Method for recycling lithium ions in waste lithium iron phosphate electrode plate

Abstract

The invention discloses a method for recovering lithium ions in a waste lithium iron phosphate electrode plate, which specifically comprises the following steps: grinding the waste lithium iron phosphate electrode plate, putting into ethanol, carrying out ultrasonic treatment, filtering, drying, putting the fine powder of the electrode plate into hydrochloric acid, carrying out ultrasonic reaction, standing, and filtering to obtain filtrate; adding aluminum powder into the filtrate until no bubbles are generated, then adding the aluminum powder, carrying out constant-temperature ultrasonic reaction, and filtering to obtain second filtrate; adding a sodium hydroxide solution into the second filtrate, and filtering to obtain a third filtrate; and adding a sodium carbonate solution into the third filtrate until no precipitate is generated, filtering, adding into ethanol, carrying out ultrasonic washing, and drying to obtain lithium carbonate. According to the method disclosed by the invention, materials on the lithium iron phosphate electrode plate are gradually precipitated and removed in a manner of gradually separating and precipitating, metal is precipitated by utilizing aluminum ions, and precipitation-dissolution separation of lithium carbonate and sodium chloride is formed under the action of sodium carbonate, so that a high-purity lithium compound is obtained; the method is good in recovery stability, high in recovery rate and free of high-temperature reaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion recovery, and particularly relates to a method for recovering lithium ions from waste lithium iron phosphate electrode sheets. Background Art

[0002] The lithium iron phosphate electrode sheets contain valuable metal elements such as lithium and iron. Lithium is an important resource and is widely used in the new energy field; iron and phosphorus are also commonly used elements in industrial production. Recycling waste lithium iron phosphate electrode sheets can achieve the recycling of these resources and alleviate the problem of resource shortage. In addition, if waste lithium iron phosphate batteries are discarded or disposed of improperly, heavy metals and chemical substances therein may leak, causing pollution to the environment such as soil and water bodies, threatening the ecological balance and human health. Through reasonable recycling and treatment, the environmental pollution risk can be reduced.

[0003] Currently, the lithium recovery from waste lithium iron phosphate mainly uses wet and pyrometallurgical methods. The wet method uses leaching solution to dissolve lithium on the lithium iron phosphate electrode sheets, and after neutralization and precipitation purification, a lithium solution is obtained. Although this method can recover most of the lithium elements, there are small amounts of other metal residues in the lithium solution, resulting in a decrease in lithium purity; the pyrometallurgical method uses high-temperature roasting to remove organic matter and carbon in the electrode fragments, and the metal compounds are reduced to metals and then converted into alloys; this method has high energy consumption and a large impact on the environment. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for recovering lithium ions from waste lithium iron phosphate electrode sheets, which improves the recovery rate and purity of lithium ions.

[0005] The technical solution adopted by the present invention is a method for recovering lithium ions from waste lithium iron phosphate electrode sheets, which is specifically implemented according to the following steps: Step 1, grind the waste lithium iron phosphate electrode sheets, then put them into ethanol for ultrasonic treatment, filter and dry to obtain electrode sheet fine powder; Step 2, put the electrode sheet fine powder into hydrochloric acid for ultrasonic reaction, let it stand, filter to obtain a filtrate and a filter residue; Step 3, slowly add aluminum powder to the filtrate until no bubbles are generated, then continue to add aluminum powder for constant-temperature ultrasonic reaction, filter to obtain a second filtrate and a second filter residue; Step 4, slowly add sodium hydroxide solution to the second filtrate and adjust the pH to 7 - 8, filter to obtain a third filtrate and a third filter residue; Step 5, slowly add sodium carbonate solution to the third filtrate until no more precipitation occurs, filter and add it to ethanol for ultrasonic washing, and obtain lithium carbonate after drying.

[0006] The characteristics of the present invention also lie in that In Step 1, the temperature of the grinding treatment is 10 - 20°C; the time of the grinding treatment is 3 - 5 h; the mass ratio of the waste lithium iron phosphate electrode sheet to ethanol is 1:5 - 8; the frequency of the ultrasonic treatment is 100 - 120 kHz, the temperature of the ultrasonic treatment is 30 - 50°C, and the time of the ultrasonic treatment is 10 - 20 min; the drying temperature is 80 - 90°C.

[0007] In Step 2, the ultrasonic reaction temperature is 0 - 5°C, the ultrasonic reaction time is 2 - 4 h, and the ultrasonic frequency is 70 - 90 kHz; the standing temperature is 20 - 30°C; the standing time is 2 - 3 h. The mass ratio of the electrode sheet fine powder to hydrochloric acid is 1:6 - 9.

[0008] In Step 3, the feeding rate of the first addition of aluminum powder is 1 - 3 g / min; the mass ratio of the second addition of aluminum powder to the electrode sheet fine powder is 1:8 - 12. The constant-temperature ultrasonic reaction time is 2 - 3 h, the constant-temperature ultrasonic reaction temperature is 60 - 70°C, and the ultrasonic frequency is 60 - 90 kHz. The aluminum powder used is micron-sized aluminum powder; the particle size of the micron-sized aluminum powder is 5 - 200 μm.

[0009] In Step 4, the concentration of the sodium hydroxide solution is 10% - 20%, and the adjustment method is mechanical stirring; In Step 5, the feeding rate of sodium carbonate is 10 - 20 mL / min; the ultrasonic frequency is 70 - 90 kHz, the ultrasonic temperature is 5 - 10°C; the drying temperature is 80 - 100°C.

[0010] The beneficial effects of the present invention are: The method of the present invention gradually precipitates and removes other materials on the lithium iron phosphate electrode sheet in the way of gradually separating the precipitate, and uses the grinding method to reduce the particle size, improve the dissolution efficiency, reduce the residue in the carbon black, uses aluminum ions as a balancing agent and a displacing agent to precipitate metals such as iron, filters to obtain a solution containing lithium chloride, and realizes the precipitation of aluminum ions in pH control. Finally, under the action of sodium carbonate, the precipitation-dissolution separation of lithium carbonate and sodium chloride is formed, so as to obtain a high-purity lithium compound; this method has good recovery stability, high recovery rate, and does not require high-temperature reaction. Specific Embodiments

[0011] The present invention will be described in detail below in conjunction with specific embodiments.

[0012] The method for recycling lithium ions from waste lithium iron phosphate electrode sheets of the present invention is specifically implemented according to the following steps: Step 1, grind the waste lithium iron phosphate electrode sheet, then put it into ethanol for ultrasonic treatment for 10 - 20 min, filter and dry to obtain electrode sheet fine powder; The temperature of the grinding treatment is 10 - 20°C; the time of the grinding treatment is 3 - 5 h; The mass ratio of the waste lithium iron phosphate electrode sheet to ethanol is 1:5 - 8; The frequency of ultrasonic treatment is 100 - 120 kHz, the temperature of ultrasonic treatment is 30 - 50 °C; the drying temperature is 80 - 90 °C; After grinding into fine powder and then performing ultrasonic treatment, ethanol can play a certain washing role, and ethanol will not affect the materials inside the electrode sheet; Step 2: Put the fine powder of the electrode sheet into hydrochloric acid for low-temperature ultrasonic reaction for 2 - 4 h, let it stand for 2 - 3 h, and filter to obtain a filtrate and a filter residue; The concentration of hydrochloric acid is 10%, and the mass ratio of the fine powder of the electrode sheet to hydrochloric acid is 1:6 - 9; The temperature of the low-temperature ultrasonic reaction is 0 - 5 °C, the ultrasonic frequency is 70 - 90 kHz; the temperature for standing is 20 - 30 °C; The purpose of performing ultrasonic reaction with hydrochloric acid is to remove carbon black; hydrochloric acid can also provide an acidic environment to ensure the decomposition of lithium iron phosphate; Step 3: Slowly add aluminum powder to the filtrate at a speed of 1 - 3 g / min until no more bubbles are generated, then continue to add aluminum powder for constant-temperature ultrasonic reaction, and filter to obtain a second filtrate and a second filter residue; The purpose of this step is: on the one hand, the aluminum powder consumes the excessive hydrochloric acid in the filtrate, and on the other hand, the excessive aluminum powder reacts with other metal ions in the solution to displace them, and separation is achieved through filtration. At this time, only aluminum chloride and lithium chloride remain in the solution; The mass ratio of the second addition of aluminum powder to the fine powder of the electrode sheet is 1:8 - 12; The time of constant-temperature ultrasonic reaction is 2 - 3 h, the temperature of constant-temperature ultrasonic reaction is 60 - 70 °C, and the ultrasonic frequency is 60 - 90 kHz; The aluminum powder used is micron-sized aluminum powder; the particle size of the micron-sized aluminum powder is 5 - 200 μm; the smaller the particle size of the aluminum powder, the more sufficient the reaction, and ultrasonic waves ensure the dispersion of the aluminum powder and improve the treatment efficiency.

[0013] Step 4: Slowly add the sodium hydroxide solution to the second filtrate and adjust the pH to 7 - 8, and filter to obtain a third filtrate and a third filter residue; The concentration of the sodium hydroxide solution is 10% - 20%, and the adjustment method is mechanical stirring; Step 5: Slowly add the sodium carbonate solution to the third filtrate until no more precipitation occurs, filter and add it to ethanol for ultrasonic washing, and obtain lithium carbonate after drying; The addition rate of sodium carbonate is 10 - 20 mL / min, and the sodium carbonate solution is saturated sodium carbonate. The ultrasonic frequency of ultrasonic washing is 70 - 90 kHz, and the temperature is 5 - 10 °C; the drying temperature is 80 - 100 °C.

[0014] Example 1 The method for recovering lithium ions from waste lithium iron phosphate electrode sheets of the present invention is specifically implemented according to the following steps: Step 1, grind the waste lithium iron phosphate electrode sheets, then put them into ethanol for ultrasonic treatment for 10 min, filter and dry to obtain electrode sheet fine powder; The temperature of the grinding treatment is 10°C; the grinding treatment time is 3 h; the mass ratio of the waste lithium iron phosphate electrode sheets to ethanol is 1:5; The ultrasonic treatment frequency is 100 kHz, the ultrasonic treatment temperature is 30°C; the drying temperature is 80°C; Step 2, put the electrode sheet fine powder into hydrochloric acid for low-temperature ultrasonic reaction for 2 h, let it stand for 2 h, filter to obtain a filtrate and a filter residue; The concentration of hydrochloric acid is 10%, and the mass ratio of the electrode sheet fine powder to hydrochloric acid is 1:6; The temperature of the low-temperature ultrasonic reaction is 0°C, the ultrasonic frequency is 70 kHz; the standing temperature is 20°C; Step 3, slowly add aluminum powder to the filtrate at a speed of 1 g / min until no bubbles are generated, then continue to add aluminum powder for constant-temperature ultrasonic reaction, filter to obtain a second filtrate and a second filter residue; The mass ratio of the second addition of aluminum powder to the electrode sheet fine powder is 1:8; The constant-temperature ultrasonic reaction time is 2 h, the constant-temperature ultrasonic reaction temperature is 60°C, and the ultrasonic frequency is 60 kHz; Step 4, slowly add sodium hydroxide solution to the second filtrate and adjust the pH to 7, filter to obtain a third filtrate and a third filter residue; The concentration of the sodium hydroxide solution is 10%; Step 5, slowly add sodium carbonate solution to the third filtrate until no more precipitation occurs, filter and add it to ethanol for ultrasonic washing, and obtain lithium carbonate after drying; The addition rate of sodium carbonate is 10 mL / min, and the sodium carbonate solution is saturated sodium carbonate. The ultrasonic frequency of ultrasonic washing is 70 kHz, and the temperature is 5°C; the drying temperature is 80°C.

[0015] Example 2 The method for recovering lithium ions from waste lithium iron phosphate electrode sheets of the present invention is specifically implemented according to the following steps: Step 1, grind the waste lithium iron phosphate electrode sheets, then put them into ethanol for ultrasonic treatment for 15 min, filter and dry to obtain electrode sheet fine powder; The temperature of the grinding treatment is 15°C; the grinding treatment time is 3.5 h; the mass ratio of the waste lithium iron phosphate electrode sheets to ethanol is 1:6; The ultrasonic treatment frequency is 105 kHz, the ultrasonic treatment temperature is 30°C; the drying temperature is 80°C; Step 2: Put the fine powder of the electrode sheet into hydrochloric acid, carry out a low-temperature ultrasonic reaction for 3 h, let it stand for 2.5 h, and obtain a filtrate and a filter residue after filtration; The concentration of hydrochloric acid is 10%, and the mass ratio of the fine powder of the electrode sheet to hydrochloric acid is 1:7; The temperature of the low-temperature ultrasonic reaction is 3 °C, and the ultrasonic frequency is 70 kHz; the temperature of standing is 30 °C; Step 3: Slowly add aluminum powder to the filtrate at a rate of 2 g / min until no more bubbles are generated, then continue to add aluminum powder, carry out a constant-temperature ultrasonic reaction, and obtain a second filtrate and a second filter residue after filtration; The mass ratio of the second addition of aluminum powder to the fine powder of the electrode sheet is 1:10; The constant-temperature ultrasonic reaction time is 2 h, the constant-temperature ultrasonic reaction temperature is 65 °C, and the ultrasonic frequency is 70 kHz; Step 4: Slowly add the sodium hydroxide solution to the second filtrate and adjust the pH to 8, and obtain a third filtrate and a third filter residue after filtration; The concentration of the sodium hydroxide solution is 12%, and the adjustment method is mechanical stirring; Step 5: Slowly add the sodium carbonate solution to the third filtrate until no more precipitation occurs, filter and add it to ethanol for ultrasonic washing, and obtain lithium carbonate after drying; The addition rate of sodium carbonate is 15 mL / min, and the sodium carbonate solution is saturated sodium carbonate. The ultrasonic frequency of ultrasonic washing is 70 kHz, and the temperature is 8 °C; the drying temperature is 85 °C.

[0016] Example 3 The method for recycling lithium ions in waste lithium iron phosphate electrode sheets of the present invention is specifically implemented according to the following steps: Step 1: Grind the waste lithium iron phosphate electrode sheet, then put it into ethanol for ultrasonic treatment for 20 min, filter and dry it to obtain fine powder of the electrode sheet; The temperature of the grinding treatment is 15 °C; the grinding treatment time is 5 h; the mass ratio of the waste lithium iron phosphate electrode sheet to ethanol is 1:6; The ultrasonic frequency of ultrasonic treatment is 110 kHz, the ultrasonic treatment temperature is 45 °C; the drying temperature is 90 °C; Step 2: Put the fine powder of the electrode sheet into hydrochloric acid, carry out a low-temperature ultrasonic reaction for 2 h, let it stand for 3 h, and obtain a filtrate and a filter residue after filtration; The concentration of hydrochloric acid is 10%, and the mass ratio of the fine powder of the electrode sheet to hydrochloric acid is 1:8; The temperature of the low-temperature ultrasonic reaction is 4 °C, and the ultrasonic frequency is 75 kHz; the temperature of standing is 23 °C; Step 3: Slowly add aluminum powder to the filtrate at a rate of 2 g / min until no more bubbles are generated, then continue to add aluminum powder, carry out a constant-temperature ultrasonic reaction, and obtain a second filtrate and a second filter residue after filtration; The mass ratio of the second addition of aluminum powder to the fine powder of the electrode sheet is 1:10; The constant-temperature ultrasonic reaction time is 3 h, the constant-temperature ultrasonic reaction temperature is 70 °C, and the ultrasonic frequency is 85 kHz; Step 4, slowly add the sodium hydroxide solution to the second filtrate and adjust the pH to 8. After filtration, a third filtrate and a third filter residue are obtained; The concentration of the sodium hydroxide solution is 18%, and the adjustment method is mechanical stirring; Step 5, slowly add the sodium carbonate solution to the third filtrate until no more precipitation occurs. After filtration, it is added to ethanol for ultrasonic washing, and lithium carbonate is obtained after drying; The addition rate of sodium carbonate is 16 mL / min, and the sodium carbonate solution is saturated sodium carbonate. The ultrasonic frequency of ultrasonic washing is 70 kHz, and the temperature is 5 °C; the drying temperature is 85 °C.

[0017] Example 4 The method for recovering lithium ions in waste lithium iron phosphate electrode sheets of the present invention is specifically implemented according to the following steps: Step 1, grind the waste lithium iron phosphate electrode sheets, then put them into ethanol for ultrasonic treatment for 20 min, filter and dry to obtain fine powder of the electrode sheets; The temperature of the grinding treatment is 10 °C; the grinding treatment time is 4 h; the mass ratio of the waste lithium iron phosphate electrode sheets to ethanol is 1:7; The ultrasonic frequency of the ultrasonic treatment is 105 kHz, the ultrasonic treatment temperature is 40 °C; the drying temperature is 80 °C; Step 2, put the fine powder of the electrode sheets into hydrochloric acid for low-temperature ultrasonic reaction for 4 h, let it stand for 2 h, filter to obtain a filtrate and a filter residue; The concentration of hydrochloric acid is 10%, and the mass ratio of the fine powder of the electrode sheets to hydrochloric acid is 1:8; The temperature of the low-temperature ultrasonic reaction is 0 °C, the ultrasonic frequency is 70 kHz; the standing temperature is 25 °C; Step 3, slowly add aluminum powder to the filtrate at a speed of 3 g / min until no more bubbles are generated, then continue to add aluminum powder for constant-temperature ultrasonic reaction, filter to obtain a second filtrate and a second filter residue; The mass ratio of the second addition of aluminum powder to the fine powder of the electrode sheets is 1:10; the constant-temperature ultrasonic reaction time is 2 h, the constant-temperature ultrasonic reaction temperature is 60 °C, and the ultrasonic frequency is 75 kHz; Step 4, slowly add the sodium hydroxide solution to the second filtrate and adjust the pH to 7. After filtration, a third filtrate and a third filter residue are obtained; The concentration of the sodium hydroxide solution is 10%, and the adjustment method is mechanical stirring; Step 5: Slowly add the sodium carbonate solution to the third filtrate until no more precipitation occurs. After filtration, add it to ethanol for ultrasonic washing, and obtain lithium carbonate after drying. The adding rate of sodium carbonate is 10 mL / min, and the sodium carbonate solution is saturated sodium carbonate. The ultrasonic frequency for ultrasonic washing is 70 kHz, and the temperature is 10°C; the drying temperature is 100°C.

[0018] Example 5 The method for recycling lithium ions from waste lithium iron phosphate electrode sheets of the present invention is specifically implemented according to the following steps: Step 1: Grind the waste lithium iron phosphate electrode sheets, then place them in ethanol for ultrasonic treatment for 20 min, filter and dry to obtain electrode sheet fine powder. The temperature for grinding treatment is 15°C; the grinding treatment time is 5 h; the mass ratio of waste lithium iron phosphate electrode sheets to ethanol is 1:5. The ultrasonic frequency for ultrasonic treatment is 115 kHz, the ultrasonic treatment temperature is 40°C; the drying temperature is 80°C. Step 2: Place the electrode sheet fine powder in hydrochloric acid for low-temperature ultrasonic reaction for 2 h, let it stand for 2 h, filter to obtain a filtrate and a filter residue. The concentration of hydrochloric acid is 10%, and the mass ratio of electrode sheet fine powder to hydrochloric acid is 1:6.5. The temperature for low-temperature ultrasonic reaction is 5°C, the ultrasonic frequency is 90 kHz; the standing temperature is 30°C. Step 3: Slowly add aluminum powder to the filtrate at a rate of 1 g / min until no more bubbles are generated, then continue to add aluminum powder for constant-temperature ultrasonic reaction, filter to obtain a second filtrate and a second filter residue. The mass ratio of the second addition of aluminum powder to the electrode sheet fine powder is 1:11. The constant-temperature ultrasonic reaction time is 2 h, the constant-temperature ultrasonic reaction temperature is 60°C, and the ultrasonic frequency is 60 kHz. Step 4: Slowly add the sodium hydroxide solution to the second filtrate and adjust the pH to 8, filter to obtain a third filtrate and a third filter residue. The concentration of the sodium hydroxide solution is 10%, and the adjustment method is mechanical stirring. Step 5: Slowly add the sodium carbonate solution to the third filtrate until no more precipitation occurs. After filtration, add it to ethanol for ultrasonic washing, and obtain lithium carbonate after drying. The adding rate of sodium carbonate is 10 mL / min, and the sodium carbonate solution is saturated sodium carbonate. The ultrasonic frequency for ultrasonic washing is 70 kHz, and the temperature is 5°C; the drying temperature is 80°C.

[0019] Example 6 The method for recycling lithium ions from waste lithium iron phosphate electrode sheets of the present invention is specifically implemented according to the following steps: Step 1: Grind the waste lithium iron phosphate electrode sheets, then put them into ethanol for ultrasonic treatment for 20 min, filter and dry to obtain fine electrode powder. The temperature of the grinding treatment is 20°C; the grinding treatment time is 5 h; the mass ratio of the waste lithium iron phosphate electrode sheets to ethanol is 1:8. The frequency of the ultrasonic treatment is 120 kHz, the ultrasonic treatment temperature is 30°C; the drying temperature is 80°C. Step 2: Put the fine electrode powder into hydrochloric acid for low-temperature ultrasonic reaction for 4 h, let it stand for 3 h, filter to obtain a filtrate and a residue. The concentration of hydrochloric acid is 10%, and the mass ratio of the fine electrode powder to hydrochloric acid is 1:9. The temperature of the low-temperature ultrasonic reaction is 0°C, the ultrasonic frequency is 90 kHz; the temperature of standing is 30°C. Step 3: Slowly add aluminum powder to the filtrate at a rate of 3 g / min until no more bubbles are generated, then continue to add aluminum powder for constant-temperature ultrasonic reaction, filter to obtain a second filtrate and a second residue. The mass ratio of the second addition of aluminum powder to the fine electrode powder is 1:12. The constant-temperature ultrasonic reaction time is 3 h, the constant-temperature ultrasonic reaction temperature is 70°C, and the ultrasonic frequency is 90 kHz. Step 4: Slowly add sodium hydroxide solution to the second filtrate and adjust the pH to 7, filter to obtain a third filtrate and a third residue. The concentration of the sodium hydroxide solution is 20%, and the adjustment method is mechanical stirring. Step 5: Slowly add sodium carbonate solution to the third filtrate until no more precipitation occurs, filter and add it to ethanol for ultrasonic washing, and obtain lithium carbonate after drying. The addition rate of sodium carbonate is 20 mL / min, and the sodium carbonate solution is saturated sodium carbonate. The ultrasonic frequency of ultrasonic washing is 90 kHz, the temperature is 10°C; the drying temperature is 100°C.

Claims

1. A method for recycling lithium ions in waste lithium iron phosphate electrode sheets, characterized in that, The implementation is carried out specifically according to the following steps: Step 1: Grind the waste lithium iron phosphate electrode sheets, then put them into ethanol for ultrasonic treatment, filter and dry to obtain fine electrode powder; Step 2: Put the fine electrode powder into hydrochloric acid for ultrasonic reaction, let it stand, filter to obtain a filtrate and a filter residue; Step 3: Slowly add aluminum powder to the filtrate until no more bubbles are generated, then continue to add aluminum powder for isothermal ultrasonic reaction, filter to obtain a second filtrate and a second filter residue; Step 4: Slowly add sodium hydroxide solution to the second filtrate and adjust the pH to 7 - 8, filter to obtain a third filtrate and a third filter residue; Step 5: Slowly add sodium carbonate solution to the third filtrate until no more precipitation occurs, filter and add it to ethanol for ultrasonic washing, and obtain lithium carbonate after drying.

2. The method for recovering lithium ions in waste lithium iron phosphate electrode sheets according to claim 1, characterized in that, In the said Step 1, the temperature of the grinding treatment is 10 - 20 °C; the time of the grinding treatment is 3 - 5 h; the mass ratio of the waste lithium iron phosphate electrode sheets to ethanol is 1:5 - 8; the ultrasonic treatment frequency is 100 - 120 kHz, the ultrasonic treatment temperature is 30 - 50 °C, the ultrasonic treatment time is 10 - 20 min; the drying temperature is 80 - 90 °C.

3. The method for recycling lithium ions in waste lithium iron phosphate electrode sheets according to claim 1, characterized in that, In the said Step 2, the mass ratio of the fine electrode powder to hydrochloric acid is 1:6 - 9.

4. The method for recovering lithium ions from waste lithium iron phosphate electrode sheets according to claim 1, wherein, In the said Step 2, the ultrasonic reaction temperature is 0 - 5 °C, the ultrasonic reaction time is 2 - 4 h, the ultrasonic frequency is 70 - 90 kHz; the standing temperature is 20 - 30 °C; the standing time is 2 - 3 h.

5. The method for recycling lithium ions in waste lithium iron phosphate electrode sheets according to claim 1, characterized in that, In the said Step 3, the speed of adding aluminum powder for the first time is 1 - 3 g / min; the mass ratio of the aluminum powder added for the second time to the fine electrode powder is 1:8 - 12.

6. The method for recovering lithium ions from waste lithium iron phosphate electrode sheets according to claim 1, wherein, In the said Step 3, the isothermal ultrasonic reaction time is 2 - 3 h, the isothermal ultrasonic reaction temperature is 60 - 70 °C, the ultrasonic frequency is 60 - 90 kHz.

7. The method for recovering lithium ions in waste lithium iron phosphate electrode sheets according to claim 1, characterized in that, In the said Step 3, the aluminum powder used is micron-sized aluminum powder; the particle size of the micron-sized aluminum powder is 5 - 200 μm.

8. The method for recovering lithium ions from waste lithium iron phosphate electrode sheets according to claim 1, wherein In the said Step 5, the adding speed of sodium carbonate is 10 - 20 mL / min; the ultrasonic frequency is 70 - 90 kHz, the ultrasonic temperature is 5 - 10 °C; the drying temperature is 80 - 100 °C.