A method for recycling waste lithium manganese oxide cathode materials

Abstract

The present invention provides a method for recycling waste lithium manganese oxide cathode materials, belonging to the technical field of recycling waste lithium manganese oxide cathode materials. First, the waste lithium manganese oxide cathode materials are mixed with sulfuric acid and then subjected to a hydrothermal reaction to obtain manganese dioxide and a washing solution; then the washing solution reacts with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate; finally, manganese dioxide, lithium sulfate and lithium hydroxide monohydrate are mixed and sequentially subjected to sintering treatment, washing and tempering treatment to obtain the recycled lithium manganese oxide cathode materials. By regulating the reaction temperature and reaction time, manganese dioxide, spherical manganese carbonate and lithium sulfate can be obtained in the present invention, realizing the effective recovery of manganese and lithium. With the recovered manganese and lithium, adding lithium hydroxide monohydrate can re-prepare the lithium manganese oxide cathode materials, and the lithium manganese oxide cathode materials have excellent electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling of waste lithium manganese oxide cathode materials, and particularly relates to a method for recycling waste lithium manganese oxide cathode materials. Background Art

[0002] With the increase in the service time of lithium batteries, the material structure will gradually be damaged and the electrochemical performance will decay. In recent years, a large number of waste lithium-ion batteries have been generated. Lithium-ion batteries usually consist of metal / metal oxides, organic chemicals, metal casings, etc. If waste lithium-ion batteries are not properly treated, they will cause serious damage to human health and the environment. At the same time, the recycling of waste lithium-ion batteries has huge economic benefits. Waste lithium-ion batteries can be regarded as rich ores containing metals such as lithium, nickel, cobalt, and manganese. From the perspective of environmental protection and resource regeneration, waste lithium-ion batteries have huge economic benefits and environmental protection value.

[0003] Currently, the research on the recycling of waste lithium-ion batteries mainly falls into the following three processes: pyrometallurgical process, hydrometallurgical process, and biohydrometallurgical process. The pyrometallurgical process mainly burns off the adhesives and carbon in the battery components through high-temperature treatment to separate the active substances. The pyrometallurgical process is simple and easy to implement, but has disadvantages such as high energy consumption and generation of waste gas. Biohydrometallurgy selectively extracts metal elements such as manganese, cobalt, lithium, and nickel through the metabolic process of biological fungi. However, biohydrometallurgy is sensitive to metal concentration, temperature, and other external factors, and the leaching rate is not high, which requires continuous research and improvement. Hydrometallurgy is considered an effective method for recycling waste lithium-ion batteries. The key part of the hydrometallurgical process is the leaching process. Through the synergistic effect of acids (HCl, H2SO4, HNO3) and reducing agents (H2O2), the valence states of transition metals are reduced, and effective leaching of transition metals is achieved. The effectiveness of H2O2 as a reducing agent is beyond doubt, but H2O2 has disadvantages such as poor stability, easy explosion, and high danger. It can be seen that various problems exist 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 cathode materials with simple process and convenient operation. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for recycling waste lithium manganese oxide cathode materials to solve the technical problems of complex process, high energy consumption, generation of waste gas, and low leaching rate existing in the recycling process of waste lithium manganese oxide cathode materials in the prior art.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for recycling waste lithium manganese oxide cathode materials, including the following steps:

[0007] (1) Mix the waste lithium manganese oxide cathode material with sulfuric acid and carry out a hydrothermal reaction to obtain manganese dioxide and a washing solution;

[0008] (2) React the washing solution from step (1) with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate;

[0009] (3) Mix the manganese dioxide from step (1), the lithium sulfate from step (2), and lithium hydroxide monohydrate, and successively carry out sintering treatment, washing, and tempering treatment to obtain the recycled lithium manganese oxide cathode material.

[0010] Preferably, the mass-volume ratio of the waste lithium manganese oxide cathode material to sulfuric acid is 2-3 g: 15-25 mL, and the concentration of sulfuric acid is 1 mol / L.

[0011] 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.

[0012] Preferably, in step (2), the molar ratio of manganese ions to ammonium bicarbonate in the washing solution is 1:1-2.

[0013] Preferably, in step (2), the reaction temperature is 20-30 °C, and the reaction time is 5-10.

[0014] 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.

[0015] Preferably, in step (3), the sintering treatment and the tempering treatment are carried out in an oxygen atmosphere.

[0016] Preferably, in step (3), the heating rate during the sintering treatment is 1-3 °C / min, the temperature is 800-900 °C, and the holding time is 10-14 h.

[0017] Preferably, in step (3), during the tempering treatment, first hold at 60-100 °C for 4-6 h, then raise the temperature to 700-800 °C and hold for 5-6 h, and the heating rate is 1-3 °C / min.

[0018] Advantages of the present invention:

[0019] (1) The recycling method provided by the present invention has a simple process and low cost, and is suitable for industrial production.

[0020] (2) By regulating the reaction temperature and reaction time, the present invention can obtain manganese dioxide, spherical manganese carbonate, and lithium sulfate, realizing the effective recovery of manganese and lithium.

[0021] (3) The present invention uses recycled manganese and lithium, and by adding lithium hydroxide monohydrate, the lithium manganese oxide cathode material can be re-prepared, and the lithium manganese oxide cathode material has excellent electrochemical performance.

[0022] (4) The recycling method of the waste lithium manganese oxide cathode material provided by the present invention can realize the recycling of resources and reduce environmental pollution. Moreover, the recycling method provided by the present invention has low requirements for synthesis equipment, is simple to operate, has no special requirements for the production process, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD patterns of manganese dioxide obtained in Examples 1 to 4 under different hydrothermal reaction conditions;

[0024] Figure 2 SEM images of manganese dioxide obtained in Examples 1 to 4 under different hydrothermal reaction conditions;

[0025] Figure 3 SEM image of manganese carbonate prepared in Example 4;

[0026] Figure 4 XRD pattern of the recycled lithium manganese oxide cathode material in Example 4;

[0027] Figure 5 Electrochemical performance diagram of the recycled lithium manganese oxide cathode material in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention provides a recycling method for waste lithium manganese oxide cathode materials, which includes the following steps:

[0029] (1) Mix the waste lithium manganese oxide cathode material and sulfuric acid and carry out hydrothermal reaction to obtain manganese dioxide and a washing solution;

[0030] (2) React the washing solution in step (1) with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate;

[0031] (3) Mix the manganese dioxide in step (1) with the lithium sulfate and lithium hydroxide monohydrate in step (2), and successively carry out sintering treatment, washing and tempering treatment to obtain the recycled lithium manganese oxide cathode material.

[0032] In the present invention, the mass-volume ratio of the waste lithium manganese oxide cathode material to sulfuric acid is 2-3 g: 15-25 mL, preferably 2.2-2.8 g: 18-22 mL, and further preferably 2.715 g: 20 mL; wherein the concentration of sulfuric acid is 1 mol / L.

[0033] In the present invention, when the waste lithium manganese oxide cathode material is mixed with sulfuric acid, it is preferably carried out under stirring conditions, where 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.

[0034] In the present invention, in the step (1), the hydrothermal reaction temperature is 100 - 200 °C, preferably 120 - 190 °C, and more preferably 160 - 180 °C; the hydrothermal reaction time is 10 - 30 h, preferably 12 - 28 h, and more preferably 14 - 24 h.

[0035] In the present invention, in the step (2), the molar ratio of manganese ions to ammonium bicarbonate in the washing liquid is 1:1 - 2, preferably 1:1 - 1.5, and more preferably 1:1.

[0036] In the present invention, in the step (2), the reaction temperature is 20 - 30 °C, preferably 22 - 28 °C, and more preferably 25 °C; the reaction time is 5 - 10 h, preferably 6 -9 h, and more preferably 7 - 8 h.

[0037] In the present invention, 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, preferably 2:0.6 - 1.2:1.02 - 1.08, and more preferably 2:0.8 - 1.0:1 - 1.05.

[0038] In the present invention, in the step (3), the sintering treatment and tempering treatment are carried out in an oxygen atmosphere.

[0039] In the present invention, in the step (3), during the sintering treatment, the heating rate 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 - 14 h, preferably 11 - 13 h, and more preferably 12 h.

[0040] In the present invention, in the step (3), during the tempering treatment, first, it is held at 60 - 100 °C for 4 - 6 h, preferably held at 65 - 95 °C for 4.5 - 5.5 h, and more preferably held at 70 - 80 °C for 5 h; then it is heated to 700 - 800 °C and held for 4 - 6 h, preferably heated to 720 - 780 °C and held for 4.5 - 5.5 h, and more preferably heated to 750 °C and held for 5 h; the heating rate is 1 - 3 °C / min, preferably 2 °C / min.

[0041] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0042] Example 1

[0043] Mix 2 g of waste lithium manganese oxide cathode material with 15 mL of sulfuric acid, where the concentration of sulfuric acid is 1 mol / L. Stir for 0.5 h at a rotation speed of 850 rpm, then transfer to a reaction kettle for hydrothermal reaction. The temperature of the hydrothermal reaction is 100 °C, and the time of the hydrothermal reaction is 10 h. After the hydrothermal reaction is completed, wash the black precipitate with deionized water to obtain manganese dioxide and washing solution. Dry the manganese dioxide at 80 °C for 24 h. Test the concentration of Mn ions in the washing solution by ICP, and then add ammonium bicarbonate to the washing solution for reaction according to the molar ratio of manganese ions to ammonium bicarbonate of 1:1. The reaction temperature is 25 °C, and the reaction time is 5 h to obtain manganese carbonate and lithium sulfate solution. Dry the manganese carbonate at 80 °C for 24 h, and evaporate and crystallize the lithium sulfate solution at 120 °C to obtain lithium sulfate.

[0044] Mix manganese dioxide, lithium sulfate and lithium hydroxide monohydrate according to the molar ratio of 2:0.8:1.05, and then carry out sintering treatment in an oxygen atmosphere. The heating rate is 2 °C / min, the sintering temperature is 850 °C, and the holding time is 12 h. Then wash the sintered product with warm water and then carry out tempering treatment. The heating rate of the tempering treatment is 3 °C / min. First, hold at 80 °C for 5 h, and then raise the temperature to 750 °C and hold for 5 h to obtain the recycled lithium manganese oxide cathode material.

[0045] Example 2

[0046] Mix 3 g of waste lithium manganese oxide cathode material with 25 mL of sulfuric acid, where the concentration of sulfuric acid is 1 mol / L. Stir for 1 h at a rotation speed of 900 rpm, then transfer to a reaction kettle for hydrothermal reaction. The temperature of the hydrothermal reaction is 140 °C, and the time of the hydrothermal reaction is 16 h. After the hydrothermal reaction is completed, wash the black precipitate with deionized water to obtain manganese dioxide and washing solution. Test the concentration of Mn ions in the washing solution by ICP, and then add ammonium bicarbonate to the washing solution for reaction according to the molar ratio of manganese ions to ammonium bicarbonate of 1:1.05. The reaction temperature is 28, and the reaction time is 7 h to obtain manganese carbonate and lithium sulfate solution. Dry the manganese carbonate at 80 °C for 24 h, and evaporate and crystallize the lithium sulfate solution at 120 °C to obtain lithium sulfate.

[0047] Mix manganese dioxide, lithium sulfate, and lithium hydroxide monohydrate in a molar ratio of 2:1:1.03, and then conduct a sintering treatment in an oxygen atmosphere. The heating rate is 1 °C / min, the sintering temperature is 800 °C, and the time is 14 h. Then, wash the sintered product with warm water and conduct a tempering treatment. The heating rate of the tempering treatment is 2 °C / min. First, hold at 100 °C for 4 h, and then raise the temperature to 800 °C and hold for 4 h to obtain the recycled lithium manganese oxide cathode material.

[0048] Example 3

[0049] Mix 2.715 g of waste lithium manganese oxide cathode material and 20 mL of sulfuric acid, where the concentration of sulfuric acid is 1 mol / L. Stir for 0.5 h at a rotation speed of 880 rpm and then transfer to a reaction kettle for hydrothermal reaction. The temperature of the hydrothermal reaction is 160 °C, and the time is 20 h. After the hydrothermal reaction is completed, wash the black precipitate with deionized water to obtain manganese dioxide and the washing solution. Test the concentration of Mn ions in the washing solution using ICP, and then add ammonium bicarbonate to the washing solution for reaction according to the molar ratio of manganese ions to ammonium bicarbonate of 1:1.07. The reaction temperature is 22 °C, and the reaction time is 8 h to obtain manganese carbonate and lithium sulfate solution. Manganese carbonate is dried at 80 °C for 24 h, and lithium sulfate solution is evaporated and crystallized at 120 °C to obtain lithium sulfate.

[0050] Mix manganese dioxide, lithium sulfate, and lithium hydroxide monohydrate in a molar ratio of 2:0.5:1.08, and then conduct a sintering treatment in an oxygen atmosphere. The heating rate is 3 °C / min, the sintering temperature is 900 °C, and the time is 10 h. Then, wash the sintered product with warm water and conduct a tempering treatment. The heating rate of the tempering treatment is 1 °C / min. First, hold at 60 °C for 6 h, and then raise the temperature to 700 °C and hold for 6 h to obtain the recycled lithium manganese oxide cathode material.

[0051] Example 4

[0052] Mix 2.715 g of waste lithium manganese oxide cathode material and 20 mL of sulfuric acid, where the concentration of sulfuric acid is 1 mol / L. Stir for 0.5 h at a rotation speed of 1000 rpm and then transfer to a reaction kettle for hydrothermal reaction. The temperature of the hydrothermal reaction is 200 °C, and the time is 24 h. After the hydrothermal reaction is completed, wash the black precipitate with deionized water to obtain manganese dioxide and the washing solution. Test the concentration of Mn ions in the washing solution using ICP, and then add ammonium bicarbonate to the washing solution for reaction according to the molar ratio of manganese ions to ammonium bicarbonate of 1:1. The reaction temperature is 25 °C, and the reaction time is 10 h to obtain manganese carbonate and lithium sulfate solution. Manganese carbonate is dried at 80 °C for 24 h, and lithium sulfate solution is evaporated and crystallized at 120 °C to obtain lithium sulfate.

[0053] Mix manganese dioxide, lithium sulfate and lithium hydroxide monohydrate in a molar ratio of 2:0.8:1.05, and then carry out sintering treatment in an oxygen atmosphere. The heating rate is 2 °C / min, the sintering temperature is 850 °C, and the time is 12 h. Then wash the sintered product with warm water and then carry out tempering treatment. The heating rate of the tempering treatment is 3 °C / min. First, keep it at 80 °C for 5 h, and then raise the temperature to 750 °C and keep it for 5 h to obtain the recycled lithium manganese oxide cathode material.

[0054] Figure 1 XRD patterns of manganese dioxide obtained in Examples 1 to 4 under different hydrothermal reaction conditions. From Figure 1 It can be seen that no secondary phase and impurity peaks are generated in the obtained manganese dioxide, and all diffraction peaks point to the manganese dioxide standard card (PDF#72-1984), which is a standard manganese dioxide material.

[0055] Figure 2 SEM images of manganese dioxide obtained in Examples 1 to 4 under different hydrothermal reaction conditions. From Figure 2 It can be seen that with the increase of the hydrothermal reaction temperature and the extension of the hydrothermal reaction time, the aggregation phenomenon of manganese dioxide gradually decreases, showing a rod-like structure.

[0056] Figure 3 SEM image of manganese carbonate prepared in Example 4. From Figure 3 It can be seen that the obtained manganese carbonate is spherical manganese carbonate.

[0057] Figure 4 XRD pattern of the recycled lithium manganese oxide cathode material in Example 4. From Figure 4 It can be seen that no secondary phase and impurity peaks are generated in the recycled lithium manganese oxide cathode material, and all diffraction peaks point to the spinel LiMn2O4 standard card (PDF#35-0782), which all belong to the Fd-3m space group, and it is a standard lithium manganese oxide cathode material.

[0058] Figure 5 Electrochemical performance diagram of the recycled lithium manganese oxide cathode material in Example 4. From Figure 5 It can be seen that the lithium manganese oxide cathode material prepared by the molten salt method has a relatively high initial discharge specific capacity of 114.3 mAh·g -1 , and the cycle retention rate is 97.1%.

[0059] As can be seen from the above embodiments, the present invention provides a method for recycling waste lithium manganese oxide cathode materials. First, the waste lithium manganese oxide cathode materials are mixed with sulfuric acid and then subjected to a hydrothermal reaction to obtain manganese dioxide and a washing solution. Then, the washing solution is reacted with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate. Finally, manganese dioxide, lithium sulfate, and lithium hydroxide monohydrate are mixed and sequentially subjected to sintering treatment, washing, and tempering treatment to obtain the recycled lithium manganese oxide cathode materials. By controlling the reaction temperature and reaction time, the present invention can obtain manganese dioxide, spherical manganese carbonate, and lithium sulfate, realizing the effective recovery of manganese and lithium. With the recovered manganese and lithium, adding lithium hydroxide monohydrate can re-prepare the lithium manganese oxide cathode materials, and the lithium manganese oxide cathode materials have excellent electrochemical properties.

[0060] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for recycling waste lithium manganese oxide cathode materials, characterized in that, It includes the following steps: (1) Mix the waste lithium manganese oxide cathode material and sulfuric acid and then carry out a hydrothermal reaction to obtain manganese dioxide and a washing solution; (2) React the washing solution in step (1) with ammonium bicarbonate to obtain manganese carbonate and lithium sulfate; (3) Mix the manganese dioxide in step (1), the lithium sulfate in step (2), and lithium hydroxide monohydrate, and then successively carry out sintering treatment, washing, and tempering treatment to obtain the recycled lithium manganese oxide cathode material.

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

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

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

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

6. The recycling method according to claim 5, characterized in that In 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 or 4 or 6, characterized in that, In 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 step (3), the heating rate during the sintering treatment is 1-3 °C / min, the temperature is 800-900 °C, and the holding time is 10-14 h.

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

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