A method for regenerating the cathode material of sodium batteries by using waste lithium manganate

Abstract

The present invention provides a method for separating lithium from the positive electrode of waste lithium manganese oxide batteries and regenerating the positive electrode material of sodium-ion batteries. Using the waste lithium manganese oxide positive electrode material as the raw material, the carbon thermal reduction of the positive electrode material, the sodium carbonate leaching of the reduction product, the acid leaching of the leaching residue, and the preparation of the precursor by the sol-gel method are carried out in sequence, and finally the positive electrode material of the sodium-ion battery is obtained by calcination; the present invention makes full use of the valuable metal components in the waste lithium manganese oxide positive electrode material, while quantitatively separating lithium, and uses the doping modification of lithium on the positive electrode material of the sodium-ion battery to prepare a high-performance positive electrode material, improving the value of the recycled product.

Description

Technical Field

[0001] The present invention relates to the field of recycling of waste lithium batteries, and particularly to a method for separating lithium from waste lithium manganese oxide cathode materials and regenerating a sodium-ion battery cathode material with a P2 layered structure. Background Art

[0002] With the gradual scrapping of early-produced lithium-ion batteries, the number of waste lithium-ion batteries has been increasing year by year. How to efficiently treat and recycle the electrode materials of waste lithium-ion batteries has become a research hotspot worldwide. Most of the research on the recycling and regeneration direction of the cathode material lithium manganese oxide focuses on the separation and purification of lithium and manganese metals. Most of the traditional recycling methods for the cathode materials of lithium manganese oxide batteries are wet leaching methods, that is, waste lithium manganese oxide is leached in an acidic reduction system, then manganese is precipitated by an alkali method, and finally lithium is selectively precipitated using the difference in solubility to be recycled into lithium and manganese metal salts for other fields. At present, there are also some improved studies on the separation and recycling of traditional methods. For example, CN109207725B discloses a method and system for recycling lithium and manganese from waste lithium manganese oxide batteries. This method disassembles waste lithium manganese oxide to obtain the cathode material, dissolves it in acid to obtain valuable elements in the cathode sheet, then separates lithium ions from other cations by ultrafiltration, and finally uses a chemical precipitation method to precipitate and separate lithium and manganese to achieve recycling. This method has advanced separation technology, good separation effect, and physical separation also reduces the introduction of impurity ions and lowers the recycling cost, but the income of the recycled products is relatively low, the recycling process is relatively long, and the investment cost of equipment is relatively high, and the overall recycling efficiency needs to be further improved.

[0003] To solve this problem, directly repairing the structure or regenerating the materials of waste lithium manganese oxide batteries to prepare new battery cathode materials has become a new research idea. This mode can reduce the battery recycling process, save costs, and increase the recycling value. Sodium-ion batteries have good research prospects due to their excellent fast charging performance, good low-temperature performance, good safety performance, low cost, and electrochemical properties similar to those of lithium-ion batteries, and have become a research hotspot in recent years, and are reasonable reproduction product targets.

[0004] Starting from the perspectives of material value addition and resource utilization, the present invention uses a sodium carbonate solution to control the lithium leaching rate, thereby realizing the quantitative doping of lithium during the material regeneration process. The partial substitution of lithium for transition metals in the sodium-ion cathode material inhibits the transformation of the crystal structure from P2 to O2, maintains the structural stability, and to a certain extent improves the specific capacity of the material. Summary of the Invention

[0005] Aiming at the problems of low recycling value and poor efficiency of waste lithium manganese oxide electrode materials, the present invention proposes a method for separating lithium from waste lithium manganese oxide cathode materials and regenerating cathode materials for sodium-ion batteries, realizing the quantitative doping of lithium during the material regeneration process. On the basis of being simple and reasonable, the method of the present invention can effectively regenerate cathode materials for sodium-ion batteries with excellent performance in the P2 layered structure.

[0006] To achieve the purpose, the present invention adopts the following technical solutions:

[0007] A method for separating lithium from waste lithium manganese oxide cathode materials and regenerating cathode materials for sodium-ion batteries, comprising the following steps:

[0008] (1) Pretreat the waste lithium manganese oxide battery to obtain the cathode material, and then carry out carbothermal reduction on the cathode material to obtain a mixed powder containing lithium and manganese elements;

[0009] (2) Place the mixed powder obtained in step (1) in a sodium carbonate solution for leaching to quantitatively control the leaching amount of lithium, filter to obtain a lithium-containing leachate and a leaching residue, and further acid-leach the leaching residue with an acid solution to obtain a leachate containing Mn 2+ and Li + ;

[0010] (3) Detect the concentrations of lithium and manganese elements in the leachate containing Mn 2+ and Li + obtained in step (2), fit the cathode material of the target P2 layered structure sodium-ion battery according to the lithium and manganese element concentrations in the leachate, calculate and add the leachate containing Mn 2+ and Li + obtained in step (2) and metal salts of nickel, magnesium and sodium to obtain a mixed solution, and then obtain a precursor of the cathode material of the P2 layered structure sodium-ion battery through the sol-gel method;

[0011] (4) Calcinate the precursor of the cathode material of the P2 layered structure sodium-ion battery obtained in step (3) to obtain the target cathode material of the P2 layered structure sodium-ion battery Na 0.67 Li x Ni y Mn 1-x-y-z Mg z O 2 (0<x≤0.1,0<y<0.2,0<z<0.1).

[0012] Preferably, in step (1), during the carbothermal reduction process, the mass ratio of the cathode material to graphite is 1-10:1, the carbothermal reduction reaction temperature is 600-800 °C, and the carbothermal reduction reaction time is 2-6 h.

[0013] Preferably, in step (2), the mass ratio of the mixed powder to water is 1:10 - 60, the leaching time is 1 - 4 h, and the amount of sodium carbonate added is 100% - 120% of the theoretically added amount.

[0014] Preferably, in step (2), the mass ratio of the mixed powder to water is 1:20 - 40.

[0015] Preferably, in step (2), the type of the acid solution is nitric acid, the amount of nitric acid added in terms of the amount of substance is 5 - 10 times the amount of manganese substance in the leaching residue, the leaching time is 0.5 - 2 h, and the leaching temperature is 40 - 80 °C.

[0016] Preferably, in step (3), in the sol - gel method, the pH of the mixed solution is adjusted to 7 - 8, then a chelating agent is added, and the reaction is carried out at 70 - 90 °C for 6 - 8 h, followed by drying and grinding to obtain a precursor of the cathode material for sodium - ion batteries with a P2 - type layered structure.

[0017] Preferably, in step (3), the chelating agent is selected from one or more of citric acid, EDTA, and sucrose.

[0018] Preferably, in step (4), the calcination is divided into two - stage sintering. The first - stage sintering temperature is 450 - 500 °C, and the sintering time is 4 - 6 h; the second - stage sintering temperature is 700 - 900 °C, and the calcination time is 10 - 12 h. The heating rate for the two - stage calcination is 5 - 10 °C·min -1 。

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The method of the present invention does not require traditional extraction processes and chemical precipitation separation processes. After destroying the spinel structure of lithium manganate by carbothermal reduction, the water solubility of lithium oxide and the slight solubility of lithium carbonate are utilized to achieve the separation of lithium and manganese and the quantitative precipitation of lithium, and finally the effect of lithium doping in the recycled material is achieved. The operation is simple, the recycling steps and requirements are simplified, and no acidic and organic waste liquids are generated during the recycling process. The main component of the final solid - phase residue is carbon, which can still participate in the previous carbothermal reduction step to achieve recycling, and the generation of waste is avoided as much as possible;

[0021] (2) While further simplifying the recycling process, the method of the present invention controls the parameters of sodium carbonate solution leaching to achieve quantitative lithium precipitation, and finally doping and modification are carried out on the prepared cathode material for sodium - ion batteries. By partially substituting lithium for transition metals, the transformation from the P2 phase to the O2 phase is inhibited, the stability of the cathode material for sodium - ion batteries is improved, and good electrochemical performance is achieved. While reducing the recycling cost, the value of the recycled product is further increased, valuable metals are fully utilized, and good recycling benefits are obtained. Description of the Drawings

[0022] Figure 1 is the XRD pattern of the cathode material for sodium-ion batteries, Na 0.67 Li x Ni y Mn 1-x-y-z Mg z O 2 (0 < x ≤ 0.1, 0 < y < 0.2, 0 < z < 0.1);

[0023] Figure 2 is the electrochemical performance graph of the battery assembled with the cathode material for sodium-ion batteries, Na 0.67 Li x Ni y Mn 1-x-y-z Mg z O 2 (0 < x ≤ 0.1, 0 < y < 0.2, 0 < z < 0.1). Detailed implementation manners

[0024] The present invention will be further described below in conjunction with embodiments and the accompanying drawings.

[0025] Embodiment 1

[0026] (1) The waste lithium manganese oxide battery is disassembled to obtain the cathode, and then the cathode material is peeled off from the cathode, crushed and calcined to obtain the cathode material. 5 g of the cathode material and 1 g of graphite are fully mixed by a ball mill at 450 RPM for 1 h. The powder mixed with graphite is sintered in an argon atmosphere at a sintering temperature of 750 °C for 2 h to obtain a mixed powder containing lithium manganese oxide;

[0027] (2) The reduced powder is added to 150 mL of deionized water, and then Na 2 CO 3 with a theoretical calculation amount of 110%, i.e., 24.64 g, is added. After filtration, a lithium-rich leaching solution is obtained. The leaching residue is mixed with 60 mL of 2 mol / L nitric acid and leached at 60 °C for 2 h. After filtration, a solution containing manganese and lithium is obtained.

[0028] (3) By ICP analysis, in the leaching solution, the mass concentrations of Li and Mn are 16.31 mg / L and 2996.95 mg / L respectively. After calculation, the leaching rate of manganese is about 99%. According to the lithium and manganese contents in the leaching solution, Na 0.67 Li 0.1 Ni 0.17 Mn 0.66 Mg 0.07 O 2, Calculate the amount to be supplemented for each element, add the corresponding metal salt to obtain a mixed solution. Subsequently, add 15.86 g of citric acid, adjust the pH to 7 - 8 using ammonia water, heat to 80 °C, and stir until the solution becomes a gel. Dry the gel in an oven at 80 °C for 12 h, and after grinding, obtain the precursor of the cathode material for sodium-ion batteries with a P2 layered structure.

[0029] (4) Subject the precursor of the cathode material for sodium-ion batteries with a P2 layered structure obtained in step (3) to solid-phase sintering in a muffle furnace. The sintering process is divided into two stages. The first stage is sintering at 450 °C for 6 h, and the second stage is sintering at 900 °C for 12 h to obtain the cathode material for sodium-ion batteries with a P2 layered structure.

[0030] Mix the prepared cathode material powder for sodium-ion batteries with a P2 layered structure, super conductive carbon, and polyvinylidene fluoride in a mass ratio of 8:1:1. After adding 0.3 g of NMP and grinding evenly, coat the slurry evenly on an aluminum foil, dry it, and cut it into circular pieces with a diameter of 12 mm. Assemble it in an argon glove box, use a sodium metal sheet as the counter electrode, and Celgard 2300 as the separator to assemble a CR2032 type coin cell. At 25 °C, perform charge-discharge tests at a 1C rate in the voltage range of 2 - 4V. The results are as Figure 2 shown. Its initial capacity is 117.6 mAh·g -1 , After 150 cycles, its discharge specific capacity is still 95.4 mAh·g -1 .

[0031] Example 2

[0032] (1) Disassemble and split a waste lithium manganese oxide battery to obtain the cathode, then peel the cathode material from the cathode, and after crushing and calcining, obtain the cathode material. Mix 4 g of the cathode material with 1 g of graphite thoroughly in a ball mill at 450 RPM for 1 h. Sinter the powder mixed with graphite in an argon atmosphere at a sintering temperature of 700 °C for 3 h to obtain a mixed powder containing lithium manganese oxide;

[0033] (2) Add the reduced powder to 120 mL of deionized water, and then add 110% of the theoretical calculated amount of Na 2 CO 3 , that is, 19.71 g, filter to obtain a lithium-rich leachate. Mix the leaching residue with 50 mL of 2 mol / L nitric acid and leach at 60 °C for 2 h, filter to obtain a solution containing manganese and a small amount of lithium.

[0034] (3) Using ICP analysis, in the leachate, the mass concentrations of Li and Mn are 13.30 mg / L and 2401.53 mg / L respectively. After calculation, the leaching rate of manganese is about 99%. According to the contents of lithium and manganese in the leachate, synthesize Na 0.67 Li0.1 Ni 0.17 Mn 0.66 Mg 0.07 O 2 , calculate the amount of each element to be supplemented, add the corresponding metal salts to obtain a mixed solution. Subsequently, add 12.71 g of citric acid, adjust the pH to 7 - 8 using ammonia water, heat to 80 °C, and stir until the solution becomes a gel. Dry the gel in an oven at 80 °C for 12 h, and after grinding, obtain the precursor of the cathode material for sodium-ion batteries with a P2 layered structure.

[0035] (4) Subject the precursor of the cathode material for sodium-ion batteries with a P2 layered structure obtained in step (3) to solid-phase sintering in a muffle furnace. The sintering process is divided into two stages. The first stage is sintering at 450 °C for 6 h, and the second stage is sintering at 800 °C for 12 h to obtain the cathode material for sodium-ion batteries with a P2 layered structure.

[0036] Mix the prepared cathode material powder for sodium-ion batteries with a P2 layered structure, super conductive carbon, and polyvinylidene fluoride in a mass ratio of 8:1:1. After adding 0.3 g of NMP and grinding evenly, coat the slurry evenly on the aluminum foil, and after drying, cut it into circular pieces with a diameter of 12 mm. Assemble it in an argon glove box, use a sodium metal sheet as the counter electrode, and Celgard 2300 as the separator to assemble a CR2032 type coin cell. At 25 °C, perform charge-discharge tests at a 1C rate in the voltage range of 2 - 4V, and the results are as Figure 2 shown. Its initial capacity is 124.7 mAh·g -1 , and after 150 cycles, its discharge specific capacity is still 96.2 mAh·g -1 .

Claims

1. Method for Separating Lithium from the Positive Electrode of Waste Lithium Manganese Oxide Batteries and Recycling the Positive Electrode Material of Sodium-Ion Batteries, Characterized in that, It includes the following steps: (1) Pretreat the waste lithium manganese oxide battery to obtain the positive electrode material, and then perform carbothermal reduction on the positive electrode material to obtain a mixed powder containing lithium and manganese elements; (2) Place the mixed powder obtained in step (1) in a sodium carbonate solution for leaching to quantitatively control the leaching amount of lithium, filter to obtain a lithium-containing leachate and leaching residue, and further acid-leach the leaching residue with an acid solution to obtain a leachate containing Mn 2+ and Li + ; (3) Detect the concentrations of lithium and manganese elements in the leaching solution containing Mn 2+ and Li + in the leaching solution, fit the cathode material of the sodium-ion battery with the target P2 layered structure according to the element concentrations of lithium and manganese in the leaching solution, calculate and add the leaching solution containing Mn 2+ and Li + obtained in step (2), as well as metal salts of nickel, magnesium and sodium, to obtain a mixed solution, and then prepare a precursor of the cathode material of the sodium-ion battery with the P2 layered structure by the sol-gel method; (4) Calcinate the precursor of the sodium-ion battery cathode material with a P2 layered structure obtained in step (3) to obtain the target sodium-ion battery cathode material with a P2 layered structure, Na 0.67 Li x Ni y Mn 1-x-y-z Mg z O 2 (0 < x ≤ 0.1, 0 < y < 0.2, 0 < z < 0.1).

2. The method for separating lithium from the positive electrode of waste lithium manganese oxide batteries and recycling the positive electrode material of sodium-ion batteries according to claim 1, Characterized in that, In step (1), during the carbothermal reduction process, the mass ratio of graphite to the positive electrode material is 1-10:1, the carbothermal reduction reaction temperature is 600-800 °C, and the carbothermal reduction reaction time is 2-6 h.

3. The method for separating lithium from the positive electrode of waste lithium manganese oxide batteries and recycling the positive electrode material of sodium-ion batteries according to claim 2, Characterized in that, In step (2), the addition amount of sodium carbonate is controlled by the slight solubility of lithium carbonate to quantitatively leach lithium. The mass ratio of the mixed powder to water is 1:10-60, the leaching time is 1-4 h, and the added amount of sodium carbonate is 100%-120% of the theoretical addition amount.

4. The method for separating lithium from the positive electrode of waste lithium manganese oxide batteries and recycling the positive electrode material of sodium-ion batteries according to claim 2 or 3, Characterized in that, In step (2), the mass ratio of the mixed powder to water is 1:20-40.

5. The method for separating lithium from the positive electrode of waste lithium manganese oxide batteries and recycling the positive electrode material of sodium-ion batteries according to claim 1 or 3, Characterized in that, In step (2), the type of acid solution is nitric acid. The amount of nitric acid added is 5-10 times the amount of manganese in the leaching residue. The leaching time is 0.5-2 h, and the leaching temperature is 40-80 °C.

6. The method for separating lithium from the positive electrode of waste lithium manganese oxide batteries and recycling the positive electrode material of sodium-ion batteries according to claim 1, Characterized in that, In step (3), in the sol-gel method, the pH of the mixed solution is adjusted to 7-8, and then a chelating agent is added, and the reaction is carried out at 70-90 °C for 6-8 h, dried, and ground to obtain a precursor of the positive electrode material of the sodium-ion battery with a P2 layered structure.

7. The method for separating lithium from the positive electrode of waste lithium manganese oxide batteries and recycling the positive electrode material of sodium-ion batteries according to claim 6, Characterized in that, In step (3), the chelating agent is selected from one or more of citric acid, EDTA, and sucrose.

8. The method for separating lithium from the positive electrode of waste lithium manganese oxide batteries and recycling the positive electrode material of sodium-ion batteries according to claim 1, Characterized in that, In step (4), the calcination is divided into two-stage sintering. The first-stage sintering temperature is 450-500 °C, and the sintering time is 4-6 h; the second-stage sintering temperature is 700-900 °C, and the calcination time is 10-12 h. The heating rate of the two-stage calcination is 5-10 °C·min.

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