Waste LFP battery regenerated lithium iron phosphate positive electrode material and preparation and application thereof

Abstract

The invention relates to the field of waste battery recovery, in particular to a preparation method of a waste LFP battery regenerated lithium iron phosphate positive electrode material, which comprises the following steps: placing a positive plate disassembled from a waste LFP battery in a modified stripping solution for modified stripping, and collecting a pretreated material containing the waste LFP positive electrode material; the stripping liquid is an organic solution in which organic acid is dissolved; carrying out mechanical modification on the pretreated material and an auxiliary agent, and then carrying out roasting treatment to obtain a roasted material; the auxiliary agent comprises an auxiliary agent A and an auxiliary agent B, the auxiliary agent A is CaCl2, and the auxiliary agent B is a sodium salt; the roasted material is subjected to water leaching treatment, and an iron-lithium leaching solution is obtained; the lithium iron leaching solution is subjected to alkali iron precipitation treatment, iron slag and a lithium solution are obtained, the lithium solution is subjected to lithium precipitation treatment, and lithium slag is obtained; and mixing and sintering the iron slag, the lithium slag and a phosphorus source to prepare the regenerated lithium iron phosphate positive electrode material. The method has the advantages of excellent metal recovery rate and excellent regeneration performance.

Description

Technical Field

[0001] The invention belongs to the field of battery waste recycling, and specifically relates to the field of recycling and regenerating positive electrode materials of waste lithium iron phosphate batteries. Background Art

[0002] Lithium-ion batteries are widely used in mobile electronic devices and electric vehicles due to their high energy density, excellent cycle performance and low memory effect. Following the ternary cathode materials, lithium iron phosphate cathode materials have developed rapidly and become the key competitive advantage of lithium-ion battery cathode materials. However, lithium iron phosphate batteries only have a lifespan of 5 to 8 years, which results in a large number of waste lithium-ion batteries. The large amount of valuable elements contained in them, if not recycled, will cause a large amount of resource waste and environmental pollution. At present, pyrometallurgy and hydrometallurgy are the main methods for treating waste lithium-ion batteries.

[0003] For example, a patent document with publication number WO2024212075A1 discloses a method for repairing and regenerating lithium iron phosphate, and the regeneration steps are as follows: crushing, soaking, screening, ball milling, and sorting the waste lithium iron phosphate pole pieces to obtain waste lithium iron phosphate pole powder, and then roasting the waste lithium iron phosphate pole powder in a carbon dioxide atmosphere at 750-900°C, stirring the obtained roasting product and water evenly, introducing carbon dioxide, and spray granulating the reaction mixture to obtain a lithium iron phosphate precursor; finally, calcining the obtained lithium iron phosphate precursor to obtain regenerated lithium iron phosphate. For another example, a Chinese patent document with publication number CN118666259A discloses a method for recycling and regenerating waste lithium iron phosphate batteries, which method includes: placing the positive electrode black powder of the waste lithium iron phosphate battery in a roasting treatment furnace filled with protective gas for roasting reaction, and adjusting the input chlorine flow rate based on the mixture in the roasting treatment furnace to control the roasting reaction temperature, and the roasting reaction temperature is controlled to be 350-500°C; soaking the roasting product obtained by the roasting reaction in water to obtain a roasting product solution; filtering the roasting product solution to obtain a filter cake; placing the filter cake in a high-temperature reduction furnace filled with protective gas and adding iron oxide and carbon powder, and the high-temperature reaction temperature is controlled to be 500-600°C.

[0004] In summary, there are some methods of calcination-water leaching to recover and regenerate lithium iron phosphate in the prior art, but the processing temperature of the existing process is relatively high, and the water leaching conditions are not mild enough. Moreover, the prior art finds it difficult to fully utilize the characteristics of the recycled material itself to optimize the electrochemical properties of the regenerated lithium iron phosphate material. Summary of the invention

[0005] In view of the problems faced by the existing recycling of waste lithium iron phosphate batteries, the purpose of the present invention is to provide a method for preparing lithium iron phosphate positive electrode materials based on recycled waste LFP batteries, aiming to obtain lithium iron phosphate positive electrode active materials with high electrochemical performance based on efficient recycling and regeneration of waste LFP batteries.

[0006] The second purpose of the present invention is to provide a lithium iron phosphate positive electrode material based on recycled waste LFP batteries prepared by the preparation method and its application in the preparation of lithium iron phosphate batteries.

[0007] The third object of the present invention is to provide a lithium iron phosphate battery comprising the regenerated lithium iron phosphate positive electrode material, and its positive electrode and positive electrode material.

[0008] A method for preparing a lithium iron phosphate positive electrode material regenerated from a waste LFP battery, wherein the positive electrode sheet disassembled from the waste LFP battery is placed in a modified stripping solution for modified stripping, and a pre-treated material containing the waste LFP positive electrode material is collected; the stripping solution is an organic solution containing an organic acid; The pre-treated material and the auxiliary agent are mechanically modified, and then calcined to obtain a calcined material; the auxiliary agent includes an auxiliary agent A and an auxiliary agent B, wherein the auxiliary agent A is CaCl2, and the auxiliary agent B is a sodium salt; The calcined material is subjected to water leaching to obtain an iron-lithium leaching solution; the iron-lithium leaching solution is subjected to alkali iron precipitation treatment to obtain iron slag and lithium liquid; the lithium liquid is subjected to lithium precipitation treatment to obtain lithium slag; The iron slag, lithium slag and phosphorus source are mixed and sintered to obtain the regenerated lithium iron phosphate positive electrode material.

[0009] The present invention innovatively places the positive electrode sheet in the modified stripping solution for stripping and simultaneous surface modification, and further cooperates with the subsequent synergistic mechanical modification treatment of the auxiliary agent A and the auxiliary agent B, which is conducive to low-temperature roasting transformation and improves the subsequent water immersion effect, and can regulate the simultaneous leaching and accompanying precipitation of beneficial components that are conducive to regenerative electrochemical performance. The present invention's research shows that the process can obtain excellent recovery rate, and in addition, can also obtain excellent regenerative electrochemical performance.

[0010] In the present invention, the waste LFP battery refers to a waste lithium iron phosphate battery, that is, a waste battery whose positive electrode active material is lithium iron phosphate.

[0011] In the present invention, the waste LFP batteries can be disassembled based on known processes.

[0012] In the present invention, the modified stripping system is also allowed to add negative electrode sheets stripped from waste LFP batteries.

[0013] In the present invention, in the stripping solution, the organic acid includes a C1-C6 fatty acid or a C2-C6 amine-containing fatty acid with an amino group, and can further be at least one of formic acid, acetic acid, aminodiacetic acid, and ethylenediaminetetraacetic acid; more preferably, acetic acid. The present invention shows that the combination of acetic acid and other processes can obtain better synergy, and can further improve the recovery rate and regeneration performance of the material.

[0014] Preferably, in the stripping solution, the concentration of the organic acid is 0.002-5%, and can be further 0.02-0.15% in consideration of cost.

[0015] Preferably, the organic solvent contained in the modified stripping solution includes at least one of NMP, DMF, DMSO, and C1-C4 alcohols.

[0016] Preferably, the liquid-to-solid ratio in the modification and stripping stage is 1-10 mL / g.

[0017] In the present invention, in the auxiliary agent B, the sodium salt includes at least one of sodium chloride, sodium carbonate and sodium bicarbonate; preferably sodium carbonate. The present invention shows that the combination of sodium carbonate and other processes can obtain better synergy and further improve the recovery rate and regeneration performance of the material.

[0018] Preferably, the weight ratio of the pretreatment material to the auxiliary agent A and the auxiliary agent B is 1:2.2-2.8:0.02-0.5.

[0019] Preferably, the mechanical modification is ball milling modification.

[0020] Preferably, the rotation speed of the mechanical modification is 100-300 rpm.

[0021] Preferably, the time of mechanical modification is 0.5 to 1 h.

[0022] In the present invention, the calcination temperature is 250-650° C., further can be 350-550° C., further can be 400-500° C. The heat preservation time is 2-10 hours, further can be 2-3 hours.

[0023] In the present invention, the liquid-to-solid ratio in the water immersion stage is 3-10 ml / g, the temperature in the water immersion stage is 25-60° C., and can further be 25-30° C. The water immersion time is 1-4 h, and can further be 1-1.5 h.

[0024] In the present invention, an alkaline component is added to the iron-lithium leaching solution, and the pH value of the system is controlled to be 4-6, followed by solid-liquid separation to obtain iron slag.

[0025] Preferably, the processing component is at least one of ammonia water, sodium hydroxide and potassium hydroxide.

[0026] Preferably, the iron slag is hydroxide slag of iron element.

[0027] Preferably, the lithium precipitation treatment is a carbonation precipitation step; and the lithium slag is lithium carbonate.

[0028] In the present invention, the iron slag and lithium slag can be sintered according to known principles and methods to obtain regenerated lithium iron phosphate.

[0029] Preferably, the molar ratio of Li, Fe and P in the iron slag, lithium slag and phosphorus source is 1.01-1.05:1:1.

[0030] Preferably, the sintering temperature is 500-800°C, and may further be 650-750°C.

[0031] Preferably, the sintering time is 5 to 15 hours, and further can be 9 to 11 hours.

[0032] Preferably, a carbon source is allowed to be added to the raw materials for sintering, and the carbon source is a soft carbon source and / or a hard carbon source; for example, it may be sugar, polymer, asphalt, etc.

[0033] The carbon source may be 1-10 wt.% of the total weight of the iron source, the lithium source and the phosphorus source, and may further be 3-6 wt.%.

[0034] The present invention also provides a lithium iron phosphate positive electrode material regenerated from waste LFP batteries prepared by the preparation method.

[0035] The regeneration method of the present invention can fully take advantage of the physical and chemical characteristics of waste LFP to regenerate lithium iron phosphate positive electrode materials with excellent electrochemical properties.

[0036] The present invention also provides the use of the recycled lithium iron phosphate positive electrode material of waste LFP batteries prepared by the preparation method, which is used as a positive electrode active material to prepare lithium iron phosphate batteries.

[0037] The present invention also provides a lithium iron phosphate battery, which comprises the lithium iron phosphate positive electrode material recycled from waste LFP batteries obtained by the preparation method.

[0038] The lithium iron phosphate battery of the present invention may include known components and structural parts except for the regenerated lithium iron phosphate material of the present invention.

[0039] Beneficial Effects The present invention innovatively places the positive electrode sheet in the modified stripping solution for stripping and surface modification, and further cooperates with the subsequent synergistic mechanical modification treatment of auxiliary agents A and B, which is beneficial to improving the metal recovery rate. In addition, it is also beneficial to the in-situ modification of the metal and to obtaining materials with excellent regenerative electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the XRD diagram of the lithium carbonate of Example 1.

[0041] Figure 2 This is the electrochemical performance diagram of the regenerated lithium iron phosphate of Example 1. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0043] In the present invention, there is no special requirement for the content of active material in the waste lithium-ion battery positive electrode material. Considering the economic efficiency of the process, the content is preferably above 50wt.%. In the following cases, unless otherwise stated, the active content is 85-90wt.%.

[0044] The present invention provides an optional method for regenerating waste lithium iron phosphate batteries, comprising the following steps: Step (1): Preprocessing The positive electrode sheet of the waste LFP battery is immersed in an organic solvent (such as a mixture of NMP and ethanol), and a certain amount of organic acid is added for ultrasonic pretreatment. The aluminum foil is then removed, and the remaining black material is washed with water, filtered, and dried to obtain the pretreated material; Step (2): Abrasive After the pre-treated material is evenly mixed with the additive A and the additive B, the mixture is placed in a ball mill for ball milling and mixing; Step (3): Calcination The abrasive is placed in an atmosphere furnace for calcination and then cooled to room temperature.

[0045] Step (4): Water Soaking The calcined material is dispersed in deionized water, stirred at a certain temperature for a period of time, and solid-liquid separation is performed.

[0046] Step (5): Precipitation Take the filtrate obtained in the above step, add alkaline components to adjust the pH to 4-6, separate the solid and liquid, precipitate and dry for later use to obtain iron slag, add Na2CO3 to the filtrate and evaporate and crystallize to obtain Li2CO3 (lithium slag).

[0047] Step (6): Regeneration The iron slag precipitate obtained in the previous step is evenly mixed with Li2CO3 and phosphorus source (NH4H2PO4), and then annealed at 500~800℃ for 5~15h to obtain a regenerated positive electrode.

[0048] In the step 1, the mass ratio of the positive electrode plate to NMP+ethanol is 10:1-20, and the mass ratio of NMP to ethanol is 1:0.1-50; the organic acid is one or more of formic acid, acetic acid, aminodiacetic acid, and ethylenediaminetetraacetic acid, and the amount of the organic acid added to the mixed solution is 0.002-5%.

[0049] In step 2, the auxiliary agent B is one or more of sodium chloride, sodium carbonate, and sodium bicarbonate; the mass ratio of the pretreated material to the auxiliary agent A is 1:2.2-2.8, and the mass ratio of the pretreated material to the auxiliary agent B is 1:0.02-0.5.

[0050] The atmosphere for the calcination treatment in step 3 is one of argon, hydrogen and air, the heating rate is 2 to 10°C / min, the insulation temperature is 250 to 650°C, and the insulation time is 2 to 10h.

[0051] The liquid-to-solid ratio in the stirring reaction liquid in step 4 is 3 to 10:1 (mass ratio), the stirring reaction temperature is 25 to 60° C., and the stirring reaction time is 1 to 4 hours.

[0052] The precipitate described in step 6 is evenly mixed with Li2CO3 and NH4H2PO4 according to the molar ratio of Fe, Li and P elements of 1:1.02:1, and then calcined to regenerate the lithium iron phosphate positive electrode.

[0053] Embodiment 1: Step 1 Peeling: The waste power lithium iron phosphate battery was placed in a 2 mol / L NaCl solution for 30 h discharge treatment, the discharged battery was dried at 85°C, the positive electrode sheet and the negative electrode sheet were disassembled and separated, the positive electrode sheet was immersed in a mixed solution of N-methylpyrrolidone and ethanol with a volume ratio of 1:10 (liquid-to-solid ratio of 2 mL / g), and 0.05% volume ratio of acetic acid was added, ultrasonic treatment was performed, the current collector in the electrode sheet was separated, and the aluminum foil was removed, the black powder was filtered, washed and dried to obtain the waste positive electrode powder (modified positive electrode powder); Step 2: Ball milling: Additive A (calcium chloride) and waste cathode material in a zirconia ball mill at a mass ratio of 2.3:1, add a certain amount of additive B (sodium carbonate), where the mass ratio of additive B to waste cathode material is 0.02:1, set the speed to 250 rpm, and ball mill for 1 hour; Step 3: Firing: The ball abrasive was fully ground and mixed and placed in a corundum sintering boat, and then calcined in a tube furnace in an argon atmosphere with a heating rate of 5°C / min, a temperature of 450°C, and kept warm for 2h.

[0054] Step 4 Leaching: The roasting material was 10:1 mL g -1 Deionized water was added at a liquid-to-solid ratio of 1.5, followed by water immersion at 25°C for 1 hour to obtain a solution rich in valuable metal ions. The leaching rates of valuable metals were 98.4% for Fe and 99.9% for Li.

[0055] Step 5: Stepwise precipitation: For the above solution, NH3×H2O was added to adjust the pH to 4-6 to precipitate iron as Fe(OH)3. Na2CO3 was added to the filtrate obtained after filtration and evaporated to obtain Li2CO3. The purity of the lithium carbonate product was above 99.5%. The XRD diagram is shown in the attached figure. Figure 1 shown.

[0056] Step 6 Regeneration: The obtained Fe(OH)3 precipitate, Li2CO3 and NH4H2PO4 were prepared according to the molar ratio of Fe, Li and P elements of 1:1.02:1 and evenly mixed with glucose (4~6wt% of the total weight of iron source, lithium source and phosphorus source) and annealed at 700℃ for 10h to obtain a regenerated positive electrode.

[0057] Embodiment 2: Compared with Example 1, the only difference is that the conditions of step 1 are changed, specifically: Group A: Changed the type of organic acid to formic acid; Group B: The solvent in the stripping modification solution is a mixed solvent of DMF and ethanol in a volume ratio of 1:15, the concentration of the organic acid therein is 0.1%, and the stripping liquid-solid ratio is 1 mL / g.

[0058] Other operations and parameters are the same as in Example 1.

[0059] Example 3 Compared with Example 1, the only difference is that the conditions of step 2 are changed, specifically: Group A: Change the type of additive B to sodium chloride; Group B: The mass ratio of auxiliary agent A (calcium chloride) to waste positive electrode material is 2.5:1, the mass ratio of auxiliary agent B to waste positive electrode material is 0.5:1, the ball milling time is 0.5h, and the rotation speed is 300rpm.

[0060] Other operations and parameters are the same as in Example 1.

[0061] Example 4 Compared with Example 1, the only difference is that the conditions of step 3 are changed, the roasting temperature is 400°C, and the time is 3h; in addition, in step 4, the water immersion temperature is 30°C, the water immersion liquid-to-solid ratio is 5ml / g, and the time is 1.5h.

[0062] The data obtained in step (4) are shown in Table 1 below.

[0063]

[0064] It can be seen from Examples 1 to 4 that the use of a modified stripping agent containing an organic acid for stripping, combined with the co-calcination of auxiliary agent A and auxiliary agent B, can achieve efficient recovery and utilization of iron and lithium.

[0065] Comparative Example 1 Compared with Example 1, the only difference is that in step 1, organic acid acetic acid is not added, and other operations and parameters are the same as in Example 1.

[0066] Comparative Example 2 Compared with Example 1, the only difference is that in step 1, acetic acid is replaced by inorganic acid sulfuric acid, and other operations and parameters are the same as in Example 1.

[0067] Comparative Example 3 Compared with Example 1, the only difference is that in step 2, the additives A and B are used, but ball milling is not performed, and the mixture containing the modified positive electrode powder of step 1, additives A and additives B is directly subjected to step 3 and subsequent treatments. Other operations and parameters are the same as in Example 1.

[0068] Comparative Example 4 Compared with Example 1, the only difference is that in step 2, the auxiliary agent B sodium carbonate is not added, the remaining amount of auxiliary agent A is the same as the total auxiliary agent in Example 1, and the other operations and parameters are the same as Example 1.

[0069] Comparative Example 5 Compared with Example 1, the only difference is that calcium chloride is not added, the amount of the remaining auxiliary agent B is the same as the total auxiliary agent in Example 1, and the other operations and parameters are the same as Example 1.

[0070] Comparative Example 6 Compared with Example 1, the only difference is that calcium chloride is replaced with an equal weight of calcium oxalate, and other operations and parameters are the same as Example 1.

[0071] The leaching data of valuable metal elements obtained in step (4) are shown in Table 2 below.

[0072]

[0073]

[0074] It can be seen from Table 3 that the method described in the present invention can obtain an excellent water leaching recovery rate. In addition, it can also obtain a regenerated material with both excellent capacity and first effect.

Claims

1. A method for preparing lithium iron phosphate positive electrode material from recycled waste LFP batteries, characterized in that: The positive electrode sheet disassembled from the waste LFP battery is placed in a modified stripping solution for modification and stripping, and the pre-treated material containing the waste LFP positive electrode material is collected; the stripping solution is an organic solution dissolved with an organic acid; The pre-treated material and the auxiliary agent are mechanically modified, and then calcined to obtain a calcined material; the auxiliary agent includes an auxiliary agent A and an auxiliary agent B, wherein the auxiliary agent A is CaCl2, and the auxiliary agent B is a sodium salt; The calcined material is subjected to water leaching to obtain an iron-lithium leaching solution; the iron-lithium leaching solution is subjected to alkali iron precipitation treatment to obtain iron slag and lithium liquid; the lithium liquid is subjected to lithium precipitation treatment to obtain lithium slag; The iron slag, lithium slag and phosphorus source are mixed and sintered to obtain the regenerated lithium iron phosphate positive electrode material.

2. The method for preparing the lithium iron phosphate positive electrode material from recycled waste LFP batteries according to claim 1, characterized in that: The modified stripping system also allows the addition of negative electrode sheets stripped from waste LFP batteries; Preferably, in the stripping solution, the organic acid comprises a C1-C6 fatty acid or a C2-C6 amine-containing fatty acid with an amino group, preferably at least one of formic acid, acetic acid, aminodiacetic acid, and ethylenediaminetetraacetic acid; Preferably, in the stripping solution, the concentration of the organic acid is 0.002-5%; Preferably, the organic solvent contained in the modified stripping solution includes at least one of NMP, DMF, DMSO, and C1-C4 alcohol; Preferably, the liquid-to-solid ratio in the modification and stripping stage is 1-10 mL / g.

3. The method for preparing the lithium iron phosphate positive electrode material from recycled waste LFP batteries according to claim 1, characterized in that: In the auxiliary agent B, the sodium salt includes at least one of sodium chloride, sodium carbonate and sodium bicarbonate; Preferably, the weight ratio of the pretreatment material to the auxiliary agent A and the auxiliary agent B is 1:2.2-2.8:0.02-0.5; Preferably, the mechanical modification is ball milling modification; Preferably, the rotation speed of mechanical modification is 100-300 rpm; Preferably, the time of mechanical modification is 0.5 to 1 h.

4. The method for preparing the lithium iron phosphate positive electrode material from recycled waste LFP batteries according to claim 1, characterized in that: The calcination temperature is 250~650℃ and the holding time is 2~10h.

5. The method for preparing the lithium iron phosphate positive electrode material from recycled waste LFP batteries according to claim 1, characterized in that: The liquid-to-solid ratio in the water immersion stage is 3-10 ml / g, the temperature in the water immersion stage is 25-60° C., and the water immersion time is 1-4 h.

6. The method for preparing the lithium iron phosphate positive electrode material from recycled waste LFP batteries according to claim 1, characterized in that: Adding alkaline components to the iron-lithium leaching solution and controlling the pH of the system to be 4-6, followed by solid-liquid separation to obtain iron slag; Preferably, the said component is at least one of ammonia water, sodium hydroxide and potassium hydroxide; Preferably, the iron slag is hydroxide slag of iron element; Preferably, the lithium precipitation treatment is a carbonation precipitation step; and the lithium slag is lithium carbonate.

7. The method for preparing lithium iron phosphate positive electrode material from recycled waste LFP batteries according to claim 1, characterized in that: The molar ratio of Li, Fe and P in the iron slag, lithium slag and phosphorus source is 1.01-1.05:1:1; Preferably, the sintering temperature is 500-800°C; Preferably, the sintering time is 5 to 15 hours.

8. A lithium iron phosphate positive electrode material obtained by the preparation method according to any one of claims 1 to 7 from recycled waste LFP batteries.

9. An application of lithium iron phosphate positive electrode material based on recycled waste LFP battery prepared by the preparation method according to any one of claims 1 to 7, characterized in that: It is used as positive electrode active material to prepare lithium iron phosphate batteries.

10. A lithium iron phosphate battery, characterized in that: The invention relates to a lithium iron phosphate positive electrode material comprising a recycled waste LFP battery obtained by the preparation method according to any one of claims 1 to 7.

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