling waste lithium iron phosphate battery positive electrode materials based on organic solvent soaking, and uses the crown ether chelate type cosolvent.

[0019] (1) After the waste lithium iron phosphate battery is discharged and disassembled, waste lithium iron phosphate positive electrode material powder is obtained;

[0020] (2) 12-16 parts of the lithium iron phosphate positive electrode material powder and 0.1-0.5 parts of the crown ether chelate type cosolvent are mixed to obtain a leaching solution;

[0021] (3) 35-45 parts of hydrogen peroxide is added to the leaching solution, the pH value is adjusted to 2-3, 70-80 parts of diammonium hydrogen phosphate solution is added, and a phosphoric acid iron and a lithium ion-containing filtrate are obtained;

[0022] (4) Sodium carbonate is added to the lithium ion-containing filtrate, and the pH value is adjusted to 10-11 to obtain lithium carbonate;

[0023] (5) 10-15 parts of the phosphoric acid iron in step (3) is mixed with 60-80 parts of a phosphoric acid solution to obtain purified phosphoric acid iron;

[0024] (6) 30-40 parts of the purified phosphoric acid iron, 20-30 parts of the lithium carbonate and 5-10 parts of acetylene black are mixed to obtain regenerated lithium iron phosphate positive electrode material.

[0025] By using the crown ether chelate type cosolvent and stirring, lithium, iron, phosphorus and other components in the positive electrode material can be fully dissolved, and in the dissolution process, the hydrolysis trend of metal ions is reduced, and hydroxide precipitates are avoided, and the tiny carbon particles generated in the dissolution process have a dispersion and stabilization effect, preventing agglomeration and blocking of the filter medium, and further adding hydrogen peroxide to the leaching solution can oxidize ferrous ions to iron ions, so that the iron ions react with phosphate ions to generate phosphoric acid iron precipitates, and efficient separation of phosphoric acid iron and lithium ion components is realized.

[0026] Preferably, step (1) specifically comprises: discharging the waste lithium iron phosphate battery, then disassembling and separating out the waste lithium iron phosphate positive plate; soaking 10-20 parts of the waste lithium iron phosphate positive plate in 60-80 parts of the organic solvent, stirring at 50-60℃ for 2-3 h, and obtaining the lithium iron phosphate positive material powder after filtration and drying.

[0027] Through soaking and stirring in the organic solvent, the positive material is detached from the aluminum foil, and the lithium iron phosphate positive material powder and the aluminum foil are obtained by filtration, realizing efficient stripping of the positive material in the waste lithium iron phosphate battery.

[0028] Further 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-methyl pyrrolidone.

[0029] Preferably, in step (2), 80-120 parts of the sulfuric acid solution are added during mixing, and stirring is performed at 80-90℃ for 3-4 h.

[0030] Further preferably, in step (2), the mass fraction of sulfuric acid in the sulfuric acid solution is 10%-15%.

[0031] Under the acidic condition, mixing and stirring with the crown ether chelate type cosolvent can make the lithium, iron, phosphorus and other components in the positive material fully dissolved.

[0032] Preferably, in step (3), the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 5%-8%.

[0033] The above-specified hydrogen peroxide solution is selected to oxidize the ferrous ions to iron ions.

[0034] Preferably, in step (3), the mass fraction of diammonium hydrogen phosphate in the diammonium hydrogen phosphate solution is 10%-20%.

[0035] The above-specified diammonium hydrogen phosphate solution is selected to make the iron ions react with the phosphate ions to generate the iron phosphate precipitate, and then the iron phosphate precipitate and the filtrate containing lithium ions are separated by filtration.

[0036] Optionally, in step (3), 70-80 parts of the diammonium hydrogen phosphate solution are added to form the iron phosphate precipitate, which is washed with deionized water for 3-5 times and dried at 80-90℃ to obtain the iron phosphate.

[0037] Optionally, step (4) specifically comprises: adding sodium carbonate to the filtrate containing lithium ions, adjusting the pH value to 10-11, and obtaining the lithium carbonate precipitate by filtration, and obtaining the lithium carbonate after washing and drying.

[0038] Preferably, in step (5), the mass fraction of phosphoric acid in the phosphoric acid solution is 10%-15%.

[0039] Optionally, in step (5), the iron phosphate precipitate is washed with deionized water for 2-3 times and dried at 80-90℃ to obtain the purified iron phosphate.

[0040] Preferably, in step (6), after mixing, 30-40 parts of deionized water is added to form a uniform slurry, and then dried at 100-110℃;

[0041] After drying, calcination is performed at a temperature of 600-700℃ for 7-10 h.

[0042] The application also provides a lithium iron phosphate battery cathode material prepared by the method.

[0043] Compared with the prior art, the application has the following beneficial effects:

[0044] (1) High selectivity to promote lithium dissolution: The crown ether chelate type dissolution aid prepared by the application can effectively improve the leaching rate of lithium element and has low selectivity to other metal ions, reducing impurity interference.

[0045] (2) Improving the solid-liquid separation performance: improving the dispersion of carbon impurities, increasing the filtration flux, and effectively reducing the difficulty of subsequent separation process.

[0046] (3) The lithium iron phosphate battery cathode material prepared by the application has a first discharge specific capacity of 136.5 mAh·g -1 at 0.2 C rate, and a capacity retention rate of 99.1% after 100 cycles, with excellent electrochemical performance. DETAILED DESCRIPTION

[0047] To further illustrate the technical means and effects adopted by the application to achieve the predetermined invention purpose, the following embodiments and comparative examples are described in detail:

[0048] Example 1

[0049] (1) The preparation method of the crown ether chelate type dissolution aid includes the following steps:

[0050] H1: Put 0.35 g of 4-acrylamide benzene-18-crown ether, 100 g of dimethyl sulfoxide, 2 g of 2-amino-4-methylsulfonyl phenol and 1 g of triethylamine into a reaction kettle, stir at 50℃ for 1 h;

[0051] H2: Dry nitrogen is introduced, and the temperature is raised to 90℃ for 2 h to form a mixed ligand containing a crown ether chelate structure;

[0052] H3: After the reaction is completed, cooling is performed, molecular sieves are added to adsorb moisture, and a crown ether chelate type cosolvent is obtained.

[0053] (2) The method provided in the embodiment for recycling waste lithium iron phosphate battery positive electrode material based on organic solvent soaking comprises the following steps:

[0054] S1: Pretreatment: The waste lithium iron phosphate battery is discharged, then disassembled, and the waste lithium iron phosphate positive electrode sheet is separated out; 10 g of the positive electrode sheet is soaked in 60 g of dimethyl sulfoxide, stirred at 50℃ for 2 h, so that the positive electrode material falls off from the aluminum foil, and the lithium iron phosphate positive electrode material powder and the aluminum foil are obtained by filtration and drying;

[0055] S2: Component separation and extraction: 12 g of the lithium iron phosphate positive electrode material powder, 80 g of a 10% sulfuric acid solution, and 0.1 g of a crown ether chelate type cosolvent are mixed, and stirred at 80℃ for 3 h, so that the lithium, iron, phosphorus and other components in the positive electrode material are fully dissolved, and the leaching solution is obtained by filtration;

[0056] 35 g of a 5% hydrogen peroxide solution is added to the leaching solution to oxidize the ferrous ions to iron ions, then the pH value of the leaching solution is adjusted to 2, 70 g of a 10% diammonium hydrogen phosphate solution is added, so that the iron ions react with the phosphate ions to generate iron phosphate precipitate, and the iron phosphate precipitate and the filtrate containing lithium ions are separated by filtration;

[0057] S3: Lithium element extraction: sodium carbonate solution is added to the filtrate containing lithium ions, and the pH value is adjusted to 10, so that the lithium ions react with the carbonate ions to generate lithium carbonate precipitate, and the lithium carbonate precipitate is obtained by filtration, and then washed with deionized water for 3 times, and dried at 80℃ to obtain lithium carbonate;

[0058] S4: Iron phosphate purification: the iron phosphate precipitate is washed with deionized water for 3 times, and then dried at 80℃; 10 g of the dried iron phosphate and 60 g of a 10% phosphoric acid solution are mixed, stirred at 60℃ for 1 h, and then filtered to obtain the purified iron phosphate precipitate, which is washed with deionized water for 2 times and dried at 80℃;

[0059] S5: Positive electrode material re-preparation: 30 g of the purified iron phosphate, 20 g of lithium carbonate and 5 g of conductive agent acetylene black are mixed, 30 g of deionized water is added to form a uniform slurry, and then the slurry is dried at 100℃, ground, and calcined at high temperature, the high-temperature calcination temperature is 600℃, and the high-temperature calcination time is 7 h, to obtain the regenerated lithium iron phosphate positive electrode material.

[0060] (3) Preparation of the positive electrode sheet and assembly of the battery:

[0061] The regenerated lithium iron phosphate positive electrode material is used as an active substance, Super-P is used as a conductive electrode, and ployvinylidene fluoride is used as a binder, which are mixed and ground in a ratio of 80:10:10 to obtain a slurry; the slurry is coated on a current collector aluminum foil, dried at 120 DEG C for 12 h in a vacuum, and then the electrode sheet is punched into a positive electrode sheet by using a sheet punching machine to obtain the positive electrode; lithium sheet is used as a negative electrode, a separator is polypropylene, and an electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio is 1:1:1).

[0062] Example 2

[0063] (1) A preparation method of the crown ether chelate type solubilizing aid includes the following steps:

[0064] H1: 0.63 g of 4-acrylamide benzene-18-crown ether, 140 g of dimethyl sulfoxide, 3 g of 2-amino-4-methylsulfonyl phenol and 2 g of triethylamine are put into a reaction kettle, stirred at 55 DEG C for 2 h;

[0065] H2: dry nitrogen is introduced, and the temperature is raised to 95 DEG C for 3 h to form a mixed ligand containing a crown ether chelate structure;

[0066] H3: after the reaction is completed, cooling, molecular sieve is added to adsorb moisture, and a crown ether chelate type solubilizing aid is obtained.

[0067] (2) The method provided in the embodiment is a method for recycling a positive electrode material of a waste lithium iron phosphate battery based on organic solvent soaking, and specifically includes the following steps:

[0068] S1: the waste lithium iron phosphate battery is discharged, then disassembled, and the waste lithium iron phosphate positive electrode sheet is separated out; 13 g of the positive electrode sheet is soaked in 65 g of N,N-dimethylformamide, stirred at 55 DEG C for 2.5 h, so that the positive electrode material falls off from the aluminum foil, and the lithium iron phosphate positive electrode material powder and the aluminum foil are obtained by filtering and drying;

[0069] S2: component separation and extraction: 13 g of the lithium iron phosphate positive electrode material powder, 90 g of a 12% sulfuric acid solution and 0.2 g of the crown ether chelate type solubilizing aid are mixed, stirred at 85 DEG C for 3.5 h, so that lithium, iron, phosphorus and other components in the positive electrode material are fully dissolved, and the leaching solution is obtained by filtering;

[0070] 38 g of a 6% hydrogen peroxide solution is added to the leaching solution to oxidize ferrous ions to iron ions, and then the pH value of the leaching solution is adjusted to 2, 73 g of a 15% diammonium hydrogen phosphate solution is added, so that iron ions react with phosphate ions to generate iron phosphate precipitate, and the iron phosphate precipitate and the filtrate containing lithium ions are separated by filtering;

[0071] S3 lithium element extraction: sodium carbonate solution is added to the filtrate containing lithium ions, the pH value is adjusted to 10, lithium ions react with carbonate ions to form lithium carbonate precipitate, and lithium carbonate precipitate is obtained by filtration, and the lithium carbonate precipitate is washed with deionized water 4 times, and then dried at 85℃ to obtain lithium carbonate;

[0072] S4 iron phosphate purification: the iron phosphate precipitate is washed with deionized water 4 times, and then dried at 85℃; 12 g of dried iron phosphate and 65 g of phosphoric acid solution with a mass concentration of 12% are mixed, stirred and reacted at 65℃ for 1.5 h, and then filtered to obtain purified iron phosphate precipitate, which is washed with deionized water twice and dried at 85℃;

[0073] S5 positive electrode material re-preparation: 34 g of purified iron phosphate, 24 g of lithium carbonate and 6 g of conductive agent acetylene black are mixed, 34 g of deionized water is added to form a uniform slurry, and then the slurry is dried at 105℃, ground, and calcined at high temperature, the high-temperature calcination temperature is 640℃, and the high-temperature calcination time is 8 h, to obtain regenerated lithium iron phosphate positive electrode material.

[0074] (3) Preparation of positive electrode sheet and assembly of battery:

[0075] The regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive agent, and the polyvinylidene fluoride is used as the binder. The three are mixed in a ratio of 80:10:10 with N-methyl pyrrolidone and ground to obtain a slurry. The slurry is coated on the current collector aluminum foil, dried in a vacuum at 120℃ for 12 h, and then the electrode sheet is punched into a positive electrode sheet by a sheet punching machine to prepare a positive electrode. 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).

[0076] Example 3

[0077] (1) The preparation method of the crown ether chelating type solubility aid includes the following steps:

[0078] H1: Put 1.3 g of 4-acrylamide benzene-18-crown ether, 180 g of dimethyl sulfoxide, 4 g of 2-amino-4-methylsulfonyl phenol and 2 g of triethylamine into a reaction kettle, stir at 65℃ for 2 h;

[0079] H2: Dry nitrogen is introduced, and the temperature is raised to 95℃ for 4 h to form a mixed ligand containing a crown ether chelating structure;

[0080] H3: After the reaction is completed, cool down, add molecular sieves to adsorb moisture, and obtain a crown ether chelating type solubility aid.

[0081] (2) The method for recycling waste lithium iron phosphate battery positive electrode material based on organic solvent soaking provided in the embodiment specifically comprises the following steps:

[0082] S1 pretreatment: the waste lithium iron phosphate battery is discharged, then disassembled, and the waste lithium iron phosphate positive plate is separated out; 18 g of the positive plate is soaked in 75 g of acetone, stirred at 55℃ for 2.5 h, so that the positive electrode material falls off from the aluminum foil, and the lithium iron phosphate positive electrode material powder and the aluminum foil are obtained by filtration and drying;

[0083] S2 component separation and extraction: 15 g of the lithium iron phosphate positive electrode material powder, 110 g of a 14% mass concentration sulfuric acid solution and 0.4 g of a crown ether chelate type dissolution aid are mixed, and stirred and reacted at 85℃ for 3.5 h, so that the lithium, iron, phosphorus and other components in the positive electrode material are fully dissolved, and the leaching solution is obtained by filtration;

[0084] 43 g of a 7% mass concentration hydrogen peroxide solution is added to the leaching solution, so that the ferrous ions are oxidized into iron ions, then the pH value of the leaching solution is adjusted to 3, 78 g of a 15% mass concentration diammonium hydrogen phosphate solution is added, so that the iron ions react with the phosphate ions to generate iron phosphate precipitate, and the iron phosphate precipitate and the filtrate containing lithium ions are separated by filtration;

[0085] S3 lithium element extraction: sodium carbonate solution is added to the filtrate containing lithium ions, and the pH value is adjusted to 11, so that the lithium ions react with the carbonate ions to generate lithium carbonate precipitate, and the lithium carbonate precipitate is obtained by filtration, and then washed with deionized water for 4 times, and dried at 85℃ to obtain lithium carbonate;

[0086] S4 iron phosphate purification: the iron phosphate precipitate is washed with deionized water for 4 times, and then dried at 85℃; 14 g of the dried iron phosphate and 75 g of a 14% mass concentration phosphoric acid solution are mixed, stirred and reacted at 65℃ for 1.5 h, and the purified iron phosphate precipitate is obtained by filtration, and then washed with deionized water for 3 times and dried at 85℃;

[0087] S5 positive electrode material re-preparation: 38 g of the purified iron phosphate, 28 g of lithium carbonate and 8 g of conductive agent acetylene black are mixed, 38 g of deionized water is added to form a uniform slurry, and then the slurry is dried at 105℃, ground, and calcined at high temperature, the high-temperature calcination temperature is 680℃, and the high-temperature calcination time is 9 h, to obtain regenerated lithium iron phosphate positive electrode material.

[0088] (3) Preparation of positive plate and assembly of battery:

[0089] The regenerated lithium iron phosphate positive electrode material is used as an active substance, Super-P is used as a conductive agent, and ployvinylidene fluoride is used as a binder, which are mixed and ground in a ratio of 80:10:10 to obtain a slurry; the slurry is coated on an aluminum foil current collector, dried at 120 DEG C for 12 hours in a vacuum, and then punched into a positive electrode sheet by using a sheet punching machine to obtain a positive electrode; lithium is used as a negative electrode, a separator is polypropylene, and an electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (volume ratio of 1:1:1).

[0090] Example 4

[0091] (1) The preparation method of the nitrogen-containing conjugated cosolvent includes the following steps:

[0092] H1: 1.51 g of 4-acrylamide benzene-18-crown ether, 200 g of dimethyl sulfoxide, 5 g of 2-amino-4-methylsulfonyl phenol, and 3 g of triethylamine are put into a reaction kettle, stirred at 70 DEG C for 3 hours;

[0093] H2: dry nitrogen is introduced, and the temperature is raised to 100 DEG C for 5 hours to form a mixed ligand containing a crown ether chelate structure;

[0094] H3: after the reaction is completed, cooling is performed, and molecular sieves are added to adsorb moisture to obtain a crown ether chelate type cosolvent.

[0095] (2) The method for recycling a positive electrode material of a waste lithium iron phosphate battery based on organic solvent soaking provided in this embodiment includes the following steps:

[0096] S1: the waste lithium iron phosphate battery is discharged, then disassembled, and the waste lithium iron phosphate positive electrode sheet is separated out; 20 g of the positive electrode sheet is soaked in 80 g of N-methyl pyrrolidone, stirred at 60 DEG C for 3 hours to make the positive electrode material fall off from the aluminum foil, and then filtered and dried to obtain lithium iron phosphate positive electrode material powder and aluminum foil;

[0097] S2: component separation and extraction: 16 g of the lithium iron phosphate positive electrode material powder, 120 g of a 15% sulfuric acid solution, and 0.5 g of the crown ether chelate type cosolvent are mixed, stirred at 90 DEG C for 4 hours to make lithium, iron, phosphorus, and other components in the positive electrode material fully dissolved, and then filtered to obtain a leaching solution;

[0098] 45 g of an 8% hydrogen peroxide solution is added to the leaching solution to oxidize ferrous ions to iron ions, then the pH value of the leaching solution is adjusted to 3, 80 g of a 20% diammonium hydrogen phosphate solution is added to make the iron ions react with phosphate ions to generate iron phosphate precipitate, and then the iron phosphate precipitate and a filtrate containing lithium ions are separated by filtration;

[0099] S3 lithium element extraction: a sodium carbonate solution is added to the filtrate containing lithium ions, the pH value is adjusted to 11, lithium ions react with carbonate ions to form lithium carbonate precipitate, and lithium carbonate precipitate is obtained by filtration, and the lithium carbonate precipitate is washed with deionized water for 5 times, and then dried at 90°C to obtain lithium carbonate;

[0100] S4 iron phosphate purification: the iron phosphate precipitate is washed with deionized water for 5 times, and then dried at 90°C; 15 g of dried iron phosphate and 80 g of 15% mass concentration phosphoric acid solution are mixed, stirred and reacted at 70°C for 2 h, and then filtered to obtain purified iron phosphate precipitate, which is washed with deionized water for 3 times and dried at 90°C;

[0101] S5 positive electrode material re-preparation: 40 g of purified iron phosphate, 30 g of lithium carbonate and 10 g of conductive agent acetylene black are mixed, 40 g of deionized water is added to form a uniform slurry, and then the slurry is dried at 110°C, ground, and calcined at high temperature, the temperature of high-temperature calcination is 700°C, and the time of high-temperature calcination is 10 h, to obtain regenerated lithium iron phosphate positive electrode material.

[0102] (3) Preparation of positive electrode sheet and assembly of battery:

[0103] The regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive agent, and the polyvinylidene fluoride is used as the binder, which are mixed and ground in the ratio of 80:10:10 with N-methyl pyrrolidone to obtain a slurry; the slurry is coated on the current collector aluminum foil, dried at 120°C under vacuum for 12 h, and then the electrode sheet is punched into a positive electrode sheet by using a sheet punching machine to prepare a positive electrode; 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).

[0104] Comparative Example 1

[0105] (1) A method for recycling waste lithium iron phosphate battery positive electrode material based on organic solvent soaking provided in Comparative Example 1 does not use crown ether chelating type solubilizing agent, which comprises the following steps:

[0106] S1 Pretreatment: the waste lithium iron phosphate battery is discharged, then disassembled, and the waste lithium iron phosphate positive electrode sheet is separated out; 10 g of the positive electrode sheet is soaked in 60 g of dimethyl sulfoxide, stirred at 50°C for 2 h, so that the positive electrode material falls off from the aluminum foil, and then filtered and dried to obtain lithium iron phosphate positive electrode material powder and aluminum foil;

[0107] S2 Component separation and extraction: 12 g of lithium iron phosphate positive electrode material powder and 80 g of 10% mass concentration sulfuric acid solution are mixed, stirred and reacted at 80°C for 3 h, so that lithium, iron, phosphorus and other components in the positive electrode material are fully dissolved, and then filtered to obtain a leaching solution;

[0108] To the leaching solution, 35 g of 5% mass concentration hydrogen peroxide solution was added to oxidize ferrous ions to ferric ions, and then the pH value of the leaching solution was adjusted to 2, and 70 g of 10% mass concentration diammonium hydrogen phosphate solution was added to make ferric ions react with phosphate ions to generate ferric phosphate precipitate, and the filtrate containing lithium ions was separated by filtration;

[0109] S3: Lithium element extraction: sodium carbonate solution was added to the filtrate containing lithium ions, and the pH value was adjusted to 10 to make lithium ions react with carbonate ions to generate lithium carbonate precipitate, and the lithium carbonate precipitate was obtained by filtration, and the lithium carbonate precipitate was washed with deionized water for 3 times, and then dried at 80°C to obtain lithium carbonate;

[0110] S4: Ferric phosphate purification: the ferric phosphate precipitate was washed with deionized water for 3 times, and then dried at 80°C; 10 g of dried ferric phosphate and 60 g of 10% mass concentration phosphoric acid solution were mixed, stirred at 60°C for 1 hour, filtered to obtain purified ferric phosphate precipitate, and then washed with deionized water for 2 times and dried at 80°C;

[0111] S5: Positive electrode material re-preparation: 30 g of purified ferric phosphate, 20 g of lithium carbonate and 5 g of conductive agent acetylene black were mixed, 30 g of deionized water was added to form a uniform slurry, and then the slurry was dried at 100°C, ground, and calcined at high temperature, the temperature of high-temperature calcination was 600°C, and the time of high-temperature calcination was 7 h, to obtain regenerated lithium iron phosphate positive electrode material.

[0112] (2) Preparation of positive electrode sheet and assembly of battery:

[0113] 70 g of regenerated lithium iron phosphate positive electrode material in S5, 5 g of acetylene black and 5 g of polyvinylidene fluoride were added into 20 g of N-methyl pyrrolidone and mixed and ground uniformly, and then coated on an aluminum foil and dried at 100°C for 3 h; then the electrode sheet was punched into a positive electrode sheet by using a sheet punching machine; in a vacuum glove box, the positive electrode sheet, a metal lithium negative electrode, an electrolyte and a glass fiber separator were assembled into a button type battery, wherein the electrolyte was 1 mol / L LiPF6 / EC+DEC+DMC with a volume ratio of 1:1:1.

[0114] Comparative Example 2

[0115] (1) Preparation method of the dissolution aid 1, comprising the following steps:

[0116] H1: 0.35 g of 4-acrylamide benzene-18-crown ether, 100 g of dimethyl sulfoxide and 1 g of triethylamine were put into a reaction kettle, stirred at 50°C for 1 h;

[0117] 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;

[0118] H3: after the reaction was completed, cooling was performed, and molecular sieves were added to adsorb moisture to obtain the solubility aid 1.

[0119] (2) The method for recycling the positive electrode material of the waste lithium iron phosphate battery based on organic solvent soaking provided by Comparative Example 2 uses the solubility aid 1, and specifically includes the following steps:

[0120] S1: pretreatment: the waste lithium iron phosphate battery was discharged, then disassembled, and the waste lithium iron phosphate positive electrode sheet was separated; 10 g of the positive electrode sheet was soaked in 60 g of dimethyl sulfoxide, stirred at 50°C for 2 h, so that the positive electrode material was separated from the aluminum foil, and the lithium iron phosphate positive electrode material powder and the aluminum foil were obtained by filtration and drying;

[0121] S2: component separation and extraction: 12 g of the lithium iron phosphate positive electrode material powder, 80 g of a 10% sulfuric acid solution, and 0.1 g of the solubility aid 1 were mixed, stirred at 80°C for 3 h, so that the lithium, iron, and phosphorus components in the positive electrode material were fully dissolved, and the leaching solution was obtained by filtration;

[0122] 35 g of a 5% hydrogen peroxide solution was added to the leaching solution to oxidize the ferrous ions to ferric ions, then the pH value of the leaching solution was adjusted to 2, 70 g of a 10% diammonium hydrogen phosphate solution was added, so that the ferric ions reacted with the phosphate ions to form a ferric phosphate precipitate, and the ferric phosphate precipitate and the filtrate containing lithium ions were separated by filtration;

[0123] S3: lithium element extraction: sodium carbonate solution was added to the filtrate containing lithium ions, and the pH value was adjusted to 10, so that the lithium ions reacted with the carbonate ions to form lithium carbonate precipitate, and the lithium carbonate precipitate was obtained by filtration, and then washed with deionized water for 3 times, and dried at 80°C to obtain lithium carbonate;

[0124] S4: ferric phosphate purification: the ferric phosphate precipitate was washed with deionized water for 3 times, and then dried at 80°C; 10 g of the dried ferric phosphate and 60 g of a 10% phosphoric acid solution were mixed, stirred at 60°C for 1 h, and then filtered to obtain the purified ferric phosphate precipitate, which was washed with deionized water for 2 times and dried at 80°C;

[0125] S5: positive electrode material re-preparation: 30 g of the purified ferric phosphate, 20 g of lithium carbonate, and 5 g of conductive agent acetylene black were mixed, 30 g of deionized water was added to form a uniform slurry, and then the slurry was dried at 100°C, ground, and calcined at high temperature, the temperature of the high-temperature calcination was 600°C, and the time of the high-temperature calcination was 7 h, to obtain the regenerated lithium iron phosphate positive electrode material.

[0126] (3) Preparation of positive electrode sheet and assembly of battery:

[0127] Take the regenerated lithium iron phosphate positive electrode material as the active material, Super-P as the conductive agent, and ployvinylidene fluoride as the binder. The three are mixed in the ratio of 80:10:10 with N-methyl pyrrolidone and then ground to obtain a slurry. The slurry is coated on the current collector aluminum foil, which is dried in vacuum at 120°C for 12 hours. Then the electrode sheet is punched into a positive electrode sheet by a sheet punching machine to obtain the positive electrode. 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 of 1:1:1).

[0128] Comparative Example 3

[0129] (1) The preparation method of the dissolution aid 2 includes the following steps:

[0130] H1: Put 0.35 g of 4-acrylamide benzene-18-crown ether, 2 g of 2-amino-4-methylsulfonyl phenol, and 1 g of triethylamine into a reaction kettle, and stir at 50°C for 1 h;

[0131] H2: Dry nitrogen is introduced, and the temperature is raised to 90°C for 2 h to form a mixed ligand containing a crown ether chelate structure;

[0132] H3: After the reaction is completed, cool down, and add molecular sieves to adsorb moisture to obtain the dissolution aid 2.

[0133] (2) The method for recycling the positive electrode material of the waste lithium iron phosphate battery based on organic solvent soaking provided in Comparative Example 3 uses the dissolution aid 2, and specifically includes the following steps:

[0134] S1: Pretreatment: The waste lithium iron phosphate battery is discharged, then disassembled, and the waste lithium iron phosphate positive electrode sheet is separated out. 10 g of the positive electrode sheet is soaked in 60 g of dimethyl sulfoxide, stirred at 50°C for 2 h to make the positive electrode material fall off from the aluminum foil, and then filtered and dried to obtain lithium iron phosphate positive electrode material powder and aluminum foil;

[0135] S2: Component separation and extraction: 12 g of the lithium iron phosphate positive electrode material powder, 80 g of a 10% mass concentration sulfuric acid solution, and 0.1 g of the dissolution aid 2 are mixed, stirred at 80°C for 3 h to make lithium, iron, phosphorus, and other components in the positive electrode material fully dissolved, and then filtered to obtain a leaching solution;

[0136] 35 g of a 5% mass concentration hydrogen peroxide solution is added to the leaching solution to oxidize ferrous ions to ferric ions, and then the pH value of the leaching solution is adjusted to 2. 70 g of a 10% mass concentration diammonium hydrogen phosphate solution is added to make the ferric ions react with the phosphate ions to form a lithium iron phosphate precipitate, and then the lithium iron phosphate precipitate and the filtrate containing lithium ions are separated by filtration.

[0137] S3 lithium element extraction: sodium carbonate solution is added to the filtrate containing lithium ions, the pH value is adjusted to 10, the lithium ions react with carbonate ions to generate lithium carbonate precipitate, and the lithium carbonate precipitate is obtained by filtration, and the lithium carbonate precipitate is washed with deionized water for 3 times, and then dried at 80℃ to obtain lithium carbonate;

[0138] S4 iron phosphate purification: the iron phosphate precipitate is washed with deionized water for 3 times, and then dried at 80℃; 10 g of dried iron phosphate and 60 g of 10% mass concentration phosphoric acid solution are mixed, stirred at 60℃ for 1 h, filtered to obtain purified iron phosphate precipitate, and then washed with deionized water for 2 times and dried at 80℃;

[0139] S5 positive electrode material re-preparation: 30 g of purified iron phosphate, 20 g of lithium carbonate and 5 g of conductive agent acetylene black are mixed, 30 g of deionized water is added to form a uniform slurry, and then the slurry is dried at 100℃, ground, and calcined at high temperature, the high-temperature calcination temperature is 600℃, and the high-temperature calcination time is 7 h, to obtain regenerated lithium iron phosphate positive electrode material.

[0140] (3) Preparation of positive electrode sheet and assembly of battery:

[0141] The regenerated lithium iron phosphate positive electrode material is used as the active material, Super-P is used as the conductive agent, and the polyvinylidene fluoride is used as the binder, which are mixed and ground in the ratio of 80:10:10 with N-methyl pyrrolidone to obtain a slurry; the slurry is coated on the current collector aluminum foil, dried at 120℃ in vacuum for 12 h, and then the electrode sheet is punched into a positive electrode sheet by using a sheet punching machine, and the positive electrode is prepared; 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).

[0142] Test Example 1

[0143] The electrochemical performance test is carried out on the NEWARE tester: the first discharge specific capacity is tested at 0.2C rate, and the capacity retention rate after 100 cycles is tested.

[0144] The test results of Test Example 1 and Test Example 2 are shown in Table 1.

[0145] Table 1

[0146]

[0147] Through the data analysis of the above examples and comparative examples, the regenerated lithium iron phosphate positive electrode material prepared by the present application has excellent electrochemical performance.

[0148] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not deviate from the technical solution of the present application. Any modification, change, equivalent change and modification of the above embodiments made according to the technical essence of the present application still belong to the scope of the technical solution of the present application.

Claims

1. A method for recycling a positive electrode material of a waste lithium iron phosphate battery based on organic solvent soaking, characterized in that, According to mass parts, comprising the following steps: (1) After disassembling the waste lithium iron phosphate battery by discharging, waste lithium iron phosphate positive material powder is obtained; (2) 12-16 parts of lithium iron phosphate positive material powder and 0.1-0.5 parts of crown ether chelating type dissolution aid are mixed to obtain a leaching solution; The preparation method of the crown ether chelating type dissolution aid, according to mass parts, comprises the following steps: 0.35-1.51 parts of 4-acrylamide benzene-18-crown ether, 100-200 parts of dimethyl sulfoxide, 2-5 parts of 2-amino-4-methyl sulfone phenol and 1-3 parts of triethylamine are uniformly mixed; Heat treatment is carried out under inert atmosphere to form a mixed ligand containing crown ether chelating structure; After the reaction is completed, the water is removed to obtain the crown ether chelating type dissolution aid, wherein the mixing is uniformly mixed at a temperature of 50-70 DEG C for 1-3 h; The heat treatment temperature is 90-100 DEG C, and the heat treatment time is 2-5 h; (3) 35-45 parts of hydrogen peroxide solution are added to the leaching solution, the pH value is adjusted to 2-3, 70-80 parts of diammonium hydrogen phosphate solution are added, and the filtrate containing lithium ions and iron phosphate are obtained; (4) Sodium carbonate is added to the filtrate containing lithium ions, and the pH value is adjusted to 10-11 to obtain lithium carbonate; (5) 10-15 parts of iron phosphate in step (3) and 60-80 parts of phosphoric acid solution are mixed to obtain purified iron phosphate; (6) 30-40 parts of purified iron phosphate, 20-30 parts of lithium carbonate and 5-10 parts of acetylene black are mixed to obtain regenerated lithium iron phosphate positive material.

2. The method for recovering the positive material of waste lithium iron phosphate battery based on organic solvent soaking according to claim 1, 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-methyl pyrrolidone.

3. The method for recovering the positive material of waste lithium iron phosphate battery based on organic solvent soaking according to claim 1, characterized in that, In step (2), 80-120 parts of sulfuric acid solution are added during mixing, and stirring reaction is carried out at 80-90 DEG C for 3-4 h, wherein the mass fraction of sulfuric acid in the sulfuric acid solution is 10%-15%.

4. The method for recovering the positive material of waste lithium iron phosphate battery based on organic solvent soaking according to claim 1, characterized in that, In step (3), the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 5%-8%; The mass fraction of diammonium hydrogen phosphate in the diammonium hydrogen phosphate solution is 10%-20%.

5. The method for recovering the positive material of waste lithium iron phosphate battery based on organic solvent soaking according to claim 1, characterized in that, In step (5), the mass fraction of phosphoric acid in the phosphoric acid solution is 10%-15%.

6. The method for recovering the positive material of waste lithium iron phosphate battery based on organic solvent soaking according to claim 1, characterized in that, In step (5), the mixing is carried out by stirring reaction at 60-70 DEG C for 1-2 h.

7. The method for recovering the positive material of waste lithium iron phosphate battery based on organic solvent soaking according to claim 1, characterized in that, In step (6), after mixing, 30-40 parts of deionized water are added to form a uniform slurry, and then drying is carried out at 100-110 DEG C; After drying, calcination is carried out, the calcination temperature is 600-700 DEG C, and the calcination time is 7-10 h.

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