Method for selectively extracting lithium from waste lithium iron phosphate positive electrode material based on interface polarization activation-complexing impurity inhibition

Abstract

The invention belongs to the technical field of waste lithium battery recovery, and particularly relates to a method for selectively extracting lithium from a waste lithium iron phosphate positive electrode material based on interface polarization activation-complexing impurity inhibition, which comprises the following steps: 1) adding the waste lithium iron phosphate positive electrode material, an oxidizing agent and an activating agent into a solvent, stirring and leaching, and carrying out solid-liquid separation after leaching to obtain a leaching solution; and (2) adding inorganic salt into the leachate, enabling the inorganic salt and the activating agent in the step (S1) to generate precipitate, and carrying out solid-liquid separation to obtain a lithium-rich solution. Through the synergistic effect of the activating agent and the oxidizing agent, the lithium is deintercalated while the main body of the waste lithium iron phosphate positive electrode material is not dissolved basically, the leaching rate of the lithium can reach 99% or above, and the content of iron and phosphorus impurities in the lithium-rich solution is low. The method has the advantages of being high in lithium leaching rate, good in lithium selectivity, wide in leaching temperature application range, short in technological process, few in generated waste and low in cost, and particularly, the method also has the excellent selective lithium leaching effect at the low temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste lithium battery recycling, and specifically relates to a method for selectively extracting lithium from waste lithium iron phosphate positive electrode materials based on interface polarization activation-complexation suppression. Background Art

[0002] Over the past decade, with the rapid development of the new energy vehicle and energy storage industries, lithium iron phosphate (LiFePO4) batteries have been widely used, with their market share increasing annually. Currently, LiFePO4 holds over 50% of the market share. LiFePO4 batteries have a lifespan of approximately eight years, so their widespread use leads to a large number of retired batteries. Reportedly, the number of retired LiFePO4 batteries has increased dramatically in recent years. Failure to recycle these batteries results in not only a waste of resources but also serious environmental pollution. Therefore, efficient recycling of spent LiFePO4 batteries has become a key issue for the industry.

[0003] At present, the traditional mainstream method for recycling lithium iron phosphate is the wet process. Although the wet process can achieve lithium extraction, it has problems such as severe co-dissolution of iron and phosphorus, complex subsequent separation steps, low lithium loss and recovery rate, and the generation of large amounts of phosphorus-containing wastewater. Although pyrometallurgy can process large quantities of raw materials, the high-temperature roasting process has high energy consumption and is prone to lithium volatilization loss, resulting in poor economic and environmental performance. The direct regeneration process requires the replenishment of lithium sources and is only suitable for batteries that are not severely aged, which restricts the recycling efficiency of lithium resources. Therefore, the development of an efficient and low-cost selective lithium extraction technology to achieve precise separation of lithium from iron and phosphorus and short-process lithium recovery is of great significance to promoting the sustainable development of the lithium battery recycling industry.

[0004] Chinese patent application publication number CN107546436A discloses a method for recovering lithium from lithium iron phosphate, which involves mixing lithium iron phosphate powder with sodium persulfate solution and obtaining a lithium-rich solution through solid-liquid separation. Although this method has the advantages of selective lithium extraction and high lithium element separation efficiency, it uses too much sodium persulfate and requires heating, resulting in a low solid-liquid ratio, large wastewater volume, and high energy consumption. Chinese patent application publication number CN118561297A discloses a method for recovering lithium and iron phosphate from waste lithium iron phosphate, which involves passing gas Cl2 into lithium iron phosphate slurry after high-temperature dilute acid washing and impurity removal, and simultaneously adding catalyst FeCl3, and crystallizing the lithium-containing solution to obtain lithium chloride. This method uses Cl2 and FeCl3, which is dangerous, costly, and difficult to treat chlorine-containing wastewater. At the same time, the method involves high-temperature dilute acid impurity removal, which can lead to increased costs and lithium element loss. Chinese patent application CN118343718A discloses a method for recovering lithium iron phosphate by oxidative leaching of ferrate. This method utilizes ferrate containing hexavalent Fe (e.g., Na2FeO4, K2FeO4) as an oxidant, employs an acetic acid-sodium acetate buffer solution, and maintains the solution pH at 3-5 to selectively extract lithium from lithium iron phosphate. However, this method suffers from drawbacks such as the high cost of the ferrate, the need for a buffer solution, and the introduction of additional impurity iron ions, making industrial application difficult. Therefore, there is a need to develop a new process for extracting lithium from spent lithium iron phosphate batteries. Summary of the Invention

[0005] The present invention aims to provide a method for selective lithium extraction from waste lithium iron phosphate positive electrode materials based on interfacial polarization activation-complexation suppression, so as to solve the problems of low lithium recovery rate, low lithium leaching selectivity, high cost, complicated process flow and large environmental pollution in waste lithium iron phosphate positive electrode materials in the prior art.

[0006] In order to achieve the above object, the present invention provides a method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression, comprising the following steps:

[0007] S1, adding waste lithium iron phosphate positive electrode material, oxidant and activator to the solvent, stirring and leaching, and separating the solid and liquid after the leaching is completed to obtain a leachate;

[0008] S2. Adding an inorganic salt to the leachate obtained in step S1, the inorganic salt and the activator in step S1 form a precipitate, and obtaining a lithium-rich solution after solid-liquid separation.

[0009] The working principle and beneficial effects of this solution are as follows: Through the synergistic effect of an activator and an oxidant, lithium is deintercalated without dissolving the host material, and the lithium leaching solution can reach a maximum of over 99%. After the leaching is completed, a small amount of specific inorganic salts is introduced to form stable complexes with impurities in the leachate, significantly reducing the impurity content in the leachate and creating favorable conditions for subsequent lithium extraction. Furthermore, it is worth mentioning that this solution is applicable at room temperature or even low temperatures (1-40°C), adapting to ambient temperature changes. The process does not require heating, reducing energy consumption.

[0010] Compared with the traditional wet process, this solution does not require the use of inorganic acid and hydrogen peroxide to extract lithium, effectively reducing the cost of reagents. In addition, this solution basically does not dissolve the main body of waste lithium iron phosphate positive electrode materials, the lithium leaching rate is high, the content of iron and phosphorus impurities in the leachate is controllable, and there is no need to consume a large amount of alkaline reagents to adjust the pH for impurity removal. While further reducing the cost of reagents, it avoids the loss of lithium during the impurity removal process, has good lithium selectivity, and produces less waste. Not only that, this solution is simple to operate, has a short process flow, and can be directly operated under existing process equipment without the need for additional equipment investment. In summary, this solution has significant environmental and economic advantages, realizes the green, efficient and low-cost extraction of lithium from waste lithium iron phosphate positive electrode materials, has good industrial prospects, and is expected to provide a reliable solution for the large-scale resource utilization of retired lithium iron phosphate batteries.

[0011] Optionally, in step S1, the oxidant is one or more of sodium percarbonate, sodium perborate, sodium hypochlorite, calcium hypochlorite, sodium perchlorate, potassium perchlorate, sodium chlorate, sodium chlorite, ammonium peroxodisulphate, sodium peroxodisulphate and potassium peroxodisulphate.

[0012] Optionally, in step S1, the activator is one or more of a divalent ferrous salt, a divalent cobalt salt, a divalent manganese salt, a divalent copper salt and a monovalent silver salt.

[0013] Optionally, in step S2, the inorganic salt is one or more of hydroxide, sulfide, carbonate, phosphate, halide, etc.

[0014] Optionally, in step S1, the ratio of waste lithium iron phosphate positive electrode material to solvent is 20-200 g:1 L.

[0015] Optionally, in step S1 , the amount of the oxidant added is 20-200% of the mass of the waste lithium iron phosphate positive electrode material.

[0016] Optionally, in step S1, the amount of the activator added is 1 to 50% of the mass of the waste lithium iron phosphate positive electrode material.

[0017] Optionally, in step S2, the molar amount of the inorganic salt added is 0.8 to 1.5 times the molar amount of the metal ions in the activator.

[0018] Optionally, in step S1, the leaching reaction temperature is 1-40°C, the leaching reaction time is 60-180 minutes, and the leaching stirring speed is 300-800 rpm.

[0019] Optionally, in step S2, the reaction temperature is 30-90°C, the reaction time is 60-180 min, and the stirring speed is 300-800 rpm.

[0020] Optionally, in step S1, the waste lithium iron phosphate positive electrode material is a positive electrode powder material with a particle size of 20 to 200 μm obtained by disassembling, crushing, cleaning and drying waste lithium iron phosphate batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic flow chart of a method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0023] The present invention provides a method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression, comprising the following steps:

[0024] S1. Add waste lithium iron phosphate positive electrode material, an oxidant, and an activator to a solvent, stir and leach, and after leaching, perform solid-liquid separation to obtain a leachate. The waste lithium iron phosphate positive electrode material is a positive electrode powder material with a particle size of 20 to 200 μm obtained by disassembling, crushing, cleaning, and drying waste lithium iron phosphate batteries. The solvent is water. The ratio of waste lithium iron phosphate positive electrode material to solvent is 20 to 200 g:1 L. The oxidant is one or more of sodium percarbonate, sodium perborate, sodium hypochlorite, calcium hypochlorite, sodium perchlorate, potassium perchlorate, sodium chlorate, sodium chlorite, ammonium peroxodisulfate, sodium peroxodisulfate, and potassium peroxodisulfate. The amount of oxidant added is 20 to 200% of the mass of the waste lithium iron phosphate positive electrode material. The activator is one or more of a divalent ferrous salt, a divalent cobalt salt, a divalent manganese salt, a divalent copper salt, and a monovalent silver salt, and the amount of the activator added is 1 to 50% of the mass of the waste lithium iron phosphate positive electrode material. In this step, the leaching reaction temperature is 1 to 40°C, the leaching reaction time is 60 to 180 minutes, and the leaching stirring speed is 300 to 800 rpm.

[0025] S2. Add an inorganic salt to the leachate obtained in step S1. The inorganic salt forms a precipitate with the activator in step S1, and a lithium-rich solution is obtained after solid-liquid separation. The inorganic salt is one or more of hydroxides, sulfides, carbonates, phosphates, halides, etc., and the molar amount of the inorganic salt added is 0.8 to 1.5 times the molar amount of the metal ion in the activator. The reaction temperature in this step is 30 to 90°C, the reaction time is 60 to 180 minutes, and the stirring speed is 300 to 800 rpm.

[0026] The following specific examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to specifically illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are only an example within a suitable range, that is, those skilled in the art can make a selection within a suitable range based on the description of this article, and are not limited to the specific values ​​​​exemplified below. In addition, the waste lithium iron phosphate positive electrode powder material used in the following examples and comparative examples contains Li 4.23%, Fe 19.27%, and P 33.6%, and the particle size of the powder material is less than 100 mesh.

[0027] Example 1

[0028] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression. The process of the method is basically as follows: Figure 1 As shown, the method specifically includes the following steps:

[0029] 1) Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetic stirring water bath and control the temperature at 40°C. Weigh 20g of waste lithium iron phosphate positive electrode powder material, 40g of ammonium peroxodisulfate and 1g of ferrous sulfate, and add them to the beaker respectively. Turn on the magnetic stirring, react at 500rpm for 120min, and then filter to obtain the leachate. The leachate was sent for ICP testing and analysis. After calculation, the lithium leaching rate was 99.98%, the iron content was 3.54g / L, and the phosphorus content was 1.19g / L.

[0030] 2) 1.92 g of sodium phosphate dodecahydrate was added to the leachate obtained in step 1), and air was introduced. The solution was heated to 90° C. and maintained at this temperature with stirring at 500 rpm. The reaction was continued for 60 minutes, followed by filtration to obtain a lithium-rich solution. The lithium-rich solution was subjected to ICP analysis, and the calculated iron content in the lithium-rich solution was 0.498 g / L and the phosphorus content was 0.11 g / L.

[0031] Example 2

[0032] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression. The process of the method is basically as follows: Figure 1 As shown, the method specifically includes the following steps:

[0033] 1) Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetic stirring water bath and control the temperature at 25°C. Weigh 20g of waste lithium iron phosphate positive electrode powder material, 20g of ammonium peroxodisulfate, and 4g of ferrous sulfate, and add them to the beaker respectively. Turn on the magnetic stirring, react at 500rpm for 120min, and then filter to obtain the leachate. The leachate was sent for ICP testing and analysis. After calculation, the lithium leaching rate was 95.73%, the iron content was 14.73g / L, and the phosphorus content was 1.02g / L.

[0034] 2) 12 g of sodium phosphate dodecahydrate was added to the leachate obtained in step 1), and air was introduced. The solution was heated to 50° C. and maintained at this temperature with stirring at 500 rpm. The reaction was continued for 60 minutes, followed by filtration to obtain a lithium-rich solution. The lithium-rich solution was subjected to ICP analysis, and the calculated iron content in the lithium-rich solution was 0.257 g / L and the phosphorus content was 2.79 g / L.

[0035] Example 3

[0036] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression. The process of the method is basically as follows: Figure 1 As shown, the method specifically includes the following steps:

[0037] 1) Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetic stirring water bath and use a low-temperature cooling circulation pump to control the temperature at 10°C. Weigh 5g of waste lithium iron phosphate positive electrode powder material, 1.25g of ammonium peroxydisulfate and 1g of ferrous sulfate, and add them to the beaker respectively. Turn on the magnetic stirring, react at 800rpm for 180min, and then filter to obtain the leachate. The leachate was sent for ICP testing and analysis. After calculation, the lithium leaching rate was 86.46%, the iron content was 4.81g / L, and the phosphorus content was 2.15g / L.

[0038] 2) Adding 2.94 g of sodium phosphate dodecahydrate to the leachate obtained in step 1), aerating the solution with air, heating the solution to 50° C. and maintaining the temperature therein with stirring at 500 rpm, reacting for 60 minutes, and then filtering the solution to obtain a lithium-rich solution. The lithium-rich solution was subjected to ICP analysis, and the calculated iron content and phosphorus content of the lithium-rich solution were 0.167 g / L and 0.105 g / L, respectively.

[0039] Example 4

[0040] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression. The process of the method is basically as follows: Figure 1 As shown, the method specifically includes the following steps:

[0041] 1) Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetic stirring water bath and control the temperature at 20°C. Weigh 10g of waste lithium iron phosphate positive electrode powder material, 5g of ammonium peroxodisulfate, and 5g of ferrous sulfate, and add them to the beaker respectively. Turn on the magnetic stirring, react at 800rpm for 90min, and then filter to obtain the leachate. The leachate was sent for ICP testing and analysis. After calculation, the lithium leaching rate was 94.45%, the iron content was 18.97g / L, and the phosphorus content was 0.92g / L.

[0042] 2) 14.16 g of sodium phosphate dodecahydrate was added to the leachate obtained in step 1), and air was introduced. The solution was heated to and maintained at 30° C. with stirring at 800 rpm. After reacting for 180 minutes, the solution was filtered to obtain a lithium-rich solution. The lithium-rich solution was subjected to ICP analysis, and the calculated iron content in the lithium-rich solution was 2.207 g / L and the phosphorus content was 3.192 g / L.

[0043] Example 5

[0044] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression. The process of the method is basically as follows: Figure 1 As shown, the method specifically includes the following steps:

[0045] 1) Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetic stirring water bath and use a low-temperature cooling circulation pump to control the temperature at 3°C. Weigh 10g of waste lithium iron phosphate positive electrode powder material, 10g of ammonium peroxydisulfate and 2g of ferrous sulfate, and add them to the beaker respectively. Turn on the magnetic stirring, react at 800rpm for 180min, and then filter to obtain the leachate. The leachate was sent for ICP testing and analysis. After calculation, the lithium leaching rate was 95.22%, the iron content was 7.68g / L, and the phosphorus content was 0.51g / L.

[0046] 2) Add 4.69 g of sodium phosphate dodecahydrate to the leachate obtained in step 1), purge with air, and heat the solution to 50° C., maintain the temperature, and stir at 500 rpm. After reacting for 60 minutes, filter the solution to obtain a lithium-rich solution. The lithium-rich solution was subjected to ICP analysis, and the calculated iron content and phosphorus content were 0.194 g / L and 0.316 g / L, respectively.

[0047] Example 6

[0048] Compared with Example 1, the only difference between this embodiment and Example 1 is that: the oxidant in this embodiment is sodium percarbonate (i.e., sodium percarbonate is used to replace the ammonium peroxydisulfate in Example 1), the activator is copper sulfate (i.e., copper sulfate is used to replace the ferrous sulfate in Example 1), and the inorganic salt is sodium sulfide (i.e., sodium sulfide is used to replace the sodium phosphate dodecahydrate in Example 1). After the leachate was sent for inspection, the lithium leaching rate was 96.18%, and the iron and phosphorus contents were 0.116 g / L and 0.41 g / L, respectively. After the inorganic salt was added, the iron and phosphorus contents in the lithium-rich solution were 0.09 g / L and 0.408 g / L, respectively.

[0049] Comparative Example 1

[0050] This comparative example provides a method for extracting lithium from waste lithium iron phosphate positive electrode material, the method comprising the following steps:

[0051] Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetically stirred water bath and control the temperature at 25°C. Weigh 20g of waste lithium iron phosphate cathode powder material and 20g of ammonium peroxodisulfate and add them to the beaker. Turn on the magnetic stirring, react at 500rpm for 120 minutes, and then filter to obtain the leachate. The leachate was sent for ICP testing and analysis. The calculated lithium leaching rate was 62.55%, the iron content was 0.178g / L, and the phosphorus content was 0.362g / L.

[0052] Comparative Example 2

[0053] This comparative example provides a method for extracting lithium from waste lithium iron phosphate positive electrode material, the method comprising the following steps:

[0054] Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetically stirred water bath at 40°C. Weigh 20g of waste lithium iron phosphate cathode powder and 40g of ammonium peroxodisulfate and add them to the beaker. Turn on the magnetic stirring, react at 500rpm for 120 minutes, and then filter to obtain the leachate. The leachate was sent for ICP analysis. The calculated lithium leaching rate was 82.75%, the iron content was 2.39g / L, and the phosphorus content was 1.34g / L.

[0055] Comparative Example 3

[0056] This comparative example provides a method for extracting lithium from waste lithium iron phosphate positive electrode material, the method comprising the following steps:

[0057] Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetically stirred water bath and control the temperature at 25°C. Weigh 20g of waste lithium iron phosphate cathode powder material and 4g of ferrous sulfate and add them to the beaker. Turn on the magnetic stirring, react at 500rpm for 120 minutes, and then filter to obtain the leachate. The leachate was sent for ICP testing and analysis. The calculated lithium leaching rate was 8.96%, the iron content was 14.76g / L, and the phosphorus content was 0.027g / L.

[0058] Comparative Example 4

[0059] Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetically stirred water bath at 50°C. Weigh 20g of waste lithium iron phosphate cathode powder and 4g of ferrous sulfate and add them to the beaker. Turn on the magnetic stirring, react at 500rpm for 120 minutes, and then filter to obtain the leachate. The leachate was sent for ICP analysis. The calculated lithium leaching rate was 16.32%, the iron content was 14.81g / L, and the phosphorus content was 0.098g / L.

[0060] Comparative Example 5

[0061] Measure 100mL of pure water and pour it into a beaker. Place the beaker in a magnetic stirring water bath and use a low-temperature cooling circulation pump to control the temperature at 3°C. Weigh 10g of waste lithium iron phosphate positive electrode powder material and 5g of ferrous sulfate, measure 1mL of hydrogen peroxide (30% mass fraction), and add them to the beaker respectively. Turn on the magnetic stirring, react at 800rpm for 180min, and then filter to obtain the leachate. The leachate was sent to ICP test analysis. After calculation, the lithium leaching rate was 16.64%, the iron content was 18.61g / L, and the phosphorus content was 0.28g / L.

[0062] Comparative Example 6

[0063] Measure 100mL of pure water and pour it into a beaker, place the beaker in a magnetic stirring water bath, and use a low-temperature cooling circulation pump to control the temperature at 3°C. Weigh 10g of waste lithium iron phosphate positive electrode powder material and 5g of ferrous sulfate, measure 30mL of hydrogen peroxide (30% mass fraction), and add them to the beaker respectively. Turn on the magnetic stirring, react at 800rpm for 180min, and then filter to obtain the leachate. The leachate was sent to ICP test analysis. After calculation, the lithium leaching rate was 24.8%, the iron content was 18.52g / L, and the phosphorus content was 0.33g / L.

[0064] In Examples 1 to 6, the lithium leaching rate reached a maximum of 99.98%, and the iron and phosphorus contents in the obtained lithium-rich solution were low. Furthermore, at a temperature of 3°C, the lithium leaching rate reached 95.22%. This demonstrates that the present invention can extract lithium at low temperatures and control the content of iron and phosphorus impurities in the lithium-rich solution.

[0065] Comparative Examples 1 and 2 demonstrate the importance of the activator in the present invention. Without it, the lithium leaching rate is significantly reduced. Comparative Examples 3 and 4 demonstrate the essential addition of an oxidant. Without it, the lithium leaching rate at 50°C is only 12.44%. This demonstrates that the oxidant and activator work synergistically to significantly improve the lithium leaching rate.

[0066] By comparing Example 5, Comparative Example 5 and Comparative Example 6, it can be seen that when the oxidant is hydrogen peroxide, the addition of the activator cannot achieve a high lithium leaching rate. This also shows that not all oxidants can be used in combination with the activator in the present invention to produce a synergistic effect, thereby significantly improving the lithium leaching rate.

[0067] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this implementation case. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field are aware of all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the inspiration given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the present invention. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression, characterized by: The following steps are involved: S1, adding waste lithium iron phosphate positive electrode material, oxidant and activator to the solvent, stirring and leaching, and separating the solid and liquid after the leaching is completed to obtain a leachate; S2. Adding an inorganic salt to the leachate obtained in step S1, the inorganic salt and the activator in step S1 form a precipitate, and obtaining a lithium-rich solution after solid-liquid separation.

2. The method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression according to claim 1, characterized in that: In step S1, the oxidant is one or more of sodium percarbonate, sodium perborate, sodium hypochlorite, calcium hypochlorite, sodium perchlorate, potassium perchlorate, sodium chlorate, sodium chlorite, ammonium peroxodisulphate, sodium peroxodisulphate and potassium peroxodisulphate.

3. The method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression according to claim 1, characterized in that: In step S1, the activator is one or more of a divalent ferrous salt, a divalent cobalt salt, a divalent manganese salt, a divalent copper salt and a monovalent silver salt.

4. The method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression according to claim 1, characterized in that: In step S2, the inorganic salt is one or more of hydroxide, sulfide, carbonate, phosphate, halide, etc.

5. The method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression according to claim 1, characterized in that: In step S1, the ratio of waste lithium iron phosphate positive electrode material to solvent is 20-200 g:1 L; and / or, the amount of the oxidant added is 20 to 200% of the mass of the waste lithium iron phosphate positive electrode material; And / or, the dosage of the activator is 1 to 50% of the mass of the waste lithium iron phosphate positive electrode material.

6. The method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression according to claim 1, characterized in that: In step S2, the molar amount of the inorganic salt added is 0.8 to 1.5 times the molar amount of the metal ions in the activator.

7. The method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression according to claim 1, characterized in that: In step S1, the leaching reaction temperature is 1-40° C., the leaching reaction time is 60-180 min, and the leaching stirring speed is 300-800 rpm.

8. The method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression according to claim 1, characterized in that: In step S2, the reaction temperature is 30-90°C, the reaction time is 60-180 min, and the stirring speed is 300-800 rpm.

9. The method for selectively extracting lithium from waste lithium iron phosphate cathode materials based on interfacial polarization activation-complexation suppression according to claim 1, characterized in that: In step S1 , the waste lithium iron phosphate positive electrode material is a positive electrode powder material with a particle size of 20 to 200 μm obtained by disassembling, crushing, cleaning and drying waste lithium iron phosphate batteries.

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