Method and system for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte

Abstract

The application discloses a low-pressure subcritical fluorohydrocarbon lithium battery electrolyte recovery method and system, which comprises the following steps: low-temperature disassembling a retired lithium battery in a low-oxygen inert closed environment to obtain mixed solid-phase materials of an electrode piece and a diaphragm with attached electrolyte; solid-liquid extraction is carried out under the condition of 15-40 DEG C and 0.6-0.8 MPa low-pressure subcritical condition with fluorohydrocarbon as an extraction medium; after organic liquid phase is separated, the extraction agent is recycled through gasification and condensation; and the electrolyte original solution is retained in the kettle; the original solution is sent into a closed reaction kettle, a silicon-based oxalate intermediate is added under nitrogen protection, lithium hexafluorophosphate is directionally converted into a fluorophosphorus-based lithium salt at low temperature, and then the fluorophosphorus-based lithium salt is purified through low-temperature crystallization to obtain high-purity fluorophosphorus-based lithium salt products and recyclable carbonate solvents. The integrated process of the application avoids the defects of high-temperature pyrolysis of lithium salt decomposition, secondary pollution of wet extraction, and high cost of supercritical high-pressure equipment, the extraction agent can be recycled, the lithium salt and the solvent have high recovery rate, the application is green and low in energy consumption, and the application has the advantages of environmental protection and high recovery income.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology for waste lithium-ion batteries, specifically relating to a method and system for recycling low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte. Background Technology

[0002] Lithium-ion batteries are widely used in new energy vehicles, energy storage equipment and consumer electronics. The scale of retired batteries is increasing year by year. The electrolyte of lithium batteries is composed of lithium hexafluorophosphate, carbonate solvent and functional additives. Direct disposal will release highly toxic substances such as hydrogen fluoride and phosphorus oxides, causing dual pollution to the atmosphere and soil. At the same time, lithium hexafluorophosphate and carbonate solvent have high economic recycling value, and resource recycling has dual significance for environmental protection and industry.

[0003] Existing electrolyte recovery methods have significant drawbacks: high-temperature pyrolysis requires temperatures of 300-500℃, which causes lithium salts to decompose and produce toxic waste gas, resulting in a lithium salt recovery rate of less than 60%; wet extraction uses organic solvents, which are difficult to separate and can easily cause secondary pollution, resulting in a lithium salt recovery rate of less than 70%; supercritical CO2 extraction requires high-pressure conditions of 8-15MPa, which results in high investment and maintenance costs for high-pressure equipment, poor selectivity for lithium salts, and a recovery rate of no more than 85%. The above processes only achieve coarse separation of the electrolyte and do not perform high-value conversion of lithium hexafluorophosphate, resulting in low economic benefits from recovery. Summary of the Invention

[0004] The purpose of this invention is to provide a low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte recovery method and system to solve the technical defects of existing high-temperature pyrolysis lithium salt decomposition, wet extraction secondary pollution, high pressure cost of supercritical CO2 equipment, low lithium salt recovery and utilization rate and no high-value conversion.

[0005] To achieve the above objectives, this application provides the following technical solution: The first aspect of this application provides a method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte, including: Disassemble retired lithium batteries at low temperature in a low-oxygen, inert, and sealed environment to prepare a mixed solid-phase material of electrodes and separators with attached electrolyte; The mixed solid material is placed inside a pressure-resistant sealed extraction vessel, and a fluorinated hydrocarbon extraction medium is introduced into the vessel. The temperature inside the vessel is controlled at 15-40°C and the pressure at 0.6-0.8 MPa to form a low-pressure subcritical environment for solid-liquid extraction. After standing and separating the layers, the fluorinated hydrocarbon organic liquid phase containing the electrolyte components is separated. Fluorinated hydrocarbons are subjected to reduced pressure vaporization, condensation and recovery and reuse through the gasification and condensation unit of the extraction vessel. The original electrolyte solution enriched with lithium salt and carbonate solvent is retained in the vessel. Deliver the raw electrolyte solution to a closed reactor, add the silicon-based oxalate intermediate and introduce nitrogen to establish an isolated atmosphere, and carry out a low-temperature reaction to directionally convert lithium hexafluorophosphate into fluorinated phosphorus-based lithium salt; Deliver the reacted feed liquid to a low-temperature crystallization separation device for crystallization and purification, to separately obtain a high-purity fluorinated phosphorus-based lithium salt finished product and a recyclable carbonate solvent.

[0006] Further, the mixed solid phase material is placed inside a pressure-resistant closed extraction kettle, a fluorinated hydrocarbon extraction medium is introduced into the kettle, the temperature in the kettle is adjusted to 15~40°C and the pressure to 0.6~0.8MPa to form a low-pressure subcritical environment for solid-liquid extraction, which specifically includes: Select at least one of tetrafluoroethane and pentafluoropropane as the fluorinated hydrocarbon extraction medium, keep the pressure in the kettle constant at 0.7~0.75MPa and the temperature constant at 25~35°C, carry out constant temperature and constant pressure extraction continuously for 20~60min, and precisely regulate through the narrow-range working conditions to enhance the dissolution capacity of electrolyte components and improve the completeness of solid-liquid phase separation.

[0007] Further, the purity of the fluorinated hydrocarbon extraction medium is not less than 99.9%, and the feeding mass ratio of the solid phase material to the fluorinated hydrocarbon extraction medium is controlled to be 1:3~1:5; By using the high-purity extraction medium and the adapted solid-liquid ratio, the recovery rate of lithium hexafluorophosphate in the system after extraction is ≥95%, and the recovery rate of the carbonate solvent is ≥98%.

[0008] Further, delivering the raw electrolyte solution to a closed reactor, adding the silicon-based oxalate intermediate and introducing nitrogen to establish an isolated atmosphere, and carrying out a low-temperature reaction to directionally convert lithium hexafluorophosphate into fluorinated phosphorus-based lithium salt specifically includes: Select bisoxalate as the silicon-based oxalate intermediate; Control the molar ratio of the silicon-based oxalate intermediate to lithium hexafluorophosphate to be 1.0~1.2:1, keep the reaction system at a constant temperature of 60~80°C, and carry out continuous reaction for 3~6h to realize sufficient directional conversion of lithium hexafluorophosphate.

[0009] Further, delivering the raw electrolyte solution to a closed reactor, adding the silicon-based oxalate intermediate and introducing nitrogen to establish an isolated atmosphere, and carrying out a low-temperature reaction to directionally convert lithium hexafluorophosphate into fluorinated phosphorus-based lithium salt specifically includes: Adjust the oxygen content inside the closed reactor to below 0.5%, and maintain the whole process of nitrogen closed isolation to inhibit the side reaction of lithium salt hydrolysis; The reaction directionally generates lithium difluorooxalatophosphate LiDFOP, ensuring that the purity of the target product is not less than 99%.

[0010] Further, carrying out reduced pressure vaporization, condensation recovery and cyclic reuse of the fluorinated hydrocarbon through the vaporization and condensation unit supporting the extraction kettle specifically includes: The internal pressure of the extraction vessel is reduced to 0.1–0.2 MPa to complete the vaporization of fluorinated hydrocarbons; The condenser temperature is controlled at 0-5℃ to condense and liquefy vaporized fluorinated hydrocarbons. The extractant obtained from the condensation can be recycled at least 50 times.

[0011] Furthermore, the low-temperature dismantling of retired lithium batteries in a low-oxygen, inert, sealed environment specifically includes: The ambient temperature of the disassembly chamber should be controlled below 50℃; By adjusting the oxygen content inside the disassembly chamber to below 0.5%, disassembly can be completed without pre-discharging the retired lithium battery.

[0012] Furthermore, the step of conveying the reacted liquid to a low-temperature crystallization device for crystallization and purification specifically includes: The internal temperature of the low-temperature crystallization equipment is controlled at 0-5℃ to complete crystallization precipitation; After centrifuging the crystalline material at 3000-5000 rpm, it is vacuum dried at 50-60℃ for 2-3 hours to obtain a high-purity lithium salt product.

[0013] Furthermore, the low-temperature dismantling of retired lithium batteries in a low-oxygen, inert, sealed environment specifically includes: The retired lithium batteries to be processed will be replaced with ternary lithium batteries. Alternatively, lithium iron phosphate energy storage batteries can be selected; Alternatively, consumer-grade lithium-ion single-cell batteries can be selected.

[0014] A second aspect of this application provides a low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte recovery system, comprising: The low-temperature inert dismantling unit is used to dismantle retired lithium batteries in a low-oxygen, sealed, low-temperature environment, producing a mixture of electrode and separator solid phase materials with electrolyte attached. The pressure-resistant, sealed extraction vessel is connected to the discharge end of the low-temperature inert dismantling unit and equipped with a vaporization and condensation unit. It is used to introduce fluorinated hydrocarbon extraction medium to achieve low-pressure subcritical solid-liquid extraction and to reduce pressure and condense to recover the extraction medium for recycling. The closed reaction vessel has its feed end connected to a pressure-resistant closed extraction vessel. It is used to receive the electrolyte stock solution, add the silicon-based oxalate intermediate, and complete the high-value conversion reaction of lithium salt under nitrogen protection. The low-temperature crystallization separation equipment has a feed end connected to the outlet of a sealed reaction vessel. It is used for low-temperature crystallization, centrifugation, and vacuum drying and purification of the reaction liquid to produce high-purity fluorinated phosphorus-based lithium salt and recyclable carbonate solvent.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The process adopts an integrated approach including low-temperature inert dismantling, 15-40℃, 0.6-0.8MPa low-pressure subcritical fluorinated hydrocarbon extraction, extractant recycling, low-temperature lithium salt conversion of raw solution, and low-temperature crystallization purification. This avoids the problems of high-temperature decomposition, high pressure and high cost, and secondary pollution from wet processes. The lithium salt and solvent recovery rates are excellent, and high-purity fluorinated phosphorus-based lithium salts and recyclable carbonate solvents can be produced. It is green, low-consumption, and has high recovery benefits.

[0016] 2. The tetrafluoroethane / pentafluoropropane extraction medium and narrow-range mild operating conditions ensure stable low-pressure subcritical state under temperature and pressure control. The narrow parameter range can enhance the dissolution efficiency of electrolyte components, improve the solid-liquid phase separation effect, reduce electrolyte residue in the electrode membrane solid phase, and fully dissolve the electrolyte without extending the extraction time, thus reducing resource loss caused by lithium salt entrainment in solid phase materials.

[0017] 3. The purity of the extraction medium and the solid-liquid feed ratio: High-purity fluorinated hydrocarbons avoid impurities from interfering with the extraction balance. The appropriate solid-liquid ratio ensures full contact between the two phases, which can stably achieve a lithium hexafluorophosphate recovery rate of ≥95% and a carbonate solvent recovery rate of ≥98%, which is significantly better than traditional recovery processes. This reduces the loss of electrolyte components and improves the overall material resource utilization rate and economic output of raw materials.

[0018] 4. Matching the types, molar ratios, and reaction temperatures of silicon-based oxalate intermediates with the lithium hexafluorophosphate conversion kinetics can promote the complete directional substitution reaction of lithium hexafluorophosphate, reduce unreacted raw material residues, improve lithium salt conversion efficiency, avoid lithium salt intermediate contamination caused by incomplete conversion, and simplify the operation difficulty of subsequent crystallization and purification processes.

[0019] 5. By controlling the low-oxygen nitrogen atmosphere in the reactor, the side reactions of lithium salt hydrolysis are suppressed, and high-purity LiDFOP is generated in a targeted manner. The low-oxygen environment eliminates the problem of lithium salt deterioration caused by water vapor and air. The purity of the target product is stably maintained at over 99%, eliminating the need for multiple recrystallization and refining processes, reducing purification energy consumption, and the produced lithium salt can be directly adapted to meet the high-end requirements of lithium battery electrolyte formulation.

[0020] 6. Reduced pressure and condensation temperature during vaporization and condensation, low temperature and low pressure vaporization and condensation conditions are mild, fluorinated hydrocarbons do not deteriorate at high temperatures, the extraction medium can be recycled more than 50 times, significantly reducing the cost of extraction reagents and hazardous waste disposal, reducing organic solvent waste emissions, simplifying waste liquid treatment procedures, and significantly reducing the long-term operating cost of the entire recycling process.

[0021] 7. The disassembly chamber is a low-temperature, low-oxygen, and sealed environment, allowing batteries to be disassembled without pre-discharging, eliminating the need for a long-term pre-discharge process and shortening the overall processing time. The low-temperature and low-oxygen environment prevents short circuits and fires in charged cells and premature decomposition and volatilization of electrolyte, improving the safety of the disassembly process, reducing early electrolyte loss, and increasing the overall recycling volume.

[0022] 8. Low-temperature crystallization, centrifugation speed and vacuum drying parameters are used to gradient separate and purify lithium salts. Low-temperature crystallization achieves efficient precipitation of lithium salts, centrifugation removes impurities from the mother liquor, and low-temperature vacuum drying avoids thermal decomposition of lithium salts. High-purity solid lithium salt products are obtained in one step, eliminating the need for multiple distillation and recrystallization steps. The purification process is short, energy consumption is low, and the purity of the product is stable and controllable.

[0023] 9. It is compatible with various raw materials such as ternary power batteries, lithium iron phosphate energy storage batteries, and consumer lithium battery cells. One set of equipment can be compatible with mainstream retired lithium-ion batteries on the market without the need for equipment modification for separate lines. It broadens the applicable scenarios of the process. Enterprises can collect and store various waste lithium batteries in a unified manner, reduce the investment in sorting and processing equipment, and improve the versatility and adaptability of production lines. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte recovery method provided by the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0029] To address the technical deficiencies mentioned in the background section, this embodiment provides a method and system for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte.

[0030] The present invention will now be described in further detail with reference to the accompanying drawings: like Figure 1 As shown, in a first aspect of the present invention, a method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte is provided, comprising: S101. Disassemble retired lithium batteries at low temperature in a low-oxygen, inert, and sealed environment to prepare a mixed solid-phase material of electrode sheets and separators with attached electrolyte. For example, a low-temperature inert dismantling unit is used to complete the operation. The dismantling unit is a completely sealed cavity structure. Nitrogen gas is continuously introduced into the cavity as an inert protective gas, and the oxygen content inside the cavity is stably controlled below 0.5%. The overall ambient temperature of the dismantling cavity is maintained at 50°C or below. There is no need to discharge the retired lithium battery beforehand; the complete retired lithium battery is directly sent into the cavity. The battery shell and cell are separated by a low-temperature mechanical cutting method, and the internal electrode plates and separator of the cell are separated. The cutting process is completely purged with nitrogen to isolate air. After cutting, the positive electrode plates, negative electrode plates, and separator with surface adsorption and electrolyte are collected and mixed to obtain a mixed solid phase material. The material is then transported to the next process in a sealed manner at the outlet. No material comes into contact with the outside air throughout the process, avoiding premature evaporation of electrolyte and hydrolysis failure of lithium hexafluorophosphate when exposed to water vapor. This step solves the problems of battery short circuit and fire and premature decomposition and loss of electrolyte in traditional dismantling processes, and completely preserves the electrolyte components inside the cell.

[0031] S102. The mixed solid material is placed inside a pressure-resistant sealed extraction vessel, and a fluorinated hydrocarbon extraction medium is introduced into the vessel. The temperature inside the vessel is controlled at 15-40°C and the pressure at 0.6-0.8 MPa to form a low-pressure subcritical environment for solid-liquid extraction. After standing and separating the layers, the fluorinated hydrocarbon organic liquid phase containing the electrolyte components is separated. For example, the mixed solid material produced by S101 is conveyed into a pressure-resistant sealed extraction vessel in a closed system. The extraction vessel is a pressure-bearing sealed reaction container. After feeding, all sealing valves are closed to achieve complete sealing. Fluorinated hydrocarbon extraction medium is continuously introduced into the vessel, and the temperature control and pressure regulation modules of the vessel are turned on simultaneously to stabilize the temperature in the vessel between 15 and 40°C and adjust the pressure in the vessel to 0.6 to 0.8 MPa. This temperature and pressure range constitutes a low-pressure subcritical equilibrium state for fluorinated hydrocarbons, which greatly enhances the solubility of fluorinated hydrocarbon molecules and can fully dissolve the electrolyte (lithium hexafluorophosphate, carbonate solvent, and additives) adsorbed on the surface of the electrode and diaphragm. After continuous extraction at constant temperature and pressure, the mixture is allowed to stand for 30 minutes to achieve natural solid-liquid separation. The lower solid phase is the electrode and diaphragm residue after the electrolyte has been removed, and the upper liquid phase is the fluorinated hydrocarbon organic liquid phase containing all electrolyte components. The liquid phase discharge pipeline is opened to separate the organic liquid phase, and the solid residue is discharged separately for metal recovery treatment. This step relies on a low-pressure, mild, and subcritical system to avoid high-temperature and high-pressure conditions, while balancing the adequacy of electrolyte extraction with the safety and cost of equipment.

[0032] S103. Fluorinated hydrocarbons are subjected to reduced pressure vaporization, condensation and recovery and reuse through the vaporization and condensation unit of the extraction vessel. The electrolyte stock solution enriched with lithium salt and carbonate solvent is retained in the vessel. For example, the extraction vessel is equipped with an independent vaporization and condensation unit. After the organic liquid phase is separated, the pressure relief valve of the vaporization unit is opened to reduce the pressure inside the vessel. The fluorinated hydrocarbon medium inside the vessel is heated and vaporized to form fluorinated hydrocarbon vapor. The fluorinated hydrocarbon vapor is transported to the condenser through a closed pipeline. The condenser liquefies the fluorinated hydrocarbon vapor through low-temperature heat exchange. The liquefied pure fluorinated hydrocarbon extraction medium is stored in a circulating storage tank. The storage tank is connected to the feed port of the extraction vessel through a return pipeline to realize the recycling of the extraction medium. After the pressure inside the vessel is reduced and the fluorinated hydrocarbons are completely vaporized and separated, the bottom of the vessel retains the electrolyte stock solution, which has been removed from the extraction medium and is highly enriched with lithium hexafluorophosphate and carbonate solvent. The stock solution is transported to the closed reaction vessel through a closed pipeline. There is no fluorinated hydrocarbon waste gas discharged throughout the process. The extraction medium can be repeatedly recycled and reused, which greatly reduces the cost of reagent consumption.

[0033] S104. The electrolyte stock solution is transported to a closed reaction vessel, a silicon-based oxalate intermediate is added and nitrogen is introduced to create an isolation atmosphere. The low-temperature reaction causes lithium hexafluorophosphate to be directionally converted into fluorophosphoric lithium salt. For example, the electrolyte stock solution produced by S103 is sealed and transported to a sealed reactor. High-purity nitrogen is continuously introduced into the reactor to replace the air inside, creating an oxygen-free and isolated reaction environment. A silica-based oxalate intermediate is quantitatively added into the reactor, and the system is stirred to mix evenly. The reaction system is controlled at a low temperature and isothermal. Lithium hexafluorophosphate in the electrolyte stock solution undergoes a directional substitution reaction with the silica-based oxalate intermediate, and the molecular structure is reconstructed to generate fluorophosphate-based lithium salt (lithium difluorooxalate phosphate LiDFOP). Nitrogen gas is continuously purged to isolate water vapor and oxygen, suppressing lithium salt hydrolysis and oxidation side reactions throughout the process, ensuring that the conversion reaction proceeds in a directional manner and that no large amounts of impurity byproducts are generated. After the reaction is completed, a mixed reaction solution is obtained and sealed and transported to a low-temperature crystallization and separation device. This step realizes the high-value conversion of lithium hexafluorophosphate, transforming low-value basic lithium salt into a high-end additive raw material for lithium batteries, and improving the economic value of the recycled products.

[0034] S105. The reaction liquid is transported to a low-temperature crystallization separation device for crystallization and purification to obtain high-purity fluorinated phosphorus-based lithium salt product and recyclable carbonate solvent, respectively. For example, the reaction liquid generated in S104 is passed into a low-temperature crystallization separation device. The low-temperature environment inside the device promotes the crystallization and precipitation of fluorinated phosphorus-based lithium salt, forming a solid-liquid mixed suspension. The crystallized solid is then processed by centrifugation and vacuum drying to remove the carbonate mother liquor attached to the surface of the solid, resulting in a solid high-purity fluorinated phosphorus-based lithium salt product. The main component of the mother liquor discharged by centrifugation is carbonate solvent. After collecting the mother liquor, it is purified by simple distillation to obtain a recycled carbonate solvent with qualified purity that can be reused in the preparation of lithium battery electrolyte. This achieves the simultaneous recovery and purification of the two core components of the electrolyte, with no waste liquid or solid waste ineffective discharge.

[0035] Example 2: This embodiment is based on the process of Embodiment 1, and refines the parameter control of the S102 low-pressure subcritical solid-liquid extraction step, limiting the type of extraction medium, the precise temperature and pressure range, and the extraction time, thereby improving the electrolyte dissolution and separation effect.

[0036] Specifically, in the process of S102, where mixed solid materials are introduced into a pressure-resistant sealed extraction vessel and fluorinated hydrocarbon extraction medium is introduced to construct a low-pressure subcritical extraction environment, any one or a combination of two of tetrafluoroethane and pentafluoropropane is selected as the fluorinated hydrocarbon extraction medium. After the vessel sealing structure is closed, the pressure inside the vessel is kept constant at 0.7–0.75 MPa by the pressure stabilization module, and the temperature inside the vessel is kept constant within a narrow range of 25–35°C by the temperature control module. Under this precise temperature and pressure condition, constant temperature and pressure extraction is carried out for 20–60 minutes. The stable condition within the narrow range can maintain the stability of the subcritical dissolution capacity of fluorinated hydrocarbons, enhance the dissolution efficiency of polar components in the electrolyte, reduce the adsorption and residue of electrolyte components inside the solid electrode membrane, and after standing and stratification, the solid-liquid phase interface is clear, the amount of electrolyte entrained in the solid phase is greatly reduced, the loss of lithium salt and solvent materials is reduced, and full extraction can be achieved without extending the extraction time, thus shortening the single-batch extraction cycle.

[0037] Example 3: This embodiment is based on the extraction process of Example 2, and further limits the purity of the extraction medium and the mass ratio of solid material to extraction medium, so as to steadily improve the comprehensive recovery rate of lithium salt and solvent.

[0038] Specifically, tetrafluoroethane / pentafluoropropane with a purity of not less than 99.9% is selected as the extraction medium. The high-purity medium is free of moisture and impurities that could interfere with the extraction balance, avoiding side reactions between impurities and lithium hexafluorophosphate that could lead to lithium salt loss. During the feeding stage, the mass ratio of the mixed solid material to the fluorinated hydrocarbon extraction medium is strictly controlled at 1:3 to 1:5. This ratio ensures that the solid material is completely immersed in the extraction medium, allowing for sufficient contact and mass transfer between the solid and liquid phases. After extraction is completed under the conditions of 0.7–0.75 MPa, 25–35 °C, and 20–60 min, the overall recovery rate of lithium hexafluorophosphate in the system is consistently ≥95%, and the recovery rate of carbonate solvent is consistently ≥98%. Compared with traditional wet, pyrolysis, and supercritical processes, the recovery efficiency is significantly improved, maximizing the retention of valuable components in the electrolyte and increasing the overall resource utilization rate of the process.

[0039] Example 4: This embodiment is based on the complete process of Embodiment 1, and refines the types of intermediates, material molar ratios, and reaction temperature and time parameters of the S104 electrolyte stock solution conversion reaction process to improve the completeness of lithium hexafluorophosphate conversion.

[0040] Specifically, in S104, when the electrolyte stock solution is sent into a closed reactor and a silicon-based oxalate intermediate is added for a low-temperature directional conversion reaction, bis(trimethylsilyl)oxalate is selected as the silicon-based oxalate intermediate. The intermediate is added quantitatively according to a molar ratio of 1.0 to 1.2:1 between the intermediate and the lithium hexafluorophosphate in the stock solution, with a small excess of the intermediate to ensure complete reaction of the lithium hexafluorophosphate. After the addition is completed, the reactor's constant temperature module is turned on to maintain the reaction system at a stable temperature of 60 to 80°C, and the reaction is continuously stirred for 3 to 6 hours. The appropriate molar ratio, temperature and reaction time match the kinetics of the lithium hexafluorophosphate substitution reaction, which greatly reduces the amount of unreacted lithium hexafluorophosphate residue, avoids the raw materials from being mixed in the product, simplifies the separation difficulty of the subsequent low-temperature crystallization and purification process, reduces repeated recrystallization operations, and reduces energy consumption in the purification process.

[0041] Example 5: This embodiment is based on the conversion reaction process of Example 4, and optimizes the control of the inert protective atmosphere inside the closed reactor to suppress hydrolysis side reactions and steadily improve the purity of LiDFOP products.

[0042] Specifically, during the entire process of the S104 lithium hexafluorophosphate directional conversion reaction, high-purity nitrogen is continuously introduced into the sealed reactor to replace the air inside the reactor. The oxygen content inside the reactor is monitored online and controlled to below 0.5%. The nitrogen-sealed isolation atmosphere is maintained throughout the process to prevent water vapor and oxygen in the air from contacting the lithium salt material, thus preventing the hydrolysis and deterioration of lithium hexafluorophosphate and intermediate products to generate hydrogen fluoride and phosphoric acid impurities. Under the intermediate ratio, 60-80℃, and 3-6h reaction conditions specified in Example 4, lithium hexafluorophosphate is directionally converted into lithium difluorooxalate phosphate (LiDFOP) with no large amount of by-products generated. The purity of the target lithium salt product obtained after crystallization and purification of the reaction material is consistently not less than 99%, eliminating the need for repeated distillation and recrystallization purification processes. The high-purity LiDFOP produced can be directly used as an additive for high-end lithium battery electrolytes, broadening the application scenarios of the recycled product.

[0043] Example 6: This embodiment is based on the complete process of Embodiment 1, and refines the pressure and temperature parameters of the S103 vaporization and condensation cycle process, extends the service life of the extraction medium cycle, and reduces the cost of reagent procurement.

[0044] Specifically, when using the S103 extraction vessel with its associated vaporization and condensation unit to recover fluorinated hydrocarbon extraction media, the pressure relief valve is slowly opened to gradually reduce the internal pressure of the pressure-resistant extraction vessel to 0.1–0.2 MPa. This low-pressure environment promotes the low-temperature vaporization of the fluorinated hydrocarbon media, eliminating the need for high-temperature heating and preventing the fluorinated hydrocarbons from decomposing and becoming ineffective at high temperatures. The vaporized fluorinated hydrocarbon vapor is then introduced into the condenser, with the condenser's heat exchange temperature maintained at a stable 0–5°C. This low-temperature heat exchange causes the fluorinated hydrocarbon vapor to liquefy rapidly. The liquefied pure fluorinated hydrocarbon is stored in a closed-loop storage tank. The storage tank is connected to the extraction vessel's feed pipeline, allowing the liquefied extraction media to be directly transported back to the extraction vessel for repeated extraction operations. Each batch of extraction media can be recycled at least 50 times, significantly reducing the amount of fresh fluorinated hydrocarbon reagent required and lowering the long-term material costs of the entire recovery process. Simultaneously, it avoids the environmental treatment costs associated with disposing of waste extraction media as hazardous waste.

[0045] Example 7: This embodiment is based on the disassembly process of S101 in Embodiment 1, refines the temperature and oxygen content control conditions of the disassembly cavity, eliminates the battery pre-discharge process, and improves disassembly safety and processing efficiency.

[0046] Specifically, during the S101 low-oxygen, inert, sealed, low-temperature dismantling of retired lithium batteries, the overall ambient temperature of the dismantling chamber is stably controlled below 50°C. The entire process is conducted in a low-temperature environment to prevent the electrolyte inside the cell from evaporating and decomposing due to heat. Nitrogen is continuously introduced into the chamber to replace the air, and the oxygen content inside the chamber is controlled in real time to below 0.5%, creating an oxygen-free, inert, and isolated space. The retired lithium batteries to be dismantled do not need to undergo long-term discharge treatment in advance, and the intact charged cells can be directly sent into the chamber for cutting and dismantling. The low-temperature, low-oxygen, sealed environment eliminates the safety hazards of short circuits, fires, and explosions during the cutting of charged cells, while also preventing premature evaporation and loss of electrolyte, eliminating the need for battery pre-discharge pre-treatment, shortening the entire recycling process, and increasing the processing capacity of a single batch of materials.

[0047] Example 8: This embodiment is based on the crystallization and purification steps of Example 1 S105, and refines the operating parameters of the entire set of equipment for crystallization, centrifugation, and vacuum drying to stably prepare high-purity solid lithium salt products.

[0048] Specifically, when the reaction liquid is transported to the low-temperature crystallization separation equipment for purification in step S105, the internal temperature of the low-temperature crystallization equipment is first controlled at 0-5℃ for constant temperature and static setting, which promotes the slow crystallization and precipitation of fluorinated phosphorus-based lithium salt in the system, forming a solid-liquid mixed suspension. The crystallized suspension is then transported to a centrifugal separation equipment and centrifuged at a speed of 3000-5000 rpm to remove the carbonate mother liquor impurities adsorbed on the crystal surface. The solid lithium salt after centrifugation is then sent to a vacuum drying equipment and vacuum dried at a temperature of 50-60℃ for 2-3 hours. The low-temperature vacuum environment prevents the lithium salt from being decomposed and oxidized by heat. After drying, a dry high-purity lithium salt solid product is directly obtained. The entire purification process completes crystallization, impurity removal, and drying in one step. The process is simple, energy consumption is low, and the purity of the product is stable and controllable.

[0049] Example 9: This embodiment is based on the disassembly process S101 in Embodiment 1, which limits the types of retired lithium battery raw materials that this process can handle, broadens the scope of application of the process, and improves the versatility of the production line.

[0050] Specifically, when performing the S101 low-temperature inert sealed dismantling process, three types of mainstream lithium battery raw materials can be selected for the retired lithium batteries to be processed. These three raw materials can be processed separately in batches or mixed and fed into the same batch: the first type is ternary lithium-ion power batteries for new energy vehicles; the second type is lithium iron phosphate energy storage batteries for energy storage power stations; and the third type is consumer lithium-ion single cells for mobile phones, laptops, and digital devices. The entire recycling process and equipment do not require parameter modification or adjustment for different battery types. One production line is compatible with mainstream retired lithium-ion battery products on the market. Enterprises can collect and store various types of waste lithium batteries in a unified manner without the need for separate lines and sorting for independent processing, reducing the investment in purchasing multiple sets of equipment and improving the adaptability and production flexibility of the waste lithium battery recycling production line.

[0051] A second aspect of the present invention provides a low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte recovery system, comprising: Low-temperature inert dismantling unit, pressure-resistant sealed extraction vessel, sealed reaction vessel, low-temperature crystallization separation equipment; The low-temperature inert dismantling unit has its discharge end connected to the inlet of the pressure-resistant sealed extraction vessel via a closed conveying pipeline. The unit is equipped with a nitrogen purging pipeline, a low-temperature temperature control module, a cutting mechanism, and an online oxygen content monitoring module. It is used to cut and dismantle various retired lithium batteries in a low-oxygen, sealed, and low-temperature environment to produce a mixed solid phase material of electrode and separator loaded with electrolyte. The material is conveyed to the extraction vessel in a sealed manner, completely isolated from air. The pressure-resistant and sealed extraction vessel is equipped with an independent vaporization and condensation unit. The gas phase reflux pipeline of the vaporization and condensation unit is connected to the feed inlet of the extraction vessel, and the liquid phase discharge pipeline of the extraction vessel is connected to the feed end of the sealed reaction vessel. The extraction vessel receives mixed solid materials and introduces a fluorinated hydrocarbon medium to create a low-pressure subcritical environment of 0.6–0.8 MPa and 15–40°C to complete solid-liquid extraction. The vaporization and condensation unit separates the fluorinated hydrocarbons under reduced pressure and recycles them. The electrolyte raw material produced at the bottom of the vessel is transported to the reaction vessel. The sealed reaction vessel is equipped with a nitrogen protection pipeline, an intermediate feeding port, and a constant-temperature stirring module. The feed pipeline receives the electrolyte raw material transported from the extraction vessel and is used to add the silicon-based oxalate intermediate. The nitrogen gas isolates the low-temperature reaction, directionally converting lithium hexafluorophosphate into lithium difluorooxalate phosphate. The reaction liquid is transported to the low-temperature crystallization separation equipment through the bottom discharge pipeline. The low-temperature crystallization separation equipment integrates a low-temperature crystallization chamber, a high-speed centrifuge, and a vacuum drying chamber. The feed end is connected to the outlet of the sealed reaction vessel to receive the converted reaction liquid. The low-temperature crystallization, centrifugal impurity removal, and low-temperature vacuum drying are completed sequentially to produce high-purity fluorinated phosphorus-based lithium salt solid products and recyclable carbonate solvent mother liquor. The mother liquor can be recycled and reused in the electrolyte preparation section.

[0052] In actual production, the recovered ternary lithium-ion batteries, lithium iron phosphate energy storage batteries, and consumer lithium-ion battery cells are first sent to a low-temperature inert dismantling unit. They are then cut in a nitrogen-sealed environment below 50°C and with an oxygen content below 0.5%, without pre-discharge, to obtain a mixed solid-phase material. This solid-phase material is then sealed and sent to a pressure-resistant extraction vessel, where tetrafluoroethane / pentafluoropropane of 99.9% purity or higher is introduced at a solid-liquid mass ratio of 1:3 to 1:5. Extraction is performed at 0.7 to 0.75 MPa and 25 to 35°C for 20 to 60 minutes. After extraction, the fluorinated hydrocarbons are vaporized under reduced pressure at 0.1 to 0.2 MPa, and the extractant is condensed and recovered at 0 to 5°C, circulating more than 50 times. The original electrolyte solution in the vessel is then sent to a sealed reaction vessel. Molybdenum is added... A bis(trimethylsilyl)oxalate solution with a ratio of 1.0–1.2:1 is reacted at 60–80°C for 3–6 hours under nitrogen protection with oxygen content controlled below 0.5% in the reactor, resulting in the directional formation of LiDFOP with a purity of over 99%. The reaction solution is then fed into a crystallization device, where it is crystallized at 0–5°C, centrifuged at 3000–5000 rpm, and vacuum dried at 50–60°C for 2–3 hours to obtain high-purity lithium salt products and recyclable carbonate solvent. The entire process operates continuously using an integrated closed-loop recovery system, achieving a lithium salt recovery rate of ≥95% and a solvent recovery rate of ≥98%. The entire process is conducted at low temperature and low pressure, without high-temperature decomposition, with closed-loop recycling of the extractant and high-value-added products, effectively addressing the shortcomings of existing recovery processes.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte, characterized in that, include: Disassemble retired lithium batteries at low temperature in a low-oxygen, inert, and sealed environment to prepare a mixed solid-phase material of electrodes and separators with attached electrolyte; The mixed solid material is placed inside a pressure-resistant sealed extraction vessel, and a fluorinated hydrocarbon extraction medium is introduced into the vessel. The temperature inside the vessel is controlled at 15-40°C and the pressure at 0.6-0.8 MPa to form a low-pressure subcritical environment for solid-liquid extraction. After standing and separating the layers, the fluorinated hydrocarbon organic liquid phase containing the electrolyte components is separated. Fluorinated hydrocarbons are subjected to reduced pressure vaporization, condensation and recovery and reuse through the gasification and condensation unit of the extraction vessel. The original electrolyte solution enriched with lithium salt and carbonate solvent is retained in the vessel. The electrolyte stock solution is transported to a closed reaction vessel, a silicon-based oxalate intermediate is added, and nitrogen gas is introduced to create an isolated atmosphere. The low-temperature reaction causes lithium hexafluorophosphate to be directionally converted into fluorophosphoric lithium salt. The reaction solution is then transported to a low-temperature crystallization separation device for crystallization and purification, yielding high-purity fluorinated phosphorus-based lithium salt and recyclable carbonate solvent, respectively.

2. The method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte according to claim 1, characterized in that, The mixed solid material is placed inside a pressure-resistant, sealed extraction vessel. A fluorinated hydrocarbon extraction medium is introduced into the vessel, and the temperature is controlled at 15–40°C and the pressure at 0.6–0.8 MPa to create a low-pressure subcritical environment for solid-liquid extraction. Specifically, this includes: At least one of tetrafluoroethane and pentafluoropropane was selected as the fluorinated hydrocarbon extraction medium. The pressure inside the vessel was kept constant at 0.7–0.75 MPa and the temperature was kept constant at 25–35 °C. The constant temperature and pressure extraction was carried out for 20–60 min. By precisely controlling the narrow range of operating conditions, the dissolution capacity of the electrolyte components was enhanced and the degree of solid-liquid phase separation was improved.

3. The method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte according to claim 2, characterized in that, The purity of the fluorinated hydrocarbon extraction medium is not less than 99.9%, and the mass ratio of solid material to fluorinated hydrocarbon extraction medium is controlled to be 1:3 to 1:

5. Using a high-purity extraction medium and a suitable solid-liquid ratio, the recovery rate of lithium hexafluorophosphate in the system after extraction is ≥95%, and the recovery rate of carbonate solvent is ≥98%.

4. The method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte according to claim 1, characterized in that, The process involves transporting the electrolyte stock solution to a sealed reactor, adding a silicon-based oxalate intermediate, and introducing nitrogen gas to create an isolated atmosphere. A low-temperature reaction then directionally converts lithium hexafluorophosphate into fluorophosphorus-based lithium salts. Specifically, this includes: Dioxalate was selected as the intermediate for silicon-based oxalate; The molar ratio of the silicon-based oxalate intermediate to lithium hexafluorophosphate is controlled at 1.0 to 1.2:

1. The reaction system is kept at a constant temperature of 60 to 80°C and the reaction is carried out continuously for 3 to 6 hours to achieve full directional conversion of lithium hexafluorophosphate.

5. The method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte according to claim 4, characterized in that, The process involves transporting the electrolyte stock solution to a sealed reactor, adding a silicon-based oxalate intermediate, and introducing nitrogen gas to create an isolated atmosphere. A low-temperature reaction then directionally converts lithium hexafluorophosphate into fluorophosphorus-based lithium salts. Specifically, this includes: The oxygen content inside the sealed reactor is controlled to below 0.5%, and nitrogen gas is used to completely seal and isolate the reactor to suppress lithium salt hydrolysis side reactions. The reaction is directed to generate lithium difluorooxalate phosphate (LiDFOP), ensuring that the purity of the target product is not less than 99%.

6. The method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte according to claim 1, characterized in that, The process of vacuum vaporization, condensation recovery, and recycling of fluorinated hydrocarbons via an extraction vessel equipped with a vaporization and condensation unit specifically includes: The internal pressure of the extraction vessel is reduced to 0.1–0.2 MPa to complete the vaporization of fluorinated hydrocarbons; The condenser temperature is controlled at 0-5℃ to condense and liquefy vaporized fluorinated hydrocarbons. The extractant obtained from the condensation can be recycled at least 50 times.

7. The method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte according to claim 1, characterized in that, The low-temperature dismantling of retired lithium batteries in a low-oxygen, inert, sealed environment specifically includes: The ambient temperature of the disassembly chamber should be controlled below 50℃; By adjusting the oxygen content inside the disassembly chamber to below 0.5%, disassembly can be completed without pre-discharging the retired lithium battery.

8. The method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte according to claim 1, characterized in that, The step of conveying the reacted liquid to a low-temperature crystallization device for crystallization and purification specifically includes: The internal temperature of the low-temperature crystallization equipment is controlled at 0-5℃ to complete crystallization precipitation; After centrifuging the crystalline material at 3000-5000 rpm, it is vacuum dried at 50-60℃ for 2-3 hours to obtain a high-purity lithium salt product.

9. The method for recovering low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte according to claim 1, characterized in that, The low-temperature dismantling of retired lithium batteries in a low-oxygen, inert, sealed environment specifically includes: The retired lithium batteries to be processed will be replaced with ternary lithium batteries. Alternatively, lithium iron phosphate energy storage batteries can be selected; Alternatively, consumer-grade lithium-ion single-cell batteries can be selected.

10. A low-pressure subcritical fluorinated hydrocarbon lithium battery electrolyte recovery system, characterized in that, include: The low-temperature inert dismantling unit is used to dismantle retired lithium batteries in a low-oxygen, sealed, low-temperature environment, producing a mixture of electrode and separator solid phase materials with electrolyte attached. The pressure-resistant, sealed extraction vessel is connected to the discharge end of the low-temperature inert dismantling unit and equipped with a vaporization and condensation unit. It is used to introduce fluorinated hydrocarbon extraction medium to achieve low-pressure subcritical solid-liquid extraction and to reduce pressure and condense to recover the extraction medium for recycling. The closed reaction vessel has its feed end connected to a pressure-resistant closed extraction vessel. It is used to receive the electrolyte stock solution, add the silicon-based oxalate intermediate, and complete the high-value conversion reaction of lithium salt under nitrogen protection. The low-temperature crystallization separation equipment has a feed end connected to the outlet of a sealed reaction vessel. It is used for low-temperature crystallization, centrifugation, and vacuum drying and purification of the reaction liquid to produce high-purity fluorinated phosphorus-based lithium salt and recyclable carbonate solvent.

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