A method for resource recycling of cathode materials from waste lithium-ion batteries

Abstract

This invention belongs to the field of lithium iron phosphate recycling technology and relates to a method for regenerating waste lithium-ion battery cathode materials. The method includes: mixing and stirring pretreated cathode powder after roasting with a phytic acid-hydrogen peroxide system; filtering and separating the mixture to obtain solid residue and a lithium-containing leachate; mixing the solid residue with phosphoric acid, heating and reacting, and calcining to obtain battery-grade iron phosphate; and subjecting the lithium-containing leachate to secondary precipitation and thermal crystallization to obtain battery-grade lithium carbonate. This invention uses a phytic acid-hydrogen peroxide system to treat waste lithium iron phosphate battery cathode materials, efficiently recovering valuable metal elements and obtaining battery-grade iron phosphate and battery-grade lithium carbonate.

Description

Technical Field

[0001] This invention belongs to the field of lithium iron phosphate recycling technology and relates to a method for regenerating waste lithium-ion battery cathode materials. Background Technology

[0002] With the ever-increasing global demand for clean energy and electric vehicles, lithium iron phosphate (LiFePO4) batteries are widely used in electric vehicles, energy storage systems, and portable electronic devices due to their superior performance and high safety. However, with the large-scale production and use of these batteries, the effective recycling and disposal of used batteries has become an increasingly important issue. The recycling of lithium iron phosphate batteries is not only about resource reuse but also involves environmental protection and sustainable development.

[0003] Currently, the recycling of spent lithium iron phosphate batteries mainly employs mechanical processing, thermal treatment, and hydrometallurgical techniques. Mechanical processing methods, through physical crushing and sorting, can partially recover materials from the batteries, but it is difficult to effectively extract metal ions. Thermal treatment methods, such as roasting, can recover metals, but face environmental challenges due to high energy consumption and pollution. Hydrometallurgical technology can efficiently extract valuable metals from batteries at relatively low temperatures and is considered one of the most promising recycling methods. However, traditional hydrometallurgical processes typically rely on strong acids such as sulfuric acid or hydrochloric acid as leaching agents. These acidic reagents are highly corrosive, easily causing environmental harm, and require special equipment and treatment measures to ensure safety. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the existing technology by proposing a method for the resource regeneration of waste lithium-ion battery cathode materials based on a phytic acid-hydrogen peroxide system. This method can yield battery-grade iron phosphate and battery-grade lithium carbonate.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for recycling waste lithium-ion battery cathode materials includes: mixing and stirring pretreated cathode black powder after roasting with a phytic acid-hydrogen peroxide system, filtering and separating solid residue and lithium-containing leachate; mixing the solid residue with phosphoric acid, heating and reacting, and calcining to obtain battery-grade iron phosphate; and subjecting the lithium-containing leachate to secondary precipitation and thermal crystallization to obtain battery-grade lithium carbonate.

[0007] Preferably, the volume ratio of the phytic acid aqueous solution with a mass fraction of 0.1-5% and the hydrogen peroxide aqueous solution with a mass fraction of 10-40% in the phytic acid-hydrogen peroxide system is 100:(1-10).

[0008] Preferably, the preparation process of the battery-grade lithium carbonate includes: mixing lithium-containing leachate with a precipitant to precipitate, filtering to obtain a first filtrate, passing carbon dioxide gas into the first filtrate to precipitate, filtering to obtain a second filtrate, and then obtaining battery-grade lithium carbonate by thermal crystallization of the second filtrate.

[0009] Preferably, the method includes:

[0010] (1) The positive electrode black powder is calcined under an inert atmosphere to obtain pretreated positive electrode black powder;

[0011] (2) Mix phytic acid aqueous solution with a mass fraction of 0.1-5% and hydrogen peroxide aqueous solution with a mass fraction of 10-40% in a volume ratio of 100:(1-10) to obtain phytic acid-hydrogen peroxide system;

[0012] (3) Add the pretreated positive electrode black powder to the phytic acid-hydrogen peroxide mixture in (2) and stir at a constant temperature of 10-80℃ for 1-12 hours;

[0013] (4) After the reaction is complete, filter to separate the solid residue and lithium-containing leachate;

[0014] (5) The solid residue is mixed with phosphoric acid, heated and calcined to obtain battery-grade iron phosphate;

[0015] (6) After the lithium-containing leachate is mixed with the precipitant and precipitated, the first filtrate is obtained by filtration. Carbon dioxide gas is passed into the first filtrate to precipitate, and then the second filtrate is obtained by filtration. The second filtrate is then subjected to thermal crystallization to obtain battery-grade lithium carbonate.

[0016] Preferably, the method includes:

[0017] (1) The waste lithium iron phosphate battery is discharged, disassembled and crushed to obtain positive electrode black powder; the positive electrode black powder is calcined at 100-280°C under an inert atmosphere to obtain pretreated positive electrode black powder.

[0018] (2) Mix phytic acid aqueous solution with a mass fraction of 0.1-5% and hydrogen peroxide aqueous solution with a mass fraction of 10-40% in a volume ratio of 100:(1-10) to obtain phytic acid-hydrogen peroxide system;

[0019] (3) Add the pretreated positive electrode black powder to the phytic acid-hydrogen peroxide mixture in (2), with a solid-liquid ratio of 50-500 g / L, and stir at a constant temperature of 10-50°C for 1-8 hours with a stirring speed of 200-1000 rpm.

[0020] (4) After the reaction is complete, filter to separate the solid residue and lithium-containing leachate;

[0021] (5) The solid residue is mixed with phosphoric acid, heated and calcined to obtain battery-grade iron phosphate;

[0022] (6) After the lithium-containing leachate is mixed with the precipitant and precipitated, the first filtrate is obtained by filtration. Carbon dioxide gas is passed into the first filtrate to precipitate, and then the second filtrate is obtained by filtration. The second filtrate is then subjected to thermal crystallization to obtain battery-grade lithium carbonate.

[0023] Preferably, the phytic acid aqueous solution in (1) has a mass fraction of 0.5-2%.

[0024] Preferably, the calcination reaction temperature in (1) is 180-220°C and the time is 1-10h.

[0025] Preferably, the volume ratio of the phytic acid aqueous solution with a mass fraction of 0.5-2% and the hydrogen peroxide aqueous solution with a mass fraction of 30% in (2) is 100:(3-10).

[0026] Preferably, the constant temperature stirring reaction in (3) is 10-39°C and the time is 1-6h.

[0027] Further preferred, the constant temperature stirring reaction in (3) is 20-30℃, and the time is 2-3h.

[0028] Preferably, the isothermal stirring reaction in (3) is carried out in air at normal pressure.

[0029] Preferably, the isothermal stirring reaction in (3) is carried out under pressure in an oxygen atmosphere.

[0030] Further optimization is achieved by applying a pressure of 0.1–5 MPa.

[0031] In a further preferred embodiment, in step (3), the pretreated positive electrode black powder is added to the phytic acid-hydrogen peroxide mixture in step (2), the solid-liquid ratio is 50-500 g / L, it is placed in an oxygen atmosphere and pressurized to 0.1-5 MPa, and the mixture is stirred at a constant temperature of 10-38°C for 1-8 hours, with a stirring speed of 200-1000 rpm.

[0032] Preferably, the lithium leaching rate in the lithium-containing leachate in (4) is ≥90%.

[0033] Further preferably, the lithium leaching rate in the lithium-containing leachate in (4) is ≥92%.

[0034] More preferably, the lithium leaching rate in the lithium-containing leachate in (4) is ≥96%.

[0035] Preferably, the mass ratio of solid residue to phosphoric acid in (5) is 1:(0.1-5).

[0036] More preferably, the mass ratio of the solid residue to phosphoric acid in (5) is 1:(0.8-3).

[0037] Preferably, the heating reaction temperature in (5) is 70-94°C and the time is 1-20h.

[0038] Preferably, the calcination in step (5) is carried out in an inert gas at a temperature of 550–800°C for 1–8 hours.

[0039] Further preferably, the purity of the battery-grade iron phosphate is ≥99.5%.

[0040] More preferably, the recovery rate of the battery-grade iron phosphate is ≥90%.

[0041] Preferably, the precipitant in (6) includes one or both of calcium oxide and calcium hydroxide.

[0042] Further preferably, 1 to 10 g of precipitant is added to every 100 ml of lithium-containing leachate.

[0043] More preferably, the lithium recovery rate is ≥80%.

[0044] Preferably, in step (6), 3-10g of calcium oxide is added to every 100ml of leachate. After complete precipitation, the first filtrate is separated by filtration. Carbon dioxide gas is continuously introduced into the first filtrate. After complete precipitation, the second filtrate is separated by filtration. The second filtrate is then pyrolyzed at 100-140℃ to crystallize. The solid is filtered, washed with hot water, and dried to obtain battery-grade lithium carbonate.

[0045] Further preferably, the lithium recovery rate is ≥90%.

[0046] Further preferably, the purity of the battery-grade lithium carbonate is ≥99.5%.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. This invention uses a phytic acid-hydrogen peroxide system to treat waste lithium iron phosphate battery cathode materials, efficiently recovering valuable metal elements from waste lithium iron phosphate batteries.

[0049] 2. In the phytic acid-hydrogen peroxide system used in this invention, phytic acid, as an organic acid, can effectively complex metal ions, while hydrogen peroxide, as an oxidant, can promote the dissolution and leaching of metals. Furthermore, phytic acid can inhibit the decomposition of hydrogen peroxide, thus reducing the amount of hydrogen peroxide used.

[0050] 3. The leaching process of this invention is carried out at room temperature or medium-low temperature, without the need for high temperature and high pressure operation, which greatly reduces energy consumption compared with traditional heat treatment and hydrometallurgical processes.

[0051] 4. The method for regenerating waste lithium-ion battery cathode materials of the present invention achieves selective lithium extraction.

[0052] 5. The method for recycling waste lithium-ion battery cathode materials of the present invention can obtain battery-grade iron phosphate and battery-grade lithium carbonate. Detailed Implementation

[0053] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0054] Unless otherwise specified, the materials used in this invention are commercially available products, and the methods used are conventional technical means.

[0055] In this paper, the lithium leaching rate is calculated using the following formula (1):

[0056]

[0057] Where x represents the lithium leaching rate, m1 is the mass of the solid residue, m2 is the mass of the raw material, ω1% is the percentage of lithium content in the solid residue detected by ICP, and ω2% is the percentage of lithium content in the raw material.

[0058] Example 1

[0059] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain cathode black powder. The black powder was then calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated cathode black powder, which consisted of 4.13% lithium, 18.33% phosphorus, and 32.71% iron. A phytic acid-hydrogen peroxide system was prepared by mixing 100 ml of a 1% phytic acid aqueous solution and 3 ml of a 30% hydrogen peroxide aqueous solution. 10 g of the pretreated cathode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0060] Solid residue and phosphoric acid (pH=2) in a mass ratio of 1:1 were mixed and heated at 90°C for 10 hours. Then, the mixture was washed three times with phosphoric acid (pH=2) and water respectively, dried, and calcined at 650°C for 4 hours in an inert gas atmosphere to obtain battery-grade iron phosphate.

[0061] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0062] In this embodiment, the lithium leaching rate was 92.3%, the lithium recovery rate was 87.3%, and the purity of battery-grade lithium carbonate reached 99.5%; the recovery rate of iron phosphate was 90.3%, and the purity of battery-grade iron phosphate reached 99.6%.

[0063] Example 2

[0064] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 0.5% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0065] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0066] In this embodiment, the lithium leaching rate was 88.6%, and the lithium recovery rate was 83.5%.

[0067] Example 3

[0068] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 4 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0069] Solid residue and phosphoric acid (pH=2) in a mass ratio of 1:1.1 were mixed and heated at 90°C for 10 hours. Then, the mixture was washed three times with phosphoric acid (pH=2) and water respectively, dried, and calcined at 650°C for 4 hours in an inert gas atmosphere to obtain battery-grade iron phosphate.

[0070] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat crystallize the second filtrate at 120℃, filter to obtain a solid, wash with hot water at 95℃ and dry to obtain battery-grade lithium carbonate.

[0071] In this embodiment, the lithium leaching rate is 94.5%, and the lithium recovery rate is 90.2%. The purity of the battery-grade iron phosphate and the battery-grade lithium carbonate in this embodiment reaches 99.6%.

[0072] Example 4

[0073] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 6 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0074] Solid residue and phosphoric acid (pH=2) in a mass ratio of 1:1 were mixed and heated at 90°C for 12 hours. Then, the mixture was washed three times with phosphoric acid (pH=2) and water respectively, dried, and calcined at 650°C for 4 hours in an inert gas atmosphere to obtain battery-grade iron phosphate.

[0075] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat crystallize the second filtrate at 125℃. Filter to obtain a solid, wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0076] In this embodiment, the lithium leaching rate is 96.6%, the lithium recovery rate is 92.3%, the purity of battery-grade lithium carbonate reaches 99.7%, and the recovery rate of battery-grade iron phosphate is 95.6%, with a purity of 99.8%.

[0077] Example 5

[0078] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 20 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0079] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0080] In this embodiment, the lithium leaching rate was 82.3% and the lithium recovery rate was 78.6%.

[0081] Example 6

[0082] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 8 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 20 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0083] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0084] In this embodiment, the lithium leaching rate was 85.6%, and the lithium recovery rate was 81.3%.

[0085] Example 7

[0086] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 10 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0087] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0088] In this embodiment, the lithium leaching rate was 96.7% and the lithium recovery rate was 92.5%.

[0089] Example 8

[0090] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 2% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0091] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0092] In this embodiment, the lithium leaching rate was 96.5%, and the lithium recovery rate was 92.3%.

[0093] Example 9

[0094] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 1 hour at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0095] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0096] In this embodiment, the lithium leaching rate was 91.2%, and the lithium recovery rate was 86.5%.

[0097] Example 10

[0098] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 3 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0099] Add 5g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Heat the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0100] In this embodiment, the lithium leaching rate was 91.4%, and the lithium recovery rate was 86.6%.

[0101] Example 11

[0102] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 190°C for 4 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 30°C for 2 hours at a stirring speed of 400 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0103] Solid residue and phosphoric acid (pH=2) in a mass ratio of 1:1.2 were mixed and heated at 90°C for 10 hours. Then, the mixture was washed three times with phosphoric acid (pH=2) and water respectively, dried, and calcined at 650°C for 4 hours in an inert gas atmosphere to obtain battery-grade iron phosphate.

[0104] Add 7g of calcium oxide to 100ml of lithium-containing leachate. After complete precipitation, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After complete precipitation, filter to separate the second filtrate. Pour the second filtrate at 120℃ to crystallize. Filter to obtain a solid. Wash with hot water at 90℃ and dry to obtain battery-grade lithium carbonate.

[0105] In this embodiment, the lithium leaching rate is 92.7%, the lithium recovery rate is 87.1%, the purity of battery-grade lithium carbonate reaches 99.5%, the recovery rate of iron phosphate is 96.6%, and the purity of battery-grade iron phosphate reaches 99.5%.

[0106] Example 12

[0107] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 190°C for 4 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture, placed in an oxygen environment at 25°C, pressurized to 1 MPa, and stirred for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0108] Battery-grade lithium carbonate was recovered according to the method in Example 1.

[0109] In this embodiment, the lithium leaching rate was 96.6%, and the lithium recovery rate was 92.4%.

[0110] Example 13

[0111] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 300°C for 2 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0112] Lithium carbonate was recovered according to the method in Example 1.

[0113] In this embodiment, the lithium leaching rate was 93.5%, and the lithium recovery rate was 87.4%.

[0114] Comparative Example 1

[0115] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 10g of pretreated positive electrode black powder was added to 100ml of 1% phytic acid aqueous solution and stirred at 25°C for 2 hours at a stirring speed of 300rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0116] Lithium carbonate was recovered according to the method in Example 1.

[0117] In this comparative example, the lithium leaching rate was 32.3%, and the lithium recovery rate was 19.6%.

[0118] Comparative Example 2

[0119] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 10g of pretreated positive electrode black powder was added to 100ml of 0.9% hydrogen peroxide solution and stirred at 25°C for 2 hours at a stirring speed of 300rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0120] Lithium carbonate was recovered according to the method in Example 1.

[0121] In this comparative example, the lithium leaching rate was 36.2%, and the lithium recovery rate was 26.4%.

[0122] Comparative Example 3

[0123] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% phytic acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a phytic acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the phytic acid-hydrogen peroxide mixture and stirred at 50°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0124] Lithium carbonate was recovered according to the method in Example 1.

[0125] In this comparative example, the lithium leaching rate was 84.7%, and the lithium recovery rate was 80.1%.

[0126] Comparative Example 4

[0127] Waste lithium iron phosphate batteries were discharged, disassembled, and crushed to obtain positive electrode black powder. The black powder was calcined at 210°C for 3 hours under an inert atmosphere to obtain pretreated positive electrode black powder. 100 ml of 1% citric acid aqueous solution and 3 ml of 30% hydrogen peroxide aqueous solution were mixed to obtain a citric acid-hydrogen peroxide system. 10 g of pretreated positive electrode black powder was added to the citric acid-hydrogen peroxide mixture and stirred at 25°C for 2 hours at a stirring speed of 300 rpm. After the reaction was completed, the solid residue and lithium-containing leachate were separated by filtration.

[0128] Lithium carbonate was recovered according to the method in Example 1.

[0129] In this comparative example, the lithium leaching rate was 89.3%, and the lithium recovery rate was 79.5%.

[0130] Comparative Example 5

[0131] The solid residue of Example 1 in a mass ratio of 1:1 was mixed with phosphoric acid (pH=2), and the mixture was heated at 70°C for 10 hours. Then, the mixture was washed three times with phosphoric acid (pH=2) and water respectively, dried, and calcined at 650°C for 4 hours in an inert gas atmosphere to obtain iron phosphate.

[0132] Add 1g of calcium oxide to 100ml of lithium-containing leachate. After precipitation is complete, filter to separate the first filtrate. Continuously pass carbon dioxide gas into the first filtrate. After precipitation is complete, filter to separate the second filtrate. Pyrolyze the second filtrate at 120℃ to obtain a solid. Wash with hot water at 90℃ and dry to obtain lithium carbonate.

[0133] In this comparative example, the recovery rate of ferric phosphate was 80.6%, and the purity was 99.5%; the recovery rate of lithium carbonate was 79.6%, and the purity was 99.5%.

[0134] In summary, the method for regenerating waste lithium-ion battery cathode materials of the present invention has low energy consumption, mild reaction conditions, achieves a lithium leaching rate of over 96%, and can obtain battery-grade iron phosphate and battery-grade lithium carbonate.

[0135] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for resource recycling of cathode materials from waste lithium-ion batteries, characterized in that, The method includes: (1) The positive electrode black powder is calcined under an inert atmosphere to obtain pretreated positive electrode black powder; (2) Mix phytic acid aqueous solution with a mass fraction of 0.1-5% and hydrogen peroxide aqueous solution with a mass fraction of 10-40% in a volume ratio of 100:(1-10) to obtain phytic acid-hydrogen peroxide system; (3) Add the pretreated positive electrode black powder to the phytic acid-hydrogen peroxide mixture in (2) and stir at a constant temperature of 10~80℃ for 1~12h; (4) After the reaction is complete, filter to separate the solid residue from the lithium-containing leachate; (5) The solid residue is mixed with phosphoric acid, heated and calcined to obtain battery-grade iron phosphate; (6) After the lithium-containing leachate is mixed with the precipitant and precipitated, the first filtrate is obtained by filtration. Carbon dioxide gas is passed into the first filtrate and precipitated. The second filtrate is then filtered to obtain the battery-grade lithium carbonate by thermal crystallization.

2. The method for resource regeneration of waste lithium-ion battery cathode materials according to claim 1, characterized in that, The isothermal stirring reaction in (3) is carried out in air at normal pressure.

3. The method for resource regeneration of waste lithium-ion battery cathode materials according to claim 1, characterized in that, The isothermal stirring reaction in (3) is carried out under pressure in an oxygen atmosphere, with a pressure of 0.1~5 MPa.

4. The method for resource regeneration of waste lithium-ion battery cathode materials according to claim 1, characterized in that, The constant temperature stirring reaction in (3) is 10~39℃ and the time is 1~6h.

5. The method for resource regeneration of waste lithium-ion battery cathode materials according to claim 1, characterized in that, The mass ratio of solid residue to phosphoric acid in (5) is 1:(0.1~5).

6. The method for resource regeneration of waste lithium-ion battery cathode materials according to claim 1, characterized in that, The heating reaction temperature in (5) is 70~94℃ and the time is 1~20h.

7. The method for resource regeneration of waste lithium-ion battery cathode materials according to claim 1, characterized in that, In step (5), calcination is carried out in an inert gas at a temperature of 550-800°C for 1-8 hours.

8. The method for resource regeneration of waste lithium-ion battery cathode materials according to claim 1, characterized in that, In step (6), 1-10g of precipitant is added to every 100ml of lithium-containing leachate.

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