Method for preparing lithium phosphate from waste lithium iron phosphate lithium extraction waste residue
By treating waste lithium iron phosphate residue through water leaching and alkaline leaching, high-value-added lithium phosphate is separated and prepared, solving the problem of the inability to utilize the waste residue as a resource and realizing pollution-free resource recycling.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHEASTERN UNIV CHINA
- Filing Date
- 2024-04-30
- Publication Date
- 2026-06-12
AI Technical Summary
In existing technologies, the waste residue from lithium iron phosphate extraction cannot be utilized as a resource, making its treatment an environmental problem. Furthermore, it contains harmful substances and cannot be directly treated as solid waste.
Waste lithium iron phosphate residue is treated using water leaching and alkaline leaching methods. The iron phosphate is decomposed by high-concentration potassium hydroxide solution, and the potassium phosphate is generated and enters the leaching solution. The iron hydroxide enters the leaching residue. Subsequently, lithium hydroxide is used to precipitate lithium phosphate. The calcined residue is used as a raw material for ironmaking, realizing the efficient utilization of resources.
This method enables the full utilization of waste lithium iron phosphate residue to produce high-value-added lithium phosphate. The process is simple, pollution-free, and has good prospects for industrial application.
Smart Images
Figure CN118343706B_ABST
Abstract
Description
Technical fields:
[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for preparing lithium phosphate from waste lithium iron phosphate extraction residue. Background technology:
[0002] Currently, lithium-ion batteries used in electric vehicles can be mainly divided into two types based on the cathode material used: nickel-cobalt-manganese ternary lithium batteries and lithium iron phosphate batteries. Lithium iron phosphate batteries account for 61% of the global installed capacity of power batteries. The design life of lithium-ion power batteries is generally 6-7 years, with some reaching 10 years. After a large number of lithium iron phosphate batteries reach the end of their life cycle, they need to be scrapped and recycled. Currently, the recycling of lithium iron phosphate batteries mainly uses the acid leaching method. This involves discharging, disassembling, crushing, and screening the battery, then leaching the lithium iron phosphate cathode material with dilute hydrochloric acid while simultaneously introducing CO2 gas, causing the Li in the solution to enter as Li2CO3. After purification, the Li resources are recovered. The lithium slag after acid leaching has a low Li content, and its main component is iron phosphate, resulting in low added value. However, due to the presence of harmful substances, it is not suitable for direct solid waste treatment. Currently, there is no reasonable utilization process for this waste lithium iron phosphate residue, and it is mostly disposed of by stockpiling. As early batches of electric vehicles are gradually scrapped in the coming years, the number of waste lithium iron phosphate power batteries will increase significantly. How to handle these waste power batteries, especially how to handle the waste lithium iron phosphate lithium extraction residue, will become one of the main problems facing the lithium battery recycling industry. Summary of the Invention:
[0003] The purpose of this invention is to provide a method for preparing lithium phosphate from waste lithium iron phosphate extraction residue, thereby solving the problem that waste lithium iron phosphate extraction residue cannot be utilized as a resource in the prior art.
[0004] The technical solution of this invention is:
[0005] A method for preparing lithium phosphate from waste lithium iron phosphate extraction residue includes the following steps:
[0006] (1) Dechlorination and desodium removal of waste lithium iron phosphate residue by water leaching
[0007] Waste lithium iron phosphate lithium extraction residue is added to deionized water and leached at a temperature of 20-100℃. The liquid-solid mass ratio during leaching is 15:1-5:1, and the leaching time is 0.5-2h. After leaching, the residue is filtered to obtain water leaching residue and primary leaching solution. Calcium chloride is added to the primary leaching solution, and the residue is separated by sedimentation and filtration. The separated leaching solution is returned to the leaching process for repeated use. The amount of calcium chloride added is based on the fluoride ion content in the primary leaching solution and is added according to the reaction theory required by equation (1), which is 95-100% of the required mass.
[0008] CaCl₂ + F - = CaF2 + Cl - (1)
[0009] (2) Separation of lithium iron phosphate waste residue by potassium hydroxide leaching
[0010] The water-leached residue was washed, dried, and ground to a particle size ≤0.15mm. It was then added to a potassium hydroxide aqueous solution for alkaline leaching. After leaching, the residue was filtered to obtain a secondary leachate and alkaline leaching residue. During the alkaline leaching process, the potassium hydroxide concentration was 120g / L~240g / L, the leaching temperature was 60~200℃, the leaching time was 0.5~10h, and the solid-liquid mass ratio of the leachate was 15:1~5:1.
[0011] The reaction that occurs during the alkaline leaching process is shown in equation (2):
[0012] FePO4+3KOH=K3PO4+Fe(OH)3 (2)
[0013] (3) Precipitation of lithium phosphate from secondary leachate
[0014] As shown in equation (3), lithium hydroxide powder is added to the secondary leachate for lithium precipitation. The lithium hydroxide dissolves into the secondary leachate and reacts with potassium phosphate in the secondary leachate to generate lithium phosphate. The lithium phosphate does not dissolve in the potassium hydroxide aqueous solution and forms crude lithium phosphate precipitate. After the lithium precipitation is completed, the tertiary leachate and crude lithium phosphate are obtained by filtration. Deionized water is added to the crude lithium phosphate and heated. After heating is completed, the solution is filtered and dried to obtain purified lithium phosphate and tertiary leachate.
[0015] During the lithium precipitation process, the added lithium hydroxide powder has a particle size ≤0.15mm and the amount added is 95-100% of the theoretical mass required by equation (3). The lithium precipitation temperature of the secondary leaching solution is 20-100℃. Deionized water is added to the crude lithium phosphate and heated and washed to achieve leaching purification. During the washing process of crude lithium phosphate, the temperature is 20-100℃ and the liquid-solid mass ratio is 10:1-2:1. The purified lithium phosphate is dried at a temperature of 100-200℃ for 1-10 hours.
[0016] K3PO4+LiOH=Li3PO4+KOH (3).
[0017] The method for preparing lithium phosphate from waste lithium iron phosphate residue includes step (1) leaching, in which mechanical stirring is used or the process is carried out in an ultrasonic environment.
[0018] In the method for preparing lithium phosphate from waste lithium iron phosphate residue, in step (1) during the leaching process, sodium and chlorine are completely introduced into the primary leaching solution, and soluble fluorine is introduced into the primary leaching solution.
[0019] In the method for preparing lithium phosphate from waste lithium iron phosphate residue, during the alkaline leaching process in step (2), the iron phosphate phase decomposes, phosphorus enters the secondary leaching solution in the form of potassium phosphate, and iron enters the alkaline leaching residue in the form of iron hydroxide.
[0020] In the method for preparing lithium phosphate from waste lithium iron phosphate extraction residue, during the alkaline leaching process in step (2), other impurities such as carbon, alumina, copper, and insoluble fluorine in the waste lithium iron phosphate extraction residue enter the alkaline leaching residue, thereby achieving the separation of phosphorus from iron and other impurities.
[0021] In the method for preparing lithium phosphate from waste lithium iron phosphate residue, step (2) involves the following treatment process for the alkaline leaching residue:
[0022] After being washed and dried, the alkali leaching residue is calcined at a temperature of 500-1100℃. During the calcination process, iron hydroxide decomposition and reduction reactions occur, as shown in equations (4), (5) and (6). The reduced product is directly used as a raw material for ironmaking.
[0023]
[0024]
[0025]
[0026] The method for preparing lithium phosphate from waste lithium iron phosphate residue, in step (3) during the lithium precipitation process, the required lithium hydroxide is added in 3 to 6 batches.
[0027] In the method for preparing lithium phosphate from waste lithium iron phosphate residue, in step (3) during the lithium precipitation process, lithium hydroxide powder with a particle size of 0.075 to 0.15 mm is added to the secondary leachate.
[0028] The method for preparing lithium phosphate from waste lithium iron phosphate residue includes the following process in step (3): adding fourth leaching solution to the third leaching solution, adjusting the potassium hydroxide concentration so that the potassium hydroxide concentration of the adjusted solution reaches the concentration range of the second leaching solution, and then returning it to the potassium hydroxide leaching process as the leaching solution for water leaching residue, thereby realizing the recycling of potassium hydroxide solution.
[0029] The design concept of this invention is:
[0030] This invention uses waste lithium iron phosphate extraction residue as raw material and high-concentration potassium hydroxide solution as leaching solution for leaching. This decomposes the iron phosphate in the lithium extraction residue, and phosphorus enters the leaching solution in the form of potassium phosphate. Iron oxide enters the leaching residue in the form of iron hydroxide. After purification, lithium hydroxide is added to the leaching solution for precipitation to obtain lithium phosphate. The leaching residue is then heated and decomposed for use as a raw material for iron smelting.
[0031] Waste lithium iron phosphate (LFP) extraction residue often contains impurities such as chlorine, fluorine, and sodium. Chlorine and sodium are typically soluble and mainly enter the residue due to insufficient washing after lithium extraction. These impurities must be removed before potassium hydroxide leaching; otherwise, they will enter the leaching solution. The primary method for removing chlorine and sodium is water leaching.
[0032] During the alkaline leaching process, the ferric phosphate phase decomposes, with phosphorus entering the secondary leaching solution as potassium phosphate, and iron entering the alkaline leaching residue as ferric hydroxide. Furthermore, during the leaching process, other impurities such as carbon, alumina, copper, and insoluble fluorine from the waste lithium iron phosphate extraction residue also enter the alkaline leaching residue, thus achieving the separation of phosphorus from iron and other impurities.
[0033] The advantages and beneficial effects of this invention are:
[0034] The method for preparing lithium phosphate using waste lithium iron phosphate extraction residue of the present invention not only realizes the full utilization of the waste lithium iron phosphate extraction residue, but also produces high-value-added lithium phosphate. The entire process is simple, generates no waste, and is pollution-free. It is a high-value-added method for treating waste lithium iron phosphate extraction residue and has good prospects for industrial application. Attached image description:
[0035] Figure 1 This is a process flow diagram for preparing lithium phosphate from waste lithium iron phosphate extraction residue of the present invention. Detailed implementation method:
[0036] like Figure 1 As shown, the process flow for preparing lithium phosphate from waste lithium iron phosphate extraction residue of the present invention is as follows:
[0037] The main components of waste lithium iron phosphate extraction residue are iron phosphate and carbon. In addition, it also contains small amounts of impurities such as aluminum oxide, copper, fluorides, and chlorides. Using waste lithium iron phosphate extraction residue as raw material, water leaching and mechanical stirring are carried out to form water-leached residue. After leaching, the residue and primary leachate are obtained by filtration. Calcium chloride is added to the primary leachate, followed by sedimentation and filtration separation. The separated leachate is returned to the leaching process for repeated use.
[0038] The water-leached residue is washed, dried, and ground, then added to a potassium hydroxide solution for alkaline leaching. After leaching, the residue is filtered to obtain a secondary leachate and alkaline leaching residue. The alkaline leaching residue is then washed, dried, and calcined. During calcination, ferric hydroxide decomposes and is reduced. The reduced product is directly used as a raw material for iron smelting.
[0039] Lithium hydroxide powder is added to the secondary leachate to precipitate lithium, forming lithium phosphate precipitate. The precipitate is then filtered to obtain the tertiary leachate and crude lithium phosphate. The crude lithium phosphate is purified by leaching, and filtered to obtain pure lithium phosphate and the quaternary leachate. The quaternary leachate is mixed with the tertiary leachate and returned to the lithium iron phosphate leaching process for use as leachate.
[0040] The present invention will now be described in further detail with reference to the embodiments.
[0041] Example 1
[0042] In this embodiment, the main components of the waste lithium iron phosphate extraction residue are TFe 33.00%, P 30.35%, C 15.00%, Al2O3 0.77%, Cu <0.01%, Cl 0.03%, F 0.10%, with the remainder mainly consisting of oxygen and water.
[0043] Waste lithium iron phosphate residue was added to deionized water and leached at 80°C. Mechanical stirring was used during the leaching process. The liquid-to-solid mass ratio during leaching was 5:1, and the leaching time was 0.5 h. After leaching, the residue and primary leachate were obtained by filtration. Calcium chloride was added to the primary leachate, and the residue was separated by sedimentation and filtration. The separated leachate was returned to the leaching process for repeated use. The amount of calcium chloride added was 100% of the theoretical mass required by equation (1).
[0044] The water-leached residue was washed, dried, and ground to a particle size ≤0.15mm. It was then added to a potassium hydroxide aqueous solution for alkaline leaching. After leaching, the residue was filtered to obtain a secondary leachate and alkaline leaching residue. During the alkaline leaching process, the potassium hydroxide concentration was 150g / L, the leaching temperature was 80℃, the leaching time was 2h, and the solid-to-liquid mass ratio was 5:1.
[0045] After washing and drying, the alkali leaching residue is calcined at 600℃. During the calcination process, ferric hydroxide decomposes and is reduced. The composition of the residue after the reaction is: TFe 58%, P 0.35%, C 12.05%, Al2O3 1.27%, Cu <0.01%, Cl 0.01%, F 0.11%, with the balance mainly being oxygen. The reduced product is directly used as a raw material for ironmaking.
[0046] Lithium hydroxide powder with a particle size of 0.075–0.15 mm was added to the secondary leachate and reacted at 80°C to generate lithium phosphate precipitate. The precipitate was then filtered to obtain the tertiary leachate and crude lithium phosphate. The amount of lithium hydroxide added was 95% of the theoretical mass required by equation (3). Deionized water was added to the crude lithium phosphate and heated. The crude lithium phosphate was washed at 80°C and a liquid-to-solid mass ratio of 5:1 to achieve leaching purification. After washing, the precipitate was filtered and dried at 150°C for 2 hours to obtain pure lithium phosphate product. In this embodiment, the purity of the pure lithium phosphate was above 99 wt%.
[0047] In addition, the third leaching solution and the crude lithium phosphate washing solution (fourth leaching solution) are mixed and returned to the lithium iron phosphate leaching process as leaching solution.
Claims
1. A method for preparing lithium phosphate from waste lithium iron phosphate extraction residue, characterized in that, Includes the following steps: (1) Water leaching dechlorination and desodium removal of waste lithium iron phosphate lithium extraction residue Waste lithium iron phosphate lithium extraction residue is added to deionized water and leached at a temperature of 20~100℃. The liquid-solid mass ratio during the leaching process is 15:1~5:1, and the leaching time is 0.5~2h. After leaching, the water leaching residue and primary leaching solution are obtained by filtration. Calcium chloride is added to the primary leaching solution, and the solution is separated by sedimentation and filtration. The separated leaching solution is returned to the leaching process for repeated use. The amount of calcium chloride added is based on the fluoride ion content in the primary leaching solution and is added according to the reaction theory required by equation (1), which is 95~100% of the required mass. CaCl2+2F - = CaF2+2Cl - (1) (2) Separation of lithium iron phosphate residue by potassium hydroxide leaching The water-leached residue was washed, dried, and ground to a particle size ≤0.15mm. It was then added to a potassium hydroxide aqueous solution for alkaline leaching. After leaching, the residue was filtered to obtain a secondary leachate and alkaline leaching residue. During the alkaline leaching process, the potassium hydroxide concentration was 120 g / L~240 g / L, the leaching temperature was 60~200℃, the leaching time was 0.5~10 h, and the solid-liquid mass ratio of the leachate was 15:1~5:
1. The reaction that occurs during the alkaline leaching process is shown in equation (2): （2） (3) Precipitation of lithium phosphate in secondary leachate As shown in equation (3), lithium hydroxide powder is added to the secondary leachate for lithium precipitation. The lithium hydroxide dissolves into the secondary leachate and reacts with potassium phosphate in the secondary leachate to generate lithium phosphate. The lithium phosphate does not dissolve in the potassium hydroxide aqueous solution and forms crude lithium phosphate precipitate. After the lithium precipitation is completed, the tertiary leachate and crude lithium phosphate are obtained by filtration. Deionized water is added to the crude lithium phosphate and heated. After heating is completed, the solution is filtered and dried to obtain purified lithium phosphate and tertiary leachate. During the lithium precipitation process, the added lithium hydroxide powder has a particle size ≤0.15mm and the amount added is 95~100% of the theoretical mass required by equation (3). The lithium precipitation temperature of the secondary leaching solution is 20~100℃. Deionized water is added to crude lithium phosphate and heated and washed to achieve leaching purification. During the washing process of crude lithium phosphate, the temperature is 20~100℃ and the liquid-solid mass ratio is 10:1~2:
1. The purified lithium phosphate is dried at a temperature of 100~200℃ for 1~10 h. （3）； The process of treating the third leaching solution in step (3) is as follows: the fourth leaching solution is added to the third leaching solution, the potassium hydroxide concentration is adjusted so that the potassium hydroxide concentration of the adjusted solution reaches the concentration range of the second leaching solution, and then it is returned to the potassium hydroxide leaching process as the leaching solution of the water leaching residue, so as to realize the recycling of potassium hydroxide solution.
2. The method for preparing lithium phosphate from waste lithium iron phosphate extraction residue according to claim 1, characterized in that, In step (1), mechanical stirring or ultrasonic stirring is used during the leaching process.
3. The method for preparing lithium phosphate from waste lithium iron phosphate extraction residue according to claim 1, characterized in that, In step (1), during the leaching process, sodium and chlorine are completely introduced into the primary leaching solution, and soluble fluorine is also introduced into the primary leaching solution.
4. The method for preparing lithium phosphate from waste lithium iron phosphate extraction residue according to claim 1, characterized in that, In step (2), during the alkaline leaching process, the ferric phosphate phase decomposes, phosphorus enters the secondary leaching solution in the form of potassium phosphate, and iron enters the alkaline leaching residue in the form of ferric hydroxide.
5. The method for preparing lithium phosphate from waste lithium iron phosphate extraction residue according to claim 1, characterized in that, In step (2), during the alkaline leaching process, other impurities such as carbon, alumina, copper, and insoluble fluorine in the waste lithium iron phosphate extraction residue enter the alkaline leaching residue, thereby achieving the separation of phosphorus from iron and other impurities.
6. The method for preparing lithium phosphate from waste lithium iron phosphate extraction residue according to claim 1, characterized in that, In step (2), the treatment process for the alkali leaching residue is as follows: After being washed and dried, the alkali leaching residue is calcined at a temperature of 500~1100℃. During the calcination process, iron hydroxide decomposition and reduction reactions occur, as shown in equations (4), (5) and (6). The reduced product is directly used as a raw material for ironmaking. （4） （5） （6）。 7. The method for preparing lithium phosphate from waste lithium iron phosphate extraction residue according to claim 1, characterized in that, In step (3) during the lithium precipitation process, the required lithium hydroxide is added in 3 to 6 portions.
8. The method for preparing lithium phosphate from waste lithium iron phosphate extraction residue according to claim 1, characterized in that, In step (3) during the lithium precipitation process, lithium hydroxide powder with a particle size of 0.075~0.15mm is added to the secondary leachate.