A method for recovering lithium, nickel, cobalt and manganese from waste ternary lithium batteries by step leaching

Abstract

The application discloses a method for recycling lithium, nickel, cobalt and manganese in waste ternary lithium batteries by step leaching, and comprises the following steps: 1) pretreatment: calcining positive and negative electrode powders of the waste ternary lithium batteries for standby; 2) leaching and separating lithium: mixing the calcined powder in the step 1) with a lithium leaching agent to leach lithium, and after the leaching is completed, performing first solid-liquid separation to obtain a lithium carbonate solution; 3) leaching and separating nickel: mixing the solid obtained by the first solid-liquid separation with a nickel leaching agent to leach nickel, and after the leaching is completed, performing second solid-liquid separation to obtain a nickel compound solution; 4) leaching and separating manganese: mixing the solid obtained by the second solid-liquid separation with a manganese leaching agent to leach manganese, and after the leaching is completed, performing third solid-liquid separation to obtain a manganese compound solution, and the solid obtained by the third solid-liquid separation is a mixture of a cobalt compound and carbon. The application can deeply separate the nickel, cobalt, manganese and lithium, has high recovery rate, can realize continuous production and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling technology, specifically to a method for recovering lithium, nickel, cobalt, and manganese from waste ternary lithium batteries using a stepwise leaching process. Background Technology

[0002] Ternary nickel-cobalt-manganese cathode materials are important materials for lithium-ion batteries, possessing significant advantages such as high energy density, good stability, and high safety. Improper disposal of retired lithium-ion batteries can cause environmental pollution and resource waste. Nickel-cobalt-manganese ternary lithium batteries contain large amounts of valuable metals such as lithium, cobalt, and manganese. Compared to mined ore, they have a higher content of valuable metals and fewer impurities, thus possessing high recycling value.

[0003] Currently, industrial processes typically employ pyrometallurgy, hydrometallurgy, or a combination of both to recover valuable metal elements from waste batteries. Pyrometallurgical recycling involves placing waste lithium-ion batteries in a furnace at temperatures exceeding 1000°C for high-temperature smelting. During this process, organic matter in the batteries is burned off, metals with melting points below the reaction temperature form alloys, low-boiling-point metals and their compounds are recovered through condensation, and other impurities are transferred to the slag phase or form gases. Pyrometallurgical recycling is widely used and can process different types of waste lithium-ion batteries. It offers advantages such as a short recycling process and high efficiency. However, some manganese and lithium are still lost in the slag during the recycling process, resulting in a significant loss of valuable metals and contributing to air pollution. Hydrometallurgical recycling primarily uses hydrometallurgical methods to separate and enrich valuable metal components from waste lithium-ion batteries, obtaining products such as soluble metal salts or precipitates. It offers advantages such as low investment, flexible production, and high metal recovery rates. However, the process requires strong acids and alkalis, as well as extractants, which can corrode production equipment and pose risks of environmental pollution and production safety.

[0004] How to solve the problems of low recovery rate of valuable metals, equipment corrosion and high cost in the existing recycling process of waste ternary batteries is the difficulty of battery recycling. Chinese patent application number 2020109779134 discloses a method for recycling ternary lithium battery cathode material, including the following steps: (1) adding lithium battery cathode powder to an inorganic acid without reducing agent for leaching to obtain an acid leaching solution; (2) adjusting the pH of the acid leaching solution, using P227 as an extractant for nickel-cobalt-manganese co-extraction and separating lithium at the same time; (3) the organic phase of nickel-cobalt-manganese co-extraction is back-extracted by acid to obtain a back-extraction solution, and oxalic acid is used as a co-precipitant to precipitate the back-extraction solution to prepare a nickel-cobalt-manganese precursor; (4) calcining the nickel-cobalt-manganese precursor at high temperature to prepare a powdered lithium battery cathode material. This technical solution achieves the separation of nickel, cobalt, and manganese from lithium through solvent extraction, and also enables the control of cathode materials for different types of ternary batteries. However, this patent cannot further achieve deep separation of nickel, cobalt, and manganese. Therefore, this invention aims to develop a stepwise leaching method for recovering lithium, nickel, cobalt, and manganese from waste ternary lithium batteries to better meet actual production needs. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a stepwise leaching method for recovering lithium, nickel, cobalt, and manganese from waste ternary lithium batteries, so as to achieve deep separation of nickel, cobalt, and manganese, improve the recovery rate, and reduce the recovery cost.

[0006] The technical problem solved by this invention is achieved by the following technical solution:

[0007] A method for recovering lithium nickel cobalt manganese from spent ternary lithium batteries using a stepwise leaching process includes the following steps:

[0008] 1) Pretreatment: Calcining the positive and negative electrode powders of waste ternary lithium batteries for later use;

[0009] 2) Lithium leaching separation: The calcined powder from step 1) is mixed with the lithium leaching agent to leach lithium. After leaching, the first solid-liquid separation is performed to obtain a lithium carbonate solution.

[0010] 3) Leaching separation of nickel: The solid obtained from the first solid-liquid separation is mixed with the nickel leaching agent to leach nickel. After leaching, a second solid-liquid separation is performed to obtain a nickel compound solution.

[0011] 4) Leaching and separation of manganese: The solid obtained from the second solid-liquid separation is mixed with the manganese leaching agent for leaching. After leaching, a third solid-liquid separation is performed. The liquid obtained is a manganese compound solution, and the solid obtained from the third solid-liquid separation is a mixture of cobalt compound and carbon. The mixture of cobalt compound and carbon is heated to remove the carbon.

[0012] Preferably, the positive and negative electrode powders of waste ternary lithium batteries are mixed evenly before calcination.

[0013] Furthermore, in step 1), the calcination process is carried out under the protection of an inert gas.

[0014] Furthermore, in step 1), the heating rate is 1–20 °C / min.

[0015] Furthermore, in step 1), the calcination temperature is 500–700°C.

[0016] Furthermore, in step 1), the calcination time is 1 to 10 hours.

[0017] Further, in step 2), the lithium impregnation agent includes one or more of water, sodium chloride solution, and potassium chloride solution.

[0018] Preferably, in step 2), the lithium impregnation agent is composed of sodium chloride solution and potassium chloride solution, and the concentrations of sodium chloride solution and potassium chloride solution are 0.01 to 0.5 mol / L.

[0019] Furthermore, in step 2), the leaching solid-liquid ratio is 1:5 to 50.

[0020] Furthermore, in step 2), the leaching is carried out under stirring at a speed of 250–600 r / min for a duration of 0.5–3 h at room temperature.

[0021] Furthermore, in step 3), the nickel immersion agent includes citrate, and also includes ammonia and / or ammonium salt.

[0022] Preferably, the concentration of ammonia water or ammonium salt solution is 0.5–5 mol / L.

[0023] Preferably, the ammonium salt solution is one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate.

[0024] Preferably, the citrate solution is one or more of sodium citrate and potassium citrate, and the concentration of the citrate solution is 0.1 to 1 mol / L.

[0025] Furthermore, in step 3), the leaching solid-liquid ratio is 1:5 to 50.

[0026] Furthermore, in step 3), the leaching temperature is 30–60°C.

[0027] Furthermore, in step 3), the leaching is carried out under stirring at a speed of 250–600 r / min for a duration of 0.5–3 h.

[0028] Further, in step 3), the nickel compound solution is evaporated and crystallized to obtain a nickel compound solid, which is then further heated to decompose the nickel compound solid to obtain nickel oxide.

[0029] Furthermore, in step 3), the heating temperature is 600–700℃ and the heating time is 1–3 hours.

[0030] Furthermore, in step 3), the heating rate is 1–20 °C / min.

[0031] Further, in step 4), the manganese impregnation agent is an aqueous solution composed of a hydrogen bond acceptor, a hydrogen bond donor, and a diluent.

[0032] Furthermore, in step 4), the leaching solid-liquid ratio is 1:5 to 50.

[0033] Furthermore, in step 4), the reaction temperature is 40–90°C. Temperature control is crucial; too low a temperature will result in incomplete coordination, affecting the manganese leaching rate; too high a temperature will cause the formed complex to decompose, thus affecting the leaching rate and cobalt-manganese separation efficiency.

[0034] Furthermore, in step 4), the leaching is carried out under stirring at a speed of 250–600 r / min for a duration of 0.5–3 h.

[0035] Further, in step 4), the concentration of the hydrogen bond donor in the manganese impregnation agent is 2.5 to 5 mol / L, and the hydrogen bond donor is one or more of formic acid, acetic acid, oxalic acid, citric acid, tartaric acid, malic acid, lactic acid, and ascorbic acid.

[0036] Further, in step 4), the concentration of hydrogen bond acceptors in the manganese impregnation agent is 0.5–2.5 mol / L, and the hydrogen bond acceptors are one or more of choline chloride, succinylcholine chloride, acetylcholine chloride, and carbamoylcholine chloride.

[0037] Further, in step 4), the concentration of the diluent in the manganese impregnation agent is 3-8 mol / L, and the diluent is one or more of dimethyl sulfoxide, dimethylacetamide, and diethylacetamide.

[0038] Further, in step 4), a manganese precipitant is added dropwise to the manganese compound solution to produce a precipitate, which is a solid manganese compound.

[0039] Further, in step 4), the concentration of the manganese precipitant is 0.1–5 mol / L, and the manganese precipitant is one or more of sodium hydroxide, ammonia, and potassium hydroxide.

[0040] Further, in step 4), the manganese compound solid is heated to obtain manganese tetroxide.

[0041] Furthermore, in step 4), the heating temperature is 800–1000℃, and the heating time is 1–3 hours.

[0042] Furthermore, in step 4), the heating rate is 1–20 °C / min.

[0043] Furthermore, in step 4), after the manganese compound solution precipitates, the solid-liquid separation solution is adjusted to pH 6-8 and then recycled as a manganese leaching agent.

[0044] Furthermore, in step 4), after the mixture of cobalt compound and carbon is heated, the cobalt compound decomposes to obtain cobalt tetroxide, and the carbon is oxidized to carbon dioxide.

[0045] The heating temperature is 450–550℃, and the heating time is 1–3 hours.

[0046] Furthermore, in step 4), the heating rate is 1–20 °C / min.

[0047] In this invention, the manganese leaching agent coordinates with cobalt and manganese to form complexes. In the complex formed by cobalt and the manganese leaching agent, some of the coordinating groups are replaced by water, forming precipitates that remain in the filter residue. In the complex formed by manganese and the manganese leaching agent, the coordinating groups are difficult to replace with water, so manganese is leached into the solution. Improper control of the ratio and concentration will affect the coordination of cobalt and manganese, impacting the separation efficiency and recovery rate. The concentration of each component in the manganese leaching agent is crucial; maintaining appropriate concentrations ensures a suitable coordination environment, thereby enabling better selective leaching of manganese.

[0048] In the nickel leaching separation step, the difference in nickel-cobalt-manganese complexation is utilized to separate nickel. Nickel can coordinate with citrate, ammonia, and ammonium ions to form water-soluble complexes, while cobalt and manganese cannot coordinate with these compounds, thus achieving the separation of nickel and cobalt / manganese. The selection of the nickel leaching agent is extremely important, as it should selectively leach nickel into the solution while retaining cobalt and manganese in the solid slag.

[0049] Beneficial effects: The stepwise leaching method for recovering lithium, nickel, cobalt, and manganese from waste ternary lithium batteries described in this invention utilizes the differences in complexation between different metal ions and coordinating molecules to achieve stepwise leaching of lithium, nickel, and manganese from waste lithium-ion batteries. Through processes such as calcination of positive and negative electrode powder, selective leaching separation of lithium, selective leaching separation of nickel, selective leaching separation of manganese, and finally thermal decomposition separation of cobalt, efficient stepwise separation of lithium, nickel, cobalt, and manganese is achieved.

[0050] The method for stepwise recycling of lithium nickel cobalt manganese from waste ternary nickel-cobalt-manganese lithium-ion batteries described in this invention is carried out under process conditions without the addition of extractants and strong acids. Compared with traditional recycling processes, it can reduce recycling costs, reduce equipment corrosion, and extend service life.

[0051] The process of this invention is simple to operate, has a high recovery rate, is environmentally friendly, and can be continuously produced, making it suitable for industrial production. Attached Figure Description

[0052] Figure 1 This is a schematic diagram illustrating the stepwise leaching recovery of nickel, cobalt, and manganese from spent ternary lithium batteries according to the present invention.

[0053] Figure 2 The image shows the XRD pattern of the positive and negative electrode mixed powder after calcination in Example 1.

[0054] Figure 3 The graph shows the recovery rates of lithium, nickel, cobalt, and manganese in Example 1.

[0055] Figure 4 The graph shows the recovery rates of lithium, nickel, cobalt, and manganese in Example 2.

[0056] Figure 5 The graph shows the recovery rates of lithium, nickel, cobalt, and manganese in Comparative Example 1. Detailed Implementation

[0057] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0058] The method for recovering lithium, nickel, cobalt, and manganese from waste ternary lithium batteries using a stepwise leaching process, as described in this embodiment, is as follows: Figure 1 As shown, it includes the following steps:

[0059] 1) Pretreatment: The positive and negative electrode powders of waste ternary lithium batteries are calcined for later use. Specifically, the positive and negative electrode powders of waste nickel-cobalt-manganese ternary lithium-ion batteries are mixed evenly, and the contents of each component are determined by ICP as follows: lithium 5.4%, nickel 22.1%, cobalt 8.5%, and manganese 11.5%. 100g of the mixed powder is weighed and placed in a muffle furnace. Under nitrogen protection, the temperature is increased to 700℃ at a heating rate of 10℃ / min, and calcined at high temperature for 1 hour for later use.

[0060] 2) Lithium leaching separation:

[0061] Preparation of lithium impregnation agent: Prepare a 0.1 mol / L sodium chloride solution using water as the solvent;

[0062] The calcined powder from step 1) was mixed with a lithium leaching agent to leach lithium at a solid-liquid ratio of 1:20. Leaching was carried out under stirring at 250 r / min for 3 h. The first solid-liquid separation was performed by filtration. The filtrate obtained was a lithium carbonate solution, which was evaporated and crystallized to obtain lithium carbonate crystals. The filter residue was then used in the next reaction step.

[0063] 3) Leaching to separate nickel:

[0064] Preparation of nickel immersion agent: Using water as solvent, prepare a mixed solution with an ammonium chloride concentration of 2 mol / L and a sodium citrate concentration of 0.1 mol / L.

[0065] The solid obtained from the first solid-liquid separation was mixed with a nickel leaching agent to leach nickel. The solid-liquid ratio was 1:50, the reaction temperature was 60℃, the leaching was carried out under stirring at room temperature with a stirring speed of 600 r / min, and the leaching time was 1 h. After leaching, a second solid-liquid separation was carried out by filtration. The liquid obtained was a nickel compound solution, and the filter residue entered the next reaction step.

[0066] A nickel compound solution was evaporated and crystallized to obtain a nickel compound solid. The nickel compound solid was then heated in air to decompose it into nickel oxide. The temperature was increased to 700°C at a rate of 5°C / min and then heated at 700°C for 1 hour.

[0067] 4) Leaching and separation of manganese:

[0068] Prepare the manganese leaching agent: using water as the solvent, prepare a mixed solution with a citric acid concentration of 4.5 mol / L, an acetylcholine chloride concentration of 2.5 mol / L, and a dimethyl sulfoxide concentration of 5.5 mol / L.

[0069] Prepare a manganese precipitant by using water as a solvent and preparing a 2 mol / L sodium hydroxide solution.

[0070] The solid obtained from the second solid-liquid separation was mixed with a manganese leaching agent for leaching. The solid-liquid ratio was 1:50, the reaction temperature was 90℃, the leaching was carried out under stirring at a stirring speed of 600 r / min, and the leaching time was 2 h.

[0071] After leaching, a third solid-liquid separation is performed by filtration. The resulting liquid is a manganese compound solution, and the resulting solid is a mixture of cobalt compound and carbon.

[0072] Manganese precipitant was slowly added dropwise to the manganese compound solution until the pH of the system reached 10.4–10.8, at which point the addition was stopped. The filter residue obtained was a solid manganese compound. This residue was then heated in air to decompose the manganese compound into manganese tetroxide. The heating rate was 10 °C / min, the heating temperature was 1000 °C, and the heating time was 1 h. The filtrate was adjusted to pH 6–8 and then used as a selective manganese leaching agent.

[0073] A mixture of cobalt compounds and carbon was heated in air to decompose cobalt tetroxide, while carbon was oxidized to carbon dioxide. The heating temperature was 550°C, the heating rate was 5°C / min, and the heating time was 1 h. Carbon was thus removed.

[0074] After the reaction was completed, the mass of each product was weighed using a balance, yielding 27.0 g of lithium carbonate, 26.4 g of nickel oxide, 10.8 g of cobalt tetroxide, and 14.6 g of manganese tetroxide. The recovery rates of each element were calculated to be 95% for lithium, 94% for nickel, 93% for cobalt, and 91% for manganese.

[0075] Figure 2 The image shows the XRD pattern of the positive and negative electrode mixed powder after calcination in Example 1.

[0076] Figure 3 The graph shows the recovery rates of lithium, nickel, cobalt, and manganese in Example 1.

[0077] Example 2

[0078] The method for recovering lithium, nickel, cobalt, and manganese from waste ternary lithium batteries using a stepwise leaching process, as described in this embodiment, is as follows: Figure 1 As shown, it includes the following steps:

[0079] 1) Pretreatment: The positive and negative electrode powders of waste ternary lithium batteries are calcined for later use. Specifically, the positive and negative electrode powders of waste nickel-cobalt-manganese ternary lithium-ion batteries are mixed evenly, and the contents of each component are determined by ICP as follows: lithium 5.4%, nickel 22.1%, cobalt 8.5%, and manganese 11.5%. 100g of the mixed powder is weighed and placed in a muffle furnace. Under nitrogen protection, the temperature is increased to 700℃ at a heating rate of 5℃ / min, and calcined at high temperature for 1 hour for later use.

[0080] 2) Lithium leaching separation:

[0081] Preparation of lithium impregnation agent: Prepare a 0.1 mol / L sodium chloride solution using water as the solvent;

[0082] The calcined powder from step 1) was mixed with a lithium leaching agent to leach lithium at a solid-liquid ratio of 1:30. Leaching was carried out under stirring at 500 r / min for 1 h. The first solid-liquid separation was performed by filtration. The filtrate obtained was a lithium carbonate solution, which was evaporated and crystallized to obtain lithium carbonate crystals. The filter residue was then used in the next reaction step.

[0083] 3) Leaching to separate nickel:

[0084] Prepare the nickel immersion agent: Prepare a mixed solution with ammonium sulfate concentration of 2 mol / L and potassium citrate concentration of 0.1 mol / L.

[0085] The solid obtained from the first solid-liquid separation was mixed with a nickel leaching agent to leach nickel. The solid-liquid ratio was 1:20, the reaction temperature was 30℃, the leaching was carried out under stirring at room temperature with a stirring speed of 400 r / min, and the leaching time was 2 h. After the leaching was completed, a second solid-liquid separation was carried out by filtration. The liquid obtained was a nickel compound solution, and the filter residue entered the next reaction step.

[0086] A nickel compound solution was evaporated and crystallized to obtain a nickel compound solid. The nickel compound solid was then heated in air to decompose it into nickel oxide. The temperature was increased to 650°C at a rate of 5°C / min for 2 hours.

[0087] 4) Leaching and separation of manganese:

[0088] Prepare the manganese leaching agent: using water as the solvent, prepare a mixed solution with oxalic acid concentration of 3 mol / L, choline chloride concentration of 1 mol / L, and diethylacetamide concentration of 4 mol / L.

[0089] Prepare a manganese precipitant by using water as a solvent to prepare a 1 mol / L sodium hydroxide solution.

[0090] The solid obtained from the second solid-liquid separation was mixed with a manganese leaching agent for leaching. The solid-liquid ratio was 1:20, the reaction temperature was 60℃, the leaching was carried out under stirring at a stirring speed of 450 r / min, and the leaching time was 3 h.

[0091] After leaching, a third solid-liquid separation is performed by filtration. The resulting liquid is a manganese compound solution, and the resulting solid is a mixture of cobalt compound and carbon.

[0092] Manganese precipitant was slowly added dropwise to the manganese compound solution until the pH of the system reached 10.4–10.8, at which point the addition was stopped. The filter residue obtained was a solid manganese compound. This residue was then heated in air to decompose the manganese compound into manganese tetroxide. The heating rate was 5 °C / min, the heating temperature was 900 °C, and the heating time was 1.5 h. The filtrate was adjusted to pH 6–8 and then used as a selective manganese leaching agent.

[0093] A mixed solid of cobalt compound and carbon was heated in air to decompose cobalt tetroxide, while carbon was oxidized to carbon dioxide. The heating temperature was 500℃, the heating rate was 10℃ / min, and the heating time was 2 h. Carbon was thus removed.

[0094] After the reaction was completed, the mass of each product was weighed using a balance, yielding 25.4 g of lithium carbonate, 26.9 g of nickel oxide, 10.5 g of cobalt tetroxide, and 14.2 g of manganese tetroxide. The recovery rates of each element were calculated to be 89% for lithium, 96% for nickel, 91% for cobalt, and 89% for manganese.

[0095] Figure 4 The graph shows the recovery rates of lithium, nickel, cobalt, and manganese in Example 2.

[0096] Comparative Example 1

[0097] The method for recovering lithium, nickel, cobalt, and manganese from spent ternary lithium batteries using a stepwise leaching process, as described in this comparative embodiment, is as follows: Figure 1 As shown, it includes the following steps:

[0098] 1) Pretreatment: The positive and negative electrode powders of waste ternary lithium batteries are calcined for later use. Specifically, the positive and negative electrode powders of waste nickel-cobalt-manganese ternary lithium-ion batteries are mixed evenly, and the contents of each component are determined by ICP as follows: lithium 5.4%, nickel 22.1%, cobalt 8.5%, and manganese 11.5%. 100g of the mixed powder is weighed and placed in a muffle furnace. Under nitrogen protection, the temperature is increased to 700℃ at a heating rate of 10℃ / min, and calcined at high temperature for 1 hour for later use.

[0099] 2) Lithium leaching separation:

[0100] Preparation of lithium impregnation agent: Prepare a 0.1 mol / L sodium chloride solution using water as the solvent;

[0101] The calcined powder from step 1) was mixed with a lithium leaching agent to leach lithium at a solid-liquid ratio of 1:20. Leaching was carried out under stirring at 250 r / min for 3 h. The first solid-liquid separation was performed by filtration. The filtrate obtained was a lithium carbonate solution, which was evaporated and crystallized to obtain lithium carbonate crystals. The filter residue was then used in the next reaction step.

[0102] 3) Leaching to separate nickel:

[0103] Preparation of nickel immersion agent: Prepare a mixed solution with ammonium chloride concentration of 0.2 mol / L and sodium citrate concentration of 0.1 mol / L using water as solvent.

[0104] The solid obtained from the first solid-liquid separation was mixed with a nickel leaching agent to leach nickel. The solid-liquid ratio was 1:50, the reaction temperature was 60℃, the leaching was carried out under stirring at room temperature with a stirring speed of 600 r / min, and the leaching time was 1 h. After leaching, a second solid-liquid separation was carried out by filtration. The liquid obtained was a nickel compound solution, and the filter residue entered the next reaction step.

[0105] A nickel compound solution was evaporated and crystallized to obtain a nickel compound solid. The nickel compound solid was then heated in air to decompose it into nickel oxide. The temperature was increased to 700°C at a rate of 5°C / min and then heated at 700°C for 1 hour.

[0106] 4) Leaching and separation of manganese:

[0107] Prepare the manganese leaching agent: using water as the solvent, prepare a mixed solution with a citric acid concentration of 1 mol / L, an acetylcholine chloride concentration of 0.5 mol / L, and a dimethyl sulfoxide concentration of 2 mol / L.

[0108] Prepare a manganese precipitant by using water as a solvent and preparing a 2 mol / L sodium hydroxide solution.

[0109] The solid obtained from the second solid-liquid separation was mixed with a manganese leaching agent for leaching. The solid-liquid ratio was 1:50, the reaction temperature was 30℃, the leaching was carried out under stirring at a stirring speed of 600 r / min, and the leaching time was 2 h.

[0110] After leaching, a third solid-liquid separation is performed by filtration. The resulting liquid is a manganese compound solution, and the resulting solid is a mixture of cobalt compound and carbon.

[0111] Manganese precipitant was slowly added dropwise to the manganese compound solution until the pH of the system reached 10.4–10.8, at which point the addition was stopped. The filter residue obtained was a solid manganese compound. This residue was then heated in air to decompose the manganese compound into manganese tetroxide. The heating rate was 10 °C / min, the heating temperature was 1000 °C, and the heating time was 1 h. The filtrate was adjusted to pH 6–8 and then used as a selective manganese leaching agent.

[0112] A mixture of cobalt compounds and carbon was heated in air to decompose cobalt tetroxide, while carbon was oxidized to carbon dioxide. The heating temperature was 550°C, the heating rate was 5°C / min, and the heating time was 1 h. Carbon was thus removed.

[0113] After the reaction was completed, the mass of each product was weighed using a balance, yielding 26.7g of lithium carbonate, 11.8g of nickel oxide, 10.6g of cobalt tetroxide, and 4.3g of manganese tetroxide. The recovery rates of each element were calculated to be 94% for lithium, 42% for nickel, 91% for cobalt, and 27% for manganese.

[0114] Figure 5 The graph shows the recovery rates of lithium, nickel, cobalt, and manganese in Comparative Example 1.

[0115] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries using a stepwise leaching process, characterized in that, Includes the following steps: 1) Pretreatment: Calcining the positive and negative electrode powders of waste ternary lithium batteries for later use; 2) Lithium leaching separation: The calcined powder from step 1) is mixed with the lithium leaching agent to leach lithium. After leaching, the first solid-liquid separation is performed, and the resulting liquid is a lithium carbonate solution. 3) Leaching and separating nickel: The solid obtained from the first solid-liquid separation is mixed with a nickel leaching agent to leach nickel. The nickel leaching agent includes citrate, ammonia and / or ammonium salt; wherein the concentration of the citrate solution is 0.1~1 mol / L, and the concentration of the ammonia or ammonium salt solution is 0.5~5 mol / L; after leaching, a second solid-liquid separation is performed to obtain a nickel compound solution. 4) Leaching and separating manganese: The solid obtained from the second solid-liquid separation is mixed with a manganese leaching agent for leaching. The manganese leaching agent consists of hydrogen bond acceptors, hydrogen bond donors, and a diluent. The hydrogen bond donors are one or more of formic acid, acetic acid, oxalic acid, citric acid, tartaric acid, malic acid, lactic acid, and ascorbic acid. The hydrogen bond acceptors are one or more of choline chloride, succinylcholine chloride, acetylcholine chloride, and ammonium formylcholine chloride. The concentration of the hydrogen bond donors is 2.5~5 mol / L, the concentration of the hydrogen bond acceptors is 0.5~2.5 mol / L, and the concentration of the diluent is 3~8 mol / L. The leaching reaction temperature is 40~90℃. After leaching, a third solid-liquid separation is performed. The liquid obtained is a manganese compound solution, and the solid obtained from the third solid-liquid separation is a mixture of cobalt compound and carbon. The mixture of cobalt compound and carbon is heated to remove the carbon.

2. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 1, characterized in that, In step 1), the calcination process is carried out under the protection of inert gas, with a heating rate of 1~20℃ / min, a calcination temperature of 500~700℃, and a calcination time of 1~10 hours.

3. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 1, characterized in that, In step 2), the lithium leaching agent includes one or more of water, sodium chloride solution, and potassium chloride solution; the solid-liquid ratio of leaching is 1:5~50, leaching is carried out under stirring at a stirring speed of 250~600 r / min, the leaching time is 0.5~3 h, and leaching is carried out at room temperature.

4. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 1, characterized in that, In step 3), the solid-liquid ratio is 1:5~50, the leaching temperature is 30~60℃, the leaching is carried out under stirring, the stirring speed is 250~600r / min, and the leaching time is 0.5~3h.

5. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 1, characterized in that, In step 3), the nickel compound solution is evaporated and crystallized to obtain a nickel compound solid. The nickel compound solid is then further heated to decompose it into nickel oxide. The heating rate is 1~20℃ / min, the heating temperature is 600~700℃, and the heating time is 1~3h.

6. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 1, characterized in that, In step 4), the solid-liquid ratio for leaching is 1:5~50, leaching is carried out under stirring at a speed of 250~600 r / min, and the leaching time is 0.5~3 h.

7. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 6, characterized in that, The diluent is one or more of dimethyl sulfoxide, dimethylacetamide, and diethylacetamide.

8. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 1, characterized in that, In step 4), a manganese precipitant is added dropwise to the manganese compound solution to produce a precipitate, which is a solid manganese compound. The concentration of the manganese precipitant is 0.1~5 mol / L, and the manganese precipitant is one or more of sodium hydroxide, ammonia, and potassium hydroxide.

9. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 8, characterized in that, The solid manganese compound is heated to obtain manganese tetroxide. The heating rate is 1~20℃ / min, the heating temperature is 800~1000℃, and the heating time is 1~3h. After the manganese compound solution produces a precipitate, the solid-liquid separation solution is adjusted to pH 6~8 and then used as a manganese leaching agent for recycling.

10. The method for recovering lithium nickel cobalt manganese from waste ternary lithium batteries by stepwise leaching according to claim 1, characterized in that, In step 4), after the mixture of cobalt compound and carbon is heated, the cobalt compound decomposes to obtain cobalt tetroxide, and the carbon is oxidized to carbon dioxide. The heating rate is 1~20℃ / min, the heating temperature is 450~550℃, and the heating time is 1~3h.

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