Leaching and recycling method for positive electrode material of waste lithium iron phosphate battery capable of improving leaching rate of lithium ions

Abstract

The invention relates to a waste lithium iron phosphate battery positive electrode material leaching recovery method capable of improving the lithium ion leaching rate. The method comprises the following steps: adding the positive electrode material of the waste lithium iron phosphate battery into deionized water, heating, adding hydrogen peroxide, adjusting the pH value by using a concentrated sulfuric acid solution, soaking, and filtering to obtain a Li < + >-containing solution and a filter cake containing FePO4; adding hydrogen peroxide and an oxidation catalyst into the low-concentration Li < + >-containing solution, heating, filtering to remove the catalyst, adjusting the pH value by using a concentrated sulfuric acid solution, soaking, and filtering to obtain a high-concentration Li < + >-containing solution and a filter cake containing FePO4; adding NaOH into the high-concentration Li < + >-containing filtrate to remove impurities, then adding Na2CO3, and precipitating to obtain crude lithium carbonate; the method comprises the following steps: repeatedly cleaning crude lithium carbonate with boiling water to obtain a Li2CO3 product; the method can effectively improve the lithium ion leaching rate.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling cathode materials of lithium iron phosphate batteries, and in particular to a method for leaching and recycling cathode materials of waste lithium iron phosphate batteries for improving the lithium ion leaching rate. Background Art

[0002] With the widespread use of lithium iron phosphate batteries, they will be scrapped after a certain number of cycles and a service life of 8 to 10 years. It is estimated that by 2025, the number of scrapped lithium iron phosphate power batteries will be nearly 100×10 4 If these used batteries are discarded carelessly, they not only pollute the soil and increase environmental pH, but also waste lithium resources, which is contrary to the concept of low-carbon green development. To solidly promote the construction of "zero-waste cities," effectively reduce the intensity of solid waste generation, improve the comprehensive utilization of solid waste, and effectively fight the battle against pollution, it is imperative to recycle and reuse the positive electrode materials of used lithium iron phosphate batteries.

[0003] Currently, several Chinese patents are worthy of attention in the recycling of spent lithium iron phosphate battery cathode materials. Chinese patent CN115611252B discloses a method for recovering iron phosphate and lithium carbonate from spent lithium iron phosphate cathode materials. This method involves sequentially subjecting the spent lithium iron phosphate cathode materials to acid leaching, oxidation, and crystallization to obtain iron phosphate. The residual solution is then subjected to sequential impurity removal and precipitation to obtain lithium carbonate.

[0004] Chinese patent CN112768799B focuses on the recycling of waste lithium iron phosphate cathode materials, disclosing a dry method for recycling waste lithium iron phosphate cathode sheets. The specific steps are: first, crushing and screening the waste lithium iron phosphate cathode sheets to separate the foil and lithium iron phosphate sheet material; then, sintering the lithium iron phosphate sheet material under an inert atmosphere and subsequently crushing it to a particle size of 1-5 μm to obtain a primary sintered material; finally, mixing the primary sintered material with a dopant at a concentration of 0.2-0.5% by weight, sintering again under an inert atmosphere, and then crushing it to obtain the lithium iron phosphate cathode material.

[0005] Chinese patent CN111924817B discloses a method for the comprehensive utilization of waste lithium iron phosphate cathode materials. The method involves leaching the waste lithium iron phosphate cathode materials with acid. After adjusting the iron-phosphorus ratio and pH of the leachate to a strongly acidic state, an oxidation reaction converts ferrous ions into ferric ions, generating a ferric phosphate precipitate. Liquid-solid separation is then performed to obtain hydrated ferric phosphate and a lithium-containing solution. The lithium-containing solution is then subjected to precipitation to remove heavy metal ions. Liquid-solid separation results in a heavy metal precipitate residue and a lithium-containing purified solution. Finally, a lithium ion precipitant is added to the lithium-containing purified solution, and the pH is adjusted to a weakly acidic or alkaline state to allow lithium ion precipitation. Liquid-solid separation is then performed to obtain a lithium salt product.

[0006] Existing patents and related technologies primarily recycle spent lithium iron phosphate battery cathode materials through direct physical regeneration and hydrometallurgical methods. However, the direct physical regeneration method, due to its high-temperature calcination process, consumes a lot of energy, while the hydrometallurgical method suffers from low lithium leaching rates and urgently requires further optimization and improvement. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides a method for leaching and recovering waste lithium iron phosphate battery positive electrode materials to improve the lithium ion leaching rate, and the operating steps are as follows:

[0008] S1: Add 15-25 parts of waste lithium iron phosphate battery positive electrode materials to 200-300 parts of deionized water, heat it up, add 30-40 parts of hydrogen peroxide, adjust the pH value to 2-3 with concentrated sulfuric acid solution, soak, filter, and obtain Li-containing + solution and filter cake containing FePO4;

[0009] S2: Towards low concentration of Li + solution, add 20-30 parts of hydrogen peroxide and 1-3 parts of oxidation catalyst, heat to a high temperature, filter to remove the catalyst, adjust the pH value to 2-3 with concentrated sulfuric acid solution, soak, filter, and obtain a high-concentration Li+-containing solution and a filter cake containing FePO4;

[0010] S3: Towards high concentration of Li + After adding 10-20 parts of NaOH to the filtrate to remove impurities, 15-25 parts of Na2CO3 are added to precipitate to obtain crude lithium carbonate;

[0011] S4: The crude lithium carbonate is repeatedly washed with boiling water 2-4 times to obtain Li2CO3 product.

[0012] The mass fractions of Li, Fe and P in the waste lithium iron phosphate battery positive electrode material are 4.4%, 34.2% and 19.0% respectively.

[0013] The soaking temperature of S1 is 30-40°C and the soaking time is 50-60 minutes.

[0014] The soaking temperature of S2 is 40-50°C and the soaking time is 40-50 minutes.

[0015] The precipitation time of S3 is 60-120 min.

[0016] The preparation method of the oxidation catalyst is:

[0017] A1: Mix 7-14 parts by weight of 4-aminopyridine-2,6-dicarboxylic acid, 5-10 parts of vanadium oxalate, and 100-150 parts of water, react at 40-55° C. for 50-100 minutes, remove the water by distillation, and then dry in vacuo to obtain a vanadium complex of 4-aminopyridine-2,6-dicarboxylate.

[0018] A2: Mix 3-7 parts of 4-aminopyridine-2,6-dicarboxylic acid vanadium complex, 2-5 parts of methacryloyloxypropyl pentamethyldisiloxane, 0.02-0.5 parts of tetrapropylene tin, 105-130 parts of aluminum oxide, 1-3 parts of potassium hydroxide, and 1000-1400 parts of dichloroethane, by weight, react at 60-70°C for 200-300 minutes, filter, and dry in a vacuum oven to obtain an oxidation catalyst.

[0019] Principle and effect

[0020] 1. In amino-olefin addition reactions, the lone pair of electrons on the amino group attacks the π bond of the olefin, resulting in a redistribution of charge. This charge transfer process is one of the key steps in the reaction. During catalysis, the charge distribution on the catalyst surface affects the adsorption and desorption of the substrate, thereby affecting catalytic efficiency.

[0021] The spatial configuration of reactants significantly influences reaction activity. The position and size of olefin substituents influence their electron density distribution, which in turn affects reaction rate and selectivity. During catalysis, the spatial configuration of the catalyst also influences substrate adsorption and product desorption, thus affecting catalytic efficiency.

[0022] 2. Electrochemical characteristics

[0023] In electrochemical systems, the charge state of the electrode surface affects the adsorption and desorption of reactants, thereby affecting reaction rate and efficiency. Alumina-supported vanadium and tin complex catalysts may improve catalytic efficiency by altering the charge state of the electrode surface, thereby increasing the adsorption capacity of reactants and the desorption capacity of products.

[0024] Electrode reactions: In electrochemical systems, the charge state of the electrode surface affects the adsorption and desorption of reactants, thereby affecting reaction rate and efficiency. Alumina-supported vanadium and tin complex catalysts may improve catalytic efficiency by altering the charge state of the electrode surface, increasing the adsorption capacity of reactants and the desorption capacity of products.

[0025] 3. Catalytic activity and selectivity

[0026] Alumina-supported vanadium and tin complexes provide highly active catalytic sites that effectively promote the conversion of reactants. These active sites may have specific geometric shapes and electronic properties that can form stable transition states with the reactants and reduce the activation energy of the reaction.

[0027] By adjusting the composition and structure of the catalyst, highly selective synthesis of specific products can be achieved. For example, by optimizing the ratio of vanadium to tin, the yield of the target product can be increased. Furthermore, the spatial configuration of the catalyst may also affect the selectivity of the product. DETAILED DESCRIPTION

[0028] 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:

[0029] The contents of Li and Fe in the leaching solution were quantitatively analyzed by flame atomic absorption spectrometer; the content of P in the leaching solution was quantitatively analyzed by proportional beam spectrophotometer.

[0030] Example 1

[0031] A method for leaching and recovering waste lithium iron phosphate battery cathode materials to improve lithium ion leaching rate, the operating steps of which are as follows:

[0032] S1: Add 15g of waste lithium iron phosphate battery positive electrode material to 200g of deionized water, heat it to a high temperature, add 30g of hydrogen peroxide, adjust the pH value to 2 with concentrated sulfuric acid solution, soak it, and filter it to obtain a filter cake containing Li+ solution and FePO4;

[0033] S2: Towards low concentration of Li + solution, add 20g hydrogen peroxide and 1g oxidation catalyst, heat to temperature, filter to remove the catalyst, adjust the pH value to 2 with concentrated sulfuric acid solution, soak, filter, and obtain a high-concentration Li+-containing solution and a filter cake containing FePO4;

[0034] S3: Towards high concentration of Li + After adding 10g of NaOH to the filtrate to remove impurities, 15g of Na2CO3 was added to precipitate to obtain crude lithium carbonate;

[0035] S4: The crude lithium carbonate is repeatedly washed with boiling water twice to obtain Li2CO3 product.

[0036] The mass fractions of Li, Fe and P in the waste lithium iron phosphate battery positive electrode material are 4.4%, 34.2% and 19.0% respectively.

[0037] The soaking temperature of S1 is 30° C. and the soaking time is 50 min.

[0038] The soaking temperature of S2 is 40° C. and the soaking time is 40 minutes.

[0039] The precipitation time of S3 is 60 min.

[0040] The preparation method of the oxidation catalyst is:

[0041] A1: 7 g of 4-aminopyridine-2,6-dicarboxylic acid, 5 g of vanadium oxalate, and 100 g of water were mixed, reacted at 40° C. for 50 minutes, distilled to remove water, and then dried in vacuo to obtain a vanadium complex of 4-aminopyridine-2,6-dicarboxylate.

[0042] A2: 3 g of 4-aminopyridine-2,6-dicarboxylic acid vanadium complex, 2 g of methacryloyloxypropyl pentamethyldisiloxane, 0.02 g of tetrapropylene tin, 105 g of aluminum oxide, 1 g of potassium hydroxide, and 1000 g of dichloroethane were mixed, reacted at 60° C. for 200 minutes, filtered, and dried in a vacuum oven to obtain an oxidation catalyst.

[0043] Example 2

[0044] A method for leaching and recovering waste lithium iron phosphate battery cathode materials to improve lithium ion leaching rate, the operating steps of which are as follows:

[0045] S1: Add 18g of waste lithium iron phosphate battery positive electrode material to 240g of deionized water, heat it up, add 33g of hydrogen peroxide, adjust the pH value to 2 with concentrated sulfuric acid solution, soak it, filter it, and obtain Li-containing + solution and filter cake containing FePO4;

[0046] S2: Towards low concentration of Li + Solution, add 23g hydrogen peroxide, 2g oxidation catalyst, heat to temperature, filter to remove catalyst, adjust pH value to 2 with concentrated sulfuric acid solution, soak, filter, and obtain high concentration of Li + solution and filter cake containing FePO4;

[0047] S3: Towards high concentration of Li + After adding 13 g of NaOH to the filtrate to remove impurities, 18 g of Na2CO3 was added to precipitate to obtain crude lithium carbonate;

[0048] S4: The crude lithium carbonate is repeatedly washed with boiling water three times to obtain Li2CO3 product.

[0049] The mass fractions of Li, Fe and P in the waste lithium iron phosphate battery positive electrode material are 4.4%, 34.2% and 19.0% respectively.

[0050] The soaking temperature of S1 is 35° C. and the soaking time is 55 minutes.

[0051] The soaking temperature of S2 is 45° C. and the soaking time is 45 minutes.

[0052] The precipitation time of S3 is 80 min.

[0053] The preparation method of the oxidation catalyst is:

[0054] A1: 9 g of 4-aminopyridine-2,6-dicarboxylic acid, 6 g of vanadium oxalate, and 110 g of water were mixed, reacted at 45°C for 60 minutes, distilled to remove water, and then dried in vacuo to obtain a vanadium complex of 4-aminopyridine-2,6-dicarboxylate.

[0055] A2: 4 g of 4-aminopyridine-2,6-dicarboxylic acid vanadium complex, 3 g of methacryloyloxypropyl pentamethyldisiloxane, 0.2 g of tetrapropylene tin, 110 g of aluminum oxide, 2 g of potassium hydroxide, and 1100 g of dichloroethane were mixed, reacted at 65° C. for 240 minutes, filtered, and dried in a vacuum oven to obtain an oxidation catalyst.

[0056] Example 3

[0057] A method for leaching and recovering waste lithium iron phosphate battery cathode materials to improve lithium ion leaching rate, the operating steps of which are as follows:

[0058] S1: Add 23g of waste lithium iron phosphate battery positive electrode material to 280g of deionized water, heat it up, add 38g of hydrogen peroxide, adjust the pH value to 3 with concentrated sulfuric acid solution, soak it, filter it, and obtain Li-containing + solution and filter cake containing FePO4;

[0059] S2: Towards low concentration of Li + Solution, add 28g hydrogen peroxide, 2g oxidation catalyst, heat to temperature, filter to remove catalyst, adjust pH value to 3 with concentrated sulfuric acid solution, soak, filter, and obtain high concentration of Li + solution and filter cake containing FePO4;

[0060] S3: After adding 18g of NaOH to the high-concentration Li+-containing filtrate to remove impurities, 23g of Na2CO3 was added for precipitation to obtain crude lithium carbonate;

[0061] S4: The crude lithium carbonate is repeatedly washed with boiling water three times to obtain Li2CO3 product.

[0062] The mass fractions of Li, Fe and P in the waste lithium iron phosphate battery positive electrode material are 4.4%, 34.2% and 19.0% respectively.

[0063] The soaking temperature of S1 is 35° C. and the soaking time is 55 minutes.

[0064] The soaking temperature of S2 is 45° C. and the soaking time is 45 minutes.

[0065] The precipitation time of S3 is 100 min.

[0066] The preparation method of the oxidation catalyst is:

[0067] A1: 12 g of 4-aminopyridine-2,6-dicarboxylic acid, 8 g of vanadium oxalate, and 140 g of water were mixed, reacted at 50°C for 90 minutes, distilled to remove water, and then dried in vacuo to obtain a vanadium complex of 4-aminopyridine-2,6-dicarboxylate.

[0068] A2: 6 g of 4-aminopyridine-2,6-dicarboxylic acid vanadium complex, 4 g of methacryloyloxypropyl pentamethyldisiloxane, 0.4 g of tetrapropylene tin, 120 g of aluminum oxide, 2 g of potassium hydroxide, and 1300 g of dichloroethane were mixed, reacted at 65° C. for 280 minutes, filtered, and dried in a vacuum oven to obtain an oxidation catalyst.

[0069] Example 4

[0070] A method for leaching and recovering waste lithium iron phosphate battery cathode materials to improve lithium ion leaching rate, the operating steps of which are as follows:

[0071] S1: Add 25g of waste lithium iron phosphate battery positive electrode material to 300g of deionized water, heat it up, add 40g of hydrogen peroxide, adjust the pH value to 3 with concentrated sulfuric acid solution, soak it, filter it, and obtain Li-containing + solution and filter cake containing FePO4;

[0072] S2: Add 30g of hydrogen peroxide and 3g of oxidation catalyst to the low-concentration Li+ solution, heat it to a high temperature, filter out the catalyst, adjust the pH to 3 with concentrated sulfuric acid solution, soak it, and filter it to obtain a high-concentration Li+ solution and a filter cake containing FePO4;

[0073] S3: Towards high concentration of Li + After adding 20g of NaOH to the filtrate to remove impurities, 25g of Na2CO3 was added to precipitate to obtain crude lithium carbonate;

[0074] S4: The crude lithium carbonate is repeatedly washed with boiling water 4 times to obtain Li2CO3 product.

[0075] The mass fractions of Li, Fe and P in the waste lithium iron phosphate battery positive electrode material are 4.4%, 34.2% and 19.0% respectively.

[0076] The soaking temperature of S1 is 40° C. and the soaking time is 60 min.

[0077] The soaking temperature of S2 is 50° C. and the soaking time is 50 minutes.

[0078] The precipitation time of S3 is 120 min.

[0079] The preparation method of the oxidation catalyst is:

[0080] A1: 14 g of 4-aminopyridine-2,6-dicarboxylic acid, 10 g of vanadium oxalate, and 150 g of water were mixed, reacted at 55°C for 100 minutes, distilled to remove water, and then dried in vacuo to obtain a vanadium complex of 4-aminopyridine-2,6-dicarboxylate.

[0081] A2: 7 g of 4-aminopyridine-2,6-dicarboxylic acid vanadium complex, 5 g of methacryloyloxypropyl pentamethyldisiloxane, 0.5 g of tetrapropylene tin, 130 g of aluminum oxide, 3 g of potassium hydroxide, and 1400 g of dichloroethane were mixed, reacted at 70° C. for 300 minutes, filtered, and dried in a vacuum oven to obtain an oxidation catalyst.

[0082] Comparative Example 1

[0083] No oxidation catalyst was added, and the rest was the same as in Example 1.

[0084] Comparative Example 2

[0085] The other steps were the same as in Example 1 except that the vanadium complex of 4-aminopyridine-2,6-dicarboxylate was not added.

[0086] Comparative Example 3

[0087] Except for not adding tetrapropylene tin, the other steps were the same as those in Example 1.

[0088] Fe leaching rate / % P leaching rate / % Li leaching rate / % Example 1 0.03 2.1 99.89 Example 2 0.03 1.9 99.91 Example 3 0.02 1.7 99.93 Example 4 0.02 1.5 99.96 Comparative Example 1 0.22 5.7 85.61 Comparative Example 2 0.17 3.5 89.13 Comparative Example 3 0.14 2.9 91.06

[0089] Through the data analysis of the above embodiments and comparative examples, the present invention can effectively improve the lithium ion leaching rate.

[0090] 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 leaching and recovering waste lithium iron phosphate battery cathode materials to improve lithium ion leaching rate, the operating steps of which are as follows: S1: Add 15-25 parts of waste lithium iron phosphate battery positive electrode materials to 200-300 parts of deionized water, heat it up, add 30-40 parts of hydrogen peroxide, adjust the pH value to 2-3 with concentrated sulfuric acid solution, soak, filter, and obtain Li-containing + solution and filter cake containing FePO4; S2: Add 20-30 parts of hydrogen peroxide and 1-3 parts of oxidation catalyst to the low concentration Li+ solution, heat it up, filter out the catalyst, adjust the pH value to 2-3 with concentrated sulfuric acid solution, soak it, filter it, and obtain a high concentration Li+ solution. + solution and filter cake containing FePO4; S3: Towards high concentration of Li + After adding 10-20 parts of NaOH to the filtrate to remove impurities, 15-25 parts of Na2CO3 are added to precipitate to obtain crude lithium carbonate; S4: The crude lithium carbonate is repeatedly washed with boiling water 2-4 times to obtain Li2CO3 product.

2. The method for leaching and recovering waste lithium iron phosphate battery cathode materials with improved lithium ion leaching efficiency according to claim 1, characterized in that: The mass fractions of Li, Fe and P in the waste lithium iron phosphate battery positive electrode material are 4.4%, 34.2% and 19.0% respectively.

3. The method for leaching and recovering waste lithium iron phosphate battery cathode materials with improved lithium ion leaching efficiency according to claim 1, characterized in that: The soaking temperature of S1 is 30-40°C and the soaking time is 50-60 minutes.

4. The method for leaching and recovering waste lithium iron phosphate battery cathode materials with improved lithium ion leaching efficiency according to claim 1, characterized in that: The soaking temperature of S2 is 40-50°C and the soaking time is 40-50 minutes.

5. The method for leaching and recovering waste lithium iron phosphate battery cathode materials with improved lithium ion leaching efficiency according to claim 1, characterized in that: The precipitation time of S3 is 60-120 min.

6. The method for leaching and recovering waste lithium iron phosphate battery cathode materials to improve lithium ion leaching efficiency according to claim 1, characterized in that: The preparation method of the oxidation catalyst is: A1: Mix 7-14 parts by weight of 4-aminopyridine-2,6-dicarboxylic acid, 5-10 parts of vanadium oxalate, and 100-150 parts of water, react at 40-55° C. for 50-100 minutes, remove the water by distillation, and then dry in vacuo to obtain a vanadium complex of 4-aminopyridine-2,6-dicarboxylate. A2: Mix 3-7 parts of 4-aminopyridine-2,6-dicarboxylic acid vanadium complex, 2-5 parts of methacryloyloxypropyl pentamethyldisiloxane, 0.02-0.5 parts of tetrapropylene tin, 105-130 parts of aluminum oxide, 1-3 parts of potassium hydroxide, and 1000-1400 parts of dichloroethane, by weight, react at 60-70°C for 200-300 minutes, filter, and dry in a vacuum oven to obtain an oxidation catalyst.