A method for synergistic conversion of ternary lithium-ion battery black powder positive electrode and repair and regeneration of graphite negative electrode

Abstract

This invention relates to a method for the synergistic conversion of ternary lithium-ion battery black powder positive electrode and the repair and regeneration of graphite negative electrode, comprising the following steps: (1) obtaining ternary lithium-ion battery black powder after a pretreatment step of retired ternary lithium-ion batteries; (2) thoroughly mixing the black powder with concentrated sulfuric acid; (3) placing the mixture into a microwave reactor for thorough microwave heat treatment; (4) stirring and leaching the product after microwave heat treatment in an aqueous solution to obtain a water-leached solution containing lithium, nickel, cobalt, and manganese and water-leached graphite slag; the water-leached solution is further processed to obtain nickel sulfate, cobalt sulfate, manganese sulfate, and lithium carbonate products; (5) the water-leached graphite slag obtained in step (4) is thoroughly washed with water and then dried to obtain battery-grade regenerated graphite products. The above method is simple in process, low in energy consumption, and has a high recovery rate of valuable metals, which can realize the deep purification and efficient repair and regeneration of waste graphite, and has good prospects for industrial application.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of solid waste resources and waste battery recycling, and particularly relates to a method for converting ternary lithium battery black powder positive electrodes and repairing and regenerating graphite negative electrodes. BACKGROUND

[0002] Retired lithium batteries are rich in strategic resources such as lithium, nickel, cobalt, copper and graphite, and the content is much higher than that of primary mineral resources. However, the retired lithium batteries also contain toxic substances such as organic matter, fluorine and phosphorus, which may harm the environment. Therefore, efficient and green recovery of strategic resources in retired lithium batteries is crucial.

[0003] Valuable metals such as lithium, nickel, cobalt and manganese in retired lithium batteries are generally leached into solution by reduction acid leaching, and then metal products are obtained by subsequent purification and extraction separation. In the process of reduction acid leaching, a reducing agent needs to be added, and because the structure of ternary materials is relatively stable, a high acid concentration is required, the reagent cost of the leaching process is high, and the leaching efficiency is low. Patent 201510007518.2 proposes a method for recovering metals from lithium nickel manganese oxide waste batteries, which mixes the positive electrode powder of the retired lithium battery with potassium bisulfate in a certain proportion and then roasts it. The roasted product is leached with water. In this method, lithium, nickel, cobalt and manganese in the positive electrode powder are transformed into sulfates, and then the valuable metals can be leached by water leaching. In the process, no reducing agent or inorganic acid needs to be added, but the price of potassium bisulfate is relatively high, and the introduction of potassium ions will adversely affect the subsequent product purification.

[0004] On the other hand, the recovery of waste graphite in retired lithium batteries has also received high attention in recent years. Currently, strong acid is generally used to leach metal impurities, and then high-temperature heat treatment (1500-2500℃) is used to repair the damaged structure. Because the whole process has high acid consumption and high energy consumption, and direct acid leaching cannot achieve deep purification. Patent 201910090383.9 discloses a method for recovering waste graphite containing silicon from lithium batteries, which mixes the graphite waste with concentrated sulfuric acid and then performs a sulfuric acid curing reaction in a muffle furnace at a temperature of about 250℃. After curing, metal impurities are removed by sulfuric acid leaching, and finally vacuum roasting at 1500℃ is performed to obtain regenerated battery graphite. The impurity removal effect of this waste graphite recovery method is acceptable, but the heat treatment temperature is high, the reaction time is long, and the energy consumption is high. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a method for economically and efficiently recovering valuable metals and waste graphite from waste ternary lithium batteries. The method has a simple process, low energy consumption, high valuable metal recovery rate, and can achieve deep purification and efficient repair and regeneration of waste graphite, and has good industrialization prospects.

[0006] A method for the synergistic conversion of ternary lithium-ion battery black powder as a positive electrode and the repair and regeneration of graphite anode, the method comprising: pre-treating retired ternary lithium-ion batteries to obtain ternary lithium-ion battery black powder (a mixed powder of nickel-cobalt-manganese ternary positive electrode and graphite anode); thoroughly mixing the black powder with a certain amount of concentrated sulfuric acid; and then placing the mixture into a microwave reactor for microwave heat treatment to achieve the sulfation transformation of nickel, cobalt, and manganese in the ternary positive electrode material into metal sulfates. The reaction principle can be described by the following formula:

[0007] LiNi x Co y Mn z O2+H2SO4→Li2SO4+NiSO4+CoSO4+MnSO4

[0008] On the other hand, transition metal salts can catalyze graphitization, enabling the graphitization transformation of carbon materials at temperatures around 1000℃. Based on this, in this method, the damaged structures in waste graphite can be graphitized and repaired under the catalytic action of nickel, cobalt, and manganese sulfates. Furthermore, since graphite itself is a strong microwave absorbing material, it can rapidly heat up and generate high-temperature hotspots during microwave heating, which is more conducive to the sulfation reaction and catalytic graphitization.

[0009] After microwave heat treatment, water immersion is used to obtain a water immersion solution containing lithium, nickel, cobalt, and manganese, and water immersion graphite residue. The water immersion solution is recovered to obtain metal sulfate products. The water immersion graphite residue is thoroughly washed and dried to obtain battery-grade recycled graphite.

[0010] A method for the synergistic conversion of ternary lithium-ion battery black powder positive electrode and the repair and regeneration of graphite negative electrode includes the following steps:

[0011] (1) After the retired ternary lithium-ion batteries undergo a pretreatment step, ternary lithium battery black powder is obtained.

[0012] (2) Mix the black powder with a certain amount of concentrated sulfuric acid thoroughly;

[0013] (3) Place the mixture into a microwave reactor for thorough microwave heat treatment;

[0014] (4) The product after microwave heat treatment is stirred and leached in an aqueous solution to obtain an aqueous leaching solution containing lithium, nickel, cobalt and manganese and an aqueous leached graphite residue; the aqueous leaching solution is then subjected to a post-treatment step to obtain nickel sulfate, cobalt sulfate, manganese sulfate and lithium carbonate products.

[0015] (5) The water-immersed graphite residue obtained in step (4) is thoroughly washed with water and then dried to obtain battery-grade recycled graphite products.

[0016] Furthermore, in step (1), the pretreatment includes steps such as discharge, disassembly, crushing, and sieving.

[0017] Furthermore, in step (2), the molar ratio of sulfuric acid in concentrated sulfuric acid to the sum of lithium, nickel, cobalt and manganese in black powder is 1 to 1.5 times.

[0018] Furthermore, in step (3), the microwave heat treatment temperature is controlled at 700-800℃ and the heat treatment time is 20-60 minutes.

[0019] Furthermore, in step (4), the post-treatment steps of the aqueous extract include purification, extraction and separation, and lithium carbonate precipitation.

[0020] Furthermore, in step (4), the liquid-to-solid ratio during stirring and leaching is 3-10 mL / g, the leaching time is 0.5-3 h, and the leaching temperature is 10-50 °C.

[0021] Furthermore, in step (5), the product is dried at 250–400°C.

[0022] For example, the method for synergistic conversion of ternary lithium-ion battery black powder positive electrode and repair and regeneration of graphite negative electrode according to the present invention includes the following steps:

[0023] (1) After the retired ternary lithium-ion batteries undergo pretreatment steps such as discharge, dismantling, crushing and screening, ternary lithium battery black powder is obtained.

[0024] (2) Mix the black powder with a certain amount of concentrated sulfuric acid. The molar ratio of sulfuric acid in the concentrated sulfuric acid to the sum of lithium, nickel, cobalt and manganese in the black powder is 1 to 1.5 times.

[0025] (3) Place the mixture into a microwave reactor for full microwave heat treatment. The heat treatment temperature is controlled at 700-800℃ and the heat treatment time is 20-60 minutes.

[0026] (4) The product after microwave heat treatment is stirred and leached in an aqueous solution to obtain a water leaching solution containing lithium, nickel, cobalt and manganese and water leached graphite residue; the water leaching solution is purified, extracted and separated, and precipitated with lithium carbonate to obtain nickel sulfate, cobalt sulfate, manganese sulfate and lithium carbonate products.

[0027] (5) The water-immersed graphite residue obtained in step (4) is thoroughly washed with water and then dried at 250-400℃ to obtain battery-grade recycled graphite products.

[0028] In step (4), the liquid-to-solid ratio during stirring and leaching is 3-10 mL / g, the leaching time is 0.5-3 h, and the leaching temperature is 10-50 °C.

[0029] This invention also relates to a combination of nickel sulfate, cobalt sulfate, manganese sulfate, lithium carbonate products and battery-grade regenerated graphite products obtained by the method described above for the synergistic conversion of ternary lithium-ion battery black powder positive electrode and the repair and regeneration of graphite negative electrode.

[0030] Beneficial effects

[0031] (1) In this invention, retired ternary lithium battery black powder is thoroughly mixed with concentrated sulfuric acid and then subjected to microwave heat treatment. Due to the strong wave absorption effect of graphite material, lithium, nickel, cobalt, manganese and impurity elements in ternary cathode material can be transformed into sulfates in a short time and at a low temperature. In the subsequent water leaching process, valuable metals can be effectively leached out, and impurities in graphite can also be efficiently removed.

[0032] (2) In this invention, the sulfates of nickel, cobalt and manganese have a catalytic graphitization effect on waste graphite. At the same time, under microwave heat treatment, the local temperature in waste graphite can reach more than 1,000 degrees Celsius, and its damaged structure can be effectively repaired and regenerated into graphite anode for batteries.

[0033] (3) The technical method of this invention is simple, energy-efficient, and has a high recovery rate of valuable metals. Waste graphite can be deeply purified and efficiently repaired and regenerated; that is, it realizes the efficient recovery of valuable metals and graphite in ternary lithium battery black powder, and has the prospect of industrial application.

[0034] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] Example 1

[0038] Retired ternary lithium-ion batteries were pre-treated by discharging, dismantling, crushing, and sieving to obtain ternary lithium-ion battery black powder. This black powder was then thoroughly mixed with concentrated sulfuric acid, with the amount of sulfuric acid in the concentrated sulfuric acid being 1.1 times the molar ratio of lithium, nickel, cobalt, and manganese in the black powder. The mixture was then placed in a microwave reactor for microwave heat treatment at 700℃ for 60 minutes. The product after microwave heat treatment was then leached in an aqueous solution with stirring. The liquid-to-solid ratio was 3 mL / g, the leaching time was 1 hour, and the leaching temperature was 20℃. The leaching rates were: lithium 98.4%, nickel 98.5%, cobalt 97.9%, and manganese 99.4%. The aqueous leaching solution was purified, extracted, separated, and precipitated with lithium carbonate to obtain nickel sulfate, cobalt sulfate, manganese sulfate, and lithium carbonate. The water-leached graphite residue was thoroughly washed with water and then dried at 400℃ to obtain recycled graphite. The initial charge specific capacity of the recycled graphite was 345 mAh / g, and the initial coulombic efficiency was 91.8%.

[0039] Example 2

[0040] Retired ternary lithium-ion batteries were pre-treated by discharging, dismantling, crushing, and sieving to obtain ternary lithium-ion battery black powder. This black powder was then thoroughly mixed with concentrated sulfuric acid, with the amount of sulfuric acid in the concentrated sulfuric acid being 1.5 times the molar ratio of lithium, nickel, cobalt, and manganese in the black powder. The mixture was then placed in a microwave reactor for microwave heat treatment at 800℃ for 20 minutes. The product after microwave heat treatment was then leached in an aqueous solution with stirring. The liquid-to-solid ratio was 8 mL / g, the leaching time was 2 hours, and the leaching temperature was 40℃. The leaching rates were: lithium 99.5%, nickel 97.6%, cobalt 98.1%, and manganese 99.5%. The aqueous leaching solution was purified, extracted, separated, and precipitated with lithium carbonate to obtain nickel sulfate, cobalt sulfate, manganese sulfate, and lithium carbonate. The water-leached graphite residue was thoroughly washed with water and then dried at 300℃ to obtain recycled graphite. The initial charge specific capacity of the recycled graphite was 352 mAh / g, and the initial coulombic efficiency was 90.7%.

[0041] Example 3

[0042] Retired ternary lithium-ion batteries were pre-treated by discharging, dismantling, crushing, and sieving to obtain ternary lithium-ion battery black powder. This black powder was then thoroughly mixed with concentrated sulfuric acid, with the amount of sulfuric acid in the concentrated sulfuric acid being 1.3 times the molar ratio of lithium, nickel, cobalt, and manganese in the black powder. The mixture was then placed in a microwave reactor for microwave heat treatment at 750℃ for 30 minutes. The product after microwave heat treatment was then leached in an aqueous solution with stirring. The liquid-to-solid ratio was 10 mL / g, the leaching time was 3 hours, and the leaching temperature was 30℃. The leaching rates were: lithium 98.9%, nickel 98.7%, cobalt 98.4%, and manganese 98.9%. The aqueous leaching solution was purified, extracted, separated, and precipitated with lithium carbonate to obtain nickel sulfate, cobalt sulfate, manganese sulfate, and lithium carbonate. The water-leached graphite residue was thoroughly washed with water and then dried at 250℃ to obtain recycled graphite. The initial charge specific capacity of the recycled graphite was 357 mAh / g, and the initial coulombic efficiency was 91.2%.

[0043] Comparative Example 1

[0044] Retired ternary lithium-ion batteries, after discharge, dismantling, crushing, and sieving pretreatment, yielded ternary lithium-ion battery black powder, which was then thoroughly mixed with concentrated sulfuric acid. The amount of sulfuric acid in the concentrated sulfuric acid was 1.1 times the molar ratio of lithium, nickel, cobalt, and manganese in the black powder. The mixture was then placed in a muffle furnace for heat treatment at 700℃ for 60 minutes. The heat-treated product was then leached in an aqueous solution with stirring. The liquid-to-solid ratio was 3 mL / g, the leaching time was 1 hour, and the leaching temperature was 20℃. The leaching rates were: lithium 91.3%, nickel 87.6%, cobalt 84.2%, and manganese 88.9%. The water-leached graphite residue was thoroughly washed with water and then dried at 400℃ to obtain recycled graphite. The initial charge specific capacity of the recycled graphite was 306 mAh / g, and the initial coulombic efficiency was 83.8%.

[0045] As can be seen, compared with the prior art, the solution described in this invention, by thoroughly mixing retired ternary lithium battery black powder with concentrated sulfuric acid and then subjecting it to microwave heat treatment, can transform lithium, nickel, cobalt, manganese and impurity elements in the ternary cathode material into sulfates in a shorter time and at a lower temperature. This allows for the effective leaching of valuable metals during subsequent water immersion, while also effectively repairing and regenerating the material into a graphite anode for batteries. The resulting product has good charging specific capacity and initial coulombic efficiency, thus achieving efficient recovery of valuable metals and graphite from ternary lithium battery black powder.

[0046] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A method for repairing and regenerating ternary lithium black powder cathodes in cooperation with graphite anodes, characterized by, The method comprises the following steps: (1) obtaining ternary lithium battery black powder after pretreatment of retired ternary lithium ion battery; (2) mixing the black powder with a certain amount of concentrated sulfuric acid; (3) putting the mixed material into a microwave reactor for sufficient microwave heat treatment; (4) stirring and leaching the product after microwave heat treatment in an aqueous solution to obtain an aqueous leaching solution containing lithium, nickel, cobalt and manganese and an aqueous leaching graphite residue; the aqueous leaching solution is treated to obtain nickel sulfate, cobalt sulfate, manganese sulfate and lithium carbonate products; (5) washing the aqueous leaching graphite residue obtained in step (4) with water and then drying to obtain battery-grade regenerated graphite products. In step (1), the pretreatment includes discharging, disassembling, crushing and screening steps; in step (2), the molar ratio of sulfuric acid in concentrated sulfuric acid to the sum of lithium, nickel, cobalt and manganese in the black powder is 1-1.5; in step (3), the temperature of microwave heat treatment is 700-800℃; in step (3), the treatment time of microwave heat treatment is 20-60 minutes.

2. The method of claim 1, wherein the treatment of the aqueous leaching solution in step (4) comprises purification, extraction separation and lithium carbonate precipitation.

3. The method of claim 1, wherein the liquid-solid ratio during stirring and leaching in step (4) is 3-10 mL / g.

4. The method of claim 1, wherein the leaching time during stirring and leaching in step (4) is 0.5-3 h.

5. The method of claim 1, wherein the leaching temperature during stirring and leaching in step (4) is 10-50℃.

6. The method of claim 1, wherein the drying temperature in step (5) is 250-400℃.