A method for recycling waste lithium battery cathode material by oxalic acid cycle and lithium hydroxide co-production

Abstract

The application discloses a method for recycling waste lithium battery positive electrode materials by oxalic acid circulation and lithium hydroxide co-production. The method uses oxalic acid solution to leach the waste lithium battery positive electrode materials, so that the valuable metals are precipitated in the form of oxalate, after solid-liquid separation, the lithium oxalate solution is introduced into an integrated electrochemical recycling system. The system is provided with an ion separation chamber filled with anion exchange resin between the cathode chamber and the anode chamber in the electrolytic cell, which constitutes Li + purifier and H + Traps: the resin fixes oxalate on one hand, promotes Li + dissociation, on the other hand, captures and neutralizes H + migrated from the anode in situ to generate oxalic acid; at the same time, Li + goes through the cathode side cation exchange membrane, and combines with OH ‑ generated by electrolysis to form a lithium hydroxide solution. The regenerated oxalic acid solution can be used for leaching, and the oxalic acid reagent circulation is realized, and the high-purity lithium hydroxide product significantly improves the overall process economy.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of waste battery positive material recycling, and particularly relates to a waste lithium battery positive material recycling method for oxalic acid circulation and lithium hydroxide co-production. BACKGROUND

[0002] With the development of new energy automobile industry, more and more lithium ion batteries enter the scrap stage, and the recycling of waste lithium ion batteries becomes a new challenge in the field of resources and environment. The positive material is rich in valuable metals such as lithium, nickel, cobalt and manganese, and is the most valuable part of the battery. Hydrometallurgy is the mainstream technology for recycling waste lithium ion battery positive material, among which, the inorganic acid (such as sulfuric acid) leaching-precipitation-extraction process is relatively mature, but there are still obvious drawbacks: (1) the strong acid system has strong corrosion and poor selectivity to metals, and subsequent metal separation needs to be realized through a complex solvent extraction step, which has long process, large reagent consumption and high cost; (2) there are many impurity ions in the leaching solution, and finally lithium is usually recycled in the form of lithium carbonate, which has low economic added value.

[0003] In view of the above problems, researchers have proposed an organic acid leaching method. Oxalic acid is concerned because of its good selectivity precipitation effect on transition metal ions, which can realize one-step separation of lithium and metals such as cobalt, nickel and manganese, and simplify the process flow. However, the large amount of oxalic acid consumed in the reaction cannot be recycled, resulting in the problem of high cost; at the same time, the lithium product usually exists in the form of lithium oxalate, which has much lower commercial value than battery-grade lithium hydroxide or lithium carbonate, and the overall economic benefit of the process is low.

[0004] Therefore, it is of great significance to develop a waste lithium ion battery positive material recycling method which can not only realize the recycling of reagents to reduce cost, but also directly produce high-value lithium products, for promoting the industrialization development of waste lithium battery recycling technology. SUMMARY

[0005] In order to solve the problems in the prior art, the application provides a waste lithium battery positive material recycling method for oxalic acid circulation and lithium hydroxide co-production. The method uses oxalic acid solution to leach the layered positive material of waste lithium ion battery, so that the valuable metals are precipitated in the form of oxalate, and lithium exists in the form of lithium oxalate in the solution. After filtration, the oxalic acid metal salt precipitate and the lithium oxalate solution are separated, and the obtained lithium oxalate solution is introduced into an integrated electrochemical recycling and separation system for treatment, so that the lithium oxalate is converted into high-value lithium hydroxide and oxalic acid solution. The regenerated oxalic acid solution can be used for leaching of waste lithium battery positive material, and the final product is high-purity lithium hydroxide, which has higher commercial value than lithium oxalate or lithium carbonate.

[0006] In order to achieve the above application purposes, the application provides the following technical solutions:

[0007] A method for recycling waste lithium battery cathode material by oxalic acid cycle and lithium hydroxide co-production, comprising the following steps:

[0008] (1) mixing the waste lithium battery cathode material with oxalic acid solution, stirring and reacting to obtain a mixed system containing insoluble metal oxalate and lithium oxalate solution; solid-liquid separation to obtain metal oxalate precipitate and lithium oxalate leaching solution;

[0009] (2) introducing the lithium oxalate leaching solution into the ion separation chamber of the electrochemical recycling device, filling the ion separation chamber with anion exchange resin, starting the electrochemical recycling device, and collecting the obtained lithium hydroxide after the treatment is completed; the regenerated oxalic acid solution can be reused for the leaching of the waste lithium battery cathode material in step (1).

[0010] Further, in step (1), the waste lithium battery cathode material is at least one of lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium manganate (LMO), and mixtures thereof.

[0011] Further, in step (1), the concentration of the oxalic acid solution is 0.1 mol / L-3 mol / L; the molar ratio of the waste lithium battery cathode material to the oxalic acid solution is 1-3, and the liquid-solid ratio is 10-30 mL / g.

[0012] Further, in step (1), the stirring reaction is carried out at a speed of 100-2000 rpm and a temperature of 60-100°C for 1-5h.

[0013] Further, in step (1), the solid-liquid separation can be carried out by suction filtration, pressure filtration or centrifugal separation.

[0014] Further, the metal oxalate precipitate in step (1) is heat treated at 400-600°C for 1-3h to obtain the corresponding metal oxide or precursor.

[0015] Further, the lithium oxalate leaching solution in step (1) is pre-concentrated to a lithium ion concentration of not less than 2 g / L before entering the ion separation chamber of the electrochemical recycling device in step (2).

[0016] Further, in step (2), the anion exchange resin includes strong base anion exchange resin and weak base anion exchange resin; the filling amount of the anion exchange resin in the ion separation chamber is 1-10 g / cm 2 .

[0017] The strong base anion exchange resin contains a quaternary ammonium group -NR3OH in its structure, and R is a hydrocarbon group; specific strong base 717 anion exchange resin, ultra-pure water polishing resin MB-106UP, etc.

[0018] The weak base anion exchange resin structure contains primary amino group -NH2, secondary amino group -NHR or tertiary amino group -NR2, and R is a hydrocarbon group; specifically, D301 macroporous weak base styrene anion exchange resin, D453 macroporous weak base styrene anion exchange resin, etc. can be selected.

[0019] Further, in step (2), the electrochemical recovery device comprises an anode chamber, a cathode chamber and an ion separation chamber between the two, a first cation exchange membrane is arranged between the anode chamber and the ion separation chamber, a second cation exchange membrane is arranged between the cathode chamber and the ion separation chamber, the ion separation chamber is filled with anion exchange resin, and a liquid inlet and a liquid outlet are arranged for the lithium oxalate solution to be treated and the regenerated oxalic acid solution to be discharged, respectively. The place where the electrochemical reaction occurs is called an electrolytic cell, and flow channels for uniform distribution of electrolyte are arranged on the anode plate and / or the cathode plate of the electrolytic cell.

[0020] The electrolyte in the anode chamber and the cathode chamber is one of water, dilute acid or dilute alkali.

[0021] The anode chamber contains an anode catalyst, which is a material with good oxidation performance, including but not limited to one of Fe, Co, Ni, Cu, Zr, Pd, Ru, Ir, Au, C and corresponding metal oxides or metal alloy materials.

[0022] The cathode chamber contains a cathode catalyst, which is a material with good reduction performance, including but not limited to one of Fe, Co, Ni, Cu, Mn, Pd, Ru, Ir, Au, Pt, C and corresponding metal oxides or metal alloy materials.

[0023] The first cation exchange membrane and the second cation exchange membrane are one of sulfonic acid type cation exchange membrane or carboxylic acid type cation exchange membrane, and the first cation exchange membrane and the second cation exchange membrane can be the same or different.

[0024] The current density of the electrochemical recovery device when it is running is 1-200 mA / cm 2 , the voltage is 0.1-30 V, and the reaction potential is 2-10 V. Preferably, the current density is 8 mA cm -2 , and the voltage is 2-8 V.

[0025] When the electrochemical recovery device is running, H + generated by electrolysis of water in the anode chamber passes through the first cation exchange membrane into the ion separation chamber, and combines with C2O4 2- in the lithium oxalate leaching solution to generate an oxalic acid solution; at the same time, Li +Crossing the second cation exchange membrane into the cathode chamber, combine with OH- produced by electrolysis of water in the cathode chamber - Lithium hydroxide solution is generated.

[0026] The method provided by the application is used for leaching treatment of the positive material of the waste lithium ion battery by using an oxalic acid solution, and separates out an oxalic acid metal salt precipitate and a lithium oxalate solution. The obtained lithium oxalate solution is introduced into an integrated electrochemical recycling and separation system for treatment. The system is provided with an ion separation chamber between an anode chamber and a cathode chamber of a water electrolysis unit. Strong base or weak base anion exchange resin is filled in the ion separation chamber, and the strong base anion exchange resin is preferred, so that a Li + The purifier and H + The trap. The resin dissociates Li + by fixing oxalate, on the one hand, and captures and neutralizes H + in situ by using oxalate, on the other hand, so as to create perfect conditions for exclusive migration of Li + . The physical and chemical properties of different ion exchange resins are ingeniously used to realize high-selectivity electrically-driven migration and purification of specific ions (Li + ). During operation of the electrochemical recycling device, protons (H + ) generated by the anode electrolyte (pure water) migrate to the ion separation module through the first cation exchange membrane, and combine with oxalate ions (C2O4 2- ) to generate an oxalic acid solution. Meanwhile, lithium ions (Li + ) in the ion separation module cross the second cation exchange membrane into the cathode chamber, combine with hydroxyl ions (OH - ) generated by electrolysis of water in the cathode chamber to form a high-purity lithium hydroxide solution. The regenerated oxalic acid solution can be returned to be used for leaching of the positive material of the waste lithium battery, so as to realize recycling of the reagent.

[0027] The recycling method provided by the application has a lithium hydroxide product yield of more than 70%, a purity of 98%-99%, and a oxalic acid recovery rate of 100%.

[0028] Compared with the prior art, the application has the beneficial effects that:

[0029] 1. The application uses oxalic acid as a leaching agent, compared with the traditional sulfuric acid / hydrochloric acid method for leaching all metals to obtain a mixed solution of lithium, nickel, cobalt and manganese, and subsequent separation and purification of various metals must rely on a complex, expensive and possibly organic-polluted multistage solvent extraction process. The oxalic acid leaching uses oxalate (C2O4 2-The highly selective precipitation effect of transition metal ions enables liquid-solid separation in one step: transition metals (Ni, Co, Mn, etc.) precipitate out as oxalate, while lithium remains in solution as soluble lithium oxalate (Li2C2O4). The selective precipitation characteristic simplifies the separation process.

[0030] 2. Through integrated electrochemical conversion, consuming only water and electricity, the two processes of oxalic acid regeneration and lithium hydroxide synthesis are cleverly combined into one. Under energized conditions, one side of the device (the ion separation chamber) separates the oxalate ions (C2O4) from lithium oxalate (Li2C2O4). 2- The protons are then used to regenerate oxalic acid (H₂C₂O₄), which can be returned to the leaching section for reuse; on the other side (cathode chamber), lithium ions (Li₂C₂O₄) are protonated and regenerated into oxalic acid (H₂C₂O₄), which can be returned to the leaching section for reuse; the other side (cathode chamber) then uses lithium ions (Li + The oxalic acid reagent is converted into lithium hydroxide (LiOH), realizing the internal circulation of oxalic acid reagent and the direct production of high-value lithium hydroxide.

[0031] 3. In this invention, an appropriate amount of anion exchange resin, preferably a strong-base anion exchange resin, is filled into the ion separation chamber, thus ingeniously constructing a Li... + Purifier and H + Traps. The resin, by immobilizing oxalate ions, on the one hand, dissociates Li... + On the other hand, oxalate is used to capture and neutralize H in situ. + , for Li + The exclusive migration of this material creates perfect conditions. By skillfully utilizing the physicochemical properties of different ion exchange resins, the exclusive migration of specific ions (Li) is achieved. + Highly selective electrodriven migration and purification.

[0032] 4. The electrochemical process takes place at room temperature or low temperature, resulting in relatively low energy consumption. The reaction is electrically driven, making it easy to couple with renewable energy sources and meeting green and low-carbon requirements. The cation exchange membrane provides a highly efficient separation method, helping to obtain high-purity lithium hydroxide products and avoiding the introduction of new impurities. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of a method for recycling waste lithium battery cathode materials by co-producing oxalic acid and lithium hydroxide according to the present invention.

[0034] Figure 2 This is a simplified structural diagram of the electrochemical recovery device used in this invention.

[0035] Figure 3 A photograph of lithium oxalate solution (left) and cobalt oxalate powder (right) produced by leaching waste lithium cobalt oxide cathode material with oxalic acid.

[0036] Figure 4The lithium-ion yield and Faraday efficiency on the cathode side of the battery when the ion separation chambers of Examples 1-4 are filled with different substances.

[0037] Figure 5 The time-voltage curves of the batteries are shown for the ion separation chambers of Examples 2 and Comparative Examples 1-3 when different substances are filled.

[0038] Figure 6 The lithium-ion yield and Faraday efficiency on the cathode side of the battery when the ion separation chamber of Examples 2 and Comparative Examples 1-3 are filled with different substances. Detailed Implementation

[0039] The technical solutions in the implementation of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their application scope. Based on this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention patent.

[0040] This invention provides a method for recycling waste lithium-ion battery cathode materials through the co-production of oxalic acid and lithium hydroxide, such as... Figure 1 As shown, oxalic acid solution is used to leach layered cathode materials from waste lithium-ion batteries, causing valuable metals to precipitate in the form of oxalate, while lithium exists in the solution as lithium oxalate. The oxalate metal salt precipitate and lithium oxalate solution are separated by filtration. The resulting lithium oxalate solution is then introduced into an integrated electrochemical recycling and separation system for processing, converting lithium oxalate into high-value lithium hydroxide and oxalic acid solution. The regenerated oxalic acid solution can be reused for leaching waste lithium battery cathode materials, and one of the final products is high-purity lithium hydroxide.

[0041] Figure 2 This is a simplified structural diagram of the electrochemical recovery device used in this invention, including an anode chamber 1, a cathode chamber 2, an anode catalyst contained in the anode chamber 1, a cathode catalyst contained in the cathode chamber 2, and an ion separation chamber 3 disposed between the anode chamber 1 and the cathode chamber 2; the ion separation chamber 3 is filled with anion exchange resin (…). Figure 2 The small circles within the dashed boxes represent the anion exchange resin used for packing. The anion exchange resin can be a strong-base anion exchange resin or a weak-base anion exchange resin, preferably a strong-base anion exchange resin, and the packing amount is 1-10 g / cm³. 2 The first cation exchange membrane 4 is disposed between the anode chamber 1 and the ion separation chamber 3, and the second cation exchange membrane 5 is disposed between the cathode chamber 2 and the ion separation chamber 3. The ion separation chamber 3 is also provided with an inlet for introducing the lithium oxalate solution to be treated and an outlet for discharging the regenerated oxalic acid solution. The site where the electrochemical reaction occurs is called an electrolytic cell. The anode plate and / or cathode plate of the electrolytic cell are provided with flow channels to ensure uniform distribution of the electrolyte.

[0042] During operation of the electrochemical recovery unit, H2 is generated by electrolyzing water in anode chamber 1. + H + It passes through the first cation exchange membrane 4 and enters the ion separation chamber 3, where it reacts with C2O4 in the lithium oxalate leachate. 2- The lithium oxalate solution is formed by the combination; simultaneously, the Li in the lithium oxalate leachate solution... + It passes through the second cation exchange membrane 5 and enters the cathode chamber 2, where it reacts with the OH- produced by the electrolysis of water in the cathode chamber 2. - The resulting lithium hydroxide solution is then combined with the oxalic acid solution obtained from the recovered lithium hydroxide. This solution can then be reused for leaching waste lithium battery cathode materials.

[0043] Example 1

[0044] A method for recycling waste lithium-ion battery cathode materials through the co-production of oxalic acid and lithium hydroxide, specifically comprising the following steps:

[0045] 0.2 mol of oxalic acid (H₂C₂O₄) solid powder was weighed and placed in a three-necked flask. 200 mL of deionized water was added, and the mixture was stirred until the oxalic acid was completely dissolved. Then, 18.0 g of waste lithium cobalt oxide (LiCoO₂) cathode material was added, maintaining a liquid-to-solid ratio of 20:1 (mL / g). The reaction system was heated to 80 ± 2 °C and mechanically stirred continuously at 500 rpm for 2 h. After the reaction was complete, the slurry was filtered to achieve solid-liquid separation. The obtained solid was cobalt oxalate (Co₂C₂O₄) precipitate, and the filtrate was a leachate containing lithium oxalate (Li₂C₂O₄). The cobalt oxalate precipitate was dried in an oven at 80 °C and then sintered in a muffle furnace at 450 °C for 2 h to obtain cobalt tetroxide material.

[0046] Take 20 mL of the above lithium oxalate leachate and pump it into the ion separation chamber of the electrochemical recovery device. The device operates under a constant current density of 200 mA, with a reaction potential of 2.1–2.9 V. The initial electrolytes in both the anode and cathode chambers are pure aqueous solutions. The ion separation chamber is filled with a strong-base 717 anion exchange resin at a loading density of 2 g / cm³. 2 Under the influence of an electric field, the protons (H+) produced by the anodic reaction... + The ions migrate through the cation exchange membrane (CEM) to the ion separation chamber, where they react with oxalate ions (C2O4). 2- The regeneration process combines with oxalic acid; simultaneously, the Li in the ion separation module... + It passes through the cathode-side cation exchange membrane into the cathode chamber and reacts with OH- produced at the cathode. - They combine to form a lithium hydroxide solution.

[0047] 80% of the coulombic charge (lithium concentration in the leaching solution is 0.5 mol / L, coulombic charge = lithium concentration x volume x 96485) was passed, and a lithium hydroxide solution with a concentration of 0.344 mol / L was obtained in the cathode chamber, with a lithium ion yield of 68.8% and a Faraday efficiency of 86%.

[0048] Example 2

[0049] An oxalic acid cycle and lithium hydroxide co-production waste lithium battery positive electrode material recycling method is specifically performed according to the following steps:

[0050] 0.2 mol of oxalic acid (H2C2O4) solid powder was weighed and placed in a three-necked flask, 200 mL of deionized water was added, and stirring was performed until the oxalic acid was completely dissolved. Then, 18.0 g of waste lithium cobalt oxide (LiCoO2) positive electrode material was added, and the liquid-solid ratio was controlled to be 20:1 (mL / g). The reaction system was heated to 80 ± 2 ℃, and mechanical stirring was continuously performed at a speed of 500 rpm for 2 h. After the reaction was completed, the slurry was suction filtered to realize solid-liquid separation. The obtained solid was cobalt oxalate (Co2C2O4) precipitate, and the filtrate was a leaching solution containing lithium oxalate (Li2C2O4). After the cobalt oxalate precipitate was dried in an oven at 80 ℃, it was placed in a muffle furnace and sintered at 450 ℃ for 2 h to obtain a tricobalt tetroxide material.

[0051] 20 mL of the above lithium oxalate leaching solution was pumped into the ion separation chamber of the electrochemical recycling device. The device was operated under the condition of a constant current density of 200 mA / cm 2 , and the reaction potential was 2.1-2.9 V. The initial electrolyte in the anode chamber and the cathode chamber was a pure water solution, the ion separation chamber was filled with strong base type 717 anion exchange resin, and the filling amount was 4 g / cm 2 . Under the action of an electric field, the protons (H + ) generated by the anode reaction migrated to the ion separation chamber through the cation exchange membrane (CEM) and were combined with the oxalate ions (C2O4 2- ) to regenerate oxalic acid; at the same time, the Li + in the ion separation module passed through the cathode side cation exchange membrane into the cathode chamber and combined with the OH - generated by the cathode to generate a lithium hydroxide solution.

[0052] 80% of the coulombic charge (lithium concentration in the leaching solution is 0.5 mol / L, coulombic charge = lithium concentration x volume x 96485) was passed, and a lithium hydroxide solution with a concentration of 0.383 mol / L was obtained in the cathode chamber, with a lithium ion yield of 76.6% and a Faraday efficiency of 95.8%.

[0053] Example 3

[0054] A method for recycling waste lithium battery cathode material by oxalic acid cycle and lithium hydroxide co-production, specifically performed according to the following steps:

[0055] 0.2 mol of oxalic acid (H2C2O4) solid powder was weighed and placed in a three-necked flask, 200 mL of deionized water was added, and stirring was performed until the oxalic acid was completely dissolved. Then, 18.0 g of waste lithium cobalt oxide (LiCoO2) cathode material was added, and the liquid-solid ratio was controlled to be 20:1 (mL / g). The reaction system was heated to 80 ± 2 ℃, and mechanical stirring was continuously performed at a speed of 500 rpm for 2 h. After the reaction was completed, the slurry was suction filtered to achieve solid-liquid separation. The obtained solid was cobalt oxalate (Co2C2O4) precipitate, and the filtrate was lithium oxalate (Li2C2O4) containing leaching solution. After the cobalt oxalate precipitate was dried in an oven at 80 ℃, it was placed in a muffle furnace and sintered at 450 ℃ for 2 h to obtain tricobalt tetroxide material.

[0056] 20 mL of the above lithium oxalate leaching solution was pumped into the ion separation chamber of the electrochemical recycling device. The device was operated under the condition of constant current density mA / cm 2 , and the reaction potential was 2.1-2.9 V. The initial electrolyte in the anode chamber and the cathode chamber was pure water solution, the ion separation chamber was filled with strong base type 717 anion exchange resin, and the filling amount was 6 g / cm 2 . Under the action of the electric field, the protons (H + ) generated by the anode reaction migrated to the ion separation chamber through the cation exchange membrane (CEM), combined with the oxalate ions (C2O4 2- ) to regenerate oxalic acid; at the same time, Li + in the ion separation module passed through the cathode side cation exchange membrane into the cathode chamber, combined with OH - generated in the cathode to generate lithium hydroxide solution.

[0057] 80% of the coulombic quantity (lithium concentration in the leaching solution was 0.5 mol / L, coulombic quantity = lithium concentration × volume × 96485) was introduced, and a lithium hydroxide solution with a concentration of 0.363 mol / L was obtained in the cathode chamber, the lithium ion yield was 72.6%, and the faradic efficiency was 90.8%.

[0058] Example 4

[0059] A method for recycling waste lithium battery cathode material by oxalic acid cycle and lithium hydroxide co-production, specifically performed according to the following steps:

[0060] Take 0.2 mol of oxalic acid (H2C2O4) solid powder, place it in a three-necked flask, add 200 mL of deionized water, and stir until the oxalic acid is completely dissolved. Then, add 18.0 g of waste lithium cobalt oxide (LiCoO2) positive electrode material, and control the liquid-solid ratio to be 20:1 (mL / g). Heat the reaction system to 80 ± 2 ℃, and continuously mechanically stir at a speed of 500 rpm for 2 h. After the reaction is completed, the slurry is suction filtered to achieve solid-liquid separation. The obtained solid is cobalt oxalate (Co2C2O4) precipitate, and the filtrate is a leaching solution containing lithium oxalate (Li2C2O4). After the cobalt oxalate precipitate is dried in an oven at 80 ℃, it is placed in a muffle furnace and sintered at 450 ℃ for 2 h to obtain a tricobalt tetraoxide material.

[0061] Take 20 mL of the above lithium oxalate leaching solution and pump it into the ion separation chamber of the electrochemical recycling device. The device is operated under the condition of a constant current density of 200 mA / cm 2 , and the reaction potential is 2.1-2.9 V. The initial electrolyte in the anode chamber and the cathode chamber is pure water solution, the ion separation chamber is filled with D301 macroporous weak base type styrene anion exchange resin, and the filling amount is 4 g / cm 2 . Under the action of an electric field, the protons (H + ) generated by the anode reaction migrate to the ion separation chamber through the cation exchange membrane (CEM), combine with the oxalate ions (C2O4 2- ) to regenerate oxalic acid; at the same time, Li + in the ion separation module passes through the cathode side cation exchange membrane into the cathode chamber, and combines with OH - generated by the cathode to generate lithium hydroxide solution.

[0062] Pass in 80% of the coulombic charge (lithium concentration in the leaching solution is 0.5 mol / L, coulombic charge = lithium concentration × volume × 96485), and obtain a lithium hydroxide solution with a concentration of 0.356 mol / L in the cathode chamber, with a lithium ion yield of 71.2% and a Faraday efficiency of 89%.

[0063] Comparative Example 1

[0064] A waste lithium battery positive electrode material recycling method, which is carried out according to the following steps:

[0065] Take 0.2 mol of oxalic acid (H2C2O4) solid powder, place it in a three-necked flask, add 200 mL of deionized water, and stir until the oxalic acid is completely dissolved. Then, add 18.0 g of waste lithium cobalt oxide (LiCoO2) positive electrode material, and control the liquid-solid ratio to be 20:1 (mL / g). Heat the reaction system to 80 ± 2 ℃, and continuously mechanically stir at a speed of 500 rpm for 2 h. After the reaction is completed, the slurry is suction-filtered to achieve solid-liquid separation. The obtained solid is cobalt oxalate (Co2C2O4) precipitate, and the filtrate is a leaching solution containing lithium oxalate (Li2C2O4). After the cobalt oxalate precipitate is dried in an oven at 80 ℃, it is placed in a muffle furnace and sintered at 450 ℃ for 2 h to obtain a tricobalt tetraoxide material.

[0066] Take 20 mL of the above lithium oxalate leaching solution and pump it into the ion separation chamber of an electrochemical separation device. The device is operated under the condition of a constant current density of 200 mA / cm 2 , and the reaction potential is 6.1-8.8 V. The initial electrolyte in the anode chamber and the cathode chamber is pure water solution, and the ion separation chamber is filled with a polytetrafluoroethylene plastic net. Under the action of an electric field, the protons (H + ) generated by the anode reaction migrate to the ion separation chamber through the cation exchange membrane (CEM), combine with the oxalate ions (C2O4 2- ) to regenerate oxalic acid; at the same time, the Li + in the ion separation module passes through the cathode side cation exchange membrane into the cathode chamber, and combines with the OH - generated in the cathode to generate lithium hydroxide solution.

[0067] The lithium hydroxide solution with a concentration of 0.252 mol / L is obtained in the cathode chamber by passing in 80% of the coulombic quantity (the lithium concentration in the leaching solution is 0.5 mol / L, the coulombic quantity = lithium concentration × volume × 96485), and the lithium ion yield is 50.4%, and the Faraday efficiency is 63%.

[0068] Comparative Example 2

[0069] A waste lithium battery positive electrode material recycling method is carried out according to the following steps:

[0070] Take 0.2 mol of oxalic acid (H2C2O4) solid powder, place it in a three-necked flask, add 200 mL of deionized water, and stir until the oxalic acid is completely dissolved. Then, add 18.0 g of waste lithium cobalt oxide (LiCoO2) positive electrode material, and control the liquid-solid ratio to be 20:1 (mL / g). Heat the reaction system to 80 ± 2 ℃, and continuously mechanically stir at a speed of 500 rpm for 2 h. After the reaction is completed, the slurry is suction-filtered to achieve solid-liquid separation. The obtained solid is cobalt oxalate (Co2C2O4) precipitate, and the filtrate is a leaching solution containing lithium oxalate (Li2C2O4). After the cobalt oxalate precipitate is dried in an oven at 80 ℃, it is placed in a muffle furnace and sintered at 450 ℃ for 2 h to obtain a tricobalt tetraoxide material.

[0071] Take 20 mL of the above lithium oxalate leaching solution and pump it into the ion separation chamber of an electrochemical separation device. The device is operated under the condition of a constant current density of 200 mA / cm 2 , and the reaction potential is 4.4-4.6 V. The initial electrolyte in the anode chamber and the cathode chamber is pure water solution, and the ion separation chamber is filled with carbon felt. Under the action of the electric field, the protons (H + ) generated by the anode reaction migrate to the ion separation chamber through the cation exchange membrane (CEM), combine with the oxalate ions (C2O4 2- ) to regenerate oxalic acid; at the same time, the Li + in the ion separation module passes through the cathode side cation exchange membrane into the cathode chamber, and combines with OH - generated in the cathode to generate lithium hydroxide solution.

[0072] Pass in 80% of the coulombic charge (the lithium concentration in the leaching solution is 0.5 mol / L, and the coulombic charge = lithium concentration × volume × 96485), and a lithium hydroxide solution with a concentration of 0.266 mol / L is obtained in the cathode chamber, with a lithium ion yield of 53.2% and a Faraday efficiency of 66.5%.

[0073] Comparative Example 3

[0074] A waste lithium battery positive electrode material recycling method, which is carried out according to the following steps:

[0075] Take 0.2 mol of oxalic acid (H2C2O4) solid powder, put it in a three-necked flask, add 200 mL of deionized water, and stir until the oxalic acid is completely dissolved. Then, add 18.0 g of waste lithium cobalt oxide (LiCoO2) positive electrode material, control the liquid-solid ratio to be 20:1 (mL / g). Heat the reaction system to 80 ± 2 ℃, and continuously mechanically stir at a speed of 500 rpm for 2 h. After the reaction is completed, the slurry is suction filtered to achieve solid-liquid separation. The obtained solid is cobalt oxalate (Co2C2O4) precipitate, and the filtrate is a leaching solution containing lithium oxalate (Li2C2O4). After the cobalt oxalate precipitate is dried in an oven at 80 ℃, it is placed in a muffle furnace and sintered at 450 ℃ for 2 h to obtain a tricobalt tetraoxide material.

[0076] Take 20 mL of the above lithium oxalate leaching solution and pump it into the ion separation chamber of the electrochemical separation device. The device is operated under the condition of a constant current density of 200 mA / cm 2 , and the reaction potential is 2-2.4 V. The initial electrolyte in the anode chamber and the cathode chamber is pure water solution, and the ion separation chamber is filled with 732 hydrogen type strong acid type cation exchange resin. Under the action of the electric field, the protons (H + ) generated by the anode reaction migrate to the ion separation chamber through the cation exchange membrane (CEM), combine with the oxalate ions (C2O4 2- ) to regenerate oxalic acid; at the same time, Li + in the ion separation module passes through the cathode side cation exchange membrane into the cathode chamber, and combines with OH - generated in the cathode to form lithium hydroxide solution.

[0077] Pass in 80% of the coulombic charge (lithium concentration in the leaching solution is 0.5 mol / L, coulombic charge = lithium concentration × volume × 96485), and obtain a lithium hydroxide solution with a concentration of 0.02 mol / L in the cathode chamber, with a lithium ion yield of 4% and a Faraday efficiency of 10%.

[0078] Figure 3 The actual photos of the lithium oxalate solution (left) and the cobalt oxalate powder (right) generated by the oxalic acid leaching of waste lithium cobalt oxide. The obtained lithium oxalate solution (left) is green, not colorless and transparent. This phenomenon indicates that part of the Co 2+ forms a soluble [Co(C2O4)2] 2- complex with excess oxalate ions, resulting in incomplete precipitation of cobalt in the solution. Correspondingly, the precipitated cobalt oxalate on the right shows its typical pink color.

[0079] As shown in Figure 4 , the ion separation chamber of the device in Example 2 is filled with 4 g / cm 2The strong-base 717 anion exchange resin, at an 80% coulombic loading, exhibited a lithium-ion yield of 76.6% and a Faradaic efficiency of 95.8%, which are higher than those of Example 1 (loading amount 2 g / cm³). 2 The lithium-ion yield and Faraday efficiency were 68.8% and 86%, respectively, and Example 3 (filling amount 6 g / cm³) 2 (The lithium-ion yield and Faraday efficiency were 72.6% and 90.8%, respectively). When the amount of strong-base 717 anion exchange resin is small, it cannot completely fix all oxalate ions in the leachate, and some oxalate ions exist as free HC2O4. - or C2O4 2- It exists in form. H migrated from the anode. + It will rapidly deplete the limited oxalate binding sites. Excess H+ + It will be unable to be effectively captured and associated with Li + They compete and pass through the second cation exchange membrane together into the cathode chamber. However, if the amount of strong base 717 anion exchange resin is too large, the excessively thick resin bed will cause Li... + A longer migration distance is required to reach the second cation exchange membrane. The resin bed itself has resistance; excessive packing increases the internal resistance of the entire electrochemical system, leading to a decrease in current at the same voltage or an increase in energy consumption at the same current, potentially causing concentration polarization: within the narrow spaces between resin particles, ion migration slows down, which may lead to localized Li+ ion exchange. + Lower concentrations limit migration rates.

[0080] Example 4: The ion separation chamber was filled with 4 g / cm³ 2 The strong-base 717 anion exchange resin, at 80% coulombic loading, exhibited a lithium-ion yield of 71.2% and a Faradaic efficiency of 89%, lower than the lithium-ion yield (76.6%) and Faradaic efficiency (95.8%) of Example 2. This performance difference is attributed to the influence of resin type on ion migration pathways. The quaternary ammonium groups of the strong-base 717 anion exchange resins (Examples 1-3) maintain stable positive charge over a wide pH range, enabling sustained oxalate fixation and efficient proton capture (H+). + ), thus providing lithium ions (Li + This constructed an exclusive migration channel. The amine groups of the D301 macroporous weakly basic styrene anion exchange resin (Example 4) exhibit significant pH dependence. Initially, it functions effectively in an acidic environment; however, the "proton trapping" function fails as the number of protons increases. Uncaptured H+... + Then with Li + The competition shifts to the cathode chamber, neutralizing the generated LiOH on one hand and reducing the efficiency of the current used for lithium recovery on the other, ultimately leading to a double decrease in lithium yield and Faraday efficiency.

[0081] As shown in Figure 5 , the potential of Example 2 and Comparative Examples 1, 2, 3 has obvious difference under 200 mA current, compared with cation (2.1 V) and anion exchange resin (2.7 V), the potential is as high as 6.1-8.8 V and 4.4-4.6 V when using polytetrafluoroethylene plastic net and carbon felt, mainly due to the polytetrafluoroethylene plastic net and carbon felt mainly play a physical filling and supporting role, without ion exchange function, the ions (Li + , H + , C2O4 2- ) in the solution can only migrate through the solution body, with great resistance. While the strong base type 717 anion exchange resin of Example 2 itself has fixed functional groups, which can selectively conduct or capture specific ions, actively participate in and optimize the ion transmission path, so the required potential is lower under the same current.

[0082] As shown in Figure 6 , under the given 80% coulomb quantity, the lithium ion yield is increased from 4% of 732 hydrogen type strong acid type cation exchange resin (Comparative Example 3) to 76.6% of strong base type 717 anion exchange resin (Example 2), while the Faraday efficiency of lithium ion is increased from 10% to 95.8%. This is because the functional groups of 732 hydrogen type strong acid type cation exchange resin are negatively charged (such as sulfonic acid group-SO3 - ), which essentially allows cations to pass through and exchange them, but the affinity (selectivity) of different cations is different. Among all cations, the binding ability of proton (H + ) to cation exchange resin functional groups is usually one of the strongest. Under the action of the electric field, H + continuously migrates from the anode chamber and quickly occupies the exchange sites on the resin. The resin will "grab" and "conduct" H + "preferentially". Compared with H + , the hydrated ion radius of Li + is larger, and its migration rate in the resin is lower. When a large amount of H + flows into the ion separation chamber and occupies the conductive path of the resin, the migration channel of Li + is severely blocked. The entire middle layer is like a "high-speed channel" for H + . Most of the current is carried by the migration of H + , resulting in H + becoming the main cation entering the cathode chamber. H + entering the cathode chamber will immediately combine with OH - generated by the cathode to generate water, thereby consuming OH - , so that Li +Even a small amount of entry cannot form effective LiOH. Therefore, what is obtained on the cathode side is a dilute solution with very low lithium content, the main component of which is water.

[0083] Example 2 uses the quaternary ammonium group -N in strong base type 717 anion exchange resin + (CH3)3 is positively charged, which allows anions to pass through and exchange with it. This property fundamentally changes the ion migration pattern of the system, and the anion exchange resin will firmly adsorb oxalate ions (C2O4 2- ) in the intermediate layer solution. In order to maintain electrical neutrality, Li 2- , which was originally paired with C2O4 + , will be "released" into the pore solution between the resin particles, becoming a free ion, and H + , which migrates from the anode chamber, will immediately encounter C2O4 2- fixed by the resin as soon as it enters the intermediate layer full of anion exchange resin. H + will combine with C2O4 2- to form oxalic acid (H2C2O4). This process effectively consumes (neutralizes) H + , preventing it from migrating towards the cathode. Since the anion exchange resin does not conduct cations, it does not hinder the migration of Li + . At the same time, the only competitor H + is also "eliminated" by oxalate at the inlet. Therefore, under the action of the electric field, a large number of free Li + in the intermediate layer solution becomes the only cation that can migrate towards the cathode. Li + smoothly passes through the anion exchange membrane on the cathode side and enters the cathode chamber in large quantities. In the cathode chamber, these Li + combine smoothly with OH - generated by electrolysis of water to form a high-purity lithium hydroxide solution.

[0084] The present application fills the ion separation chamber of the electrochemical recycling device with an appropriate amount of strong base type anion exchange resin, and ingeniously constructs a Li + purifier and H + trap. The resin dissociates Li + by fixing oxalate, and on the other hand, captures and neutralizes H + in situ using oxalate, creating perfect conditions for the exclusive migration of Li + . The physical and chemical properties of different ion exchange resins are skillfully used to achieve high-selectivity electrically-driven migration and purification of specific ions (Li + ), and to achieve the recycling of oxalic acid reagent and the direct production of high-value lithium hydroxide.

[0085] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for recycling waste lithium battery cathode material co-producing oxalic acid cycle and lithium hydroxide, characterized in that, The method comprises the following steps: Step (1), mixing and stirring the waste lithium battery positive electrode material with oxalic acid solution, solid-liquid separation, obtaining oxalic acid metal salt precipitate and lithium oxalate leaching solution; Step (2), introducing the lithium oxalate leaching solution into the ion separation chamber of the electrochemical recovery device, filling the ion separation chamber with anion exchange resin, starting the electrochemical recovery device, collecting the obtained lithium hydroxide after treatment, and regenerating the obtained oxalic acid solution for reuse in step (1) for leaching of the waste lithium battery positive electrode material; The electrochemical recovery device comprises an anode chamber (1), a cathode chamber (2), and an ion separation chamber (3) between the two, a first cation exchange membrane (4) is arranged between the anode chamber (1) and the ion separation chamber (3), a second cation exchange membrane (5) is arranged between the cathode chamber (2) and the ion separation chamber (3), the ion separation chamber (3) is filled with anion exchange resin, and an inlet and an outlet are arranged. The anion exchange resin comprises strong base anion exchange resin and weak base anion exchange resin; wherein the strong base anion exchange resin contains a quaternary ammonium group -NR3OH in the structural formula, and R is a hydrocarbon group; the weak base anion exchange resin contains a primary amino group -NH2, a secondary amino group -NHR, or a tertiary amino group -NR2 in the structural formula, and R is a hydrocarbon group.

2. The method according to claim 1, wherein the method is characterized by, In step (1), the waste lithium battery positive electrode material is at least one of lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum acid, lithium cobalt acid, lithium iron phosphate, lithium manganate, and a mixture thereof.

3. The method according to claim 1, wherein the method is characterized by, In step (1), the concentration of the oxalic acid solution is 0.1-3 mol / L; the molar ratio of the waste lithium battery positive electrode material to the oxalic acid solution is 1-3; the stirring reaction is carried out at a speed of 100-2000 rpm and a temperature of 60-100℃ for 1-5 h.

4. The method according to claim 1, wherein the method is characterized by, The oxalic acid metal salt precipitate in step (1) is heat treated at 400-600℃ for 1-3 h to obtain the corresponding metal oxide or precursor; the lithium oxalate leaching solution in step (1) is pre-concentrated before entering the ion separation chamber of the electrochemical recovery device in step (2), so that the lithium ion concentration is not less than 2 g / L.

5. The method according to claim 1, wherein the method is characterized by, The anion exchange resin is filled in the ion separation chamber in an amount of 1-10 g / cm 2 .

6. The method according to claim 1, wherein the method is characterized by, The electrolyte in the anode chamber (1) and the cathode chamber (2) is one of water, dilute acid or dilute alkali; the anode chamber (1) contains one of anode catalysts Fe, Co, Ni, Cu, Zr, Pd, Ru, Ir, Au, C and corresponding metal oxides or metal alloy materials; the cathode chamber (2) contains one of cathode catalysts Fe, Co, Ni, Cu, Mn, Pd, Ru, Ir, Au, Pt, C and corresponding metal oxides or metal alloy materials.

7. The method according to claim 1, wherein the method is characterized by, The first cation exchange membrane (4) and the second cation exchange membrane (5) are one of sulfonic acid type cation exchange membrane or carboxylic acid type cation exchange membrane.

8. The method according to claim 1, wherein the method is characterized by, In step (2), the current density of the electrochemical recovery device when in operation is 1-200 mA / cm 2 , the voltage is 0.1-30 V, and the reaction potential is 2-10 V.

9. The method according to any one of claims 1-8, wherein the method is characterized in that, The electrochemical recovery device operates, the anode chamber (1) electrolysis water produces H + Through the first cation exchange membrane (4) into the ion separation chamber (3), with the C2O4 2- Combined to generate oxalic acid solution; at the same time, Li + Through the second cation exchange membrane (5) into the cathode chamber (2), with the OH - Combined to generate lithium hydroxide solution.

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