A method for recycling ternary lithium battery cathode material based on supercritical hydrothermal reaction

Abstract

The application provides a ternary lithium battery positive electrode material recycling method based on a supercritical hydrothermal reaction, which comprises the following steps: firstly, mixing the positive electrode sheet of the waste ternary lithium battery with a first oxidizing agent and deionized water, and performing a hydrothermal oxidation reaction in a supercritical state; after the reaction is completed, filtering to obtain filter residue; then, performing acid immersion on the filter residue by using inorganic acid liquid containing a reducing agent, and removing aluminum ions by precipitation; then, adding nickel salt, manganese salt and cobalt salt into the aluminum-removed filtrate, adjusting the proportion, and then adding a complexing agent and a precipitating agent to perform a co-precipitation reaction, so as to obtain a ternary precursor; finally, performing a hydrothermal crystallization reaction on the ternary precursor, and then mixing the ternary precursor with a lithium source and a second oxidizing agent to perform a hydrothermal synthesis reaction in a supercritical state, so as to obtain regenerated ternary positive electrode material. The method uses supercritical hydrothermal oxidation to treat the binder and the conductive additive in the positive electrode sheet, and simultaneously combines hydrothermal crystallization and supercritical hydrothermal synthesis technology, so that the synthesis time of the ternary lithium material is shortened.

Description

Technical Field

[0001] This invention relates to the field of battery recycling technology, and in particular to a method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction. Background Technology

[0002] Lithium-ion batteries, using ternary lithium as the cathode material, are widely used in the consumer electronics industry, leading to a surge in pressure for recycling and disposal of used batteries and a sharp increase in demand for metals such as lithium, cobalt, and nickel. Cobalt, when in the natural environment, can transform into compounds that are harmful to the environment. Therefore, recycling high-value metals such as lithium, cobalt, nickel, and aluminum from lithium-ion batteries can, on the one hand, prevent environmental pollution caused by waste; on the other hand, as high-value mineral elements, the recycling and reuse of lithium, cobalt, and nickel can reduce the pressure on mineral extraction and bring considerable economic benefits.

[0003] On the positive electrode of a lithium-ion battery, the positive electrode active material and acetylene black are coated onto aluminum foil using a binder. The key to separating the positive electrode and the positive electrode active material lies in removing the binder. In pyrometallurgical processes, binder removal is primarily achieved through high-temperature processes, which decompose the binder and release harmful fluorine-containing gases into the environment. In hydrometallurgical processes, organic solvents are typically used to dissolve the binder. This dissolution process requires expensive, environmentally harmful organic solvents and usually takes a considerable amount of time.

[0004] Furthermore, when recovering valuable metal ions from cathode active materials, many processes employ extraction methods to sequentially extract these ions. Extraction processes require environmentally harmful extractants and involve complex operations, increasing recovery costs and posing environmental risks. Summary of the Invention

[0005] This invention provides a method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction, which solves the defects of existing technologies such as complex recycling processes, high costs and high environmental pollution risks, and achieves efficient recycling of ternary lithium battery cathode materials.

[0006] This invention provides a method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction, comprising:

[0007] The positive electrode of the ternary lithium battery to be recycled is mixed with the first oxidant and deionized water, and a hydrothermal oxidation reaction is carried out under supercritical conditions. After the reaction is complete, solid-liquid separation is performed to obtain the first lithium-containing filtrate and filter residue.

[0008] The filter residue is acid-leached with an inorganic acid solution containing a reducing agent. An aluminum ion precipitant is added to the acid leaching solution. After precipitation is complete, solid-liquid separation is performed to obtain an aluminum-containing solid product and an aluminum-removed filtrate.

[0009] Nickel salt, manganese salt and cobalt salt are added to the aluminum removal filtrate to adjust the ion concentration of the solution. Then, complexing agent and precipitant are added to adjust the pH value to carry out a co-precipitation reaction. After the precipitation is complete, solid-liquid separation is performed to obtain the ternary precursor and the second lithium-containing filtrate.

[0010] After the ternary precursor undergoes a hydrothermal crystallization reaction, it is mixed with a lithium source and a second oxidant and subjected to a hydrothermal synthesis reaction under supercritical conditions. After the reaction is complete, solid-liquid separation is performed to obtain a regenerated ternary cathode material and a third lithium-containing filtrate.

[0011] A method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to the present invention further includes:

[0012] Water-soluble carbonates are added to the first, second, and third lithium-containing filtrates to precipitate lithium ions, and then filtered to obtain lithium carbonate.

[0013] According to the present invention, a method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction is provided, wherein the hydrothermal oxidation reaction is carried out at a temperature of 380℃~600℃, a pressure of 24MPa~40MPa, and a time of 5min~200min; and the amount of the first oxidant added is 1mol / L~12mol / L.

[0014] According to the present invention, a method for recycling ternary lithium battery cathode material based on supercritical hydrothermal reaction is provided, wherein the acid leaching process is carried out in a heated environment and a magnetic stirring device is used for stirring; the amount of reducing agent added is 0.1 mol / L to 5 mol / L; and the concentration of the inorganic acid solution is 1 mol / L to 5 mol / L.

[0015] According to the present invention, a method for recovering ternary lithium battery cathode material based on supercritical hydrothermal reaction is provided, wherein the molar ratio of nickel ions, cobalt ions and manganese ions in the aluminum removal filtrate is adjusted to 8:1:1, 5:2:3, 6:2:2 or 1:1:1.

[0016] According to the present invention, a method for recovering ternary lithium battery cathode material based on supercritical hydrothermal reaction is provided. In the coprecipitation reaction, the pH value of the aluminum removal filtrate is adjusted to 10-13, and the coprecipitation reaction is carried out in a heating environment while being stirred using a magnetic stirring device.

[0017] According to the present invention, a method for recycling ternary lithium battery cathode material based on supercritical hydrothermal reaction is provided. The ternary precursor after solid-liquid separation is mixed with deionized water and subjected to hydrothermal crystallization reaction in an oxygen-free environment at a temperature of 150℃~600℃, a pressure of 0.1MPa~40MPa, and a time of 2h~12h.

[0018] According to the present invention, a method for recovering ternary lithium battery cathode material based on supercritical hydrothermal reaction is provided, wherein the ternary precursor solution after hydrothermal crystallization reaction is mixed with the lithium source at a molar ratio of 1:(1.05~1.5), and the concentration of the lithium source is 1mol / L~6mol / L.

[0019] According to the present invention, a method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction is provided, wherein the hydrothermal synthesis reaction is carried out at a temperature of 380℃~600℃, a pressure of 24MPa~40MPa, and a time of 1h~12h; and the amount of the second oxidant added is 1mol / L~6mol / L.

[0020] According to the present invention, a method for recycling ternary lithium battery cathode material based on supercritical hydrothermal reaction is provided, wherein the first oxidant is one or more of hydrogen peroxide, oxygen, potassium permanganate, ammonium persulfate, sodium percarbonate, sodium peroxide, potassium peroxide, calcium peroxide, and lithium peroxide.

[0021] The reducing agent is one or more of hydrogen peroxide, sodium sulfite, sodium thiosulfate, ammonium sulfite, citric acid, and glucose; the inorganic acid solution is one or more of sulfuric acid, hydrochloric acid, and nitric acid.

[0022] The aluminum ion precipitant is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide;

[0023] The nickel salt is one or more selected from nickel sulfate, nickel chloride, nickel sulfamate, nickel bromide, nickel acetate, nickel hydroxide, and nickel carbonyl; the cobalt salt is one or more selected from cobalt sulfate, cobalt nitrate, cobalt carbonate, cobalt acetate, and cobalt chloride; the manganese salt is one or more selected from manganese sulfate, manganese carbonate, manganese acetate, and manganese chloride.

[0024] The complexing agent is ammonia, and the precipitant is sodium hydroxide and / or potassium hydroxide;

[0025] The lithium source is one or more of lithium hydroxide, lithium oxalate, and lithium acetate; the second oxidant is one or more of hydrogen peroxide, oxygen, and ozone.

[0026] This invention provides a method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction. The method involves oxidizing and decomposing the binder and conductive additives on the ternary lithium battery cathode sheet using supercritical water containing an oxidant, thus separating the cathode material from the aluminum foil substrate. Next, the filter residue is acid-leached with an inorganic acid solution containing a reducing agent to leach out nickel, cobalt, and manganese elements from the cathode material. Simultaneously, an aluminum ion precipitant is used to separate aluminum-containing solid products, achieving aluminum recovery. Then, nickel, cobalt, and manganese salts are used to adjust the ion concentration ratio in the aluminum removal filtrate, and a ternary precursor is synthesized through co-precipitation. Finally, the co-precipitated ternary precursor is subjected to hydrothermal crystallization treatment, and the crystallized ternary precursor is mixed with a lithium source to synthesize regenerated ternary cathode materials under a supercritical hydrothermal environment, achieving the recovery and regeneration of ternary lithium. This method uses supercritical hydrothermal oxidation to treat binders and conductive additives in the positive electrode sheet, eliminating the need for toxic and expensive organic solvents and achieving zero emissions of toxic gases. It can quickly and effectively remove binders and conductive additives, is highly efficient, and environmentally friendly. In addition, in the subsequent ion recovery and regeneration process, ternary precursors are directly co-precipitated by adding complexing agents and precipitants, avoiding the very complex extraction process and eliminating the need for extractants that cause serious environmental pollution. At the same time, the combination of hydrothermal crystallization and supercritical hydrothermal synthesis technology shortens the process of hydrothermal synthesis of ternary lithium materials and improves the crystallinity of the product. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a schematic flowchart of the method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction provided by the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] like Figure 1 As shown in the figure, an embodiment of the present invention provides a method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction, comprising:

[0031] Step S100: The positive electrode of the ternary lithium battery to be recycled is mixed with the first oxidant and deionized water, and a hydrothermal oxidation reaction is carried out under supercritical conditions. After the reaction is complete, solid-liquid separation is performed to obtain the first lithium-containing filtrate and filter residue.

[0032] Specifically, the positive electrode sheet of the ternary lithium battery to be recycled generally uses aluminum foil as a base, with positive electrode material uniformly coated on both sides. The positive electrode material includes a certain proportion of ternary lithium positive electrode active material, conductive additives and binders. The conductive additives mainly include acetylene black, graphite, etc., and the binder is mainly polyvinylidene fluoride (PVDF).

[0033] The amount of the first oxidant added is 1 mol / L to 12 mol / L. In some specific embodiments, the first oxidant can be one or a mixture of hydrogen peroxide, oxygen, potassium permanganate, ammonium persulfate, sodium percarbonate, sodium peroxide, potassium peroxide, calcium peroxide, and lithium peroxide. The first oxidant can be prepared into an aqueous solution with deionized water. If it is a gaseous oxidant, it can be directly introduced into the hydrothermal reactor.

[0034] The solid-liquid ratio of the positive electrode sheet and the aqueous solution of the oxidant added to the hydrothermal reactor can range from 1 g / L to 100 g / L, and the filling degree of the hydrothermal reactor can be from 30% to 60%. By heating and pressurizing the hydrothermal reactor, the aqueous solution of the oxidant inside is brought to a high-temperature, high-pressure supercritical state above the critical point, thereby achieving hydrothermal oxidation of the binder and conductive additives. The oxidation products are carbon dioxide, water, hydrofluoric acid, and salt compounds, without producing toxic waste gas emissions. Because the binder is oxidized and decomposed, the positive electrode material can be separated from the aluminum foil substrate. At the same time, the ternary lithium active material in the positive electrode material is partially or completely reduced to divalent compounds by carbon (from acetylene black or graphite, etc.) and carbon oxides are generated. In addition, under supercritical conditions, due to the extremely strong reactivity of the solution in the hydrothermal reactor, the remaining carbon can be almost completely oxidized, achieving complete removal of carbon without the need for subsequent additional carbon removal. In some specific embodiments, the temperature of the hydrothermal oxidation reaction is 380℃~600℃, the pressure is 24MPa~40MPa, and the time is 5min~200min.

[0035] After the hydrothermal oxidation reaction is completed, the hydrothermal reactor is cooled and depressurized, and the reaction product is removed. The product is then subjected to solid-liquid separation and washing, and the first lithium-containing filtrate and filter residue are collected separately. The filter residue mainly contains aluminum and aluminum oxide / hydroxides, unreduced ternary materials, and low-valence compounds of nickel, cobalt, and manganese. Under supercritical conditions, the rate of the hydrothermal oxidation reaction is increased, and the time required for complete reaction is correspondingly reduced, thus improving the overall removal efficiency and effectiveness of adhesives and conductive additives.

[0036] Step S200: The filter residue is acid-leached with an inorganic acid solution containing a reducing agent. An aluminum ion precipitant is added to the acid leaching solution. After the precipitation is complete, solid-liquid separation is performed to obtain an aluminum-containing solid product and an aluminum-removed filtrate.

[0037] Specifically, the amount of reducing agent added can be 0.1 mol / L to 5 mol / L, and the concentration of the inorganic acid solution can be 1 mol / L to 5 mol / L. In some specific embodiments, the reducing agent can be one or more of hydrogen peroxide, sodium sulfite, sodium thiosulfate, ammonium sulfite, citric acid, and glucose. The inorganic acid solution can be one or more of sulfuric acid, hydrochloric acid, and nitric acid. The solid-liquid ratio of the filter residue to the acid leaching solution can be in the range of 1 g:(60~100) mL. By adding a reducing agent under acidic conditions, metal elements such as nickel, cobalt, manganese, and lithium are leached into the aqueous solution in ionic form.

[0038] After acid leaching, an aluminum ion precipitant is added to the leaching solution to remove aluminum ions. The aluminum ion precipitant is primarily an alkaline reagent; in some specific embodiments, it can be one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide. After the pH of the leaching solution is adjusted to 3-6 and the aluminum ions are completely precipitated, the leaching solution is subjected to solid-liquid separation to obtain an aluminum-free filtrate and an aluminum-containing solid product. Aluminum is mainly recovered in the form of aluminum and aluminum hydroxide.

[0039] Step S300: Add nickel salt, manganese salt and cobalt salt to the aluminum removal filtrate to adjust the ion concentration of the solution, and then add complexing agent and precipitant to adjust the pH value to carry out co-precipitation reaction. After the precipitation is complete, solid-liquid separation is performed to obtain the ternary precursor and the second lithium-containing filtrate.

[0040] Specifically, the concentrations of nickel, cobalt, and manganese ions in the aluminum-removing filtrate are measured, and the molar concentrations of nickel, cobalt, and manganese ions are adjusted to a specific ratio by adding nickel, manganese, and cobalt salts. This specific ratio can be determined according to the type of ternary lithium cathode material to be generated. In some specific embodiments, this molar ratio can be 8:1:1, 5:2:3, 6:2:2, or 1:1:1. The nickel salt used can be one or more of nickel sulfate, nickel chloride, nickel sulfamate, nickel bromide, nickel acetate, nickel hydroxide, and nickel carbonyl; the cobalt salt can be one or more of cobalt sulfate, cobalt nitrate, cobalt carbonate, cobalt acetate, and cobalt chloride; and the manganese salt can be one or more of manganese sulfate, manganese carbonate, manganese acetate, and manganese chloride.

[0041] A complexing agent and a precipitant are then added to adjust the pH value for coprecipitation. Specifically, the pH value of the aluminum-removing filtrate can be adjusted to 10-13. The complexing agent can be NH3·H2O, and the precipitant can be sodium hydroxide and / or potassium hydroxide. The coprecipitation reaction can be carried out under heating conditions while being stirred using a magnetic stirrer. In some specific embodiments, the coprecipitation reaction temperature can be 50℃-80℃, the magnetic stirring speed can be 100r / min-800r / min, and the reaction time can be 1h-25h. After complete coprecipitation, solid-liquid separation is performed to obtain the ternary precursor and the second lithium-containing filtrate.

[0042] In step S400, after the ternary precursor undergoes a hydrothermal crystallization reaction, it is mixed with a lithium source and a second oxidant and subjected to a hydrothermal synthesis reaction under supercritical conditions. After the reaction is complete, solid-liquid separation is performed to obtain a regenerated ternary cathode material and a third lithium-containing filtrate.

[0043] Specifically, the ternary precursor obtained from co-precipitation is first washed to remove residual impurities, then mixed with an appropriate amount of deionized water and placed in a hydrothermal reactor for hydrothermal crystallization. The hydrothermal crystallization reaction is carried out in an oxygen-free environment, and a protective gas, such as nitrogen or argon, can be filled into the hydrothermal reactor. The hydrothermal crystallization temperature is 150℃~600℃, the pressure is 0.1MPa~40MPa, and the time is 2h~12h. When the pressure is 0.1MPa~24MPa, it is conventional hydrothermal crystallization; in this case, the hydrothermal reactor can be lined with Teflon to prevent ions from precipitating from the metal reactor into the solution. When the pressure is 24MPa~40MPa, it is supercritical hydrothermal crystallization.

[0044] Then, the crystallized ternary precursor solution is mixed with a lithium source and a second oxidant, and a hydrothermal synthesis reaction is carried out under supercritical conditions. The filling rate of the hydrothermal reactor can be 20%~60%. After the reaction is complete, solid-liquid separation is performed to obtain regenerated ternary cathode material and a third lithium-containing filtrate. In some specific embodiments, the ternary precursor solution and the lithium source are mixed at a molar ratio of 1:(1.05~1.5), and the concentration of the lithium source is 1mol / L~6mol / L. The lithium source can be one or more of lithium hydroxide, lithium oxalate, and lithium acetate. The temperature of the supercritical hydrothermal synthesis reaction is 380℃~600℃, the pressure is 24MPa~40MPa, and the time is 1h~12h. The amount of the second oxidant added is 1mol / L~6mol / L. The second oxidant can be one or more of hydrogen peroxide, oxygen, and ozone.

[0045] After the supercritical hydrothermal synthesis reaction is completed, the product is filtered and washed to obtain the recycled ternary lithium cathode material.

[0046] This embodiment provides a method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction. The method involves oxidizing and decomposing the binder and conductive additives on the ternary lithium battery cathode sheet using supercritical water containing an oxidant, thus separating the cathode material from the aluminum foil substrate. Next, the filter residue is acid-leached with an inorganic acid solution containing a reducing agent to leach out nickel, cobalt, and manganese elements from the cathode material. Simultaneously, an aluminum ion precipitant is used to separate aluminum-containing solid products, achieving aluminum recovery. Then, nickel, cobalt, and manganese salts are used to adjust the ion concentration ratio in the aluminum removal filtrate, and a ternary precursor is synthesized via co-precipitation. Finally, the co-precipitated ternary precursor is subjected to hydrothermal crystallization treatment, and the crystallized ternary precursor is mixed with a lithium source to synthesize regenerated ternary cathode materials under a supercritical hydrothermal environment, achieving the recovery and regeneration of ternary lithium. This method uses supercritical hydrothermal oxidation to treat binders and conductive additives in the positive electrode sheet, eliminating the need for toxic and expensive organic solvents and achieving zero emissions of toxic gases. It can quickly and effectively remove binders and conductive additives, is highly efficient, and environmentally friendly. In addition, in the subsequent ion recovery and regeneration process, ternary precursors are directly co-precipitated by adding complexing agents and precipitants, avoiding the very complex extraction process and eliminating the need for extractants that cause serious environmental pollution. At the same time, the combination of hydrothermal crystallization and supercritical hydrothermal synthesis technology shortens the process of hydrothermal synthesis of ternary lithium materials and improves the crystallinity of the product.

[0047] Furthermore, based on the above embodiments, it also includes:

[0048] Step S500: Water-soluble carbonate is added to the first, second, and third lithium-containing filtrates to precipitate lithium ions, and the filtrate is filtered to obtain lithium carbonate. The first, second, and third lithium-containing filtrates can be precipitated separately, or they can be mixed in pairs or all at once before precipitation, depending on the lithium ion concentration in each filtrate. In some specific embodiments, the water-soluble carbonate can be one or more of (NH4)2CO3, Na2CO3, K2CO3, Rb2CO3, and Cs2CO3. By recovering lithium ions from the hydrothermal filtrate, the recovery rate of valuable metals from spent ternary lithium batteries is further improved.

[0049] Furthermore, based on the above embodiments, the acid leaching process in step S200 can be carried out under heating conditions, while the acid leaching solution is stirred using a magnetic stirrer. Specifically, the heating temperature can be 60℃~95℃, the stirring speed can be 100r / min~800r / min, and the time can be 1h~5h.

[0050] Furthermore, based on the above embodiments, the positive electrode of the ternary lithium battery to be recycled in step S100 is the positive electrode obtained by disassembling and sorting the waste ternary lithium battery after it has been fully discharged. Specifically, the waste ternary lithium battery can be discharged using physical discharge method and / or chemical discharge method; after the charge in the battery is completely released, the outer shell of the lithium battery is disassembled manually to obtain the battery core, and then the plastic film of the lithium battery pack and the positive and negative electrodes are sorted manually to obtain the positive electrode of the ternary lithium battery to be recycled.

[0051] The specific process of this method will be illustrated below with a specific embodiment.

[0052] First, after fully discharging the failed 2032 button-type ternary LNCM111 battery, the battery was manually disassembled, and the circular positive electrode sheets were sorted out. The positive electrode sheets were weighed and mixed with 28 mL of 30% hydrogen peroxide solution and 3.5 mL of deionized water, then placed in a 70 mL high-pressure hydrothermal reactor. The high-pressure hydrothermal reactor was sealed and placed in a pit furnace for heating, raising the internal temperature of the reactor to 420°C. The temperature inside the reactor was maintained at 420°C for 30 minutes. After cooling and depressurizing the reactor, the product was removed. The product was filtered, washed, and the first lithium-containing filtrate and filter residue were collected. Sodium carbonate was added to the first lithium-containing filtrate to recover lithium ions in the form of lithium carbonate precipitation.

[0053] The filter residue was subjected to acid leaching treatment. 182 mg of the filter residue was added to 18.2 mL of a mixed solution of sulfuric acid and hydrogen peroxide, making the solid-liquid ratio 10:1 mg / mL. The concentration of hydrogen peroxide in the acid leaching solution was 0.97 mol / L, and the concentration of sulfuric acid was 2 mol / L. The mixture was heated to 90 °C in a water bath and maintained for 180 min, while being magnetically stirred at 500 r / min.

[0054] Add NaOH solution to adjust the pH to pH=5, filter the acid leaching solution, and recover aluminum as aluminum and aluminum hydroxide. Adjust the ion concentration in the filtered leachate by adding nickel sulfate, cobalt sulfate, and manganese sulfate to adjust the nickel, cobalt, and manganese ion concentrations to 0.1 mol / L. Add NH3·H2O as a complexing agent and NaOH solution as a precipitating agent, adjust the pH to 11, maintain the reaction temperature at 55℃, and the stirring speed at 500 r / min to co-precipitate Ni. 1 / 3 Co 1 / 3 Mn 1 / 3 (OH)2 precursor was filtered and repeatedly rinsed with water. The precursor obtained by co-precipitation was mixed with deionized water and added to a hydrothermal reactor. The mixture was reacted at 200°C for 10 hours to obtain a crystallized ternary precursor. The second lithium-containing filtrate obtained by co-precipitation and filtration was added with sodium carbonate solution to precipitate lithium carbonate.

[0055] Crystallized Ni 1 / 3 Co 1 / 3 Mn 1 / 3 The (OH)₂ precursor was mixed with a 3 mol / L lithium hydroxide aqueous solution at a molar ratio of 1:1.05. The mixture was placed in a supercritical hydrothermal reactor, and oxygen was introduced through a high-pressure pump. The hydrothermal reactor was heated to 420°C and maintained for 6 hours. After cooling, the mixture was filtered to obtain LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 was used to rinse the product and then dry it.

[0056] As can be seen from the above embodiments, the ternary lithium battery cathode material recycling method based on supercritical hydrothermal reaction provided by the present invention uses supercritical hydrothermal oxidation technology to oxidize and decompose the binder, electrolyte, and acetylene black on the ternary lithium battery cathode, thereby separating the ternary cathode material from the electrode sheet. After leaching nickel, cobalt, and manganese elements in the cathode material, a ternary precursor is synthesized by co-precipitation, and then crystallized by hydrothermal crystallization to improve the crystallinity of the material. Finally, the highly crystalline ternary precursor is converted into ternary lithium cathode material by supercritical hydrothermal synthesis. This process rapidly separates and recycles the cathode active material without the use of toxic and expensive organic solvents, and can also achieve zero emissions of toxic gases. It can quickly and effectively remove binders and conductive additives, is highly efficient, and environmentally friendly. At the same time, the combination of hydrothermal crystallization and supercritical hydrothermal synthesis technology shortens the hydrothermal synthesis process of ternary lithium material and improves the crystallinity of the product. In addition, aluminum and lithium elements in the cathode sheet are also recovered.

[0057] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recycling ternary lithium battery cathode materials based on supercritical hydrothermal reaction, characterized in that, include: The positive electrode of the ternary lithium battery to be recycled is mixed with the first oxidant and deionized water, and a hydrothermal oxidation reaction is carried out under supercritical conditions. After the reaction is complete, solid-liquid separation is performed to obtain the first lithium-containing filtrate and filter residue. The filter residue is acid-leached with an inorganic acid solution containing a reducing agent. An aluminum ion precipitant is added to the acid leaching solution. After precipitation is complete, solid-liquid separation is performed to obtain an aluminum-containing solid product and an aluminum-removed filtrate. Nickel salt, manganese salt and cobalt salt are added to the aluminum removal filtrate to adjust the ion concentration of the solution. Then, complexing agent and precipitant are added to adjust the pH value to carry out a co-precipitation reaction. After the precipitation is complete, solid-liquid separation is performed to obtain the ternary precursor and the second lithium-containing filtrate. After the ternary precursor undergoes a hydrothermal crystallization reaction, it is mixed with a lithium source and a second oxidant and subjected to a hydrothermal synthesis reaction under supercritical conditions. After the reaction is complete, solid-liquid separation is performed to obtain a regenerated ternary cathode material and a third lithium-containing filtrate.

2. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to claim 1, characterized in that, Also includes: Water-soluble carbonates are added to the first, second, and third lithium-containing filtrates to precipitate lithium ions, and then filtered to obtain lithium carbonate.

3. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to claim 1, characterized in that, The hydrothermal oxidation reaction is carried out at a temperature of 380℃~600℃, a pressure of 24MPa~40MPa, and a time of 5min~200min; the amount of the first oxidant added is 1mol / L~12mol / L.

4. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to claim 1, characterized in that, The acid leaching process is carried out under heating conditions, and a magnetic stirring device is used for stirring; the amount of reducing agent added is 0.1 mol / L to 5 mol / L; the concentration of the inorganic acid solution is 1 mol / L to 5 mol / L.

5. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to claim 1, characterized in that, Nickel salt, manganese salt, and cobalt salt are added to the aluminum removal filtrate to adjust the molar ratio of nickel ions, cobalt ions, and manganese ions in the aluminum removal filtrate to 8:1:1, 5:2:3, 6:2:2, or 1:1:

1.

6. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to claim 5, characterized in that, In the coprecipitation reaction, the pH of the aluminum-removing filtrate is adjusted to 10-13, and the coprecipitation reaction is carried out under heating conditions while being stirred using a magnetic stirrer.

7. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to claim 1, characterized in that, The ternary precursor, after solid-liquid separation, is mixed with deionized water and subjected to hydrothermal crystallization reaction in an oxygen-free environment at a temperature of 150℃~600℃, a pressure of 0.1MPa~40MPa, and a time of 2h~12h.

8. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to claim 1, characterized in that, The ternary precursor solution after hydrothermal crystallization reaction is mixed with the lithium source at a molar ratio of 1:(1.05~1.5), and the concentration of the lithium source is 1mol / L~6mol / L.

9. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to claim 1, characterized in that, The hydrothermal synthesis reaction is carried out at a temperature of 380℃~600℃, a pressure of 24MPa~40MPa, and a time of 1h~12h; the amount of the second oxidant added is 1mol / L~6mol / L.

10. The method for recovering ternary lithium battery cathode materials based on supercritical hydrothermal reaction according to any one of claims 1 to 9, characterized in that, The first oxidant is one or more of hydrogen peroxide, oxygen, potassium permanganate, ammonium persulfate, sodium percarbonate, sodium peroxide, potassium peroxide, calcium peroxide, and lithium peroxide; The reducing agent is one or more of hydrogen peroxide, sodium sulfite, sodium thiosulfate, ammonium sulfite, citric acid, and glucose; the inorganic acid solution is one or more of sulfuric acid, hydrochloric acid, and nitric acid. The aluminum ion precipitant is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide; The nickel salt is one or more selected from nickel sulfate, nickel chloride, nickel sulfamate, nickel bromide, nickel acetate, nickel hydroxide, and nickel carbonyl; the cobalt salt is one or more selected from cobalt sulfate, cobalt nitrate, cobalt carbonate, cobalt acetate, and cobalt chloride; the manganese salt is one or more selected from manganese sulfate, manganese carbonate, manganese acetate, and manganese chloride. The complexing agent is ammonia, and the precipitant is sodium hydroxide and / or potassium hydroxide; The lithium source is one or more of lithium hydroxide, lithium oxalate, and lithium acetate; the second oxidant is one or more of hydrogen peroxide, oxygen, and ozone.

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