Method for preparing lithium-rich manganese-based positive electrode material by recycling waste lithium ion battery

Abstract

The invention relates to the technical field of recycling of waste lithium ion batteries, in particular to a method for preparing a lithium-rich manganese-based positive electrode material by recycling waste lithium ion batteries. The method comprises the following steps: mixing the positive electrode material of the waste lithium ion battery with ammonium sulfate, and roasting in an oxygen-free atmosphere to obtain a roasted product; the roasted product is mixed with water for leaching treatment, and leaching liquid rich in lithium and manganese is obtained; mixing the leachate with a carbonate precipitant solution, and carrying out a co-precipitation reaction to obtain a precursor; and roasting the precursor to obtain the lithium-rich manganese-based positive electrode material. According to the method, an ammonium sulfate-assisted low-temperature salinization roasting technology is adopted, and efficient selective synergistic extraction of lithium and manganese is realized based on the difference of properties of metal elements. Besides, the obtained leaching solution rich in lithium and manganese does not need complex purification treatment and can be directly used for integrally synthesizing the precursor of the high-performance lithium-rich manganese-based positive electrode material, the technological process is simple, and the resource recovery efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of waste lithium-ion battery resource utilization technology, and in particular to a method for preparing lithium-rich manganese-based cathode materials from waste lithium-ion batteries. Background Technology

[0002] In recent years, with the rapid development of the electric vehicle industry, the amount of waste lithium-ion batteries commonly used in electric vehicle power batteries has also surged. Improper disposal of waste lithium-ion batteries can lead to various environmental pollution problems, including large amounts of solid waste going to landfills, heavy metal pollution, dust pollution, and water pollution, while also wasting resources. Therefore, the resource recycling of waste lithium-ion batteries is of great significance to environmental protection and resource circulation.

[0003] Currently, the main methods for recycling spent lithium-ion batteries include pyrometallurgy and hydrometallurgy. Pyrometallurgy reduces metal oxides to alloys or elemental metals through high-temperature smelting (usually above 1000℃), followed by refining to separate the target metal. While this method has wide applicability, it suffers from high energy consumption, low lithium recovery rates, severe environmental pollution, and low product added value. Hydrometallurgy is currently the mainstream recycling method. It uses strong acids (such as sulfuric acid and hydrochloric acid) combined with reducing agents (such as H2O2) to dissolve the metals in the cathode material, followed by solvent extraction or chemical precipitation for separation and purification. Although hydrometallurgy has a higher metal recovery rate, it still suffers from high acid consumption, high wastewater treatment costs, and excessively low pH values ​​in the leachate (usually below 1.0). Furthermore, the complex composition and low pH of the metal ion leachate obtained from acid leaching make it difficult to directly use for the regeneration of high-value-added materials.

[0004] In recent years, researchers have tried to improve the methods by using low-temperature roasting and organic acid leaching, but there are still problems such as the need for subsequent acid leaching of roasted products, poor stability of manganese ions in the leaching solution, and complex lithium-manganese co-precipitation process. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a method for preparing lithium-rich manganese-based cathode materials from recycled waste lithium-ion batteries. By using ammonium sulfate-assisted low-temperature salting roasting technology, based on the differences in the properties of metal elements, the efficient and selective synergistic extraction of lithium and manganese is achieved, while significantly inhibiting the leaching of nickel and cobalt.

[0006] To achieve the above objectives, the present invention provides a method for preparing lithium-rich manganese-based cathode materials by recycling spent lithium-ion batteries, comprising the following steps: S1. Mix waste lithium-ion battery cathode material with ammonium sulfate and calcine it under an oxygen-free atmosphere to obtain the calcined product; S2. The roasted product is mixed with water and leached to obtain a leachate rich in lithium and manganese; S3. The lithium- and manganese-rich leachate is mixed with a carbonate precipitant solution to carry out a co-precipitation reaction to obtain the precursor; S4. The precursor is calcined to obtain lithium-rich manganese-based cathode material.

[0007] Preferably, in S1, the mixing ratio of waste lithium-ion battery cathode material and ammonium sulfate satisfies the following relationship: taking half the amount of lithium element and the sum of the amount of manganese element in the waste lithium-ion battery cathode material as the reference value, the ratio of this reference value to the amount of ammonium sulfate is controlled within the range of 1:1 to 1:1.3.

[0008] Preferably, in S1, the heating rate of calcination is 8-12℃ / min, the target temperature is 500-600℃, and the holding time is 2-4h.

[0009] Preferably, in S2, the mass ratio of the calcined product to the volume of water is 1g:5-10mL.

[0010] Preferably, in S3, the carbonate precipitant in the carbonate precipitant solution includes ammonium carbonate and ammonium bicarbonate; the molar ratio of ammonium carbonate to ammonium bicarbonate is 0.5-1.5:1.5-2.5; and the concentration of total carbonate ions in the carbonate precipitant solution is 1-3 mol / L.

[0011] Preferably, in S3, the volume ratio of the lithium- and manganese-rich leachate to the carbonate precipitant solution is 0.5-1.5:0.5-1.5.

[0012] Preferably, in S3, the pH of the coprecipitation reaction is adjusted using ammonia water, and the pH of the coprecipitation reaction is 8-9.

[0013] Preferably, in S4, the calcination includes a first calcination and a second calcination performed sequentially; the first calcination and the second calcination are performed in an air atmosphere.

[0014] Preferably, the heating rate of the first calcination is 3-7℃ / min, the target temperature is 450-550℃, and the holding time is 4-6h.

[0015] Preferably, the heating rate of the second calcination is 3-7℃ / min, the target temperature is 700-800℃, and the holding time is 8-12h.

[0016] The beneficial effects of this invention are as follows: This invention provides a method for preparing lithium-rich manganese-based cathode materials from recycled waste lithium-ion batteries, comprising the following steps: mixing waste lithium-ion battery cathode materials with ammonium sulfate and calcining them under an oxygen-free atmosphere to obtain a calcined product; mixing the calcined product with water and performing a leaching treatment to obtain a leachate rich in lithium and manganese; mixing the leachate rich in lithium and manganese with a carbonate precipitant solution and performing a co-precipitation reaction to obtain a precursor; and calcining the precursor to obtain the lithium-rich manganese-based cathode material.

[0017] This invention employs ammonium sulfate-assisted low-temperature salting roasting technology. Based on the differences in the properties of metal elements, it achieves highly efficient and selective synergistic extraction of lithium and manganese, while significantly inhibiting the leaching of nickel and cobalt. Specifically, the leaching rate of lithium exceeds 99%, the leaching rate of manganese exceeds 92%, while the leaching rates of nickel and cobalt are both below 2%, demonstrating excellent selectivity. Furthermore, through an integrated "roasting-leaching-co-precipitation" process design, the resulting lithium- and manganese-rich leachate requires no complex purification treatment and can be directly used as a precursor for synthesizing high-performance lithium-rich manganese-based cathode materials. This method significantly shortens the process flow, reduces energy consumption and material costs, and achieves seamless integration and closed-loop recycling from spent lithium-ion batteries to high-value-added cathode materials, resulting in high resource utilization. Simultaneously, this invention avoids the use of strong acids throughout the process; the leaching stage is conducted under normal pressure water leaching conditions, and the roasting temperature is low, thus avoiding the use of highly corrosive reagents at the source and significantly reducing the generation and emission of toxic and harmful waste gases and liquids, demonstrating outstanding environmental friendliness.

[0018] 2. Residual reducing components in the leachate (such as SO3) 2- NH3·H2O can effectively stabilize Mn 2+ To prevent oxidation, an optimized ammonium carbonate-ammonium bicarbonate compound precipitation system can be used to obtain a precursor with uniform element distribution and fine particles. After calcination, it is easy to form a lithium-rich manganese-based cathode material with stable structure and complete crystal development. The final product exhibits excellent electrochemical performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process for preparing lithium-rich manganese-based cathode materials by recycling waste lithium-ion batteries in this invention. Detailed Implementation

[0020] This invention provides a method for preparing lithium-rich manganese-based cathode materials by recycling spent lithium-ion batteries, comprising the following steps: S1. Mix waste lithium-ion battery cathode material with ammonium sulfate and calcine it under an oxygen-free atmosphere to obtain the calcined product; S2. The roasted product is mixed with water and leached to obtain a leachate rich in lithium and manganese; S3. The lithium- and manganese-rich leachate is mixed with a carbonate precipitant solution to carry out a co-precipitation reaction to obtain the precursor; S4. The precursor is calcined to obtain lithium-rich manganese-based cathode material.

[0021] In this invention, in step S1, the preparation process of the positive electrode material of waste lithium-ion batteries includes the following steps: The waste lithium-ion batteries are discharged, shredded, magnetically separated, and air-separated to obtain a mixed positive and negative electrode sheet; the mixed positive and negative electrode sheet is heat-treated under a nitrogen atmosphere to remove the electrolyte and binder, while simultaneously magnetizing the positive electrode sheet; then, a belt magnetic separator is used for magnetic separation under conditions of a magnetic roller diameter of 10-14 cm, a magnetic field strength of 4500-5500 G, and a rotation speed of 45-55 r / min to achieve effective separation of the positive and negative electrode sheets (avoiding the negative electrode sheet from entering subsequent processes and causing resource waste); the separated positive electrode sheet is hydraulically crushed to promote efficient dissociation between the positive electrode material and the aluminum foil, as well as between the positive electrode material particles; the obtained crushed product is wet-sieved through a sieve with a pore size of 0.04-0.05 mm to separate the aluminum foil and the positive electrode material suspension; finally, the product is filtered and dried to obtain the desired waste lithium-ion battery positive electrode material.

[0022] In this invention, the waste lithium-ion batteries include waste ternary lithium batteries; the heating rate of the heat treatment is 8-12℃ / min, the target temperature is 500-650℃, and the holding time is 25-60min.

[0023] In this invention, in S1, the mixing ratio of waste lithium-ion battery cathode material and ammonium sulfate satisfies the following relationship: taking the sum of half the amount of lithium element and manganese element in the waste lithium-ion battery cathode material as the reference value, the ratio of this reference value to the amount of ammonium sulfate is controlled within the range of 1:1 to 1:1.3.

[0024] In this invention, in step S1, waste lithium-ion battery cathode material is mixed with ammonium sulfate and ground for 20-35 minutes, and then calcined.

[0025] In this invention, in S1, the setting of the oxygen-free atmosphere includes: after evacuation, nitrogen gas is introduced, and the flow rate of nitrogen gas is set to 150-200 mL / min.

[0026] In this invention, in S1, the heating rate of calcination is 8-12℃ / min, the target temperature is 500-600℃, and the holding time is 2-4h.

[0027] In this invention, during the roasting process in S1, the waste lithium-ion battery cathode material and ammonium sulfate undergo redox and sulfation reactions in a gradual heating and isothermal stage. The main reaction equation can be expressed as: LiNi x Co y Mnz O2 + (NH4)2SO4 → Li2SO4 + MnSO4 + CoO + NiO + NH3 + N2 + H2O. This reaction utilizes the reducing properties of ammonium sulfate and its thermal decomposition products under anaerobic conditions to reduce high-valence metal compounds in waste lithium-ion battery cathode materials, further converting them into lithium sulfate, manganese sulfate, nickel oxide, and cobalt oxide.

[0028] In this invention, in step S1, the tail gas generated during the roasting process is absorbed and treated by a sulfuric acid solution with a concentration of 3-5 mol / L. The absorbent can be used to recover ammonium sulfate through a recrystallization process, thereby realizing the recycling of the reagent.

[0029] In this invention, in step S1, after the calcination is completed, the nitrogen gas supply is stopped and the inlet valve of the tubular furnace is sealed, allowing the system to cool naturally to room temperature in an oxygen-free state, thereby obtaining the calcined product.

[0030] In this invention, in step S2, the mass ratio of the calcined product to the volume of water is 1g:5-10mL; the leaching treatment is carried out under normal pressure, room temperature, and a stirring speed of 300-400r / min; the leaching treatment time is 25-35min; after the leaching treatment is completed, the solution is filtered to obtain a leaching solution rich in lithium and manganese.

[0031] In this invention, in S3, the carbonate precipitant solution contains ammonium carbonate and ammonium bicarbonate; the molar ratio of ammonium carbonate to ammonium bicarbonate is 0.5-1.5:1.5-2.5; the total carbonate ions (referring to CO32-) in the carbonate precipitant solution... 2- +HCO3 - The concentration of ) is 1-3 mol / L.

[0032] In this invention, in S3, the volume ratio of the lithium- and manganese-rich leachate to the carbonate precipitant solution is 0.5-1.5:0.5-1.5.

[0033] In this invention, the coprecipitation reaction is carried out by co-current titration. The lithium and manganese-rich leachate and the carbonate precipitant solution are titrated in a reaction vessel at a rate of 0.5-1.5 mL / min. The coprecipitation reaction is carried out at a temperature of 45-55℃ and a stirring speed of 200-300 r / min. The coprecipitation reaction is stopped after the titration of the leachate and the precipitant solution is completed.

[0034] In this invention, in S3, the pH of the coprecipitation reaction is adjusted using ammonia water with a mass fraction of 25-28%, and the pH of the coprecipitation reaction is 8-9.

[0035] In this invention, after the co-precipitation reaction in step S3 is completed, a suspension is obtained. After turning off the heating and magnetic stirring system, the suspension is allowed to stand for 1-3 hours. Then, it is centrifuged at 3000-4000 r / min for 5-15 min. The precipitate is washed 2-4 times with a water and ethanol mixture with a volume ratio of 2-4:1 (each wash lasts 2-3 min, and the solid-liquid ratio (the ratio of the mass of the precipitate to the volume of the water and ethanol mixture) is 1 g: 5-15 mL). After washing, the precipitate is filtered through a filter membrane with a pore size of 0.04-0.05 μm. The solid obtained by vacuum drying is then subjected to a temperature of 75-85℃ and a pressure of -0.005 to -0.015 MPa to obtain the precursor.

[0036] In this invention, S4 includes a first roasting and a second roasting performed sequentially; the first roasting and the second roasting are performed in an air atmosphere.

[0037] In this invention, the heating rate of the first calcination is 3-7℃ / min, the target temperature is 450-550℃, and the holding time is 4-6h.

[0038] In this invention, the heating rate of the second calcination is 3-7℃ / min, the target temperature is 700-800℃, and the holding time is 8-12h.

[0039] In this invention, a first calcination is carried out in an air atmosphere to promote the full decomposition of carbonates and the formation of amorphous lithium manganese oxides. After the first calcination, the product is naturally cooled to room temperature and ground for 15-25 minutes. Then, a second calcination is carried out in an air atmosphere to crystallize the material at high temperature, forming an ordered lithium-rich manganese-based cathode material crystal structure and promoting the growth of grains into uniform particles.

[0040] In this invention, after calcination, the obtained product is naturally cooled to room temperature, and then water is added at a solid-liquid ratio of 1g:5-15mL. The mixture is stirred and washed for 3-7 minutes at a stirring rate of 350-400r / min. The mixture is then filtered, and the obtained solid is vacuum dried for 22-26 hours at a temperature of 75-85℃ and a pressure of -0.005 to -0.015MPa to obtain lithium-rich manganese-based cathode material.

[0041] A schematic diagram of the process for preparing lithium-rich manganese-based cathode materials from recycled waste lithium-ion batteries in this invention is shown below. Figure 1 As shown.

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0043] In the following embodiments of the present invention, the waste ternary lithium batteries are sourced from a waste lithium battery recycling company.

[0044] Example 1 This embodiment provides a method for preparing lithium-rich manganese-based cathode materials by recycling spent lithium-ion batteries, including the following steps: Waste ternary lithium batteries are discharged, shredded, separated by magnetoelectric separation and air classification to obtain mixed positive and negative electrode sheets. The mixed positive and negative electrode sheets are then heat-treated in a nitrogen atmosphere with a heating rate of 10℃ / min, a target temperature of 600℃, and a holding time of 30min at the target temperature. Then, the positive electrode sheets are obtained by magnetic separation using a belt magnetic separator with a magnetic roller diameter of 12cm, a magnetic field strength of 5000G, and a rotation speed of 50r / min. The positive electrode sheets are then hydraulically crushed, and the crushed products are wet-screened through a sieve with a pore size of 0.045mm to separate the aluminum foil and the positive electrode material suspension. Finally, the products are filtered and dried to obtain the waste lithium-ion battery positive electrode material.

[0045] Waste lithium-ion battery cathode material was mixed with ammonium sulfate. The ratio of half the amount of lithium to the amount of manganese in the waste lithium-ion battery cathode material to the amount of ammonium sulfate was controlled at 1:1.172. The mixture was ground for 20 minutes. After grinding, the material was placed in a tube furnace. The tube furnace was evacuated and nitrogen gas was introduced (nitrogen flow rate of 175 mL / min). The furnace was roasted in an oxygen-free atmosphere. The heating rate was set at 10℃ / min, the target temperature was 550℃, and the holding time at the target temperature was 3 hours. After roasting, the nitrogen gas supply was stopped and the tube furnace inlet valve was sealed. The system was allowed to cool naturally to room temperature in an oxygen-free state to obtain the roasted product.

[0046] The calcined product was mixed with water at a ratio of 1 g: 5 mL and leached under normal pressure, room temperature, and stirring speed of 350 r / min for 30 min. After leaching, the mixture was filtered to obtain a leachate rich in lithium and manganese.

[0047] Ammonium carbonate, ammonium bicarbonate, and water were mixed to obtain a carbonate precipitant solution with a molar ratio of 1:2. The total carbonate concentration in the carbonate precipitant solution was 2.4 mol / L. A lithium- and manganese-rich leachate was mixed with the carbonate precipitant solution at a volume ratio of 1:1. The lithium- and manganese-rich leachate and the carbonate precipitant solution were then titrated separately into a reaction vessel at a rate of 1 mL / min. A co-precipitation reaction was carried out under conditions of a water bath temperature of 50℃ and a stirring speed of 250 r / min (the pH of the co-precipitation reaction was adjusted using 26% ammonia water, and the pH of the co-precipitation reaction was 8.5). After the co-precipitation reaction (tipping) was completed, a suspension was obtained, and the heating was turned off. After being mixed with a magnetic stirring system, the mixture was allowed to stand for 2 hours, followed by centrifugation at 3500 r / min for 10 min. The resulting precipitate was washed three times with a water-ethanol mixture at a volume ratio of 3:1 (each wash lasting 2.5 min, with a solid-liquid ratio of 1 g: 10 mL). After washing, the mixture was filtered through a 0.045 μm pore size membrane. The solid obtained by vacuum drying was then subjected to a temperature of 80 °C and a pressure of -0.01 MPa to obtain the precursor.

[0048] The precursor was heated to 500℃ in air at a heating rate of 5℃ / min and held for 5 hours for the first calcination. After the first calcination, the product was naturally cooled to room temperature and ground for 20 minutes. Then, the temperature was increased to 750℃ at a heating rate of 5℃ / min and held for 10 hours for the second calcination. The product obtained from the second calcination was naturally cooled to room temperature, and then water was added at a solid-liquid ratio of 1g:10mL. The mixture was stirred and washed for 5 minutes at a stirring rate of 350r / min. The mixture was then filtered, and the resulting solid was vacuum dried at 80℃ and -0.01MPa for 24 hours to obtain lithium-rich manganese-based cathode material.

[0049] Example 2 This embodiment provides a method for preparing lithium-rich manganese-based cathode materials by recycling spent lithium-ion batteries, including the following steps: Waste ternary lithium batteries are discharged, shredded, separated by magnetoelectric separation and air classification to obtain mixed positive and negative electrode sheets. The mixed positive and negative electrode sheets are then heat-treated in a nitrogen atmosphere with a heating rate of 10℃ / min, a target temperature of 500℃, and a holding time of 60min at the target temperature. Then, the positive electrode sheets are obtained by magnetic separation using a belt magnetic separator with a magnetic roller diameter of 12cm, a magnetic field strength of 5000G, and a rotation speed of 50r / min. The positive electrode sheets are then hydraulically crushed, and the crushed products are wet-screened through a sieve with a pore size of 0.045mm to separate the aluminum foil and the positive electrode material suspension. Finally, the products are filtered and dried to obtain the waste lithium-ion battery positive electrode material.

[0050] Waste lithium-ion battery cathode material was mixed with ammonium sulfate. The ratio of half the amount of lithium to the amount of manganese in the waste lithium-ion battery cathode material to the amount of ammonium sulfate was controlled at 1:1.172. The mixture was ground for 20 minutes. After grinding, the material was placed in a tube furnace. The tube furnace was evacuated and nitrogen gas was introduced (nitrogen flow rate of 175 mL / min). The furnace was roasted in an oxygen-free atmosphere. The heating rate was set at 10℃ / min, the target temperature was 550℃, and the holding time at the target temperature was 3 hours. After roasting, the nitrogen gas supply was stopped and the tube furnace inlet valve was sealed. The system was allowed to cool naturally to room temperature in an oxygen-free state to obtain the roasted product.

[0051] The calcined product was mixed with water at a ratio of 1g:10mL and leached under normal pressure, room temperature, and stirring speed of 350r / min for 30min. After leaching, the mixture was filtered to obtain a leachate rich in lithium and manganese.

[0052] Ammonium carbonate, ammonium bicarbonate, and water were mixed to obtain a carbonate precipitant solution with a molar ratio of 1:2. The total carbonate concentration in the carbonate precipitant solution was 1.2 mol / L. A lithium- and manganese-rich leachate was mixed with the carbonate precipitant solution at a volume ratio of 1:1. The lithium- and manganese-rich leachate and the carbonate precipitant solution were then titrated separately into a reaction vessel at a rate of 1 mL / min. A co-precipitation reaction was carried out under conditions of a water bath temperature of 50℃ and a stirring speed of 250 r / min (the pH of the co-precipitation reaction was adjusted using 26% ammonia water, and the pH of the co-precipitation reaction was 8.5). After the co-precipitation reaction (tipping) was completed, a suspension was obtained, and the heating was turned off. After being mixed with a magnetic stirring system, the mixture was allowed to stand for 2 hours, followed by centrifugation at 3500 r / min for 10 min. The resulting precipitate was washed three times with a water-ethanol mixture at a volume ratio of 3:1 (each wash lasting 2.5 min, with a solid-liquid ratio of 1 g: 10 mL). After washing, the mixture was filtered through a 0.045 μm pore size membrane. The solid obtained by vacuum drying was then subjected to a temperature of 80 °C and a pressure of -0.01 MPa to obtain the precursor.

[0053] The precursor was heated to 500℃ at a heating rate of 5℃ / min in air for the first calcination, and held at that temperature for 5h. After the first calcination, the product was naturally cooled to room temperature and ground for 25min. Then, it was heated to 750℃ at a heating rate of 5℃ / min and held for 10h for the second calcination. The product obtained from the second calcination was naturally cooled to room temperature, and then water was added at a solid-liquid ratio of 1g:10mL. The mixture was stirred and washed for 5min at a stirring rate of 350r / min. The mixture was then filtered, and the resulting solid was vacuum dried at 80℃ and -0.01MPa for 24h to obtain lithium-rich manganese-based cathode material.

[0054] Example 3 This embodiment provides a method for preparing lithium-rich manganese-based cathode materials by recycling spent lithium-ion batteries, including the following steps: Waste ternary lithium batteries are discharged, shredded, separated by magnetoelectric separation and air classification to obtain mixed positive and negative electrode sheets. The mixed positive and negative electrode sheets are then heat-treated in a nitrogen atmosphere with a heating rate of 10℃ / min, a target temperature of 500℃, and a holding time of 60min at the target temperature. Then, the positive electrode sheets are obtained by magnetic separation using a belt magnetic separator with a magnetic roller diameter of 12cm, a magnetic field strength of 5000G, and a rotation speed of 50r / min. The positive electrode sheets are then hydraulically crushed, and the crushed products are wet-screened through a sieve with a pore size of 0.045mm to separate the aluminum foil and the positive electrode material suspension. Finally, the products are filtered and dried to obtain the waste lithium-ion battery positive electrode material.

[0055] Waste lithium-ion battery cathode material was mixed with ammonium sulfate. The ratio of half the amount of lithium to the amount of manganese in the waste lithium-ion battery cathode material to the amount of ammonium sulfate was controlled at 1:1.172. The mixture was ground for 20 minutes. After grinding, the material was placed in a tube furnace. The tube furnace was evacuated and nitrogen gas was introduced (nitrogen flow rate of 175 mL / min). The furnace was roasted in an oxygen-free atmosphere. The heating rate was set at 10℃ / min, the target temperature was 550℃, and the holding time at the target temperature was 3 hours. After roasting, the nitrogen gas supply was stopped and the tube furnace inlet valve was sealed. The system was allowed to cool naturally to room temperature in an oxygen-free state to obtain the roasted product.

[0056] The calcined product was mixed with water at a ratio of 1 g: 5 mL and leached under normal pressure, room temperature, and stirring speed of 350 r / min for 30 min. After leaching, the mixture was filtered to obtain a leachate rich in lithium and manganese.

[0057] Ammonium carbonate, ammonium bicarbonate, and water were mixed to obtain a carbonate precipitant solution with a molar ratio of 1:2. The total carbonate concentration in the carbonate precipitant solution was 2.4 mol / L. A lithium- and manganese-rich leachate was mixed with the carbonate precipitant solution at a volume ratio of 1:1. The lithium- and manganese-rich leachate and the carbonate precipitant solution were then titrated separately into a reaction vessel at a rate of 1 mL / min. A co-precipitation reaction was carried out under conditions of a water bath temperature of 50℃ and a stirring speed of 250 r / min (the pH of the co-precipitation reaction was adjusted using 26% ammonia water, and the pH of the co-precipitation reaction was 8.5). After the co-precipitation reaction (tipping) was completed, a suspension was obtained, and the heating was turned off. After being mixed with a magnetic stirring system, the mixture was allowed to stand for 2 hours, followed by centrifugation at 3500 r / min for 10 min. The resulting precipitate was washed three times with a water-ethanol mixture at a volume ratio of 3:1 (each wash lasting 2.5 min, with a solid-liquid ratio of 1 g: 10 mL). After washing, the mixture was filtered through a 0.045 μm pore size membrane. The solid obtained by vacuum drying was then subjected to a temperature of 80 °C and a pressure of -0.01 MPa to obtain the precursor.

[0058] The precursor was heated to 500℃ at a heating rate of 5℃ / min in air for the first calcination, and held at that temperature for 5h. After the first calcination, the product was naturally cooled to room temperature and ground for 25min. Then, it was heated to 750℃ at a heating rate of 5℃ / min and held for 10h for the second calcination. The product obtained from the second calcination was naturally cooled to room temperature, and then water was added at a solid-liquid ratio of 1g:10mL. The mixture was stirred and washed for 5min at a stirring rate of 350r / min. The mixture was then filtered, and the resulting solid was vacuum dried at 80℃ and -0.01MPa for 24h to obtain lithium-rich manganese-based cathode material.

[0059] Experimental Example 1 The lithium- and manganese-rich leachate obtained in Example 1 was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the recoveries of Li and Mn were 99.2% and 92.5%, respectively, while the leaching rates of Ni and Co were only 0.3% and 1.5%, respectively.

[0060] Therefore, this invention utilizes the aforementioned method of recycling spent lithium-ion batteries to prepare lithium-rich manganese-based cathode materials. Employing ammonium sulfate-assisted low-temperature salting roasting technology, and leveraging the differences in the properties of metal elements, it achieves highly efficient and selective synergistic extraction of lithium and manganese, while significantly inhibiting the leaching of nickel and cobalt. Furthermore, through an integrated "roasting-leaching-co-precipitation" process design, the resulting lithium- and manganese-rich leachate requires no complex purification treatment and can be directly used as a precursor for synthesizing high-performance lithium-rich manganese-based cathode materials. This method significantly shortens the process flow, reduces energy consumption and material costs, and achieves seamless integration and closed-loop recycling from spent lithium-ion batteries to high-value-added cathode materials, resulting in high resource utilization. Simultaneously, this invention avoids the use of strong acids throughout the process; the leaching stage involves atmospheric pressure water leaching under mild conditions, and the roasting temperature is low, thus preventing the use of highly corrosive reagents at the source and significantly reducing the generation and emission of toxic and harmful waste gases and liquids, demonstrating outstanding environmental friendliness.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for recycling spent lithium-ion batteries to prepare a lithium-rich manganese-based cathode material, characterized in that, The method comprises the following steps: S1. mixing the waste lithium ion battery positive electrode material with ammonium sulfate, and roasting under an oxygen-free atmosphere to obtain a roasting product; S2. mixing the roasting product with water, and performing leaching treatment to obtain a leaching solution rich in lithium and manganese; S3. mixing the leaching solution rich in lithium and manganese with a carbonate precipitant solution, and performing coprecipitation to obtain a precursor; S4. roasting the precursor to obtain a lithium-rich manganese-based positive electrode material.

2. The method according to claim 1, wherein the lithium-rich manganese-based cathode material is prepared from the spent lithium-ion battery by the recycling process, characterized in that, In S1, the mixing ratio of the waste lithium ion battery positive electrode material and ammonium sulfate satisfies the following relationship: taking half of the amount of substance of lithium element and the sum of the amount of substance of manganese element in the waste lithium ion battery positive electrode material as a reference value, the ratio of the reference value to the amount of substance of ammonium sulfate is controlled within the range of 1:1 to 1:1.

3.

3. The method for recycling spent lithium-ion batteries to prepare lithium-rich manganese-based cathode material according to claim 1, characterized in that, In S1, the heating rate of roasting is 8-12℃ / min, the target temperature is 500-600℃, and the holding time is 2-4h.

4. The method for recycling spent lithium-ion batteries to prepare lithium-rich manganese-based cathode material according to claim 1, characterized in that, In S2, the mass of the roasting product to the volume of water is 1g:5-10mL.

5. The method for recycling spent lithium-ion batteries to prepare lithium-rich manganese-based cathode material according to claim 1, characterized in that, In S3, the carbonate precipitant in the carbonate precipitant solution includes ammonium carbonate and ammonium bicarbonate; the molar ratio of ammonium carbonate to ammonium bicarbonate is 0.5-1.5:1.5-2.5; and the total concentration of carbonate in the carbonate precipitant solution is 1-3mol / L.

6. The method for preparing lithium-rich manganese-based cathode materials by recycling spent lithium-ion batteries according to claim 1, characterized in that, In S3, the volume ratio of the leaching solution rich in lithium and manganese to the carbonate precipitant solution is 0.5-1.5:0.5-1.

5.

7. The method of claim 1, wherein the lithium-rich manganese-based cathode material is prepared from the spent lithium-ion battery by the recycling process. In S3, the coprecipitation reaction uses ammonia water to adjust the pH, and the pH of the coprecipitation reaction is 8-9.

8. The method of claim 1, wherein the lithium-rich manganese-based cathode material is prepared from the spent lithium-ion battery by the recycling process. In S4, the roasting includes first roasting and second roasting performed in sequence; the first roasting and the second roasting are performed in an air atmosphere.

9. The method for recycling spent lithium-ion batteries to prepare lithium-rich manganese-based cathode material according to claim 8, characterized in that, The heating rate of the first roasting is 3-7℃ / min, the target temperature is 450-550℃, and the holding time is 4-6h.

10. The method for recycling spent lithium-ion batteries to prepare lithium-rich manganese-based cathode material according to claim 8, characterized in that, The heating rate of the second roasting is 3-7℃ / min, the target temperature is 700-800℃, and the holding time is 8-12h.

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