Recycling method of positive electrode material of retired lithium iron phosphate battery

Abstract

The invention discloses a recycling method of a positive electrode material of a retired lithium iron phosphate battery, and belongs to the technical field of battery recycling. In the ball-milling treatment process, ferric chloride is added as a grinding aid, electrons are transferred from the retired lithium iron phosphate battery positive electrode material to ferric chloride under the action of mechanical stress, Fe < 3 + > in the ferric chloride is reduced into Fe < 2 + >, Li < + > is released from an olivine structure of ferric phosphate, lithium iron phosphate is oxidized into ferric phosphate, and the lithium iron phosphate battery positive electrode material is obtained. The above ball milling process can significantly increase the recovery rate of lithium, and further, the recovered lithium is comprehensively utilized and converted into a lithium carbonate product. Meanwhile, the generated iron phosphate filter residues react with alkali liquor to obtain a phosphate solution with a high additional value, the generated ferric hydroxide filter residues are further treated to obtain ferric chloride, the ferric chloride is reused in the step of ball milling treatment, and cyclic utilization of ferric salt is achieved. Therefore, the recycling method has practical industrial application potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery recycling and processing, and specifically relates to a method for recycling positive electrode materials of retired lithium iron phosphate batteries. Background Art

[0002] With the rapid development of the new energy industry, the full life cycle recycling industry of retired lithium iron phosphate batteries is booming. In the existing lithium battery recycling technology, the retired lithium batteries are first fully discharged by physical and chemical methods, and then directly disassembled, calcined, and screened to separate battery powder (positive electrode powder, graphite powder), current collector (aluminum foil, copper foil), diaphragm and other components, and then a series of processes such as acid leaching, impurity removal, and extraction are carried out to obtain a relatively pure ternary slurry and lithium-containing liquid. Since the raw materials are mixed with a large amount of copper, aluminum, graphite, iron phosphate and other substances, the traditional wet process must be used to dissolve all the metal elements in the retired lithium iron phosphate batteries with strong acid, resulting in large acid consumption and long reaction time during the acid leaching process. The content of impurity elements is high, and the lithium loss during the impurity removal process is large and the recovery rate is low. At the same time, a large amount of solid waste slag and wastewater will be generated, increasing the production cost.

[0003] Therefore, it is necessary to provide a new method for recycling the positive electrode material of retired lithium iron phosphate batteries to solve the shortcomings of the existing methods for recycling retired lithium iron phosphate batteries. Summary of the invention

[0004] The purpose of the present invention is to provide a method for recycling retired lithium iron phosphate battery positive electrode materials. The recycling method of the present invention can efficiently recover lithium in retired lithium iron phosphate battery positive electrode materials, and convert lithium into lithium carbonate products, convert the generated iron phosphate residue into phosphate, and convert the generated iron hydroxide residue into ferric chloride, which is reused in the ball milling process, while realizing the recycling of iron, reducing process production costs, and having practical potential for industrial application.

[0005] In a first aspect, the present invention provides a method for recycling positive electrode materials of retired lithium iron phosphate batteries, comprising the following steps: soaking, discharging, disassembling and sorting retired lithium iron phosphate batteries to obtain positive electrode sheets, crushing, drying and calcining the positive electrode sheets to obtain positive electrode powder; mixing the positive electrode powder with ferric chloride and subjecting it to ball milling to obtain a powder, mixing the powder with water for leaching, and separating to obtain a lithium-containing mother liquor and an iron phosphate residue; adding an alkali solution to the iron phosphate residue and reacting to obtain a phosphate solution and an iron hydroxide residue; introducing oxygen into the lithium mother liquor, and then adding an alkali solution for precipitation reaction to obtain an iron hydroxide residue and a filtrate; adding a sodium carbonate solution to the filtrate for reaction to obtain lithium carbonate and a sodium chloride solution; adding a hydrochloric acid solution to the iron hydroxide residue to obtain a ferric chloride solution, concentrating and evaporating the ferric chloride solution to obtain ferric chloride, and reusing the ferric chloride.

[0006] In the present invention, the inventors have found that during the ball milling process, ferric chloride is added as a grinding aid. Under the action of mechanical stress, electrons are transferred from the retired lithium iron phosphate battery positive electrode material to the ferric chloride. 3+ Reduced to Fe 2+ , Li + Lithium iron phosphate is released from the olivine structure of iron phosphate, and is oxidized to iron phosphate. The olivine structure of the positive electrode material remains stable. The ball milling process can significantly increase the recovery rate of lithium. In addition, the produced iron hydroxide residue is further treated to obtain ferric chloride, which is reused in the ball milling step to achieve the recycling of iron salts.

[0007] Furthermore, in the present invention, the oxygen introduced into the lithium-containing mother solution is excessive to completely convert Fe 2+ Oxidized to Fe 3+ .

[0008] In some embodiments, during the preparation of the positive electrode sheet, immersing includes: immersing in a sodium chloride solution with a mass concentration of 3-10% (for example, 3%, 5%, 7%, 10% or other values ​​within the range); discharging includes: discharging for 20-30 hours, for example, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours or other values ​​within the range, at a temperature of 20-25°C (for example, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C or other values ​​within the range).

[0009] In some embodiments, during the preparation of the positive electrode powder, drying includes: drying for 40 to 80 minutes, for example, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes or other values ​​within the range, at a temperature of 250 to 350°C (for example, 250°C, 270°C, 290°C, 310°C, 330°C, 350°C or other values ​​within the range); calcining includes: calcining for 40 to 80 minutes, for example, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes or other values ​​within the range, at a temperature of 600 to 750°C (for example, 600°C, 650°C, 700°C, 750°C or other values ​​within the range).

[0010] In the present invention, the inventors further discovered that calcining the positive electrode powder facilitates the removal of the organic binder, which is beneficial to the recycling of retired lithium iron phosphate battery positive electrode materials.

[0011] In some embodiments, during the preparation of the powder, the mass ratio of the positive electrode powder to ferric chloride is 1:(1-1.5), for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or other ratios within this range; the ball milling treatment includes: at a rotation speed of 300-900r / min (for example, it can be 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min, 900r / min or other values ​​within this range), ball milling for 5-60min, for example, it can be 5min, 10min, 20min, 30min, 40min, 50min, 60min or other values ​​within this range.

[0012] In some preferred embodiments, the mass ratio of the positive electrode powder to ferric chloride is 1:(1-1.2), and the ball milling treatment includes: ball milling for 10-30 minutes at a rotation speed of 500-900 r / min.

[0013] In some embodiments, during the preparation of the lithium-containing mother liquor and the iron phosphate residue, the mass ratio of the powder to water is 1:(3-10), for example, it can be 1:3, 1:5, 1:7, 1:9, 1:10 or other ratios within this range; the leaching includes: leaching for 40-80 minutes at a temperature of 40-80°C (for example, it can be 40°C, 50°C, 60°C, 70°C, 80°C or other values ​​within this range), for example, it can be 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes or other values ​​within this range.

[0014] In some embodiments, during the preparation of the iron hydroxide residue and the filtrate, the alkali solution is selected from at least one of a sodium hydroxide solution, a potassium hydroxide solution and a calcium hydroxide solution; and the alkali solution is added to control the pH value of the solution to be 7.2 to 7.5, for example, 7.2, 7.3, 7.4, 7.5 or other values ​​within this range.

[0015] In some embodiments, during the preparation of iron hydroxide residue and filtrate, the precipitation reaction includes: reacting for 40 to 80 minutes, for example, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes or other values ​​within the range, at a temperature of 60 to 100°C (for example, 60°C, 70°C, 80°C, 90°C, 100°C or other values ​​within the range).

[0016] In some embodiments, during the preparation of the phosphate solution and the iron hydroxide residue, the alkali solution is selected from at least one of a sodium hydroxide solution, a potassium hydroxide solution and a calcium hydroxide solution; and the alkali solution is added to control the pH value of the solution to be 11 to 14, for example, 11, 12, 13, 14 or other values ​​within this range.

[0017] In some embodiments, during the preparation of lithium carbonate and sodium chloride solutions, after adding sodium carbonate solution, the pH value of the solution is controlled to be 11-11.5, for example, it can be 11, 11.1, 11.2, 11.3, 11.4, 11.5 or other values ​​within the range; the reaction includes: at a temperature of 70-100°C (for example, it can be 70°C, 80°C, 90°C, 100°C or other values ​​within the range), the reaction time is 100-140min, for example, it can be 100min, 110min, 120min, 130min, 140min or other values ​​within the range.

[0018] In some embodiments, during the preparation of lithium carbonate and sodium chloride solution, the sodium chloride solution is recycled.

[0019] In the present invention, the obtained sodium chloride solution is recycled to the soaking step of retired lithium iron phosphate batteries, thereby realizing the comprehensive recycling of the sodium chloride solution.

[0020] The beneficial effects of the present invention are as follows: Different from the prior art, in the process of ball milling, the present invention adds ferric chloride as a grinding aid. Under the action of mechanical stress, electrons are transferred from the retired lithium iron phosphate battery positive electrode material to the ferric chloride. 3+ Reduced to Fe 2+ , Li + Released from the olivine structure of iron phosphate, lithium iron phosphate is oxidized to iron phosphate, and the above-mentioned ball milling process can significantly increase the recovery rate of lithium, and further, the recovered lithium is comprehensively utilized and converted into lithium carbonate products. At the same time, the produced iron phosphate residue is reacted with alkali solution to obtain a high value-added phosphate solution, and the produced iron hydroxide residue is further processed to obtain iron chloride, and the iron chloride is reused in the step of ball milling to realize the recycling of iron salts. In addition, the process in the present invention is simple, and the prepared iron chloride can be reused to realize the comprehensive utilization of the recovered product, reduce the process production cost, and have practical potential for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of the method for recycling the positive electrode material of retired lithium iron phosphate batteries. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The experimental methods without specific conditions in the examples are usually carried out according to conventional conditions and conditions described in the manual, or according to conditions recommended by the manufacturer. The general equipment, materials, reagents, etc. used are all available from commercial channels unless otherwise specified.

[0024] See also Figure 1 , which is a flow chart of the recycling method of retired lithium iron phosphate battery positive electrode materials of the present invention. Specifically, retired lithium iron phosphate batteries are soaked, discharged, disassembled and sorted to obtain positive electrode sheets, and the positive electrode sheets are crushed, dried and calcined to obtain positive electrode powder; the positive electrode powder is mixed with ferric chloride and ball milled to obtain powder, the powder is mixed with water for leaching, and lithium-containing mother liquor and iron phosphate residue are obtained through separation; oxygen is introduced into the lithium-containing mother liquor, and then alkaline solution is added for precipitation reaction to obtain iron hydroxide residue and filtrate; sodium carbonate solution is added to the filtrate for reaction to obtain lithium carbonate and sodium chloride solution.

[0025] Example 1 A method for recycling retired lithium iron phosphate battery positive electrode materials comprises the following steps: 1) The retired lithium iron phosphate battery was immersed in a sodium chloride solution with a mass concentration of 5%, discharged at a temperature of 25°C for 24 hours, taken out and drained, and then disassembled and sorted to obtain a positive electrode sheet, which was crushed, dried at a temperature of 300°C for 60 minutes, and then calcined at a temperature of 650°C for 60 minutes to obtain a positive electrode powder; 2) The positive electrode powder obtained in step 1) is mixed with ferric chloride in a mass ratio of 1:1.2, and ball milled for 30 minutes at a rotation speed of 600 r / min to obtain a powder, and the powder is mixed with water in a mass ratio of 1:5, and leached for 60 minutes at a temperature of 60° C., and a lithium-containing mother liquor and an iron phosphate residue are obtained by separation; 3) introducing excess oxygen into the lithium-containing mother liquor obtained in step 2), then adding sodium hydroxide solution, controlling the pH value of the solution to 7.5, and carrying out precipitation reaction at 80° C. for 60 minutes to obtain iron hydroxide residue and filtrate; adding sodium hydroxide solution to the iron phosphate residue obtained in step 2), controlling the pH value of the solution to 13, and reacting to obtain phosphate solution and iron hydroxide residue; 4) adding a saturated sodium carbonate solution to the filtrate obtained in step 3), controlling the pH value of the solution to 11.5, reacting at 90° C. for 120 min to obtain lithium carbonate and sodium chloride solution, and recycling the sodium chloride solution to step 1); adding a hydrochloric acid solution to the iron hydroxide residue obtained in step 3) to obtain a ferric chloride solution, concentrating and evaporating the ferric chloride solution to obtain ferric chloride, and recycling the ferric chloride to step 2).

[0026] Example 2 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Embodiment 1, except that, in step 2), the positive electrode powder and ferric chloride are mixed in a mass ratio of 1:1.

[0027] Example 3 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the positive electrode powder and ferric chloride are mixed in a mass ratio of 1:1.5.

[0028] Example 4 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the ball milling speed is 300 r / min.

[0029] Example 5 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the ball milling speed is 500r / min.

[0030] Example 6 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the ball milling speed is 700 r / min.

[0031] Example 7 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the ball milling speed is 900 r / min.

[0032] Example 8 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the ball milling time is 5 minutes.

[0033] Example 9 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the ball milling time is 10 minutes.

[0034] Example 10 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the ball milling time is 20 minutes.

[0035] Embodiment 11 The method for recycling the retired lithium iron phosphate battery positive electrode material in this embodiment is basically the same as that in Example 1, except that in step 2), the ball milling time is 60 minutes.

[0036] Comparative Example 1 The method for recycling the retired lithium iron phosphate battery positive electrode material in this comparative example is basically the same as that in Example 1, except that, in step 2), ferric chloride is not added.

[0037] Comparative Example 2 The method for recycling the retired lithium iron phosphate battery positive electrode material in this comparative example is basically the same as that in Example 1, except that in step 2), the ball milling speed is 100 r / min.

[0038] Comparative Example 3 The method for recycling the retired lithium iron phosphate battery positive electrode material in this comparative example is basically the same as that in Example 1, except that in step 2), the ball milling time is 2 minutes.

[0039] Comparative Example 4 The method for recycling the retired lithium iron phosphate battery positive electrode material in this comparative example is basically the same as that in Example 1, except that, in step 2), no ball milling treatment is performed.

[0040] Performance Testing The lithium leaching content in the lithium-containing mother solution prepared in step 2) of Example 1-11 and Comparative Example 1-4 was tested, and the results are shown in Table 1 below: Table 1 Results of lithium leaching content in lithium-containing mother liquor

[0041] From the data in Table 1, it can be seen that the amount of lithium leached from the lithium-containing mother solution prepared in step 2) of Example 1-11 is significantly higher than that of the lithium-containing mother solution prepared in step 2) of Comparative Example 1-4. Furthermore, from the results in Example 1-3, it can be seen that as the content of ferric chloride increases, the lithium leaching rate decreases to a certain extent. This is because as the content of ferric chloride increases, part of the Fe 3+ A flocculent Fe(OH)3 precipitate will be generated, entraining some lithium and causing lithium loss.

[0042] The difference between Comparative Example 1 and Example 1 is that ferric chloride is not added, and the results show that the lithium leaching rate is extremely low. The results show that the addition of ferric chloride can significantly promote the precipitation of lithium from the retired lithium iron phosphate battery positive electrode material.

[0043] The difference between Comparative Example 2 and Example 1 is that the ball milling speed is 100 r / min, and it is found that the lithium leaching rate has decreased to a certain extent. The results show that increasing the ball milling speed is conducive to the precipitation of lithium from the retired lithium iron phosphate battery positive electrode material.

[0044] The difference between Comparative Example 3 and Example 1 is that the ball milling time is 2 minutes, and it is found that the lithium leaching rate has decreased to a certain extent. The results show that increasing the ball milling time is conducive to the precipitation of lithium from the retired lithium iron phosphate battery positive electrode material.

[0045] The difference between Comparative Example 4 and Example 1 is that the ball milling treatment is not performed, and the results show that the lithium leaching rate is significantly reduced. The results show that the ball milling treatment is conducive to the precipitation of lithium from the retired lithium iron phosphate battery positive electrode material.

[0046] In summary, the recycling method of the present invention can efficiently recover lithium from retired lithium iron phosphate battery positive electrode materials and convert lithium into lithium carbonate products, while achieving the recycling of iron and reducing process production costs, and has practical potential for industrial application.

[0047] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0048] The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for recycling the positive electrode material of retired lithium iron phosphate batteries, characterized in that: The steps include: The retired lithium iron phosphate batteries are soaked, discharged, disassembled and sorted to obtain positive electrode sheets, and the positive electrode sheets are crushed, dried and calcined to obtain positive electrode powder; The positive electrode powder is mixed with ferric chloride and then ball-milled to obtain a powder, the powder is mixed with water for leaching, and a lithium-containing mother liquor and an iron phosphate residue are obtained by separation; Passing oxygen into the lithium-containing mother liquor, then adding alkali solution to carry out precipitation reaction, to obtain iron hydroxide residue and filtrate; adding alkali solution to the iron phosphate residue and reacting to obtain phosphate solution and iron hydroxide residue; adding sodium carbonate solution to the filtrate to react and obtain lithium carbonate and sodium chloride solution; A hydrochloric acid solution is added to the ferric hydroxide filter residue to obtain a ferric chloride solution, the ferric chloride solution is concentrated and evaporated to obtain ferric chloride, and the ferric chloride is reused.

2. The method for recycling the retired lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: In the preparation process of the positive electrode sheet, the immersion includes: immersing in a sodium chloride solution with a mass concentration of 3 to 10%; and the discharge includes: discharging for 20 to 30 hours at a temperature of 20 to 25°C.

3. The method for recycling the retired lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: In the preparation process of the positive electrode powder, the drying includes: drying at a temperature of 250 to 350° C. for 40 to 80 minutes; the calcining includes: calcining at a temperature of 600 to 750° C. for 40 to 80 minutes.

4. The method for recycling the retired lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: In the preparation process of the powder, the mass ratio of the positive electrode powder to the ferric chloride is 1:(1-1.5); the ball milling treatment includes: ball milling for 5-60 minutes at a rotation speed of 300-900 r / min.

5. The method for recycling the retired lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: In the preparation process of the lithium-containing mother liquor and the iron phosphate residue, the mass ratio of the powder to the water is 1:(3-10); the leaching includes: leaching for 40-80 minutes at a temperature of 40-80°C.

6. The method for recycling the retired lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: In the preparation process of the iron hydroxide residue and the filtrate, the alkali solution is selected from at least one of a sodium hydroxide solution, a potassium hydroxide solution and a calcium hydroxide solution; and the alkali solution is added to control the pH value of the solution to be 7.2-7.

5.

7. The method for recycling the retired lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: In the process of preparing the iron hydroxide residue and the filtrate, the precipitation reaction comprises: reacting for 40 to 80 minutes at a temperature of 60 to 100°C.

8. The method for recycling the retired lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: In the preparation process of the phosphate solution and the iron hydroxide filter residue, the alkali solution is selected from at least one of a sodium hydroxide solution, a potassium hydroxide solution and a calcium hydroxide solution; and the alkali solution is added to control the pH value of the solution to be 11-14.

9. The method for recycling the retired lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: In the preparation process of the lithium carbonate and sodium chloride solution, after adding the sodium carbonate solution, the pH value of the solution is controlled to be 11-11.5, and the reaction includes: reacting for 100-140 minutes at a temperature of 70-100°C.

10. The method for recycling retired lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: During the preparation process of the lithium carbonate and sodium chloride solution, the sodium chloride solution is recycled.

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