Method for electrochemical lithium extraction of retired lithium battery assisted by pseudocapacitor cathode

Abstract

The invention belongs to the field of electrochemistry, and particularly relates to a method for electrochemical lithium extraction of a decommissioned lithium battery assisted by a pseudocapacitor cathode, which comprises the following steps: a) providing an anode electrode and a cathode electrode; the anode electrode is an anode electrode made of a recycled retired lithium battery anode material or an retired lithium battery anode plate; the cathode electrode contains a Prussian blue analogue, the Prussian blue analogue is prepared by mixing citrate, transition metal salt and cyanide in water for reaction, and the transition metal salt is one or more of cobalt salt, ferric salt, copper salt and nickel salt; and b) immersing the anode electrode and the cathode electrode into the electrolyte, and electrifying to carry out electrochemical lithium extraction. According to the method, a pseudocapacitance material with a lithium discharging characteristic is adopted as a cathode to replace a common metal pole plate or a carbon material, a pseudocapacitance reaction with a corrected electrode potential is adopted to replace a hydrogen evolution reaction on the cathode of an existing system, and finally, low-energy-consumption and high-selectivity recovery of lithium is realized.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemistry, and in particular relates to a method for electrochemically extracting lithium from retired lithium batteries using a pseudocapacitive cathode. Background Art

[0002] In recent years, the global lithium battery industry has developed rapidly and has been widely used in new energy and other fields. At the same time, the market is about to usher in a large-scale wave of lithium battery retirement. How to properly dispose of retired lithium batteries and recycle them is a key challenge that needs to be solved urgently.

[0003] Since retired lithium batteries contain abundant lithium, with a higher content and purity than natural mineral reserves, they are considered high-quality "urban mines". Recovering lithium from retired lithium batteries is a key way to solve the problem of retired battery disposal and achieve sustainable supply of lithium resources. However, traditional wet and pyrometallurgical recovery processes generally have problems such as high environmental pollution, high energy consumption, high lithium loss rate, and low recovery purity.

[0004] Recently, some researchers have proposed a new technology for electrochemical lithium extraction from retired lithium batteries. This technology directly uses the positive electrode material of retired lithium batteries as the anode, relies on applying voltage or generating strong oxidizing free radicals in situ to induce oxidation reactions of transition metals in the electrode material, and simultaneously couples the electrostatic repulsion of the anode to lithium ions to drive the selective leaching of lithium.

[0005] Compared with traditional processes, electrochemical lithium extraction technology has the advantages of green process and high lithium recovery purity, but it also has problems such as low lithium leaching efficiency and high energy consumption. A key reason for the high energy consumption is that the cathode of the existing electrochemical lithium extraction system mainly undergoes hydrogen evolution reaction, which generates hydrogen through the reduction of water molecules / protons, thereby driving metal oxidation on the anode and the release and migration of lithium to maintain charge and ion balance. However, the potential required for the cathode hydrogen evolution reaction is low (<0Vvs.RHE), the reaction energy barrier is high, and the kinetics are slow. These characteristics seriously restrict the lithium leaching efficiency of the anode (usually more than 3h is required for leaching). At the same time, in order to drive lithium leaching, a high voltage of more than 2.5V needs to be applied, which significantly increases energy consumption and further hinders the scale and commercial application of this technology. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for electrochemical lithium extraction of retired lithium batteries assisted by a pseudocapacitive cathode. The method uses a pseudocapacitive material with lithium expulsion properties as a cathode to replace the commonly used metal plate or carbon material, and replaces the hydrogen evolution reaction on the cathode of the existing system with a pseudocapacitive reaction with a more positive electrode potential, thereby significantly reducing the voltage and energy consumption of the entire electrochemical lithium extraction system, while enhancing lithium leaching on the anode, and ultimately achieving low-energy consumption and high-selectivity recovery of lithium.

[0007] The present invention provides a method for electrochemically extracting lithium from retired lithium batteries using a pseudocapacitive cathode, comprising the following steps:

[0008] a) providing an anode electrode and a cathode electrode;

[0009] The anode electrode is an anode electrode made of recycled retired lithium battery positive electrode material, or is a retired lithium battery positive electrode plate;

[0010] The cathode electrode contains a Prussian blue analogue, which is prepared by a mixed reaction of citrate, a transition metal salt and a cyanide in water, wherein the transition metal salt is one or more of a cobalt salt, an iron salt, a copper salt and a nickel salt, and the cyanide is ferrocyanide and / or ferrocyanide;

[0011] b) immersing the anode electrode and the cathode electrode in an electrolyte and applying power to perform electrochemical lithium extraction.

[0012] Preferably, in step a), the recovered retired lithium battery positive electrode material and the positive electrode material in the retired lithium battery positive plate are one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide and ternary lithium.

[0013] Preferably, in step a), the anode electrode is prepared from the recycled retired lithium battery positive electrode material according to the following steps:

[0014] The recycled retired lithium battery positive electrode material, a binder and a solvent are mixed to obtain an anode electrode slurry;

[0015] The anode electrode slurry is coated on a current collector and dried to obtain an anode electrode.

[0016] Preferably, in step a), the Prussian blue analogue is prepared according to the following steps:

[0017] Citrate, transition metal salt and cyanide are stirred and mixed in water, aged, solid-liquid separated, solid phase washed and dried to obtain a Prussian blue analogue.

[0018] Preferably, the citrate is potassium citrate and / or sodium citrate; the transition metal salt is one or more of cobalt nitrate, ferric nitrate, copper nitrate and nickel nitrate; the cyanide is potassium ferrocyanide and / or potassium ferrocyanide; and the molar ratio of the citrate, the transition metal salt and the cyanide is (3-5):(1-3):1.

[0019] Preferably, the stirring and mixing time is 12 to 24 hours; the aging time is 12 to 24 hours; the solid-liquid separation method is centrifugal separation, and the centrifugal speed is 6000 to 12000 rpm; the drying temperature is 50 to 100°C.

[0020] Preferably, in step a), the cathode electrode is prepared according to the following steps:

[0021] mixing a Prussian blue analog, a binder and a solvent to obtain a cathode electrode slurry;

[0022] The cathode electrode slurry is coated on a current collector and dried to obtain a cathode electrode.

[0023] Preferably, in step b), the solute in the electrolyte is one or more of K2SO4, Na2SO4, KNO3, NaNO3 and NaCl; and the concentration of the solute in the electrolyte is 0.01 to 0.1 mol / L.

[0024] Preferably, in step b), the electrochemical lithium extraction is carried out under stirring conditions.

[0025] Preferably, the method further comprises:

[0026] c) After the electrochemical lithium extraction is completed by applying power, carbonate is added to the electrolyte to recover the generated lithium carbonate precipitate.

[0027] Compared with the prior art, the present invention provides a method for electrochemical lithium extraction of retired lithium batteries assisted by a pseudocapacitor cathode, comprising the following steps: a) providing an anode electrode and a cathode electrode; the anode electrode is an anode electrode made of recycled retired lithium battery positive electrode material, or a retired lithium battery positive electrode plate; the cathode electrode contains a Prussian blue analog, which is prepared by a mixed reaction of citrate, a transition metal salt and a cyanide in water, wherein the transition metal salt is one or more of a cobalt salt, an iron salt, a copper salt and a nickel salt, and the cyanide is a ferrocyanide and / or a ferrocyanide; b) immersing the anode electrode and the cathode electrode in an electrolyte, and applying power to perform electrochemical lithium extraction. In the present invention, a pseudocapacitor cathode is used to absorb a large amount of cations (non-lithium ions) in the electrolyte into the material lattice, and at the same time, electrons flow from the anode of the retired lithium battery to the cathode, thereby driving the oxidation of the anode and the dissolution of lithium ions. In order to ensure that the lithium ions released by the anode are not reabsorbed by the cathode, pseudocapacitor materials (Prussian blue analogs, PBAs) with lithium expulsion properties are prepared by coprecipitation. They are then made into cathode electrodes and combined with retired lithium battery materials (such as lithium iron phosphate LFP, lithium cobalt oxide LCO, lithium manganese oxide LMO, ternary lithium NCM, etc.) as anode electrodes to construct an electrochemical lithium extraction system. By simulating the charging process of lithium batteries, efficient and low-consumption electrochemical lithium extraction is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0029] Figure 1 is the XRD spectrum of Co-PBAs provided in Example 1 of the present invention;

[0030] Figure 2 This is a diagram showing the verification results of the lithium removal characteristics of the Co-PBAs electrode provided in Example 1 of the present invention;

[0031] Figure 3 This is a diagram showing the verification results of the lithium removal characteristics of the Fe / Cu / Ni-PBAs electrode provided in Example 1 of the present invention;

[0032] Figure 4 This is a comparison diagram of the effects of Co-PBAs electrode and Pt as cathode-assisted electrochemical lithium extraction at different voltages provided in Example 2 of the present invention;

[0033] Figure 5 This is a comparison diagram of the effects of various metal-based PBAs electrodes and Pt as cathode-assisted electrochemical lithium extraction at a voltage of 1V provided in Example 2 of the present invention;

[0034] Figure 6 This is a comparison diagram of the effects of different electrolytes on Co-PBAs electrodes as cathode-assisted electrochemical lithium extraction at a voltage of 1 V provided in Example 3 of the present invention;

[0035] Figure 7 This is a graph showing the experimental results of the cycle stability of the Co-PBAs electrode as a cathode-assisted electrochemical lithium extraction at a voltage of 1 V provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The present invention provides a method for electrochemically extracting lithium from retired lithium batteries using a pseudocapacitive cathode, comprising the following steps:

[0038] a) providing an anode electrode and a cathode electrode;

[0039] The anode electrode is an anode electrode made of recycled retired lithium battery positive electrode material, or is a retired lithium battery positive electrode plate;

[0040] The cathode electrode contains a Prussian blue analogue, which is prepared by a mixed reaction of citrate, a transition metal salt and a cyanide in water, wherein the transition metal salt is one or more of a cobalt salt, an iron salt, a copper salt and a nickel salt, and the cyanide is ferrocyanide and / or ferrocyanide;

[0041] b) immersing the anode electrode and the cathode electrode in an electrolyte and applying power to perform electrochemical lithium extraction.

[0042] In the method provided by the present invention, in step a), the recovered retired lithium battery positive electrode material and the positive electrode material in the retired lithium battery positive plate include but are not limited to one or more of lithium iron phosphate LFP, lithium cobalt oxide LCO, lithium manganese oxide LMO and ternary lithium NCM, preferably ternary lithium NCM.

[0043] In the method provided by the present invention, in step a), the recovered retired lithium battery positive electrode material is preferably an anode electrode made according to the following steps:

[0044] The recycled retired lithium battery positive electrode material, a binder and a solvent are mixed to obtain an anode electrode slurry;

[0045] The anode electrode slurry is coated on a current collector and dried to obtain an anode electrode.

[0046] In the above-mentioned anode electrode preparation steps provided by the present invention, the binder includes but is not limited to a perfluorosulfonic acid polymer solution (Nafion solution); the amount ratio of the binder to the retired lithium battery positive electrode material is preferably 50μL: (20-100) mg, specifically 50μL: 20mg, 50μL: 30mg, 50μL: 40mg, 50μL: 50mg, 50μL: 60mg, 50μL: 70mg, 50μL: 80mg, 50μL: 90mg or 50μL: 100mg; the solvent includes but is not limited to isopropanol; The usage ratio of the solvent to the retired lithium battery positive electrode material is preferably 950μL:(20-100)mg, specifically 950μL:20mg, 950μL:30mg, 950μL:40mg, 950μL:50mg, 950μL:60mg, 950μL:70mg, 950μL:80mg, 950μL:90mg or 950μL:100mg; the current collector includes but is not limited to carbon paper; the drying temperature is preferably 50-100℃, specifically 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃.

[0047] In the method provided by the present invention, in step a), the Prussian blue analogue contained in the cathode electrode is preferably a cobalt-based Prussian blue analogue, that is, the transition metal salt selected when preparing the Prussian blue analogue is a cobalt salt.

[0048] In the method provided by the present invention, in step a), the Prussian blue analogue is prepared according to the following steps:

[0049] Citrate, transition metal salt and cyanide are stirred and mixed in water, aged, solid-liquid separated, solid phase washed and dried to obtain a Prussian blue analogue.

[0050] In the above-mentioned preparation steps of the Prussian blue analog provided by the present invention, the citrate is preferably potassium citrate and / or sodium citrate; the transition metal salt is preferably one or more of cobalt nitrate, iron nitrate, copper nitrate and nickel nitrate; the cyanide is preferably potassium ferrocyanide and / or potassium ferrocyanide; the molar ratio of the citrate, the transition metal salt and the cyanide is preferably (3-5):(1-3):1, more preferably 4:2:1; the stirring and mixing temperature is preferably 10-40°C, specifically 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or 40°C; the stirring and mixing time is preferably 12-24h, specifically 12h, 14h, 16h, 18h, 20h, 22h or 24h; The aging temperature is preferably 10-40°C, specifically 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or 40°C; the aging time is preferably 12-24h, specifically 12h, 14h, 16h, 18h, 20h, 22h or 24h; the solid-liquid separation method is preferably centrifugal separation, and the centrifugal speed is preferably 6000-12000rpm, specifically 6000rpm, 7000rpm, 8000rpm, 9000rpm, 10000rpm, 11000rpm or 12000rpm; the drying temperature is preferably 50-100°C, specifically 50°C, 60°C, 70°C, 80°C, 90°C or 100°C.

[0051] In the method provided by the present invention, in step a), the cathode electrode is prepared according to the following steps:

[0052] mixing a Prussian blue analog, a binder and a solvent to obtain a cathode electrode slurry;

[0053] The cathode electrode slurry is coated on a current collector and dried to obtain a cathode electrode.

[0054] In the above-mentioned cathode electrode preparation steps provided by the present invention, the binder includes but is not limited to a perfluorosulfonic acid polymer solution (Nafion solution); the dosage ratio of the binder to the Prussian blue analog is preferably 50 μL: (20-100) mg, specifically 50 μL: 20 mg, 50 μL: 30 mg, 50 μL: 40 mg, 50 μL: 50 mg, 50 μL: 60 mg, 50 μL: 70 mg, 50 μL: 80 mg, 50 μL: 90 mg or 50 μL: 100 mg; the solvent includes but is not limited to isopropanol; The dosage ratio of the solvent to the Prussian blue analogue is preferably 950μL:(20-100)mg, specifically 950μL:20mg, 950μL:30mg, 950μL:40mg, 950μL:50mg, 950μL:60mg, 950μL:70mg, 950μL:80mg, 950μL:90mg or 950μL:100mg; the current collector includes but is not limited to carbon paper; the drying temperature is preferably 50-100℃, specifically 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃.

[0055] In the method provided by the present invention, in step b), the solute in the electrolyte is preferably one or more of K2SO4, Na2SO4, KNO3, NaNO3 and NaCl, more preferably K2SO4; the concentration of the solute in the electrolyte is preferably 0.01-0.1 mol / L, specifically 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L or 0.1 mol / L, most preferably 0.05 mol / L.

[0056] In the method provided by the present invention, in step b), the electrochemical lithium extraction is preferably carried out under stirring conditions; the stirring speed is preferably ≤500rpm, specifically 50rpm, 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm or 500rpm.

[0057] In the method provided by the present invention, in step b), the voltage of the electrochemical lithium extraction is preferably ≤2V, specifically 0V, 0.1V, 0.2V, 0.5V, 0.7V, 1V, 1.2V, 1.5V, 1.7V or 2V; the temperature of the electrochemical lithium extraction is preferably 10-40°C, specifically 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or 40°C; the time of the electrochemical lithium extraction is preferably ≤5h, specifically 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h.

[0058] In the method provided by the present invention, it is preferred that the following steps are also included:

[0059] c) After the electrochemical lithium extraction is completed by applying power, carbonate is added to the electrolyte to recover the generated lithium carbonate precipitate.

[0060] Compared with conventional electrochemical lithium extraction technology for retired lithium batteries, the method provided by the present invention has at least the following advantages:

[0061] (1) The cathode reaction was ingeniously designed by optimizing the cathode material. The pseudocapacitive reaction with a more positive electrode potential was selected to replace the hydrogen evolution reaction on the cathode of the existing system. After coupling with the lithium selective leaching reaction on the anode, the gap between the redox potentials of the cathode and the cathode was greatly reduced, thereby achieving efficient electrochemical lithium extraction at ultra-low voltage. At the same time, the side reactions of water electrolysis and the possible generation of gases that may cause the electrode material to fall off were effectively avoided, greatly improving the Faraday efficiency.

[0062] (2) The electrolyte, which is often overlooked in the electrochemical process, is utilized. The rapid coupling of potassium / sodium ions and electrons at the pseudocapacitive cathode significantly reduces the electrochemical polarization and improves the lithium leaching efficiency at the anode. 100% lithium leaching can be achieved in a short time, and the lithium leaching selectivity can also reach about 100%, which has important environmental significance and economic value.

[0063] For the sake of clarity, the following examples are used to explain the present invention in detail. In the following examples of the present invention, unless otherwise specified, all are carried out at room temperature and pressure.

[0064] Example 1: Verification of Lithium Expulsion Properties of Pseudocapacitive Cathodes (PBAs)

[0065] (1) Synthesis of cobalt-based Prussian blue analogs (Co-PBAs):

[0066] Potassium citrate and cobalt nitrate are uniformly dispersed in 100 mL of water, which is referred to as solution 1; potassium ferrocyanide is uniformly dispersed in 100 mL of water, which is referred to as solution 2; wherein the concentration of cobalt nitrate in solution 1 is 0.2 mol / L, and the molar ratio of potassium citrate, cobalt nitrate and potassium ferrocyanide is 4:2:1;

[0067] Solution 1 and solution 2 were simultaneously added into 50 mL of water at a rate of 1 mL / min through a peristaltic pump, and cobalt-based Prussian blue analogues (Co-PBAs) were obtained after stirring, aging, centrifugation, washing, and drying; wherein the stirring time was 18 h, the aging time was 18 h, the centrifugal speed was 10000 rpm, and the drying temperature was 70°C.

[0068] The synthesized Co-PBAs were tested by XRD, and the results were as follows: Figure 1 As shown, Figure 1 is the XRD spectrum of Co-PBAs provided in Example 1 of the present invention. Figure 1 It can be seen that the Co-PBAs synthesized in this example have four main peaks in the range of 17 to 40°, corresponding to the (200), (220), (400) and (420) crystal planes of the face-centered cubic structure, indicating that the Prussian blue analogue was successfully synthesized.

[0069] (2) Verification of the lithium removal properties of Co-PBAs electrodes:

[0070] Take 30 mg of Co-PBAs, mix with 50 μL Nafion (binder) and 950 μL isopropanol, and evenly apply it on the cleaned and cut 2×2 cm 2 The carbon paper was placed on the substrate and dried to make Co-PBAs electrodes.

[0071] The alkali metal cation adsorption experiment of single salt and mixed salt was carried out on Co-PBAs electrode using Chenhua electrochemical workstation (CHI760e). The specific experimental process was as follows: a 100mL three-electrode electrolytic cell was used, the volume of the electrolyte was 50mL, and 1mmol / L single salt solutions of K2SO4, Na2SO4, and Li2SO4 and mixed salt solutions of 1mmol / L K2SO4+1mmol / L Li2SO4 and 1mmol / LNa2SO4+1mmol / L Li2SO4 were prepared respectively; the working electrode was 2×2cm 2 The Co-PBAs electrode (active material loading is 30 mg), the counter electrode is a graphite rod, the reference electrode is silver / silver chloride (Ag / AgCl), the working potential is 0 V vs. Ag / AgCl, the stirring rate is 250 rpm, the reaction time is 1 h, and the change in the concentration of alkali metal cations in the electrolyte before and after the reaction is detected by inductively coupled plasma optical emission spectrometry (ICP-OES) to obtain the adsorption capacity of the Co-PBAs electrode for different alkali metal cations.

[0072] The results are as follows Figure 2 As shown, Figure 2This is a verification result diagram of the lithium removal characteristics of the Co-PBAs electrode provided in Example 1 of the present invention. Figure 2 It can be seen that the Co-PBAs electrode has a high adsorption capacity for potassium ions, exceeding 70 mg / g, and an adsorption capacity for sodium ions exceeding 35 mg / g. The adsorption capacity for lithium ions is less than 0.2 mg / g, and it can hardly adsorb lithium ions. This shows that Co-PBAs can be used as a cathode to assist the electrochemical extraction of lithium from retired lithium batteries, and will hardly affect the concentration and recovery of lithium in the electrolyte, confirming the feasibility of the technical solution of the present invention.

[0073] (3) Synthesis of other metal-based Prussian blue analogs:

[0074] Referring to the synthesis method in (1), cobalt nitrate was replaced by iron nitrate, copper nitrate, and nickel nitrate, respectively, to obtain iron-based Prussian blue analogs (Fe-PBAs), copper-based Prussian blue analogs (Cu-PBAs), and nickel-based Prussian blue analogs (Ni-PBAs).

[0075] (4) Verification of lithium removal properties of Fe / Cu / Ni-PBAs electrodes:

[0076] An alkali metal cation adsorption experiment similar to (2) was carried out on the Fe / Cu / Ni-PBAs electrode, and the electrolyte used was 1mmol / L K2SO4+1mmol / L Li2SO4 in (2).

[0077] The results are as follows Figure 3 As shown, Figure 3 This is a diagram showing the verification results of the lithium removal characteristics of the Fe / Cu / Ni-PBAs electrode provided in Example 1 of the present invention. Figure 3 It can be seen that the adsorption capacity of various metal-based PBAs electrodes for lithium ions is less than 0.1 mg / g, and they all show strong lithium expulsion characteristics.

[0078] Example 2: Comparison of the effects of the technical solution of the present invention and conventional electrochemical lithium extraction technology

[0079] In order to demonstrate the advantages of the technical solution of the present invention, the Co-PBAs electrode and Pt prepared in Example 1 were used as cathodes, and an electrochemical lithium extraction experiment was carried out using CHI760e. The specific experimental process is as follows:

[0080] The electrochemical experiment used a 100 mL two-electrode electrolytic cell with 50 mL of 0.05 mol / L K2SO4 solution as the electrolyte; the cathode electrode was 2 × 2 cm 2 Co-PBAs electrode (active material loading 30 mg) or Pt sheet, anode electrode 2 × 2 cm 2The NCM electrode (active material loading is 30 mg), the applied voltage is 0-2 V, the stirring rate is 250 rpm, the reaction time is 2 h, and the changes in the concentrations of lithium, cobalt, nickel, manganese and other ions in the electrolyte before and after the reaction are detected by inductively coupled plasma optical emission spectrometry (ICP-OES), and the electrochemical lithium extraction effects under different technical schemes are obtained.

[0081] The results are as follows Figure 4 As shown, Figure 4 This is a comparison diagram of the effects of Co-PBAs electrode and Pt as cathode assisted electrochemical lithium extraction at different voltages provided by Example 2 of the present invention. Figure 4 It can be concluded that the technical solution of the present invention selects a pseudocapacitive reaction with a more positive electrode potential to replace the hydrogen evolution reaction on the cathode of the existing system. After coupling with the lithium selective leaching reaction on the anode, the gap between the redox potentials of the cathode and the cathode is greatly reduced, the external voltage required for lithium extraction is lower, and the lithium leaching kinetics are faster at the same voltage.

[0082] Specifically, when Pt was used as the cathode to assist electrochemical lithium extraction, only about 28% of lithium was leached in 2 hours at a voltage of 1V. In comparison, when Co-PBAs electrodes were used as cathodes, 100% lithium leaching was achieved efficiently under the conditions of 1V and 2 hours, and the leaching selectivity could also reach about 100%. The pH of the electrolyte remained almost unchanged before and after the reaction, confirming that pseudocapacitive cathode assistance can effectively avoid the side reactions of water electrolysis, achieve the goal of improving Faraday efficiency and reducing energy consumption, and reflect the advantages of the technical solution of the present invention.

[0083] Furthermore, under the preferred voltage condition (1 V), various metal-based PBAs electrodes prepared in Example 1 were used as cathodes to test their effect of assisting electrochemical lithium extraction. Figure 5 As shown, Figure 5 This is a comparison chart of the effects of various metal-based PBAs electrodes and Pt as cathode-assisted electrochemical lithium extraction at 1V voltage provided by Example 2 of the present invention. Figure 5 It can be concluded that when various metal-based PBAs electrodes are assisted, more than 90% lithium leaching can be achieved under the conditions of 1V and 2h, and the leaching selectivity can reach about 100%, and the pH of the electrolyte before and after the reaction is almost unchanged. These results prove the versatility of the technical solution of the present invention in PBAs materials.

[0084] Example 3: Optimization of reaction conditions

[0085] Under the preferred voltage condition (1 V), the Co-PBAs electrode prepared in Example 1 was used as the cathode, and the electrochemical experimental method in Example 2 was used to explore the effect of the electrolyte type on the technical solution of the present invention.

[0086] The results are as follows Figure 6 As shown, Figure 6 This is a comparison diagram of the effects of different electrolytes on the Co-PBAs electrode as a cathode-assisted electrochemical lithium extraction at a voltage of 1V provided in Example 3 of the present invention. Figure 6 It can be concluded that K2SO4 and KNO3 solutions can be used as alternative electrolytes; the lithium extraction efficiency is reduced when Na2SO4 solution is used as the electrolyte because PBAs have a high affinity for K + Has higher preference and interaction strength for Na + The preference is slightly weaker; the use of H2SO4 solution and KCl solution will lead to non-selective leaching of transition metal ions in retired lithium battery materials and is not suitable as an electrolyte for electrochemical lithium extraction.

[0087] Example 4: Stability Test

[0088] The cycle test conditions refer to the electrochemical experimental method in Example 2, and the Co-PBAs electrode prepared in Example 1 is used as the cathode under the preferred voltage condition (1V); after each cycle, the Co-PBAs electrode is regenerated (10min) by applying an oxidation potential of 1V vs Ag / AgCl in a three-electrode electrolytic cell, and then enters the next cycle for testing.

[0089] The results are as follows Figure 7 As shown, Figure 7 This is a graph showing the experimental results of the cycle stability of the Co-PBAs electrode as a cathode-assisted electrochemical lithium extraction at a voltage of 1V provided in Example 4 of the present invention. Figure 7 It can be concluded that after 5 cycles, the lithium extraction efficiency of the technical solution of the present invention can still be maintained above 95%, proving its performance stability and application potential.

[0090] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for electrochemical lithium extraction from retired lithium batteries assisted by a pseudocapacitive cathode, characterized in that: The following steps are involved: a) providing an anode electrode and a cathode electrode; The anode electrode is an anode electrode made of recycled retired lithium battery positive electrode material, or is a retired lithium battery positive electrode plate; The cathode electrode contains a Prussian blue analogue, which is prepared by a mixed reaction of citrate, a transition metal salt and a cyanide in water, wherein the transition metal salt is one or more of a cobalt salt, an iron salt, a copper salt and a nickel salt, and the cyanide is ferrocyanide and / or ferrocyanide; b) immersing the anode electrode and the cathode electrode in an electrolyte and applying power to perform electrochemical lithium extraction.

2. The method according to claim 1, characterized in that In step a), the positive electrode material in the recycled retired lithium battery positive electrode material and the retired lithium battery positive plate is one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide and ternary lithium.

3. The method according to claim 1, characterized in that In step a), the anode electrode is prepared from the recycled retired lithium battery positive electrode material according to the following steps: The recycled retired lithium battery positive electrode material, a binder and a solvent are mixed to obtain an anode electrode slurry; The anode electrode slurry is coated on a current collector and dried to obtain an anode electrode.

4. The method according to claim 1, characterized in that: In step a), the Prussian blue analogue is prepared according to the following steps: Citrate, transition metal salt and cyanide are stirred and mixed in water, aged, solid-liquid separated, solid phase washed and dried to obtain a Prussian blue analogue.

5. The method according to claim 4, characterized in that The citrate is potassium citrate and / or sodium citrate; the transition metal salt is one or more of cobalt nitrate, iron nitrate, copper nitrate and nickel nitrate; the cyanide is potassium ferrocyanide and / or potassium ferrocyanide; the molar ratio of the citrate, the transition metal salt and the cyanide is (3-5):(1-3):

1.

6. The method according to claim 4, characterized in that The stirring and mixing time is 12 to 24 hours; the aging time is 12 to 24 hours; the solid-liquid separation method is centrifugal separation, and the centrifugal speed is 6000 to 12000 rpm; the drying temperature is 50 to 100°C.

7. The method according to claim 1, characterized in that In step a), the cathode electrode is prepared according to the following steps: mixing a Prussian blue analog, a binder and a solvent to obtain a cathode electrode slurry; The cathode electrode slurry is coated on a current collector and dried to obtain a cathode electrode.

8. The method according to claim 1, characterized in that In step b), the solute in the electrolyte is one or more of K2SO4, Na2SO4, KNO3, NaNO3 and NaCl; the concentration of the solute in the electrolyte is 0.01-0.1 mol / L.

9. The method according to claim 1, characterized in that: In step b), the electrochemical lithium extraction is carried out under stirring conditions.

10. The method according to claim 1, characterized in that Also includes: c) After the electrochemical lithium extraction is completed by applying power, carbonate is added to the electrolyte to recover the generated lithium carbonate precipitate.

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