Method for electrochemically extracting lithium from retired lithium battery with the assistance of pseudo-capacitive cathode

Abstract

The application belongs to the field of electrochemistry, and particularly relates to a method for electrochemically extracting lithium from a retired lithium battery with the assistance of a pseudo-capacitance 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 is a retired lithium battery positive plate; the cathode electrode contains Prussian blue analogues, the Prussian blue analogues are prepared by mixing and reacting citrate, transition metal salt and cyanide in water, and the transition metal salt is one or more of cobalt salt, iron salt, copper salt and nickel salt; b) immersing the anode electrode and the cathode electrode into an electrolyte, and performing electrochemical lithium extraction by electrification. In the method, the pseudo-capacitance material with lithium discharge characteristics is used as the cathode to replace the commonly used metal plate or carbon material, the pseudo-capacitance reaction with a more positive electrode potential is used to replace the hydrogen evolution reaction on the cathode of the existing system, and finally the low-energy-consumption and high-selectivity recovery of lithium is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrochemistry, and particularly relates to a method for electrochemical lithium extraction from retired lithium batteries assisted by a pseudo-capacitive cathode. BACKGROUND

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

[0003] Due to the rich lithium contained in the retired lithium battery, the content and purity are higher than that of natural mineral reserves, so it is considered as a high-quality "urban mine". Recycling lithium from retired lithium batteries is a key way to solve the disposal problem of retired batteries and realize the sustainable supply of lithium resources. However, the traditional wet and pyrometallurgical recycling processes generally have problems such as serious environmental pollution, high energy consumption, high lithium loss rate, and low recovery purity.

[0004] Recently, researchers have proposed a new technology of electrochemical lithium extraction from retired lithium batteries, which directly uses the positive electrode material of the retired lithium battery as the anode, relies on the application of voltage or in-situ generation of strong oxidizing free radicals to induce the oxidation reaction of transition metals in the electrode material, and couples the electrostatic repulsion of lithium ions on the anode to drive the selective leaching of lithium.

[0005] Compared with traditional processes, the electrochemical lithium extraction technology has the advantages of green process, high lithium recovery purity, etc., but also has problems such as low lithium leaching efficiency and high energy consumption. One of the key reasons for high energy consumption is that the cathode of the existing electrochemical lithium extraction system mainly occurs hydrogen evolution reaction, which generates hydrogen by reducing water molecules / protons, thereby driving the oxidation of metals 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 (<0V vs. RHE), the reaction energy barrier is high, and the kinetics is slow, which seriously restricts the lithium leaching efficiency of the anode (usually more than 3h is required for leaching). At the same time, in order to drive the leaching of lithium, a high voltage of 2.5V or more needs to be applied, thereby significantly increasing the energy consumption, further hindering the scale and commercial application of the technology. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a method for electrochemical lithium extraction from retired lithium batteries assisted by a pseudo-capacitive cathode. The pseudo-capacitive material with lithium repelling property is used as the cathode to replace the commonly used metal plate or carbon material, and the pseudo-capacitive reaction with a more positive electrode potential is used to replace the hydrogen evolution reaction on the cathode of the existing system, thereby significantly reducing the voltage and energy consumption of the whole electrochemical lithium extraction system, strengthening the lithium leaching on the anode, and finally realizing the low-energy consumption and high-selectivity recovery of lithium.

[0007] The application provides a method for electrochemically extracting lithium from a retired lithium battery with the aid of a pseudo-capacitance 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 a retired lithium battery positive plate.

[0010] The cathode electrode contains Prussian blue analogues, which are made by mixing citrate, transition metal salt and cyanide in water, the transition metal salt is one or more of cobalt salt, iron salt, copper salt and nickel salt, and the cyanide is ferricyanide and / or ferrocyanide.

[0011] b) immersing the anode electrode and the cathode electrode in an electrolyte and applying electricity to electrochemically extract lithium.

[0012] Preferably, in step a), the recycled 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 cobaltate, lithium manganate and ternary lithium.

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

[0014] Mixing the recycled retired lithium battery positive electrode material, the binder and the solvent to obtain an anode electrode slurry;

[0015] Coating the anode electrode slurry onto a current collector and drying to obtain an anode electrode.

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

[0017] Stirring and mixing citrate, transition metal salt and cyanide in water, aging, solid-liquid separation, washing the solid phase, and drying to obtain Prussian blue analogues.

[0018] Preferably, 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 ferricyanide 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 12-24h; the aging time is 12-24h; the solid-liquid separation method is centrifugal separation at a centrifugal speed of 6000-12000rpm; and the drying temperature is 50-100℃.

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

[0021] The Prussian blue analogues, the binder and the solvent are mixed to obtain a cathode electrode slurry;

[0022] The cathode electrode slurry is coated onto the 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; the concentration of the solute in the electrolyte is 0.01-0.1 mol / L.

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

[0025] Preferably, the method further comprises:

[0026] c) after the electrochemical lithium extraction by power supply is completed, adding a carbonate into the electrolyte to recover the generated lithium carbonate precipitate.

[0027] Compared with the prior art, the present application provides a method for electrochemically extracting lithium from a retired lithium battery assisted by a pseudo-capacitive cathode, comprising the following steps: a) providing an anode electrode and a cathode electrode; the anode electrode is an anode electrode made of recycled positive electrode material of a retired lithium battery, or is a positive electrode plate of a retired lithium battery; the cathode electrode contains a Prussian blue analogue, which is prepared by mixing citrate, transition metal salt and cyanide in water, the transition metal salt is one or more of cobalt salt, iron salt, copper salt and nickel salt, and the cyanide is ferricyanide and / or ferrocyanide; b) immersing the anode electrode and the cathode electrode into an electrolyte and performing electrochemical lithium extraction by power supply. In the present application, the pseudo-capacitive cathode is used to adsorb a large amount of cations (non-lithium ions) in the electrolyte into the material lattice, while 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 prevent the lithium ions released by the anode from being adsorbed by the cathode again, a pseudo-capacitive material (Prussian blue analogue, PBA) with lithium repelling property is prepared by coprecipitation method. Then it is made into a cathode electrode and combined with the retired lithium battery material (such as lithium iron phosphate LFP, lithium cobaltate LCO, lithium manganate LMO, ternary lithium NCM, etc.) as an anode electrode to construct an electrochemical lithium extraction system. By simulating the charging process of a lithium battery, efficient and low-consumption electrochemical lithium extraction is realized. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only only some embodiments of the present application, and all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative labor also belong to the protection scope of the present application.

[0029] Figure 1 is the XRD spectrum of Co-PBAs provided by the embodiment 1 of the present application;

[0030] Figure 2 is the verification result graph of the lithium extraction characteristics of the Co-PBAs electrode provided by the embodiment 1 of the present application;

[0031] Figure 3 is the verification result graph of the lithium extraction characteristics of the Fe / Cu / Ni-PBAs electrode provided by the embodiment 1 of the present application;

[0032] Figure 4 is the comparison graph of the effects of Co-PBAs electrode and Pt as cathode auxiliary electrochemical lithium extraction under different voltages provided by the embodiment 2 of the present application;

[0033] Figure 5 is the comparison graph of the effects of various metal-based PBAs electrodes and Pt as cathode auxiliary electrochemical lithium extraction under 1V voltage provided by the embodiment 2 of the present application;

[0034] Figure 6 is the comparison graph of the effects of different electrolytes on Co-PBAs electrode as cathode auxiliary electrochemical lithium extraction under 1V voltage provided by the embodiment 3 of the present application;

[0035] Figure 7 is the cycle stability experimental result graph of Co-PBAs electrode as cathode auxiliary electrochemical lithium extraction under 1V voltage provided by the embodiment 4 of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely as follows. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor also belong to the protection scope of the present application.

[0037] The present application provides a method for pseudo-capacitance cathode auxiliary electrochemical lithium extraction of retired lithium battery, 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 a retired lithium battery positive plate;

[0040] The cathode electrode contains Prussian blue analogues, which are made by mixing citrate, transition metal salt and cyanide in water, the transition metal salt is one or more of cobalt salt, iron salt, copper salt and nickel salt, and the cyanide is ferricyanide and / or ferrocyanide;

[0041] b) Immersing the anode electrode and cathode electrode in an electrolyte and performing electrochemical lithium extraction by applying electricity.

[0042] In the method provided by the application, in step a), the positive electrode material in the recycled retired lithium battery positive electrode material and the positive electrode material in the retired lithium battery positive plate includes but is not limited to one or more of lithium iron phosphate LFP, lithium cobaltate LCO, lithium manganate LMO and ternary lithium NCM, and preferably ternary lithium NCM.

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

[0044] Mixing the recycled retired lithium battery positive electrode material, the binder and the solvent to obtain an anode electrode slurry;

[0045] Coating the anode electrode slurry on a current collector and drying to obtain an anode electrode.

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

[0047] In the method provided by the present application, 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 for the preparation of the Prussian blue analogue is a cobalt salt.

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

[0049] The citrate, transition metal salt and cyanide are mixed by stirring in water, aged, solid-liquid separated, the solid phase is washed and dried to obtain the Prussian blue analogue.

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

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

[0052] The Prussian blue analogue, binder and solvent are mixed to obtain a cathode electrode slurry;

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

[0054] In the above-mentioned step of preparing the cathode electrode provided by the present application, the binder includes but is not limited to a perfluorosulfonic acid type polymer solution (Nafion solution); the ratio of the amount of the binder to the Prussian blue analogue is preferably 50 μL:(20-100) mg, and specifically can be 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 isopropyl alcohol; the ratio of the amount of the solvent to the Prussian blue analogue is preferably 950 μL:(20-100) mg, and specifically can be 950 μL:20 mg, 950 μL:30 mg, 950 μL:40 mg, 950 μL:50 mg, 950 μL:60 mg, 950 μL:70 mg, 950 μL:80 mg, 950 μL:90 mg or 950 μL:100 mg; the current collector includes but is not limited to carbon paper; and the drying temperature is preferably 50-100°C, and specifically can be 50°C, 60°C, 70°C, 80°C, 90°C or 100°C.

[0055] In the method provided by the present application, in step b), the solute in the electrolyte is preferably one or more of K2SO4, Na2SO4, KNO3, NaNO3 and NaCl, and more preferably K2SO4; and the concentration of the solute in the electrolyte is preferably 0.01-0.1 mol / L, and specifically can be 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, and most preferably 0.05 mol / L.

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

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

[0058] In the method provided by the application, the following steps are preferably further included:

[0059] c) After the power supply for electrochemical lithium extraction is stopped, a carbonate is added to the electrolyte, and a generated lithium carbonate precipitate is recovered.

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

[0061] (1) By means of the preferred cathode material, a cathode reaction is ingeniously designed, and a pseudo-capacitance reaction for electrode potential correction is selected to replace the hydrogen evolution reaction on the cathode of the existing system, and after being coupled with the lithium selective leaching reaction on the anode, the gap between the oxidation-reduction potentials of the anode and the cathode is greatly reduced, so that efficient electrochemical lithium extraction can be realized at an ultra-low voltage, and problems such as side reactions of water electrolysis and electrode material falling caused by possible gas are effectively avoided, and the faradic efficiency is greatly improved.

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

[0063] For a clearer understanding, the following examples are used for detailed description. In the following examples of the application, unless otherwise specified, all operations are carried out at room temperature and under normal pressure.

[0064] Example 1: Verification of lithium removal characteristics of pseudo-capacitance cathode (PBAs)

[0065] (1) Synthesis of cobalt-based prussian blue analogues (Co-PBAs):

[0066] Potassium citrate and cobalt nitrate were uniformly dispersed in 100 mL of water, and were recorded as solution 1; potassium ferricyanide was uniformly dispersed in 100 mL of water, and was recorded as solution 2; wherein the concentration of cobalt nitrate in solution 1 was 0.2 mol / L, and the molar ratio of potassium citrate, cobalt nitrate and potassium ferricyanide was 4:2:1;

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

[0068] The Co-PBAs synthesized are subjected to XRD detection, and the results are shown in Figure 1 Figure 1 Figure 1 is an XRD spectrum of the Co-PBAs provided in Example 1 of the present application. As can be seen from Figure 1 , the Co-PBAs synthesized in the present example have four main peaks in the range of 17-40 DEG, corresponding to the (200), (220), (400), and (420) crystal planes of the face-centered cubic structure, indicating that the Prussian blue analogues are successfully synthesized.

[0069] (2) Verification of the lithium stripping property of the Co-PBAs electrode:

[0070] 30 mg of Co-PBAs are taken, mixed with 50 μL of Nafion (binder) and 950 μL of isopropyl alcohol, and uniformly coated on a 2x2 cm 2 of carbon paper which is washed and cut, and dried to form a Co-PBAs electrode.

[0071] The Co-PBAs electrode is subjected to alkali metal cation adsorption experiments of single salt and mixed salt by using a Chenhua electrochemical workstation (CHI760e), and the specific experimental process is as follows: a 100 mL three-electrode electrolytic cell is used, the volume of the electrolyte is 50 mL, and 1 mmol / L of K2SO4, Na2SO4, and Li2SO4 single salt solutions and 1 mmol / L K2SO4+1 mmol / L Li2SO4 and 1 mmol / L Na2SO4+1 mmol / L Li2SO4 mixed salt solutions are respectively prepared; the working electrode is a 2x2 cm 2 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 according to the change of the alkali metal cation concentration in the electrolyte before and after the reaction detected by inductively coupled plasma optical emission spectrometer (ICP-OES), the adsorption capacity of the Co-PBAs electrode to different alkali metal cations can be obtained.

[0072] The results are shown in Figure 2 Figure 2 ​​is a verification result graph of the lithium rejection property of the Co-PBAs electrode provided in Embodiment 1 of the present application. Through Figure 2 It can be seen that the Co-PBAs electrode has a high adsorption capacity for potassium ions, more than 70 mg / g, an adsorption capacity for sodium ions more than 35 mg / g, and an adsorption capacity for lithium ions less than 0.2 mg / g, almost unable to adsorb lithium ions, which indicates that the Co-PBAs can be used as a cathode auxiliary for electrochemical lithium extraction from retired lithium batteries, almost without affecting the concentration and recovery of lithium in the electrolyte, proving the feasibility of the technical solution of the present application.

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

[0074] Referring to the synthesis method in (1), replace the cobalt nitrate with iron nitrate, copper nitrate and nickel nitrate respectively to obtain iron-based Prussian blue analogues (Fe-PBAs), copper-based Prussian blue analogues (Cu-PBAs) and nickel-based Prussian blue analogues (Ni-PBAs) in turn.

[0075] (4) Verification of lithium rejection property of Fe / Cu / Ni-PBAs electrode:

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

[0077] The results are shown in Figure 3 , and Figure 3 is a verification result graph of the lithium rejection property of the Fe / Cu / Ni-PBAs electrode provided in Embodiment 1 of the present application. Through Figure 3 It can be seen that the PBAs electrodes of various metal bases have an adsorption capacity for lithium ions less than 0.1 mg / g, all showing strong lithium rejection properties.

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

[0079] In order to show the advantages of the technical solution of the present application, the Co-PBAs electrode prepared in Embodiment 1 and Pt were used as cathodes, and electrochemical lithium extraction experiments were performed using CHI760e, and the specific experimental process was as follows:

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

[0081] As shown in the results, Figure 4 Figure 4 is a comparison chart of the effects of Co-PBAs electrodes and Pt as cathode auxiliary electrochemical lithium extraction under different voltages provided by the embodiment 2 of the present application. By Figure 4 It can be concluded that the present technical solution selects the pseudo-capacitance reaction of electrode potential correction to replace the hydrogen evolution reaction on the cathode of the existing system, which is coupled with the lithium selective leaching reaction on the anode, thereby greatly reducing the gap between the oxidation and reduction potentials of the anode and cathode, lowering the applied voltage required for lithium extraction, and accelerating the lithium leaching kinetics under the same voltage.

[0082] Specifically, when Pt is used as the cathode auxiliary electrochemical lithium extraction, about 28% of lithium is leached out under the voltage of 1 V for 2 h. In comparison, when the Co-PBAs electrode is used as the cathode, 100% of lithium is leached out under the conditions of 1 V and 2 h, and the leaching selectivity can reach about 100%, and the pH of the electrolyte before and after the reaction is almost unchanged, which confirms that the pseudo-capacitance cathode auxiliary can effectively avoid the side reaction of water electrolysis, achieve the goal of improving the Faraday efficiency and reducing the energy consumption, and embodies the advantages of the present technical solution.

[0083] Further, under the preferred voltage condition (1 V), various metal-based PBAs electrodes prepared in the embodiment 1 are used as the cathode to test the effect of auxiliary electrochemical lithium extraction. As shown in the results, Figure 5 Figure 5 is a comparison chart of the effects of various metal-based PBAs electrodes and Pt as cathode auxiliary electrochemical lithium extraction under the voltage of 1 V provided by the embodiment 2 of the present application. By Figure 5 It can be concluded that when various metal-based PBAs electrodes are used as the auxiliary, more than 90% of lithium can be leached out under the conditions of 1 V and 2 h, 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 universality of the present technical solution in PBAs materials.

[0084] Embodiment 3: Reaction condition optimization

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

[0086] The results are shown in the following table.​​Figure 6 Figure 6 is a comparison chart of the effect of different electrolytes on the Co-PBAs electrode as a cathode auxiliary electrochemical lithium extraction provided by embodiment 3 under 1V voltage. Through Figure 6 It can be concluded that K2SO4 and KNO3 solutions can be used as alternative electrolytes; the lithium extraction efficiency is reduced when using Na2SO4 solution as the electrolyte, because PBAs have higher preference and interaction strength for K + slightly weaker preference for Na + ; using H2SO4 solution and KCl solution will cause non-selective leaching of transition metal ions in the retired lithium battery material, 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 test 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 subjected to an oxidation potential of 1V vs Ag / AgCl in a three-electrode electrolytic cell for regeneration (10min), and then enters the next cycle for testing.

[0089] The results are shown in Figure 7 , and Figure 7 is a cycle stability test result chart of the Co-PBAs electrode as a cathode auxiliary electrochemical lithium extraction provided by embodiment 4 under 1V voltage. Through Figure 7 It can be concluded that the lithium extraction efficiency of the present application can still be maintained at more than 95% after 5 cycles, proving its performance stability and application potential.

[0090] The above is only the preferred embodiment of the present application, and it should be noted that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered within the scope of protection of the present application.​

Claims

1. A method for electrochemically extracting lithium from a retired lithium battery assisted by a pseudo-capacitive cathode, characterized in that, The method comprises 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 plate; The cathode electrode contains Prussian blue analogues, which are prepared by mixing citrate, transition metal salt and cyanide in water, the transition metal salt is one or more of cobalt salt, iron salt, copper salt and nickel salt, and the cyanide is ferricyanide and / or ferrocyanide; b) immersing the anode electrode and cathode electrode in an electrolyte and applying electricity to perform electrochemical lithium extraction.

2. The method of claim 1, wherein, In step a), the positive electrode material in the recycled retired lithium battery positive electrode material and the positive electrode material in the retired lithium battery positive plate is one or more of lithium iron phosphate, lithium cobaltate, lithium manganate and ternary lithium.

3. The method of claim 1, wherein, In step a), the recycled retired lithium battery positive electrode material is made into an anode electrode according to the following steps: Mixing the recycled retired lithium battery positive electrode material, the binder and the solvent to obtain an anode electrode slurry; Coating the anode electrode slurry onto a current collector and drying to obtain an anode electrode.

4. The method of claim 1, wherein, In step a), the Prussian blue analogues are prepared according to the following steps: Stirring and mixing citrate, transition metal salt and cyanide in water, aging, solid-liquid separation, washing the solid phase, and drying to obtain Prussian blue analogues.

5. The method of claim 4, wherein, 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 ferricyanide and / or potassium ferrocyanide; and the molar ratio of the citrate, transition metal salt and cyanide is (3-5):(1-3):

1.

6. The method of claim 4, wherein, The stirring and mixing time is 12-24 h; the aging time is 12-24 h; the solid-liquid separation method is centrifugal separation at a centrifugal speed of 6000-12000 rpm; and the drying temperature is 50-100℃.

7. The method of claim 1, wherein, In step a), the cathode electrode is prepared according to the following steps: Mixing the Prussian blue analogues, the binder and the solvent to obtain a cathode electrode slurry; Coating the cathode electrode slurry onto a current collector and drying to obtain a cathode electrode.

8. The method of claim 1, wherein, 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 0.01-0.1 mol / L.

9. The method of claim 1, wherein, In step b), the electrochemical lithium extraction is carried out under stirring.

10. The method of claim 1, wherein, Further comprising: c) after the end of the electricity application for electrochemical lithium extraction, adding carbonate to the electrolyte to recover the generated lithium carbonate precipitate.

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