Method for preparing battery-grade iron phosphate by using lithium extraction residue and battery-grade iron phosphate

Abstract

The application discloses a method for preparing battery-grade iron phosphate by using lithium extraction residue and battery-grade iron phosphate, and relates to the technical field of lithium battery recycling. The method comprises the following steps: mixing and leaching lithium extraction residue and acid liquor, and obtaining iron-containing filtrate and first filtration residue after solid-liquid separation; adding phosphorus-iron residue into the iron-containing filtrate, and making the phosphorus-iron residue react with the iron-containing filtrate, so as to obtain a first mixed solution after solid-liquid separation, wherein the phosphorus-iron residue is one or more of FeP, Fe2P and Fe3P; adjusting the pH of the first mixed solution, and obtaining a second mixed solution and second filtration residue after solid-liquid separation; adding an oxidizing agent into the second mixed solution, oxidizing the divalent iron in the second mixed solution to obtain a first reaction liquid containing iron phosphate precipitate, filtering the first reaction liquid, and obtaining iron phosphate dihydrate product after washing and drying of the obtained precipitate. The method can treat two kinds of waste residues, i.e., lithium extraction residue and phosphorus-iron residue, simultaneously, does not need to add a reducing agent such as iron powder, and can improve the economic benefit of lithium extraction residue treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery recycling, and in particular to a method for preparing battery-grade iron phosphate from lithium extraction residue and battery-grade iron phosphate. BACKGROUND

[0002] Lithium iron phosphate batteries have excellent electrical cycling performance, high safety performance, and low cost, and their application in new energy vehicles and other fields is growing rapidly. Iron phosphate, as the main raw material for preparing lithium iron phosphate, has an important influence on the physical and chemical properties of lithium iron phosphate. Battery-grade iron phosphate used to prepare positive electrode materials has very high requirements for impurity content and requires harsh basic raw materials. High-purity phosphoric acid or phosphate and iron salt are usually used for reaction, but the cost of high-purity raw materials is very high. Therefore, it is urgent to consider using some low-cost iron and phosphorus sources to synthesize battery-grade iron phosphate.

[0003] With the rapid development of the new energy industry, the number of new energy vehicles in use is increasing year by year, which also means that a large number of lithium iron phosphate batteries will be discarded every year. Waste lithium iron phosphate batteries contain a wealth of lithium, iron, and phosphorus elements, which are important secondary energy sources. The lithium content in waste lithium iron phosphate batteries is low, but the iron and phosphorus content is high. However, the recovery value of lithium is high. In traditional recovery processes, lithium is usually recovered as high-value lithium carbonate or lithium hydroxide, and the remaining materials are treated as waste residue, collectively known as lithium extraction residue. Lithium extraction residue is basically discarded as waste, which not only fails to maximize the utilization of iron and phosphorus resources, but also causes significant environmental pollution.

[0004] In order to improve resource utilization and reduce environmental pollution, lithium extraction residue has been subjected to secondary recovery and utilization in recent years. The traditional method is to dissolve lithium extraction residue with high-concentration inorganic acid, and the leaching filtrate is subjected to reduction, impurity removal, and oxidation to obtain iron phosphate. This traditional method has high acid and alkali consumption and low economic benefits. SUMMARY

[0005] The present application discloses a method for preparing battery-grade iron phosphate from lithium extraction residue and battery-grade iron phosphate, to solve the technical problem of low economic benefits in the related art method for preparing battery-grade iron phosphate from lithium extraction residue.

[0006] To solve the above problems, the present application adopts the following technical solutions:

[0007] The method for preparing battery-grade iron phosphate from lithium extraction residue comprises the following steps:

[0008] The lithium extraction residue is mixed with an acid solution for leaching, and after solid-liquid separation, an iron-containing filtrate and a first filtration residue are obtained;

[0009] The phosphorus iron slag is added into the filtrate containing iron, and the phosphorus iron slag is allowed to react with the filtrate containing iron, so as to obtain a first mixed solution after solid-liquid separation, wherein the phosphorus iron slag is one or more of FeP, Fe2P and Fe3P;

[0010] The pH of the first mixed solution is adjusted, and a second mixed solution and a second filter residue are obtained after solid-liquid separation;

[0011] An oxidizing agent is added into the second mixed solution, so as to obtain a first reaction liquid containing iron phosphate precipitate after oxidation of the divalent iron in the second mixed solution, and the first reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain a dihydrate iron phosphate product.

[0012] According to an optional embodiment, the method for preparing the battery-grade iron phosphate by using the lithium extraction slag further comprises the following steps:

[0013] After the reaction liquid containing the iron phosphate precipitate is filtered, sodium carbonate is added into the obtained filtrate, and a second reaction liquid containing lithium carbonate precipitate is obtained after reaction, and the second reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain a lithium carbonate product;

[0014] Or, after the reaction liquid containing the iron phosphate precipitate is filtered, phosphoric acid is added into the obtained filtrate, and a lithium dihydrogen phosphate solution is obtained after reaction, and a lithium dihydrogen phosphate product is obtained after concentration, crystallization and drying.

[0015] According to an optional embodiment, an alkali solution is added into the first mixed solution, and the pH of the first mixed solution is increased to 2-3.

[0016] According to an optional embodiment, after the first mixed solution is obtained, the following steps are further included:

[0017] Battery black powder is added into the first mixed solution, and the battery black powder is mixed and leached with the first mixed solution, so as to obtain a third mixed solution and a third filter residue after solid-liquid separation;

[0018] An alkali solution is added into the third mixed solution, and the pH of the third mixed solution is increased to 2-3.

[0019] According to an optional embodiment, the alkali solution is one or more of NaOH, Na2CO3, NaHCO3, Na3PO4, KOH, K2CO3 and KHCO3.

[0020] According to an optional embodiment, when the battery black powder is added into the first mixed solution, the liquid-solid ratio of the first mixed solution to the battery black powder is 3-6:1; and / or, the temperature when the battery black powder is mixed and leached with the first mixed solution is room temperature, and the time is 1.5-3h.

[0021] According to an optional embodiment, when the lithium extraction residue is mixed with the acid liquor, water is also added to the lithium extraction residue, and the mass ratio of the lithium extraction residue, the acid liquor and the water is 1:0.8-1.5:2-5, wherein the acid liquor is sulfuric acid with a concentration of 98%; or when the lithium extraction residue is mixed with the acid liquor, the mass ratio of the lithium extraction residue and the acid liquor is 1:2-8, wherein the acid liquor is dilute sulfuric acid with a concentration of 25%-35%.

[0022] According to an optional embodiment, when the lithium extraction residue is mixed with the acid liquor for leaching, the temperature is 20-90 DEG C, and the time is 1.5-3h.

[0023] According to an optional embodiment, when the iron-containing filtrate is added to the phosphorus iron residue, the liquid-solid ratio of the iron-containing filtrate to the phosphorus iron residue is 8-12:1; and / or, when the iron-containing filtrate reacts with the phosphorus iron residue, the temperature is 50-90 DEG C, and the time is 1.5-3h.

[0024] The battery-grade iron phosphate of the present application is prepared by using the lithium extraction residue as raw material and by using the method for preparing battery-grade iron phosphate from lithium extraction residue according to any one of the technical solutions of the present application.

[0025] The technical solution adopted by the present application can achieve the following beneficial effects:

[0026] The method for preparing battery-grade iron phosphate from lithium extraction residue of the present application can realize gradient utilization of acid liquor, and can treat the lithium extraction residue and the phosphorus iron residue, thereby realizing the treatment of waste with waste. Compared with the prior art, the present application can improve the utilization rate of acid liquor, and can avoid using expensive iron powder as a reducing agent, thereby reducing the treatment cost of the lithium extraction residue and the phosphorus iron residue and improving the economic benefit of the lithium extraction residue treatment.

[0027] In addition, the preferred technical solution of the present application also has the following technical effects:

[0028] The method for preparing battery-grade iron phosphate from lithium extraction residue provided by the application adds battery black powder into the first mixed solution and makes the battery black powder mixed and leached with the first mixed solution, in the process, the battery black powder can be leached by the acidity of the first mixed solution, so that the method for preparing battery-grade iron phosphate from lithium extraction residue can realize the treatment of three wastes, i.e., lithium extraction residue, phosphorus iron residue and battery black powder, and fully realizes the treatment of waste with waste; on the other hand, the acidity of the first mixed solution can be consumed by the battery black powder, so that the pH of the first mixed solution is increased, and the amount of lye used in the subsequent pH adjustment of the solution can be greatly reduced, so that the treatment cost of the lithium extraction residue can be further reduced and the economic benefit can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0030] Figure 1 is the XRD pattern of the iron phosphate obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of the present application.

[0032] The terms "first", "second" and the like in the specification and claims of the present application are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second" and the like are generally of a kind, not limited to the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / ", generally means that the objects before and after are in an "or" relationship.

[0033] In the related art, when the lithium extraction residue is recycled, the lithium extraction residue is usually mixed with sulfuric acid, trivalent iron in the lithium extraction residue is leached into the solution, and then the trivalent iron is reduced to divalent iron by using a reducing agent such as iron powder; then the pH of the solution is adjusted by adding sodium hydroxide, so that the metal ions such as aluminum, titanium, chromium and calcium in the solution are precipitated, and the divalent iron ions remain in the solution, and then the phosphorus iron is obtained by adding hydrogen peroxide. In this process, the amount of acid, reducing agent and alkali is large, especially the cost of reducing agent and alkali is high, which leads to low economic benefit of the traditional recycling method.

[0034] Therefore, the method for preparing battery-grade phosphorus iron by using lithium extraction residue is used to add phosphorus iron residue into the iron-containing filtrate, which can leach the phosphorus iron residue by using the acidity of the iron-containing filtrate, and reduce the trivalent iron in the iron-containing filtrate to divalent iron by using the reducing property of the phosphorus iron residue, so as to improve the utilization rate of the acid and avoid using expensive iron powder as a reducing agent, thereby improving the economic benefit of the lithium extraction residue treatment.

[0035] The method for preparing battery-grade phosphorus iron by using lithium extraction residue comprises the following steps:

[0036] Step 100: The lithium extraction residue is mixed with acid to leach out, and after solid-liquid separation, an iron-containing filtrate and a first filter residue are obtained. Preferably, when the lithium extraction residue is mixed with the acid, water is also added to the lithium extraction residue, and the mass ratio of the lithium extraction residue, the acid and the water is 1:0.8-1.5:2-5, wherein the acid is sulfuric acid with a concentration of 98%. Preferably, when the lithium extraction residue is mixed with the acid, the mass ratio of the lithium extraction residue and the acid is 1:2-8, wherein the acid is dilute sulfuric acid with a concentration of 25%-35%.

[0037] Preferably, the temperature for mixing the lithium extraction residue with the acid to leach out is 20-90℃, and the time is 1.5-3h. More preferably, the temperature for mixing the lithium extraction residue with the acid to leach out is 80-90℃, and the time is 1.5-2h. Especially preferably, the temperature for mixing the lithium extraction residue with the acid to leach out is 90℃, and the time is 2h.

[0038] Step 200: The phosphorus iron residue is added to the iron-containing filtrate, and the phosphorus iron residue reacts with the iron-containing filtrate, and after solid-liquid separation, a first mixed solution is obtained, wherein the phosphorus iron residue is one or more of FeP, Fe2P and Fe3P. Exemplarily, the phosphorus iron residue is derived from the by-product waste residue in yellow phosphorus production.

[0039] Preferably, when the phosphorus iron residue is added to the iron-containing filtrate, the liquid-solid ratio of the iron-containing filtrate to the phosphorus iron residue is 8-12:1. The uncompletely leached phosphorus iron residue is recovered and added to the next batch of iron-containing filtrate for continuous reaction (a small amount of fresh phosphorus iron residue can be supplemented to the recovered phosphorus iron residue).

[0040] Preferably, the temperature of the iron-containing filtrate reacting with the phosphorus-iron residue is 50-90°C, and the time is 1.5-3h. More preferably, the temperature of the iron-containing filtrate reacting with the phosphorus-iron residue is 80-90°C, and the time is 1.5-2h.

[0041] Step 300: adjusting the pH of the first mixed solution to obtain a second mixed solution and a second filter residue after solid-liquid separation. By adjusting the pH of the first mixed solution, the metal ions such as aluminum, titanium, chromium, calcium and the like in the solution can be precipitated in the form of precipitate, providing a basis for preparing the battery-grade iron phosphate product.

[0042] Step 400: adding an oxidizing agent to the second mixed solution to oxidize the divalent iron in the second mixed solution to obtain a first reaction liquid containing iron phosphate precipitate, filtering the first reaction liquid, and obtaining iron phosphate dihydrate product by washing and drying the obtained precipitate. Exemplarily, the oxidizing agent is hydrogen peroxide. The process of adding an oxidizing agent to the second mixed solution to prepare iron phosphate is the existing technology, which will not be described here.

[0043] The method for preparing battery-grade iron phosphate from lithium extraction residue in the present application is as follows: after the lithium extraction residue is mixed with acid solution for leaching, the metal elements in the lithium extraction residue are dissolved in the acid solution, the obtained iron-containing filtrate is filtered, and the iron-containing filtrate still has acidity. At this time, the iron-containing filtrate is added to the phosphorus-iron residue, and the acidity of the iron-containing filtrate can be used to leach the phosphorus-iron residue, and the reducing property of the phosphorus-iron residue can be used to reduce the trivalent iron in the iron-containing filtrate to divalent iron, thereby providing a basis for the subsequent impurity removal of the iron-containing filtrate. This method can realize the gradient utilization of acid solution, and can treat the two kinds of waste residues of lithium extraction residue and phosphorus-iron residue, realize the treatment of waste with waste, compared with the existing method, the utilization rate of acid solution can be improved, and the use of expensive iron powder as a reducing agent can be avoided, thereby reducing the treatment cost of lithium extraction residue and phosphorus-iron residue and improving the economic benefit of lithium extraction residue treatment.

[0044] In some embodiments, the method for preparing battery-grade iron phosphate from lithium extraction residue further comprises the following steps:

[0045] After filtering the reaction liquid containing iron phosphate precipitate, sodium carbonate is added to the obtained filtrate, and lithium carbonate precipitate is obtained after reaction. The second reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain lithium carbonate product. Alternatively, after filtering the reaction liquid containing iron phosphate precipitate, phosphoric acid is added to the obtained filtrate, and lithium dihydrogen phosphate solution is obtained after reaction. Lithium dihydrogen phosphate product is obtained by concentration, crystallization and drying. Not limited to this, the filtrate can also be used to prepare lithium phosphate, lithium hydroxide and other products.

[0046] The lithium extraction residue is the material after lithium extraction from battery waste. However, due to the process limitation, the lithium extraction process cannot realize the complete recovery of lithium, and a small amount of lithium still remains in the lithium extraction residue. The lithium content in the lithium extraction residue is several thousand ppm after detection. The method for preparing battery-grade iron phosphate from lithium extraction residue in the application can extract lithium from the obtained filtrate by precipitation or crystallization process to prepare lithium products, which can not only further improve the economic benefit of lithium extraction residue treatment, but also avoid the environmental pollution problem caused by direct discharge of the filtrate.

[0047] In some embodiments, the method for preparing battery-grade iron phosphate from lithium extraction residue further comprises the following step: stepwise recovery of metal elements in the second filtration residue. When the pH of the first mixed solution is increased to 2-3, the metal ions such as aluminum, titanium, chromium and calcium in the solution are precipitated in the form of precipitate, and after solid-liquid separation, they enter the second filtration residue. By stepwise recovery of metal elements in the second filtration residue, not only the economic benefit of lithium extraction residue treatment can be further improved, but also the environmental pollution problem caused by direct discharge of the filtrate can be avoided.

[0048] Through the above scheme, the complete component recovery in the lithium extraction residue can be realized, which greatly improves the economic benefit of lithium extraction residue treatment and reduces the harm of the emissions to the environment.

[0049] In some embodiments, an alkali solution is added to the first mixed solution, and the pH of the first mixed solution is increased to 2-3. Preferably, the alkali solution is one or more of NaOH, Na2CO3, NaHCO3, Na3PO4, KOH, K2CO3, and KHCO3. More preferably, the alkali solution is NaOH. Without being limited thereto, the remaining alkali solutions can also be used.

[0050] In some embodiments, after obtaining the first mixed solution, the following steps are further included: adding battery black powder to the first mixed solution, and mixing and leaching the battery black powder with the first mixed solution, to obtain a third mixed solution and a third filtration residue after solid-liquid separation; adding an alkali solution to the third mixed solution, and increasing the pH of the third mixed solution to 2-3. Preferably, the alkali solution is one or more of NaOH, Na2CO3, NaHCO3, Na3PO4, KOH, K2CO3, and KHCO3. More preferably, the alkali solution is NaOH. Without being limited thereto, the remaining alkali solutions can also be used.

[0051] After obtaining the first mixed solution, the battery black powder is added to the first mixed solution, and the battery black powder is mixed and leached with the first mixed solution. In this process, the battery black powder can be leached by the acidity of the first mixed solution, so that the method for preparing battery-grade iron phosphate from lithium extraction residue can realize the treatment of three wastes, i.e., lithium extraction residue, phosphorus iron residue and battery black powder, and fully realize the "waste treatment with waste". On the other hand, the acidity of the first mixed solution can be consumed by the battery black powder, so that the pH of the first mixed solution is increased (specifically, the pH can be increased from-0.07 to about 1.0). When the pH of the solution is adjusted subsequently, the amount of alkali solution can be greatly reduced, thereby further reducing the treatment cost of lithium extraction residue and improving economic benefits.

[0052] In some embodiments, when the battery black powder is added to the first mixed solution, the liquid-solid ratio of the first mixed solution to the battery black powder is 3-6:1. For example, when the liquid-solid ratio of the first mixed solution to the battery black powder is 5:1, the pH of the first mixed solution can be increased to 1.03. The battery black powder that is not completely dissolved in the reaction can be recovered and reused; or acid solution can be added to the first mixed solution at the same time, so that the lithium iron phosphate in the battery black powder is completely dissolved in the solution, and the recovery of lithium iron phosphate in the battery black powder is realized.

[0053] In some embodiments, the temperature of the battery black powder mixed with the first mixed solution is room temperature, and the time is 1.5-3h. Preferably, the time of the battery black powder mixed with the first mixed solution is 1.5-2h. More preferably, the time of the battery black powder mixed with the first mixed solution is 2h.

[0054] The battery-grade iron phosphate of the present application is prepared by using any one of the methods for preparing battery-grade iron phosphate from lithium extraction residue in the present application, using lithium extraction residue as raw material. The battery-grade iron phosphate obtained by the present application has low cost and high quality, and can be used in the field of battery preparation. Specifically, the purity of the battery-grade iron phosphate obtained by the present application is as high as 99.98%. The impurities and contents in the iron phosphate are detected by ICP-MS, and the impurity content in the iron phosphate is within 50ppm.

[0055] The method for preparing battery-grade iron phosphate from lithium extraction residue and the battery-grade iron phosphate provided by the present application will be described in detail below through specific embodiments.

[0056] The compositions of the raw material residues used in each embodiment are detected.

[0057] Lithium extraction residue: derived from the waste residue after lithium extraction from lithium iron phosphate enterprises, the main components are phosphorus and iron. Specifically, the iron content in the lithium extraction residue is 30.54%, the phosphorus content is 16.54%, and the lithium extraction residue also contains a large amount of other elements, including 1942ppm of residual lithium, 1420ppm of sodium, 73ppm of magnesium, 7504ppm of aluminum, 235ppm of potassium, 850ppm of calcium, 9ppm of titanium, 18ppm of vanadium, 19ppm of chromium, 295ppm of manganese, 113ppm of cobalt, 350ppm of nickel, 560ppm of copper, 12ppm of zinc, 6ppm of arsenic, 0.1ppm of cadmium, and 3ppm of lead.

[0058] Phosphorus iron residue: derived from the by-product of yellow phosphorus production, the main components are phosphorus and iron. Specifically, the iron content in the phosphorus iron residue is 65.05%, the phosphorus content is 21.54%, and the lithium extraction residue also contains a large amount of other elements, including 158ppm of sodium, 816ppm of magnesium, 757ppm of aluminum, 311ppm of potassium, 15072ppm of calcium, 6028ppm of titanium, 2139ppm of vanadium, 1451ppm of chromium, 24781ppm of manganese, 207ppm of cobalt, 1005ppm of nickel, 688ppm of copper, 72ppm of zinc, 5ppm of arsenic, and 152ppm of lead.

[0059] Battery black powder: derived from battery recycling manufacturers, the main components are lithium, phosphorus and iron. Specifically, the iron content in the battery black powder is 23.79%, the phosphorus content is 11.30%, and the lithium content is 33132ppm, and the battery black powder also contains a large amount of other elements, including 1340ppm of sodium, 49ppm of magnesium, 16495ppm of aluminum, 130ppm of potassium, 438ppm of calcium, 1187ppm of titanium, 122ppm of vanadium, 30ppm of chromium, 4532ppm of manganese, 3864ppm of cobalt, 3127ppm of nickel, 16045ppm of copper, 31ppm of zinc, 8ppm of arsenic, 9ppm of cadmium, and 12ppm of lead.

[0060] Example 1

[0061] The method for preparing battery-grade iron phosphate from lithium extraction residue in this embodiment includes the following steps:

[0062] Step 100: Take 100 g of lithium extraction residue, 120 g of 98% sulfuric acid, and 280 g of water, mix them together, and heat to 90°C. Soak the mixture for 2 hours under stirring. After filtration, obtain the iron-containing filtrate and the first filter residue.

[0063] Step 200: Take 200 g of the iron-containing filtrate, add 20 g of phosphorus-iron residue to the iron-containing filtrate, mix them well, heat to 90°C, and react for 2 hours under stirring. After solid-liquid separation, obtain the first mixed solution.

[0064] Step 300: The pH of the first mixed solution is -0.07. Add NaOH to the first mixed solution to adjust the pH to 2. The total amount of NaOH added is 38.5 g. After filtration, obtain the second mixed solution and the second filter residue.

[0065] Step 400: Add excess hydrogen peroxide to the second mixed solution. Specifically, the amount of hydrogen peroxide added is 12.5 g. React the second mixed solution and the hydrogen peroxide at 45°C for 1 hour to obtain the first reaction solution containing iron phosphate precipitate. Filter the first reaction solution, and obtain the iron phosphate product after washing and drying the precipitate.

[0066] After detection, the iron phosphate dihydrate obtained in this embodiment is 42.6 g, the purity of the iron phosphate is 99.98%, and the impurities in the iron phosphate are shown in Table 1.

[0067] Table 1: Impurity elements and contents of iron phosphate in Example 1

[0068]

[0069] Figure 1 The XRD pattern of the iron phosphate in this embodiment is also shown. From the XRD pattern, Figure 1 It can be seen that the purity of the iron phosphate obtained in this embodiment is high, and there is almost no impurity peak.

[0070] Example 2

[0071] The method for preparing battery-grade iron phosphate from lithium extraction residue in this embodiment includes the following steps:

[0072] Step 100: Take 100 g of lithium extraction residue, 120 g of 98% sulfuric acid, and 280 g of water, mix them together, and heat to 90°C. Soak the mixture for 2 hours under stirring. After filtration, obtain the iron-containing filtrate and the first filter residue.

[0073] Step 200: Take 200 g of the iron-containing filtrate, add 20 g of phosphorus-iron residue to the iron-containing filtrate, mix them well, heat to 90°C, and react for 2 hours under stirring. After solid-liquid separation, obtain the first mixed solution.

[0074] Step 300: The pH of the first mixed solution is -0.07, battery black powder is added to the first mixed solution, the liquid-solid ratio of the first mixed solution to the battery black powder is 5:1, the first mixed solution and the battery black powder are reacted at room temperature under stirring for 2h, and after solid-liquid separation, a third mixed solution and a third filter residue are obtained. The pH of the third mixed solution is increased to 1.03.

[0075] NaOH is added to the third mixed solution, and the pH of the third mixed solution is increased to 2, and the total amount of NaOH added is 8.3g. After filtration, a second mixed solution and a second filter residue are obtained.

[0076] Step 400: Excess hydrogen peroxide is added to the second mixed solution, specifically, the amount of hydrogen peroxide added is 12.5g, the second mixed solution and the hydrogen peroxide are reacted at 45℃ for 1h to obtain a first reaction liquid containing iron phosphate precipitate, the first reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain iron phosphate dihydrate product.

[0077] It is detected that the iron phosphate dihydrate obtained in this embodiment is 40.3g, and the purity of the iron phosphate is 99.98%. The impurities and contents of the iron phosphate are detected by ICP-MS, and the impurities in the iron phosphate are shown in Table 2.

[0078] Table 2 Impurity elements and contents of iron phosphate in Example 2

[0079]

[0080] Example 3

[0081] The method for preparing battery-grade iron phosphate from lithium extraction residue in this embodiment comprises the following steps:

[0082] Step 100: Take 100g of lithium extraction residue, 120g of 98% concentrated sulfuric acid, and 280g of water, mix them together, and heat to 90℃. The mixed solution is leached under stirring for 2h. After filtration, an iron-containing filtrate and a first filter residue are obtained.

[0083] Step 200: Take 200g of the iron-containing filtrate, add 20g of phosphorus iron residue to the iron-containing filtrate, mix the phosphorus iron residue and the iron-containing filtrate uniformly, heat to 90℃, and the mixed solution is reacted under stirring for 2h. After solid-liquid separation, a first mixed solution is obtained.

[0084] Step 300: The pH of the first mixed solution is -0.07, battery black powder is added to the first mixed solution, the liquid-solid ratio of the first mixed solution to the battery black powder is 5:1, the first mixed solution and the battery black powder are reacted at room temperature under stirring for 2h, and after solid-liquid separation, a third mixed solution and a third filter residue are obtained. The pH of the third mixed solution is increased to 1.03.

[0085] NaOH was added to the third mixed solution, and the pH of the third mixed solution was increased to 2, and the total amount of NaOH added was 5.6 g. After filtration, a second mixed solution and a second filter residue were obtained.

[0086] Step 400: Excess hydrogen peroxide was added to the second mixed solution, specifically, the amount of hydrogen peroxide added was 12.5 g, and the second mixed solution and hydrogen peroxide were reacted at 45°C for 1 hour to obtain a first reaction liquid containing iron phosphate precipitate. The first reaction liquid was filtered, and the obtained precipitate was washed and dried to obtain iron phosphate dihydrate product.

[0087] It was detected that the iron phosphate dihydrate obtained in this embodiment was 42.5 g, and the purity of the iron phosphate was 99.98%. The impurities and contents of the iron phosphate were detected by ICP-MS, and the impurities in the iron phosphate were as shown in Table 3.

[0088] Table 3 Impurity elements and contents of iron phosphate in Example 3

[0089]

[0090] Example 4

[0091] The method for preparing battery-grade iron phosphate from lithium extraction residue in this embodiment comprises the following steps:

[0092] Step 100: Take 100 g of lithium extraction residue, 120 g of 98% sulfuric acid, and 280 g of water, mix them, and heat to 90°C. The mixed solution is leached for 2 hours under stirring. After filtration, an iron-containing filtrate and a first filter residue are obtained.

[0093] Step 200: Take 200 g of the iron-containing filtrate, and add 20 g of phosphorus iron residue to the iron-containing filtrate. Mix the phosphorus iron residue and the iron-containing filtrate, heat to 90°C, and react the mixed solution under stirring for 2 hours. After solid-liquid separation, a first mixed solution is obtained.

[0094] Step 300: The pH of the first mixed solution is -0.07, battery black powder is added to the first mixed solution, and the liquid-solid ratio of the first mixed solution to the battery black powder is 6:1. The first mixed solution and the battery black powder are reacted under stirring at room temperature for 2 hours. After solid-liquid separation, a third mixed solution and a third filter residue are obtained, and the pH of the third mixed solution is increased to 0.92.

[0095] NaOH was added to the third mixed solution, and the pH of the third mixed solution was increased to 2, and the total amount of NaOH added was 5.6 g. After filtration, a second mixed solution and a second filter residue were obtained.

[0096] Step 400: adding excess hydrogen peroxide to the second mixed solution, specifically, the amount of hydrogen peroxide added is 12.5 g, the second mixed solution and hydrogen peroxide are reacted at 45℃ for 1 hour to obtain a first reaction liquid containing iron phosphate precipitate, the first reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain iron phosphate dihydrate product.

[0097] It is detected that the iron phosphate dihydrate obtained in the embodiment is 40.1 g, and the purity of the iron phosphate is 99.98%. The impurities and contents of the iron phosphate are detected by ICP-MS, and the impurities of the iron phosphate are shown in Table 4.

[0098] Table 4 Impurity elements and contents of iron phosphate in Example 4

[0099]

[0100] Example 5

[0101] The method for preparing battery-grade iron phosphate from lithium extraction residue in the embodiment comprises the following steps:

[0102] Step 100: taking 100 g of lithium extraction residue, 120 g of 98% sulfuric acid, and 280 g of water, mixing them, and heating to 90℃, and then leaching the mixture under stirring for 2 hours. After filtration, an iron-containing filtrate and a first filter residue are obtained.

[0103] Step 200: taking 200 g of the iron-containing filtrate, adding 20 g of phosphorus iron residue to the iron-containing filtrate, mixing the phosphorus iron residue and the iron-containing filtrate, heating to 90℃, and then reacting the mixture under stirring for 2 hours. After solid-liquid separation, a first mixed solution is obtained.

[0104] Step 300: the pH of the first mixed solution is -0.07, battery black powder is added to the first mixed solution, the liquid-solid ratio of the first mixed solution to the battery black powder is 5:1, the first mixed solution and the battery black powder are reacted under stirring at room temperature for 2 hours, and after solid-liquid separation, a third mixed solution and a third filter residue are obtained, and the pH of the third mixed solution is increased to 1.03.

[0105] NaOH is added to the third mixed solution to increase the pH of the third mixed solution to 2.5, and the total amount of NaOH added is 9.0 g. After filtration, a second mixed solution and a second filter residue are obtained.

[0106] Step 400: adding excess hydrogen peroxide to the second mixed solution, specifically, the amount of hydrogen peroxide added is 12.5 g, the second mixed solution and hydrogen peroxide are reacted at 45℃ for 1 hour to obtain a first reaction liquid containing iron phosphate precipitate, the first reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain iron phosphate dihydrate product.

[0107] The obtained iron phosphate dihydrate in the embodiment is 40.2 g, and the purity of the iron phosphate is 99.98%. The impurities and content of the iron phosphate are detected by ICP-MS, and the impurities of the iron phosphate are shown in Table 5.

[0108] Table 5 Table of impurity elements and content of iron phosphate in Example 5

[0109]

[0110] Example 6

[0111] The method for preparing battery-grade iron phosphate from lithium extraction residue in the embodiment comprises the following steps:

[0112] Step 100: 100 g of lithium extraction residue, 120 g of 98% sulfuric acid, and 280 g of water are mixed, and the mixture is heated to 90°C. The mixed solution is leached for 2 h under stirring. After filtration, an iron-containing filtrate and a first filter residue are obtained.

[0113] Step 200: 200 g of the iron-containing filtrate is taken, and 20 g of phosphorus-iron residue is added to the iron-containing filtrate. After mixing the phosphorus-iron residue with the iron-containing filtrate, the mixture is heated to 90°C. The mixed solution is reacted for 2 h under stirring, and then solid-liquid separation is performed to obtain a first mixed solution.

[0114] Step 300: The pH of the first mixed solution is -0.07. Battery black powder is added to the first mixed solution, and the liquid-solid ratio of the first mixed solution to the battery black powder is 5:1. The first mixed solution and the battery black powder are reacted for 2 h under stirring at room temperature. After solid-liquid separation, a third mixed solution and a third filter residue are obtained, and the pH of the third mixed solution is increased to 1.03.

[0115] NaOH is added to the third mixed solution to increase the pH of the third mixed solution to 3. The total amount of NaOH added is 9.5 g. After filtration, a second mixed solution and a second filter residue are obtained.

[0116] Step 400: Excess hydrogen peroxide is added to the second mixed solution. Specifically, the amount of hydrogen peroxide added is 12.5 g. The second mixed solution and the hydrogen peroxide are reacted for 1 h at 45°C to obtain a first reaction liquid containing iron phosphate precipitate. The first reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain iron phosphate dihydrate product.

[0117] The obtained iron phosphate dihydrate in the embodiment is 39.8 g, and the purity of the iron phosphate is 99.98%. The impurities and content of the iron phosphate are detected by ICP-MS, and the impurities of the iron phosphate are shown in Table 6.

[0118] Table 6 Table of impurity elements and content of iron phosphate in Example 6

[0119]

[0120] Example 7

[0121] The method for preparing battery-grade iron phosphate from lithium extraction residue in this example comprises the following steps:

[0122] Step 100: Take 100 g of lithium extraction residue, 80 g of 98% sulfuric acid, and 200 g of water. Mix them together and heat to 90°C. Soak the mixture under stirring for 2 hours. After filtration, obtain the iron-containing filtrate and the first filter residue.

[0123] Step 200: Take 200 g of the iron-containing filtrate and add 20 g of phosphorus-iron residue to it. Mix the phosphorus-iron residue with the iron-containing filtrate and heat to 90°C. React the mixture under stirring for 2 hours. After solid-liquid separation, obtain the first mixed solution.

[0124] Step 300: The pH of the first mixed solution is 0.2. Add battery black powder to the first mixed solution. The liquid-solid ratio of the first mixed solution to the battery black powder is 5:1. React the mixture under stirring at room temperature for 2 hours. After solid-liquid separation, obtain the third mixed solution and the third filter residue. The pH of the third mixed solution is increased to 1.35.

[0125] Add NaOH to the third mixed solution to increase the pH of the third mixed solution to 2. The total amount of NaOH added is 5.6 g. After filtration, obtain the second mixed solution and the second filter residue.

[0126] Step 400: Add excess hydrogen peroxide to the second mixed solution. Specifically, the amount of hydrogen peroxide added is 12.5 g. React the second mixed solution and the hydrogen peroxide at 45°C for 1 hour to obtain the first reaction liquid containing iron phosphate precipitate. Filter the first reaction liquid. The obtained precipitate is washed and dried to obtain the iron phosphate dihydrate product.

[0127] After detection, the obtained iron phosphate dihydrate in this example is 38.5 g, and the purity of the iron phosphate is 99.98%. The impurities and contents of the iron phosphate are detected by ICP-MS. The impurities in the iron phosphate are shown in Table 7.

[0128] Table 7 Impurity elements and contents of iron phosphate in Example 7

[0129]

[0130] Example 8

[0131] The method for preparing battery-grade iron phosphate from lithium extraction residue in this example comprises the following steps:

[0132] Step 100: Take 100 g of lithium extraction residue, 150 g of 98% sulfuric acid, and 500 g of water, mix them together, and heat to 90°C. Soak the mixture for 2 hours under stirring. After filtration, obtain the filtrate containing iron and the first filter residue.

[0133] Step 200: Take 200 g of the filtrate containing iron, add 20 g of phosphorus-iron residue, mix them together, and heat to 90°C. React the mixture for 2 hours under stirring. After solid-liquid separation, obtain the first mixed solution.

[0134] Step 300: The pH of the first mixed solution is -0.23. Add battery black powder to the first mixed solution, and the liquid-solid ratio of the first mixed solution to the battery black powder is 5:1. React the mixture at room temperature for 2 hours under stirring. After solid-liquid separation, obtain the third mixed solution and the third filter residue. The pH of the third mixed solution is increased to 0.56.

[0135] Add NaOH to the third mixed solution to increase the pH of the third mixed solution to 2. The total amount of NaOH added is 15.7 g. After filtration, obtain the second mixed solution and the second filter residue.

[0136] Step 400: Add excess hydrogen peroxide to the second mixed solution. Specifically, the amount of hydrogen peroxide added is 12.5 g. React the second mixed solution and the hydrogen peroxide at 45°C for 1 hour to obtain the first reaction solution containing iron phosphate precipitate. Filter the first reaction solution, and obtain the iron phosphate precipitate after washing and drying. The product is iron phosphate dihydrate.

[0137] After detection, the amount of iron phosphate dihydrate obtained in this embodiment is 42.3 g, and the purity of iron phosphate is 99.98%. Use ICP-MS to detect the impurities and content of iron phosphate. The impurities in the iron phosphate are shown in Table 8.

[0138] Table 8: Impurity elements and content of iron phosphate in Example 8

[0139]

[0140] Example 9

[0141] The method for preparing battery-grade iron phosphate from lithium extraction residue in this embodiment includes the following steps:

[0142] Step 100: Take 100 g of lithium extraction residue, 120 g of 98% sulfuric acid, and 280 g of water, mix them together, and heat to 90°C. Soak the mixture for 2 hours under stirring. After filtration, obtain the filtrate containing iron and the first filter residue.

[0143] Step 200: Take 200 g of the iron-containing filtrate, and add 25 g of the phosphorus-iron slag to the iron-containing filtrate. After mixing the phosphorus-iron slag with the iron-containing filtrate, the temperature is increased to 90°C, and the mixed solution is reacted for 2 h under stirring. After solid-liquid separation, a first mixed solution is obtained.

[0144] Step 300: The pH of the first mixed solution is -0.07, and battery black powder is added to the first mixed solution. The liquid-solid ratio of the first mixed solution to the battery black powder is 5:1. The first mixed solution and the battery black powder are reacted for 2 h under stirring at room temperature. After solid-liquid separation, a third mixed solution and a third filter residue are obtained, and the pH of the third mixed solution is increased to 1.01.

[0145] NaOH is added to the third mixed solution, and the pH of the third mixed solution is increased to 2. The total amount of NaOH added is 8.4 g. After filtration, a second mixed solution and a second filter residue are obtained.

[0146] Step 400: Excess hydrogen peroxide is added to the second mixed solution. Specifically, the amount of hydrogen peroxide added is 12.5 g. The second mixed solution and the hydrogen peroxide are reacted for 1 h at 45°C to obtain a first reaction liquid containing iron phosphate precipitate. The first reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain a ferriphosphate dihydrate product.

[0147] It is detected that the ferriphosphate dihydrate obtained in this embodiment is 40.2 g, and the purity of the ferriphosphate is 99.98%. The impurities and contents of the ferriphosphate are detected by ICP-MS. The impurities of the ferriphosphate are shown in Table 9.

[0148] Table 9 Impurity elements and contents of the ferriphosphate in Example 9

[0149]

[0150] Example 10

[0151] The method for preparing battery-grade ferriphosphate from lithium extraction residue in this embodiment includes the following steps:

[0152] Step 100: Take 100 g of lithium extraction residue, 120 g of 98% concentrated sulfuric acid, and 280 g of water. After mixing the three, the temperature is increased to 90°C, and the mixed solution is leached for 2 h under stirring. After filtration, an iron-containing filtrate and a first filter residue are obtained.

[0153] Step 200: Take 200 g of the iron-containing filtrate, and add 16.7 g of the phosphorus-iron slag to the iron-containing filtrate. After mixing the phosphorus-iron slag with the iron-containing filtrate, the temperature is increased to 90°C, and the mixed solution is reacted for 2 h under stirring. After solid-liquid separation, a first mixed solution is obtained.

[0154] Step 300: The pH of the first mixed solution is -0.07. Battery black powder is added to the first mixed solution. The liquid-solid ratio of the first mixed solution to the battery black powder is 5:1. At room temperature, the first mixed solution and the battery black powder react under stirring for 2 hours. After solid-liquid separation, a third mixed solution and a third filter residue are obtained. The pH of the third mixed solution increases to 1.08.

[0155] NaOH was added to the third mixed solution to raise its pH to 2. The total amount of NaOH added was 8.3 g. After filtration, a second mixed solution and a second filter residue were obtained.

[0156] Step 400: Add excess hydrogen peroxide to the second mixed solution. Specifically, the amount of hydrogen peroxide added is 12.5g. The second mixed solution and hydrogen peroxide react at 45°C for 1 hour to obtain a first reaction solution containing ferric phosphate precipitate. Filter the first reaction solution, and wash and dry the precipitate to obtain ferric phosphate dihydrate product.

[0157] The obtained ferric phosphate dihydrate in this embodiment was 42.3 g, and the purity of ferric phosphate was 99.98%. ICP-MS was used to detect the impurities and their content in the ferric phosphate. The impurities in the ferric phosphate are shown in Table 10 below.

[0158] Table 10. Impurity elements and their contents in ferric phosphate in Example 10.

[0159]

[0160] Example 11

[0161] This embodiment describes a method for preparing battery-grade iron phosphate using lithium extraction slag, comprising the following steps:

[0162] Step 100: Take 100g of lithium residue, 120g of 98% sulfuric acid, and 280g of water. Mix the three together and heat to 80℃. Immerse the mixture in the solution for 1.5 hours while stirring. After filtration, obtain an iron-containing filtrate and the first filter residue.

[0163] Step 200: Take 200g of iron-containing filtrate, add 20g of phosphorus iron slag to the iron-containing filtrate, mix the phosphorus iron slag and iron-containing filtrate evenly, heat to 80℃, and react the mixed solution under stirring for 1.5h. After solid-liquid separation, the first mixed solution is obtained.

[0164] Step 300: The pH of the first mixed solution is -0.07. Battery black powder is added to the first mixed solution. The liquid-solid ratio of the first mixed solution to the battery black powder is 5:1. At room temperature, the first mixed solution and the battery black powder react under stirring for 1.5 hours. After solid-liquid separation, a third mixed solution and a third filter residue are obtained. The pH of the third mixed solution increases to 1.07.

[0165] NaOH was added to the third mixed solution, and the pH of the third mixed solution was increased to 2, and the total amount of NaOH added was 8.2 g. After filtration, a second mixed solution and a second filter residue were obtained.

[0166] Step 400: Excess hydrogen peroxide was added to the second mixed solution, specifically, the amount of hydrogen peroxide added was 12.5 g, and the second mixed solution and hydrogen peroxide were reacted at 45°C for 1 h to obtain a first reaction liquid containing iron phosphate precipitate. The first reaction liquid was filtered, and the obtained precipitate was washed and dried to obtain iron phosphate dihydrate product.

[0167] It was detected that the iron phosphate dihydrate obtained in this embodiment was 40.6 g, and the purity of the iron phosphate was 99.98%. The impurities in the iron phosphate are shown in Table 11.

[0168] Table 11 Impurity elements and contents of iron phosphate in Example 11

[0169]

[0170] Example 12

[0171] The method for preparing battery-grade iron phosphate from lithium extraction residue in this embodiment comprises the following steps:

[0172] Step 100: Take 100 g of lithium extraction residue, 120 g of 98% sulfuric acid, and 280 g of water, mix them, and soak the mixture at 20°C under stirring for 3 h. After filtration, an iron-containing filtrate and a first filter residue are obtained.

[0173] Step 200: Take 200 g of the iron-containing filtrate, and add 20 g of phosphorus iron residue to the iron-containing filtrate. After mixing the phosphorus iron residue with the iron-containing filtrate, heat to 50°C, and react the mixture under stirring for 3 h. After solid-liquid separation, a first mixed solution is obtained.

[0174] Step 300: The pH of the first mixed solution is -0.07, battery black powder is added to the first mixed solution, and the liquid-solid ratio of the first mixed solution to the battery black powder is 5:1. At room temperature, the first mixed solution and the battery black powder are reacted under stirring for 3 h, and after solid-liquid separation, a third mixed solution and a third filter residue are obtained, and the pH of the third mixed solution is increased to 1.12.

[0175] NaOH was added to the third mixed solution, and the pH of the third mixed solution was increased to 2, and the total amount of NaOH added was 8.2 g. After filtration, a second mixed solution and a second filter residue were obtained.

[0176] Step 400: adding excess hydrogen peroxide to the second mixed solution, specifically, the amount of hydrogen peroxide added is 12.5 g, the second mixed solution and the hydrogen peroxide are reacted at 45℃ for 1 hour to obtain a first reaction liquid containing iron phosphate precipitate, the first reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain iron phosphate dihydrate product.

[0177] It is detected that the iron phosphate dihydrate obtained in the embodiment is 41.3 g, and the purity of the iron phosphate is 99.98%. The impurities and contents of the iron phosphate are detected by ICP-MS, and the impurities of the iron phosphate are shown in Table 12.

[0178] Table 12 Impurity elements and contents of iron phosphate in Example 12

[0179]

[0180] Example 13

[0181] The method for preparing battery-grade iron phosphate from lithium extraction residue in the embodiment comprises the following steps:

[0182] Step 100: taking 100 g of lithium extraction residue, 120 g of 98% concentrated sulfuric acid, and 280 g of water, mixing them, and heating to 90℃, and then leaching the mixture under stirring for 2 hours. After filtration, an iron-containing filtrate and a first filter residue are obtained.

[0183] Step 200: taking 200 g of the iron-containing filtrate, adding 20 g of phosphorus iron residue to the iron-containing filtrate, mixing the phosphorus iron residue and the iron-containing filtrate, heating to 90℃, and then reacting the mixture under stirring for 2 hours. After solid-liquid separation, a first mixed solution is obtained.

[0184] Step 300: the pH of the first mixed solution is -0.07, battery black powder is added to the first mixed solution, the liquid-solid ratio of the first mixed solution to the battery black powder is 5:1, and the first mixed solution and the battery black powder are reacted under stirring at room temperature for 2 hours. After solid-liquid separation, a third mixed solution and a third filter residue are obtained, and the pH of the third mixed solution is increased to 1.03.

[0185] NaOH is added to the third mixed solution, and the pH of the third mixed solution is increased to 2, and the total amount of NaOH added is 8.3 g. After filtration, a second mixed solution and a second filter residue are obtained.

[0186] Step 400: adding excess hydrogen peroxide to the second mixed solution, specifically, the amount of hydrogen peroxide added is 12.5 g, the second mixed solution and hydrogen peroxide are reacted at 45℃ for 1 hour to obtain a first reaction liquid containing iron phosphate precipitate, the first reaction liquid is filtered, and the obtained precipitate is washed, dried and then iron phosphate dihydrate product is obtained. 16 g of sodium carbonate is added to the obtained filtrate, and the mixture is reacted at 45℃ for 1 hour to obtain a second reaction liquid containing lithium carbonate precipitate, the second reaction liquid is filtered, and the obtained precipitate is washed, dried and then lithium carbonate product is obtained.

[0187] It is detected that the iron phosphate dihydrate obtained in the embodiment is 40.3 g, and the purity of the iron phosphate is 99.98%. The impurities and content of the iron phosphate are detected by ICP-MS, and the impurities in the iron phosphate are shown in Table 13.

[0188] Table 13 Impurity elements and content table of iron phosphate in Example 13

[0189]

[0190] It is detected that the lithium carbonate obtained in the embodiment is 11.8 g, and the purity of the lithium carbonate is 99.99%. The impurities and content of the lithium carbonate are detected by ICP-MS, and the impurities in the lithium carbonate are shown in Table 14.

[0191] Table 14 Impurity elements and content table of lithium carbonate in Example 14

[0192]

[0193] It is to be understood that the terms "including", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that processes, methods, articles, or apparatuses that comprise a list of elements are not to be construed as consisting only of those elements, but can include other elements not expressly listed or inherent to such processes, methods, articles, or apparatuses. Without further limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0194] In addition, it should be noted that the scope of the methods and apparatuses in the embodiments of the present application is not limited to performing functions in the order shown or discussed, but can also include performing functions in a substantially simultaneous manner or in a reverse order, for example, the described method can be performed in an order different from that described, and various steps can also be added, omitted, or combined. In addition, the features described with reference to certain examples can be combined in other examples.

[0195] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for preparing battery-grade iron phosphate using lithium extraction residue, characterized in that, The method comprises the following steps: The lithium extraction residue is mixed with acid solution for leaching, and after solid-liquid separation, an iron-containing filtrate and a first filter residue are obtained, wherein the lithium extraction residue is the waste residue after lithium extraction in a lithium iron phosphate enterprise; Phosphorus iron residue is added to the iron-containing filtrate, and the phosphorus iron residue reacts with the iron-containing filtrate, and after solid-liquid separation, a first mixed solution is obtained, wherein the phosphorus iron residue is one or more of FeP, Fe2P and Fe3P; The pH of the first mixed solution is adjusted to make aluminum ions, titanium ions, chromium ions and calcium ions in the solution precipitate, and after solid-liquid separation, a second mixed solution and a second filter residue are obtained; An oxidizing agent is added to the second mixed solution to oxidize the divalent iron in the second mixed solution to obtain a first reaction liquid containing iron phosphate precipitate, and the first reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain iron phosphate dihydrate product. 2.The method for preparing battery-grade iron phosphate by using lithium extraction residue according to claim 1, characterized in that, The method further comprises the following steps: After the reaction liquid containing iron phosphate precipitate is filtered, sodium carbonate is added to the obtained filtrate, and after reaction, a second reaction liquid containing lithium carbonate precipitate is obtained, and the second reaction liquid is filtered, and the obtained precipitate is washed and dried to obtain lithium carbonate product; Or, after the reaction liquid containing iron phosphate precipitate is filtered, phosphoric acid is added to the obtained filtrate, and after reaction, lithium dihydrogen phosphate solution is obtained, and after concentration, crystallization and drying, lithium dihydrogen phosphate product is obtained. 3.The method for preparing battery-grade iron phosphate by using lithium extraction residue according to claim 1, characterized in that, Alkaline solution is added to the first mixed solution, and the pH of the first mixed solution is increased to 2-3. 4.The method for preparing battery-grade iron phosphate by using lithium extraction residue according to claim 1, characterized in that, After the first mixed solution is obtained, the following steps are further included: Battery black powder is added to the first mixed solution, and the battery black powder is mixed with the first mixed solution for leaching, and after solid-liquid separation, a third mixed solution and a third filter residue are obtained; Alkaline solution is added to the third mixed solution, and the pH of the third mixed solution is increased to 2-3.

5. The method for preparing battery-grade iron phosphate by using lithium extraction residue according to claim 3 or 4, characterized in that, The alkaline solution is one or more of NaOH, Na2CO3, NaHCO3, Na3PO4, KOH, K2CO3 and KHCO3. 6.The method for preparing battery-grade iron phosphate by using lithium extraction residue according to claim 4, characterized in that, When the battery black powder is added to the first mixed solution, the liquid-solid ratio of the first mixed solution to the battery black powder is 3-6:1; And / or, the temperature when the battery black powder is mixed with the first mixed solution for leaching is room temperature, and the time is 1.5-3h. 7.The method for preparing battery-grade iron phosphate by using lithium extraction residue according to claim 1, characterized in that, When the lithium extraction residue is mixed with the acid solution, water is also added to the lithium extraction residue, and the mass ratio of the lithium extraction residue, the acid solution and the water is 1:0.8-1.5:2-5, wherein the acid solution is sulfuric acid with a concentration of 98%; Or, when the lithium extraction residue is mixed with the acid solution, the mass ratio of the lithium extraction residue to the acid solution is 1:2-8, wherein the acid solution is dilute sulfuric acid with a concentration of 25%-35%. 8.The method for preparing battery-grade iron phosphate by using lithium extraction residue according to claim 7, characterized in that, The temperature when the lithium extraction residue is mixed with the acid solution for leaching is 20-90℃, and the time is 1.5-3h. 9.The method for preparing battery-grade iron phosphate by using lithium extraction residue according to claim 1, characterized in that, When the phosphorus iron residue is added to the iron-containing filtrate, the liquid-solid ratio of the iron-containing filtrate to the phosphorus iron residue is 8-12:1; And / or, the temperature when the iron-containing filtrate reacts with the phosphorus iron residue is 50-90℃, and the time is 1.5-3h.

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