A method for preferentially extracting lithium from waste lithium batteries by using the ore pulp electrolysis technology

Abstract

This invention discloses a method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology. The method includes: sequentially discharging and disassembling spent lithium batteries to obtain positive electrode sheets or a mixture of positive and negative electrode sheets; calcining the positive electrode sheets or the mixture of positive and negative electrode sheets, and sieving to obtain positive electrode powder or a mixture of positive and negative electrode powder; adding the positive electrode powder or the mixture of positive and negative electrode powder to dilute sulfuric acid and stirring to obtain a slurry; transferring the slurry to an electrolytic cell, electrolyzing the slurry, and filtering to obtain a lithium-ion-rich solution. This method, by adjusting the slurry of spent lithium batteries and adding a suitable electric field, utilizes electrochemical oxidation and electric field migration to promote the migration of lithium ions from the crystal structure of the positive electrode material into the solution, while simultaneously oxidizing and dissolving the metallic lithium deposited on the negative electrode material. This achieves selective lithium extraction under low-acid conditions, while preventing the leaching of other valuable elements besides lithium, thus achieving the goal of preferential lithium extraction.

Description

Technical Field

[0001] This invention relates to the field of waste lithium-ion battery material recycling technology, and in particular to a method for preferentially extracting lithium from waste lithium batteries using slurry electrolysis technology. Background Technology

[0002] With the increasing severity of energy depletion and environmental pollution, lithium-ion batteries are experiencing rapid development in energy applications, particularly in new energy vehicles and energy storage, demonstrating broad market prospects. With the widespread adoption of power lithium-ion batteries, and considering their 5-8 year lifespan, a surge in the retirement of used lithium batteries is inevitable. If a large number of retired lithium-ion batteries cannot be properly recycled and utilized, it will cause serious damage to the ecological environment. At the same time, lithium batteries contain abundant valuable metals such as lithium, iron, phosphorus, copper, and aluminum, representing a huge potential resource with high economic value from recycling. Considering lithium resource reserves and demand, an electric vehicle requires approximately 3-20 kg of lithium. According to the "New Energy Vehicle Industry Development Plan (2021-2035)," by 2050, new energy vehicle sales in my country will reach approximately 20% of total new vehicle sales (estimated at 2.58 million vehicles), and the demand for lithium in electric vehicles will reach 55,000 tons. Although my country has abundant lithium resources, they are mainly concentrated in high-altitude, cold regions such as Qinghai and Tibet. On the one hand, the mining environment is harsh, and on the other hand, local infrastructure is weak. Therefore, although my country's lithium reserves account for 22% of the global total, it heavily relies on imports for lithium ore, currently exceeding 85% dependence. With the rapid development of the new energy vehicle industry, the shortage of lithium resources has become increasingly severe, leading to a rapid rise in lithium prices. The domestic price of battery-grade lithium carbonate has increased from approximately 42,000 yuan / ton at the beginning of 2015 to 360,000 yuan / ton in March 2023, an increase of over 800%. Compared to the increasingly difficult mining and refining of lithium ore, recovering lithium from spent lithium batteries will be one of the important ways to ensure my country's lithium resource security.

[0003] Currently, the recycling methods for spent lithium batteries are mainly divided into two categories: pyrometallurgical and hydrometallurgical processes. Pyrometallurgical processes involve pre-treating the spent lithium batteries by removing the outer casing, then calcining or pyrolyzing the mixed battery materials under an inert gas atmosphere. Organic matter escapes as gas, while most of the low-boiling-point lithium oxide escapes as vapor and is absorbed and recovered with water. Other metals (such as copper, nickel, and cobalt) form alloys, which are subsequently separated using hydrometallurgical techniques. Fluorine and phosphorus in the electrolyte are solidified in the slag. The disadvantage of pyrometallurgical processes is the low overall recovery rate of valuable metals; metals such as aluminum, manganese, and lithium are lost in the slag. Hydrometallurgical processes mainly use inorganic or organic acids to leach the spent battery materials, followed by multi-stage extraction or stepwise precipitation to separate the valuable elements. Compared to pyrometallurgical processes, hydrometallurgical processes have many advantages, including high metal recovery rates, high product purity, low energy consumption, and low emissions. A typical hydrometallurgical process usually includes two steps: wet leaching of the materials and separation and recovery of metal elements from the leaching solution. Because the recycling process often employs multi-stage extraction or stepwise precipitation to separate valuable elements, the overall lithium recovery rate is low (only around 90%). Considering the current high price of lithium-containing materials, adopting preferential lithium extraction processes to improve lithium recovery rates is imperative. For spent lithium iron phosphate batteries, researchers have developed a Na2S2O8 oxidation method for preferential lithium extraction and recovery of LiFePO4. For spent ternary NCM lithium battery materials, Professor Xu Shengming et al. used a controlled carbothermal reduction method to directionally convert NCM materials into Ni-Co alloys, MnO, Li2O, and Li2CO3, and then used H3PO4 solution leaching to preferentially extract Li and Mn. However, the above preferential lithium extraction technologies are complex, require additional reagents, and are costly.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a clean and rapid method for preferentially extracting lithium from waste lithium batteries, so as to improve the overall lithium recovery rate. This invention aims to solve the problems of complex processes, the need to introduce additional reagents, and high costs associated with existing preferential lithium extraction technologies.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology, comprising the following steps:

[0008] Waste lithium batteries are discharged and disassembled in sequence to obtain positive electrode sheets or a mixture of positive and negative electrode sheets;

[0009] The positive electrode sheet or the mixture of the positive and negative electrode sheets is calcined and sieved to obtain positive electrode powder or positive and negative electrode mixed powder.

[0010] The positive electrode powder or the positive and negative electrode mixed powder is added to dilute sulfuric acid and stirred to obtain a slurry;

[0011] The slurry is transferred to an electrolytic cell, electrolyzed, and then filtered to obtain a lithium-ion-rich solution.

[0012] Optionally, the waste lithium battery is one or more of ternary lithium-ion batteries, lithium iron phosphate batteries, and lithium cobalt oxide batteries.

[0013] Optionally, the calcination temperature is 500℃~600℃, the calcination time is 2 hours~6 hours, and the heating rate is 5℃ / min~10℃ / min.

[0014] Optionally, the step of adding the positive electrode powder or the positive and negative electrode mixed powder to dilute sulfuric acid specifically includes:

[0015] The additive is mixed with dilute sulfuric acid to obtain a mixed solution of sulfuric acid and additive;

[0016] The positive electrode powder or the positive and negative electrode mixed powder is added to the mixed solution of sulfuric acid and additives.

[0017] Optionally, the additive is a chemical reagent with oxidizing properties;

[0018] The solid-liquid mass-volume ratio of the positive electrode powder or the positive and negative electrode mixed powder to the mixed solution of sulfuric acid and additives is 1:(5~25).

[0019] The concentration of the dilute sulfuric acid is 0.1 mol / L to 0.5 mol / L; the concentration of the additive in the mixed solution of sulfuric acid and additive is 0.05 mol / L to 0.2 mol / L.

[0020] The additive is one or more of hydrogen peroxide, potassium permanganate, sodium sulfate, sodium sulfite, and sodium persulfate.

[0021] Optionally, the step of transferring the slurry to an electrolytic cell, electrolyzing the slurry, and then filtering to obtain a lithium-ion-rich solution specifically includes:

[0022] An electrolytic cell and an external power supply are provided. The electrolytic cell includes a cathode, an anode, and a tank body. The external power supply includes a negative electrode and a positive electrode. The cathode is connected to the negative electrode, and the anode is suspended and inserted into the tank body and connected to the positive electrode. The slurry is transferred into the tank body. After the external power supply is turned on, the slurry is electrolyzed and filtered to obtain a lithium-ion-rich solution.

[0023] Optionally, the electrolytic cell further includes a diaphragm to separate the cathode chamber and the anode chamber, to suspend the anode in the anode chamber, and to transfer the slurry to the anode chamber;

[0024] The electrolytic cell also includes a stirrer, which is turned on to stir the slurry.

[0025] Optionally, the diaphragm is selected from ion exchange membrane and industrial filter cloth;

[0026] The cathode and the anode are each independently selected from one of the following: graphite electrode, glassy carbon electrode, titanium-based ruthenium-iridium coated electrode, and titanium-based iridium-tantalum coated electrode.

[0027] Optionally, the external power supply is a DC power supply, and the electrolysis mode can be either constant current electrolysis or controlled potential electrolysis.

[0028] When electrolyzing the slurry using a constant current, the anode current density is 4 mA / cm². 2 ~8 mA / cm 2 .

[0029] When electrolyzing the slurry using a controlled potential, the voltage used is 2.0 V to 4.0 V.

[0030] Optionally, the electrolysis time is 3 to 24 hours.

[0031] Beneficial Effects: This invention discloses a method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology. This method involves adjusting the slurry of spent lithium batteries and adding a suitable electric field. Through electrochemical oxidation and electric field migration, lithium ions in the positive electrode material of the spent lithium batteries migrate from the crystal structure into the solution, while simultaneously oxidizing and dissolving the metallic lithium deposited on the negative electrode material. This invention achieves selective lithium extraction under low-acid conditions by controlling the pH value of the solution and the strength of the applied electric field, while preventing the leaching of other valuable elements besides lithium, thereby achieving the goal of preferential lithium extraction.

[0032] This invention uses only low-concentration sulfuric acid, has a small applied electric field voltage, operates in a mild environment, and produces no wastewater or exhaust gas. It has low requirements for process equipment, a good operating environment, low raw material consumption, and high economic benefits.

[0033] The present invention features a simple process, short flow, and high comprehensive recycling rate, which is conducive to large-scale industrial production. It can be effectively integrated with existing battery recycling production lines, meets current industry needs, and has good application prospects and practical value. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the apparatus provided by the present invention for preferentially extracting lithium from waste lithium batteries. Detailed Implementation

[0035] This invention provides a method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] This invention provides a method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology, comprising the following steps:

[0037] Step 1: Discharge and disassemble the waste lithium batteries in sequence to obtain positive electrode sheets or a mixture of positive and negative electrode sheets;

[0038] Step 2: Calcine the positive electrode sheet or the mixture of the positive and negative electrode sheets, and sieve it to obtain positive electrode powder or positive and negative electrode mixed powder.

[0039] Step 3: Add the positive electrode powder or the positive and negative electrode mixed powder to dilute sulfuric acid and stir to obtain a slurry;

[0040] Step 4: Transfer the slurry to an electrolytic cell, electrolyze the slurry, and then filter to obtain a lithium-ion-rich solution.

[0041] This embodiment of the method involves preparing a slurry of waste lithium battery materials and adding a suitable electric field. Through electrochemical oxidation and electric field migration, lithium ions in the positive electrode material of the waste lithium battery migrate from the crystal structure into the solution. At the same time, the metallic lithium deposited on the negative electrode material is oxidized and dissolved. This embodiment achieves selective extraction of lithium under low acid conditions by controlling the pH value of the solution and the strength of the applied electric field, while preventing other valuable elements besides lithium from being leached out, thereby achieving the purpose of preferential lithium extraction.

[0042] This embodiment uses only low-concentration sulfuric acid, has a small applied electric field voltage, a mild operating environment, and no wastewater or exhaust gas emissions; it has low requirements for process equipment, a good operating environment, low raw material consumption, and high economic benefits.

[0043] This embodiment features a simple process, short flow, and high comprehensive recycling rate, which is conducive to large-scale industrial production. It can be effectively integrated with existing battery recycling production lines, meets current industry needs, and has good application prospects and practical value.

[0044] In step one, the waste lithium batteries are discharged and disassembled. The disassembly process can be carried out in two ways. One is precise disassembly, which uses a solvent (such as DMC solvent) to clean the electrode plates to remove residual electrolyte. Then, the positive and negative electrode plates can be separated by manual sorting or color sorting technology to obtain the positive electrode plate. The other is conventional disassembly, which directly crushes the discharged waste lithium batteries to obtain a mixture of positive and negative electrode plates.

[0045] In one embodiment, the waste lithium battery can be one or more of ternary lithium-ion batteries, lithium iron phosphate batteries, and lithium cobalt oxide batteries.

[0046] In step two, the specific steps are as follows: place the positive electrode sheet or the mixture of positive and negative electrode sheets obtained in step one into a vacuum drying oven for drying; place the dried positive electrode sheet or the mixture of positive and negative electrode sheets into a crucible and place it in a high-temperature furnace for calcination to remove the binder (such as PVDF) and conductive agent (such as conductive carbon), thereby separating the electrode sheet from the current collector (such as aluminum foil or copper foil); and sieve to obtain positive electrode powder or positive and negative electrode mixed powder.

[0047] In one embodiment, the drying temperature can be 60 ℃ to 120 ℃, and the drying time can be 4 hours to 24 hours.

[0048] In one embodiment, the calcination temperature can be 500 ℃~600 ℃ (e.g., 500 ℃, 550 ℃ or 600 ℃), the calcination time is 2 hours~6 hours (e.g., 2 hours, 3 hours, 4 hours, 5 hours or 6 hours), and the heating rate is 5 ℃ / min~10 ℃ / min, that is, the temperature is raised to 500 ℃~600 ℃ at this heating rate.

[0049] In step three, concentrated industrial sulfuric acid can be diluted with water to prepare dilute sulfuric acid of a certain concentration. A certain amount of additives can also be added; these additives are one or more oxidizing chemical reagents such as hydrogen peroxide, potassium permanganate, sodium sulfate, and sodium sulfite.

[0050] The positive electrode powder or the positive and negative electrode mixed powder is added to dilute sulfuric acid and stirred thoroughly to obtain a slurry.

[0051] In one embodiment, the concentration of the dilute sulfuric acid is 0.1 mol / L to 0.5 mol / L.

[0052] In one embodiment, the solid-liquid ratio (solid mass: acid volume) of the positive electrode powder or the positive and negative electrode mixed powder to the dilute sulfuric acid is 1:(5~25).

[0053] In one embodiment, the step of adding the positive electrode powder or the positive and negative electrode mixed powder to dilute sulfuric acid specifically includes:

[0054] Dilute sulfuric acid is mixed with additives to obtain a mixed solution of sulfuric acid and additives;

[0055] The positive electrode powder or the positive and negative electrode mixed powder is added to the mixed solution of sulfuric acid and additives.

[0056] In this embodiment, adding a certain amount of oxidizing additive (i.e., oxidizing chemical reagent) to dilute sulfuric acid can promote the leaching of lithium and at the same time oxidize valuable metal ions from a low valence state to a high valence state, leaving them in the residue.

[0057] Further, the concentration of the dilute sulfuric acid is 0.1 mol / L to 0.5 mol / L, the amount of additive in the mixed solution of sulfuric acid and additive is 0.05 mol / L to 0.2 mol / L, and the solid-liquid mass-volume ratio of the positive electrode powder or the positive and negative electrode mixed powder to the mixed solution of sulfuric acid and additive is 1:(5~25).

[0058] In step four, in one embodiment, the step of transferring the slurry to an electrolytic cell, electrolyzing the slurry, and then filtering to obtain a lithium-ion-rich solution specifically includes:

[0059] An electrolytic cell and an external power supply are provided. The electrolytic cell includes a cathode, an anode, and a cell body (the cell body can be graphite, and the graphite can be used as the cathode). The external power supply includes a negative electrode and a positive electrode. The cathode is connected to the negative electrode, and the anode is suspended and inserted into the cell body and connected to the positive electrode. The slurry is transferred into the cell body. After the external power supply is turned on, the slurry is electrolyzed, and then filtered to obtain a lithium-ion-rich solution.

[0060] In one embodiment, the electrolytic cell further includes a diaphragm that separates the cathode chamber and the anode chamber, suspends the anode in the anode chamber, and transfers the slurry to the anode chamber;

[0061] The electrolytic cell also includes a stirrer, which is turned on to stir the slurry.

[0062] In other words, combining Figure 1As shown, step four specifically includes: using an electrolytic cell, connecting the cathode to the negative terminal of an external power supply, separating the cathode chamber and the anode chamber using a diaphragm, suspending the anode in the anode chamber and connecting it to the positive terminal of the external power supply, transferring the slurry to the anode chamber; turning on the stirrer to stir the slurry in the anode chamber; connecting the external power supply to electrolyze the slurry, and filtering to obtain a lithium-ion-rich solution. The spent lithium batteries that have had lithium preferentially removed are sent for further leaching to comprehensively recover other valuable elements.

[0063] The specific reaction principle is as follows: under the action of an external electric field, the anode connected to the positive terminal of the external power supply has an oxidation effect. Under the action of stirring, the slurry comes into contact with the anode. The metallic lithium in the negative electrode powder is oxidized into lithium ions, and the valuable metal elements in the positive electrode powder, such as Ni, Co, Mn, Fe, etc., are oxidized from low-valence metal ion state to high-valence metal ion state. They are not easily dissolved and enter the slag. Under the action of electric field migration, the dissolved lithium ions selectively pass through the diaphragm and enter the cathode chamber to be enriched.

[0064] In one embodiment, an ion exchange membrane or industrial filter cloth is used as the diaphragm. Further, the ion exchange membrane is a cation exchange membrane. Further, the industrial filter cloth is a polyester filter cloth or a polypropylene filter cloth.

[0065] In one embodiment, the external power supply is a DC power supply, and electrolysis is performed using constant current or controlled voltage; when electrolyzing the slurry using constant current, the anode current density is selected as 4 mA / cm². 2 ~8 mA / cm 2 Electrolysis can be performed using any value within the range; when electrolyzing the slurry using a controlled potential, the voltage used can be any value within the range of 2.0 V to 4.0 V.

[0066] In one embodiment, the electrolysis time is any value within the range of 3 hours to 24 hours;

[0067] In one embodiment, mechanical stirring or ultrasonic stirring is used to mix the slurry evenly.

[0068] In one embodiment, the cathode and the anode are each independently selected from one of the following inert electrodes: graphite electrode, glassy carbon electrode, titanium-based ruthenium-iridium coated electrode, and titanium-based iridium-tantalum coated electrode.

[0069] The present invention will be further described below through several specific embodiments.

[0070] Example 1

[0071] Waste NCM523 lithium batteries were discharged and precisely disassembled. The obtained positive electrode sheets were cleaned using 98% DMC solvent at a liquid-to-solid ratio (DMC solvent volume: waste NCM523 lithium battery positive electrode sheet mass) of 10:1 to remove residual electrolyte. The cleaned positive electrode sheets were then dried in a vacuum drying oven at 120℃ for 4 hours. The dried positive electrode sheets were then placed in a crucible and placed in a muffle furnace, where they were calcined at 500℃ for 2 hours to remove PVDF and conductive carbon, thereby separating the positive electrode sheet from the current collector (aluminum foil or copper foil). The resulting positive electrode powder was obtained by sieving. Analysis showed that the positive electrode powder contained 6.11 wt% lithium, 39.37 wt% nickel, and 15.06 wt% cobalt.

[0072] Prepare a 0.5 mol / L dilute sulfuric acid solution by dissolving 98% concentrated sulfuric acid in 300 mL of water. Add hydrogen peroxide solution (0.62 wt%) to the dilute sulfuric acid and stir thoroughly to obtain a mixed solution of sulfuric acid and hydrogen peroxide.

[0073] Weigh 30 g of waste NCM523 lithium battery positive electrode powder, and mix it thoroughly with the above-prepared sulfuric acid and hydrogen peroxide mixed solution to form a slurry, according to a liquid-to-solid ratio (volume of the mixed solution of sulfuric acid and hydrogen peroxide: mass of waste NCM523 lithium battery positive electrode powder) of 10:1.

[0074] A graphite electrolytic cell is used, with the negative terminal of the external power supply serving as the cathode. A graphite electrode is suspended and inserted into the electrolytic cell, and connected to the positive terminal of the external power supply as the anode.

[0075] The prepared slurry was placed in an electrolytic cell and stirred at a speed of 300 r / min to prevent solids from settling. An external power supply was then connected, and the anolyte current density for slurry electrolysis was controlled at 4 mA / cm². 2 The electrolysis time was 24 hours. After electrolysis, the slurry in the electrolytic cell was filtered to obtain slag and a lithium-rich solution. The concentration of ions in the lithium-rich solution was determined by ICP. The lithium ion concentration in the lithium-rich solution was found to be 6.09 g / L, with a lithium leaching rate of 99.70%. Nickel, cobalt, and manganese remained in the slag and were essentially not leached, with leaching rates of 10.5%, 14.7%, and 1.4%, respectively.

[0076] Example 2

[0077] Waste NCM523 lithium batteries were discharged and precisely disassembled. The obtained positive electrode sheets were cleaned using 98% DMC solvent at a liquid-to-solid ratio (DMC solvent volume: waste NCM523 lithium battery positive electrode sheet mass) of 10:1 to remove residual electrolyte. The cleaned positive electrode sheets were then dried in a vacuum drying oven at 120 °C for 4 hours. The dried positive electrode sheets were then placed in a crucible and placed in a muffle furnace, where they were calcined at 500 °C for 2 hours to remove PVDF and conductive carbon, thereby separating the positive electrode sheet from the current collector (aluminum foil or copper foil). The resulting positive electrode powder was obtained by sieving. Analysis showed that the positive electrode powder contained 6.11 wt% lithium, 39.37 wt% nickel, and 15.06 wt% cobalt.

[0078] Prepare a 0.25 mol / L dilute sulfuric acid solution by dissolving 98% concentrated sulfuric acid in 240 mL of water. Add hydrogen peroxide solution (0.62 wt%) to the dilute sulfuric acid solution and stir thoroughly to obtain a mixed solution of sulfuric acid and hydrogen peroxide.

[0079] Weigh 30g of waste NCM523 lithium battery positive electrode powder, and mix it with the prepared sulfuric acid and hydrogen peroxide mixed solution according to the liquid-to-solid ratio (volume of mixed solution of sulfuric acid and hydrogen peroxide: mass of waste NCM523 lithium battery positive electrode powder) = 8:1. Stir thoroughly to form a slurry.

[0080] A graphite electrolytic cell is used, with the negative terminal of the external power supply serving as the cathode. A polyester filter cloth is used as a diaphragm to separate the anode chamber. A graphite electrode is suspended and inserted into the anode chamber of the electrolytic cell, and connected to the positive terminal of the external power supply as the anode.

[0081] The prepared slurry was placed in the anode chamber of the electrolytic cell and stirred at a stirring intensity of 300 r / min to prevent solids from settling. After the liquid levels in the anode and cathode chambers were balanced, an external power supply was connected, and the anode current density for slurry electrolysis was controlled at 6 mA / cm². 2 The electrolysis time was 24 hours. After electrolysis, the slurry in the electrolytic cell was filtered to obtain slag and a lithium-rich solution. The concentration of each ion in the lithium-rich solution was determined by ICP. The lithium ion concentration in the lithium-rich solution was found to be 5.83 g / L, with a lithium leaching rate of 95.45%. Nickel, cobalt, and manganese remained in the slag and were not leached, with leaching rates of 5.6%, 7.3%, and 0.7%, respectively.

[0082] Example 3

[0083] Waste lithium iron phosphate batteries were discharged and precisely disassembled. The obtained positive electrode sheets were cleaned using 98% DMC solvent at a liquid-to-solid ratio (DMC solvent volume: waste lithium iron phosphate battery positive electrode sheet mass) of 10:1 to remove residual electrolyte. The cleaned positive electrode sheets were then dried in a vacuum drying oven at 120 °C for 4 hours. The dried positive electrode sheets were then placed in a crucible and placed in a muffle furnace, where they were calcined at 550 °C for 5 hours to remove PVDF and conductive carbon, thereby separating the positive electrode sheet from the current collector (aluminum foil or copper foil). The resulting lithium iron phosphate positive electrode powder was obtained by sieving. Analysis showed that the positive electrode powder contained 4.23 wt% lithium, 32.84 wt% iron, and 18.73 wt% P.

[0084] Prepare 100 mL of dilute sulfuric acid with a concentration of 0.4 mol / L, add 0.05 mol / L anhydrous sodium sulfate, and then add 1.8 mL of 30% H2O2 solution. Mix well.

[0085] Weigh 10 g of waste lithium iron phosphate cathode powder according to the liquid-to-solid ratio (volume of sulfuric acid solution: mass of waste lithium iron phosphate cathode powder) = 10:1, mix it with the sulfuric acid mixed solution prepared above, and stir thoroughly for 30 min to obtain a slurry.

[0086] A graphite electrolytic cell is used, with the negative terminal of the external power supply serving as the cathode. A polyester filter cloth is used as a diaphragm to separate the anode chamber. A graphite electrode is suspended and inserted into the anode chamber of the electrolytic cell, and connected to the positive terminal of the external power supply as the anode.

[0087] The prepared slurry was placed in the anode chamber of the electrolytic cell and stirred at a stirring intensity of 300 r / min to prevent solids from settling. After the liquid levels in the anode and cathode chambers were balanced, an external power supply was connected, and potentiometric electrolysis was performed using a controlled voltage of 3.25 V for 3 hours. After electrolysis, the slurry in the electrolytic cell was filtered to obtain slag and a lithium-rich solution. The concentrations of various ions in the lithium-rich solution were determined by ICP. The results showed that the lithium ion concentration in the lithium-rich solution was 4.21 g / L, the Fe concentration was 0.976 g / L, and the phosphate concentration was 0.46 g / L, with a lithium leaching rate of 91.90%. Iron and phosphorus remained in the slag and were not leached, with leaching rates of 2.73% and 2.26%, respectively.

[0088] In summary, this invention provides a method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology. This method involves adjusting the slurry of spent lithium batteries and adding a suitable electric field. Through electrochemical oxidation and electric field migration, lithium ions in the positive electrode material of the spent lithium batteries migrate from the crystal structure into the solution, while simultaneously oxidizing and dissolving the metallic lithium deposited on the negative electrode material. This invention achieves selective lithium extraction under low-acid conditions by controlling the pH value of the solution and the strength of the applied electric field, while preventing the leaching of other valuable elements besides lithium, thus achieving the goal of preferential lithium extraction.

[0089] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology, characterized in that, Includes the following steps: Waste lithium batteries are discharged and disassembled in sequence to obtain positive electrode sheets or a mixture of positive and negative electrode sheets; The positive electrode sheet or the mixture of the positive and negative electrode sheets is calcined and sieved to obtain positive electrode powder or positive and negative electrode mixed powder. The positive electrode powder or the positive and negative electrode mixed powder is added to dilute sulfuric acid and stirred to obtain a slurry; The slurry is transferred to an electrolytic cell, electrolyzed, and then filtered to obtain a lithium-ion-rich solution. The step of adding the positive electrode powder or the positive and negative electrode mixed powder to dilute sulfuric acid specifically includes: The additive is mixed with dilute sulfuric acid to obtain a mixed solution of sulfuric acid and additive; The positive electrode powder or the positive and negative electrode mixed powder is added to the mixed solution of sulfuric acid and additives; The solid-liquid mass-volume ratio of the positive electrode powder or the positive and negative electrode mixed powder to the mixed solution of sulfuric acid and additives is 1:(5~25); The concentration of the dilute sulfuric acid is 0.1 mol / L to 0.5 mol / L, and the concentration of the additive in the mixed solution of sulfuric acid and additive is 0.05 mol / L to 0.2 mol / L. The additive is one or more of hydrogen peroxide, potassium permanganate, and sodium persulfate; The steps of transferring the slurry to an electrolytic cell, electrolyzing the slurry, and filtering to obtain a lithium-ion-rich solution specifically include: An electrolytic cell and an external power supply are provided. The electrolytic cell includes a cathode, an anode, and a cell body, and the cell body is made directly of graphite and serves directly as the cathode. The external power supply includes a negative electrode and a positive electrode; the cathode is connected to the negative electrode, the anode is suspended and inserted into the tank and connected to the positive electrode, and the slurry is transferred into the tank; after the external power supply is turned on, the slurry is electrolyzed and filtered to obtain a lithium-ion-rich solution; The external power supply is a DC power supply, and the electrolysis mode is constant current electrolysis, with an anode current density of 4 mA / cm². 2 ~8mA / cm 2 .

2. The method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology according to claim 1, characterized in that, The waste lithium batteries are one or more of the following: ternary lithium-ion batteries, lithium iron phosphate batteries, and lithium cobalt oxide batteries.

3. The method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology according to claim 1, characterized in that, The calcination temperature is 500℃~600℃, the calcination time is 2 hours~6 hours, and the heating rate is 5℃ / min~10℃ / min.

4. The method for preferentially extracting lithium from spent lithium batteries using slurry electrolysis technology according to claim 1, characterized in that, The electrolysis time is 3 to 24 hours.

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