Method for recovering lithium resources in lithium ion battery cathode material

Abstract

The present application belongs to the technical field of material recycling, and relates to a method for recycling lithium resources in lithium ion battery positive electrode materials. The present application uses leaching medium with oxidizing property to oxidize the retired lithium ion battery positive electrode materials in a solid-liquid reaction system to extract lithium, and after the reaction, the leaching medium returns to the electrochemical reaction system to realize regeneration from the reduced state to the oxidized state, and is accompanied by deposition of metallic lithium. Subsequently, the leaching medium in the oxidized state returns to the solid-liquid reaction system to extract lithium from the positive electrode materials that have not been delithiated. A small amount of leaching medium is used to realize batch recycling of the retired lithium ion battery positive electrode materials, realize green closed-loop recycling, and reduce the recycling cost. Directly obtained is a metallic lithium foil, realizing high-value green controllable recycling of lithium resources.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material recycling, and relates to a lithium resource recycling method in a lithium ion battery positive electrode material. BACKGROUND

[0002] As a clean energy storage device, lithium ion batteries are widely used as chemical power sources for portable electronic devices and power sources for electric vehicles. With the vigorous development of new energy vehicles, the installed capacity of lithium ion power batteries is increasing year by year, and the gap between supply and demand of lithium resources is gradually expanding. In addition, it is reported that 1,100 tons of heavy metals and more than 200 tons of toxic electrolytes need to be treated for every 4,000 tons of waste lithium ion batteries. If not properly treated, it will cause irreversible pollution to the environment. In addition, the content of valuable metal elements in waste lithium ion batteries far exceeds that of general ores. In view of environmental protection and economic benefits, it is imperative to recycle and utilize waste lithium ion batteries.

[0003] At present, the lithium resources in the production and recycling of lithium ion battery positive electrode materials are commonly recycled by fire method and wet method. The traditional fire method can treat complex battery waste without strict sorting and pretreatment, but it has the problems of high energy consumption, low lithium resource recovery rate, heavy pollution and poor economy. Compared with the fire method, the wet metallurgical method has the advantages of high lithium resource recovery rate and no need for high-temperature sintering, and therefore is widely concerned by researchers. The traditional wet metallurgical method mainly realizes the recovery of lithium resources through acid leaching, but it will produce acid waste liquid which needs to be neutralized with alkali, and the consumption of acid and alkali is large, which will cause environmental pollution. In addition, the lithium salt product is obtained through subsequent treatment such as precipitation, evaporation recrystallization and neutralization treatment. At present, H2O2 and other oxidizing agents are also used to partially replace strong acid in the laboratory recycling of positive electrode materials, the leaching conditions are optimized, and the leaching rate and product purity of lithium are improved. CO2 is also used as a leaching agent to realize the recovery of lithium resources in the retired battery positive electrode material at room temperature,

[0004] Although the production and recycling of retired battery positive electrode materials can effectively realize the recovery of lithium resources and obtain lithium salt products such as lithium carbonate, the use of these technologies not only has the problems of complex process, complex subsequent treatment such as precipitation recovery and neutralization treatment. More importantly, the products obtained by these recycling methods are all lithium salt products, which have low added value, and the recycling process will cause environmental pollution. SUMMARY

[0005] To solve the above problems in the prior art, the purpose of the present application is to provide a lithium resource recycling method in a lithium ion battery positive electrode material to overcome the deficiencies of the prior art.

[0006] One purpose of the present application is achieved by the following technical solutions:

[0007] A method for recovering lithium resources in a lithium ion battery cathode material, comprising the following steps:

[0008] S1, injecting a leaching medium into a solid-liquid reactor filled with lithium ion battery cathode material, the leaching medium being in an oxidized state and reacting with the lithium ion battery cathode material in the solid-liquid reactor to reduce the lithium ion battery cathode material, the leaching medium being reduced and Li being removed from the lithium ion battery cathode material to form Li + , and then pumping the leaching solution into an electrochemical reactor, charging the electrochemical reactor at a certain current density, the reduced leaching medium being oxidized, and Li + being reduced to form Li single element deposition on the deposition carrier of the electrochemical reactor to form a primary Li deposition;

[0009] S2, circulating the leaching solution in the solid-liquid reactor and the electrochemical reactor by a pump to form multiple Li depositions, and keeping the lithium ion battery cathode material from flowing out of the solid-liquid reactor with the leaching solution;

[0010] S3, after the reaction is completed, the deposition carrier is taken out and washed to obtain a lithium metal foil;

[0011] The leaching solution is formed by dissolving the leaching medium in an electrolyte containing lithium salt, and the leaching medium is a compound that can form a redox couple.

[0012] Preferably, the leaching medium is any one or a combination of ferricyanide, acetylacetone metal salt, ferrocene and its derivatives, tetramethylpiperidine oxide and its derivatives, anthraquinone compounds, ketone compounds, alkylbenzene, and heterocyclic aromatic hydrocarbons.

[0013] Preferably, step S1 comprises the following steps:

[0014] Injecting the leaching solution into a solid-liquid reactor filled with lithium ion battery cathode material, when the leaching medium is in an oxidized state, the oxidized leaching medium reacts with the lithium ion battery cathode material to reduce the lithium ion battery cathode material, the leaching medium is reduced, and then the leaching solution is pumped into an electrochemical reactor, the electrochemical reactor is charged at a certain current density, the leaching medium is oxidized, and Li + is reduced to form Li single element deposition to form a primary Li deposition;

[0015] When the leaching medium is in the reduced state, the reduced leaching medium does not react with the lithium-ion battery cathode material, and then the leaching solution is pumped into an electrochemical reactor, the electrochemical reactor is charged at a certain current density, and the leaching medium is oxidized; the oxidized leaching medium is pumped into a solid-liquid reactor, and a reduction reaction occurs between the oxidized leaching medium and the lithium-ion battery cathode material, the leaching medium is reduced, the leaching solution is pumped into the electrochemical reactor, and the electrochemical reactor is charged at a current density, the leaching medium is oxidized, Li + is reduced to form Li single-element deposition to form primary Li deposition.

[0016] Preferably, the electrolyte containing lithium is formed by dissolving lithium salt in an organic solvent, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis-trifluoromethanesulfonimide, lithium bis-fluorosulfonimide; the organic solvent is one or more of dimethyl carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, vinylene carbonate; the concentration of lithium salt is 0.01-2 mol / L.

[0017] Preferably, the lithium-ion battery cathode material is one or more of nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, lithium cobaltate, lithium iron phosphate, lithium manganate, lithium titanate.

[0018] Preferably, the circulation flow rate of the leaching solution is 10-1000 ml / min.

[0019] Preferably, the electrochemical reactor is charged at a current density of 0.1-100 mA / cm2, and the electrochemical reactor is charged to 3.0-5.0 V.

[0020] Preferably, the solid-liquid reactor has a containing cavity, and the containing cavity is divided into an upper feeding cavity and a lower discharging cavity by a filtering assembly, and the feeding cavity is provided with a first feeding port, and the discharging cavity is provided with a first discharging port.

[0021] The electrochemical reactor comprises a first current collector and a second current collector as positive and negative electrodes, and the first current collector and the second current collector are connected to the positive and negative electrodes of an external power supply, wherein the first current collector and the second current collector are oppositely arranged; a graphite plate is located between the first current collector and the second current collector and connected to the first current collector; a deposition carrier is detachably connected to the second current collector and oppositely arranged with the graphite plate; and a diaphragm is located between the graphite plate and the second current collector.

[0022] The graphite plate is provided with a flow channel, and the flow channel is provided with a second feeding port and a second discharging port, the second feeding port is connected to the first discharging port through a first pipeline, the second discharging port is connected to the first feeding port through a second pipeline, and a pump body is arranged on the first pipeline or the second pipeline.

[0023] Preferably, the solid-liquid reactor is sequentially provided with a cover plate, a barrel and a base along a feeding direction, and the cover plate and the barrel are connected through fasteners, and the barrel and the base are connected through fasteners, wherein the feeding cavity is arranged in the barrel, the discharging cavity is arranged in the base, the first feeding port is arranged on the cover plate and communicates with the feeding cavity, the first discharging port is arranged on the base and communicates with the discharging cavity, and the filtering assembly is located at the connection between the barrel and the base.

[0024] The cover plate is also provided with a stirrer, and the stirring end of the stirrer extends into the feeding cavity through the cover plate, wherein the stirring end is provided with a stirring rod.

[0025] The cover plate is provided with a gas outlet, and the gas outlet communicates with the feeding cavity.

[0026] Preferably, the electrochemical reactor further comprises a first insulating gasket, a second insulating gasket, a first clamping plate and a second clamping plate, and the first insulating gasket is located between the first clamping plate and the first current collector, and the second insulating gasket is located between the second clamping plate and the second current collector.

[0027] The electrochemical reactor further comprises a first sealing gasket and a second sealing gasket, and the graphite felt is placed in the hole of the first sealing gasket, the deposition carrier is located in the hole of the second sealing gasket, the diaphragm is clamped between the first sealing gasket and the second sealing gasket, and the structure formed by splicing the first sealing gasket, the graphite felt, the diaphragm and the second sealing gasket is connected to one side of the graphite plate provided with the flow channel.

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

[0029] 1. The present application is based on a continuous flow electrochemical solid-liquid coupling reaction technology, and provides a method for recycling lithium resources of lithium ion battery positive materials on a large scale. First, the continuous flow electrochemical reactor is used as an electrochemical reaction system, and a solid-liquid reaction system is combined to realize selective lithium extraction and recovery of retired lithium ion battery positive materials. An oxidizing lithium extraction leaching medium is used as a leaching agent to oxidize and extract lithium from the retired lithium ion battery positive materials in the solid-liquid reaction system. After the reaction, the lithium extraction leaching medium returns to the electrochemical reaction system, realizes the regeneration of the lithium extraction leaching medium from the reduced state to the oxidized state, and is accompanied by the deposition of lithium metal on the deposition carrier. Subsequently, the lithium extraction leaching medium in the oxidized state returns to the solid-liquid reaction system to extract lithium from the positive materials that have not been delithiated, so that the reaction solution always maintains a constant lithium extraction leaching medium and Li + Concentration. A small amount of lithium extraction leaching medium is used to realize batch recovery of retired lithium ion battery positive materials. This technology can realize the recovery of a large amount of waste positive materials with a small amount of recyclable leaching agent, realize green closed-loop recycling, reduce recovery cost, solve the problems of reducing the energy barrier of the surface interface reaction and uncontrollable lithium extraction rate during the lithium extraction process, and simultaneously realize the recycling of lithium resources.+ Migrate and deposit in situ on the deposition carrier, directly get metal lithium foil, realize the high value green controllable recovery of lithium resources.

[0030] 2、The new method for recycling lithium resources of positive electrode materials on a large scale can flexibly adjust and schedule the thickness, porosity and microstructure of the recovered product metal lithium foil at any time according to production needs, so as to achieve the purpose of recycling and preparing high-performance metal lithium foil materials.

[0031] 3、The lithium resources of the application can achieve the purpose of industrial-scale recovery, can adjust product types in time according to market demand changes, have high production line flexibility, wide adaptability, low production cost and simple process.

[0032] 4、The application develops a closed cycle process for recycling lithium metal in situ deposition of positive electrode materials of retired lithium ion batteries through the circulating recovery device formed by the solid-liquid reactor, the electrochemical reactor and the pipeline, directly generates high-value-added metal lithium foil, saves the complex subsequent treatment such as precipitation and evaporation crystallization in the traditional wet recovery, and improves the production yield. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a structural diagram of the solid-liquid reactor and the electrochemical reactor connected in the application;

[0034] Figure 2 It is a structural diagram of the solid-liquid reactor in a preferred embodiment of the application;

[0035] Figure 3 It is an exploded view of the electrochemical reactor in a preferred embodiment of the application;

[0036] Figure 4 It is a flow chart of recycling lithium resources in the positive electrode material of the lithium ion battery;

[0037] Figure 5 It is a charge-discharge curve of real-time detection of the electrochemical reactor in Example 1;

[0038] Figure 6 It is a physical map (a) and a scanning electron microscope map (b) of the metal lithium foil of Example 1;

[0039] Figure 7 It is a comparison diagram of electrochemical performance of the metal lithium foil prepared in Example 1 and the commercial lithium foil;

[0040] Figure 8 It is a charge-discharge curve of the metal lithium foil prepared in Example 1 and the commercial lithium foil.

[0041] In the figure,

[0042] 10. Solid-liquid reactor; 11. Filter assembly; 12. Feed chamber; 13. Discharge chamber; 14. Cover plate; 141. First feed inlet; 142. Air outlet; 15. Cylinder; 151. First flange; 16. Base; 161. First discharge outlet; 162. Second flange; 17. Agitator; 171. Agitator rod;

[0043] 20. Electrochemical reactor; 21. First current collector; 23. Graphite plate; 231. Flow channel; 232. Second feed inlet; 233. Second discharge outlet; 24. Second current collector; 25. Deposition carrier; 26. Diaphragm; 27. First insulating gasket; 28. Second insulating gasket; 29. ​​First clamping plate; 210. Second clamping plate; 220. First sealing gasket; 230. Second sealing gasket; 240. Graphite felt; 30. First pipeline; 40. Second pipeline; 50. Pump body. Detailed Implementation

[0044] In the following description, embodiments of the method for recovering lithium resources from the lithium-ion battery cathode material of the present invention will be described in detail. However, these embodiments are exemplary, and the disclosure of the present invention is not limited thereto. Furthermore, the accompanying drawings used herein are merely for better illustration of the disclosed content of the present invention and do not constitute a limitation on the scope of protection.

[0045] This invention provides a method for recovering lithium resources from lithium-ion battery cathode materials in some embodiments, such as... Figure 4 As shown, it includes the following steps:

[0046] S1. The leaching medium is dissolved in a lithium salt-containing electrolyte to form a leaching solution, wherein the leaching medium is a compound that can form a redox couple;

[0047] S2. Fill the solid-liquid reactor with lithium-ion battery cathode material;

[0048] S3. The leachate is injected into the solid-liquid reactor. When the leachate is in an oxidized state, it undergoes a reduction reaction with the lithium-ion battery cathode material in the solid-liquid reactor. The leaching-mediated reduction removes Li elements from the lithium-ion battery cathode material, forming Li. + The leachate was then pumped into the electrochemical reactor, which was charged at a certain current density. The reduced leachate was then mediated by oxidation of Li... + The reduced elemental Li is deposited on the deposition support of the electrochemical reactor, forming a primary Li deposition.

[0049] S4. The leachate is circulated in the solid-liquid reactor and the electrochemical reactor by a pump to form multiple Li deposits and keep the lithium-ion battery cathode material from flowing out of the solid-liquid reactor with the leachate.

[0050] S5. After the reaction is complete, remove the deposition support and wash it to obtain lithium metal foil.

[0051] The leaching is mediated by compounds capable of forming redox couples. These compounds exhibit reversible redox behavior, forming different compounds upon gaining or losing electrons, and this process is reversible.

[0052] Redox couple: In a redox reaction, the oxidized and reduced states that appear on opposite sides of a half-reaction are called a redox couple. A half-reaction in a redox reaction refers to a way of representing the entire reaction by dividing it into two parts, each describing the oxidation or reduction process of only one substance.

[0053] For example, the half-reaction of a redox reaction is as follows: [Fe(CN)6] 3+ → [Fe(CN)6] 4+ +e - Then [Fe(CN)6] 3+ / [Fe(CN)6] 4+ This is a redox couple. At this point, the compound that can form the redox couple, i.e., the leaching mediator, can be [Fe(CN)6]. 3+ The compound (leaching-mediated by oxidation state) can also be Fe(CN)6. 4+ Compounds (reduced state leaching mediated).

[0054] Preferably, the leaching medium is any one or more combinations of metal-containing redox compounds and organic redox compounds. More preferably, the leaching medium is any one or more combinations of ferrocyanides, acetylacetone metal salts, ferrocene and its derivatives, tetramethylpiperidine oxide (TEMPO) and its derivatives, anthraquinone compounds, ketone compounds, alkylbenzenes, and heterocyclic aromatic hydrocarbons. Ferricyanides may include one or more of potassium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide, ammonium ferrocyanide, magnesium ferrocyanide, sodium ferrocyanide, ammonium ferrocyanide, and magnesium ferrocyanide. Acetylacetone metal salts may include one or more of iron acetylacetone, cobalt acetylacetone, and chromium acetylacetone.

[0055] When the leaching medium used is in its oxidized state, it accepts electrons through self-reduction in the solid-liquid reactor and undergoes a reduction reaction with the lithium-ion battery cathode material. The reduction half-reaction is: Leaching medium (oxidized state) + ne - → Leaching-mediated (reduced state); The reduced state enters the electrochemical reactor through leaching, releases electrons through self-oxidation, and undergoes an oxidation reaction. The oxidation half-reaction is: Leaching-mediated (reduced state) → Leaching-mediated (oxidized state) + ne - .

[0056] When the leaching mediator is in a reduced state, it does not react in the solid-liquid reactor, and then the reduced leaching mediator is pumped into the electrochemical reactor to form an oxidized state leaching mediator by oxidation reaction, and the oxidized leaching mediator returns to the solid-liquid reactor to react with the lithium ion battery positive electrode material to form a reduced state leaching mediator.

[0057] The leaching mediator forms a closed loop in the solid-liquid reactor and the electrochemical reactor, and is not consumed itself, but only serves as an electron carrier to improve or realize the transfer efficiency of lithium elements.

[0058] The method for recycling lithium resources in a lithium ion battery positive electrode material provided in some embodiments of the application comprises the following steps:

[0059] S1, dissolving the leaching mediator in the electrolyte containing lithium salt to form a leaching solution, wherein the leaching mediator is a compound capable of forming a redox couple;

[0060] S2, filling the lithium ion battery positive electrode material in the solid-liquid reactor;

[0061] S3, injecting the leaching solution into the solid-liquid reactor, when the leaching mediator is in an oxidized state, the oxidized leaching mediator reacts with the lithium ion battery positive electrode material to form a reduced state leaching mediator, and then the leaching solution is pumped into the electrochemical reactor, and the electrochemical reactor is charged at a certain current density, the leaching mediator is oxidized, Li + is reduced to form Li single element deposition to form primary Li deposition;

[0062] When the leaching mediator is in a reduced state, the reduced leaching mediator does not react with the lithium ion battery positive electrode material, and then the leaching solution is pumped into the electrochemical reactor, and the electrochemical reactor is charged at a certain current density, the leaching mediator is oxidized; the oxidized leaching mediator is pumped into the solid-liquid reactor to react with the lithium ion battery positive electrode material to form a reduced state leaching mediator, and then the leaching solution is pumped into the electrochemical reactor by a pump, and the electrochemical reactor is charged at a certain current density, the leaching mediator is oxidized, Li + is reduced to form Li single element deposition to form primary Li deposition;

[0063] S4, circulating the leaching solution in the solid-liquid reactor and the electrochemical reactor by a pump to form multiple Li depositions, and keeping the lithium ion battery positive electrode material from flowing out of the solid-liquid reactor with the leaching solution;

[0064] S5, after the reaction is completed, the deposition carrier in which metal lithium is deposited in the electrochemical reactor is taken out, and metal lithium foil can be obtained after washing.

[0065] The electrolyte containing lithium salt is formed by dissolving lithium salt in an organic solvent, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis-trifluoromethanesulfonimide, lithium bisfluorosulfonimide (LiFSI), and the organic solvent is one or more of dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), methyl trifluoroethyl carbonate (FEMC), ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, vinylene carbonate. The concentration of lithium salt is 0.01-2 mol / L.

[0066] Preferably, the lithium ion battery positive electrode material is one or more of nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, lithium cobaltate, lithium iron phosphate, lithium manganate, lithium titanate.

[0067] The molar ratio of the lithium ion battery positive electrode material to the leaching medium is not particularly limited, and theoretically, a small amount of leaching medium can be used to recover a large amount of Li in the lithium ion positive electrode material through multiple cycles. Preferably, the molar ratio of the lithium ion battery positive electrode material to the leaching medium is ≥1. Preferably, it is 1:1-100. Further preferably, it is 1:1-50.

[0068] Preferably, the circulation flow rate of the leaching solution is 10-1000 ml / min.

[0069] Preferably, the electrochemical reactor is charged at a current density of 0.1-100 mA / cm2 to 3.0-5.0 V. The electrochemical reactor is charged at a certain current density to regenerate the leaching medium back to the oxidized state, thereby realizing the regeneration of the leaching solution, while the lithium ions are deposited in the electrode chamber to obtain a lithium metal foil, thereby realizing the recovery of lithium resources.

[0070] In some embodiments of the present application, a device for recovering lithium resources in a lithium ion battery positive electrode material is also provided, comprising a solid-liquid reactor 10 and an electrochemical reactor 20.

[0071] As shown in Figures 1-3 The solid-liquid reactor 10 is internally provided with a containing cavity, which is divided into an upper feeding cavity 12 and a lower discharging cavity 13 in communication by a filtering assembly 11, and the feeding cavity 12 is provided with a first feeding port 141, and the discharging cavity 13 is provided with a first discharging port 161.

[0072] The electrochemical reactor 20 comprises a first current collector 21 and a second current collector 24 as positive and negative electrodes, and the first current collector 21 and the second current collector 24 are connected to the positive and negative electrodes of an external power supply, wherein the first current collector 21 and the second current collector 24 are oppositely arranged; a graphite plate 23 is located between the first current collector 21 and the second current collector 24 and connected to the first current collector 21, wherein the graphite plate 23 is provided with a flow channel 231, and a second feeding port 232 and a second discharging port 233 are arranged on the flow channel 231, the second feeding port 232 is connected to the first discharging port 161 through a first pipeline 30, the second discharging port 233 is connected to the first feeding port 141 through a second pipeline 40, and a pump body 50 is arranged on the first pipeline 30 or the second pipeline 40; a deposition carrier 25 made of conductive material is detachably connected to the second current collector 24 and oppositely arranged with the graphite plate 23; and a diaphragm 26 is located between the graphite plate 23 and the second current collector 24.

[0073] The lithium ion battery positive electrode material is filled into the feeding cavity 12 of the solid-liquid reactor, and the filter assembly 11 is arranged between the feeding cavity 12 and the discharging cavity 13, so that the lithium ion battery positive electrode material in the feeding cavity 12 cannot directly enter the discharging cavity 13, then the leaching liquid is injected into the feeding cavity 12 to fully mix with the lithium ion battery positive electrode material, the leaching medium in the oxidation state reacts with the lithium ion battery positive electrode material to form the target leaching liquid, and then the target leaching liquid flows out from the first discharging port 161 into the electrochemical reactor 20 through the first pipeline 30 under the action of the pump, and metal lithium and the leaching liquid with the leaching medium in the oxidation state are generated through electrolysis reaction, wherein the metal lithium is adsorbed on the deposition carrier 25 to precipitate, and thus the first lithium element is precipitated. The leaching liquid with the leaching medium in the oxidation state flows out from the second discharging port 233 into the feeding cavity 12 through the second pipeline 40 again to react with the remaining lithium ion battery positive electrode material to form the target leaching liquid again, and the above steps are repeated to precipitate the second lithium element. The lithium element in the lithium ion battery positive electrode material is precipitated through the above steps. Since the leaching medium in the target leaching liquid flows from the solid-liquid reactor 10 to the electrochemical reactor 20 and then returns to the solid-liquid reactor 10, a small amount of lithium extraction leaching medium is used to realize batch recovery of the lithium ion battery positive electrode material, a green closed cycle is realized, problems such as reduction of surface interface reaction capacity and uncontrollable lithium extraction rate during the lithium extraction process are solved, the metal lithium is precipitated on the deposition carrier 25 to obtain a metal lithium foil, and high-value green and controllable recovery of lithium resources is realized.

[0074] In addition, it is further pointed out that when the leaching mediator is in a reduced state, the leaching mediator is injected into the feeding chamber 12 without reacting with the lithium ion battery cathode material in the feeding chamber 12, and then the leaching solution is pumped into the electrochemical reactor 20, and through electrochemical reaction, the reduced leaching mediator is oxidized to form an oxidized leaching mediator, at this time, the leaching solution is returned to the feeding chamber 12 again, and can react with the lithium ion battery cathode material in the feeding chamber 12 to produce lithium ions and target leaching solution with reduced leaching mediator, and then the lithium metal and leaching solution with oxidized leaching mediator are produced again through the electrochemical reactor.

[0075] Preferably, the solid-liquid reactor 10 is sequentially provided with a cover plate 14, a barrel 15 and a base 16 in the feeding direction, and the cover plate 14 and the barrel 15 are connected by fasteners, and the barrel 15 and the base 16 are connected by fasteners, wherein the feeding chamber 12 is arranged in the barrel 15, the discharging chamber 13 is arranged in the base 16, the first feeding port 141 is arranged on the cover plate 14 and communicates with the feeding chamber 12, the first discharging port 161 is arranged on the base 16 and communicates with the discharging chamber 13, and the filter assembly 11 is located at the connection between the barrel 15 and the base 16.

[0076] In this embodiment, the detachable connection between the cover plate 14 and the barrel 15 facilitates the feeding of the lithium ion battery cathode material, that is, when it is necessary to fill the lithium ion battery cathode material into the feeding chamber 12, the cover plate 14 is directly opened, and when the filling is completed, the connection between the cover plate 14 and the barrel 15 is locked by the fasteners. The feeding port on the cover plate 14 is used as the injection port of the leaching solution, that is, after the leaching mediator is mixed with the electrolyte in a certain proportion, it can be directly injected from the feeding port. The advantage of this is that when the leaching solution is injected into the feeding chamber 12, it is mixed with the existing lithium ion battery cathode material in the feeding chamber 12, so that even if the phenomenon of "powder flying" occurs, it will not overflow the barrel 15, ensuring the environment around the solid-liquid reactor 10. In addition, the connection between the barrel 15 and the base 16 generally does not need to be frequently disassembled, and only when the filtering effect of the filter assembly 11 needs to be replaced, the connection between the barrel 15 and the base 16 needs to be disassembled. Therefore, the detachable structure of the barrel 15 and the base 16 also facilitates the replacement of the filter assembly 11, ensuring that the filter assembly 11 in the solid-liquid reactor 10 always has a good filtering effect.

[0077] The filter assembly 11 is a filter membrane or a filter screen, or a combination of the two, etc. The pore size of the filter assembly is < the particle size of the raw material.

[0078] It is worth mentioning that the whole solid-liquid reactor 10 is arranged in a detachable structure, which not only facilitates the filling of the lithium ion battery positive material and the extraction of the residue after the reaction, but also realizes the large-scale recovery of lithium resources and improves the recovery efficiency.

[0079] It is further pointed out that the cover plate 14 and the cylinder body 15 constitute the upper part structure of the solid-liquid reactor 10, and the base 16 constitutes the lower part structure of the solid-liquid reactor 10, wherein the upper part structure is made of transparent material, such as glass. The upper part structure of the solid-liquid reactor 10 is arranged in a transparent manner, which facilitates the observation of the mixing condition between the lithium ion battery positive material and the leaching liquid, avoids the waste of raw materials caused by insufficient mixing of the two, and reduces the recovery efficiency of lithium resources.

[0080] Preferably, the cover plate 14 is further provided with a stirrer 17, and the stirring end of the stirrer 17 extends into the feeding chamber 12 through the cover plate 14, wherein the stirring end is provided with a stirring rod 171.

[0081] In this embodiment, the setting of the stirrer 17 can satisfy the sufficient contact between the leaching medium in the leaching liquid and the lithium ion battery positive material, so as to improve the extraction effect of lithium resources.

[0082] It is worth mentioning that the stirrer 17 generally drives the stirring rod 171 to rotate circumferentially through a motor, and the motor can be a stepping motor, which is convenient for controlling the rotating speed and rotating angle.

[0083] Further preferably, the cover plate 14 is provided with a gas outlet 142, and the gas outlet 142 is in communication with the feeding chamber 12.

[0084] In this embodiment, by setting the gas inlet, the pressure in the feeding chamber 12 is adjusted, so as to change the filtering speed and the filtering quality, and avoid the cracking phenomenon caused by the too high pressure in the feeding chamber 12.

[0085] Preferably, the two ends of the cylinder body 15 along the feeding direction are respectively provided with first flanges 151, and the plane where the outlet chamber 13 of the base 16 is arranged is provided with a second flange 162, wherein the cover plate 14 is connected with the first flange 151 on the side of the cylinder body 15 facing the cover plate 14 through fasteners, and the first flange 151 on the side of the cylinder body 15 facing the base 16 is connected with the second flange 162 through fasteners.

[0086] In this embodiment, by setting the first flange 151 and the second flange 162, the splicing gap between the cover plate 14 and the cylinder body 15 and between the cylinder body 15 and the base 16 is reduced, so as to avoid the leakage phenomenon.

[0087] Further preferably, a sealing member is arranged between the cover plate 14 and the cylinder 15, and between the cylinder 15 and the base 16, and is embedded in any two of the first flange 151, the second flange 162, or the cover plate 14.

[0088] Preferably, the electrochemical reactor 20 further comprises a first insulating gasket 27, a second insulating gasket 28, a first clamp plate 29, and a second clamp plate 210, and the first insulating gasket 27 is arranged between the first clamp plate 29 and the first current collector 21, and the second insulating gasket 28 is arranged between the second clamp plate 210 and the second current collector 24.

[0089] In the embodiment, the first insulating gasket 27 and the second insulating gasket 28 are mainly used to insulate the conduction between the first clamp plate 29 and the first current collector 21, and between the second clamp plate 210 and the second current collector 24.

[0090] Preferably, the electrochemical reactor 20 further comprises a first sealing gasket 220 and a second sealing gasket 230, and the graphite felt 240 is arranged in the hole of the first sealing gasket 220, the deposition carrier 25 is arranged in the hole of the second sealing gasket 230, and the diaphragm 26 is clamped between the first sealing gasket 220 and the second sealing gasket 230. The structure formed by the first sealing gasket 220, the graphite felt 240, the diaphragm 26, and the second sealing gasket 230 is connected to one side of the graphite plate 23 provided with the flow channel 231.

[0091] In the embodiment, the graphite felt 240 is used to expand the reaction site area and improve the efficiency of the leaching medium oxidation, and the first sealing gasket 220 and the second sealing gasket 230 are used to improve the sealing effect.

[0092] Further preferably, the flow channel 231 is arranged in an S shape, the second inlet 232 is arranged at the lower end of the flow channel 231, and the second outlet 233 is arranged at the upper end of the flow channel 231. The device for recycling lithium resources in a lithium ion battery positive electrode material provided by the application realizes the recycling of lithium resources through the solid-liquid reactor 10, the electrochemical reactor 20, and the pipeline, and the process is simple and does not cause environmental pollution.

[0093] The technical solutions of the application will be further described and illustrated by specific embodiments and drawings. It should be understood that the specific embodiments described herein are only used to help understand the application and are not used to limit the application. The drawings used herein are only used to better illustrate the disclosed content and do not limit the protection scope. If not otherwise specified, the raw materials used in the embodiments of the application are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0094] In the description of the present application, unless otherwise specified, the numerical range "a~b" represents a shorthand notation for any real combination between a and b, and includes a and b.

[0095] Example 1

[0096] The recovery method of the present embodiment comprises the following steps:

[0097] S1, 0.05 mol K4[Fe(CN)6] is immersed and dissolved in 1000 mL of lithium salt-containing electrolyte (1 M LiTFSI dissolved in DMC:EC mixed solvent with a volume ratio of 7:3) to form a leaching solution.

[0098] S2, 0.5 mol of lithium ion battery cathode material LiFePO4 is filled into the feed chamber of the solid-liquid reactor, and the assembly of the solid-liquid reactor is completed.

[0099] S3, the leaching solution is injected into the feed chamber of the solid-liquid reactor through the first feed port, K4[Fe(CN)6] does not react with LiFePO4, then the leaching solution is pumped out from the first discharge port and enters the second feed port of the electrochemical reactor through the first pipeline (and the LiFePO4 cathode material is prevented from flowing out of the solid-liquid reactor with the leaching solution by the filter assembly (filter screen)), the electrochemical reactor is charged at a current density of 1.0 milliampere / square centimeter, and the cutoff voltage is 4.0V, in the process, the leaching-mediated K4[Fe(CN)6] is oxidized to K3[Fe(CN)6]; Li + in the leaching solution is reduced to form Li elemental deposition on the deposition carrier (copper foil), forming a primary Li deposition; K3[Fe(CN)6] is pumped out from the second discharge port and enters the solid-liquid reactor from the first feed port through the second pipeline, at this time, K3[Fe(CN)6] reacts with LiFePO4 and is reduced to [Fe(CN)6] 4- in the leaching-mediated, Li + in the cathode material is released, then the leaching solution is pumped out from the first discharge port and enters the second feed port of the electrochemical reactor through the first pipeline, the electrochemical reactor is charged at a current density of 1.0 milliampere / square centimeter, and the cutoff voltage is 4.0V, in the process, the leaching-mediated [Fe(CN)6] 4- is oxidized to K3[Fe(CN)6], Li + is reduced to form Li elemental deposition on the deposition carrier, forming a secondary Li deposition.

[0100] S4, repeat the cycle to form multiple Li depositions; the circulation flow rate of the leaching solution is 50 ml / min.

[0101] S5. After the reaction is complete, remove the deposition support containing lithium metal from the electrochemical reactor and wash it to obtain lithium metal foil.

[0102] The following reaction occurred in the first electrochemical reactor: [Fe(CN)6] 4- +Li + →[Fe(CN)6] 3- +Li

[0103] The following reaction then occurs in the solid-liquid reactor: [Fe(CN)6] 3- +LiFePO4→ [Fe(CN)6] 4- +Li + +FePO4;

[0104] The following reaction then occurs in the electrochemical reactor: [Fe(CN)6] 4- +Li + →[Fe(CN)6] 3- +Li.

[0105] The completion of the reaction is determined by real-time monitoring of the charge-discharge curves in the electrochemical reactor. Figure 5 As shown, the green curve is the real-time monitoring curve of the electrochemical reactor in Example 1. As the recovery progresses, the electrochemical reactor undergoes a charging step, and the voltage gradually increases with the increase in charging capacity (charging time) until it reaches the cutoff voltage, indicating that Li... + Recovery complete. The blue curve represents the control sample (without LiFePO4 material added to the solid-liquid reactor).

[0106] Figure 6 The images shown are (a) and (b) of the lithium foil from Example 1. The obtained lithium foil has a macroscopic size of 5 × 5 cm. The prepared lithium metal has a tightly packed, rock-like structure, providing good nucleation sites while avoiding the exposure of a large amount of active surface area, and has a thickness of 40 micrometers.

[0107] The recycled lithium foil prepared in Example 1 and a commercial lithium foil of the same thickness were assembled into batteries with commercial LiFePO4 cathode material, respectively. Electrochemical performance was compared, and the performance comparison chart is shown below. Figure 7 The corresponding charge-discharge curves are as follows: Figure 8 Recycled Li refers to the lithium foil prepared in Example 1, while Commercial Li refers to commercially available lithium foil of the same thickness.

[0108] The fresh LiFePO4, Super P and PVDF were mixed in a mass ratio of 8:1:1, and NMP was used as the solvent to rotate and mix into slurry in a high-speed mixer. Then the slurry was uniformly coated on the aluminum foil by using an automatic film coating machine, and dried at 80°C for 12 hours. The dried electrode was cut into a 14 mm round piece, and the electrode was weighed and the load of the electrode was about 2.4 mg / cm 2 . The electrode was assembled in a 2032 type button cell, and the whole assembly process was carried out in a glove box under argon atmosphere (O2 and H2O <0.1 ppm). The electrolyte used 1 M LiTFSI dissolved in DOL / DME (volume ratio 1:1). The recovered metal lithium foil or the same thickness of commercial lithium foil was used as the negative electrode, respectively. The charge / discharge test of the assembled button cell was carried out on the LAND battery test system. The commercial metal lithium foil assembled battery had a first circle charge capacity of 162.74 mAh / g, a discharge capacity of 153.74 mAh / g, a 200 circle retention rate of 87.06%, and an average coulombic efficiency of 99.76% at a current density of 0.1C. In comparison, the recovered metal lithium foil assembled battery had a first circle charge capacity of 165.47 mAh / g, a discharge capacity of 156.82 mAh / g, a 200 circle retention rate of 98.38%, and an average coulombic efficiency of 99.36% at a current density of 0.1C. The recovered metal lithium foil had a better capacity retention rate.

[0109] The Li recovery rate in the waste LiFePO4 of the embodiment was as high as 98.33%.

[0110] Example 2

[0111] The recovery method of the embodiment comprises the following steps:

[0112] S1, 0.05 mol of K3[Fe(CN)6] was immersed and dissolved in 1000 mL of lithium salt-containing electrolyte (1 M LiTFSI dissolved in DMC:EC mixed solvent with a volume ratio of 7:3 to form a leaching solution.

[0113] S2, 0.2 mol of lithium ion battery cathode material LiFePO4 was filled into the feed cavity of the solid-liquid reactor, and the assembly of the solid-liquid reactor was completed.

[0114] S3, the leaching solution was injected into the feed cavity of the solid-liquid reactor through the first feed port, and K3[Fe(CN)6] reacted with LiFePO4 to reduce the leaching agent to [Fe(CN)6] 4- , and the Li +The leaching solution is pumped out from the first outlet and into the second inlet of the electrochemical reactor through the first pipeline, the LiFePO4 positive electrode material is retained in the solid-liquid reactor by the filter assembly (filter screen) and does not flow out with the leaching solution, the electrochemical reactor is charged at a current density of 0.5 mA / cm2 and a cutoff voltage of 4.0 V, in the process, the leaching agent [Fe(CN)6] 4- is oxidized to [Fe(CN)6] 3- , Li + is reduced to form Li elemental deposition on the deposition carrier (copper foil) to form a primary Li deposition.

[0115] S4, K3[Fe(CN)6] is pumped out from the second outlet and into the first inlet of the solid-liquid reactor through the second pipeline, K3[Fe(CN)6] is again reduced with LiFePO4 and is again pumped into the electrochemical reactor. This cycle is repeated to form multiple Li depositions. The circulation flow rate of the leaching solution is 30 ml / min.

[0116] S5, after the reaction is completed, the deposition carrier with deposited metal lithium in the electrochemical reactor is taken out and washed to obtain a metal lithium foil.

[0117] The following reaction occurs in the solid-liquid reactor:

[0118] [Fe(CN)6] 3- + LiFePO4→ [Fe(CN)6] 4- + Li + + FePO4;

[0119] The following reaction occurs in the electrochemical reactor: [Fe(CN)6] 4- + Li + → [Fe(CN)6] 3- + Li.

[0120] Example 3

[0121] Example 3 differs from Example 1 in that the leaching agent of Example 3 is 2,2,6,6-tetramethylpiperidine oxide derivative (TMAPO), the electrolyte is 1 M LiFSI dissolved in DMC, FEC, FEMC to form a mixed solvent in a volume ratio of 2:4:4, and the others are the same as in Example 1.

[0122] The following reaction occurs in the solid-liquid reactor:

[0123] TMAPO + + LiFePO4→ TMAPO + Li + + FePO4;

[0124] The following reaction occurs in the electrochemical reactor: TMAPO + Li + → TMAPO + + Li.

[0125] Example 4

[0126] Example 4 differs from Example 1 in that the leaching mediator of Example 4 is 2,2,6,6-tetramethylpiperidine oxide (TEMPO), the electrolyte is 1 M LiFSI dissolved in a mixed solvent of DMC, FEC, FEMC in a volume ratio of 2:4:4, and the rest is the same as Example 1.

[0127] The following reaction occurs in the solid-liquid reactor:

[0128] TEMPO + + LiFeP04→ TEMPO + Li + + FeP04;

[0129] The following reaction occurs in the electrochemical reactor: TEMPO + Li + → TEMPO + + Li.

[0130] Example 5

[0131] Example 5 differs from Example 1 in that the leaching mediator of Example 5 is 2,5-di-tert-butyl-1-methoxy-4-(2'-methoxyethoxy)benzene (DBMMB), the electrolyte is 1 M LiTFSI dissolved in EMC / EC / PC (volume ratio 5:4:1) containing 5 wt% FEC, and the rest is the same as Example 1.

[0132] The following reaction occurs in the solid-liquid reactor:

[0133] DBMMB + + LiFeP04→ DBMMB + Li + + FeP04;

[0134] The following reaction occurs in the electrochemical reactor: DBMMB + Li + → DBMMB + + Li.

[0135] Aspects, embodiments, features, of the present application are to be considered illustrative only and not restrictive in all respects. The scope of the present application is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art, without departing from the spirit and scope of the application as claimed.

[0136] In the preparation method of the present application, the order of the steps is not limited to the order listed, and for those of ordinary skill in the art, changes in the order of the steps without creative effort are within the scope of the present application. In addition, two or more steps or actions can be performed simultaneously.

[0137] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the scope of the application. Various modifications or changes in the described embodiments can be made by those skilled in the art, or equivalents can be substituted, without departing from the spirit of the present application. It is intended that the present application embrace all such modifications and changes and, accordingly, the application should be limited only by the scope of the following claims, and equivalents thereof.

Claims

1. A method for recovering lithium resources from lithium-ion battery cathode materials, characterized in that, Includes the following steps: S1. A leachate including the leaching medium is injected into a solid-liquid reactor filled with lithium-ion battery cathode material. When the leaching medium is in an oxidized state, it undergoes a reduction reaction with the lithium-ion battery cathode material in the solid-liquid reactor. The leaching medium is reduced, and Li element is removed from the lithium-ion battery cathode material to form Li. + The leachate was then pumped into the electrochemical reactor, which was charged at a specific current density. The reduced leachate was then oxidized, and Li... + The reduced elemental Li is deposited on the deposition support of the electrochemical reactor, forming a primary Li deposition. S2. The leachate is circulated in the solid-liquid reactor and the electrochemical reactor by a pump to form multiple Li deposits and keep the lithium-ion battery cathode material from flowing out of the solid-liquid reactor with the leachate. S3. After the reaction is complete, remove the deposition support and wash it to obtain lithium metal foil. The leachate is formed by leaching a lithium salt-containing electrolyte, wherein the leaching medium is a compound capable of forming a redox couple.

2. The recycling method according to claim 1, characterized in that, The leaching medium is any one or a combination of ferrocyanide, acetylacetone metal salts, ferrocene and its derivatives, tetramethylpiperidine oxide and its derivatives, anthraquinone compounds, ketone compounds, alkylbenzenes, and heterocyclic aromatic hydrocarbons.

3. The recycling method according to claim 1, characterized in that, Step S1 includes the following steps: The leachate is injected into a solid-liquid reactor filled with lithium-ion battery cathode material. When the leaching medium is in an oxidized state, it undergoes a reduction reaction with the lithium-ion battery cathode material, reducing the leaching medium. The leachate is then pumped into an electrochemical reactor, which is charged at a specific current density. The leaching medium is then oxidized, and Li... + It is reduced to form elemental Li deposits, resulting in a primary Li deposition. When the leaching medium is in a reduced state, it does not react with the lithium-ion battery cathode material. The leachate is then pumped into the electrochemical reactor, which is charged at a specific current density, causing the leaching medium to oxidize. The oxidized leaching medium is then pumped into the solid-liquid reactor, where it undergoes a reduction reaction with the lithium-ion battery cathode material, reducing the leaching medium. The leachate is then pumped back into the electrochemical reactor, which is charged at a specific current density, causing the leaching medium to oxidize and Li... + It is reduced to form elemental Li deposits, resulting in a primary Li deposition.

4. The recycling method according to claim 1, characterized in that, The lithium salt-containing electrolyte is formed by dissolving lithium salt in an organic solvent. The lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. The organic solvent is one or more of dimethyl carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, and vinylene carbonate. The concentration of the lithium salt is 0.01~2 mol / L.

5. The recycling method according to claim 1, characterized in that, The cathode material of lithium-ion batteries is one or more of the following: nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, and lithium titanate.

6. The recycling method according to claim 1, characterized in that, The circulation flow rate of the leachate is 10~1000 ml / min.

7. The recycling method according to claim 1, characterized in that, The electrochemical reactor was charged at a current density of 0.1 to 100 mA / cm² to bring it to 3.0 to 5.0 V.

8. The method according to claim 1, characterized in that, The solid-liquid reactor has a built-in containment cavity, which is divided into an upper and lower connected feed cavity and a discharge cavity by a filter assembly. The feed cavity is provided with a first feed port, and the discharge cavity is provided with a first discharge port. The electrochemical reactor includes a first current collector and a second current collector serving as positive and negative electrodes, respectively, and the first and second current collectors are connected to the positive and negative electrodes of an external power source, respectively, wherein the first and second current collectors are arranged opposite to each other; a graphite plate is located between the first and second current collectors and connected to the first current collector; a deposition carrier is detachably connected to the second current collector and is arranged opposite to the graphite plate; and a diaphragm is located between the graphite plate and the second current collector. The graphite plate is provided with a flow channel, and a second inlet and a second outlet are provided on the flow channel. The second inlet and the first outlet are connected by a first pipeline, and the second outlet and the first inlet are connected by a second pipeline. A pump body is provided on the first pipeline or the second pipeline.

9. The method according to claim 8, characterized in that, The solid-liquid reactor is provided with a cover plate, a cylinder and a base in sequence along the feeding direction. The cover plate and the cylinder are connected by fasteners, and the cylinder and the base are connected by fasteners. The feeding chamber is located in the cylinder and the discharging chamber is located in the base. The first feeding port is located on the cover plate and is connected to the feeding chamber, and the first discharging port is located on the base and is connected to the discharging chamber. The filter assembly is located at the connection between the cylinder and the base. An agitator is also provided on the cover plate, and the agitator's agitating end extends into the feed chamber through the cover plate, wherein the agitating end is provided with an agitating rod; The cover plate is provided with an air outlet, which is connected to the feed chamber.

10. The method according to claim 8, characterized in that, The electrochemical reactor further includes a first insulating gasket, a second insulating gasket, a first clamping plate, and a second clamping plate, wherein the first insulating gasket is located between the first clamping plate and the first current collector, and the second insulating gasket is located between the second clamping plate and the second current collector. The electrochemical reactor also includes a first sealing gasket and a second sealing gasket, with a graphite felt placed in the pores of the first sealing gasket, a deposition carrier located in the pores of the second sealing gasket, a diaphragm sandwiched between the first and second sealing gaskets, and a structure formed by splicing the first sealing gasket, graphite felt, diaphragm and second sealing gasket connected to one side of the graphite plate with flow channels.

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