Regeneration of lithium iron phosphate anode material from waste lithium iron phosphate battery and preparation and application thereof

Abstract

The present application relates to the field of waste battery recycling, and particularly relates to a preparation method of a regenerated lithium iron phosphate positive electrode material from waste LFP batteries, wherein the positive electrode sheet disassembled from the waste LFP batteries is placed in a modified stripping solution for modified stripping, and pretreated materials containing the waste LFP positive electrode material are collected; the stripping solution is an organic solution in which an organic acid is dissolved; the pretreated materials and an additive are mechanically modified, and then subjected to calcination treatment to obtain calcined materials; the additive includes additive A and additive B, wherein the additive A is CaCl2, and the additive B is a sodium salt; the calcined materials are subjected to water immersion treatment to obtain an iron lithium leaching solution; the iron lithium leaching solution is subjected to iron precipitation treatment to obtain iron residue and lithium liquid, and the lithium liquid is subjected to lithium precipitation treatment to obtain lithium residue; the iron residue and the lithium residue are mixed and subjected to sintering treatment together with a phosphorus source to obtain the regenerated lithium iron phosphate positive electrode material. The method has excellent metal recovery rate, and in addition, has excellent regeneration performance.

Description

Technical Field

[0001] The present invention belongs to the field of battery waste recycling, and in particular 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 development of ternary cathode materials, lithium iron phosphate (LiFePO4) cathode materials have rapidly developed and become a key competitive advantage in LiFePO4 cathode materials. However, LiFePO4 batteries have a lifespan of only 5–8 years, resulting in a large amount of waste. The high amount of valuable elements contained in these batteries, if not recovered, would result in significant resource waste and environmental pollution. Currently, pyrometallurgy and hydrometallurgy are the primary methods for treating spent LiFePO4 batteries.

[0003] For example, the patent document with publication number WO2024212075A1 discloses a method for repairing and regenerating lithium iron phosphate, and its regeneration steps are: crushing, soaking, screening, ball milling, and sorting the waste lithium iron phosphate electrodes to obtain waste lithium iron phosphate electrode powder, and then roasting the waste lithium iron phosphate electrode powder in a carbon dioxide atmosphere at 750-900°C. After the obtained roasting product and water are evenly stirred, carbon dioxide is introduced, and the reaction mixture is spray granulated to obtain a lithium iron phosphate precursor; finally, the obtained lithium iron phosphate precursor is calcined to obtain regenerated lithium iron phosphate. For another example, Chinese patent document CN118666259A discloses a method for recycling and regenerating waste lithium iron phosphate batteries, which includes: placing the waste lithium iron phosphate battery positive electrode black powder in a roasting furnace filled with protective gas for a roasting reaction, and adjusting the input chlorine flow rate based on the mixture in the roasting 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, the existing technology has some methods for calcination-water leaching to recover and regenerate lithium iron phosphate, but the processing temperature of the existing process is relatively high, and the water leaching conditions lack mildness. Moreover, the existing technology 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 response to 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 the 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 obtained 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 cathode material regenerated from waste LFP batteries comprises placing cathode sheets disassembled from waste LFP batteries in a modification and stripping solution for modification and stripping, and collecting a pretreated material containing the waste LFP cathode material; the stripping solution is an organic solution containing an organic acid;

[0009] The pretreated material and the auxiliary agent are mechanically modified and then calcined to obtain a calcined material; the auxiliary agent includes auxiliary agent A and auxiliary agent B, wherein the auxiliary agent A is CaCl2 and the auxiliary agent B is a sodium salt;

[0010] 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;

[0011] The iron slag, lithium slag and phosphorus source are mixed and sintered to prepare the regenerated lithium iron phosphate positive electrode material.

[0012] This invention innovatively places the positive electrode sheet in the modified stripping solution for stripping and simultaneous surface modification, and further combines this with the subsequent synergistic mechanical modification of additives A and B. This facilitates low-temperature calcination and improves subsequent water leaching. It also regulates the simultaneous leaching and accompanying precipitation of beneficial components that contribute to regenerative electrochemical performance. Research conducted by the present invention demonstrates that this process can achieve excellent recovery rates and, in addition, superior regenerative electrochemical performance.

[0013] 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.

[0014] In the present invention, the waste LFP batteries can be obtained by disassembling based on known processes.

[0015] In the present invention, the modified stripping system is also allowed to add negative electrode sheets stripped from waste LFP batteries.

[0016] In the present invention, the organic acid in the stripping solution includes a C1-C6 fatty acid or a C2-C6 amine-containing fatty acid with an amino group, and may further be at least one of formic acid, acetic acid, aminodiacetic acid, and ethylenediaminetetraacetic acid; acetic acid is more preferably used. Research in this invention has shown that combining acetic acid with other processes can achieve enhanced synergy, further improving material recovery and regeneration performance.

[0017] 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.

[0018] Preferably, the organic solvent contained in the modified stripping solution includes at least one of NMP, DMF, DMSO, and C1-C4 alcohols.

[0019] Preferably, the liquid-to-solid ratio in the modification and stripping stage is 1-10 mL / g.

[0020] In the present invention, the sodium salt in the additive B includes at least one of sodium chloride, sodium carbonate, and sodium bicarbonate; preferably sodium carbonate. Studies in the present invention have shown that combining sodium carbonate with other processes can achieve better synergy, further improving the recovery rate and regeneration performance of the material.

[0021] 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.

[0022] Preferably, the mechanical modification is ball milling modification.

[0023] Preferably, the rotation speed of the mechanical modification is 100-300 rpm.

[0024] Preferably, the mechanical modification time is 0.5 to 1 h.

[0025] In the present invention, the calcination temperature is 250-650° C., further 350-550° C., further 400-500° C., and the holding time is 2-10 hours, further 2-3 hours.

[0026] 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 hours, and can further be 1-1.5 hours.

[0027] In the present invention, an alkaline component is added to the iron-lithium leaching solution, and the pH of the system is controlled to be 4-6, followed by solid-liquid separation to obtain iron slag.

[0028] Preferably, the said component is at least one of ammonia water, sodium hydroxide and potassium hydroxide.

[0029] Preferably, the iron slag is hydroxide slag of iron element.

[0030] Preferably, the lithium precipitation treatment is a carbonation precipitation step; and the lithium slag is lithium carbonate.

[0031] 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.

[0032] 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.

[0033] Preferably, the sintering temperature is 500-800°C, and further can be 650-750°C.

[0034] Preferably, the sintering time is 5 to 15 hours, and further can be 9 to 11 hours.

[0035] 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 can be sugar, polymer, asphalt, etc.

[0036] 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.%.

[0037] The present invention also provides a lithium iron phosphate positive electrode material obtained by the preparation method of waste LFP batteries.

[0038] 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.

[0039] The present invention also provides the use of the lithium iron phosphate positive electrode material based on the recycled waste LFP battery prepared by the preparation method, which is used as a positive electrode active material for preparing a lithium iron phosphate battery.

[0040] 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.

[0041] The lithium iron phosphate battery of the present invention may contain, in addition to the regenerated lithium iron phosphate material of the present invention, other components and structural parts of the battery may be known.

[0042] Beneficial effects

[0043] 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. This 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

[0044] Figure 1 This is the XRD pattern of the lithium carbonate of Example 1.

[0045] Figure 2 This is the electrochemical performance diagram of the regenerated lithium iron phosphate in Example 1. DETAILED DESCRIPTION

[0046] The present invention will be further described in detail below with reference to specific examples, but the present invention is not limited to the following examples.

[0047] In the present invention, there is no special requirement for the active material content in the waste lithium-ion battery positive electrode material. Considering the economic efficiency of the process, the content is preferably above 50 wt.%. In the following cases, unless otherwise stated, the active material content is 85-90 wt.%.

[0048] The present invention provides an optional method for regenerating waste lithium iron phosphate batteries, comprising the following steps:

[0049] Step (1): Preprocessing

[0050] 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;

[0051] Step (2): Abrasive

[0052] After the pre-treated material is evenly mixed with additives A and B, the mixture is placed in a ball mill for ball milling;

[0053] Step (3): Calcination

[0054] The abrasive is placed in an atmosphere furnace for calcination and then cooled to room temperature.

[0055] Step (4): Water Soaking

[0056] The calcined material is dispersed in deionized water, stirred at a certain temperature for a period of time, and solid-liquid separation is performed.

[0057] Step (5): Precipitation

[0058] Take the filtrate obtained in the previous step, add alkaline components to adjust the pH to 4~6, separate the solid and liquid, precipitate and dry to obtain iron slag, add Na2CO3 to the filtrate and evaporate and crystallize to obtain Li2CO3 (lithium slag).

[0059] Step (6): Regeneration

[0060] The iron slag precipitate obtained in the previous step is mixed evenly with Li2CO3 and phosphorus source (NH4H2PO4) and then annealed at 500~800℃ for 5~15h to obtain a regenerated positive electrode.

[0061] In 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%.

[0062] 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.

[0063] The calcination atmosphere in step 3 is one of argon, hydrogen, and air, the heating rate is 2 to 10°C / min, the holding temperature is 250 to 650°C, and the holding time is 2 to 10 hours.

[0064] The liquid-to-solid ratio in the stirred 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.

[0065] 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.

[0066] Example 1:

[0067] Step 1 Peeling:

[0068] Waste power lithium iron phosphate batteries were placed in a 2 mol / L NaCl solution for 30 h of discharge treatment. The discharged batteries were dried at 85°C and disassembled to separate the positive and negative electrodes. The positive electrodes were immersed in a mixture of N-methylpyrrolidone and ethanol with a volume ratio of 1:10 (liquid-to-solid ratio of 2 mL / g) and 0.05% by volume of acetic acid was added. Ultrasonic treatment was performed to separate the current collector from the electrode. After removing the aluminum foil, the black powder was filtered, washed with water, and dried to obtain waste positive electrode powder (modified positive electrode powder).

[0069] Step 2: Ball milling:

[0070] 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) at a mass ratio of 0.02:1. Set the speed to 250 rpm and ball mill for 1 hour.

[0071] Step 3: Firing:

[0072] The ball mill 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 2 hours.

[0073] Step 4 Leaching:

[0074] The calcined material was 10:1 mL g -1 Deionized water was added to the solution at a liquid-to-solid ratio, followed by 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.

[0075] Step 5: Stepwise precipitation:

[0076] 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 pattern is shown in the attached figure. Figure 1 shown.

[0077] Step 6 Regeneration:

[0078] 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 mixed evenly 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.

[0079] Example 2:

[0080] Compared with Example 1, the only difference is that the conditions of step 1 are changed, specifically:

[0081] Group A: Changed the type of organic acid to formic acid;

[0082] Group B: The solvent in the stripping modification solution is a mixed solvent of DMF and ethanol with a volume ratio of 1:15, the concentration of the organic acid is 0.1%, and the stripping liquid-solid ratio is 1 mL / g.

[0083] Other operations and parameters are the same as in Example 1.

[0084] Example 3

[0085] Compared with Example 1, the only difference is that the conditions of step 2 are changed, specifically:

[0086] Group A: The type of additive B was changed to sodium chloride;

[0087] Group B: The mass ratio of additive A (calcium chloride) to waste positive electrode material is 2.5:1, the mass ratio of additive B to waste positive electrode material is 0.5:1, the ball milling time is 0.5h, and the rotation speed is 300rpm.

[0088] Other operations and parameters are the same as in Example 1.

[0089] Example 4

[0090] 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 3 hours; in addition, in step 4, the water immersion temperature is 30°C, the water immersion liquid-to-solid ratio is 5 ml / g, and the time is 1.5 hours.

[0091] The data obtained in step (4) are shown in Table 1 below.

[0092]

[0093] 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 combined roasting of auxiliary agents A and B, can achieve efficient recovery and utilization of iron and lithium.

[0094] Comparative Example 1

[0095] 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.

[0096] Comparative Example 2

[0097] 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.

[0098] Comparative Example 3

[0099] Compared with Example 1, the only difference is that in step 2, the aforementioned additives A and B are used, but ball milling is not performed. Instead, the mixture containing the modified positive electrode powder, additives A, and additives B from step 1 is directly subjected to step 3 and subsequent treatments. Other operations and parameters are the same as in Example 1.

[0100] Comparative Example 4

[0101] 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.

[0102] Comparative Example 5

[0103] Compared with Example 1, the only difference is that calcium chloride is not added, the remaining amount of auxiliary agent B is the same as the total auxiliary agent in Example 1, and other operations and parameters are the same as Example 1.

[0104] Comparative Example 6

[0105] Compared with Example 1, the only difference is that calcium chloride is replaced by an equal weight of calcium oxalate, and other operations and parameters are the same as in Example 1.

[0106] The leaching data of valuable metal elements obtained in step (4) are shown in Table 2 below.

[0107]

[0108]

[0109] As shown in Table 3, the method described in the present invention can obtain an excellent water leaching recovery rate. In addition, it can also obtain a recycled material with both excellent capacity and first efficiency.

Claims

1. A method for preparing lithium iron phosphate positive electrode material from recycled waste LFP batteries, characterized in that: The positive electrode sheets disassembled from the waste LFP batteries are placed in a modification stripping solution for modification and stripping, and a 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 pretreated material and the auxiliary agent are mechanically modified and then calcined to obtain a calcined material; the auxiliary agent includes auxiliary agent A and auxiliary agent B, wherein the auxiliary agent A is CaCl2 and the auxiliary agent B is sodium salt; the mechanical modification is ball milling modification; 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 prepare the regenerated lithium iron phosphate positive electrode material.

2. The method for preparing a lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: The modified stripping system is further added with negative electrode sheets stripped from waste LFP batteries.

3. The method for preparing a lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: 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.

4. The method for preparing a lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 3, wherein: The organic acid is at least one of formic acid, acetic acid, aminodiacetic acid, and ethylenediaminetetraacetic acid.

5. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 3, wherein: In the stripping solution, the volume concentration of the organic acid is 0.002-5%.

6. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: The organic solvent contained in the modified stripping solution includes at least one of NMP, DMF, DMSO, and C1-C4 alcohols.

7. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: The liquid-to-solid ratio in the modification and stripping stage was 1~10 mL / g.

8. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: In the auxiliary agent B, the sodium salt includes at least one of sodium chloride, sodium carbonate, and sodium bicarbonate.

9. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: 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.

10. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, characterized in that: The rotation speed of mechanical modification is 100~300rpm.

11. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, characterized in that: The time of mechanical modification is 0.5~1h.

12. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: The calcination temperature is 250~650℃ and the holding time is 2~10h.

13. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: 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.

14. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, wherein: An alkaline component is added to the iron-lithium leaching solution, and the pH of the system is controlled to be 4-6, followed by solid-liquid separation to obtain iron slag.

15. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 14, characterized in that: The alkaline component is at least one of ammonia water, sodium hydroxide and potassium hydroxide.

16. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 14, characterized in that: The iron slag is hydroxide slag of iron element.

17. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, characterized in that: The lithium precipitation process is a carbonation precipitation step; the lithium slag is lithium carbonate.

18. The method for preparing lithium iron phosphate cathode 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.

19. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, characterized in that: The sintering temperature is 500~800℃.

20. The method for preparing lithium iron phosphate cathode material from recycled waste LFP batteries according to claim 1, characterized in that: The sintering time is 5~15h.

21. A lithium iron phosphate cathode material obtained by the preparation method according to any one of claims 1 to 20, which is recycled from waste LFP batteries.

22. An application of a lithium iron phosphate cathode material made from recycled waste LFP batteries obtained by the preparation method according to any one of claims 1 to 20, characterized in that: It is used as a positive electrode active material to prepare lithium iron phosphate batteries.

23. A lithium iron phosphate battery, characterized in that: The invention relates to a lithium iron phosphate positive electrode material comprising recycled waste LFP batteries prepared by the preparation method according to any one of claims 1 to 20.

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