Method for recycling spent battery cathodes

Abstract

In the recovery method provided in this application, CO is generated by the reaction of oxalic acid and concentrated sulfuric acid. This provides an acidic atmosphere for the reaction between the cathode powder and CO, allowing some of the cathode powder (LiMeO2) to melt, transforming the solid-gas two-phase system into a solid-gas-liquid three-phase system, which is beneficial for improving the recovery rate of Li ions in LiMeO2. Furthermore, the use of CO for pre-lithiation results in a low lithium content in the solid filter material, minimizing interference from lithium ions in impurity removal and providing the possibility for subsequent efficient impurity removal. On the other hand, under acidic conditions, CO undergoes a reduction reaction with the cathode powder, reducing high-valence ions in the cathode powder to lower-valence ions, resulting in a more thorough reduction. This allows the solid filter material to dissolve in sulfuric acid, achieving efficient impurity removal. Additionally, Al is removed by adding alkali, oxidant, fluoride, and adsorbent. 3+ Fe 3+ Ca 2+ Mg 2+ F ‑ A second solution containing MeSO4 is obtained, which can be used as a precursor for preparing positive electrode active materials. It achieves efficient overall impurity removal and improves lithium recovery rate, while obtaining a high-purity MeSO4 solution.

Description

Technical Field

[0001] This application relates to the field of battery recycling technology, and in particular to a method for recycling the positive electrode of a waste battery. Background Technology

[0002] With the continuous expansion of the electric vehicle and renewable energy markets, new energy batteries, as an important energy storage device, have been widely used in automobiles, power tools, mobile devices, and other fields due to their high energy density and long lifespan. However, the recycling and disposal of used batteries remains a global challenge. Once batteries are damaged or reach the end of their lifespan, a large number of used batteries are generated, posing potential pollution and resource waste problems to the environment. Among these, batteries using ternary materials as the positive electrode active material are particularly widely used.

[0003] Traditional recycling processes mainly include pyrometallurgy and hydrometallurgy. Pyrometallurgy extracts valuable metals or compounds from cathode materials through high-temperature treatment. While the process is simple, its recovery efficiency and product quality are relatively low, and it easily generates harmful gases that pollute the environment. Hydrometallurgy, on the other hand, involves pre-treating the cathode material and then using processes such as acid leaching and extraction to enrich and recycle or utilize the valuable metals. However, this process requires large amounts of acids, alkalis, or extraction solutions. Summary of the Invention

[0004] The purpose of this application is to provide a method for recycling the positive electrode of spent batteries, so as to improve the lithium recovery rate and obtain high-purity MeSO4. The specific technical solution is as follows:

[0005] This application provides a method for recycling the positive electrode of a used battery, which includes the following steps:

[0006] (1) Obtain the positive electrode material of the waste battery, and pre-treat the positive electrode material to obtain positive electrode powder;

[0007] (2) Carbon monoxide is prepared by mixing oxalic acid and concentrated sulfuric acid and heating.

[0008] (3) The carbon monoxide obtained is passed into the positive electrode powder and heat-treated at a temperature T1 of 550°C to 700°C. Then it is washed with water and filtered to obtain solid filter material and lithium-containing filtrate.

[0009] The solid filter media comprises elemental Me and / or oxide MeO, wherein Me is selected from at least one of Ni, Co, and Mn.

[0010] (4) The solid filter material is mixed with sulfuric acid and heated to dissolve it, thereby obtaining a first solution; wherein, the first solution includes Me 2+ and impurity ions, said impurity ions including Al 3+ Fe 2+Ca 2+ and Mg 2+ The pH of the first solution is less than or equal to 2;

[0011] (5) The impurity ions in the first solution are removed to obtain a purified second solution containing MeSO4.

[0012] In some embodiments of this application, step (5) involves removing impurity ions from the first solution, including:

[0013] Step (5-a): For the Al in the impurity ions... 3+ and Fe 2+ Perform impurity removal treatment a; Step (5-b): Then, remove Ca from the impurity ions. 2+ and Mg 2+ b. Perform impurity removal treatment.

[0014] In some embodiments of this application, the impurity removal process a in step (5-a) includes:

[0015] The first solution, alkaline solution, and oxidant are mixed to obtain solution a, which is then subjected to impurity removal reaction a, followed by filtration to obtain filtrate and filter residue. The pH of solution a is 3 to 5.5; preferably, the pH of solution a is 4.5 to 5.

[0016] The impurity removal process b in step (5-b) includes:

[0017] The filtrate obtained in step (5-a) is mixed with fluoride to obtain solution b, and impurity removal reaction b is carried out. Then, an adsorbent is added to adsorb the remaining fluoride, and the solution is filtered to obtain the purified second solution containing MeSO4.

[0018] In some embodiments of this application, the impurity removal process a in step (5-a) includes: mixing the alkaline solution with the first solution to adjust the pH to 3 to 5.5 to remove the Al. 3+ Then the oxidizing agent is added to make Fe 2+ It is removed after oxidation and precipitation.

[0019] In some embodiments of this application, the impurity removal process a in step (5-a) includes: mixing the oxidant with the first solution to make Fe 2+ Oxidation is then performed, followed by the addition of the alkaline solution to adjust the pH to 3 to 5.5, so that Fe... 3+ And Al 3+ Removed after sedimentation.

[0020] In some embodiments of this application, step (5-a) satisfies at least one of the following conditions:

[0021] Condition a: The alkali in the alkaline solution is selected from at least one of NaOH, KOH, and ammonia water;

[0022] Condition b: The oxidant is selected from at least one of H2O2 and O2;

[0023] Condition c: The amount of the oxidant is: 0.01 mol to 0.1 mol of the oxidant is added for every 10 g of the positive electrode powder.

[0024] In some embodiments of this application, step (5-b) satisfies at least one of the following conditions:

[0025] Condition d: The fluoride is selected from at least one of NaF, KF, and NH4F;

[0026] Condition e: The adsorbent is selected from La2O3;

[0027] Condition f: The amount of the fluoride used is: 0.05g to 1g of the fluoride is added for every 10g of the positive electrode powder;

[0028] Condition g: The mass of the fluoride is a, and the mass of the adsorbent is b, satisfying a:b = 1:(10 to 100).

[0029] In some embodiments of this application, step (3) satisfies at least one of the following conditions:

[0030] Condition h: For every 10g of the positive electrode powder, the flow rate of carbon monoxide introduced is 1L / min to 3L / min;

[0031] Condition i: The heat treatment time t1 is 1 hour to 3 hours;

[0032] Condition j: The solid-liquid ratio of the water washing is 1:(10 to 100), and the unit of solid in the water washing is g, and the unit of liquid is ml;

[0033] Condition k: The washing process is completed when the pH of the washing solution after the water washing is 7 to 8.

[0034] In some embodiments of this application, step (3) satisfies at least one of the following conditions:

[0035] Condition 1: The positive electrode powder and oxalic acid are mixed first, and then the prepared carbon monoxide is introduced. The mass ratio of the positive electrode powder to oxalic acid is (5 to 10):1.

[0036] Condition m: In the lithium-containing filtrate, Li + The elution rate is 95%–99%.

[0037] In some embodiments of this application, in step (4), the number of moles of sulfuric acid is N1, the number of moles of the positive electrode powder is N2, and N1:N2 = (1.2 to 2.5):1.

[0038] This application also provides a positive electrode active material precursor, which is prepared by the above-described purified second solution containing MeSO4. The positive electrode active material precursor comprises Me(OH)2 and impurity elements.

[0039] The precursor of the positive electrode active material has very low content of impurity elements. The concentration of Al can reach ≤1mg / L, the concentration of Fe can reach ≤1mg / L, the concentration of Ca can reach ≤5mg / L, and the concentration of Mg can reach ≤5mg / L.

[0040] Preferably, in the positive electrode active material precursor, the concentration of Al is ≤1 mg / L, the concentration of Fe is ≤0.5 mg / L, the concentration of Ca is ≤4.5 mg / L, and the concentration of Mg can reach ≤4.5 mg / L.

[0041] This application also provides a method for preparing a precursor of a positive electrode active material, including preparation by adding an alkali.

[0042] The beneficial effects of this application are:

[0043] In the recovery method provided in this application, CO is produced by the reaction of oxalic acid and concentrated sulfuric acid. This provides an acidic atmosphere for the reaction between the cathode powder and CO, allowing some of the cathode powder (LiMeO2) to become molten, transforming the solid-gas two-phase into a solid-gas-liquid three-phase system. This is beneficial for improving the recovery rate of Li ions in LiMeO2. Specifically, the recovery rate of Li ions in the lithium-containing filtrate... + The elution recovery rate reaches approximately 95%–99%. Furthermore, by utilizing CO pre-treatment for lithium extraction, the lithium content in the solid filter media is kept low, minimizing interference from lithium ions in impurity removal and creating the possibility for subsequent efficient impurity removal.

[0044] On the other hand, under acidic conditions, CO reacts with the cathode powder in a reduction reaction, reducing high-valence ions in the cathode powder to low-valence ions. This reduction is relatively thorough, allowing the solid filter material to dissolve effectively in sulfuric acid, thus providing the possibility for subsequent efficient impurity removal. Specifically, the Li in the cathode powder is first removed... + Effective elution, then complete dissolution of the solid filter media in sulfuric acid, Li + The efficient elution process facilitates the thorough execution of subsequent impurity removal.

[0045] Furthermore, in the recovery method of this application, during the impurity removal process, the pH is first adjusted to 3-5.5 using alkali, and then combined with an oxidant to remove Al.3+ and Fe 3+ All were converted into precipitates and removed; then fluorides were used to treat Ca 2+ Mg 2+ Fluorination precipitation is performed to remove impurities; then an adsorbent is used to remove F. - After impurity removal, the resulting second solution containing MeSO4 can be used as a precursor for preparing positive electrode active materials. This is achieved through three steps: sequentially adding aluminum / iron, calcium / magnesium, and F... - After impurities are removed, the overall process is highly efficient and improves lithium recovery. At the same time, a high-purity MeSO4 solution is obtained, which is beneficial for preparing the precursor of positive electrode active material. In the second solution containing MeSO4, the concentration of Al can reach ≤1mg / L, the concentration of Fe can reach ≤1mg / L, the concentration of Ca can reach ≤5mg / L, and the concentration of Mg can reach ≤5mg / L.

[0046] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0048] Figure 1 This is an experimental flowchart of Embodiment 1 of this application. Detailed Implementation

[0049] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0050] Currently, there are several methods for recycling ternary cathode materials from spent batteries. One method involves adding carbon to the spent ternary cathode material, continuously introducing CO2 during roasting, and then carbonizing it during water leaching. This converts Li to Li₂CO₃, separating it from other elements. Other elements such as nickel, cobalt, and manganese are then separated and extracted using acid leaching followed by extraction. This process requires the addition of additional carbon source, and the subsequent separation of nickel, cobalt, and manganese consumes acid and alkali, resulting in significant resource consumption. Another method involves reducing the ternary cathode material powder by introducing one or more of carbon monoxide, nitrogen, and natural gas during roasting. After water leaching to obtain a lithium-rich solution, resin purification is performed, followed by the introduction of carbon dioxide. The remaining residue is then acid-dissolved, precipitated, and extracted for recovery. This method requires two steps for lithium extraction, and nickel, cobalt, and manganese require additional acid-alkali treatment and extraction, also resulting in high resource consumption.

[0051] This application provides a method for recycling the positive electrode of a used battery, which includes the following steps:

[0052] (1) Obtain the positive electrode material of the waste battery, and pre-treat the positive electrode material to obtain positive electrode powder;

[0053] (2) Obtain carbon monoxide or carbon powder;

[0054] (3) Mix carbon monoxide or carbon powder into the positive electrode powder, heat treat it, and then wash and filter it to obtain solid filter material and lithium-containing filtrate.

[0055] (4) The solid filter material is mixed with sulfuric acid and heated to dissolve it, thereby obtaining a first solution; wherein, the first solution includes Me 2+ And impurity ions, Me is selected from at least one of Ni, Co, and Mn elements, and impurity ions include Al 3+ Fe 2+ Ca 2+ or Mg 2+ At least one of the following, the pH of the first solution is less than or equal to 2;

[0056] (5) The impurity ions in the first solution are removed to obtain a purified second solution containing MeSO4.

[0057] In some embodiments of this application, in step (2), carbon monoxide can be obtained by mixing oxalic acid and concentrated sulfuric acid and then heating.

[0058] In some embodiments of this application, the temperature of the heat treatment in step (3) can be from 550°C to 700°C.

[0059] In some embodiments of this application, in step (3), the solid filter media includes elemental Me and / or oxide MeO, wherein Me is selected from at least one of Ni, Co and Mn.

[0060] This application provides a method for recycling the positive electrode of a used battery, which includes the following steps:

[0061] (1) Obtain the positive electrode material of the waste battery, and pre-treat the positive electrode material to obtain positive electrode powder;

[0062] (2) Carbon monoxide is prepared by mixing oxalic acid and concentrated sulfuric acid and heating.

[0063] (3) The carbon monoxide obtained is passed into the positive electrode powder and heat-treated at a temperature T1 of 550°C to 700°C. Then it is washed with water and filtered to obtain solid filter material and lithium-containing filtrate.

[0064] Solid filter media include elemental Me and / or oxide MeO, wherein Me is selected from at least one of Ni, Co, and Mn elements;

[0065] (4) The solid filter material is mixed with sulfuric acid and heated to dissolve it, thereby obtaining a first solution; wherein, the first solution includes Me 2+ and impurity ions, including Al 3+ Fe 2+ Ca 2+ and Mg 2+ The pH of the first solution is less than or equal to 2;

[0066] (5) The impurity ions in the first solution are removed to obtain a purified second solution containing MeSO4.

[0067] In this application, the positive electrode can refer to a positive electrode whose positive electrode active material is mainly LiMeO2, wherein Me is selected from at least one of the elements Ni, Co, and Mn, or other suitable positive electrode active materials.

[0068] The recovery method provided in this application prepares CO using a combination of oxalic acid and concentrated sulfuric acid. The resulting CO is used to remove carbon from the cathode powder. Specifically, CO reacts with LiMeO2 to generate CO2, which then reacts with C in the cathode powder to produce CO. This CO2 continues to react with the cathode powder, removing carbon and reducing nickel, cobalt, and manganese. After washing and filtration, nickel, cobalt, manganese, and lithium in the cathode powder are separated, resulting in a solid filter media that is essentially carbon-free. The resulting solid filter media, containing nickel, cobalt, and manganese metals (Me) and their oxides (MeO), is then dissolved and purified using sulfuric acid.

[0069] Specifically, CO is prepared by combining oxalic acid and concentrated sulfuric acid. CO reacts with LiMeO2 to generate CO2. The CO2 obtained from the above reaction continues to react with C in the cathode powder to generate CO, and thus CO continues to react with LiMeO2 in the cathode powder. Steps (2) and (3) remove carbon from the cathode powder and simultaneously convert lithium in LiMeO2 into Li2CO3. After washing with water, it enters the lithium-containing filtrate, thereby realizing the recovery of lithium. LiMeO2 is also reduced to make Me exist in the solid form of elemental Me and / or oxide MeO. After washing with water, elemental Me and / or oxide MeO enter the solid filter material. Filtration separates the lithium-containing filtrate and the solid filter material. Most of the lithium exists in the lithium-containing filtrate in ionic form. The solid filter material basically does not contain carbon and lithium, so the lithium elution recovery rate is high, and the interference of lithium ions on the subsequent solid filter material impurity removal process is minimized. Then, the solid filter media containing elemental Me and / or oxide MeO generated by reduction is dissolved by heating with sulfuric acid. When the pH of the first solution is less than or equal to 2, it indicates that enough sulfuric acid has been added to the first solution to dissolve the elemental Me and / or oxide MeO in the solid filter media, resulting in MeSO4, such as NiSO4, CoSO4, and MnSO4. In addition, the solid filter media includes not only elemental Me and / or oxide MeO, but also compounds containing impurity elements, such as oxides or carbonates containing impurity elements. In step (4), these compounds react with sulfuric acid to generate corresponding sulfates. The impurity elements include aluminum, iron, calcium, and magnesium. The resulting sulfates include aluminum sulfate, ferric sulfate, calcium sulfate, and magnesium sulfate. Aluminum sulfate, ferric sulfate, and magnesium sulfate are readily soluble in water, while calcium sulfate is not completely soluble in water. The content of each impurity element is relatively low, thus the first solution contains impurity ions Al. 3+ Fe 2+ Mg 2 and Ca 2+ After further impurity removal, a purified second solution containing MeSO4 can be obtained.

[0070] In addition, the CO produced by the reaction of oxalic acid and concentrated sulfuric acid provides an acidic atmosphere for step (3), allowing some LiMeO2 to become molten, transforming the solid-gas two-phase into a solid-gas-liquid three-phase system. This is beneficial for improving the recovery rate of Li ions in LiMeO2. Furthermore, due to the high leaching recovery rate of Li ions, the subsequent impurity removal process is relatively simple, meaning that the influence of Li ions on impurity removal is basically unnecessary. Meanwhile, in step (3), the heat treatment temperature T1 is between 550℃ and 700℃. For example, the heat treatment temperature T1 can be 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, or 700℃, or any two of the above numbers. If the heat treatment temperature is too low, the structure of LiMeO2 cannot be destroyed, the reaction is incomplete, and most of the trivalent Me ions cannot be converted into divalent Me ions. If the heat treatment temperature is too high, most of the Li will volatilize, resulting in a significant decrease in Li recovery rate and economic losses. Therefore, by controlling the heat treatment temperature T1 within the above-mentioned range, CO can react fully with LiMeO2, resulting in a higher lithium recovery rate and thus improving the economic efficiency of the recycling process.

[0071] In step (4), when the pH is less than or equal to 2, it indicates that sufficient sulfuric acid has been added to the first solution to dissolve the elemental Me and / or oxide MeO in the solid filter material, yielding MeSO4, such as NiSO4, CoSO4, and MnSO4. Simultaneously, the solid filter material also contains compounds containing impurity elements, such as oxides or carbonates. These impurity elements include aluminum, iron, calcium, and magnesium. After dissolution with sulfuric acid, sulfates are obtained, including aluminum sulfate, ferric sulfate, calcium sulfate, and magnesium sulfate. Among these, aluminum sulfate, ferric sulfate, and magnesium sulfate are readily soluble in water, while calcium sulfate is not completely soluble in water. The content of each impurity element is relatively low, thus the first solution contains impurity ions Al. 3+ Fe 2+ Mg 2 and Ca 2+ When the pH is greater than 2, the amount of sulfuric acid added to the first solution is insufficient, which may cause incomplete reaction of elemental Me and / or oxide MeO in the solid filter media. Some elemental Me and / or oxide MeO in the solid filter media dissolve in the first solution, so that some Me elements exist in ionic form and some Me elements still exist in solid form, reducing the recovery rate of MeSO4. In addition, some impurity elements may also continue to exist in the solid phase. Subsequent acid dissolution and impurity removal of the undissolved solids are required, which reduces the overall impurity removal effect.

[0072] This application does not impose any particular restrictions on the method of obtaining the positive electrode of the waste battery, as long as it can achieve the purpose of this application. For example, it can be obtained by dismantling the waste battery or by purchasing it directly.

[0073] In this application, the reaction equation for oxalic acid and concentrated sulfuric acid in step (2) is as follows:

[0074]

[0075] In this application, the heat treatment in step (3) includes the following reactions:

[0076] 2CO+2LiMeO2=Li2CO3+Me+MeO+CO2↑;

[0077] CO2 + C = 2CO↑.

[0078] In this application, the dissolution reaction in step (4) includes the following reactions:

[0079] Me + H₂SO₄ = H₂↑ + MeSO₄;

[0080] MeO + H2SO4 = H2O + MeSO4.

[0081] In some embodiments of this application, in step (2), the mass of oxalic acid is Z g, the volume of the catalyst concentrated sulfuric acid is P mL, Z:P = (5 to 50):1; the heating temperature T5 after mixing oxalic acid and concentrated sulfuric acid is 150°C to 250°C.

[0082] In some embodiments of this application, in step (3), the flow rate V of carbon monoxide introduced per 10g of cathode powder is 1L / min to 3L / min. For example, the flow rate V of carbon monoxide can be 1L / min, 1.2L / min, 1.4L / min, 1.5L / min, 1.6L / min, 1.8L / min, 2L / min, 2.2L / min, 2.4L / min, 2.5L / min, 2.6L / min, 2.8L / min, or 3L / min, or any two of the above values. By adjusting the flow rate V of carbon monoxide within the above range, on the one hand, CO reacts fully with LiMeO2, which is beneficial for separating lithium elements during the subsequent water washing process; on the other hand, residual carbon in the cathode powder can be removed. The resulting solid filter material is essentially free of lithium elements and carbon, which is beneficial for improving the recovery rate of Me elements.

[0083] In some embodiments of this application, the heat treatment time t1 in step (3) is 1 to 3 hours. For example, the heat treatment time t1 can be 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3 hours, or any two of the above values. By adjusting the heat treatment time t1 within the above range, CO can fully react with LiMeO2, converting trivalent Me ions into divalent Me ions, which is beneficial to improving the recovery rate of Me element; moreover, lithium element is not easily volatilized, and the recovery rate of lithium element is relatively high when recovering lithium element through lithium-containing filtrate in the subsequent process. Thus, the economic benefits of the recovery process can be improved.

[0084] In some embodiments of this application, in step (3), the solid-liquid ratio X of the water washing is 1:(10 to 100), where the unit of solid in the water washing is g and the unit of liquid is ml. For example, the solid-liquid ratio X can be 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, or 1:100, or any two of the above numbers. By adjusting the solid-liquid ratio X of the water washing within the above range, the recovery rate of lithium ions can be improved.

[0085] In some embodiments of this application, in step (3), the washing is completed when the pH of the washing solution after multiple washes is 7 to 8. For example, the pH of the washing solution can be 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, or 8, or any two of the above numbers. If the pH of the washing solution after washing is within the above range, it indicates that the lithium element is basically cleaned. Therefore, by controlling the pH of the washing solution within the above range, effective separation of lithium and Me elements can be achieved.

[0086] In some embodiments of this application, in step (3), the solid-liquid ratio X of the water washing is 1:(10 to 100), and the pH of the washing solution after water washing is 7 to 8, at which point the water washing is completed. By adjusting the solid-liquid ratio X of the water washing and the pH of the washing solution after water washing within the above ranges, effective separation of lithium and Me elements can be achieved.

[0087] In some embodiments of this application, in step (3), the cathode powder and oxalic acid can be mixed first, and then the prepared carbon monoxide can be introduced. The mass ratio Y of the cathode powder to oxalic acid is (5 to 10):1. For example, the mass ratio Y can be 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, or any two of the above numbers. Mixing the cathode powder and oxalic acid can produce CO, CO2 and H2O. First, the generated CO is conducive to a more complete reaction between the cathode powder and CO. Second, the generated CO2 continues to react with C in the cathode powder to generate more CO, which is more conducive to a complete reaction between the cathode powder and CO. Third, the generated H2O can adjust the reaction atmosphere, which is conducive to the reaction between the cathode powder and CO in a solid-gas-liquid three-phase state. Furthermore, the early addition of oxalic acid ensures a sufficient CO supply and the presence of H2O to adjust the atmosphere, which facilitates the reaction between CO and the cathode powder, shortens the reaction time, and particularly improves the elution recovery rate of Li ions (to 95%-99%), thus reducing the interference of lithium ions on impurity removal. By controlling the mass ratio Y of cathode powder to oxalic acid within the above range, it is beneficial for the cathode powder to react fully with CO, thereby improving the recovery rates of nickel, cobalt, and lithium.

[0088] In some embodiments of this application, in step (3), the lithium-containing filtrate contains Li + The elution rate is 95%–99%. For example, Li + The elution rate can be 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, or 99%, or any two of the above figures. Because Li + The elution rate is relatively high, and the lithium content in the solid filter material is low, which reduces the interference of lithium ions on impurity removal and provides the possibility for subsequent efficient impurity removal.

[0089] In some embodiments of this application, in step (4), the temperature T2 of the dissolution reaction is 50°C to 80°C, and the time t2 is 0.5h to 2h. For example, the temperature T2 of the dissolution reaction can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, or any two of the above numbers. For example, the time t2 of the dissolution reaction can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, or 2h, or any two of the above numbers. By controlling the temperature T2 and time t2 of the dissolution reaction within the above ranges, it is beneficial for the positive electrode powder to dissolve sufficiently to obtain the first solution.

[0090] In some embodiments of this application, in step (4), the sulfuric acid is commercially available concentrated sulfuric acid.

[0091] In some embodiments of this application, in step (4), the molar number of sulfuric acid is N1, and the molar number of positive electrode powder is N2, satisfying N1:N2 = (1.2 to 2.5):1. In this application, the molar number N2 of the positive electrode powder is denoted by the sum of the molar numbers of lithium elements in the positive electrode powder. For example, the molar ratio of sulfuric acid to positive electrode powder N1:N2 can be 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, or 2.5:1, or between any two of the above ratios. The solid filter media includes elemental Me and / or oxide MeO, where Me is selected from at least one of Ni, Co, and Mn elements. By adjusting the molar ratio of sulfuric acid to positive electrode powder N1:N2 within the above range, excess sulfuric acid is added to ensure the complete dissolution reaction in step (4). The excess sulfuric acid dissolves the elemental Me and / or oxide MeO in the solid filter media, and the Me element exists in the solution in ionic form, resulting in a first solution containing MeSO4, such as NiSO4, CoSO4, or MnSO4. Simultaneously, the solid filter media also includes compounds containing impurity elements, such as oxides or carbonates containing impurity elements. These impurity elements include aluminum, iron, calcium, and magnesium. After dissolution with sulfuric acid, sulfates are obtained, including aluminum sulfate, ferric sulfate, calcium sulfate, and magnesium sulfate. Among these, aluminum sulfate, ferric sulfate, and magnesium sulfate are readily soluble in water, while calcium sulfate is not completely soluble in water. The content of each impurity element is relatively low, thus the first solution contains impurity ions Al. 3+ Fe 2+ Mg 2 and Ca 2+ This is beneficial for efficient impurity removal in the subsequent process.

[0092] In some embodiments of this application, step (5) involves removing impurity ions from the first solution, including: step (5-a): removing Al ions from the impurity ions. 3+ and Fe 2+ Perform impurity removal treatment a; Step (5-b): Then remove Ca from the impurity ions. 2+ and Mg 2+ Perform impurity removal treatment b. The dissolution process in step (4) causes the impurity elements in the solid filter material to exist in the first solution in ionic form. By adding an alkaline solution, the Al in the first solution is removed. 3+ The formation of Al(OH)3 precipitate and sufficient oxidant cause Fe in the first solution to... 2+ After complete oxidation, it becomes Fe. 3+ Fe 3+ With OH in the solution - The reaction produces Fe(OH)3 precipitate, which is then removed by filtration to remove impurity ions (Al). 3+ and Fe2+ By adding a fluorinating agent, the Ca in the solution... 2+ and Mg 2+ Calcium fluoride and magnesium fluoride precipitates are formed, and impurity ions Ca are removed by filtration. 2+ and Mg 2+ The remaining fluorinating agent is adsorbed by adding an adsorbent, and the mixture is filtered to obtain a purified second solution containing nickel-cobalt-manganese sulfate. In this process, the order of impurity removal is controlled, i.e., Al is removed first. 3+ and Fe 2+ , then remove Ca 2+ and Mg 2+ Finally, removing residual fluorinating agent facilitates the efficient removal of impurity elements.

[0093] In some embodiments of this application, there are no particular restrictions on the temperature of the impurity removal process in step (5), as long as the purpose of this application can be achieved. For example, the temperature of the impurity removal process can be room temperature.

[0094] In some embodiments of this application, the impurity removal process a in step (5-a) includes: mixing a first solution, an alkaline solution, and an oxidant to obtain solution a, performing an impurity removal reaction a, and then filtering to obtain filtrate and filter residue. In some embodiments of this application, in step (5), the pH of solution a is 3 to 5.5, preferably 4.5 to 5. For example, the pH of solution a can be 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, or 5.5, or between any two of the above numbers. By adding an alkaline solution, the pH of solution a is adjusted to be within the above range, so that Al 3+ Al(OH)3 precipitate is formed, and an oxidizing agent is added to make Fe... 2+ Oxidation forms Fe(OH)3 precipitate in solution a, which is then filtered to complete the removal of aluminum / iron ions.

[0095] In some embodiments of this application, the impurity removal process a in step (5-a) includes: mixing the alkaline solution with the first solution to make its pH between 3 and 5.5, indicating that solution a contains sufficient OH-. - Make Al 3+ Al(OH)3 precipitate is formed to remove Al 3+ Then an oxidizing agent is added to make Fe 2+ It is oxidized to Fe 3+ Afterwards, solution a contains sufficient OH- - Fe 3+ With OH - The reaction produces Fe(OH)3 precipitate, which is removed by filtration.2+ .

[0096] In some embodiments of this application, the impurity removal process a in step (5-a) includes: the impurity removal process a includes: mixing the oxidant with the first solution, so that Fe 2+ Oxidation was performed, followed by the addition of an alkaline solution to adjust the pH to 3 to 5.5, indicating that solution a contained sufficient OH-. - Make Al 3+ Al(OH)3 precipitate is formed, and then sufficient oxidant is added to make Fe... 2+ Completely oxidized to Fe 3+ After that, Fe 3+ with a sufficient amount of OH in solution a - The reaction produces Fe(OH)3 precipitate, which is then removed by filtration to remove impurity ions Fe. 2+ And Al 3+ .

[0097] In some embodiments of this application, in step (5-a), the alkali in the alkaline solution is selected from at least one of NaOH, KOH, and ammonia water. When the alkali in the alkaline solution is selected from at least one of the above compounds, OH- is provided in solution a. - This makes the impurity ions Al 3+ Al(OH)3 precipitate and Fe are formed. 2+ It is oxidized to Fe 3+ The reaction then produces Fe(OH)3 precipitate in solution a, which can be removed by filtration to remove impurity ions Al. 3+ and Fe 2+ Meanwhile, the introduction of small amounts of sodium and potassium elements does not affect the subsequent preparation of positive electrode active material precursors using the purified MeSO4-containing second solution.

[0098] In some embodiments of this application, in step (5-a), the oxidant is selected from at least one of H2O2 and O2. When the oxidant is selected from at least one of the above compounds, no other impurity ions are introduced, while efficiently removing Fe... 2+ Complete oxidation to Fe 3+ This causes Fe(OH)3 precipitate to form in solution a, and the Fe ions are removed by filtration.

[0099] In some embodiments of this application, in step (5-a), the amount of oxidant used is: 0.01 mol to 0.1 mol of oxidant is added per 10 g of positive electrode powder. For example, the amount of oxidant added per 10 g of positive electrode powder can be 0.01 mol, 0.02 mol, 0.03 mol, 0.04 mol, 0.05 mol, 0.06 mol, 0.07 mol, 0.08 mol, 0.09 mol, or 0.1 mol, or any two of the above figures. By controlling the amount of added oxidant within the above range, the Fe in the solid filter material is reduced. 2+ Complete oxidation to Fe 3+ After that, Fe 3+ with a sufficient amount of OH in solution a - The reaction produces Fe(OH)3 precipitate, which is then filtered to remove the Fe ions.

[0100] In some embodiments of this application, the impurity removal process b in step (5-b) includes: mixing the filtrate obtained in step (5-a) with fluoride to obtain solution b, performing the impurity removal reaction b, then adding an adsorbent to adsorb the remaining fluoride, and filtering to obtain a purified second solution containing MeSO4. By adding fluoride, the Ca in solution b is reduced... 2+ and Mg 2+ It can form a precipitate that is sparingly soluble in water, and filter out impurity ions such as Ca. 2+ and Mg 2+ Meanwhile, the remaining fluoride is adsorbed by an adsorbent, and after filtration, a purified second solution containing MeSO4 is obtained.

[0101] In some embodiments of this application, in step (5-b), the fluoride is selected from at least one of NaF, KF, and NH4F. The fluoride is selected from at least one of the above compounds, which makes the impurity ion Ca... 2+ and Mg 2+ Calcium fluoride and magnesium fluoride precipitates are formed, and impurity ions Ca are removed by filtration. 2+ and Mg 2+ .

[0102] In some embodiments of this application, in step (5-b), the amount of fluoride used is: 0.05g to 1g of fluoride is added per 10g of positive electrode powder. For example, the mass of fluoride added per 10g of positive electrode powder can be 0.05g, 0.1g, 0.15g, 0.2g, 0.25g, 0.3g, 0.35g, 0.4g, 0.45g, 0.5g, 0.55g, 0.6g, 0.65g, 0.7g, 0.75g, 0.8g, 0.85g, 0.9g, 0.95g, or 1g, or any two of the above figures. By controlling the mass of the added fluoride within the above range, the impurity ion Ca...2+ and Mg 2+ The reaction was complete, and the impurity ion Ca... 2+ and Mg 2+ Calcium fluoride and magnesium fluoride precipitates are formed; after filtration, impurity ions Ca are removed. 2+ and Mg 2+ .

[0103] In some embodiments of this application, in step (5-b), the adsorbent is selected from La2O3.

[0104] In some embodiments of this application, in step (5-b), the mass of fluoride is a, and the mass of adsorbent is b, satisfying a:b = 1:(10 to 100). For example, the mass ratio of fluoride to adsorbent a:b can be 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, or 1:100, or any two of the above ratios. By adjusting the mass ratio of fluoride to adsorbent within the above range, the adsorbent can completely adsorb the remaining fluoride, forming a precipitate, reducing the risk of introducing impurities into solution b, and obtaining a purified second solution containing MeSO4.

[0105] In some embodiments of this application, in step (1), the pretreatment includes crushing, screening, and high-temperature treatment. The temperature T4 of the high-temperature treatment is 300°C to 800°C, the time t4 is 0.1h to 10h, and the atmosphere is selected from air or oxygen. For example, the temperature T4 of the high-temperature treatment can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C, or any two of the above numbers. For example, the time t4 of the high-temperature treatment can be 0.1h, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h, or any two of the above numbers. The positive current collector and positive electrode material layer of the disassembled positive electrode are separated. The positive electrode material layer is then crushed and sieved to prepare positive electrode material layer powder within a certain particle size range. Subsequently, the positive electrode material layer powder is subjected to high-temperature treatment to remove the conductive agent and binder, thereby obtaining the positive electrode powder. This application does not have any particular limitation on the particle size of the positive electrode material layer powder, as long as it can achieve the purpose of this application.

[0106] In some embodiments of this application, the waste battery is one or more of waste ternary nickel-cobalt-manganese batteries or waste lithium cobalt oxide batteries.

[0107] This application also provides a positive electrode active material precursor, which is prepared by purifying a second solution containing MeSO4. The second solution is the same as the second solution described in the recovery method provided in this application. The positive electrode active material precursor includes Me(OH)2. By adding an alkali to the second solution to make the pH alkaline, Me(OH)2 precipitate can be formed. The precipitate can then be obtained by filtration. In some embodiments of this application, the alkali added to the second solution can be at least one of NaOH, KOH, and ammonia water.

[0108] The positive electrode active material precursor Me(OH)2 prepared by this process has a very low content of impurity elements and a high recovery rate of Me(OH)2.

[0109] Example

[0110] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0111] Test methods and equipment:

[0112] Concentration test of impurity elements:

[0113] The concentrations of impurity elements Al, Fe, Ca, and Mg in the second solution after impurity removal were determined by ICP, and the units were mg / L.

[0114] Calculation of elution recovery rate:

[0115] The Li content in the cathode powder and the Li content in the washed solid filter media were determined by ICP. The Li elution recovery rate was calculated as (1 - Li content in the washed solid filter media / Li content in the cathode powder) × 100%.

[0116] Preparation of positive electrode powder:

[0117] Used ternary 811 lithium-ion batteries (LiNi) 0.8 Co 0.1 Mn 0.1 The O2) is disassembled, and the resulting positive electrode material layer is crushed and sieved to obtain positive electrode material layer powder. The positive electrode material layer powder is pretreated in a rotary kiln at T4 = 550℃ by introducing air to remove residual conductive agent and binder. The pretreatment time is t4 = 2h. Then, it is passed through a 150-mesh sieve to obtain positive electrode powder. The mass percentage of lithium in the positive electrode powder is 7.2%.

[0118] Unless otherwise specified, the following examples and comparative examples all use the positive electrode powder prepared as described above.

[0119] Example 1

[0120] Figure 1 The experimental flowchart for Example 1 is shown below, with the specific steps as follows:

[0121] 10g of positive electrode powder was used for reduction. The positive electrode powder was placed in a quartz boat and then placed in a tube furnace. 100g of oxalic acid was added to a flask, and 5ml of concentrated sulfuric acid was added dropwise to the flask before heating. Before entering the tube furnace, anti-backflow devices, sodium hydroxide solution bottles, and concentrated sulfuric acid bottles were set up to absorb CO2 and water. The temperature was set to T5 = 150℃ for CO preparation. The temperature of the tube furnace was set to T1 = 700℃. When the temperature reached T1, CO was introduced at a flow rate V = 2L / min for a duration of t1 = 90min (1.5h). After cooling, the calcined material was removed and washed with water at a solid-liquid ratio of 1:50, using 500ml of water for 1 hour. After each wash, the material was filtered, and then washed again with water at a solid-liquid ratio of 1:50. After three washes, the pH of the washing solution was measured. Washing was completed when the pH reached 7, yielding a solid filter material containing Me and MeO (Ni, Co, NiO, CoO, MnO). The elution recovery rate of Li was 98.75%. In the initial 10g of cathode powder, the total mass m0 of nickel, cobalt, and manganese was approximately 5.8g (the nickel, cobalt, and manganese content in 811 lithium-ion battery cathode powder is approximately 58wt%). The lithium elution rate of 98.75% indicates that the cathode material structure was thoroughly deciphered, and that most of the metallic Me was reduced, facilitating subsequent dissolution reactions.

[0122] The solid filter material was acid-dissolved. 6.1g of solid filter material was dissolved in 20mL of water and 50mL of 4.8mol / L sulfuric acid. The molar amount of sulfuric acid N1 was 0.24mol, and the molar amount of positive electrode powder N2 was about 0.1mol. The ratio of N1 to N2 was 2.4:1. The acid dissolution temperature was controlled at T2 = 70℃. The mixture was stirred and dissolved for 2h to obtain the first solution. The pH of the first solution was less than 0.

[0123] At room temperature, the first solution is filtered and then impurities are removed (the impurity ions in the solution are Al). 3+ Fe 2+ Ca 2+ Mg 2+ Al was removed by adjusting the pH and adding H2O2. 3+ and Fe 2+Specifically, first, add 4g NaOH and 100mL water to prepare a 1mol / L alkaline solution. Add 100mL of alkaline solution to the first solution to adjust the pH to around 4.5. Al ions will begin to precipitate. After filtration, add 3mL of H2O2 (concentration of 30wt%, molar concentration of 9.79mol / L), that is, add 0.029mol of H2O2 for every 10g of positive electrode powder. 2+ Ions transform into Fe 3+ Fe 3+ Precipitation also begins at a pH of around 4.5. Excess NaF is added to the filtrate after filtration to precipitate Ca. 2+ and Mg 2+ The mass a of NaF was 0.4 g, meaning 0.4 g of NaF was added for every 10 g of cathode powder. After filtration, excess NaF was removed using La2O3 with a mass b of 5 g (a:b = 1:12.5). After further filtration, a relatively pure second solution containing NiSO4, CoSO4, and MnSO4 was obtained. The concentrations of Al, Fe, Ca, and Mg were 0.82 mg / L, 0.30 mg / L, 3.47 mg / L, and 4.26 mg / L, respectively. The concentrations of each impurity element before and after impurity removal are shown in Table 2.

[0124] Table 1

[0125]

[0126] Note: The “content of each element in the washed solid filter media in mg / kg” in Table 1 refers to how many mg of that element are contained in 1 kg of solid filter media.

[0127] Table 2

[0128] impurity elements The concentration of impurity elements in the first solution after acid dissolution (mg / L) The concentration of impurity elements in the second solution after impurity removal treatment (mg / L) Al 19.09 0.82 Fe 1.34 0.30 Ca 97.77 3.47 Mg 32.41 4.26

[0129] Example 2

[0130] 10g of positive electrode powder was used for reduction. The positive electrode powder and solid oxalic acid were mixed together and placed in a quartz boat, which was then placed in a tube furnace. The mass ratio of positive electrode powder to oxalic acid, Y, was 10:1. 100g of oxalic acid was added to a flask, and 5ml of concentrated sulfuric acid was added dropwise before heating. Before entering the tube furnace, anti-backflow devices, sodium hydroxide solution bottles, and concentrated sulfuric acid bottles were used to absorb CO2 and water. The temperature was set to T5 = 150℃ for CO preparation. The temperature of the tube furnace was set to T1 = 700℃, and the process began when the temperature reached T1. CO was introduced at a flow rate of V = 2.5 L / min for a duration of t1 = 90 min. After cooling, the calcined material was removed and washed with water at a solid-liquid ratio of 1:50, using 500 ml of water for 1 hour. After each wash, the material was filtered, and then washed again with water at a solid-liquid ratio of 1:50. After three washes, the pH of the washing solution was measured. The washing was completed when the pH reached 7, yielding solid filter media. The elution recovery rate of Li was 98.9%. The total mass m0 of nickel, cobalt, and manganese in 10 g of cathode powder was approximately 5.8 g.

[0131] 6.2g of solid filter material was acid-dissolved using 20mL of water and 40mL of 4.8mol / L sulfuric acid. The molar amount of sulfuric acid, N1, was 0.192mol, and the molar amount of positive electrode powder, N2, was approximately 0.1mol. The ratio of N1 to N2 was 1.9:1. The acid dissolution temperature was controlled at T2 = 80℃. The mixture was stirred and dissolved for 2 hours to obtain the first solution, which had a pH less than 0.

[0132] At room temperature, the first solution is filtered and then impurities are removed (the impurity ions in the solution are Al). 3+ Fe 2+ Ca 2+ Mg 2+ Al was removed by adjusting the pH and adding H2O2. 3+ and Fe 2+ Specifically, first, add 4g NaOH and 100mL water to prepare a 1mol / L alkaline solution. Add 90mL of alkaline solution to the first solution to adjust the pH to around 5. Al ions will begin to precipitate. After filtration, add 2mL of H2O2 (concentration of 30wt%, molar concentration of 9.79mol / L), that is, add 0.0196mol of H2O2 for every 10g of positive electrode powder to remove Fe. 2+ Ions transform into Fe 3+ Fe 3+ Precipitation also begins at a pH of around 5. Excess NaF is added to the filtrate after filtration to precipitate Ca. 2+ and Mg 2+The mass of NaF, a, is 0.05 g, meaning 0.05 g of NaF is added for every 10 g of cathode powder. After filtration, excess NaF is removed using La₂O₃, with a mass, b, of 1 g. The ratio of a to b is 1:20. Filtration yields a relatively pure second solution containing NiSO₄, CoSO₄, and MnSO₄. The concentrations of Al, Fe, Ca, and Mg are 0.79 mg / L, 0.37 mg / L, 3.12 mg / L, and 3.94 mg / L, respectively.

[0133] Example 3

[0134] Except for the following parameters which differ from those in Example 1, all other parameters are the same as in Example 1:

[0135] The temperature of the tubular furnace is set at T1 = 550℃;

[0136] The CO flow rate is as follows: for every 10g of positive electrode powder, the carbon monoxide flow rate V = 2.5L / min; the heat treatment duration t1 = 60min;

[0137] In this embodiment, the elution recovery rate of Li was 95.2%.

[0138] Example 4

[0139] Except for the following parameters which differ from those in Example 1, all other parameters are the same as in Example 1:

[0140] The temperature of the tubular furnace is set at T1 = 600℃;

[0141] The CO flow rate is as follows: for every 10g of positive electrode powder, the flow rate of carbon monoxide introduced is V = 1L / min, and the heat treatment duration is t1 = 180min;

[0142] In this embodiment, the elution recovery rate of Li was 95.9%.

[0143] Example 5

[0144] Except for the mass ratio Y of positive electrode powder to oxalic acid being 5:1, everything else is the same as in Example 2. The mass of the positive electrode powder is 10g.

[0145] In this embodiment, the elution recovery rate of Li was 98.4%.

[0146] Example 6

[0147] Except for the following parameters which differ from those in Example 2, all other parameters are the same as in Example 2:

[0148] The CO flow rate is as follows: for every 10g of positive electrode powder, the carbon monoxide flow rate is V = 3L / min, and the heat treatment duration is t1 = 180min.

[0149] In this embodiment, the elution recovery rate of Li was 98.7%.

[0150] Example 7

[0151] Except for the following parameters which differ from those in Example 1, all other parameters are the same as in Example 1:

[0152] The solid-liquid ratio for water washing is 1:10.

[0153] In this embodiment, the elution recovery rate of Li was 96.4%.

[0154] Example 8

[0155] Except for the following parameters which differ from those in Example 1, all other parameters are the same as in Example 1:

[0156] The solid-liquid ratio for water washing is 1:100.

[0157] In this embodiment, the elution recovery rate of Li was 97.2%.

[0158] Table 3

[0159]

[0160] Comparative Example 1 (CO was introduced in a normal manner, compared with Example 1)

[0161] 10g of cathode powder was used for reduction. The cathode powder was placed in a quartz boat and then placed in a tube furnace. CO gas was continuously introduced at a flow rate of V = 2 L / min, and the tube furnace temperature was set to T1 = 700℃ for 90 min. After cooling, the cathode powder was removed and washed with water at a solid-liquid ratio of 1:50, using 500 ml of water for 1 h. After each wash, the mixture was filtered, and then washed again with water at a solid-liquid ratio of 1:50. After three washes, the pH of the solution was measured. The washing was completed when the pH reached 7, yielding solid filter media. The elution recovery rate of Li was 85%. The total mass m0 of nickel, cobalt, and manganese in 10g of cathode powder was approximately 6g.

[0162] The solid filter media was acid-dissolved using 50 ml of 4.8 mol / L sulfuric acid at a temperature of 70°C (T2). The solution was stirred for 2 hours to obtain the first solution, which had a pH less than 0.

[0163] At room temperature, impurity removal was performed using the same steps as in Example 1 to obtain a second solution.

[0164] The experiment found that the acid dissolution effect of the solid filter material was poor, and a small portion of the solids were not dissolved. This may be because the reduction of the positive electrode powder by directly introducing CO was not high, resulting in the solid filter material not being completely acid-dissolved. A small amount of impurity elements were also not acid-dissolved and entered the liquid phase. The recovery rates of Li and Me elements were low. Further acid dissolution and impurity removal of the undissolved solids are required. The overall impurity removal effect was worse than that of Example 1.

[0165] Comparative Example 2 (reduction temperature 500℃)

[0166] 10g of positive electrode powder was used for reduction. The powder was placed in a quartz boat and then placed in a tube furnace. 100g of oxalic acid was added to a flask, followed by 5ml of concentrated sulfuric acid. The furnace was heated, with anti-backflow measures in place before entering the tube furnace. A sodium hydroxide solution bottle and a concentrated sulfuric acid bottle were used to absorb CO2 and water. The furnace was heated to T5 = 150℃ to prepare CO. The tube furnace temperature was set to T1 = 500℃. When the temperature reached T1, CO was introduced at a flow rate of V = 2L / min for a duration of t1 = 90min. After cooling, the positive electrode powder was removed and washed with water at a solid-liquid ratio of 1:50 using 500ml of water for 1 hour. After each wash, the powder was filtered and washed again with water at a solid-liquid ratio of 1:50. After three washes, the pH of the solution was measured. The washing was completed when the pH reached 7, yielding a solid filter media. The elution recovery rate of Li was 30%.

[0167] The solid filter media was acid-dissolved using 50 ml of 4.8 mol / L sulfuric acid at a temperature of 70°C (T2). The solution was stirred for 2 hours to obtain the first solution, which had a pH less than 0.

[0168] The experiment revealed that most of the solids in the solid filter media could not be dissolved by acid, thus making it impossible to effectively carry out the impurity removal reaction.

[0169] Compared with Example 1, Comparative Example 2 shows that when the reduction temperature T1 is too low, the reduction of the cathode powder is incomplete, and the lithium element cannot be effectively separated from the cathode powder, resulting in a low lithium recovery rate and the inability to effectively carry out subsequent dissolution and impurity removal reactions.

[0170] Comparative Example 3 (reduction temperature 800℃)

[0171] 10g of positive electrode powder was used for reduction. The positive electrode powder was placed in a quartz boat and then placed in a tube furnace. 100g of oxalic acid was added to a flask, and 5ml of concentrated sulfuric acid was added dropwise before heating. Before entering the tube furnace, anti-backflow devices, sodium hydroxide solution bottles, and concentrated sulfuric acid bottles were used to absorb CO2 and water. The temperature was set at T5 = 150℃ to prepare CO. The temperature of the tube furnace was set at T1 = 800℃. When the temperature reached T1, CO was introduced at a flow rate V = 2L / min for a duration of t1 = 90min. After cooling, the calcined material was removed and washed with water at a solid-liquid ratio of 1:50 using 500ml of water for 1 hour. After each wash, the material was filtered and washed again with water at a solid-liquid ratio of 1:50. After three washes, the pH of the solution was measured. The washing was completed when the pH reached 7, yielding solid filter media. The elution recovery rate of Li was 50%, indicating that most of the Li volatilized due to the high temperature.

[0172] Compared with Example 1, Comparative Example 3 shows that when the reduction temperature T1 is too high, lithium volatilizes, reducing the lithium recovery rate. However, the resulting solid filter material has a high degree of reduction and can be used for subsequent dissolution and impurity removal reactions.

[0173] The solid filter media was acid-dissolved using 50 ml of 4.8 mol / L sulfuric acid at a temperature of 70°C (T2). The solution was stirred for 2 hours to obtain the first solution, which had a pH less than 0.

[0174] At room temperature, impurity removal was performed using the same steps as in Example 1 to obtain a second solution. The concentrations of Al, Fe, Ca, and Mg were 0.93 mol / L, 0.47 mol / L, 4.41 mol / L, and 4.55 mol / L, respectively.

[0175] As can be seen from Examples 1 to 8 and Comparative Examples 1 to 3, the recycling method provided in this application can effectively recover lithium, nickel, cobalt, and manganese from the positive electrode of waste ternary lithium batteries. In the second solution containing MeSO4, the concentration of impurity elements is low (the concentration of Al can reach below 1 mg / L, the concentration of Fe can reach below 1 mg / L, the concentration of Ca can reach below 5 mg / L, and the concentration of Mg can reach below 5 mg / L), meaning that the purity of the obtained MeSO4 is high, and the elution recovery rate of Li is high, which is also beneficial for the recovery of lithium. At the same time, the consumption of sulfuric acid is low during the recycling process, resulting in high economic benefits.

[0176] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for recycling the positive electrode of a used battery, comprising the following steps: (1) Obtain the positive electrode material of the waste battery, and pre-treat the positive electrode material to obtain positive electrode powder; (2) Carbon monoxide is prepared by mixing oxalic acid and concentrated sulfuric acid and heating. (3) The carbon monoxide obtained is passed into the positive electrode powder and heat-treated at a temperature T1 of 550°C to 700°C. Then it is washed with water and filtered to obtain solid filter material and lithium-containing filtrate. The solid filter media comprises elemental Me and / or oxide MeO, wherein Me is selected from at least one of Ni, Co, and Mn. (4) mixing the solid filter material with sulfuric acid to perform a heating dissolution reaction to obtain a first solution; wherein the first solution comprises Me 2+ and impurity ions, the impurity ions comprising Al 3+ , Fe 2+ , Ca 2+ , and Mg 2+ , and the pH of the first solution is less than or equal to 2; (5) The impurity ions in the first solution are removed to obtain a purified second solution containing MeSO4.

2. The method according to claim 1, wherein, In step (5), the impurity ions in the first solution are removed, including: Step (5-a): For the Al in the impurity ions... 3+ and Fe 2+ Perform impurity removal treatment a; Step (5-b): Then, remove Ca from the impurity ions. 2+ and Mg 2+ b. Perform impurity removal treatment.

3. The method according to claim 2, wherein, The impurity removal process a in step (5-a) includes: The first solution, alkaline solution, and oxidant are mixed to obtain solution a, which is then subjected to impurity removal reaction a, followed by filtration to obtain filtrate and filter residue. The pH of solution a is 3 to 5.5; preferably, the pH of solution a is 4.5 to 5. The impurity removal process b in step (5-b) includes: The filtrate obtained in step (5-a) is mixed with fluoride to obtain solution b, and impurity removal reaction b is carried out. Then, an adsorbent is added to adsorb the remaining fluoride, and the solution is filtered to obtain the purified second solution containing MeSO4.

4. The method according to claim 3, wherein, The impurity removal process a in step (5-a) includes: mixing the alkaline solution with the first solution to adjust the pH to 3 to 5.5, in order to remove the Al. 3+ Then the oxidizing agent is added to make Fe 2+ It is removed through oxidation and precipitation; or, The impurity removal process a includes: mixing the oxidant with the first solution to make Fe 2+ Oxidation is then performed, followed by the addition of the alkaline solution to adjust the pH to 3 to 5.5, so that Fe... 3+ And Al 3+ Removed after sedimentation.

5. The method according to claim 3, wherein, In step (5-a), at least one of the following conditions must be met: Condition a: The alkali in the alkaline solution is selected from at least one of NaOH, KOH, and ammonia water; Condition b: The oxidant is selected from at least one of H2O2 and O2; Condition c: The amount of the oxidant is: 0.01 mol to 0.1 mol of the oxidant is added for every 10 g of the positive electrode powder.

6. The method according to claim 3, wherein, In step (5-b), at least one of the following conditions must be met: Condition d: The fluoride is selected from at least one of NaF, KF, and NH4F; Condition e: The adsorbent is selected from La2O3; Condition f: The amount of the fluoride used is: 0.05g to 1g of the fluoride is added for every 10g of the positive electrode powder; Condition g: The mass of the fluoride is a, and the mass of the adsorbent is b, satisfying a:b = 1:(10 to 100).

7. The method according to claim 1, wherein, In step (3), at least one of the following conditions must be met: Condition h: For every 10g of the positive electrode powder, the flow rate of carbon monoxide introduced is 1L / min to 3L / min; Condition i: The heat treatment time t1 is 1 hour to 3 hours; Condition j: The solid-liquid ratio of the water washing is 1:(10 to 100), wherein the unit of solid in the water washing is g and the unit of liquid is ml; Condition k: The washing process is completed when the pH of the washing solution after the water washing is 7 to 8.

8. The method according to claim 1, wherein, In step (3), at least one of the following conditions must be met: Condition 1: The positive electrode powder and oxalic acid are mixed first, and then the prepared carbon monoxide is introduced. The mass ratio of the positive electrode powder to oxalic acid is (5 to 10):

1. Condition m: In the lithium-containing filtrate, Li + The elution rate is 95%–99%.

9. The method according to claim 1, wherein, In step (4), the number of moles of sulfuric acid is N1, and the number of moles of the positive electrode powder is N2, with N1:N2 = (1.2 to 2.5):

1.

10. A positive electrode active material precursor, said positive electrode active material precursor is prepared by a purified second solution containing MeSO4, wherein the second solution is the second solution in the method of any one of claims 1 to 9; The positive electrode active material precursor includes Me(OH)2.

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