Method for recycling lithium manganese iron phosphate positive electrode material

Abstract

The application belongs to the field of new energy, and discloses a recycling method of a lithium manganese iron phosphate positive electrode material, which comprises the following steps: step 1: performing aerobic roasting on black powder containing the lithium manganese iron phosphate positive electrode material; step 2: dispersing the product of step 1 into an acidic water body to obtain a solution; and step 3: extracting corresponding elements from the solution in the order of first extracting iron elements and then extracting copper elements; wherein Cu 2+ is precipitated from the solution by a precipitant. The method adopts an oxygen-rich or aerobic calcination mode to make metal elements form oxides, so as to facilitate acidolysis; according to the pH law of extraction of each metal element, copper is extracted after iron, and the copper is obtained by using a precipitation method, so that the problem that copper and iron cannot be effectively distinguished during oxygen-rich or aerobic calcination can be effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of new energy, specifically to a method for recycling lithium manganese iron phosphate cathode material. Background Technology

[0002] In recent years, with the rapid development of the new energy industry, the requirements for power batteries have become increasingly stringent. Among these requirements, the cathode, as the most crucial component, directly determines the battery's quality. Lithium iron phosphate (LFP) cathode materials are widely used due to their abundant resources, affordable price, and stable and safe operation. However, they also suffer from drawbacks such as low conductivity and low capacity, hindering their further development. Research has found that doping LFP materials with a certain proportion of manganese creates a new cathode material that can effectively improve electrochemical performance, such as conductivity and operating voltage. Therefore, lithium manganese iron phosphate (MFP) is gradually replacing LFP and is gaining widespread application. Simultaneously, the recycling of materials from LFP batteries becomes particularly important after they reach the end of their service life.

[0003] Existing technologies typically employ oxygen-deficient sintering to convert iron into Fe as much as possible. 2+ The copper exists in the form of iron, and then copper is removed first, followed by iron. This is not feasible during oxygen-enriched or oxygen-containing calcination because during oxygen-enriched calcination, the copper on the electrode is almost completely oxidized, and a large amount of Cu is present in the solution. 2+ If copper is removed first, and the pH endpoint of the iron-copper displacement reaction is 2.4, under these pH conditions, the Fe in the solution... 3+ The formation of iron phosphate precipitate makes copper and iron difficult to separate. Oxygen-enriched or oxygen-containing calcination is an advantageous condition for achieving rapid and complete dissolution of the cathode material into the acid solution.

[0004] The technical problem addressed in this case is: how to achieve copper and iron separation in lithium manganese iron phosphate cathode materials under oxygen-rich or oxygen-enriched calcination conditions. Summary of the Invention

[0005] The main objective of this invention is to provide a method for recovering lithium manganese iron phosphate cathode material. This method uses oxygen-enriched or aerobic calcination to form oxides of metal elements, which facilitates acid hydrolysis. Based on the pH rules for the extraction of each metal element, copper is extracted after iron, and copper is obtained by precipitation. This method can effectively avoid the problem of ineffective separation of copper and iron during oxygen-enriched or aerobic calcination.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0008] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0009] Step 2: Disperse the product from Step 1 into acidic water to ionize the metal elements and obtain a solution; the pH of the acidic water is below 1.0;

[0010] In this step, the pH value of the acidic water can be selected as 0.95, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, 0.5, 0.4, 0.3, 0.2, 0, or -0.2;

[0011] Step 3: Extract the corresponding elements from the solution in the order of first extracting iron and then extracting copper;

[0012] Cu in the solution 2+ It is precipitated from the solution by a precipitating agent.

[0013] In the above-mentioned method for recovering lithium manganese iron phosphate cathode material, the acid in the acidic water is an inorganic acid; the amount of the inorganic acid used is equivalent to more than 1.1 times the amount used for ionizing manganese and iron elements.

[0014] Preferably, the amount of inorganic acid used is equivalent to 1.1 to 2.5 times the amount used for ionizing manganese and iron.

[0015] The reason why the lower limit of inorganic acid equivalent is set at 1.1 times is that it not only needs to dissolve manganese and iron, but also reacts with oxides of elements such as copper and aluminum, so the lower limit is set at at least 1.1 times.

[0016] Of course, the present invention does not exclude the use of organic acids, but the use of organic acids is uneconomical and inconvenient. Specifically, organic acids can lead to excessively high COD concentrations in wastewater, increasing the difficulty of wastewater treatment. At the same time, some organic acids have complexing properties or form precipitates with certain metal elements. Therefore, if organic acids are selected, sufficient small-scale experiments should be conducted to select the appropriate type of organic acid.

[0017] In the above-mentioned method for recovering lithium manganese iron phosphate cathode material, the inorganic acid is sulfuric acid, hydrochloric acid, or nitric acid.

[0018] In some embodiments of the present invention, hydrochloric acid is used instead of sulfuric acid, and under the same pH conditions, similar results as sulfuric acid can be achieved.

[0019] In the above-mentioned method for recycling lithium manganese iron phosphate cathode material, the calcination temperature in step 1 is 200℃~800℃, the calcination time is 1h~5h, and the calcination atmosphere is air or oxygen.

[0020] The purpose of aerobic roasting is to oxidize the electrode metal, which facilitates acid hydrolysis and increases the recovery rate of the cathode material.

[0021] The roasting temperature in step 1 is preferably 250℃~600℃, more preferably 300℃~450℃;

[0022] The roasting time is preferably 2h to 4h, more preferably 2h to 3.5h;

[0023] In some embodiments of the present invention, the calcination temperature may be selected as 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃.

[0024] In some embodiments of the present invention, the calcination time is 1h, 2h, 3h, 4h or 5h;

[0025] In the above-mentioned method for recovering lithium iron phosphate cathode material, the method for extracting iron in step 3 is specifically as follows:

[0026] Step 31: After filtering the solution from step 2, add Fe to the filtrate. 2+ and oxidizing agent until Fe 3+ Fe 2+ The total molar amount is equal to the molar amount of phosphate;

[0027] Step 32: Adjust the pH of the solution from step 31 to 1.6-2.0, and filter to obtain the first filter residue and the first filtrate.

[0028] In the above-mentioned method for recovering lithium iron phosphate cathode material, the method for extracting copper element in step 3 is specifically as follows:

[0029] Step 33: Add only precipitated Cu to the first filtrate 2+ The precipitant was used, and the pH at the reaction endpoint was controlled to be 3.0–4.0. The mixture was then filtered to obtain a second filter residue and a second filtrate.

[0030] As a further preferred embodiment of the present invention, step 33 is followed by:

[0031] Step 34: Adjust the pH of the second filtrate to 4.5-7, and filter to obtain the third filter residue and the third filtrate;

[0032] Step 35: Adjust the pH of the third filtrate to be no lower than 9, and filter to obtain the fourth filter residue and the fourth filtrate;

[0033] Step 36: Add the fourth filtrate to the carbonate solution to obtain lithium carbonate precipitate.

[0034] In the above-mentioned method for recycling lithium manganese iron phosphate cathode material, the oxidant in step 31 is hydrogen peroxide, oxygen, or sodium peroxide.

[0035] In the above-mentioned method for recovering lithium manganese iron phosphate cathode material, the precipitant in step 33 is a soluble sulfide.

[0036] In the above-mentioned method for recovering lithium manganese iron phosphate cathode material, the soluble sulfide is one or more combinations of sodium sulfide, potassium sulfide, and hydrogen sulfide.

[0037] Preferably, the precipitant and Cu 2+ The molar ratio is 1 to 1.2:1. Preferably, the precipitant is in slight excess. More preferably, the precipitant and Cu... 2+ The molar ratio is 1.05 to 1.12:1.

[0038] In the above-mentioned method for recovering lithium manganese iron phosphate cathode material, the reaction temperature of each of steps 31 to 36 is independently between room temperature and 70°C; the reaction time of each of steps 31 to 36 is independently between 1 and 5 hours.

[0039] In some embodiments of the present invention, the reaction temperatures of steps 31 to 36 are each independently 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 60°C, or 70°C or higher.

[0040] In some embodiments of the present invention, the reaction time of steps 31 to 36 is independently 1h, 2h, 3h, 4h or 5h or longer.

[0041] One of the above-described technical solutions of the present invention has at least one of the following advantages or beneficial effects:

[0042] In this invention, metal elements are formed into oxides by oxygen-enriched or aerobic calcination, which facilitates acid hydrolysis. Based on the pH rules for the extraction of each metal element, copper is extracted after iron, and copper is obtained by precipitation. This effectively avoids the problem of copper and iron not being able to be effectively distinguished during oxygen-enriched or aerobic calcination.

[0043] More specifically, the objective of this invention is achieved through a combination of the following elements:

[0044] 1. Utilizing the solubility of ferric phosphate at pH below 1.0, all metal elements are ionized prior to copper precipitation;

[0045] 2. Ferric phosphate precipitation is achieved by utilizing the fact that the pH endpoint of the ferric phosphate precipitation reaction is lower than the pH starting point of the precipitant for copper precipitation.

[0046] 3. The pH endpoint for copper precipitation using a precipitant is significantly lower than the pH endpoint for precipitation reactions of other metal elements in the form of hydroxides, thus achieving copper precipitation and effective separation of copper and iron.

[0047] In short, before extracting copper with a precipitant, it is only necessary to raise the pH of the solution to the precipitation pH of ferric phosphate, and then precipitate copper with a precipitant. The pH value of copper precipitation is greater than that of ferric phosphate precipitation. In this way, almost all metal elements can be dissolved using extremely low pH. Then, iron is precipitated first by ferric phosphate precipitation, and finally copper is precipitated with a precipitant, so that the purity of each precipitate is high.

[0048] In the traditional method, due to the oxygen-deficient calcination, the iron in the acid-dissolved solution exists in the form of ferrous ions. The pH is first adjusted to precipitate copper. Since ferrous phosphate is not a precipitable substance, iron does not precipitate during this process. However, combining the traditional method with aerobic calcination fails to achieve effective separation of iron and copper because the precipitation pH endpoint for copper (2.4), the formation of ferric phosphate precipitation, and the displacement reaction to obtain elemental copper occur simultaneously, making iron and copper inseparable. By combining the above techniques, instead of using the displacement method to extract copper, a precipitation method is adopted. Based on the 1.0 difference between the pH endpoint of ferric phosphate precipitation and the pH starting point for copper sulfide formation, effective separation of copper and iron in the aerobic calcination process is achieved.

[0049] In a preferred embodiment of the present invention, aluminum, manganese and lithium are separated by precipitation in sequence. Detailed Implementation

[0050] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1

[0052] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0053] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0054] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 450℃ in an oxygen atmosphere for 2 hours.

[0055] Step 2: Disperse the product of Step 1 into acidic water to ionize the metal elements and obtain a solution; the acid in the acidic water is sulfuric acid;

[0056] Specifically, after roasting, the powder and 200ml of deionized water were mixed to form a slurry; 76.03g of 60% concentrated sulfuric acid was added to the lithium manganese iron phosphate slurry, the pH was about 0.7, the temperature was raised to 50℃, the reaction was carried out for 3 hours, and the mixture was filtered. The filter cake contained impurities such as graphite that were insoluble in acid, totaling 26.75g (after drying).

[0057] Step 3: After filtering the solution from Step 2, determine the Fe content in the solution. 3+ Supplementing Fe with phosphate ion concentration 2+ and oxidizing agent until Fe 3+ Fe 2+ The total molar amount is equal to the molar amount of phosphate;

[0058] Specifically, after filtration, take 100g of the filtrate, add 15.57g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 1.85, the temperature was 50℃, the reaction time was 3 hours, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filter residue was ferric phosphate; the first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0059] Step 4: Add sodium sulfide solution and sodium hydroxide solution to the first filtrate. Sodium sulfide and Cu 2+ The molar ratio was 1.12:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 50℃, the reaction time was 3 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+ Mn 2+ The second filter residue is copper sulfide, with a content of 0.86g.

[0060] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 5.0–6.0, react for 0.5 h at 30°C, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0061] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 9.0–10.0, react for 1 hour at 50°C, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0062] Step 7: Based on the Li of the fourth filtrate +A saturated sodium carbonate solution with a concentration of 1.2 times the equivalent was prepared. The fourth filtrate was added to the saturated sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0063] Example 2

[0064] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0065] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0066] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 400℃ in an oxygen atmosphere for 3 hours.

[0067] Step 2: After roasting, mix the powder with 200ml of deionized water to form a slurry; add 82.3g of 60% concentrated sulfuric acid to the lithium manganese iron phosphate slurry, the pH is about 0.62, control the temperature to 30℃, react for 5h, filter, and the filter cake contains 26.83g of impurities that are insoluble in acid (after drying).

[0068] Step 3: After filtration, take 100g of the filtrate, add 15.32g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 2, the temperature was 40℃, the reaction time was 2 hours, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0069] Step 4: Add potassium sulfide solution and sodium hydroxide solution to the first filtrate. Potassium sulfide and Cu 2+ The molar ratio was 1.1:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 60℃, the reaction time was 2 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+ Mn 2+ The second filter residue is copper sulfide.

[0070] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 6, react for 1 hour at 40℃, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0071] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 9, react for 2 hours at 70℃, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0072] Step 7: Based on the Li of the fourth filtrate + An unsaturated sodium carbonate solution (concentration 16%) was prepared at a concentration of 1.2 times the equivalent. The fourth filtrate was added to the sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0073] Example 3

[0074] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0075] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0076] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 350℃ in an oxygen atmosphere for 4 hours.

[0077] Step 2: After roasting, mix the powder with 200ml of deionized water to form a slurry; add 88.7g of 60% concentrated sulfuric acid to the lithium manganese iron phosphate slurry, the pH of the system is about 0.55, control the temperature to 30℃, react for 5h, filter, the filter cake contains 27.14g of impurities that are insoluble in acid (after drying);

[0078] Step 3: After filtration, take 100g of the filtrate, add 15.05g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 1.8, the temperature was 50℃, the reaction time was 1 hour, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0079] Step 4: Add sodium sulfide solution and sodium hydroxide solution to the first filtrate. Sodium sulfide and Cu 2+ The molar ratio was 1.08:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 70℃, the reaction time was 3 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+ Mn 2+ The second filter residue is copper sulfide.

[0080] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 7, react for 2 hours at 50℃, and filter to obtain the third filter residue and the third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0081] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 10, react for 1 hour at 50℃, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0082] Step 7: Based on the Li of the fourth filtrate + An unsaturated sodium carbonate solution (concentration 15%) was prepared at a concentration of 1.2 times the equivalent. The fourth filtrate was added to the sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0083] Example 4

[0084] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0085] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0086] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 300℃ in an oxygen atmosphere for 3 hours.

[0087] Step 2: After roasting, mix the powder with 200ml of deionized water to form a slurry; add 76.03g of 60% concentrated sulfuric acid to the lithium manganese iron phosphate slurry, the pH is about 0.7, control the temperature to 70℃, react for 2 hours, filter, and the filter cake contains 28.36g of impurities that are insoluble in acid (after drying).

[0088] Step 3: After filtration, take 100g of the filtrate, add 16.13g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, potassium hydroxide was added to control the pH of the reaction system to 1.9, the temperature was 70℃, the reaction time was 2 hours, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0089] Step 4: Add sodium sulfide solution and potassium hydroxide solution to the first filtrate. Sodium sulfide and Cu 2+The molar ratio was 1.06:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 30℃, the reaction time was 2 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+ Mn 2+ The second filter residue is copper sulfide.

[0090] Step 5: Add potassium hydroxide to adjust the pH of the second filtrate to 4.5, react for 1 hour at 30℃, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0091] Step 6: Add potassium hydroxide to adjust the pH of the third filtrate to 9, react for 5 hours at 30℃, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0092] Step 7: Based on the Li of the fourth filtrate + Prepare a saturated potassium carbonate solution with a concentration of 1.2 times the equivalent. Add the fourth filtrate to the potassium carbonate solution and react for 1 hour at a temperature of 80°C. Filter to obtain a soluble sulfate solution. The filter cake is solid lithium carbonate.

[0093] Example 5

[0094] The process is largely the same as in Example 1, except that in step 3, alkali is added to control the pH of the system to 1.6.

[0095] Specifically as follows:

[0096] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0097] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0098] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 450℃ in an oxygen atmosphere for 2 hours.

[0099] Step 2: Disperse the product of Step 1 into acidic water to ionize the metal elements and obtain a solution; the acid in the acidic water is sulfuric acid;

[0100] Specifically, after roasting, the powder and 200ml of deionized water were mixed to form a slurry; 76.03g of 60% concentrated sulfuric acid was added to the lithium manganese iron phosphate slurry, the pH was about 0.7, the temperature was raised to 50℃, the reaction was carried out for 3 hours, and the mixture was filtered. The filter cake contained impurities such as graphite that were insoluble in acid, totaling 26.69g (after drying).

[0101] Step 3: After filtering the solution from Step 2, determine the Fe content in the solution. 3+ Supplementing Fe with phosphate ion concentration 2+ and oxidizing agent until Fe 3+ Fe 2+ The total molar amount is equal to the molar amount of phosphate;

[0102] Specifically, after filtration, take 100g of the filtrate, add 15.43g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 1.6, the temperature was 50℃, the reaction time was 3 hours, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filter residue was ferric phosphate; the first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0103] Step 4: Add sodium sulfide solution and sodium hydroxide solution to the first filtrate. Sodium sulfide and Cu 2+ The molar ratio was 1.12:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 50℃, the reaction time was 3 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+ Mn 2+ The second filter residue is copper sulfide.

[0104] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 5.0–6.0, react for 0.5 h at 30°C, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0105] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 9.0–10.0, react for 1 hour at 50°C, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0106] Step 7: Based on the Li of the fourth filtrate + A saturated sodium carbonate solution with a concentration of 1.2 times the equivalent was prepared. The fourth filtrate was added to the saturated sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0107] Example 6

[0108] The process is largely the same as in Example 1, except that in step 3, alkali is added to control the pH of the system to 2.0.

[0109] Specifically as follows:

[0110] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0111] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0112] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 450℃ in an oxygen atmosphere for 2 hours.

[0113] Step 2: Disperse the product of Step 1 into acidic water to ionize the metal elements and obtain a solution; the acid in the acidic water is sulfuric acid;

[0114] Specifically, after roasting, the powder and 200ml of deionized water were mixed to form a slurry; 76.03g of 60% concentrated sulfuric acid was added to the lithium manganese iron phosphate slurry, the pH was about 0.7, the temperature was raised to 50℃, the reaction was carried out for 3 hours, and the mixture was filtered. The filter cake contained impurities such as graphite that were insoluble in acid, totaling 26.72g (after drying).

[0115] Step 3: After filtering the solution from Step 2, determine the Fe content in the solution. 3+ Supplementing Fe with phosphate ion concentration 2+ and oxidizing agent until Fe 3+ Fe 2+ The total molar amount is equal to the molar amount of phosphate;

[0116] Specifically, after filtration, take 100g of the filtrate, add 15.51g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 2.0, the temperature was 50℃, the reaction time was 3 hours, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filter residue was ferric phosphate; the first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0117] Step 4: Add sodium sulfide solution and sodium hydroxide solution to the first filtrate. Sodium sulfide and Cu 2+ The molar ratio was 1.12:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 50℃, the reaction time was 3 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+Mn 2+ The second filter residue is copper sulfide.

[0118] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 5.0–6.0, react for 0.5 h at 30°C, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0119] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 9.0–10.0, react for 1 hour at 50°C, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0120] Step 7: Based on the Li of the fourth filtrate + A saturated sodium carbonate solution with a concentration of 1.2 times the equivalent was prepared. The fourth filtrate was added to the saturated sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0121] Example 7

[0122] Generally the same as Example 1, except that in step 4, sodium sulfide and Cu 2+ The molar ratio is 1:1.

[0123] Specifically as follows:

[0124] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0125] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0126] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 450℃ in an oxygen atmosphere for 2 hours.

[0127] Step 2: Disperse the product of Step 1 into acidic water to ionize the metal elements and obtain a solution; the acid in the acidic water is sulfuric acid;

[0128] Specifically, after roasting, the powder and 200ml of deionized water were mixed to form a slurry; 76.03g of 60% concentrated sulfuric acid was added to the lithium manganese iron phosphate slurry, the pH was about 0.7, the temperature was raised to 50℃, the reaction was carried out for 3 hours, and the mixture was filtered. The filter cake contained impurities such as graphite that were insoluble in acid, totaling 26.75g (after drying).

[0129] Step 3: After filtering the solution from Step 2, determine the Fe content in the solution. 3+Supplementing Fe with phosphate ion concentration 2+ and oxidizing agent until Fe 3+ Fe 2+ The total molar amount is equal to the molar amount of phosphate;

[0130] Specifically, after filtration, take 100g of the filtrate, add 15.57g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 1.85, the temperature was 50℃, the reaction time was 3 hours, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filter residue was ferric phosphate; the first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0131] Step 4: Add sodium sulfide solution and sodium hydroxide solution to the first filtrate. Sodium sulfide and Cu 2+ The molar ratio was 1:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 50℃, the reaction time was 3 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+ Mn 2+ The second filter residue is copper sulfide.

[0132] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 5.0–6.0, react for 0.5 h at 30°C, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0133] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 9.0–10.0, react for 1 hour at 50°C, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0134] Step 7: Based on the Li of the fourth filtrate + A saturated sodium carbonate solution with a concentration of 1.2 times the equivalent was prepared. The fourth filtrate was added to the saturated sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0135] Example 8

[0136] Generally the same as Example 1, except that in step 4, sodium sulfide and Cu 2+ The molar ratio is 1:1.

[0137] Specifically as follows:

[0138] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0139] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0140] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 450℃ in an oxygen atmosphere for 2 hours.

[0141] Step 2: Disperse the product of Step 1 into acidic water to ionize the metal elements and obtain a solution; the acid in the acidic water is sulfuric acid;

[0142] Specifically, after roasting, the powder and 200ml of deionized water were mixed to form a slurry; 76.03g of 60% concentrated sulfuric acid was added to the lithium manganese iron phosphate slurry, the pH was about 0.7, the temperature was raised to 50℃, the reaction was carried out for 3 hours, and the mixture was filtered. The filter cake contained impurities such as graphite that were insoluble in acid, totaling 26.75g (after drying).

[0143] Step 3: After filtering the solution from Step 2, add Fe according to the concentration of Fe3+ and phosphate ions in the solution. 2+ and oxidizing agent until Fe 3+ Fe 2+ The total molar amount is equal to the molar amount of phosphate;

[0144] Specifically, after filtration, take 100g of the filtrate, add 15.57g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 1.85, the temperature was 50℃, the reaction time was 3 hours, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filter residue was ferric phosphate; the first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0145] Step 4: Add potassium sulfide solution and sodium hydroxide solution to the first filtrate. Potassium sulfide and Cu 2+ The molar ratio was 1:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 50℃, the reaction time was 3 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+ Mn 2+ The second filter residue is copper sulfide.

[0146] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 5.0–6.0, react for 0.5 h at 30°C, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0147] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 9.0–10.0, react for 1 hour at 50°C, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0148] Step 7: Based on the Li of the fourth filtrate + A saturated sodium carbonate solution with a concentration of 1.2 times the equivalent was prepared. The fourth filtrate was added to the saturated sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0149] Example 9

[0150] The method is largely the same as in Example 1, except that in step 4, sodium sulfide is replaced with hydrogen sulfide.

[0151] Specifically as follows:

[0152] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0153] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0154] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 450℃ in an oxygen atmosphere for 2 hours.

[0155] Step 2: Disperse the product of Step 1 into acidic water to ionize the metal elements and obtain a solution; the acid in the acidic water is sulfuric acid;

[0156] Specifically, after roasting, the powder and 200ml of deionized water were mixed to form a slurry; 76.03g of 60% concentrated sulfuric acid was added to the lithium manganese iron phosphate slurry, the pH was about 0.7, the temperature was raised to 50℃, the reaction was carried out for 3 hours, and the mixture was filtered. The filter cake contained impurities such as graphite that were insoluble in acid, totaling 26.75g (after drying).

[0157] Step 3: After filtering the solution from Step 2, determine the Fe content in the solution. 3+ Supplementing Fe with phosphate ion concentration 2+ and oxidizing agent until Fe 3+ Fe 2+ The total molar amount is equal to the molar amount of phosphate;

[0158] Specifically, after filtration, take 100g of the filtrate, add 15.57g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 1.85, the temperature was 50℃, the reaction time was 3 hours, and the mixture was filtered to obtain the first filtrate and the first filter residue. The first filter residue was ferric phosphate; the first filtrate contained Li. + Mn 2+ Al 3+ Cu 2+ A sulfate solution.

[0159] Step 4: Add hydrogen sulfide aqueous solution and sodium hydroxide solution to the first filtrate. Hydrogen sulfide and Cu 2+ The molar ratio was 1.12:1, the pH at the reaction endpoint was controlled at 3.0–4.0, the temperature was 50℃, the reaction time was 3 h, and the mixture was filtered to obtain a second residue and a second filtrate; the second filtrate contained Li. + Al 3+ Mn 2+ The second filter residue is copper sulfide.

[0160] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 5.0–6.0, react for 0.5 h at 30°C, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue is aluminum hydroxide;

[0161] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 9.0–10.0, react for 1 hour at 50°C, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0162] Step 7: Based on the Li of the fourth filtrate + A saturated sodium carbonate solution with a concentration of 1.2 times the equivalent was prepared. The fourth filtrate was added to the saturated sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0163] Comparative Example 1

[0164] A method for recycling lithium manganese iron phosphate cathode material includes the following steps:

[0165] Step 1: Aerobic roasting of the black powder containing lithium iron phosphate cathode material;

[0166] 75g of waste manganese iron lithium battery black powder (lithium content 2.7%, copper content 2.37%, aluminum content 0.83%) was roasted at 500℃ in an oxygen atmosphere for 2 hours.

[0167] Step 2: Disperse the product of Step 1 into acidic water to ionize the metal elements and obtain a solution; the acid in the acidic water is sulfuric acid;

[0168] Specifically, after roasting, the powder and 200ml of deionized water were mixed to form a slurry; 76.03g of 60% concentrated sulfuric acid was added to the lithium manganese iron phosphate slurry, the temperature was raised to 50℃, the reaction was carried out for 3 hours, and the mixture was filtered. The filter cake contained 26.81g of impurities that were insoluble in acid (after drying).

[0169] Step 3: Add 1.71g of iron powder to the solution in Step 2, stir to react, and a precipitate will form. After filtration, the first filtrate and the first filter residue (mostly iron phosphate) are obtained. Add acid to adjust the pH of the first filtrate to 0.7.

[0170] Step 4: Take 100g of the filtrate from Step 3, add 10.87g of ferrous sulfate heptahydrate, and add hydrogen peroxide to remove the Fe from the solution. 2+ Completely oxidized to Fe 3+ Then, liquid alkali was added to control the pH of the reaction system to 1.85, the temperature to 50℃, the reaction time to 2 hours, and the mixture was filtered to obtain the second filtrate and the second filter residue (mostly iron phosphate).

[0171] Step 5: Add sodium hydroxide to adjust the pH of the second filtrate to 5, react for 0.5 h at 30°C, and filter to obtain the third residue and third filtrate; the third filtrate contains Li. + and Mn 2+ The filtrate; the third filter residue was tested and found to contain aluminum hydroxide and copper hydroxide;

[0172] Step 6: Add sodium hydroxide to adjust the pH of the third filtrate to 9, react for 1 hour at 50℃, filter, and obtain Li-containing solution. + The fourth filtrate and the fourth filter residue, wherein the fourth filter residue is manganese hydroxide;

[0173] Step 7: Based on the Li of the fourth filtrate + A saturated sodium carbonate solution with a concentration of 1.2 times the equivalent was prepared. The fourth filtrate was added to the saturated sodium carbonate solution, and the reaction was carried out for 1 hour at a temperature of 90°C. After filtration, a sodium sulfate solution was obtained, and the filter cake was solid lithium carbonate.

[0174] The filter residues from each step of the examples and comparative examples were dried and weighed, and the results are shown in Table 1 below:

[0175] Table 1 Filter Cake Weight Table

[0176]

[0177]

[0178] Results analysis:

[0179] 1. As can be seen from Examples 1 to 9, good recovery efficiency can be obtained under conventional reaction temperatures and reaction times;

[0180] Meanwhile, the lower pH allows ferric phosphate to exist stably in an ionized form, providing suitable conditions for subsequent separation.

[0181] 2. As can be seen from Examples 1 to 9, compared with the reduction and replacement method, the preferred precipitant does not introduce other metal elements and does not require attention to the pH value of the system, making the separation of copper and iron a reality.

[0182] 3. The first filter residue in Comparative Example 1 was found to contain ferric phosphate precipitate after testing;

[0183] The following is a detailed analysis of several phenomena observed in Comparative Example 1:

[0184] 3.1. After adding 1.71g of iron powder, the pH of the solution is about 1.5. At this point, it has entered the precipitation pH range of ferric phosphate. However, it is still some distance away from the pH required for complete precipitation of ferric phosphate. Therefore, at this stage, some ferric phosphate will precipitate out.

[0185] 3.2 The first filter residue of Comparative Example 1 did not contain copper, indicating that in this comparative example, iron did not displace copper before reacting with acid according to the metal activity series.

[0186] As can be seen from Example 1 and Comparative Example 1, the existing method cannot effectively separate iron and copper. The reason is that, under extremely acidic conditions, when iron powder is added to the system, it does not first displace copper according to the metal activity series, but reacts with the acid first to become Fe. 2+ (This phenomenon was still reproduced during industrial scale-up); therefore, if the copper is to be replaced using the existing technology, iron powder must be added first to raise the pH of the solution and remove it from the extremely acidic environment in order to carry out the replacement reaction smoothly. However, the increase in pH leads to the precipitation of iron phosphate, which makes it impossible to separate copper and iron.

[0187] 3.3. In further experiments, this invention found that if the amount of iron powder used in step 3 of Comparative Example 1 was increased to 3.58 g (approximately 2.3 times the copper equivalent), copper still could not be displaced because it preferentially displaced Fe in the solution. 3+ Reduced to Fe 2+ The reaction equation is shown in Equation 1 below.

[0188] It should be noted that if iron powder is added further to reduce all the ferric iron and then further displace copper (the reaction equation is shown in Equation 2 below), the consumption of iron powder in the entire reaction will increase. Furthermore, to ensure the smooth progress of subsequent steps, the pH value needs to be lowered, which increases acid consumption, making it impractical for industrial applications. This invention, by utilizing the ionic stability of ferric phosphate under low pH conditions, can preferentially precipitate and separate ferric phosphate, and then separate copper as copper sulfide. This allows for effective separation of metal ions during the reaction process as the pH gradually increases.

[0189] 2Fe 3+ +Fe→3Fe 2+ Formula 1;

[0190] Fe+Cu 2+ →Fe 2+ +Cu Formula 2;

[0191] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A recovery method of a lithium iron manganese phosphate positive electrode material, characterized by, The method comprises the following steps: Step 1: performing aerobic roasting on black powder containing a lithium iron manganese phosphate positive electrode material; Step 2: dispersing the product of step 1 into an acidic aqueous body to ionize metal elements, to obtain a solution; the pH value of the acidic aqueous body is less than 1.0; Step 3: extracting corresponding elements from the solution in the order of extracting iron elements first and then extracting copper elements; The method for extracting iron elements in step 3 is specifically as follows: Step 31 : After filtration of the solution of step 2, to the filtrate is added Fe 2+ and oxidizing agent until the total moles of Fe 3+ , Fe 2+ and moles of phosphate are equal. Step 32: The solution is filtered and the filtrate is used in step 33. Step 32: adjusting the pH value of the solution of step 31 to 1.6-2.0, and filtering to obtain first filter residue and first filtrate; the first filter residue is iron phosphate; Step 33: Add only precipitated Cu to the first filtrate 2+ The precipitant was used to control the pH at the reaction endpoint to be 3.0~4.0, and the mixture was filtered to obtain a second filter residue and a second filtrate; the second filter residue was copper sulfide. Step 34: adjusting the pH value of the second filtrate to 4.5-7, and filtering to obtain third filter residue and third filtrate; the third filter residue is aluminum hydroxide; Step 35: adjusting the pH value of the third filtrate to not less than 9, and filtering to obtain fourth filter residue and fourth filtrate; the fourth filter residue is manganese hydroxide; Step 36: adding the fourth filtrate into a carbonate solution to obtain lithium carbonate precipitate.

2. The recovery method of the lithium iron manganese phosphate cathode material according to claim 1, characterized in that, The acid in the acidic aqueous body is an inorganic acid; the amount of the inorganic acid is equivalent to 1.1 times or more of the equivalent amount of manganese elements and iron elements used for ionization.

3. The recovery method of the lithium iron manganese phosphate cathode material according to claim 2, characterized in that, The amount of the inorganic acid is equivalent to 1.1-2.5 times of the equivalent amount of manganese elements and iron elements used for ionization.

4. The recovery method of the lithium iron manganese phosphate cathode material according to claim 2, characterized in that, The inorganic acid is sulfuric acid, hydrochloric acid or nitric acid.

5. The recovery method of the lithium iron manganese phosphate cathode material according to claim 1, characterized in that, The roasting temperature of step 1 is 200-800 DEG C, the roasting time is 1-5 h, and the roasting atmosphere is air or oxygen.

6. The recovery method of the lithium iron manganese phosphate cathode material according to claim 1, characterized in that, The oxidizing agent in step 31 is hydrogen peroxide, oxygen or sodium peroxide.

7. The recovery method of the lithium iron manganese phosphate cathode material according to claim 1, characterized in that, The precipitant is a soluble sulfide.

8. The recovery method of the lithium iron manganese phosphate cathode material according to claim 7, characterized in that, The soluble sulfide is one or a combination of multiple of sodium sulfide, potassium sulfide and hydrogen sulfide.

9. The recovery method of the lithium iron manganese phosphate cathode material according to claim 7, characterized in that, The molar ratio of the precipitant and Cu 2+ is 1-1.2:

1.

10. The recovery method of the lithium iron manganese phosphate cathode material according to claim 1, characterized in that, The reaction temperature of steps 31-33 is independently normal temperature-70 DEG C; the reaction time of steps 31-33 is independently 1-5 h.

11. The recovery method of the lithium iron manganese phosphate cathode material according to claim 1, characterized in that, The reaction temperature of steps 34-36 is independently normal temperature-70 DEG C; the reaction time of steps 34-36 is independently 1-5 h.

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