USE OF TETRAFLUORPROPEN IN A SOLUTION FOR LEAKING AN ELECTROLYTE SOLUTION FROM A Spent LITHIUM BATTERY AND METHOD FOR SEPARATE AND RECOVERING AN ELECTROLYTE SOLUTION FROM A Spent LITHIUM BATTERY

Abstract

Use of tetrafluoropropene in a solvent for leaching an electrolyte solution from a spent lithium battery.

Description

TECHNICAL AREA

[0001] The present invention relates to the field of recovery of lithium cell materials, in particular a solvent for leaching an electrolyte solution from a spent lithium battery and a method for separating and recovering an electrolyte solution from a spent lithium battery. STATE OF THE ART

[0002] In recent years, the production volume of lithium batteries has increased with the rapid development of the electric vehicle and large-scale energy storage markets, resulting in an explosive rise in the number of used and old lithium batteries. These used and old lithium batteries contain large quantities of rare non-ferrous metals such as cobalt, lithium, nickel, manganese, copper, aluminum, and the like, as well as toxic and harmful compounds such as electrolyte solutions, lithium hexafluorophosphate electrolytes, adhesives, and the like. In particular, the lithium hexafluorophosphate electrolyte in the electrolyte solution is thermally unstable and decomposes at just 60°C to form PF5, producing HF gas, which in turn generates highly dangerous hydrofluoric acid.

[0003] Traditional processes for reprocessing spent lithium batteries can easily generate PF5, HF, or other fluorides, which severely pollute the atmosphere, water, and soil. Furthermore, heavy metal compounds in the materials used for the positive electrode also contribute to water and soil pollution. Materials used for the negative electrode result in dust pollution, while membrane materials contribute to white pollution. Additionally, the loss of valuable metals such as copper, nickel, cobalt, manganese, lithium, and others wastes resources. Therefore, the recovery and safe disposal of spent lithium batteries are of paramount economic and social importance.

[0004] Currently, the problems associated with the recovery and reuse of lithium batteries are attracting considerable public attention. Ensuring the safe disposal and reuse of materials from spent lithium-ion batteries is of lasting importance for achieving a circulating economy and sustainable development.

[0005] Conventional lithium-ion battery recovery processes are complex and, according to existing theoretical research and industrial applications, can be summarized in three steps: pre-processing, secondary processing, and deep processing. The specific procedure is explained in general terms below.

[0006] Pre-processing: Since used and old lithium batteries typically contain a certain amount of residual charge, they must be discharged before recycling. Furthermore, it is possible that the electrolyte solution or electrolyte in the lithium battery generates harmful radiofrequency (RF) in the presence of water. Therefore, suitable pre-processing should be carried out before recycling the lithium battery to eliminate this potential hazard. This pre-processing step primarily involves deep discharge and comminution under a protective gas atmosphere, methods already known and widely used by those skilled in the art.

[0007] Secondary processing: This secondary processing serves to completely separate the materials for the positive and negative electrodes of the lithium battery from the copper or aluminum electrode plates. Common methods for this include thermal decomposition with fire, dissolution in an organic solvent, dissolution in an acidic or alkaline solution, and electrolysis.

[0008] In the thermal decomposition process using fire, the battery is subjected to a temperature of 380°C to 500°C, causing the electrolyte solution and adhesive to decompose and evaporate. This process separates the materials for the positive and negative electrodes from the copper or aluminum electrode plates. While thermal decomposition using fire is a simple and straightforward process, it effectively removes the electrolyte solution and adhesive. However, this process necessarily generates a large quantity of harmful gases, which, if not properly absorbed and cleaned, could easily lead to severe secondary pollution.

[0009] The method of dissolving the electrolyte in an organic solvent is a process for separating the materials for the positive and negative electrodes from the copper or aluminum foils. In this process, the electrolyte solution is dissolved in an organic solvent such as dichloromethane, chloroform, acetone, ethanol, and the like, and then isolated from the solvent by distillation. However, such solvents are highly flammable and explosive, and therefore extremely dangerous. More critically, during the distillation process, the high operating temperature causes the lithium hexafluorophosphate electrolyte in the solution to decompose, producing toxic and harmful fluorides that threaten production and environmental safety.Furthermore, under normal conditions, the remaining solvent adhering to the surface of the materials for the positive and negative electrodes of the lithium battery, the copper or aluminum foils, and the plastics cannot be recovered, which necessarily leads to fire hazards and secondary pollution.

[0010] In the acid-base process, the shredded battery is first immersed in a base solution. The aluminum foil dissolves in the base, while the copper foil remains unaffected. The copper foil and carbon powder immersed in the base are then calcined at a high temperature or dissolved in an organic compound, thus decomposing or dissolving the adhesive. The residue is then immersed in an acid to separate the active materials. This process cannot completely remove the fluorides, and the use of the acid-base solution inevitably causes pollution in the production environment, water, and atmosphere. Furthermore, the process consumes a large quantity of acid-base solution and a significant amount of AlO₂. -1 , which is generated by the solution, is also not favorable for the subsequent separation and purification of the active materials.

[0011] In the electrolysis process, a lead plate is used as the anode, the positive electrode of the battery as the cathode, and a sulfuric acid solution as the electrolyte. An applied electric field is used to detach the material from the positive electrode and simultaneously recover aluminum foil. This process allows for the separation of the positive electrode material to obtain pure aluminum foil and the conversion of some of the positive electrode material into an ionic form in the electrolyte solution, which facilitates subsequent processing. However, this process has the following disadvantages: high electrical energy consumption and poor electrolysis efficiency; the need for safe disposal of the spent sulfuric acid; and the fire hazard at the production site due to the hydrogen gas produced during electrolysis.

[0012] Deep processing: Using a traditional process known as "wet forging", heavy metals such as nickel, cobalt, manganese, and lithium are recovered and reused from the materials for the positive electrode of the lithium battery, a process already known and widely used by experts.

[0013] EP 1 056 146 A1 discloses a process for recycling electrode materials from used lithium batteries, in which cathode materials from the compound class of lithium transition metal mixed oxides from discharged used lithium batteries can be recovered after comminution of the electrode components by mechanical and extractive processing of the same with the aim of removing anode components and other impurities, such as binders and other processing aids and subsequent controlled high-temperature treatment without leaving thermal decomposition products to chemically identical products as those used for the manufacture of the batteries.

[0014] WO 2020 / 112 813 A1 discloses a process comprising processing at least one battery into multiple core sections. Each core section in the plurality of core sections comprises an anode section, a cathode section with a cathode material, a separator section arranged between the anode section and the cathode section, and an electrolyte. The process also includes arranging the multiple core sections in a solvent to produce a mixture of cathode materials from the multiple core sections. The solvent and the electrolyte form an ionically conductive medium, and the mixture of cathode materials is characterized by a substantially homogeneous distribution of an active element in the cathode material.

[0015] US 2015 / 0 017 532 A1 discloses a binder containing a fluoropolymer, the fluoropolymer containing a vinylidene fluoride-based polymerization unit, and a polymerization unit based on a monomer with an amide group represented by -CO-NRR '(R and R' are the same or different and each is a hydrogen atom or an alkyl group, optionally with a substituent group) or an amide bond represented by -CO-NR '- (R represents a hydrogen atom, an alkyl group, optionally with a substituent group, or a phenyl group, optionally with a substituent group) and a solution viscosity of 10 to 20,000 mPa·s. Also disclosed are a positive electrode mixture and a negative electrode mixture comprising the binder, a positive electrode, a negative electrode, and a lithium-ion secondary cell.

[0016] In summary, while conventional methods can solve the problem of partially separating and recovering materials from lithium batteries, they suffer to varying degrees from common problems such as high energy consumption, significant acid and base loss, severe environmental impact, a high risk of fire and explosion, and, in particular, the inability to recover the electrolyte solution or electrolyte. This limits the industrialization of used lithium battery recycling. A solution to these problems is urgently needed. CONTENT OF THE INVENTION

[0017] To solve the aforementioned technical problems, the present invention provides a solvent for leaching an electrolyte solution from a spent lithium battery and a method for separating and recovering an electrolyte solution from a spent lithium battery.

[0018] The above technical problem is solved according to the invention with the following solutions: A solvent for leaching an electrolyte solution in a spent lithium battery comprises tetrafluoropropene.

[0019] The invention has the following advantageous aspects: As the solvent according to the invention for leaching an electrolyte solution from a spent lithium battery, tetrafluoropropene exhibits properties such as low toxicity and flammability. It can dissolve the electrolyte, such as lithium hexafluorophosphate, and due to its boiling point, which is lower than the thermal decomposition temperature of lithium hexafluorophosphate, no harmful compounds are released during leaching and fractional distillation from the electrolyte solution. This allows sufficient recovery of the electrolyte, such as lithium hexafluorophosphate, without polluting the environment.

[0020] Furthermore, it is stipulated that the tetrafluoropropene is 1,3,3,3-tetrafluoropropene and / or 2,3,3,3-tetrafluoropropene.

[0021] Furthermore, it is stipulated that the solvent will continue to contain tetrafluoroethane and that the proportion of tetrafluoroethane in the solvent will be between 10 vol.% and 90 vol.%.

[0022] As a solvent for leaching electrolyte solutions from spent lithium batteries, tetrafluoroethane exhibits properties such as low toxicity and flammability. It can dissolve electrolytes like lithium hexafluorophosphate, and due to its boiling point being lower than the thermal decomposition temperature of lithium hexafluorophosphate, no harmful compounds are released during leaching and fractional distillation from the electrolyte solution. Therefore, it can be mixed with tetrafluoropropene to recover sufficient amounts of electrolyte, such as lithium hexafluorophosphate, without harming the environment.

[0023] The application further discloses a method for separating and recovering an electrolyte solution in a spent lithium battery by leaching using a solvent, the method comprising the following steps: S100: Discharging and shredding the spent lithium battery, mixing with the solvent under vacuum, leaching at 20°C - 50°C and 0.6 MPa to 1.6 MPa to obtain a lye mixture and an insoluble solid, respectively; and S200: Heating the alkali mixture to 20°C - 50°C and fractional distillation at -0.08 MPa to 1.6 MPa to obtain a first recovered solvent and the electrolyte solution.

[0024] During the registration process, the electrolyte solution or electrolyte in a used battery is separated in two steps by leaching. The process is simple and efficient, with electrolyte solution recovery rates of up to 97%, and the recovered solvent is reusable. Because the alkaline mixture and the used lithium battery are mixed under vacuum, the duration of contact between the electrolyte solution or electrolyte and the air, and thus the potential for the formation of harmful substances through contact, are reduced, making the entire leaching process more environmentally friendly.

[0025] Furthermore, it is planned that step S200 will include fractional distillation: S201: Heating the alkali mixture to 20°C - 50°C at 0.6 MPa to 1.6 MPa until the operating pressure falls below 0.6 MPa, collecting and condensing the vapor to obtain a first distillate; S202: Heating the alkali mixture at 20°C - 50°C until the operating pressure falls below 0.2 MPa, increasing the pressure of the steam to 0.6 MPa to 1.6 MPa and condensing to obtain a second distillate; S203: Heating the alkali mixture at 20°C - 50°C, drawing off the steam under vacuum until the operating pressure falls below -0.08 MPa, and then increasing the steam pressure to 0.6 MPa to 1.6 MPa and condensing to obtain a third distillate; and S204: Combining the first, second and third distillates to obtain the first recovered solvent, and collecting the remaining unevaporated liquid to obtain the electrolyte solution.

[0026] During registration, fractional distillation is carried out in three stages so that sufficient solvent can be distilled from the electrolyte.

[0027] Furthermore, the process after step S100 is intended to include a step S300: heating the insoluble solid to 20°C - 50°C at -0.08 MPa to 1.6 MPa, removing the remaining solvent from the surface of the insoluble solid and recovering it to obtain a second recovered solvent and a solid for lithium battery.

[0028] Furthermore, it is planned that step S300 will include the recovery of the remaining solvent: S301: Heating the insoluble solid to 20°C - 50°C at 0.6 MPa to 1.6 MPa until the operating pressure falls below 0.6 MPa, collecting and condensing the vapor to obtain a first remaining solvent; S302: Heating the insoluble solid at 20°C - 50°C until the operating pressure falls below 0.2 MPa, increasing the pressure of the vapor to 0.6 MPa to 1.6 MPa and condensing to obtain a second remaining solvent; S303: Heating the insoluble solid at 20°C - 50°C, drawing off the vapor under vacuum until the operating pressure falls below -0.08 MPa, and then increasing the pressure of the vapor to 0.6 MPa to 1.6 MPa and condensing to obtain a third remaining solvent; and S304: Combining the first, second and third remaining solvents to obtain a second recovered solvent.

[0029] During the registration process, the remaining solvent on the surface of the insoluble solid is removed in three stages, so that the remaining solvent on the surface of the insoluble solid can be effectively removed and collected.

[0030] Furthermore, it is planned that after steps S200 and S300, it will also include a step S400: collecting and combining the first and second recovered solvents to obtain a recovered solvent which is used to leach an electrolyte solution from a spent lithium battery.

[0031] During registration, the first and second recovered solvents are collected and combined so that they can be reused, which reduces costs.

[0032] Furthermore, it is planned that in step S100 the volumetric solid:liquid ratio of the spent lithium battery to the solvent will be 1 : 1 to 1 : 4.

[0033] Furthermore, it is planned that step S100 includes leaching: leaching at a stirring speed of 3 - 5 rpm for 20 - 40 min, repeated 1 - 4 times.

[0034] During registration, the leaching process is carried out several times while stirring to sufficiently dissolve the electrolyte solution. BRIEF DESCRIPTION OF THE FIGURES Fig. Figure 1 shows a general flowchart of the present application; Fig. Figure 2 shows a schematic flow diagram of fractional distillation in step S100; and Fig. Figure 3 shows a schematic flowchart of the recovery of the remaining solvent from the surface of the insoluble solid in step S300. DETAILED EXECUTION FORMS

[0035] The principle and features of the invention are described below in conjunction with the figures. The examples serve only to explain the invention, without limiting its scope.

[0036] The following discloses embodiments or exemplary embodiments for different implementations of the technical solutions of the objects. To simplify the content of the disclosure, specific exemplary embodiments for one or more arrangements of the features are described below. However, the exemplary embodiments described are not intended to limit the invention. In the following description, the expression "that a first feature is connected to a second feature" is understood to mean the embodiment of a direct connection, the embodiment with an additional feature, or furthermore, the embodiment in which one or more other features are used in between to connect or combine the first and second features, whereby the first and second features can be indirectly coupled.

[0037] It is understood that in the following embodiments according to the application, the steps are modifiable, so that some steps can be carried out in a different order or in parallel without affecting the test results according to the application.

[0038] It is understood that the experiments described in the present disclosure are based on an industrial production apparatus where it is difficult to maintain the temperature and pressure at precise values ​​during production, and where the pressure typically changes with the temperature. Therefore, in the following embodiments, the operating pressure and temperature were each set within a range of values. Example 1

[0039] A single component, 1,3,3,3-tetrafluoropropene (HFO-1234ze (Type E)), was selected as the solvent and designated as Solvent I. The key parameters are: boiling point ODP GWP Security level toxicity Pressure at 20°C Pressure at 50°C -19°C 0 6 A1 non-toxic 0.6 MPa 1.3 MPa

[0040] S101: The shredded lithium battery was placed in a sealed container, which was then evacuated at normal temperature to a manometer pressure of -0.06 MPa to -0.08 MPa in order to remove the residual gas inside the container.

[0041] S102: Solvent I was added to the sealed container. The volume of solvent I added was 1 to 2 times the volume of the lithium battery materials. The temperature was increased to 20°C to 50°C and the pressure to 0.6 to 1.3 MPa. The mixture was stirred for 20 to 40 minutes to ensure that the electrolyte solution and the electrolyte it contained were sufficiently dissolved in solvent I.

[0042] S103: A filter system inside the container was activated, so that the liquid was passed through a filter screen and separated from the solid, resulting in a caustic mixture containing the dissolved electrolyte solution and the dissolved electrolyte, and an insoluble solid. The leaching and filtering process was repeated once or twice so that the electrolyte solution and the electrolyte in the battery were completely leached.

[0043] S200: In the sealed container, the alkali mixture of the electrolyte solution was continuously heated to 20°C - 50°C and subjected to fractional distillation of the solvent.

[0044] In this embodiment, fractional distillation can be carried out in the following specific steps: S201: The alkali mixture was heated to 20°C - 50°C at 1.3 MPa until the operating pressure was reduced to 0.6 MPa. The vapor was collected and condensed to obtain a first distillate. S202: The alkali mixture was heated and evaporated at 20°C - 50°C. The vapor was extracted by a compressor, and the operating pressure was increased to 0.6 MPa to 1.3 MPa. A second distillate was obtained by condensation until the operating pressure was reduced to 0.2 MPa. S203: The alkali mixture was heated at 20°C - 50°C. The vapor was extracted by a compressor until the pressure inside the vessel decreased from overpressure to vacuum and remained within a gauge pressure range of -0.08 to -0.09 MPa at a temperature of 20°C - 50°C for more than 5 minutes. This indicated that the leaching solvent had completely evaporated. The vapor pressure was increased to 0.6 MPa to 1.3 MPa, and the vapor was condensed to obtain a third distillate. S204: The first, second and third distillates were combined to obtain the first recovered solvent, and the remaining liquid was collected to obtain the electrolyte solution. S300: In the sealed container, the materials of the insoluble solid were continuously heated to 20°C - 50°C until the remaining solvent on the surface of the insoluble solid had evaporated.

[0045] In the embodiments described in the application, the solvent remaining after evaporation can be recovered. This specifically comprises the following steps: S301: The insoluble solid was heated to 20°C - 50°C at 1.3 MPa until the operating pressure was reduced to 0.6 MPa. The vapor was collected and condensed to obtain a first remaining solvent. S302: The insoluble solid was heated at 20°C - 50°C and extracted by a compressor until the operating pressure inside the vessel was reduced to 0.2 MPa. The pressure of the vapor was increased by the compressor to 0.6 MPa to 1.3 MPa, and a second, remaining solvent was obtained by condensation. S303: The insoluble solid was heated at 20°C - 50°C. A vacuum pump was switched on to extract the vapor until the pressure was reduced to -0.08 MPa. The pressure of the vapor was then increased with a compressor to between 0.6 MPa and 1.3 MPa, and the vapor was condensed to obtain a third remaining solvent until the pressure inside the vessel had decreased from overpressure to vacuum and remained stable within a gauge pressure range of -0.08 to -0.09 MPa for more than 5 minutes. This indicated that the solvents for leaching had completely evaporated. S304: The first, second and third remaining solvents were combined to obtain a second recovered solvent.

[0046] The principle behind the application is that the boiling point of the electrolyte solution is greater than 90°C, meaning it cannot evaporate in the temperature range of 20°C to 50°C. Therefore, within this temperature range, the alkaline mixture can be separated into the electrolyte solution and the solvent by fractional distillation. The decomposition temperature of the electrolyte, lithium hexafluorophosphate, in the electrolyte solution is 60°C. Thus, at an operating temperature not exceeding 50°C, the electrolyte does not decompose, preventing environmental damage.

[0047] In this embodiment, in addition to the effective separation of the materials of the spent lithium battery, the solvent used for leaching can also be effectively recovered, which avoids environmental pollution and waste of materials, saves energy, and reduces costs. Example 2

[0048] A single component, 2,3,3,3-tetrafluoropropene (HFO-1234yf), was selected as the solvent and designated as Solvent II. The key parameters are: boiling point ODP GWP Security level toxicity Pressure at 25°C Pressure at 40°C -29°C 0 4 A2 low toxicity 0.67 MPa <1.6 MPa

[0049] The added volume of solvent II was 1 to 3 times the volume of the lithium battery materials, with a leaching temperature of 25°C - 40°C, a pressure of 0.6 to 1.6 MPa, and a leaching duration of 25 - 40 min with stirring.

[0050] Regarding the fractional distillation and recovery of the electrolyte solution, reference is made to the steps in embodiment 1. Example 3

[0051] 1,3,3,3-Tetrafluoropropene (HFO-1234ze (Type E)) was selected as the solvent at a volume fraction of 90%, and tetrafluoroethane (R134a) was added at a volume fraction of 10% to formulate solvent III for leaching. The key parameters are: boiling point ODP Security level toxicity Pressure at 30°C Pressure at 50°C approx. -20°C 0 A2 low toxicity 0.7MPa 1.4 MPa

[0052] The shredded lithium battery was placed in a suitable sealed container, which was then evacuated to a manometer pressure of -0.06 MPa to -0.08 MPa to remove the gas inside the container.

[0053] The added volume of solvent III was 1 to 4 times the volume of the lithium battery materials, with a leaching temperature of 30°C - 50°C, a pressure of 0.7 to 1.4 MPa, and a leaching duration of 30 - 35 min with stirring.

[0054] Regarding the leaching, fractional distillation and recovery of the electrolyte solution, reference is made to the steps in embodiment 1. Example 4

[0055] 2,3,3,3-Tetrafluoropropene (HFO-1234yf) was selected as the solvent at a volume fraction of 10%, and tetrafluoroethane (R134a) was added at a volume fraction of 90% to formulate solvent IV for leaching. The key parameters are: boiling point ODP Security level toxicity Pressure at 30°C Pressure at 45°C approx. -29°C 0 A2 low toxicity 0.75MPa 1.2 MPa

[0056] The shredded lithium battery was placed in a suitable sealed container, which was then evacuated to a manometer pressure of -0.06 MPa to -0.08 MPa to remove the gas inside the container.

[0057] The added volume of solvent IV was 1 to 2.5 times the volume of the lithium battery materials, with a leaching temperature of 30°C - 45°C, a pressure of 0.6 MPa to 1.2 MPa, and a leaching duration of 20 - 40 min with stirring.

[0058] Regarding the leaching, fractional distillation and recovery of the electrolyte solution, reference is made to the steps in embodiment 1. Example 5

[0059] A solvent IV for leaching was formulated, consisting of 1 / 3 tetrafluoroethane (R134a), 1 / 3 1,3,3,3-tetrafluoropropene (HFO-1234ze (Type E)), and 1 / 3 2,3,3,3-tetrafluoropropene (HFO-1234yf). The key parameters are: boiling point ODP Security level toxicity Pressure at 30°C Pressure at 50°C approx. -29°C 0 A2 low toxicity 0.75MPa 1.5 MPa

[0060] The shredded lithium battery was placed in a suitable sealed container, which was then evacuated to a manometer pressure of -0.06 MPa to -0.08 MPa to remove the gas inside the container.

[0061] The added volume of solvent V was 2 to 3 times the volume of the lithium battery materials, with a leaching temperature of 30°C - 50°C, a pressure of 0.75 to 1.5 MPa, and a leaching duration of 30 min with stirring.

[0062] Regarding the leaching, fractional distillation and recovery of the electrolyte solution, reference is made to the steps in embodiment 1.

[0063] The recoveries of the electrolyte solution and the electrolyte in the embodiments according to the application were calculated, and the results are shown in the following table. Example 1 Example 2 Example 3 Example 4 Example 5 Electrolyte solution / electrolyte recovery ≥99% 98% 97,5% 98% 97% Recovery solvents 99,5% 99% 96% 96% 95%

[0064] It can be seen from the table above that, in the embodiments according to the application, the electrolyte solution in the lithium battery can be effectively recovered with a recovery rate of more than 97%, and the solvent is sufficiently recovered after leaching with a recovery rate of more than 95%, thus enabling solvent circulation for reuse in the subsequent leaching of the spent lithium battery and reducing waste. Prior art methods for recovering the electrolyte solution or electrolyte from the lithium battery cannot achieve the recovery rate attainable according to the invention and cause a significant amount of pollution.

[0065] The application focuses on the disposal of used, unusable lithium batteries, which are leached with a suitable solvent using low energy consumption to recover the electrolyte solution and the dissolved electrolyte. This eliminates the safety risks and environmental impact of used lithium batteries. Furthermore, it enables the separation of the materials for the positive and negative electrodes, the copper foil, the aluminum foil, the plastic, and the iron casing without limitation at normal pressure and temperature. In addition, the solvent used in the embodiments can be efficiently recovered and reused.

[0066] Registration offers the following advantages: The contact of the electrolyte solution or electrolyte with the air is reduced, thereby decreasing the likelihood and duration of the formation of the harmful substance and effectively mitigating the environmental pollution and fire hazard caused by the discharge of the lithium battery's electrolyte solution into the environment. Since the leaching and separation processes are carried out in a completely sealed container, no environmentally harmful gas or liquid is present during the entire procedure.

[0067] In this process, tetrafluoropropene and tetrafluoroethane, which are low-toxicity and not readily flammable, are used as solvents for leaching the electrolyte solution and the electrolyte from the lithium battery. Firstly, they reduce the viscosity of the mixture during leaching and increase its flowability, thus facilitating a smooth leaching process. Secondly, the low boiling point of tetrafluoropropene and tetrafluoroethane is much lower than the temperature for the thermal decomposition of the lithium hexafluorophosphate electrolyte in the electrolyte solution (60°C). Therefore, sufficient lithium hexafluorophosphate is recovered from the electrolyte solution without decomposition, and the solvent can be sufficiently recovered and reused, creating an environmentally friendly process.Thirdly, the use of tetrafluoropropene and tetrafluoroethane, which are non-toxic and non-flammable, as solvents for leaching can significantly reduce the flammability of the lithium battery electrolyte solution, allowing production to take place under safe conditions.

[0068] The solvent for leaching according to the application has a boiling point that is less than 0°C, so that under mild conditions the evaporation, condensation and recovery of the solvent can be achieved, thus avoiding the energy waste in the conventional processes for solvent recovery.

[0069] After the electrolyte solution has been removed from the used lithium battery by leaching, the solids of the battery are in a completely loose state, which allows further separation of nickel, cobalt, lithium, manganese, copper, aluminum, iron and the like.

[0070] Only the preferred embodiments of the present invention have been described above, but the invention is not intended to be limited thereto. All modifications, equivalent substitutions, and extensions that are consistent with the idea and principle of the invention are to be included within the scope of protection of the invention.

Claims

[1] Use of tetrafluoropropene in a solvent for leaching an electrolyte solution from a spent lithium battery. [2] The use according to claim 1, characterized by that the tetrafluoropropene is 1,3,3,3-tetrafluoropropene and / or 2,3,3,3-tetrafluoropropene. [3] The use according to claim 1 or 2, characterized by that the solvent continues to contain tetrafluoroethane and that the proportion of tetrafluoroethane in the solvent is 10 vol.% to 90 vol.%. [4] Method for separating and recovering an electrolyte solution in a spent lithium battery by leaching using a solvent according to any one of claims 1 to 3, characterized by that the procedure includes the following steps: S100: Discharging and shredding the spent lithium battery, mixing with the solvent under vacuum, leaching at 20°C - 50°C and 0.6 MPa to 1.6 MPa to obtain a lye mixture and an insoluble solid, respectively; and S200: Heating the alkali mixture to 20°C - 50°C and fractional distillation at -0.08 MPa to 1.6 MPa to obtain a first recovered solvent and the electrolyte solution, wherein step S200 comprises the fractional distillation: S201: Heating the alkali mixture to 20°C - 50°C at 0.6 MPa to 1.6 MPa, so that the alkali mixture is evaporated until the operating pressure falls below 0.6 MPa, collecting and condensing the vapor to obtain a first distillate; S202: Heating and evaporating the alkali mixture at 20°C - 50°C until the operating pressure falls below 0.2 MPa, increasing the pressure of the vapor to 0.6 MPa to 1.6 MPa and condensing to obtain a second distillate; S203: Heating the alkali mixture at 20°C - 50°C, drawing off the steam under vacuum until the operating pressure falls below -0.08 MPa, and then increasing the steam pressure to 0.6 MPa to 1.6 MPa and condensing to obtain a third distillate; and S204: Combining the first, second and third distillates to obtain the first recovered solvent, and collecting the remaining unevaporated liquid to obtain the electrolyte solution. [5] Method for separating and recovering according to claim 4, characterized by , that after step S100 it also includes a step S300: heating the insoluble solid to 20°C - 50°C at -0.08 MPa to 1.6 MPa, removing the remaining solvent from the surface of the insoluble solid by evaporation and recovery to obtain a second recovered solvent and a solid for lithium battery. [6] Method for separating and recovering according to claim 5, characterized by , that step S300 includes the recovery of the remaining solvent: S301: Heating the insoluble solid to 20°C - 50°C at 0.6 MPa to 1.6 MPa until the operating pressure falls below 0.6 MPa, collecting and condensing the vapor to obtain a first remaining solvent; S302: Heating the insoluble solid at 20°C - 50°C until the operating pressure falls below 0.2 MPa, increasing the pressure of the vapor to 0.6 MPa to 1.6 MPa and condensing to obtain a second remaining solvent; S303: Heating the insoluble solid at 20°C - 50°C, drawing off the vapor under vacuum until the operating pressure falls below -0.08 MPa, and then increasing the pressure of the vapor to 0.6 MPa to 1.6 MPa and condensing to obtain a third remaining solvent; and S304: Combining the first, second and third remaining solvents to obtain a second recovered solvent. [7] Method for separating and recovering according to claim 5 or 6, characterized by , that after steps S200 and S300 it also includes a step S400: collecting and combining the first and second recovered solvents to obtain a recovered solvent which is reused to leach an electrolyte solution from a spent lithium battery. [8] Method for separating and recovering according to claim 4, characterized by , that in step S100 the volumetric solid-liquid ratio of the spent lithium battery to the solvent is 1 : 1 to 1 : 4 v / v. [9] Method for separating and recovering according to claim 4 or 8, characterized by, that in step S100 the leaching includes: Leaching at a stirring speed of 3 - 5 rpm for 20 - 40 min, repeated 1 - 4 times.

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