Electrochemical unit, device and method for continuously regenerating retired positive electrode material and seawater desalination method

Abstract

The invention belongs to the field of battery recovery, and particularly relates to an electrochemical unit, device and method for continuously regenerating a retired positive electrode material and a seawater desalination method. The electrochemical unit comprises an electrolytic tank, an anode chamber, a cathode chamber and a lithium ion selective exchange membrane; the anode chamber and the cathode chamber are arranged in the electrolytic tank; the lithium ion selective exchange membrane is arranged between the anode chamber and the cathode chamber; the anode chamber is used for accommodating brine; and the cathode chamber is used for accommodating retired conductive slurry. The retired conductive paste is prepared by selectively adding the surfactant and the conductive agent, and uniformly stirring and dispersing the surfactant and the conductive agent. The slurry has fluidity, so that the reaction can realize continuous production. And the liquid subjected to subsequent solid-liquid separation can be repeatedly used for preparing the retired conductive slurry, so that the environmental pollution is small.

Description

Technical Field

[0001] The present invention belongs to the field of battery recycling, and in particular relates to an electrochemical unit, a device and a method for continuous regeneration of retired positive electrode materials, and a seawater desalination method. Background Art

[0002] Since 2017, new energy vehicles have developed rapidly due to their advantages such as environmental protection and energy saving. By 2024, the penetration rate of new energy vehicles is close to 40%, which reflects that the share of new energy vehicles in the automobile market is growing rapidly. By the end of 2023, the stock of lithium-ion batteries, one of the core power sources of new energy vehicles, will reach 940GWh, which highlights the importance of lithium-ion batteries in the new energy vehicle industry. With the rapid popularization of new energy vehicles, how to deal with a large number of retired lithium batteries has become an urgent problem to be solved. The recycling and regeneration of retired lithium batteries not only helps to reduce environmental pollution, but is also an important way to promote the sustainable development of the electric vehicle industry. The positive electrode material of lithium-ion batteries accounts for about 30% to 50% of the battery cost, so the recycling and regeneration of positive electrode materials are of great significance to reducing costs and improving resource utilization efficiency.

[0003] There are two main recycling technologies: 1. Using dry metallurgy or hydrometallurgy to leach and crystallize lithium ions from retired cathode materials to obtain lithium carbonate, lithium hydroxide and other lithium salt products, which are then synthesized with precursors to form regenerated cathode materials. 2. Using lithium replenishers and other lithium replenishment methods to directly repair and regenerate retired cathode materials.

[0004] Existing methods for regenerating retired lithium-ion battery positive electrode materials usually use a method of grinding and calcining with the addition of a lithium supplement or using an electrochemical method to achieve regeneration. The addition of a lithium supplement will introduce additional organic matter, increase costs and make the product uncontrollable. The electrochemical method usually requires the retired positive electrode material to be reduced to be coated on the electrode surface in a solid phase as the negative electrode of the subsequent assembled battery, and then a negative electrode potential is applied for reduction. After reduction, the battery is disassembled to obtain the repaired regenerated positive electrode powder. This method is complicated to operate, requires sufficient lithium source to be supplemented, and cannot continuously produce regenerated positive electrode powder.

[0005] Patent CN117855658A achieves ion transfer between the cathode and the anode by setting up a cathode chamber and an anode chamber and an ion exchange membrane in a closed container, so that the retired lithium iron phosphate powder reacts with a mixed solution of reducing organic acid and lithium salt to generate lithium iron phosphate slurry in situ. However, this method has the following disadvantages: (1) The cost is relatively high, and reducing organic acid and lithium salt need to be added to the cathode and anode chambers. (2) Continuous production is not possible, and the retired lithium iron phosphate powder needs to be manually placed in the cylindrical cathode for reaction. (3) When the lithium iron phosphate on the anode side generates iron phosphate, the reaction on this side is transformed into an oxygen evolution reaction of electrolyzed water, the pH value of the solution decreases, and the iron phosphate dissolves in the acid, resulting in failure of the generation reaction.

[0006] Patent CN117940610A provides an electrochemical lithium extraction electrode, an electrochemical lithium extraction device and a lithium extraction method, the purpose of which is to use electrochemical means to extract lithium from salt lakes. However, this method has the following shortcomings: (1) After the cathode electrochemical adsorption, it is placed in the anode for desorption, which consumes twice the amount of electricity to achieve the adsorption and desorption purification of lithium ions. (2) There is no discharge channel for the gas that may be generated by electrolysis. (3) It is necessary to control the initial lithium content of the cathode active material and the anode active material. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide an electrochemical unit, a device and a method for continuous regeneration of retired positive electrode materials and a seawater desalination method.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] An electrochemical unit for continuous regeneration of retired positive electrode materials comprises an electrolytic cell, an anode chamber and a cathode chamber arranged in the electrolytic cell, and a lithium ion selective exchange membrane arranged between the anode chamber and the cathode chamber; the anode chamber is used to contain brine; the cathode chamber is used to contain retired conductive slurry.

[0010] The retired conductive slurry comprises retired positive electrode powder, a surfactant, a conductive agent and water;

[0011] Preferably, the retired positive electrode powder is one of nickel-cobalt-manganese ternary, lithium iron phosphate, and lithium cobalt oxide;

[0012] The surfactant is hydroxymethyl cellulose, polypyrrolidone, polyethylene glycol octylphenyl ether, carboxymethyl cellulose (CMC), etc.; preferably, the surfactant is hydroxymethyl cellulose;

[0013] The conductive agent is carbon nanotube, carbon black, SuperP, graphene, carbon fiber, etc.; preferably, the conductive agent is carbon black;

[0014] The mass ratio of retired positive electrode powder, surfactant, conductive agent and solvent is (19.8-198): (0.2-2): (0.4-4): (179.6-1796); preferably, the mass ratio is 99:1:2:898.

[0015] The retired conductive slurry is prepared by the following method: S201, the retired batteries are crushed and screened to obtain retired positive electrode powder; preferably, mechanical disassembly or manual disassembly is adopted; S202; surfactant and conductive agent are added and uniformly dispersed until the slurry is uniform and has a certain conductivity, and the solid content of the retired conductive slurry is ≤25%; preferably 5-25%;

[0016] An anode is arranged in the anode chamber; a cathode is arranged in the cathode chamber; the anode and the cathode are connected via a power supply;

[0017] The anode and cathode independently include a current collector and a mesh electrode; the thickness of the current collector is independently 4 to 8 mm; the surface area is 100 to 400 cm 2 ;

[0018] The current collector is an inert electrode, including at least one of platinum and graphite plate, and the structure includes a parallel plate or a straight flow field plate;

[0019] The mesh electrode comprises conductive high-pore graphite felt or conductive carbon fiber skeleton; preferably, the mesh electrode has a pore size of 100 to 300 microns.

[0020] The lithium ion exchange membrane is one of a lithium lanthanum titanate LLTO ceramic membrane, a SPEEK composite membrane, and a two-dimensional sub-nanometer hydrated layered silicate membrane.

[0021] The present invention also includes an electrochemical device, including a parallel type or a series type;

[0022] The series type includes a plurality of electrochemical units for continuously regenerating the retired positive electrode materials connected in series; the anode chamber of the first electrochemical unit is connected to the brine storage tank; the cathode chamber of the terminal electrochemical unit is connected to the slurry tank;

[0023] The parallel type includes a plurality of electrochemical units for continuously regenerating the retired positive electrode materials in parallel; the brine storage tank and the slurry tank are respectively connected to the anode chamber and the cathode chamber of each electrochemical unit.

[0024] The present invention also includes a method for continuous regeneration of retired positive electrode materials, using the electrochemical device.

[0025] Specifically, the process includes the following steps: S301, pumping brine into the anode chamber and pumping retired conductive slurry into the cathode chamber, wherein the anode and the cathode form an electrode pair; S302, applying voltage through a power supply to perform electrolysis, wherein a chloride ion oxidation reaction occurs at the anode to generate chlorine gas, and lithium ions in the brine in the anode chamber enter the cathode chamber through an ion exchange membrane under the action of an external electric field, and the oxidized positive electrode material in the retired conductive slurry in the cathode chamber undergoes a corresponding reduction reaction and lithium ion embedding, thereby repairing and regenerating the retired lithium-ion battery positive electrode material; preferably, the DC voltage applied by the power supply is 0.1 to 3 V, and the current density is 10 to 200 mA / cm 2 .

[0026] The process also includes S303, performing solid-liquid separation on the repaired and regenerated positive electrode material of the battery, and obtaining a solid as a positive electrode material precursor; and calcining or carbon-coating the positive electrode material precursor to finally obtain a regenerated positive electrode material.

[0027] Nickel-cobalt-manganese ternary is calcined at 700-1200°C; lithium iron phosphate is calcined at 800-1000°C; lithium cobalt oxide is calcined at 700-1000°C; the calcination time is 3-24h.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) In the electrochemical device constructed by the present invention, the high-pore graphite felt and the conductive carbon fiber skeleton can provide a reaction site with a high specific surface area for the retired positive electrode material, and the formula of the retired conductive slurry also ensures the conductive network of the slurry; the lithium ion selective exchange membrane blocks the interference of other metal cations in the brine; the presence of the pump pumps the electrolytic reaction raw materials into the reaction chamber to increase the reaction rate, and the raw materials flow out from the output pipeline after the reaction, which is convenient for continuous large-scale production; and the retired positive electrode material does not need to strictly control the initial lithium content.

[0030] (2) The present invention constructs a retired conductive slurry, which is prepared by selectively adding a surfactant and a conductive agent, stirring and uniformly dispersing. Since the slurry has fluidity, this reaction can be produced continuously. The liquid after subsequent solid-liquid separation can be used to repeatedly prepare retired conductive slurry, which has little pollution to the environment. The generated chlorine gas is discharged through the gas outlet pipe and collected for disinfection of fresh water.

[0031] (3) The electrochemical method used in the present invention promotes the reduction of retired positive electrode materials by applying an external power source, so as to regenerate the structure of retired positive electrode materials. Under the action of the external electric field, the lithium ions in the brine in the anode chamber migrate to the cathode chamber, and chlorine gas is generated at the same time. The repair of retired lithium-ion battery positive electrode materials is comprehensively realized, and the recovery and utilization of lithium resources in the brine are also realized, which has a good industrial application prospect.

[0032] (4) The electrochemical performance of the regenerated lithium battery positive electrode material prepared by the electrochemical method of the present invention is relatively stable and excellent, which is equivalent to the electrochemical performance of the lithium battery positive electrode material before retirement. At the same time, the lithium ion concentration in the brine is significantly reduced, which can realize the recovery and reuse of lithium resources. Among them, the retired lithium battery positive electrode materials include but are not limited to nickel-cobalt-manganese ternary, lithium iron phosphate, lithium cobalt oxide and other materials according to different systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the principle of an electrochemical unit for continuous regeneration of positive electrode materials of retired lithium-ion batteries provided by an embodiment of the present invention;

[0034] Figure 2 This is a diagram of the preparation process of the positive electrode slurry of retired lithium-ion batteries according to an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the electrochemical method flow chart of an embodiment of the present invention;

[0036] Figure 4 This is a flow chart of a lithium recovery and retired positive electrode material repair system according to an embodiment of the present invention;

[0037] Figure 5 Schematic diagram of an electrochemical device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and the best embodiments.

[0039] In the process of realizing the concept of the present invention, with the help of the idea that the liquid flow battery energy storage material can flow, the retired positive electrode material is evenly dispersed, a conductive agent is added to make a slurry, and a uniform retired conductive slurry is configured. The slurry is pumped into the reaction chamber by a pump, and flows out of the reaction chamber after electrolysis, thereby realizing continuous electrolysis reaction and regeneration of the positive electrode material; at the same time, the selection of the lithium source for repairing the positive electrode material is selected from the ion concentrated product brine after seawater / salt lake desalination, and the lithium ion exchange membrane is used to realize the recovery and utilization of lithium resources in seawater / salt lake, and chlorine gas is generated in the anode chamber.

[0040] Figure 1 The schematic diagram of the principle of the electrochemical unit for continuous regeneration of retired lithium-ion battery positive electrode materials provided by the embodiments of the present invention. Specifically, according to some embodiments of the present invention, Figure 1 An electrochemical unit for continuous regeneration of retired positive electrode materials is shown, comprising an electrolytic cell 1, an anode chamber 11 and a cathode chamber 12 arranged in the electrolytic cell, and a lithium ion selective exchange membrane 13 arranged between the anode chamber 11 and the cathode chamber 12; the anode chamber is used to accommodate brine; the cathode chamber is used to accommodate retired conductive slurry.

[0041] The anode chamber 11 and the cathode chamber 12 have the same volume and can accommodate 50-200 mL of brine and conductive slurry respectively, for example, 50 mL, 100 mL, 150 mL or 200 mL, but not limited thereto.

[0042] The electrode assembly 2 is matched in the electrolytic cell 1, including an anode 21 disposed in the anode chamber; a cathode 22 disposed in the cathode chamber; the anode 21 and the cathode 22 are connected via a power source 3;

[0043] The anode and cathode independently include a current collector and a mesh electrode;

[0044] The thickness of the current collector is independently 4 to 8 mm; for example, it can be 4 mm, 5 mm, 6 mm, 7 mm or 8 mm, but it is not limited thereto. The surface area is 100 to 400 cm 2 ; For example, it can be 100cm 2 , 200cm 2 , 300cm 2 or 400cm 2 , but not limited thereto. The current collector is an inert electrode, including at least one of platinum and graphite plate, and the structure includes a parallel plate or a straight flow field plate;

[0045] The mesh electrode is used to ensure uniform flow without blockage and sufficient reaction, including conductive high-pore graphite felt or conductive carbon fiber skeleton; the tortuosity is low, and the mesh electrode pore size is 100-300 microns. For example, it can be 50 microns, 100 microns, 150 microns, 200 microns, 250 microns or 300 microns, but it is not limited to this.

[0046] The lithium ion exchange membrane 13 allows only lithium ions to pass into the cathode chamber 12 and blocks other cations in the brine. It is one of lithium lanthanum titanium oxide LLTO ceramic membrane, SPEEK composite membrane, and two-dimensional sub-nanometer hydrated layered silicate membrane.

[0047] The electrochemical unit also includes a slurry tank 5 and a brine tank 6, which are used to respectively contain the retired conductive slurry before and after the electrochemical reaction, the regenerated positive electrode slurry and the brine before and after the reaction, and other ion solutions. At the same time, it is equipped with corresponding pumps 3, gas pipelines 7, liquid pipelines 8, etc. The gas pipeline 7 is connected to the anode chamber 11 to discharge chlorine for collection.

[0048] The present invention also includes an electrochemical device, including a parallel type or a series type ( Figure 5Shown); the series type includes a plurality of electrochemical units for continuously regenerating retired positive electrode materials connected in series; the anode chamber of the head electrochemical unit is connected to the brine storage tank; the cathode chamber of the terminal electrochemical unit is connected to the slurry tank; the parallel type includes a plurality of electrochemical units for continuously regenerating retired positive electrode materials connected in parallel; the brine storage tank and the slurry tank are respectively connected to the anode chamber and cathode chamber of each electrochemical unit.

[0049] According to some embodiments of the present invention, the electrochemical unit is regarded as a monomer. In practical applications, the electrode areas of the anode 21 and the cathode 22 in the electrolytic cell 1 can be enlarged, and multiple monomers can be connected in parallel to achieve large-scale expansion; at the same time, multiple monomers can be connected in series to allow the slurry to flow through multiple monomers in sequence, thereby improving the sufficiency of the electrode reaction and improving the purity of the regenerated positive electrode material.

[0050] According to some embodiments of the present invention, the electrochemical method flow diagram is as follows Figure 3 , further comprising: pumping anode brine and cathode retired conductive slurry into the electrolytic cell 1 in the form of pumping, the active material pumped in under the condition of an external power supply 3 participates in the reaction, the anode 21 undergoes a chloride ion oxidation reaction to generate chlorine gas, the lithium ions in the brine in the anode chamber 11 pass through the ion exchange membrane 13 into the cathode chamber 12 under the action of an external electric field, the oxidized positive electrode material in the retired conductive slurry in the cathode chamber 12 undergoes a corresponding reduction reaction and lithium ion embedding, and the retired lithium ion battery positive electrode material is repaired; preferably, the retired lithium ion battery positive electrode slurry is prepared as follows Figure 2 After the waste positive electrode sheets are crushed and screened, surfactants and conductive agents are added and evenly dispersed until the slurry is uniform and has a certain conductivity, with a solid content of ≤25%, ensuring that the slurry has a suitable viscosity and is conducive to flow.

[0051] According to some embodiments of the present invention, the electrochemical method further includes: solid-liquid separation of the repaired slurry, including but not limited to adding flocculants, filtration, centrifugal separation and the like; further calcining the separated solid to increase the crystallinity of the material, thereby improving the cycle performance; preferably, the calcination temperature can be divided into: nickel-cobalt-manganese ternary (700-1200°C), lithium iron phosphate (800-1000°C), lithium cobalt oxide (700-1000°C), etc. according to the type of positive electrode material, and the calcination time is 3-24h. If carbon coating is considered, a commercial carbon source can be selected.

[0052] According to some embodiments of the present invention, the solid content of the retired conductive paste is 5-25%, for example, 5%, 10%, 15%, 20%, 25% but not limited thereto.

[0053] According to some embodiments of the present invention, the anode chamber 11 and the cathode chamber 12 have the same volume and can accommodate 50-200 mL of brine and conductive slurry respectively, for example, 50 mL, 100 mL, 150 mL or 200 mL, but not limited thereto.

[0054] According to some embodiments of the present invention, the electrochemical device further comprises a slurry tank and a brine tank for respectively containing retired conductive slurry before and after the electrochemical reaction, regenerated positive electrode slurry, and brine before and after the reaction, and other ion solutions.

[0055] According to some embodiments of the present invention, the retired conductive slurry includes retired positive electrode powder, a surfactant, a conductive agent and water;

[0056] Preferably, the retired positive electrode powder is one of nickel-cobalt-manganese ternary, lithium iron phosphate, and lithium cobalt oxide;

[0057] The surfactant is hydroxymethyl cellulose, polypyrrolidone, polyethylene glycol octylphenyl ether, carboxymethyl cellulose CMC, etc.; preferably, the surfactant is hydroxymethyl cellulose;

[0058] The conductive agent is carbon nanotube, carbon black, SuperP, graphene, carbon fiber, etc.; preferably, the conductive agent is carbon black;

[0059] The mass ratio of retired positive electrode powder, surfactant, conductive agent and solvent is (19.8-198): (0.2-2): (0.4-4): (179.6-1796); specifically, it can be 19.8:0.2:0.4:179.6, 99:1:2:898, 198:2:4:1796, etc.; preferably, the mass ratio is 99:1:2:898.

[0060] According to some embodiments of the present invention, a method for preparing a conductive paste is also provided, using Figure 2 The process includes operations S201 to S202.

[0061] S201, retired batteries are crushed and screened to obtain retired positive electrode powder; preferably, mechanical or manual disassembly is adopted; S202; surfactant and conductive agent are added, and evenly dispersed until the slurry is uniform and has a certain conductivity, and the solid content of the retired conductive slurry is ≤25%; preferably 5-25%; for example, it can be 5%, 10%, 15%, 20%, 25% but not limited thereto.

[0062] The retired conductive slurry is prepared in a homogenization tank, and the stirring speed of the homogenization tank is 10r / min to 40r / min for revolution, for example, 10r / min, 20r / min, 30r / min or 40r / min, but not limited to this; and 800r / min to 1200r / min for rotation, for example, 800r / min, 900r / min, 1000r / min, 1100r / min or 1200r / min, but not limited to this.

[0063] According to some embodiments of the present invention, a method for continuous regeneration of retired positive electrode materials is also provided. Figure 3 The present invention provides a flowchart of a method.

[0064] S301, pumping brine into the anode chamber 11, and pumping the retired conductive slurry into the cathode chamber 12, wherein the anode 21 and the cathode 22 form an electrode pair.

[0065] S302, applying voltage through the power supply 3 for electrolysis, the anode 21 undergoes a chloride ion oxidation reaction to generate chlorine gas, and the lithium ions in the brine in the anode chamber 11 enter the cathode chamber 12 through the ion exchange membrane 13 under the action of the external electric field, and the oxidized positive electrode material in the retired conductive slurry in the cathode chamber 12 undergoes a corresponding reduction reaction and lithium ion embedding, thereby repairing and regenerating the retired lithium-ion battery positive electrode material.

[0066] According to some embodiments of the present invention, the anode 21 undergoes an oxidation reaction of chloride ions, and the reaction process is as follows.

[0067] 2Cl - -2e - →Cl2(g)E≈4.4V vs.Li / Li +

[0068] According to some embodiments of the present invention, the cathode 22 undergoes reduction of the positive electrode material and insertion of lithium ions. x Co y Mn z Taking the reaction of O2, where x+y+z=1) and LiCoO2 as an example, the reaction process is as follows.

[0069] L i 1-x FePO4+xLi + +xe - →LiFePO4 E≈3.4V vs.Li / Li +

[0070] L i 1-x MO2+xL i + +xe- →LiMO2 E≈(3.5~4.3V)vs.L i / L i +

[0071] L i 1-x CoO2+xLi + +xe - →LiCoO2 E≈(3.7V)vs.Li / Li +

[0072] According to some embodiments of the present invention, the flow rate of the pump is 50 to 200 mL / min, for example, 50 mL / min, 100 mL / min, 150 mL / min or 200 mL / min, but not limited thereto. The flow rate of the pump affects the speed of the electrochemical reaction. If it is too fast, the reaction is insufficient, and if it is too slow, the actual production efficiency is affected. Therefore, a suitable flow rate should be selected in combination with the actual electrolytic cell volume and reaction rate.

[0073] According to some embodiments of the present invention, the DC voltage applied by the electrochemical reaction power supply 3 is 0.1 to 3 V, for example, 0.1 V, 1 V, 2 V or 3 V, but not limited thereto; the current density is 10 to 200 mA / cm 2 , for example, it can be 10mA / cm 2 , 50mA / cm 2 , 100mA / cm 2 , 150mA / cm 2 or 200mA / cm 2 , but it is not limited to this.

[0074] According to some embodiments of the present invention, the method further includes operation S303, performing solid-liquid separation by adding flocculants, filtration, centrifugal separation and the like, and obtaining a solid as a positive electrode material precursor; performing subsequent operations such as calcination and carbon coating on the positive electrode material precursor to finally obtain a regenerated positive electrode material.

[0075] According to some embodiments of the present invention, the calcination conditions vary according to different positive electrode materials. Nickel-cobalt-manganese ternary is calcined at 700-1200°C, for example, 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C, but not limited thereto. Lithium iron phosphate is calcined at 800-1000°C, for example, 800°C, 900°C or 1000°C, but not limited thereto. Lithium cobalt oxide is calcined at 700-1000°C, for example, 700°C, 800°C, 900°C or 1000°C, but not limited thereto. The calcination time is 3-24h, for example, 3h, 6h, 12h, 18h or 24h, but not limited thereto.

[0076] According to some embodiments of the present invention, a flow chart of a lithium recovery and retired positive electrode material repair system is also provided. Figure 4 As shown. With the electrochemical device of the present invention as the core, the left side is a roadmap for seawater desalination and lithium enrichment. A portion of the seawater / salt lake is concentrated after desalination to generate fresh water, and the other portion is concentrated brine. The brine is introduced into the anode chamber of the electrochemical device. When powered on, the lithium ions in the brine pass through the lithium ion selective exchange membrane and enter the cathode chamber. Chlorine is generated in the anode chamber. The generated chlorine can be used for fresh water disinfection, and the remaining other ion solutions can be used for other chemical applications or to prepare other compounds. The right side is a roadmap for the recovery and regeneration of the positive electrode of the battery. The retired battery that has been discharged is disassembled and pre-treated. After that, the positive electrode powder is obtained, and a solvent is added. A surfactant and a conductive agent are optionally added. The powder is stirred at a high speed and evenly dispersed to obtain a retired conductive slurry. The retired conductive slurry is pumped into the cathode chamber of the electrochemical device. When the power is turned on, the positive electrode material is reduced and regenerated by electrons. The regenerated positive electrode material flows out with the slurry. After solid-liquid separation, the liquid phase can be reused in the preparation of retired conductive slurry. The solid phase positive electrode material precursor is calcined to obtain a regenerated positive electrode material, which can be reused in the manufacture and use of batteries. During the calcination process, the binder or organic matter present in the product can also be burned. Among them, there are two routes for disassembly: mechanical disassembly or manual disassembly. The difference is that the positive electrode powder and the negative electrode powder can be distinguished by manual disassembly, while the positive and negative electrode powders after mechanical disassembly are mixed together, which has a certain impact on the subsequent configuration of the retired conductive slurry, but has little impact on the finished recycled material, because when the finished recycled material is calcined, graphite reacts with oxygen to generate carbon dioxide gas, which has little impact on the positive electrode material.

[0077] The present invention is further described below by embodiments and related test experiments and results. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined arbitrarily into other feasible embodiments.

[0078] It should be noted that the following specific examples are only for illustration, and the protection scope of the present invention is not limited thereto. The chemicals and raw materials used in the following examples are all commercially available or prepared by recognized preparation methods.

[0079] Example 1

[0080] This embodiment provides an electrochemical method for continuously regenerating positive electrode materials of lithium-ion batteries. Figure 1The electrolytic cell 1 using the electrochemical unit of the present invention, wherein the anode 21 and the cathode 22 are both electrodes composed of a graphite plate electrode and a mesh electrode 23, the thickness of the two graphite plate electrodes is 6 mm, and the effective reaction area of ​​the anode and the cathode is 200 cm 2 ; The mesh electrode 23 is a carbon felt electrode with 200 micron pores.

[0081] The electrolytic cell 1 is divided into an anode chamber 11 and a cathode chamber 12 by a lithium ion exchange membrane 13 (preferably a SPEEK composite membrane). The anode chamber 11 is connected to a gas pipeline 7; the anode chamber 11 and the cathode chamber 12 are both pumped with retired conductive slurry and brine from the slurry tank 5 and the brine tank 6 by a pump 3, and then discharged through a liquid pipeline 8.

[0082] The formula of retired conductive slurry is as follows: retired lithium iron phosphate powder 99g, carbon black conductive agent 1g, solvent water 898g, surfactant hydroxymethyl cellulose 2g, ensure that the solid content is about 10%, and stir and disperse evenly in the homogenization tank at a speed of 20r / min revolution and 1000r / min rotation.

[0083] The configuration of anode brine refers to the configuration of simulated brine of Xitaijinaier Salt Lake, and its main components are: Li + 1.42 g·L -1 , Na + 7.94 g·L -1 , K + 16.61 g·L -1 ,Mg 2+ 93.58g·L -1 , C l -1 260.39g·L -1 , SO4 2- 63.88g·L -1 .

[0084] The voltage applied by the electrochemical reaction power supply 3 is 2V, ensuring that the cathode electrode potential is lower than 3.4V vs. Li / Li + To ensure the normal occurrence of the cathode reaction, the current density was set to 50 mA / cm 2 .

[0085] The flow rate of the pump was set to 100 mL / min to ensure sufficient reaction.

[0086] After the reaction is completed, the regenerated positive electrode slurry is separated into solid and liquid by mechanical methods. The obtained solid is dried in a vacuum drying oven at 90°C, mechanically ground and calcined at 900°C to obtain the regenerated positive electrode material. The liquid is recovered and reused in the configuration of the retired conductive slurry.

[0087] The recycled positive electrode material powder, SP, and PVDF were mixed in a mass ratio of 8:1:1, and NMP was used as a solvent to manually mix to form a slurry. The slurry was evenly coated on aluminum foil, dried, and pressed into a positive electrode sheet. A lithium sheet was used as the counter electrode, the electrolyte was 1 mol / L Li PF6, and the lithium ion exchange membrane was selected from the Celgard series of polypropylene lithium ion exchange membranes. CR2025 button cells were assembled in a glove box. At room temperature, the NEWARE battery formation system was used, the voltage range was 2-3.65V, and the current density was 0.1C to test its gram capacity. The results are shown in Table 1. Compared with the new material, the first discharge gram capacity of the recycled material is slightly lower by 4.1mAh / g, and the first charge gram capacity is not much different from that of the new material after conversion, which proves that the material was successfully regenerated.

[0088] At the same time, the anode brine after the reaction was taken to test the lithium ion concentration, and the result was Li + 0.11 g L -1 , C l - 1 259.11 g·L -1 The reduction in lithium ion concentration demonstrated the successful extraction of lithium ions from the brine.

[0089] Research has shown that this method is also applicable to nickel-cobalt-manganese ternary (calcination temperature is 700-1200°C) and lithium cobalt oxide (calcination temperature is 700-1000°C), so it will not be repeated here.

[0090] Comparative Example 1

[0091] The present embodiment provides an electrochemical method capable of continuously regenerating positive electrode materials of lithium-ion batteries. Compared with Example 1, the difference is that the configuration of the retired conductive slurry is different. The specific formula is as follows: 100g of retired lithium iron phosphate powder, 898g of solvent water, 2g of surfactant hydroxymethyl cellulose, ensuring that the solid content is about 10%, and stirring and dispersing evenly in a slurry tank at a speed of 20r / min of revolution and 1000r / min of rotation.

[0092] The remaining devices and operations are consistent with those in Example 1.

[0093] The results are shown in Table 1. Compared with Comparative Example 2, the first discharge capacity of the recycled material is only slightly higher by 2.5 mAh / g, proving that sufficient cathode electrode reaction cannot be achieved by relying solely on the conductivity of the positive electrode material without adding a conductive agent.

[0094] Comparative Example 2

[0095] Retired lithium iron phosphate, SP, and PVDF were mixed in a mass ratio of 8:1:1 and assembled into a CR2025 button cell. Other operations and conditions were consistent with the embodiment. The capacity of the retired material at 0.33C for the first discharge was 105.8 mAh / g, compared with which the gram capacity of the recycled material was 22.8 mAh / g higher, proving that this invention can regenerate retired lithium iron phosphate positive electrode materials.

[0096] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0097] Table 1 Performance comparison of new materials and recycled materials

[0098]

[0099] In summary, (1) in the electrochemical device constructed by the present invention, the high-pore graphite felt and the conductive carbon fiber skeleton can provide a reaction site with a high specific surface area for the retired positive electrode material, and the formula of the retired conductive slurry also ensures the conductive network of the slurry; the lithium ion selective exchange membrane blocks the interference of other metal cations in the brine; the presence of the pump pumps the electrolytic reaction raw materials into the reaction chamber to increase the reaction rate, and the raw materials flow out from the output pipe after the reaction, which is convenient for continuous large-scale production; and the retired positive electrode material does not need to strictly control the initial lithium content.

[0100] (2) The present invention constructs a retired conductive slurry, which is prepared by selectively adding a surfactant and a conductive agent, stirring and uniformly dispersing. Since the slurry has fluidity, this reaction can be produced continuously. The liquid after subsequent solid-liquid separation can be used to repeatedly prepare retired conductive slurry, which has little pollution to the environment. The generated chlorine gas is discharged through the gas outlet pipe and collected for disinfection of fresh water.

[0101] (3) The electrochemical method used in the present invention promotes the reduction of retired positive electrode materials by applying an external power source, so as to regenerate the structure of retired positive electrode materials. Under the action of the external electric field, the lithium ions in the brine in the anode chamber migrate to the cathode chamber, and chlorine gas is generated at the same time. The repair of retired lithium-ion battery positive electrode materials is comprehensively realized, and the recovery and utilization of lithium resources in the brine are also realized, which has a good industrial application prospect.

[0102] (4) The electrochemical performance of the regenerated lithium battery positive electrode material prepared by the electrochemical method of the present invention is relatively stable and excellent, which is equivalent to the electrochemical performance of the lithium battery positive electrode material before retirement. At the same time, the lithium ion concentration in the brine is significantly reduced, which can realize the recovery and reuse of lithium resources. Among them, the retired lithium battery positive electrode materials include but are not limited to nickel-cobalt-manganese ternary, lithium iron phosphate, lithium cobalt oxide and other materials according to different systems.

[0103] 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. An electrochemical unit for continuous regeneration of retired positive electrode materials, characterized in that: The invention comprises an electrolytic cell, an anode chamber and a cathode chamber arranged in the electrolytic cell, and a lithium ion selective exchange membrane arranged between the anode chamber and the cathode chamber; the anode chamber is used to contain brine; and the cathode chamber is used to contain retired conductive slurry.

2. The electrochemical unit for continuous regeneration of retired positive electrode materials according to claim 1, characterized in that: The retired conductive slurry comprises retired positive electrode powder, a surfactant, a conductive agent and water; Preferably, the retired positive electrode powder is one of nickel-cobalt-manganese ternary, lithium iron phosphate, and lithium cobalt oxide; Preferably, the surfactant is hydroxymethyl cellulose, polypyrrolidone, polyethylene glycol octylphenyl ether, carboxymethyl cellulose CMC; preferably, the surfactant is hydroxymethyl cellulose; Preferably, the conductive agent is carbon nanotube, carbon black, SuperP, graphene, carbon fiber, etc.; preferably, the conductive agent is carbon black; Preferably, the mass ratio of retired positive electrode powder, surfactant, conductive agent and solvent is (19.8-198): (0.2-2): (0.4-4): (179.6-1796); preferably, the mass ratio is 99:1:2:

898.

3. The electrochemical unit for continuous regeneration of retired positive electrode materials according to claim 1, characterized in that: The retired conductive slurry is prepared in the following manner: S201, the retired batteries are crushed and screened to obtain retired positive electrode powder; preferably, mechanical disassembly or manual disassembly is performed; S202; surfactants and conductive agents are added and evenly dispersed until the slurry is uniform and has a certain conductivity, and the solid content of the retired conductive slurry is ≤25%; preferably 5-25%.

4. The electrochemical unit for continuous regeneration of retired positive electrode materials according to claim 1, characterized in that: An anode is arranged in the anode chamber; a cathode is arranged in the cathode chamber; the anode and the cathode are connected via a power supply; The anode and cathode independently include a current collector and a mesh electrode; the thickness of the current collector is independently 4 to 8 mm; the surface area is 100 to 400 cm 2 ; The current collector is an inert electrode, including at least one of platinum and graphite plate, and the structure includes a parallel plate or a straight flow field plate; The mesh electrode comprises conductive high-pore graphite felt or conductive carbon fiber skeleton; preferably, the mesh electrode has a pore size of 100 to 300 microns.

5. The electrochemical unit for continuous regeneration of retired positive electrode materials according to claim 1, characterized in that: The lithium ion exchange membrane is one of a lithium lanthanum titanate LLTO ceramic membrane, a SPEEK composite membrane, and a two-dimensional sub-nanometer hydrated layered silicate membrane.

6. An electrochemical device, characterized in that: Including parallel type or series type; The series type comprises a plurality of electrochemical units for continuous regeneration of retired positive electrode materials according to any one of claims 1 to 5 connected in series; the anode chamber of the first electrochemical unit is connected to the brine storage tank; the cathode chamber of the terminal electrochemical unit is connected to the slurry tank; a pump is provided on the connecting pipeline; The parallel type comprises a plurality of electrochemical units for continuous regeneration of retired positive electrode materials as described in any one of claims 1 to 5 connected in parallel; a brine storage tank and a slurry tank are respectively connected to the anode chamber and cathode chamber of each electrochemical unit; and a pump is provided on the connecting pipeline.

7. A method for continuous regeneration of retired positive electrode materials, characterized in that: Use of the electrochemical device according to claim 6.

8. The method according to claim 7, characterized in that The method comprises the following steps: S301, pumping brine into the anode chamber and pumping retired conductive slurry into the cathode chamber, wherein the anode and the cathode form an electrode pair; S302, applying voltage through a power supply to perform electrolysis, wherein a chloride ion oxidation reaction occurs at the anode to generate chlorine gas, and lithium ions in the brine in the anode chamber enter the cathode chamber through an ion exchange membrane under the action of an external electric field, and the oxidized positive electrode material in the retired conductive slurry in the cathode chamber undergoes a corresponding reduction reaction and lithium ion embedding, thereby repairing and regenerating the retired lithium ion battery positive electrode material; preferably, the DC voltage applied by the power supply is 0.1 to 3 V; the current density is 10 to 200 mA / cm 2 .

9. The method according to claim 8, characterized in that The method also includes S303, performing solid-liquid separation on the repaired and regenerated positive electrode material of the battery, and the obtained solid is the positive electrode material precursor; the positive electrode material precursor is calcined or carbon-coated to finally obtain the regenerated positive electrode material; preferably, nickel-cobalt-manganese ternary is calcined at 700-1200°C; lithium iron phosphate is calcined at 800-1000°C; lithium cobalt oxide is calcined at 700-1000°C; the calcination time is 3-24h.

10. A method for desalination of seawater, characterized in that: Use of the electrochemical device according to claim 6.

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