Method for recycling waste lithium manganate positive electrode material

Abstract

A method for recycling a waste lithium manganate positive electrode material. The method comprises: firstly, mixing a waste lithium manganate positive electrode material with sulfuric acid, and then carrying out a hydrothermal reaction to obtain manganese dioxide and a washing solution; then, reacting the washing solution with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate; and finally, mixing manganese dioxide, lithium sulfate and lithium hydroxide monohydrate, followed by sintering, washing and tempering treatments in sequence, thereby obtaining the recycled lithium manganate positive electrode material. The method achieves the effective recovery of manganese and lithium.

Description

A method for recycling waste lithium manganese oxide positive electrode material Technical Field

[0001] The invention belongs to the technical field of recycling waste lithium manganate positive electrode materials, and in particular relates to a method for recycling waste lithium manganate positive electrode materials. Background Art

[0002] As lithium batteries age, their material structure gradually degrades and their electrochemical performance diminishes. In recent years, a significant amount of spent lithium-ion batteries has been generated. Lithium-ion batteries are typically composed of metals / metal oxides, organic chemicals, and metal shells. Failure to properly dispose of spent lithium-ion batteries can cause serious harm to human health and the environment. At the same time, recycling spent lithium-ion batteries offers significant economic benefits. Spent lithium-ion batteries can be considered a gold mine rich in metals such as lithium, nickel, cobalt, and manganese. From the perspective of environmental protection and resource recycling, spent lithium-ion batteries offer significant economic and environmental benefits.

[0003] Currently, research on the recycling of spent lithium-ion batteries (LIBs) is primarily focused on three processes: pyrometallurgy, hydrometallurgy, and biometallurgy. Pyrometallurgy primarily involves burning off the binder and carbon in battery components through high-temperature treatment, thereby separating the active materials. While the pyrometallurgical process is simple and easy to implement, it has disadvantages such as high energy consumption and the generation of waste gases. Biometallurgy selectively extracts metal elements such as manganese, cobalt, lithium, and nickel through the metabolic processes of fungi. However, biometallurgy is sensitive to metal concentration, temperature, and other external factors, and its leaching rate is low, requiring continuous research and improvement. Hydrometallurgy is considered an effective method for recycling spent LIBs. The key component of the hydrometallurgical process is the leaching process, which involves the synergistic action of an acid (HCl, H2SO4, HNO3) and a reducing agent (H2O2) to reduce the valence state of transition metals and achieve efficient leaching. While H2O2 is undoubtedly effective as a reducing agent, it has drawbacks such as poor stability, explosiveness, and high risk. It can be seen that there are various problems in the three processes for recycling waste lithium-ion batteries, and there is an urgent need to provide a method for recycling waste lithium manganese oxide positive electrode materials with simple process and convenient operation.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to provide a method for recycling waste lithium manganese oxide positive electrode materials to solve the technical problems of complex process, high energy consumption, waste gas generation and low leaching rate in the recycling process of waste lithium manganese oxide positive electrode materials in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for recycling waste lithium manganese oxide positive electrode materials, comprising the following steps:

[0008] (1) mixing waste lithium manganate positive electrode material and sulfuric acid and performing a hydrothermal reaction to obtain manganese dioxide and a washing solution;

[0009] (2) reacting the washing liquid from step (1) with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate;

[0010] (3) The manganese dioxide obtained in step (1) and the lithium sulfate and lithium hydroxide monohydrate obtained in step (2) are mixed and then sintered, washed and tempered in sequence to obtain a recovered lithium manganate positive electrode material.

[0011] Preferably, the mass volume ratio of the waste lithium manganese oxide positive electrode material and sulfuric acid is 2-3 g:15-25 mL, wherein the concentration of sulfuric acid is 1 mol / L.

[0012] Preferably, in step (1), the temperature of the hydrothermal reaction is 100-200° C., and the time of the hydrothermal reaction is 10-30 h.

[0013] Preferably, in step (2), the molar ratio of manganese ions to ammonium bicarbonate in the washing liquid is 1:1-2.

[0014] Preferably, in step (2), the reaction temperature is 20-30° C., and the reaction time is 5-10.

[0015] Preferably, in step (3), the molar ratio of manganese dioxide, lithium sulfate and lithium hydroxide monohydrate is 2:0.5-1.5:1-1.1.

[0016] Preferably, in step (3), the sintering and tempering treatments are carried out in an oxygen atmosphere.

[0017] Preferably, in step (3), the heating rate during sintering is 1-3°C / min, the temperature is 800-900°C, and the holding time is 10-14h.

[0018] Preferably, in step (3), the tempering treatment is first carried out at 60-100°C for 4-6 hours, and then the temperature is increased to 700-800°C for 5-6 hours, with a heating rate of 1-3°C / min.

[0019] Beneficial effects of the present invention:

[0020] (1) The recycling method provided by the present invention has simple process and low cost, and is suitable for industrial production.

[0021] (2) The present invention can obtain manganese dioxide, spherical manganese carbonate and lithium sulfate by regulating the reaction temperature and reaction time, thereby achieving effective recovery of manganese and lithium.

[0022] (3) The present invention uses recycled manganese and lithium and adds lithium hydroxide monohydrate to re-produce lithium manganate positive electrode material, and the lithium manganate positive electrode material has excellent electrochemical properties.

[0023] (4) The recycling method of waste lithium manganese oxide cathode materials provided by the present invention can achieve resource recycling and reduce environmental pollution. In addition, the recycling method provided by the present invention has low requirements for synthesis equipment, is simple to operate, has no special requirements for production process, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is an XRD pattern of manganese dioxide obtained under different hydrothermal reaction conditions in Examples 1 to 4;

[0025] FIG2 is a SEM image of manganese dioxide obtained under different hydrothermal reaction conditions in Examples 1 to 4;

[0026] FIG3 is a SEM image of manganese carbonate obtained in Example 4;

[0027] FIG4 is an XRD pattern of the recovered lithium manganate positive electrode material of Example 4;

[0028] FIG5 is a graph showing the electrochemical performance of the recovered lithium manganese oxide positive electrode material of Example 4. DETAILED DESCRIPTION

[0029] The present invention provides a method for recycling waste lithium manganese oxide positive electrode materials, comprising the following steps:

[0030] (1) mixing waste lithium manganate positive electrode material and sulfuric acid and performing a hydrothermal reaction to obtain manganese dioxide and a washing solution;

[0031] (2) reacting the washing liquid from step (1) with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate;

[0032] (3) The manganese dioxide obtained in step (1) and the lithium sulfate and lithium hydroxide monohydrate obtained in step (2) are mixed and then sintered, washed and tempered in sequence to obtain a recovered lithium manganate positive electrode material.

[0033] In the present invention, the mass volume ratio of the waste lithium manganate positive electrode material and sulfuric acid is 2-3g:15-25mL, preferably 2.2-2.8g:18-22mL, and more preferably 2.715g:20mL; wherein the concentration of sulfuric acid is 1mol / L.

[0034] In the present invention, the waste lithium manganate positive electrode material and sulfuric acid are preferably mixed under stirring conditions, wherein the stirring speed is 800-1000 rpm, preferably 850-950 rpm, and more preferably 900 rpm; the stirring time is 0.5-1 h, preferably 0.5 h.

[0035] In the present invention, in step (1), the temperature of the hydrothermal reaction is 100-200°C, preferably 120-190°C, and more preferably 160-180°C; the time of the hydrothermal reaction is 10-30h, preferably 12-28h, and more preferably 14-24h.

[0036] In the present invention, in step (2), the molar ratio of manganese ions to ammonium bicarbonate in the washing solution is 1:1-2, preferably 1:1-1.5, and more preferably 1:1.

[0037] In the present invention, in step (2), the reaction temperature is 20-30°C, preferably 22-28°C, and more preferably 25°C; the reaction time is 5-10h, preferably 6-9h, and more preferably 7-8h.

[0038] In the present invention, in step (3), the molar ratio of manganese dioxide, lithium sulfate and lithium hydroxide monohydrate is 2:0.5-1.5:1-1.1, preferably 2:0.6-1.2:1.02-1.08, and more preferably 2:0.8-1.0:1-1.05.

[0039] In the present invention, in the step (3), the sintering treatment and the tempering treatment are carried out in an oxygen atmosphere.

[0040] In the present invention, in step (3), the heating rate during the sintering treatment is 1-3°C / min, preferably 2°C / min; the temperature is 800-900°C, preferably 820-880°C, and more preferably 850°C; the holding time is 10-14h, preferably 11-13h, and more preferably 12h.

[0041] In the present invention, in step (3), during the tempering treatment, the temperature is first kept at 60-100°C for 4-6 hours, preferably at 65-95°C for 4.5-5.5 hours, and more preferably at 70-80°C for 5 hours; then the temperature is raised to 700-800°C for 4-6 hours, preferably at 720-780°C for 4.5-5.5 hours, and more preferably at 750°C for 5 hours; the heating rate is 1-3°C / min, preferably 2°C / min.

[0042] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] 2g of waste lithium manganese oxide positive electrode material was mixed with 15mL of sulfuric acid at a concentration of 1mol / L. After stirring at 850rpm for 0.5h, the mixture was transferred to a reactor for a hydrothermal reaction at a temperature of 100°C for 10h. After the hydrothermal reaction, the black precipitate was washed with deionized water to obtain manganese dioxide and a washing liquid. The manganese dioxide was dried at 80°C for 24h. The washing liquid was tested for the concentration of Mn ions using ICP. Then, ammonium bicarbonate was added to the washing liquid at a molar ratio of manganese ions to ammonium bicarbonate of 1:1 to react at a temperature of 25°C for 5h to obtain a manganese carbonate and lithium sulfate solution. The manganese carbonate was dried at 80°C for 24h, and the lithium sulfate solution was evaporated and crystallized at 120°C to obtain lithium sulfate.

[0045] Manganese dioxide, lithium sulfate and lithium hydroxide monohydrate are mixed in a molar ratio of 2:0.8:1.05 and sintered in an oxygen atmosphere at a heating rate of 2°C / min, a sintering temperature of 850°C, and a holding time of 12 hours. The sintered product is then washed with warm water and tempered at a heating rate of 3°C / min. The mixture is first kept at 80°C for 5 hours and then heated to 750°C for 5 hours to obtain a recovered lithium manganate positive electrode material.

[0046] Example 2

[0047] 3g of waste lithium manganese oxide positive electrode material was mixed with 25mL of sulfuric acid at a concentration of 1mol / L. After stirring at 900rpm for 1h, the mixture was transferred to a reactor for a hydrothermal reaction at a temperature of 140°C for 16h. After the hydrothermal reaction, the black precipitate was washed with deionized water to obtain manganese dioxide and a washing solution. The washing solution was tested for the concentration of Mn ions using ICP. Ammonium bicarbonate was then added to the washing solution at a molar ratio of manganese ions to ammonium bicarbonate of 1:1.05 for reaction at a temperature of 28°C for 7h to obtain a manganese carbonate and lithium sulfate solution. The manganese carbonate was dried at 80°C for 24h, and the lithium sulfate solution was evaporated and crystallized at 120°C to obtain lithium sulfate.

[0048] Manganese dioxide, lithium sulfate and lithium hydroxide monohydrate are mixed in a molar ratio of 2:1:1.03 and sintered in an oxygen atmosphere at a heating rate of 1°C / min, a sintering temperature of 800°C and a sintering time of 14 hours. The sintered product is then washed with warm water and tempered at a heating rate of 2°C / min. The mixture is first kept at 100°C for 4 hours and then heated to 800°C for 4 hours to obtain a recovered lithium manganate positive electrode material.

[0049] Example 3

[0050] 2.715g of waste lithium manganese oxide positive electrode material was mixed with 20mL of sulfuric acid at a concentration of 1mol / L. After stirring at 880rpm for 0.5h, the mixture was transferred to a reactor for hydrothermal reaction at a temperature of 160°C for 20h. After the hydrothermal reaction, the black precipitate was washed with deionized water to obtain manganese dioxide and a washing solution. The washing solution was tested for the concentration of Mn ions using ICP. Ammonium bicarbonate was then added to the washing solution at a molar ratio of manganese ions to ammonium bicarbonate of 1:1.07 to react at a temperature of 22°C for 8h to obtain a manganese carbonate and lithium sulfate solution. The manganese carbonate was dried at 80°C for 24h, and the lithium sulfate solution was evaporated and crystallized at 120°C to obtain lithium sulfate.

[0051] Manganese dioxide, lithium sulfate and lithium hydroxide monohydrate are mixed in a molar ratio of 2:0.5:1.08 and sintered in an oxygen atmosphere at a heating rate of 3°C / min, a sintering temperature of 900°C and a time of 10 hours. The sintered product is then washed with warm water and tempered at a heating rate of 1°C / min. The mixture is first kept at 60°C for 6 hours and then heated to 700°C for 6 hours to obtain a recovered lithium manganate positive electrode material.

[0052] Example 4

[0053] 2.715g of waste lithium manganese oxide positive electrode material was mixed with 20mL of sulfuric acid at a concentration of 1mol / L. After stirring at 1000rpm for 0.5h, the mixture was transferred to a reactor for hydrothermal reaction at a temperature of 200°C for 24h. After the hydrothermal reaction, the black precipitate was washed with deionized water to obtain manganese dioxide and a washing solution. The washing solution was tested for the concentration of Mn ions using ICP. Then, ammonium bicarbonate was added to the washing solution at a molar ratio of manganese ions to ammonium bicarbonate of 1:1 to react at a temperature of 25°C for 10h to obtain a manganese carbonate and lithium sulfate solution. The manganese carbonate was dried at 80°C for 24h, and the lithium sulfate solution was evaporated and crystallized at 120°C to obtain lithium sulfate.

[0054] Manganese dioxide, lithium sulfate and lithium hydroxide monohydrate are mixed in a molar ratio of 2:0.8:1.05 and sintered in an oxygen atmosphere at a heating rate of 2°C / min, a sintering temperature of 850°C, and a sintering time of 12 hours. The sintered product is then washed with warm water and tempered at a heating rate of 3°C / min. The mixture is first kept at 80°C for 5 hours and then heated to 750°C for 5 hours to obtain a recovered lithium manganate positive electrode material.

[0055] FIG1 shows the XRD patterns of manganese dioxide obtained under different hydrothermal reaction conditions in Examples 1 to 4. As can be seen from FIG1 , the obtained manganese dioxide has no secondary phase and impurity peaks, and all diffraction peaks point to the manganese dioxide standard card (PDF#72-1984), indicating that the obtained manganese dioxide is a standard manganese dioxide material.

[0056] FIG2 is an SEM image of manganese dioxide obtained under different hydrothermal reaction conditions in Examples 1 to 4. As can be seen from FIG2 , as the hydrothermal reaction temperature increases and the hydrothermal reaction time prolongs, the aggregation of manganese dioxide gradually decreases and a rod-like structure is formed.

[0057] FIG3 is a SEM image of the manganese carbonate obtained in Example 4. It can be seen from FIG3 that the obtained manganese carbonate is spherical.

[0058] FIG4 is an XRD pattern of the recovered lithium manganese oxide positive electrode material of Example 4. As can be seen from FIG4 , the recovered lithium manganese oxide positive electrode material does not have the generation of secondary phases and impurity peaks, and all diffraction peaks point to the spinel LiMn2O4 standard card (PDF#35-0782) and belong to the Fd-3m space group, which is a standard lithium manganese oxide positive electrode material.

[0059] FIG5 is an electrochemical performance diagram of the recovered lithium manganese oxide positive electrode material of Example 4. It can be seen from FIG5 that the lithium manganese oxide positive electrode material prepared by the molten salt method has a high initial discharge specific capacity of 114.3 mAh g -1 , the cycle retention rate is 97.1%.

[0060] As can be seen from the above examples, the present invention provides a method for recycling waste lithium manganese oxide positive electrode materials. The method first mixes the waste lithium manganese oxide positive electrode materials with sulfuric acid and then conducts a hydrothermal reaction to produce manganese dioxide and a washing solution. The washing solution is then reacted with ammonium bicarbonate to produce manganese carbonate and lithium sulfate. Finally, the manganese dioxide, lithium sulfate, and lithium hydroxide monohydrate are mixed and sequentially sintered, washed, and tempered to obtain the recovered lithium manganese oxide positive electrode material. By regulating the reaction temperature and reaction time, the present invention can produce manganese dioxide, spherical manganese carbonate, and lithium sulfate, achieving efficient recovery of manganese and lithium. The recovered manganese and lithium can be re-produced into lithium manganese oxide positive electrode material by adding lithium hydroxide monohydrate. The lithium manganese oxide positive electrode material exhibits excellent electrochemical properties.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for recycling waste lithium manganese oxide positive electrode materials, characterized in that: The steps include: (1) mixing waste lithium manganate positive electrode material and sulfuric acid and performing a hydrothermal reaction to obtain manganese dioxide and a washing liquid; (2) reacting the washing liquid from step (1) with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate; (3) The manganese dioxide obtained in step (1) and the lithium sulfate and lithium hydroxide monohydrate obtained in step (2) are mixed and then sintered, washed and tempered in sequence to obtain a recovered lithium manganate positive electrode material.

2. The recycling method according to claim 1, characterized in that: The mass volume ratio of the waste lithium manganate positive electrode material and sulfuric acid is 2-3 g:15-25 mL, wherein the concentration of the sulfuric acid is 1 mol / L.

3. The recycling method according to claim 1 or 2, characterized in that: In the step (1), the temperature of the hydrothermal reaction is 100 to 200° C., and the time of the hydrothermal reaction is 10 to 30 hours.

4. The recycling method according to claim 3, characterized in that: In the step (2), the molar ratio of manganese ions to ammonium bicarbonate in the washing liquid is 1:1-2.

5. The recycling method according to claim 2 or 4, characterized in that: In the step (2), the reaction temperature is 20 to 30° C. and the reaction time is 5 to 10 hours.

6. The recycling method according to claim 5, characterized in that: In the step (3), the molar ratio of manganese dioxide, lithium sulfate and lithium hydroxide monohydrate is 2:0.5-1.5:1-1.

1.

7. The recycling method according to claim 1, 4 or 6, characterized in that: In the step (3), the sintering treatment and the tempering treatment are carried out in an oxygen atmosphere.

8. The recycling method according to claim 7, characterized in that: In the step (3), the heating rate during the sintering treatment is 1-3°C / min, the temperature is 800-900°C, and the insulation time is 10-14h.

9. The recycling method according to claim 6 or 8, characterized in that: In the step (3), during the tempering treatment, the temperature is first kept at 60-100° C. for 4-6 hours, and then the temperature is increased to 700-800° C. and kept for 4-6 hours, with a heating rate of 1-3° C. / min.

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