A method for recovering cobalt and lithium in waste lithium cobalt oxide batteries by molten salt electrolysis

Abstract

The application discloses a recovery method of recovering cobalt and lithium in waste and old lithium cobalt oxide batteries through molten salt electrolysis, and comprises the following steps: mixing positive electrode powder of the waste and old lithium cobalt oxide batteries with cobalt chloride and adding into an electrolytic cell containing lithium chloride molten salt to perform electrolysis; performing leaching on the molten salt after electrolysis; and performing solid-liquid separation on the leaching product to obtain leaching liquid and leaching residue; the leaching liquid is a lithium chloride solution; and the leaching residue is cobalt powder. Compared with a traditional process flow, the recovery method of recovering cobalt and lithium in waste and old lithium cobalt oxide batteries through molten salt electrolysis greatly reduces the process flow, avoids using acid leaching and extraction processes in the traditional process, reduces the emission of waste liquid and waste gas, is clean and environmentally friendly, and can realize continuous operation; in the electrolysis process, new positive electrode powder and cobalt chloride can be continuously added into the molten salt along with the consumption of the lithium cobalt oxide, so that the production process is continuous.

Description

Technical Field

[0001] This invention belongs to the field of battery recycling, and in particular relates to a method for recycling waste lithium cobalt oxide cathode materials. Background Technology

[0002] With the large-scale extraction and use of fossil fuels, greenhouse gas and pollutant emissions are increasing, and the greenhouse effect and other environmental problems are becoming increasingly significant. Therefore, the use and storage of clean energy are crucial. Batteries are one of the most common energy storage systems. Among them, lithium-ion batteries, due to their advantages such as high specific capacity and energy density, ease of operation, and relatively long lifespan, are the most widely used batteries in portable devices, electric vehicles, and grid energy storage. Due to the continuous upgrading of consumer electronics and the rapid development of electric vehicles, a large number of lithium-ion batteries have been manufactured in recent decades. Furthermore, with the increasing number of electric vehicles, the demand for lithium-ion batteries will further increase. A large number of waste lithium-ion batteries are expected to be generated in the next decade. Waste lithium-ion batteries are rich in valuable metals, making them a high-value urban mineral resource. Resource recycling of waste lithium batteries not only meets social needs but also alleviates resource shortages caused by the increase in lithium battery production capacity.

[0003] Currently, methods for resource recovery from spent lithium batteries include wet recycling, pyrometallurgical recycling, and direct regeneration. Wet recycling typically involves transferring valuable metals from the cathode material to a leaching solution to facilitate subsequent precipitation and purification processes. Common inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, combined with H2O2, can all be used for leaching cathode materials. For example, patent CN108330286A discloses a method for comprehensively recovering cobalt and lithium from lithium cobalt oxide waste. The lithium cobalt oxide waste is first leached and filtered with an acid solution. The resulting filtrate is then used to selectively adsorb cobalt using a multivalent metal adsorption resin. The remaining filtrate is then separated to obtain lithium hydroxide using a bipolar membrane. This process has low cost, but the inorganic acids used are highly corrosive, require sophisticated equipment, and easily generate harmful gases such as Cl2 and SO2.

[0004] Pyrometallurgical recycling involves recovering metallic elements from spent lithium-ion batteries using high-temperature methods, in the form of metals and their compounds. For example, patent CN114317983A discloses a method for separating and extracting valuable metals from the positive electrode of spent lithium batteries. This method uses organic binders and conductive additives such as carbon black as reducing agents to carbothermally reduce lithium cobalt oxide in the positive electrode sheet, achieving lithium and cobalt separation through leaching, water leaching, filtration, and acid leaching. In this process, lithium is recovered as lithium carbonate. Lithium carbonate is only slightly soluble in water, and the subsequent leaching process has a large liquid-solid ratio, easily leading to low recovery rates and high emissions.

[0005] Direct regeneration primarily utilizes lithium salts to restore NCM cathodes damaged by lithium-ion loss and cation mixing. For example, patent CN11021783A discloses a molten salt activation regeneration method for spent lithium-ion battery cathode material lithium cobalt oxide. This process places the failed cathode material in a molten salt containing lithium salt for activation. During this process, the high-temperature molten salt reconstructs the crystal structure of the failed lithium cobalt oxide, restoring and improving its lithium storage performance. While this process is simple, the regenerated product exhibits poor cycle performance and low charge / discharge capacity.

[0006] Therefore, currently available lithium cobalt oxide battery recycling technologies mainly suffer from the following problems: complex process flow, low product recovery rate, consumption of large amounts of corrosive reagents such as acids, high emissions of waste liquid and waste gas, and difficulty in continuous operation. Therefore, developing a clean, pollution-free, high-recovery-rate, and continuously operable lithium cobalt oxide cathode material recycling process is of great significance. Summary of the Invention

[0007] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a short-process, emission-free, high-recovery-rate, and continuous-operation method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis. To solve the above technical problem, the technical solution proposed by this invention is as follows:

[0008] A method for recovering cobalt and lithium from waste lithium cobalt oxide batteries by molten salt electrolysis includes the following steps: mixing waste lithium cobalt oxide battery cathode powder with cobalt chloride and adding it to an electrolytic cell containing lithium chloride molten salt for electrolysis; leaching the molten salt after electrolysis; and then performing solid-liquid separation on the leaching product to obtain leachate and leach residue, wherein the leachate is a lithium chloride solution and the leach residue is cobalt powder.

[0009] In the above recycling method, preferably, the particle size of the waste lithium cobalt oxide battery cathode powder is controlled to be less than 50 μm. Larger cathode powder particle size reduces its dissolution rate in molten salt and also hinders particle migration within the molten salt.

[0010] In the above recycling method, preferably, the amount of waste lithium cobalt oxide battery cathode powder added is 5-30 wt% of the mass of lithium chloride molten salt, and the amount of cobalt chloride added is 0.4-0.6 times the molar amount of lithium cobalt oxide in the waste lithium cobalt oxide battery cathode powder. A higher amount of waste lithium cobalt oxide battery cathode powder added will cause a rapid increase in the system's melting point, which is detrimental to the mass transfer process within the molten salt. Cobalt chloride can provide a chlorine source for lithium, allowing lithium in the product to be recovered in the form of lithium chloride. Furthermore, cobalt chloride provides a chlorine source, preventing the accumulation of high-melting-point lithium oxide (1567℃) during the reaction, which would lead to an increase in the melting point of the reaction system, thus hindering the continuous operation of electrolysis. Adding cobalt chloride will provide a chlorine source for lithium, thereby converting lithium oxide into lithium chloride, maintaining the stability of the electrolyte composition during electrolysis, and ensuring the smooth progress of continuous reaction when waste lithium cobalt oxide battery cathode powder is added to the molten salt.

[0011] In the above-mentioned recycling method, preferably, the electrolysis temperature is controlled at 650-750℃, and the atmosphere during electrolysis is argon and / or nitrogen. This electrolysis temperature helps the molten salt maintain good fluidity; further increases in temperature will lead to excessive volatilization of lithium chloride.

[0012] In the above-mentioned recycling method, preferably, constant voltage electrolysis is used, controlling the electrolytic cell voltage at 1.5-2.5V, and the electrolysis duration is 1.1-1.3 times the theoretical electrolysis time t (in hours); the theoretical electrolysis time t is calculated according to the following formula:

[0013]

[0014] Where n is the molar amount of lithium cobalt oxide in the cathode powder of waste lithium cobalt oxide batteries, and I is the average current (unit: ampere).

[0015] In the above recycling method, preferably, waste lithium cobalt oxide battery cathode powder and cobalt chloride are continuously added to the electrolytic cell as electrolysis proceeds. Continuous addition of waste lithium cobalt oxide battery cathode powder and cobalt chloride enables continuous production.

[0016] In the above-mentioned recycling method, preferably, pure water is used to absorb the tail gas during electrolysis to obtain tail gas absorbent, and the tail gas absorbent is used as leachate during leaching.

[0017] In the above recycling method, preferably, a metal rod / plate / mesh is used as the cathode and graphite is used as the anode for electrolysis, and the cathode metal is one of molybdenum, tungsten, titanium, and cobalt.

[0018] In the above-mentioned recycling method, preferably, the leaching time is controlled to be 0.5-2h and the leaching liquid-to-solid ratio is (1.5-3):1.

[0019] In the above recycling method, preferably, the lithium chloride solution is evaporated, concentrated, cooled, and crystallized to prepare lithium chloride powder; a portion of the cobalt powder is chlorinated and regenerated and returned to be mixed with the waste lithium cobalt oxide battery cathode powder, wherein the chlorinated regenerated cobalt powder accounts for 30-40 wt% of the total cobalt powder mass.

[0020] The principle of this invention is briefly described as follows: This invention uses molten salt electrolysis to recover lithium and cobalt from spent lithium cobalt oxide batteries. Lithium chloride is used as the molten salt in the process, and the positive electrode powder from the spent lithium cobalt oxide batteries is added to the molten salt. Cobalt chloride is used as the chlorine source. The positive electrode powder (lithium cobalt oxide) is dissolved in the molten salt using Li... + CoO2 - O 2- Co 3+ It exists in the form of cobaltate or cobalt ions dissolved in the electrolytic cell. During the electrolysis process, the positive and negative electrodes undergo the following reactions, respectively.

[0021] positive electrode:

[0022] Carbon material as anode: n / 2C + nO 2- →n / 2CO2+2ne - ;

[0023] negative electrode:

[0024] CoO x +2ne - →CoO x-n +nO 2- ;

[0025] nCo 2+ +2ne - →nCo;

[0026] The molten salt system is heated to a predetermined temperature, where lithium cobalt oxide and cobalt chloride are uniformly distributed. Applying a voltage causes oxygen ions to migrate towards the negative electrode and anions towards the positive electrode. Since the deposition potential of cobalt ions is more positive than that of lithium ions, metallic cobalt is preferentially deposited during electrolysis. As cobalt ions are reduced to elemental cobalt, oxygen ions escape as carbon dioxide or oxygen gas, and chloride ions combine with lithium ions during cooling to form lithium chloride. The electrolysis process consumes both lithium cobalt oxide and cobalt chloride. The reaction process can be continuously maintained by adding cathode powder and cobalt chloride, ensuring that only lithium chloride remains in the molten salt system at the reaction endpoint. Because a small amount of lithium chloride may volatilize during electrolysis, the tail gas from the electrolysis unit is absorbed using pure water. The pure water in the tail gas absorption unit acts as a leaching agent, further improving the lithium recovery rate.

[0027] This invention allows for electrochemical regulation to control the particle size of the product (cobalt powder), thereby achieving product diversity. The cobalt chloride used as an additive in this invention can be regenerated through the chlorination of cobalt powder, achieving internal material circulation; simultaneously, the solution in the tail gas absorption device can be used as a leachate, realizing a closed-loop circulation of all chemical reagents.

[0028] Compared with the prior art, the advantages of the present invention are as follows:

[0029] 1. The method for recycling cobalt and lithium from waste lithium cobalt oxide batteries by molten salt electrolysis of the present invention significantly reduces the traditional process flow, avoids the use of acid leaching and extraction processes in the traditional process, reduces the emission of waste liquid and waste gas, and the process is clean and environmentally friendly.

[0030] 2. The present invention relates to a method for recovering cobalt and lithium from waste lithium cobalt oxide batteries by molten salt electrolysis, and by adding cobalt chloride, a high-purity lithium chloride product is finally obtained. Lithium chloride has high solubility in pure water (83.5g / 100ml 20℃), and can achieve efficient leaching at room temperature. The liquid-to-solid ratio is low, which reduces the energy consumption of subsequent purification processes. The final product has high purity and high recovery rate.

[0031] 3. The method for recovering cobalt and lithium from waste lithium cobalt oxide batteries by molten salt electrolysis of the present invention can achieve continuous operation. As lithium cobalt oxide is consumed during the electrolysis process, new cathode powder and cobalt chloride can be continuously added to the molten salt to achieve continuous production process. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a process flow diagram of the molten salt electrolysis method for recovering cobalt and lithium from waste lithium cobalt oxide batteries according to the present invention.

[0034] Figure 2 This is a schematic diagram of the reaction process of the molten salt electrolysis method for recovering cobalt and lithium from waste lithium cobalt oxide batteries according to the present invention.

[0035] Figure 3 The magnetic cobalt powder obtained after leaching in Example 1. Detailed Implementation

[0036] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0038] 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.

[0039] The waste lithium cobalt oxide batteries used in the following examples and comparative examples were from the same batch of manually dismantled waste lithium cobalt oxide batteries. The pre-discharged lithium cobalt oxide was split and crushed, then vacuum pyrolyzed at 450°C, 100 Pa, for 2 hours. The products after vacuum pyrolysis were sieved and ground to obtain cathode powder with a particle size of less than 50 μm. Its main components are shown in the table below.

[0040] Table 1: Main Components and Contents of Positive Electrode Powder

[0041]

[0042] Example 1:

[0043] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0044] Lithium chloride was used as the molten salt. 3.3 wt% cobalt chloride and 5 wt% lithium chloride molten salt cathode powder were added to the electrolytic cell. A high-purity graphite rod (99.9 wt%) was used as the anode, and a molybdenum rod as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The argon flow rate was controlled at 50 ml / min, and the temperature was raised to 650℃. Electrolysis was performed at a constant voltage of 1.6V for 11 hours. The pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 1.5. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0045] A large amount of carbon dioxide was generated in the exhaust gas. By weighing the different products and combining this with ICP detection, the lithium recovery rate and cobalt recovery rate were calculated. The calculated lithium recovery rate was 80.5%, and the cobalt recovery rate was 82.3%.

[0046] The process flow diagram and reaction process diagram of the recovery method in this embodiment are as follows: Figure 1 , Figure 2 As shown, the cobalt powder obtained from the leaching residue is as follows: Figure 3 As shown.

[0047] Example 2:

[0048] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0049] Lithium chloride was used as the molten salt. 6.6 wt% cobalt chloride was added as the chlorine source to the lithium chloride molten salt, and this mixture was thoroughly mixed with 10 wt% positive electrode powder to obtain a mixed salt, which was then added to the electrolytic cell. A high-purity graphite rod (99.9 wt%) was used as the anode, and a titanium plate was used as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The nitrogen flow rate was controlled at 50 ml / min, and the temperature was raised to 700℃. Electrolysis was performed at a constant voltage of 2.1V for 10 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 1.5. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0050] A large amount of carbon dioxide was generated in the exhaust gas. By weighing the different products and combining this with ICP detection, the lithium recovery rate and cobalt recovery rate were calculated. The calculated lithium recovery rate was 95.6%, and the cobalt recovery rate was 97.3%.

[0051] Example 3:

[0052] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0053] Lithium chloride was used as the molten salt. 19.8 wt% cobalt chloride was added as the chlorine source to the lithium chloride molten salt, and this mixture was thoroughly mixed with 30 wt% positive electrode powder to obtain a mixed salt, which was then added to the electrolytic cell. A high-purity graphite rod (99.9 wt%) was used as the anode, and a tungsten rod as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The flow rate of the argon-nitrogen mixed gas was controlled at 50 ml / min, and the temperature was raised to 750℃. Electrolysis was performed at a constant voltage of 2.4V for 21 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 3. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0054] A large amount of carbon dioxide was generated in the exhaust gas. By weighing the different products and combining this with ICP detection, the lithium recovery rate and cobalt recovery rate were calculated. The calculated lithium recovery rate was 98.6%, and the cobalt recovery rate was 98.1%.

[0055] Example 4:

[0056] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0057] Lithium chloride was used as the molten salt. 6.6 wt% cobalt chloride was added as the chlorine source to the lithium chloride molten salt, and this mixture was thoroughly mixed with 10 wt% positive electrode powder to obtain a mixed salt, which was then added to the electrolytic cell. A platinum sheet was used as the anode, and a cobalt rod as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The argon flow rate was controlled at 50 ml / min, and the temperature was raised to 700℃. Electrolysis was performed at a constant voltage of 2.1V for 12 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 2. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0058] Oxygen was detected in the exhaust gas. The lithium and cobalt recovery rates were calculated by weighing different products and combining this with ICP testing. The calculated lithium recovery rate was 95.9%, and the cobalt recovery rate was 97.9%.

[0059] Example 5:

[0060] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0061] Lithium chloride was used as the molten salt. 6.6 wt% cobalt chloride was added as the chlorine source to the lithium chloride molten salt, and this mixture was thoroughly mixed with 10 wt% positive electrode powder to obtain a mixed salt, which was then added to the electrolytic cell. Tin dioxide rods were used as the anode, and molybdenum rods as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The nitrogen flow rate was controlled at 50 ml / min, and the temperature was raised to 700℃. Electrolysis was performed at a constant voltage of 1.8V for 12 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 2. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0062] Oxygen was detected in the exhaust gas. The lithium and cobalt recovery rates were calculated by weighing different products and combining this with ICP testing. The calculated lithium recovery rate was 94.8%, and the cobalt recovery rate was 91.6%.

[0063] Example 6:

[0064] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0065] Lithium chloride was used as the molten salt. 6.6 wt% cobalt chloride was added as the chlorine source to the lithium chloride molten salt, and this mixture was thoroughly mixed with 10 wt% positive electrode powder to obtain a mixed salt, which was then added to the electrolytic cell. A Cu-Ni-Fe alloy rod was used as the anode, and a molybdenum rod as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The flow rate of the argon-nitrogen mixed gas was controlled at 50 ml / min, and the temperature was raised to 680℃. Electrolysis was performed at a constant voltage of 2.1V for 10 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 2. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0066] Oxygen was detected in the exhaust gas. The lithium and cobalt recovery rates were calculated by weighing different products and combining this with ICP testing. The calculated lithium recovery rate was 94.8%, and the cobalt recovery rate was 93.1%.

[0067] Example 7:

[0068] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0069] Lithium chloride was used as the molten salt. 10 wt% cobalt chloride was added as the chlorine source to the lithium chloride molten salt, and this mixture was thoroughly mixed with 15 wt% positive electrode powder to obtain a mixed salt, which was then added to the electrolytic cell. A platinum sheet was used as the anode, and a molybdenum rod as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The argon flow rate was controlled at 50 ml / min, and the temperature was raised to 700℃. Electrolysis was performed at a constant voltage of 1.8V for 10 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 2. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0070] Oxygen was detected in the exhaust gas. The lithium and cobalt recovery rates were calculated by weighing different products and combining this with ICP testing. The calculated lithium recovery rate was 89.7%, and the cobalt recovery rate was 84.5%.

[0071] Comparative Example 1:

[0072] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0073] Lithium chloride was used as the molten salt. 10 wt% cobalt chloride was added as the chlorine source to the lithium chloride molten salt, and this mixture was thoroughly mixed with 15 wt% positive electrode powder to obtain a mixed salt, which was then added to the electrolytic cell. A platinum sheet was used as the anode, and a molybdenum rod as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The argon flow rate was controlled at 50 ml / min, and the temperature was raised to 700℃. Electrolysis was performed at a constant voltage of 1.4V for 10 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 2. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0074] Oxygen was detected in the exhaust gas. The lithium and cobalt recovery rates were calculated by weighing different products and combining this with ICP testing. The calculated lithium recovery rate was 2.1%, and the cobalt recovery rate was 0%.

[0075] Comparative Example 2:

[0076] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0077] Lithium chloride was used as the molten salt. 10 wt% cobalt chloride was added as the chlorine source to the lithium chloride molten salt, and this mixture was thoroughly mixed with 15 wt% positive electrode powder to obtain a mixed salt, which was then added to the electrolytic cell. A platinum sheet was used as the anode, and a molybdenum rod as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The argon flow rate was controlled at 50 ml / min, and the temperature was raised to 630℃. Electrolysis was performed at a constant voltage of 1.8V for 10 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 2. The leached product was filtered. The filtrate was a lithium chloride solution, and the leaching residue was cobalt powder.

[0078] Oxygen was detected in the exhaust gas. The lithium and cobalt recovery rates were calculated by weighing different products and combining this with ICP testing. The calculated lithium recovery rate was 43.2%, and the cobalt recovery rate was 38.3%.

[0079] Comparative Example 3:

[0080] A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis includes the following steps:

[0081] Lithium chloride was used as the molten salt, and it was thoroughly mixed with 10 wt% lithium chloride molten salt cathode powder to obtain a mixed salt, which was then added to the electrolytic cell. A high-purity graphite rod (99.9 wt%) was used as the anode, and a titanium plate as the cathode. A glass bottle containing pure water was used as the tail gas absorption device. The nitrogen flow rate was controlled at 50 ml / min, and the temperature was raised to 700℃. Electrolysis was performed at a constant voltage of 2.1V for 10 hours. Pure water from the tail gas absorption device was used for leaching at room temperature, with the liquid-to-solid ratio controlled at 1.5. The leached product was then filtered. Because cobalt chloride was not added as a chlorine source, the viscosity of the molten salt increased after a period of time due to the formation of high-melting-point compounds such as lithium oxide, resulting in a significant decrease in current efficiency.

[0082] The lithium and cobalt recovery rates were calculated by weighing different products and combining this with ICP testing. The calculated lithium recovery rate was 66.7%, and the cobalt recovery rate was 74.2%.

Claims

1. A method for recovering cobalt and lithium from spent lithium cobalt oxide batteries via molten salt electrolysis, characterized in that, Includes the following steps: Waste lithium cobalt oxide battery cathode powder is mixed with cobalt chloride and added to an electrolytic cell containing lithium chloride molten salt for electrolysis. The molten salt after electrolysis is leached, and the leaching product is then subjected to solid-liquid separation to obtain leaching solution and leaching residue. The leaching solution is a lithium chloride solution, and the leaching residue is cobalt powder. The amount of waste lithium cobalt oxide battery cathode powder added is 5-30 wt% of the mass of lithium chloride molten salt, and the amount of cobalt chloride added is 0.4-0.6 times the molar amount of lithium cobalt oxide in the waste lithium cobalt oxide battery cathode powder; As electrolysis proceeds, waste lithium cobalt oxide battery cathode powder and cobalt chloride are continuously added to the electrolytic cell.

2. The recycling method according to claim 1, characterized in that, The particle size of the cathode powder from waste lithium cobalt oxide batteries should be controlled to be less than 50 μm.

3. The recycling method according to claim 1, characterized in that, The electrolysis temperature is controlled at 650-750℃, and the atmosphere during electrolysis is argon and / or nitrogen.

4. The recycling method according to claim 1, characterized in that, Electrolysis is performed using constant voltage, with the electrolytic cell voltage controlled at 1.5-2.5V. The electrolysis duration is 1.1-1.3 times the theoretical electrolysis time t. The theoretical electrolysis time t is calculated using the following formula: ； Where n is the molar amount of lithium cobalt oxide in the cathode powder of waste lithium cobalt oxide batteries, and I is the average current.

5. The recycling method according to any one of claims 1-4, characterized in that, During electrolysis, pure water is used to absorb the tail gas to obtain a tail gas absorbent solution, and the tail gas absorbent solution is used as the leachate solution during leaching.

6. The recycling method according to any one of claims 1-4, characterized in that, During electrolysis, a metal rod / plate / mesh is used as the cathode, and graphite is used as the anode. The cathode metal is one of molybdenum, tungsten, titanium, or cobalt.

7. The recycling method according to any one of claims 1-4, characterized in that, The leaching time should be controlled at 0.5-2 hours, and the liquid-to-solid ratio should be (1.5-3):

1.

8. The recycling method according to any one of claims 1-4, characterized in that, Lithium chloride solution is evaporated, concentrated, cooled, and crystallized to prepare lithium chloride powder; a portion of the cobalt powder is chlorinated and regenerated and returned to be mixed with the waste lithium cobalt oxide battery cathode powder, with the chlorinated regenerated cobalt powder accounting for 30-40 wt% of the total cobalt powder mass.

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