A method for recovering lithium from lithium iron phosphate battery positive electrode waste powder

Abstract

The application belongs to the field of lithium ion batteries, and relates to a method for recovering lithium from positive electrode waste powder of lithium iron phosphate batteries, comprising the following steps: selectively dissolving out lithium from the positive electrode waste powder of lithium iron phosphate batteries to obtain lithium dissolving-out solution and iron phosphate residue; removing copper and aluminum impurities from the lithium dissolving-out solution to obtain lithium purified solution and lithium copper aluminum-containing residue; precipitating and separating lithium from the lithium purified solution; dispersing the lithium copper aluminum-containing residue in water, and then sequentially performing aging, acid dissolution and filtration on the obtained slurry to obtain Al(OH)3 and lithium-rich copper-containing solution, and then performing electrolysis on the lithium-rich copper-containing solution to obtain lithium-poor copper-containing solution and metal copper, wherein the lithium-poor copper-containing solution is returned to the lithium dissolving-out solution for recycling treatment. The method provided by the application can further eliminate the lithium loss caused by the removal of copper and aluminum impurities during the chemical precipitation recovery of lithium, realize effective recovery of lithium, and has great application prospect.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, specifically relating to a method for recovering lithium from waste positive electrode powder of lithium iron phosphate batteries. Background Technology

[0002] Since its first report in 1997, lithium iron phosphate (LiFePO4, simplified LFP) material has become a promising cathode material for lithium-ion batteries due to its environmental friendliness, abundant raw material sources, low price, high specific capacity, excellent cycle performance, and thermal stability. It has enormous development potential in electric commercial vehicles, special-purpose vehicles, and energy storage. Driven by both policy and market forces, my country's new energy vehicle market has experienced explosive growth over the past decade. Starting with the first batch of the "Ten Cities, Thousand Vehicles" promotion plan for new energy vehicles, my country was among the first to deploy lithium iron phosphate batteries in the new energy vehicle sector. Generally, lithium iron phosphate batteries have a lifespan of 5-8 years, and the first batch of power batteries for new energy vehicles are already reaching their aging stage. A new wave of power battery "retirement" is imminent, and lithium-ion batteries will soon enter a large-scale scrapping and recycling phase. Waste lithium-ion batteries contain a large amount of valuable metal components, as well as electrolytes, separators, and casing materials. Improper disposal will pose a serious threat to the environment. Recycling used lithium iron phosphate batteries can not only reduce the environmental pollution caused by used lithium-ion batteries, but also bring considerable economic benefits.

[0003] Existing recycling technologies for retired lithium iron phosphate batteries are mainly divided into three categories based on the material's recycling cycle: cascade utilization, dismantling-sorting recycling, and metallurgical recycling. Cascade utilization involves disassembling, breaking down, and testing retired power batteries for secondary reuse in applications such as communication base stations, energy storage, and low-speed electric vehicles, maximizing the battery's value. Dismantling-sorting recycling involves discharging and breaking down the batteries, sorting them according to their constituent materials to separate plastics, metal casings, copper foil, aluminum foil, and electrode materials, obtaining high-value electrode materials. These are then recycled using pyrometallurgical or hydrometallurgical techniques. Metallurgical recycling involves calcining the spent batteries in a furnace to decompose the compounds, followed by reduction and hydrometallurgical steps to obtain metal alloys.

[0004] Lithium iron phosphate (LFP) cathode material is the most valuable core material in LFP power batteries, accounting for approximately 30-40% of the battery cost. Recycling technologies for spent LFP cathode materials mainly fall into two categories: solid-phase regeneration and hydrometallurgical techniques. Solid-phase regeneration involves adding lithium salts and carbon sources to spent LFP cathode powder to adjust its chemical composition, followed by processes such as ball milling and sintering to restore the composition and structure of the LFP material. Hydrometallurgical techniques recover valuable components such as lithium, iron, and phosphorus from spent LFP cathode materials using chemical methods. Lithium has the highest economic value among spent LFP materials, and much research focuses on lithium recovery.

[0005] For example, CN113666397A discloses an economical acid-based method for recovering lithium from waste lithium iron phosphate materials. This method involves mixing waste lithium iron phosphate powder, concentrated sulfuric acid, and water to form a slurry; introducing air into the slurry for aeration and stirring; adding hydrogen peroxide and continuing stirring after aeration stops; filtering to separate iron phosphate and PVDF; adding calcium carbonate to the filtrate to adjust the pH; adding lime to adjust the pH again; filtering; adding saturated lithium carbonate to the filtrate; filtering; introducing carbon dioxide to the filtrate for precipitation; filtering, washing, and drying to obtain lithium carbonate. However, this method typically only recovers about 90% of the lithium, leaving the remaining lithium in the waste, which not only wastes resources but also impacts the environment. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing methods in recovering lithium from waste lithium iron phosphate battery cathode powder, which have a low lithium yield, and to provide a method for recovering lithium from waste lithium iron phosphate battery cathode powder that can improve the lithium yield.

[0007] After in-depth and extensive research, the inventors of this invention discovered that existing technologies generally use chemical precipitation to remove copper and aluminum from waste lithium iron phosphate battery cathode powder to achieve lithium recovery. However, the lithium recovery rate is generally only around 90%, mainly because lithium is entrained in the copper-aluminum slag, resulting in lithium loss. By dispersing the lithium-containing copper-aluminum slag in water, and then sequentially aging, acid-dissolving, and filtering the resulting slurry, and then electrolyzing the resulting lithium-rich copper solution to obtain a lithium-poor copper solution, which is then recycled back to the lithium leaching solution, lithium can be effectively recovered from the lithium-containing copper slag. Based on this, this invention was completed.

[0008] Specifically, the method for recovering lithium from waste cathode powder of lithium iron phosphate batteries provided by the present invention includes:

[0009] S1. Selectively leaching lithium from the waste powder of lithium iron phosphate battery cathode to obtain lithium leaching solution and iron phosphate slag;

[0010] S2. Remove copper and aluminum impurities from the lithium leaching solution to obtain lithium purified solution and lithium-containing copper and aluminum slag;

[0011] S3. Separate lithium from the lithium purification solution by precipitation; disperse the lithium-containing copper-aluminum slag in water, and then age, acid dissolve and filter the resulting slurry in sequence to obtain Al(OH)3 and lithium-containing copper-rich solution. Then, electrolyze the lithium-containing copper-rich solution to obtain lithium-containing copper-poor solution and metallic copper. The lithium-containing copper-poor solution is returned to the lithium leaching solution for recycling.

[0012] In a preferred embodiment, step S1, the method for selectively leaching lithium from lithium iron phosphate battery cathode waste powder, includes solid-liquid separation after treating the lithium iron phosphate battery cathode waste powder with a combination of acid and oxidant.

[0013] In a preferred embodiment, in step S1, the acid solution is a sulfuric acid solution.

[0014] In a preferred embodiment, in step S1, the concentration of the sulfuric acid solution is 10–30 wt%.

[0015] In a preferred embodiment, in step S1, the amount of sulfuric acid solution used is such that the pH value of the system is 1.5 to 4.0.

[0016] In a preferred embodiment, in step S1, the oxidant is hydrogen peroxide.

[0017] In a preferred embodiment, in step S1, the hydrogen peroxide reacts with the Fe in the lithium iron phosphate battery cathode waste powder. 2+ The molar ratio is 0.6 to 1.0.

[0018] In a preferred embodiment, step S2, the method for removing copper and aluminum impurities from the lithium leaching solution includes adjusting the pH value of the lithium leaching solution to 4.0 to 10.0 and then performing solid-liquid separation.

[0019] In a preferred embodiment, step S3, the method for precipitating and separating lithium from the lithium purification solution, includes concentrating the lithium purification solution to a concentration of 10 g / L or higher, and then adding CO2 and / or Na2CO3 to the concentrate to precipitate lithium as Li2CO3 or adding Na3PO4 to the concentrate to precipitate lithium as Li3PO4.

[0020] In a preferred embodiment, in step S3, when dispersing the lithium-containing copper-aluminum slag in water, the amount of water used is such that the solid content of the resulting slurry is 15-50 wt%.

[0021] In a preferred embodiment, in step S3, the aging conditions include a temperature of 30–100°C and a time of 1–5 hours.

[0022] In a preferred embodiment, in step S3, the acid solution used for acid dissolution is a sulfuric acid solution and / or a nitric acid solution; the H+ in the acid solution... + With Cu in lithium-containing copper-aluminum slag 2+ The molar ratio is (2.4~4.0):1.

[0023] In a preferred embodiment, in step S3, the electrolysis conditions include using copper as the cathode, graphite or titanium as the anode, and a current density of 0.1–1.0 A / dm³. 2 The electrolysis time is 10 min to 2 h.

[0024] In a preferred embodiment, the method for recovering lithium from lithium iron phosphate battery cathode waste powder provided by the present invention further includes treating the tail liquid obtained after precipitating and separating lithium from the lithium purification solution to remove sodium salt, and then returning the lithium-rich solution to the lithium leaching solution for recycling.

[0025] In a preferred embodiment, the tail liquid treatment method is a thermal method or a membrane method.

[0026] The method provided by this invention can further eliminate lithium loss caused by the removal of copper and aluminum impurities during precipitation, based on the chemical precipitation method for lithium recovery, thus achieving effective lithium recovery and showing great application potential. Furthermore, the method for recovering lithium from lithium iron phosphate battery cathode waste powder provided by this invention can also produce additional byproducts of metallic copper and Al(OH)3, achieving efficient resource utilization. Attached Figure Description

[0027] Figure 1 The present invention provides a schematic diagram of the recovery of lithium from waste cathode powder of lithium iron phosphate batteries. Detailed Implementation

[0028] like Figure 1 As shown, the method for recovering lithium from waste cathode powder of lithium iron phosphate batteries provided by the present invention includes:

[0029] S1. Selectively leaching lithium from the waste powder of lithium iron phosphate battery cathode to obtain lithium leaching solution and iron phosphate slag;

[0030] S2. Remove copper and aluminum impurities from the lithium leaching solution to obtain lithium purified solution and lithium-containing copper and aluminum slag;

[0031] S3. Separate lithium from the lithium purification solution by precipitation; disperse the lithium-containing copper-aluminum slag in water, and then age, acid dissolve and filter the resulting slurry in sequence to obtain Al(OH)3 and lithium-containing copper-rich solution. Then, electrolyze the lithium-containing copper-rich solution to obtain lithium-containing copper-poor solution and metallic copper. The lithium-containing copper-poor solution is returned to the lithium leaching solution for recycling.

[0032] In a preferred embodiment, step S1, the method for selectively leaching lithium from lithium iron phosphate battery cathode waste powder, includes treating the lithium iron phosphate battery cathode waste powder with a co-impregnation of acid and an oxidant, followed by solid-liquid separation. The acid solution can be, for example, at least one of sulfuric acid solution, hydrochloric acid solution, phosphoric acid solution, and nitric acid solution, preferably a sulfuric acid solution. The concentration of the sulfuric acid solution is preferably 10–30 wt%, such as 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or any value between them. Furthermore, the amount of sulfuric acid solution used is preferably such that the pH value of the system is 1.5–4.0, specifically 1.5, 2.5, 3.5, 4.0, or any value between them. The oxidant is preferably hydrogen peroxide. The amount of hydrogen peroxide used is based on the H2O2 / Fe... 2+ The preferred molar ratio is 0.6–1.0, that is, the ratio of H2O2 in hydrogen peroxide to Fe in the waste powder of lithium iron phosphate battery cathode. 2+ The molar ratio is 0.6 to 1.0, such as 0.6, 0.7, 0.8, 0.9, 1.0 or any value between them.

[0033] In a preferred embodiment, step S2, the method for removing copper and aluminum impurities from the lithium leaching solution, includes adjusting the pH value of the lithium leaching solution to 4.0–10.0 followed by solid-liquid separation. Specifically, the pH value can be 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, or any value between them. Adjusting the pH value to 4.0–10.0 causes copper and aluminum in the lithium leaching solution to precipitate out as hydroxides. After solid-liquid separation, a purified lithium solution and lithium-containing copper-aluminum slag are obtained. Furthermore, adjusting the pH value to 4.0–10.0 can be achieved, for example, by adding an acid or alkali solution to the system. The acid solution can be, for example, at least one of sulfuric acid solution, hydrochloric acid solution, phosphoric acid solution, nitric acid solution, etc., and the alkali solution can be, for example, at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, ammonia water, etc.

[0034] In this invention, in step S3, the method for precipitating and separating lithium from the lithium purification solution can be, for example, by directly adding at least one of CO2, Na2CO3, and Na3PO4 to the lithium purification solution to precipitate lithium, but the lithium deposition efficiency is low in this case. In a preferred embodiment, the method for precipitating and separating lithium from the lithium purification solution includes concentrating the lithium purification solution to a concentration of 10 g / L or higher, and then adding CO2 and / or Na2CO3 to the concentrate to precipitate lithium as Li2CO3, or adding Na3PO4 to the concentrate to precipitate lithium as Li3PO4. The inventors of this invention have found that concentrating the lithium purification solution to a concentration of 10 g / L or higher before precipitation, specifically to 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L, 20 g / L, 22 g / L, 24 g / L, 26 g / L, 28 g / L, 30 g / L, or any value between them, can significantly improve the lithium deposition efficiency. Furthermore, the efficiency of lithium precipitation using Na3PO4 as a precipitant is significantly higher than that using CO2 and / or Na2CO3 as precipitants.

[0035] In this invention, the lithium content in the lithium-containing copper-aluminum slag is related to the copper and aluminum impurity content in the lithium iron phosphate battery cathode waste powder. The higher the impurity content, the higher the amount of lithium adsorbed by the slag when adjusting the pH value to precipitate copper and aluminum, resulting in high-lithium copper-aluminum slag. If the lithium in the copper-aluminum slag is not recovered, the lithium yield will be significantly reduced, resulting in the waste of high-value lithium metal. To recover lithium from the lithium-containing copper slag, the lithium-containing copper-aluminum slag needs to be dispersed in water, and the resulting slurry is then subjected to aging, acid dissolution, and filtration in sequence to obtain Al(OH)3 and lithium-rich copper solution. The lithium-rich copper solution is then electrolyzed to obtain lithium-poor copper solution and metallic copper. The lithium-poor copper solution is returned to the lithium leaching solution for recycling. When dispersing the lithium-containing copper-aluminum slag in water, the amount of water used is preferably such that the solid content of the resulting slurry is 15-50 wt%, such as 15 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, or any value between them. The preferred aging conditions include a temperature of 30–100°C, such as 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, or any value between them; and a time of 1–5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or any value between them. The acid solution used for acid dissolution can be a sulfuric acid solution and / or a nitric acid solution. The amount of acid solution used is calculated according to H… + / Cu 2+ The preferred molar ratio is 2.4 to 4.0, that is, the H+ in the acid solution... + Cu in lithium copper aluminum slag 2+The preferred molar ratio is 2.4 to 4.0, such as 2.4, 3.0, 3.5, 4.0, or any value between them. The electrolysis conditions preferably include using copper as the cathode; using graphite or titanium as the anode; and a current density of 0.1 to 1.0 A / dm³. 2 For example, 0.1A / dm 2 0.2A / dm 2 0.5A / dm 2 0.75A / dm 2 1.0A / dm 2 Or any value between them; the electrolysis time is 10 min to 2 h, such as 10 min, 30 min, 1 h, 1.5 h, 2 h or any value between them. Electrolysis can convert lithium-rich copper solution into lithium-poor copper solution, which can be recycled back to the lithium leaching solution. After electrolysis, 85-98% of Cu is deposited on the cathode in metallic form. The ratio of the amount of Cu deposited in metallic form to the total amount of Cu is the Cu deposition rate. The Cu deposition rate is related to the concentration of the lithium-rich copper solution. When the Cu concentration in the lithium-rich copper solution is as high as 2000 ug / mL, the Cu content can be reduced to 200 ug / mL after electrolysis, and 90% of Cu is deposited on the cathode in metallic form. When the lithium-rich copper solution is concentrated to a Cu content of more than 5000 ug / mL, about 96% of Cu is deposited on the cathode in metallic form.

[0036] In a preferred embodiment, the method for recovering lithium from lithium iron phosphate battery cathode waste powder provided by the present invention further includes treating the tail liquid obtained after precipitating and separating lithium from the lithium purification solution to obtain a lithium-rich solution, which is then returned to the lithium dissolution solution for recycling. The tail liquid treatment method mainly refers to desalination, that is, removing the salts (such as sodium salts like Na2SO4) generated during the recovery process. The removal method can specifically be a thermal method or a membrane method, which are well known to those skilled in the art and will not be elaborated here.

[0037] The present invention will be described in detail below through embodiments.

[0038] In the following examples and comparative examples, the lithium recovery rate was calculated according to the following formula:

[0039] Lithium recovery rate = (m1 + m2) / (m - m') × 100%

[0040] Wherein, m1 is the amount of lithium in the recovered lithium salt; m2 is the amount of lithium in the lithium-containing copper-poor solution; m is the amount of lithium in the added lithium iron phosphate battery cathode waste powder; and m' is the amount of lithium in the tailings. The Li content is determined according to the lithium content detection method specified in the national standard GB / T 30835-2014 Lithium-ion Battery Carbon Compliant Lithium Iron Phosphate Cathode Material.

[0041] Example 1 This example illustrates the method for recovering lithium from waste cathode powder of lithium iron phosphate batteries provided by the present invention.

[0042] S1. Add commercially available 27.5% hydrogen peroxide and 20wt% sulfuric acid solution to the waste positive electrode powder of lithium iron phosphate batteries. After stirring evenly, let it stand for 3 hours to obtain lithium leaching solution and iron phosphate residue. The amount of sulfuric acid solution used is adjusted to maintain the pH of the system at 3.0. The amount of hydrogen peroxide used is related to the Fe content in the waste positive electrode powder of lithium iron phosphate batteries. 2+ The molar ratio is 1.0.

[0043] S2. After adjusting the pH value of the lithium leaching solution to 8.0, solid-liquid separation is performed to obtain lithium purified solution and lithium-containing copper-aluminum slag.

[0044] S3. The lithium purification solution is concentrated to a concentration of 18 g / L. Na3PO4 is then added to the concentrate to precipitate lithium as Li3PO4, yielding lithium salt (Li salt). The resulting tailings are desalted using a membrane process to remove sodium salt, resulting in a lithium-rich solution. This lithium-rich solution is then recycled back to the lithium leaching solution. Lithium-containing copper-aluminum slag is dispersed in water to obtain a slurry with a solid content of 25 wt%. This slurry is then aged at 30°C for 5 hours. A 15 wt% sulfuric acid solution is then added to the system for acid dissolution for 30 minutes. The amount of sulfuric acid solution used is determined according to H... + Cu in lithium-containing copper-aluminum slag 2+ The molar ratio was 3.2. After acid dissolution was complete, the mixture was filtered to obtain Al(OH)3 and a lithium-rich copper solution. The lithium-rich copper solution was then electrolyzed, using copper as the cathode and graphite or titanium as the anode, with the current density controlled at 0.5 A / dm³. 2 After electrolysis for 1 hour, a lithium-containing copper-poor solution and metallic copper were obtained. The lithium-containing copper-poor solution was returned to the lithium leaching solution for recycling. The total lithium recovery rate was 95.8%.

[0045] Example 2 This example illustrates the method for recovering lithium from waste cathode powder of lithium iron phosphate batteries provided by the present invention.

[0046] S1. Add commercially available 27.5% hydrogen peroxide and 30wt% sulfuric acid solution to the waste positive electrode powder of lithium iron phosphate batteries. After stirring evenly, let it stand for 0.5 hours to obtain lithium leaching solution and iron phosphate residue. The amount of sulfuric acid solution used is adjusted to maintain the pH value of the system at 4. The amount of hydrogen peroxide used is related to the Fe content in the waste positive electrode powder of lithium iron phosphate batteries. 2+ The molar ratio is 0.6.

[0047] S2. After adjusting the pH value of the lithium leaching solution to 6.0, solid-liquid separation is performed to obtain lithium purified solution and lithium-containing copper-aluminum slag.

[0048] S3. The lithium purification solution is concentrated to a concentration of 12 g / L. CO2 is then added to the concentrate to precipitate lithium as Li2CO3, yielding lithium salt (Li salt). The resulting tailings are desalted using a membrane process to remove sodium salt, resulting in a lithium-rich solution. This lithium-rich solution is then recycled back to the lithium leaching solution. Lithium-containing copper-aluminum slag is dispersed in water to obtain a slurry with a solid content of 15 wt%. This slurry is then aged at 80°C for 3 hours. A 25 wt% sulfuric acid solution is then added to the system for acid dissolution for 45 minutes. The amount of sulfuric acid solution used is determined according to H... + Cu in lithium-containing copper-aluminum slag 2+ The molar ratio was 4.0. After acid dissolution was complete, the mixture was filtered to obtain Al(OH)3 and a lithium-rich copper solution. The lithium-rich copper solution was then electrolyzed, using copper as the cathode and graphite or titanium as the anode, with the current density controlled at 0.1 A / dm³. 2 After electrolysis for 2 hours, a lithium-containing copper-poor solution and metallic copper were obtained. The lithium-containing copper-poor solution was returned to the lithium leaching solution for recycling. The total lithium recovery rate was 94.8%.

[0049] Example 3 This example illustrates the method for recovering lithium from waste cathode powder of lithium iron phosphate batteries provided by the present invention.

[0050] S1. Add commercially available 27.5% hydrogen peroxide and 10wt% sulfuric acid solution to the waste positive electrode powder of lithium iron phosphate batteries. After stirring evenly, let it stand for 2 hours to obtain lithium leaching solution and iron phosphate residue. The amount of sulfuric acid solution used is adjusted to maintain the pH of the system at 2.0. The amount of hydrogen peroxide used is related to the Fe content in the waste positive electrode powder of lithium iron phosphate batteries. 2+ The molar ratio is 0.8.

[0051] S2. After adjusting the pH of the lithium leaching solution to 10, solid-liquid separation is performed to obtain lithium purified solution and lithium-containing copper-aluminum slag.

[0052] S3. The lithium purification solution is concentrated to a concentration of 22 g / L. Na2CO3 is then added to the concentrate to precipitate lithium as Li2CO3, yielding lithium salt (Li salt). The resulting tailings are desalted using a membrane process to remove sodium salt, resulting in a lithium-rich solution. This lithium-rich solution is then recycled back to the lithium leaching solution. Lithium-containing copper-aluminum slag is dispersed in water to obtain a slurry with a solid content of 20 wt%. This slurry is then aged at 50°C for 4 hours. A 10 wt% sulfuric acid solution is then added to the system for acid dissolution for 60 minutes. The amount of sulfuric acid solution used is determined according to H... + Cu in lithium-containing copper-aluminum slag 2+ The molar ratio was 2.4. After acid dissolution was complete, the mixture was filtered to obtain Al(OH)3 and a lithium-rich copper solution. The lithium-rich copper solution was then electrolyzed, using copper as the cathode and graphite or titanium as the anode, with the current density controlled at 1.0 A / dm³. 2After electrolysis for 30 minutes, a lithium-containing copper-poor solution and metallic copper were obtained. The lithium-containing copper-poor solution was returned to the lithium leaching solution for recycling. The total lithium recovery rate was 95.3%.

[0053] Example 4 illustrates the method for recovering lithium from waste cathode powder of lithium iron phosphate batteries provided by the present invention.

[0054] Lithium was recovered from spent cathode powder of lithium iron phosphate batteries according to the method of Example 1, except that in step S3, Na3PO4 was replaced with the same amount of Na2CO3 by weight, while the other conditions were the same as in Example 1. The results showed that the total lithium recovery rate was 94.5%.

[0055] Example 5 illustrates the method for recovering lithium from waste cathode powder of lithium iron phosphate batteries provided by the present invention.

[0056] Lithium was recovered from waste cathode powder of lithium iron phosphate batteries according to the method of Example 1. The difference was that in step S3, during the precipitation and separation of lithium from the lithium purification solution, the lithium purification solution was not concentrated first; instead, Na3PO4 was directly added to precipitate lithium as Li3PO4. The remaining conditions were the same as in Example 1. The results showed that the total lithium recovery rate was 95.0%.

[0057] Comparative Example 1: This example illustrates a comparative method for recovering lithium from waste cathode powder of lithium iron phosphate batteries.

[0058] Lithium was recovered from spent lithium iron phosphate battery cathode powder according to the method in Example 1, except that the step of recovering lithium from lithium-containing copper-aluminum slag was not included; all other conditions were the same as in Example 1. The results showed that the total lithium recovery rate was 91.0%.

[0059] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for recovering lithium from waste cathode powder of lithium iron phosphate batteries, characterized in that, The method includes: S1. Selectively leaching lithium from the waste powder of lithium iron phosphate battery cathode to obtain lithium leaching solution and iron phosphate slag; S2. Removing copper and aluminum impurities from lithium leaching solution. The method for removing copper and aluminum impurities from lithium leaching solution includes adjusting the pH value of lithium leaching solution to 4.0~8.0 so that copper and aluminum in lithium leaching solution precipitate out in the form of hydroxides, followed by solid-liquid separation to obtain lithium purified solution and lithium-containing copper and aluminum slag. S3. Separate lithium from the lithium purification solution by precipitation; disperse the lithium-containing copper-aluminum slag in water, and then age, acid dissolve and filter the resulting slurry in sequence to obtain Al(OH)3 and lithium-containing copper-rich solution. Then, electrolyze the lithium-containing copper-rich solution to obtain lithium-containing copper-poor solution and metallic copper. The lithium-containing copper-poor solution is returned to the lithium leaching solution for recycling.

2. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 1, characterized in that, In step S1, the method for selectively leaching lithium from lithium iron phosphate battery cathode waste powder includes treating the lithium iron phosphate battery cathode waste powder with a mixture of acid and oxidant, followed by solid-liquid separation.

3. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 2, characterized in that, In step S1, the acid solution is a sulfuric acid solution.

4. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 3, characterized in that, In step S1, the concentration of the sulfuric acid solution is 10~30wt%.

5. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 3, characterized in that, In step S1, the amount of sulfuric acid solution used is such that the pH value of the system is 1.5 to 4.

0.

6. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 2, characterized in that, In step S1, the oxidant is hydrogen peroxide.

7. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 6, characterized in that, In step S1, the hydrogen peroxide reacts with Fe in the waste lithium iron phosphate battery cathode powder. 2+ The molar ratio is 0.6~1.

0.

8. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 1, characterized in that, In step S3, the method for precipitating and separating lithium from the lithium purification solution includes concentrating the lithium purification solution to a concentration of 10 g / L or higher, and then adding CO2 and / or Na2CO3 to the concentrate to precipitate lithium as Li2CO3 or adding Na3PO4 to the concentrate to precipitate lithium as Li3PO4.

9. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 1, characterized in that, In step S3, when dispersing lithium-containing copper-aluminum slag in water, the amount of water used is such that the solid content of the resulting slurry is 15~50wt%.

10. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 1, characterized in that, In step S3, the aging conditions include a temperature of 30~100℃ and a time of 1~5h.

11. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 1, characterized in that, In step S3, the acid solution used for acid dissolution is a sulfuric acid solution and / or a nitric acid solution; the H+ in the acid solution... + With Cu in lithium-containing copper-aluminum slag 2+ The molar ratio is 2.4~4.

0.

12. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 1, characterized in that, In step S3, the electrolysis conditions include using copper as the cathode, graphite or titanium as the anode, and a current density of 0.1~1.0 A / dm³. 2 The electrolysis time is 10 min to 2 h.

13. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 1, characterized in that, The method also includes treating the tail liquid obtained after precipitating and separating lithium from the lithium purification solution to remove sodium salt, and then returning the lithium-rich solution to the lithium leaching solution for recycling.

14. The method for recovering lithium from waste cathode powder of lithium iron phosphate batteries according to claim 13, characterized in that, The method for treating the tail liquid is either thermal or membrane.

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