Method for co-recovering waste lithium iron phosphate and lithium manganese iron phosphate

Abstract

The invention discloses a method for co-recycling waste lithium iron phosphate and lithium manganese iron phosphate, and relates to the technical field of lithium batteries. Waste lithium iron phosphate powder and waste lithium iron manganese phosphate powder are used for oxidation acid leaching, so that lithium is fully leached into an acid leaching solution, and iron and manganese enter a solid material to serve as an iron source and a manganese source; carrying out alkalization treatment on the pickle liquor to obtain lithium carbonate as a lithium source; the lithium manganese iron phosphate is prepared by taking an iron source, a manganese source and a lithium source as raw materials. According to the recovery method provided by the invention, manganese, iron and lithium can be efficiently recovered in a green and pollution-free manner, and the prepared lithium manganese iron phosphate positive electrode material is long in cycle life, high in energy density and relatively good in electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate. Background Art

[0002] Currently, lithium iron phosphate batteries account for more than one-third of the market share. As time goes by, a large number of retired batteries will be produced. Therefore, the reuse of waste lithium iron phosphate batteries is very important. It is necessary not only to minimize the harm of recycling to the environment, but also to improve the utilization effect. The current recycling process is difficult to balance the economy and environmental protection. The recycling of lithium iron phosphate battery materials requires multiple links, including battery disassembly, material separation, purification, etc., and each link requires a lot of equipment, manpower and energy.

[0003] For example, processes such as high-temperature roasting and wet leaching require a large amount of heat energy and chemical reagents, resulting in high recycling costs. During the recycling process, a large amount of wastewater, waste gas, waste residue and other wastes will be generated. If not handled properly, it will cause serious pollution to the environment. For example, the acid-containing wastewater generated during the wet leaching process needs to be neutralized, precipitated and other treatments before it can be discharged, and the waste residue may contain harmful substances such as heavy metals and need to be safely disposed of. These environmental protection treatment requirements increase the operating costs and technical difficulties of recycling companies. How to meet environmental protection requirements while ensuring the economy of the recycling process is an urgent problem to be solved.

[0004] In addition, it is difficult to repair and regenerate the performance of recycled waste batteries. After long-term use, the crystal structure of the positive electrode material of the iron-lithium battery will change, such as lattice distortion and particle agglomeration, resulting in a decrease in the electrochemical performance of the material. During the recycling process, the crystal structure of the positive electrode material needs to be repaired to restore its electrochemical performance.

[0005] Current recycling methods can be divided into direct regeneration, pyrometallurgy and hydrometallurgy:

[0006] (1) The direct regeneration method is to calcine the waste iron-lithium material together with the lithium source at high temperature to compensate for the lost lithium, repair the damaged crystal structure, and restore its previous electrochemical properties. However, there are many impurities and its electrical properties are far from the original.

[0007] (2) Pyrometallurgy is a process with high energy consumption and equipment costs, which to some extent hinders its application.

[0008] (3) Hydrometallurgy has become the mainstream method for recycling waste lithium iron. It mainly uses oxidative acid leaching process, such as sulfuric acid and phosphoric acid, and then uses suitable reagents for separation and purification. However, the cost is still high, and the consumption of chemical substances is accompanied by the generation of secondary pollution.

[0009] At present, the recovery of lithium iron phosphate is mainly for lithium recovery, and the FePO 4 ·2H 2 O is directly discarded as the residue of lithium extraction. Therefore, it is urgent to develop a simple, efficient, green and low-cost method to recover iron, manganese and lithium.

[0010] In view of this, the present invention is proposed. Summary of the invention

[0011] The purpose of the present invention is to provide a method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate, aiming to provide a simple and easy method for co-recovering manganese, iron and lithium.

[0012] The present invention is achieved in that:

[0013] In a first aspect, the present invention provides a method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate, comprising:

[0014] Mixing the waste lithium iron phosphate powder and the waste lithium iron manganese phosphate powder, performing acid leaching in a mixed acid solution containing an oxidant and an organic acid, and obtaining a solid material and an acid leaching solution after solid-liquid separation;

[0015] Using solid materials as iron and manganese sources;

[0016] The acid leaching solution is subjected to alkalization treatment, and lithium carbonate is obtained after solid-liquid separation, and the lithium carbonate is used as a lithium source;

[0017] Lithium iron manganese phosphate is prepared using iron source, manganese source and lithium source as raw materials.

[0018] In an optional embodiment, the oxidant in the mixed acid solution is selected from at least one of hydrogen peroxide (e.g., saturated hydrogen peroxide) and hypochlorous acid solution;

[0019] Preferably, the volume fraction of the oxidant in the mixed acid solution is 1%-20%.

[0020] In an optional embodiment, the organic acid in the mixed acid solution is selected from at least one of acetic acid, propionic acid, tartaric acid, oxalic acid, malic acid, citric acid and ascorbic acid;

[0021] Preferably, the concentration of the organic acid in the mixed acid solution is 0.1 mol / L-4 mol / L.

[0022] In an optional embodiment, the amount of the mixed acid solution is adjusted to make the material-liquid ratio 5g / L-25g / L.

[0023] In an optional embodiment, the acid leaching temperature is 20°C-60°C, and the acid leaching time is 10min-40min;

[0024] Preferably, the acid leaching is followed by water washing and then solid-liquid separation.

[0025] In an alternative embodiment, the solid material is dried and used as the iron and manganese source.

[0026] In an optional embodiment, the process of alkalizing the acid leaching solution includes: introducing carbon dioxide or adding sodium carbonate into the acid leaching solution, and performing solid-liquid separation after no solid is deposited.

[0027] In an optional embodiment, the iron source, manganese source, lithium source and carbon source are mixed and then sintered once; the sintered material obtained by the primary sintering is ball-milled and then sintered twice;

[0028] Preferably, the sintering temperature of the primary sintering is 450°C-550°C, and the sintering time is 3h-10h;

[0029] Preferably, the sintering temperature of the secondary sintering is 600° C.-700° C., and the sintering time is 5 h-15 h.

[0030] In an optional embodiment, by adjusting the amount of iron source, manganese source, lithium source and carbon source, the molar ratio of Fe, Mn, Li and organic carbon in the raw material is 1: (0.8-1.2): (1.8-2.2): (1.0-1.5).

[0031] In an alternative embodiment, the organic carbon is selected from at least one of glucose, sucrose and polyethylene glycol.

[0032] The present invention has the following beneficial effects: the present invention utilizes waste lithium iron phosphate powder and waste lithium iron manganese phosphate powder for oxidative acid leaching, so that lithium is fully leached into the acid leaching solution, and iron and manganese enter the solid material as iron source and manganese source; the acid leaching solution is alkalized to obtain lithium carbonate as a lithium source; and lithium iron manganese phosphate is prepared using iron source, manganese source and lithium source as raw materials. The recovery method provided by the present invention can efficiently, greenly and pollution-freely recover manganese, iron and lithium, and the prepared lithium iron manganese phosphate positive electrode material has a long cycle life, high energy density and good electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 A process flow chart of a method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate provided in an embodiment of the present invention;

[0035] Figure 2The EIS spectra of the products obtained in the embodiments and comparative examples are shown below;

[0036] Figure 3 The rate performance test results of the products obtained for the embodiments and comparative examples;

[0037] Figure 4 The high temperature cycle test results of the products are obtained for the embodiments and comparative examples. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0039] Compared with lithium iron phosphate, lithium iron manganese phosphate has better low-temperature performance, a higher voltage platform (4.1V), and theoretically, the energy density of lithium iron manganese phosphate is 15%-20% higher than that of lithium iron phosphate, so lithium iron manganese phosphate is expected to become the next generation of lithium iron phosphate alternative cathode material. Due to the similar structure of lithium iron manganese phosphate and lithium iron phosphate, waste lithium iron phosphate can be converted into lithium iron manganese phosphate, and after long-term circulation and acid leaching and other pretreatment, the particles of waste lithium iron phosphate will have microcracks, which provide more sites for its combination with manganese elements.

[0040] The embodiment of the present invention provides a method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate, and prepares lithium iron manganese phosphate positive electrode material by co-acid leaching method combined with two-step sintering process. Figure 1 As shown, the steps are as follows:

[0041] S1. Prepare materials

[0042] Waste lithium iron phosphate powder and waste lithium iron manganese phosphate powder are separated from waste batteries, and the specific separation method is not limited.

[0043] In some embodiments, after the waste batteries are discharged, the positive electrode sheets are separated and the positive electrode sheets can be crushed and sieved to obtain waste lithium iron phosphate powder and waste lithium manganese iron phosphate powder with small particle sizes.

[0044] In some embodiments, the separated waste lithium iron phosphate powder and waste lithium iron manganese acid powder can be fully ball-milled for standby use. The ball-milling method is not limited, and can be wet ball-milling, or the powder can be directly solid-phase ball-milled, but is not limited thereto.

[0045] S2, oxidative acid leaching

[0046] After mixing and ball-milling the waste lithium iron phosphate powder and the waste lithium iron manganese phosphate powder, acid leaching is carried out in a mixed acid solution containing an oxidant and an organic acid, and a black solid material and an acid leaching solution are obtained after solid-liquid separation. In the mixed acid solution containing an oxidant and an organic acid, lithium is leached out and enters the acid leaching solution. The solid material containing iron and manganese can be used as an iron source and a manganese source.

[0047] In a preferred embodiment, the solid material is dried to obtain iron phosphate powder (FP) and manganese phosphate powder (MP) after oxidation leaching, which can be used as iron source and manganese source. Impurities such as solvents remaining on the surface of the solid material can be removed by drying.

[0048] In some embodiments, the oxidant in the mixed acid solution is selected from at least one of saturated hydrogen peroxide and hypochlorous acid solution, and the oxidant can be any one or more of the above; the organic acid in the mixed acid solution is selected from at least one of acetic acid, acetic acid, propionic acid, tartaric acid, oxalic acid, malic acid, citric acid and ascorbic acid, and the organic acid can be any one or more of the above.

[0049] Furthermore, the volume fraction of the oxidant in the mixed acid solution is 1%-20%, and the concentration of the organic acid in the mixed acid solution is 0.1mol / L-4mol / L. By adjusting the concentrations of the oxidant and the organic acid, lithium can be leached more fully, iron and manganese can be retained in the solid material, and the utilization rate of raw materials can be improved. Specifically, the volume fraction of the oxidant in the mixed acid solution can be 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, etc.; the concentration of the organic acid in the mixed acid solution can be 0.1mol / L, 0.5mol / L, 1.0mol / L, 2.0mol / L, 3.0mol / L, 4.0mol / L, etc.

[0050] In some embodiments, by adjusting the amount of mixed acid solution, the material-liquid ratio is 5g / L-25g / L, the acid leaching temperature is 20℃-60℃, and the acid leaching time is 10min-40min. By adjusting the material-liquid ratio, acid leaching temperature and time, lithium can be leached more fully. Specifically, the material-liquid ratio refers to the ratio of the total amount of waste lithium iron phosphate powder and waste lithium manganese iron phosphate powder to the amount of mixed acid solution. The material-liquid ratio is 5g / L-25g / L, that is, 1L of mixed acid solution corresponds to a total mass of two waste powders of 5g-25g. For example, the material-liquid ratio can be 5g / L, 10g / L, 15g / L, 20g / L, 25g / L, etc. The acid leaching temperature can be 20℃, 30℃, 40℃, 50℃, 60℃, etc., and the acid leaching time can be 10min, 20min, 30min, 40min, etc.

[0051] In some embodiments, water washing is performed after acid leaching, and then solid-liquid separation is performed. The washing can be performed with deionized water to prevent lithium ions from adhering to the solid material.

[0052] S3. Alkalization

[0053] The acid leaching solution is alkalized and lithium carbonate is obtained after solid-liquid separation. The lithium carbonate is used as a lithium source to recover the lithium element.

[0054] In some embodiments, the process of alkalizing the acid leaching solution includes: introducing carbon dioxide or adding sodium carbonate into the acid leaching solution, and performing solid-liquid separation after no solid is deposited. After introducing carbon dioxide or adding sodium carbonate, lithium in the acid leaching solution is deposited, and the obtained white solid is Li 2 CO 3 , which can be used as a lithium source. When no solid is produced in the system, stop adding carbon dioxide or sodium carbonate. Sodium carbonate can be added in the form of an aqueous solution or directly added as a solid. The method of solid-liquid separation is not limited and can be general suction filtration.

[0055] S4, Sintering

[0056] Lithium iron manganese phosphate is prepared using iron source, manganese source and lithium source as raw materials, so as to realize the recovery of valuable metals iron, manganese and lithium in waste lithium iron phosphate powder and waste lithium iron manganese phosphate powder.

[0057] In some embodiments, the iron source, manganese source, lithium source and carbon source are mixed and sintered once, and the sintered material obtained by the first sintering is ball-milled and then sintered twice. Adding a ball milling process between the two sinterings makes the distribution of each element more uniform and the contact more complete, which is conducive to improving its crystal structure after high-temperature sintering, and obtains a structurally reconstructed and modified carbon-coated LMFP material. The method provided in the embodiment of the present invention not only efficiently and greenly recycles waste iron lithium without pollution, avoids the large-scale use of chemicals that pollute the environment, but also obtains a lithium manganese iron phosphate battery with a long cycle life and high energy density.

[0058] In some embodiments, by regulating the amount of iron source, manganese source, lithium source and carbon source, the molar ratio of Fe, Mn, Li and organic carbon in the raw material is 1: (0.8-1.2): (1.8-2.2): (1.0-1.5), such as 1: 0.8: 1.8: 1.0, 1: 1.0: 2.0: 1.02, 1: 1.2: 2.2: 1.5, etc. The amount of iron source, manganese source, lithium source and carbon source is preferably within the above range to regulate the carbon coating amount and the molar ratio of each element to further improve the electrochemical performance of lithium manganese iron phosphate. When the ratio of iron source, manganese source and lithium source obtained in S2 and S3 does not meet the above requirements, additional additions may be made.

[0059] Furthermore, the organic carbon is selected from at least one of glucose, sucrose and polyethylene glycol, and the organic carbon may be any one or more of the above.

[0060] In some embodiments, the sintering temperature of the first sintering is 450°C-550°C, and the sintering time is 3h-10h; the sintering temperature of the second sintering is 600°C-700°C, and the sintering time is 5h-15h. By optimizing the temperature and time of the two sinterings, the electrochemical performance of the sintered lithium manganese iron phosphate is further improved.

[0061] Specifically, the sintering temperature of the first sintering can be 450°C, 480°C, 500°C, 530°C, 550°C, etc., and the first sintering time can be 3h, 5h, 8h, 10h, etc.; the sintering temperature of the second sintering can be 600°C, 650°C, 700°C, etc., and the second sintering time can be 5h, 8h, 10h, 12h, 15h, etc.

[0062] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0063] It should be noted that the preparation process of the waste lithium iron phosphate powder and waste lithium iron manganese phosphate powder used in the following examples and comparative examples is as follows:

[0064] Waste lithium iron phosphate powder: Take the retired lithium iron phosphate battery of Lanjun New Energy Technology Co., Ltd. with a model of 314Ah, and the positive electrode material is lithium iron phosphate.

[0065] Waste lithium iron manganese phosphate powder: Take the retired lithium iron manganese phosphate battery of Lanjun New Energy Technology Co., Ltd. with a model of 72Ah, and the positive electrode material is lithium iron manganese phosphate.

[0066] Example 1

[0067] This embodiment provides a method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate, the steps are as follows:

[0068] 200g of waste lithium iron phosphate powder and 200g of waste lithium iron manganese phosphate powder were mixed with a hydrogen peroxide-acetic acid composite solution, the volume fraction of saturated hydrogen peroxide in the composite solution was 10vol%, the concentration of acetic acid was 2mol / L, the solid-liquid ratio was 10g / L, the reaction temperature was 50°C, the oxidation time was 30min, and then washed with deionized water 3 times, solid-liquid separation was performed to obtain a black solid and a filtrate, and the black solid was dried to obtain leached iron phosphate powder (FP) and leached manganese phosphate powder (MP) after oxidation leaching, which were used as iron source and manganese source. CO was introduced into the filtrate. 2 When no solid is produced, stop adding and filter to obtain a white solid, namely Li 2 CO 3 , as a lithium source, and element recovery was tested using ICP.

[0069] The iron source, manganese source, lithium source, and carbon source were fully ball-milled in a molar ratio of Fe, Mn, Li, and organic carbon of 1:1:2:1.2 (extra can be added if the ratio is insufficient), and the rotation speed was 200 rpm for 1 h. The carbon source was polyethylene glycol. They were sintered at 500°C in an argon atmosphere for 5 h, and then fully ball-milled again at a rotation speed of 200 rpm for 1 h, a rotation speed of 150 rpm for 2 h, and sintered at 600°C in an argon atmosphere for 10 h to obtain lithium iron manganese phosphate material. A 5Ah lithium iron manganese phosphate soft-pack battery was prepared, and its rate performance and high-temperature cycle performance were tested.

[0070] Example 2

[0071] This embodiment provides a method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate, the steps are as follows:

[0072] 200g of waste lithium iron phosphate powder and 250g of waste lithium iron manganese phosphate powder were mixed with a hydrogen peroxide-hypochlorous acid-acetic acid composite solution. The volume fractions of saturated hydrogen peroxide solution and hypochlorous acid solution in the composite solution were 10vol% and 5vol%, respectively. The concentration of acetic acid was 2mol / L, the solid-liquid ratio was 10g / L, the reaction temperature was 50°C, and the oxidation time was 30min. After washing with deionized water for 3 times, solid-liquid separation was performed to obtain a black solid and a filtrate. After the black solid was dried, leached iron phosphate powder (FP) and leached manganese phosphate powder (MP) after oxidation leaching were obtained as iron source and manganese source. Na was added to the filtrate. 2 CO 3 When no solid is produced, stop adding and filter to obtain a white solid, namely Li 2 CO 3 , as a lithium source, and element recovery was tested using ICP;

[0073] The iron source, manganese source, lithium source, and carbon source were fully ball-milled in a molar ratio of Fe, Mn, Li, and organic carbon of 1:1:2:1.2 (extra can be added if the ratio is insufficient), and the rotation speed was 300 rpm for 1.5 h. The carbon source was glucose. The mixture was sintered at 450 ° C in an argon atmosphere for 6 h, and then fully ball-milled again at a rotation speed of 200 rpm for 2 h. The mixture was sintered at 650 ° C in an argon atmosphere for 12 h to obtain lithium iron manganese phosphate material. A 5Ah lithium iron manganese phosphate soft-pack battery was prepared, and its rate performance and high-temperature cycle performance were tested.

[0074] Example 3

[0075] This embodiment provides a method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate, the steps are as follows:

[0076] 150g of waste lithium iron phosphate powder and 200g of waste lithium iron manganese phosphate powder were mixed with a hydrogen peroxide-acetic acid composite solution. The volume fraction of saturated hydrogen peroxide solution in the composite solution was 10vol%, the concentration of acetic acid was 1mol / L, the solid-liquid ratio was 10g / L, the reaction temperature was 50°C, the oxidation time was 30min, and then washed with deionized water 3 times. Solid-liquid separation was performed to obtain a black solid and a filtrate. After the black solid was dried, leached iron phosphate powder (FP) and leached manganese phosphate powder (MP) after oxidation leaching were obtained as iron source and manganese source. Na was added to the filtrate. 2 CO 3 When no solid is produced, stop adding and filter to obtain a white solid, namely Li 2 CO 3 , as a lithium source, and element recovery was tested using ICP.

[0077] The iron source, manganese source, lithium source, and carbon source were fully ball-milled in a molar ratio of Fe, Mn, Li, and organic carbon of 1:1:2:1.2 (additional materials can be added if the ratio is insufficient), and the rotation speed was 150 rpm for 1 hour. The carbon source was glucose. The mixture was sintered at 400°C in an argon atmosphere for 6 hours, and then fully ball-milled again at a rotation speed of 150 rpm for 0.5 hours. The mixture was sintered at 600°C in an argon atmosphere for 24 hours to obtain lithium iron manganese phosphate material. A 5Ah lithium iron manganese phosphate soft-pack battery was prepared, and its rate performance and high-temperature cycle performance were tested.

[0078] Example 4

[0079] The only difference from Example 1 is that no ball milling is performed between two sinterings.

[0080] Comparative Example 1

[0081] 200 g of waste lithium iron phosphate powder and 200 g of waste lithium iron manganese phosphate powder were mixed with a hydrogen peroxide-acetic acid composite solution, the volume fraction of the saturated hydrogen peroxide solution in the composite solution was 10 vol%, the concentration of acetic acid was 1 mol / L, the solid-liquid ratio was 10 g / L, the reaction temperature was 50 ° C, the oxidation time was 30 min, and the mixture was washed with deionized water 3 times. After filtration and drying, the waste iron phosphate powder (FP) after oxidation leaching was obtained and used as the iron source and manganese source, and the element recovery rate was tested using ICP.

[0082] The iron source, manganese source, and lithium source (Li 2 CO 3), the carbon source was fully ball-milled in a molar ratio of Fe, Mn, Li, and organic carbon of 1:1:2:1.2 (the insufficient ratio could be added additionally), the rotation speed was 150 rpm, the time was 2 h, the carbon source was glucose, and the sintering was carried out at 600 ° C in an argon atmosphere for 10 h to obtain lithium manganese iron phosphate material, and a 5Ah lithium manganese iron phosphate soft-pack battery was prepared to test its rate performance and high-temperature cycle performance.

[0083] Comparative Example 2

[0084] 200g of waste lithium iron phosphate powder and 200g of waste lithium iron manganese phosphate powder were fully ball-milled at a speed of 200rpm for 2h, and a carbon source and a lithium source were added to achieve a molar ratio of Fe, Mn, Li, and organic carbon of 1:1:2:1.2. The carbon source was glucose and the lithium source was lithium carbonate. The mixture was sintered at 700°C in an argon atmosphere for 10h to obtain lithium iron manganese phosphate material. A 5Ah lithium iron manganese phosphate soft-pack battery was prepared, and its rate performance and high-temperature cycle performance were tested.

[0085] Test Example 1

[0086] The element recovery effect, impedance, rate performance, and high temperature cycle performance of lithium manganese iron phosphate prepared by the test examples and comparative examples are shown in Table 1. Figure 2 , Figure 3 and Figure 4 shown.

[0087] ICP test method: 10 g of the obtained iron source and manganese source were dissolved in aqua regia, shaken in a 50°C water bath for 2 hours, and then tested. The results are shown in Table 1. The element recovery rate calculation method is formula 1:

[0088]

[0089] Wherein, δ is the element recovery rate, %; a is the mass ratio of iron or manganese in the recovered material, wt%; c is the ICP test result, mol / L; v is the total volume of the solution during the ICP test, L.

[0090] Table 1 Recovery effect of metal elements in different recovery schemes

[0091] Recycling Program Iron recovery efficiency (%) Manganese recovery efficiency (%) Example 1 98.51 98.33 Example 2 97.22 97.10 Example 3 97.07 96.46 Example 4 98.66 97.81 Comparative Example 1 88.80 89.45 Comparative Example 2 87.55 87.06

[0092] It can be seen from Table 1 that the recovery rate of iron in the method of the embodiment is significantly higher than that in the comparative example.

[0093] Rate performance test method: After charging at 0.33C constant current to 4.3V, leave it for 10 minutes, discharge at different rates to 2.0V, record the process steps, time, and capacity. The results are as follows: Figure 3 .

[0094] High temperature cycle test method: the ambient temperature is 45℃, charge to 4.3V at 1C rate, leave for 10min, discharge to 2.0V at 1C rate, cycle until the capacity retention rate is 80%, record the process steps, time, and capacity. The results are as follows: Figure 4 .

[0095] from Figure 2 It can be seen that the battery impedance of Examples 1 and 2 is small and the lithium ion diffusion rate is fast, which shows that the material formed by fully recycling waste iron-lithium and manganese-iron-lithium batteries by the method of the present invention has a more complete lithium ion bulk diffusion capacity.

[0096] from Figure 3 and Figure 4 It can be seen that the batteries of Examples 1 and 2 have excellent rate performance and cycle performance, achieving the purpose of fully recycling iron-lithium and manganese-iron-lithium batteries.

[0097] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for co-recovering waste lithium iron phosphate and lithium iron manganese phosphate, characterized in that: include: Mixing the waste lithium iron phosphate powder and the waste lithium iron manganese phosphate powder, performing acid leaching in a mixed acid solution containing an oxidant and an organic acid, and obtaining a solid material and an acid leaching solution after solid-liquid separation; Using the solid material as an iron source and a manganese source; The acid leaching solution is subjected to alkalization treatment to obtain lithium carbonate after solid-liquid separation, and the lithium carbonate is used as a lithium source; Lithium manganese iron phosphate is prepared using the iron source, the manganese source and the lithium source as raw materials.

2. The method according to claim 1, characterized in that The oxidant in the mixed acid solution is selected from at least one of hydrogen peroxide and hypochlorous acid solution; Preferably, the volume fraction of the oxidant in the mixed acid solution is 1%-20%.

3. The method according to claim 1, characterized in that The organic acid in the mixed acid solution is selected from at least one of acetic acid, propionic acid, tartaric acid, oxalic acid, malic acid, citric acid and ascorbic acid; Preferably, the concentration of the organic acid in the mixed acid solution is 0.1 mol / L-4 mol / L.

4. The method according to claim 3, characterized in that The amount of the mixed acid solution is adjusted to make the solid-liquid ratio 5g / L-25g / L.

5. The method according to claim 4, characterized in that The acid immersion temperature is 20℃-60℃, and the acid immersion time is 10min-40min; Preferably, the acid leaching is followed by water washing and then solid-liquid separation.

6. The method according to any one of claims 1 to 5, characterized in that The solid material is dried and used as an iron source and a manganese source.

7. The method according to claim 1, characterized in that The process of alkalizing the acid leaching solution includes: introducing carbon dioxide or adding sodium carbonate into the acid leaching solution, and performing solid-liquid separation after no solid is deposited.

8. The method according to claim 1, characterized in that The iron source, the manganese source, the lithium source and the carbon source are mixed and then sintered once; the sintered material obtained by the primary sintering is ball-milled and then sintered twice; Preferably, the sintering temperature of the primary sintering is 450°C-550°C, and the sintering time is 3h-10h; Preferably, the sintering temperature of the secondary sintering is 600° C.-700° C., and the sintering time is 5 h-15 h.

9. The method according to claim 8, characterized in that By adjusting the amount of the iron source, the manganese source, the lithium source and the carbon source, the molar ratio of Fe, Mn, Li and organic carbon in the raw material is 1: (0.8-1.2): (1.8-2.2): (1.0-1.5).

10. The method according to claim 9, characterized in that The organic carbon is selected from at least one of glucose, sucrose and polyethylene glycol.

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