In-situ preparation method of a solid polymer electrolyte, its recycling method and a lithium-ion battery

Abstract

The present invention belongs to the field of lithium-ion batteries, and particularly relates to an in-situ preparation method of a solid polymer electrolyte, its recycling method, and a lithium-ion battery. The preparation method provided by the present invention comprises the following steps: a) loading an electrolyte precursor onto the surface of a battery separator, and then assembling it with a lithium-ion battery positive electrode and a lithium-ion battery negative electrode to obtain a semi-finished lithium-ion battery; in step a), the components of the electrolyte precursor include a polymerizable monomer, a lithium salt, and an initiator, and the lithium salt is lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, etc.; b) under heating conditions, the electrolyte precursor in the semi-finished lithium-ion battery undergoes in-situ polymerization on the battery separator to obtain a solid polymer electrolyte loaded on the battery separator. The preparation method provided by the present invention does not require an external catalyst, and the obtained solid polymer electrolyte can be depolymerized by heating, having good environmental and economic benefits.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion batteries, and particularly relates to an in-situ preparation method and a recycling method of a solid polymer electrolyte and a lithium-ion battery. Background Art

[0002] Since the development of lithium-ion batteries to date, they have been widely used in major fields such as new energy vehicles, consumer electronics, and energy storage. Lithium batteries have a relatively high energy density and a long cycle life. The energy density can reach 100-200 Wh / kg, and the cycle life is greater than 1000 times, which is much higher than that of other secondary batteries. Therefore, they are the objects of vigorous development at present. Most of the commercially available lithium-ion batteries on the market are liquid lithium-ion batteries, and the electrolytes used therein are low-boiling and flammable organic liquids such as carbonates and ethers. Once a large amount of heat is released due to an internal short circuit in this type of liquid battery, it is extremely likely to cause safety accidents such as battery combustion or even explosion. Compared with traditional liquid electrolyte lithium-ion batteries, solid polymer batteries have higher safety, better mechanical properties, stronger processability, and can use high-energy density electrode materials such as metallic lithium to further improve the energy density of the battery. Therefore, solid polymer batteries have a very broad application prospect.

[0003] Compared with the ionic conductivity of liquid electrolytes of 10 -2 ~10 -3 S·cm -1 , the development of solid polymer electrolytes is limited by their low ionic conductivity (usually in the range of 10 -5 ~10 -6 S·cm -1 ). Due to their low ionic conductivity, solid polymer batteries are difficult to be used at room temperature, difficult to achieve fast charging technology, and due to the large internal resistance of solid polymer batteries, irreversible energy loss will occur during the charging process, resulting in a decrease in capacity. In addition, the preparation process of solid polymer batteries is complex. It is necessary to pre-prepare a solid polymer electrolyte and then assemble it with the positive and negative electrode plates of the battery in a winding or laminating manner. The all-solid-state battery obtained by this ex-situ preparation method has poor interfacial compatibility between the internal electrodes and the solid electrolyte, resulting in a very large interfacial impedance, seriously affecting the power density of the battery, and the preparation process is complex and the cost is high.

[0004] To solve the above problems existing in the ex-situ preparation technology of solid polymer electrolytes, researchers have continuously developed systems for in-situ polymerization to prepare solid polymer electrolytes directly on battery components. However, the existing technologies for in-situ polymerization to prepare solid polymer electrolytes generally require the additional introduction of catalysts, and these additional introduced catalysts may lead to the deterioration of battery performance.

[0005] In addition, as the market share of lithium-ion batteries continues to expand, the problem of waste after battery use has gradually emerged. Common solid polymer electrolytes are all based on polyolefin or polyether structures. Since these polymers are difficult to degrade and difficult to separate from lithium salts, the common treatment methods for current solid polymer electrolytes are landfill or combustion, which not only causes a large amount of waste of high-value electrolyte salts, but also may cause environmental pollution. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an in-situ preparation method of a solid polymer electrolyte, its recovery method, and a lithium-ion battery. The preparation method provided by the present invention uses an electrolyte salt as a catalyst without adding an external catalyst, avoiding the deterioration of battery performance caused by the external catalyst; moreover, the prepared solid polymer electrolyte can be depolymerized by heating after use, so as to realize the recycling of polymer monomers and lithium salts in the solid polymer electrolyte, having good environmental and economic benefits.

[0007] The present invention provides an in-situ preparation method of a solid polymer electrolyte, comprising the following steps:

[0008] a) Loading an electrolyte precursor onto the surface of a battery separator, and then assembling the battery separator loaded with the electrolyte precursor, a lithium-ion battery positive electrode, and a lithium-ion battery negative electrode to obtain a semi-finished lithium-ion battery;

[0009] In step a), the components of the electrolyte precursor include a polymer monomer, a lithium salt, and an initiator. The polymer monomer is one or more of cyclic carbonates, lactones, lactides, and cycloalkenone acetals. The lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, bis(malonato)boric acid, lithium malonate oxalate borate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)methyl, and lithium 4,5-dicyano-2-(trifluoromethyl)imidazole. The initiator is one or more of carboxylic acid initiators, alcohol initiators, phenol initiators, and amine initiators;

[0010] b) Under heating conditions, the electrolyte precursor in the semi-finished lithium-ion battery undergoes in-situ polymerization on the battery separator to obtain a solid polymer electrolyte loaded on the battery separator.

[0011] Preferably, the polymer monomer is one or more of trimethylene carbonate, ethylene carbonate, ε-caprolactone, β-butyrolactone, and lactide; the initiator is one or more of terephthalic acid, trimesic acid, terephthalyl alcohol, ditrimethylolpropane pentaerythritol, 1,4-butanediol, and hydroquinone.

[0012] Preferably, the molar ratio of the polymerization monomer, lithium salt and initiator is 300:(20 - 60):(1 - 2).

[0013] Preferably, the heating temperature is 80 - 150 °C; the heating time is 0.5 - 24 h.

[0014] Preferably, the material of the positive electrode of the lithium ion battery is one or more of lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganate and lithium nickel cobaltate materials.

[0015] Preferably, the material of the negative electrode of the lithium ion battery is one or more of lithium, graphite, soft carbon, hard carbon and silicon.

[0016] Preferably, the battery separator is one or more of glass fiber separator, cellulose separator, polyethylene separator and polypropylene separator.

[0017] The present invention provides a method for recycling a solid polymer electrolyte, comprising the following steps:

[0018] Collect the solid polymer electrolyte prepared by the preparation method described in the above technical solution, heat and depolymerize it, separate the products, and recycle the polymerization monomer and / or lithium salt.

[0019] Preferably, the heating and depolymerization temperature is 150 - 200 °C; the heating and depolymerization time is 0.5 - 10 h.

[0020] The present invention provides a lithium ion battery, comprising: a positive electrode of a lithium ion battery, a negative electrode of a lithium ion battery, a battery separator and an electrolyte, and the electrolyte is the solid polymer electrolyte prepared by the preparation method described in the above technical solution.

[0021] Compared with the prior art, the present invention provides an in-situ preparation method of a solid polymer electrolyte, a recycling method thereof, and a lithium-ion battery. The preparation method provided by the present invention comprises the following steps: a) loading an electrolyte precursor onto the surface of a battery separator, and then assembling the battery separator loaded with the electrolyte precursor, a lithium-ion battery positive electrode, and a lithium-ion battery negative electrode to obtain a semi-finished lithium-ion battery; in step a), the components of the electrolyte precursor include a polymerizable monomer, a lithium salt, and an initiator, the polymerizable monomer is one or more of cyclic carbonates, lactones, lactides, and cyclic enone acetals, the lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, bis(malonato)boric acid, lithium malonate oxalate borate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)methyl, and 4,5-dicyano-2-trifluoromethylimidazole lithium, and the initiator is one or more of carboxylic acid initiators, alcohol initiators, phenol initiators, and amine initiators; b) under heating conditions, the electrolyte precursor in the semi-finished lithium-ion battery undergoes in-situ polymerization on the battery separator to obtain a solid polymer electrolyte loaded on the battery separator. The preparation method provided by the present invention does not require an additional catalyst, and the obtained solid polymer electrolyte can be depolymerized by heating, having good environmental and economic benefits.

[0022] More specifically, it has the following technical advantages:

[0023] (1) The existing technical solutions for in-situ polymerization to prepare solid polymer electrolytes require the additional introduction of a catalyst, which may deteriorate the battery performance; while in the present invention, the lithium salt is used as a catalyst, which not only avoids possible adverse side reactions in the battery but also simplifies the electrolyte formulation.

[0024] (2) The polymer electrolyte contains a large amount of high-value electrolyte salts. The existing methods for in-situ polymerization to prepare solid polymer electrolytes are all based on polyolefin or polyether structures, and such polymers are difficult to degrade and separate from the lithium salt. Therefore, after being discarded, such polymer electrolytes can only be landfilled or burned, which not only causes a large waste of high-value electrolyte salts but also may cause environmental pollution; while the polymer electrolyte obtained in the present invention can be depolymerized by heating after use, and through simple separation steps (recrystallization, sublimation, etc.), the high-value lithium salt and some reaction monomers in the electrolyte can be recovered, which not only solves the environmental pollution problem of the polymer electrolyte but also has better economic benefits.

[0025] (3) Most of the solid polymer electrolytes prepared by existing technical solutions rely on cross-linking reactions or cationic polymerization. It is difficult to control the structure and molecular weight of the products, and it is difficult to optimize the battery performance by regulating the polymerization reaction. The present invention can precisely control the molecular weight and chain structure of the polymerization products by adjusting the dosage of the initiator and the number of functional groups in the initiator molecule, and a solid polymer electrolyte with high ionic conductivity can be prepared by optimizing the reaction conditions.

[0026] (4) Limited by the uncontrollability of the polymer structure, the room-temperature ionic conductivity of the all-solid polymer electrolytes prepared by existing technical solutions is relatively low, and the conductivity can only be improved by adding external plasticizers, etc., which makes the formulation more complex. The solid polymer electrolyte obtained by the present invention can precisely control the degree of polymerization reaction by adjusting the heating time and temperature, and use the remaining polymerization monomers as internal plasticizers, simplifying the electrolyte formulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0028] Figure 1 It is the EIS spectrum diagram provided in Embodiment 1 of the present invention;

[0029] Figure 2 It is the 1H NMR spectrum diagram provided in Embodiment 1 of the present invention;

[0030] Figure 3 It is the 7Li NMR spectrum diagram provided in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] The present invention provides an in-situ preparation method for a solid polymer electrolyte, comprising the following steps:

[0033] a) Loading the electrolyte precursor onto the surface of the battery separator, and then assembling the battery separator loaded with the electrolyte precursor, the positive electrode of the lithium-ion battery, and the negative electrode of the lithium-ion battery to obtain a semi-finished lithium-ion battery;

[0034] b) Under heating conditions, the electrolyte precursor in the semi-finished lithium-ion battery undergoes in-situ polymerization on the battery separator to obtain a solid polymer electrolyte loaded on the battery separator.

[0035] In the preparation method provided by the present invention, in step a), the components of the electrolyte precursor include a polymerizable monomer, a lithium salt, and an initiator; wherein, the polymerizable monomer is one or more of cyclic carbonates, lactones, lactides, and cycloalkenone acetals, preferably one or more of trimethylene carbonate, ethylene carbonate, ε-caprolactone, β-butyrolactone, and lactide; the lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, bis(malonato)boric acid, lithium malonate oxalate borate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)methyl, and lithium 4,5-dicyano-2-(trifluoromethyl)imidazole; the initiator is one or more of carboxylic acid initiators, alcohol initiators, phenolic initiators, and amine initiators, preferably one or more of terephthalic acid, trimesic acid, terephthalyl alcohol, ditrimethylolpropane pentaerythritol, 1,4-butanediol, and hydroquinone. In the present invention, the molar ratio of the polymerizable monomer, lithium salt, and initiator is preferably 300:(20 - 60):(1 - 2), wherein the molar ratio of the polymerizable monomer and the lithium salt can specifically be 300:20, 300:25, 300:30, 300:35, 300:40, 300:45, 300:50, 300:55, or 300:60, and the molar ratio of the polymerizable monomer and the initiator is preferably 300:1, 300:1.1, 300:1.2, 300:1.3, 300:1.4, 300:1.5, 300:1.6, 300:1.7, 300:1.8, 300:1.9, or 300:2.

[0036] In the preparation method provided by the present invention, in step a), the electrolyte precursor is preferably loaded onto the surface of the battery separator in a solution state. In the present invention, when the electrolyte precursor is not in a solution state at room temperature, it is preferably heated to a solution state.

[0037] In the preparation method provided by the present invention, in step a), the battery separator is preferably one or more of glass fiber separators, cellulose separators, polyethylene separators, and polypropylene separators.

[0038] In the preparation method provided by the present invention, in step a), the material of the positive electrode of the lithium-ion battery is preferably one or more of lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganate, and lithium nickel cobaltate materials.

[0039] In the preparation method provided by the present invention, in step a), the material of the negative electrode of the lithium-ion battery is preferably one or more of lithium, graphite, soft carbon, hard carbon, and silicon.

[0040] In the preparation method provided by the present invention, in step b), before performing the heating, it is preferably to let the semi-finished lithium-ion battery stand for a period of time to ensure sufficient contact between the electrolyte precursor and the electrode.

[0041] In the preparation method provided by the present invention, in step b), the heating temperature is preferably 80-150 °C, specifically 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C, 135 °C, 140 °C, 145 °C, or 150 °C; the heating time is preferably 0.5-24 h, specifically 0.5 h, 1 h, 1.5 h, 2 h, 3 h, 4 h, 6 h, 8 h, 12 h, 16 h, or 24 h.

[0042] The present invention also provides a method for recycling a solid polymer electrolyte, comprising the following steps:

[0043] Collect the solid polymer electrolyte prepared by the preparation method described in the above technical solution, heat and depolymerize it, separate the products, and recycle to obtain polymer monomers and / or lithium salts.

[0044] In the recycling method provided by the present invention, the heating and depolymerization temperature is preferably 150-200 °C, specifically 150 °C, 155 °C, 160 °C, 165 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 195 °C, or 200 °C; the heating and depolymerization time is preferably 0.5-10 h, specifically 0.5 h, 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 10 h.

[0045] In the recycling method provided by the present invention, the way of separating the products is preferably recrystallization and / or sublimation.

[0046] The present invention also provides a lithium-ion battery, comprising: a positive electrode of a lithium-ion battery, a negative electrode of a lithium-ion battery, a battery separator, and an electrolyte, wherein the electrolyte is a solid polymer electrolyte prepared by the preparation method described in the above technical solution.

[0047] In the lithium-ion battery provided by the present invention, the positive electrode of the lithium-ion battery, the negative electrode of the lithium-ion battery, and the battery separator have been introduced in the in-situ preparation method of the solid polymer electrolyte described above, and will not be elaborated here.

[0048] The technical solution provided by the present invention does not require an additional catalyst during the in-situ preparation of the solid polymer electrolyte, and the obtained solid polymer electrolyte can be depolymerized by heating, having good environmental and economic benefits. More specifically, it has the following technical advantages:

[0049] (1) The existing technical solutions for in-situ polymerization to prepare solid polymer electrolytes need to introduce additional catalysts, which may deteriorate the battery performance; while in the present invention, lithium salts are used as catalysts, which not only avoid possible adverse side reactions in the battery but also simplify the electrolyte formulation.

[0050] (2) The polymer electrolyte contains a large amount of high-value electrolyte salts. The existing in-situ polymerization methods for preparing solid polymer electrolytes are all based on polyolefin or polyether structures. Such polymers are difficult to degrade and separate from the lithium salts. Therefore, after being discarded, such polymer electrolytes can only be landfilled or burned, which not only causes a large waste of high-value electrolyte salts but also may cause environmental pollution; while the polymer electrolyte obtained in the present invention can be depolymerized by heating after use, and through simple separation steps (recrystallization, sublimation, etc.), the high-value lithium salts and some reaction monomers in the electrolyte can be recovered, which not only solves the environmental pollution problem of the polymer electrolyte but also has better economic benefits.

[0051] (3) The solid polymer electrolytes prepared by existing technical solutions mostly rely on cross-linking reactions or cationic polymerization, and the product structure and molecular weight are difficult to control, and it is difficult to optimize the battery performance by regulating the polymerization reaction; the present invention can accurately control the molecular weight and chain structure of the polymerization product by adjusting the dosage of the initiator and the number of functional groups in the initiator molecule, and a solid polymer electrolyte with high ionic conductivity can be prepared by optimizing the reaction conditions.

[0052] (4) Limited by the uncontrollability of the polymer structure, the room-temperature ionic conductivity of the all-solid polymer electrolytes prepared by existing technical solutions is relatively low, and the conductivity can only be improved by adding external plasticizers, etc., which makes the formulation more complex; while the solid polymer electrolyte obtained in the present invention can accurately control the degree of polymerization reaction by adjusting the heating time and temperature, and make the remaining polymerization monomers act as internal plasticizers, simplifying the electrolyte formulation.

[0053] For the sake of clarity, the following will be described in detail through the following examples.

[0054] Example 1

[0055] (1) Prepare the polymer electrolyte precursor solution:

[0056] Weigh 1.0 g of trimethylene carbonate as the polymerization monomer, 281.2 mg of lithium bis(trifluoromethanesulfonyl)imide as the catalyst and lithium source, and 4.5 mg of terephthalyl alcohol as the initiator separately in an argon glove box, and mix them evenly at 45 °C to obtain the polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator] = 300 / 30 / 1, molar ratio, the same below).

[0057] (2) Preparation of a solid-state battery by in-situ polymerization:

[0058] Assemble a lithium-ion button battery in an argon glove box. The positive electrode is a commercially purchased lithium nickel cobalt manganese oxide electrode sheet, the negative electrode is a commercially purchased graphite electrode sheet, and the separator is a commercially purchased glass fiber separator; drop 100 μL of the above polymer electrolyte precursor solution onto the glass fiber separator, assemble the button battery, then let it stand in the glove box for 2 h to ensure that the electrolyte fully infiltrates the electrode material, and then place it in an oven at 110 °C for 1 h for in-situ polymerization to form a lithium-ion button battery with a solid polymer electrolyte. The prepared lithium-ion button battery is subjected to a constant current charge-discharge test at 0.2 C at room temperature. After 50 cycles, the capacity retention rate is 95.0%, and the capacity retention rate at a 1 C rate is 89.6%; the ionic conductivity of the solid polymer electrolyte prepared by the above method is tested. The result is that the ionic conductivity at room temperature (25 °C) is 1.2 mS / cm, and its EIS spectrum is as follows Figure 1 .

[0059] (3) Depolymerization and recovery of high-value lithium salt:

[0060] Collect the solid polymer electrolyte prepared above in a reaction tube, heat it in an oil bath at 180 °C for 1 h, add diethyl ether to the depolymerization product for recrystallization, and obtain trimethylene carbonate crystals in the lower layer. Its 1H NMR spectrum is as follows Figure 2 , and the recovery rate is 85%. After drying the upper diethyl ether solution, lithium bis(trifluoromethanesulfonyl)imide is obtained, and the recovery rate is 96%. Its 7Li NMR spectrum is as follows Figure 3 .

[0061] Example 2

[0062] (1) Preparation of a polymer electrolyte precursor solution:

[0063] Weigh 1.0 g of trimethylene carbonate as the polymerization monomer, 182.0 mg of lithium hexafluoroarsenate as the catalyst and lithium source, and 16.6 mg of dipentaerythritol as the initiator separately in an argon glove box, and mix them evenly at 45 °C to obtain the polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator] = 300 / 30 / 2).

[0064] (2) Preparation of a solid-state battery by in-situ polymerization:

[0065] Assemble a lithium-ion button battery inside an argon glove box. The positive electrode is a commercially purchased lithium iron manganese phosphate electrode sheet, the negative electrode is a commercially purchased graphite electrode sheet, and the separator is a commercially purchased cellulose separator. Drop 100 μL of the above polymer electrolyte precursor solution onto the cellulose separator, assemble the button battery, and then let it stand in the glove box for 2 h to ensure that the electrolyte fully infiltrates the electrode materials. Subsequently, place it in an oven at 110 °C and keep it warm for 2 h for in-situ polymerization to form a lithium-ion button battery with a solid polymer electrolyte. Perform a 0.2C constant current charge-discharge test on the prepared lithium-ion button battery at room temperature. After 50 cycles, the capacity retention rate is 92.8%, and the capacity retention rate at a 1C rate is 88.2%. Test the ionic conductivity of the solid polymer electrolyte prepared by the above method, and the result is an ionic conductivity of 0.95 mS / cm at room temperature.

[0066] (3) Depolymerize and recycle high-value lithium salts:

[0067] Collect the solid polymer electrolyte prepared above in a reaction tube, heat it in an oil bath at 180 °C for 1 h, add diethyl ether to the depolymerization product for recrystallization. Trimethylene carbonate crystals are obtained in the lower layer with a recovery rate of 86%, and lithium hexafluorophosphate is obtained after drying the upper diethyl ether solution with a recovery rate of 96%.

[0068] Example 3

[0069] (1) Prepare a polymer electrolyte precursor solution:

[0070] Weigh 1.0 g of ε-caprolactone as a polymerization monomer, 266.2 mg of lithium hexafluorophosphate as a catalyst and lithium source, and 4.9 mg of terephthalic acid as an initiator inside an argon glove box, and mix them evenly to obtain a polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator] = 300 / 60 / 1).

[0071] (2) Prepare a solid-state battery by in-situ polymerization:

[0072] Assemble a lithium-ion button battery inside an argon glove box. The positive electrode is a commercially purchased lithium iron phosphate electrode sheet, the negative electrode is a commercially purchased graphite electrode sheet, and the separator is a commercially purchased polypropylene separator. Drop 100 μL of the above polymer electrolyte precursor solution onto the polypropylene separator, assemble the button battery, and then let it stand in the glove box for 2 h to ensure that the electrolyte fully infiltrates the electrode materials. Subsequently, place it in an oven at 100 °C and keep it warm for 1 h for in-situ polymerization to form a lithium-ion button battery with a solid polymer electrolyte. Perform a 0.2C constant current charge-discharge test on the prepared lithium-ion button battery at room temperature. After 50 cycles, the capacity retention rate is 91.3%, and the capacity retention rate at a 1C rate is 84.9%. Test the ionic conductivity of the solid polymer electrolyte prepared by the above method, and the result is an ionic conductivity of 1.1 mS / cm at room temperature.

[0073] (3) Depolymerize and recycle high-value lithium salts:

[0074] Collect the solid polymer electrolyte prepared above in a reaction tube, connect a cold trap, heat it in an oil bath at 150 °C for 1 h under vacuum conditions, ε-caprolactone is collected in the cold trap, and the recovery rate is 93%. The remaining solid is recrystallized in diethyl ether to obtain lithium hexafluorophosphate, and the recovery rate is 92%.

[0075] Example 4

[0076] (1) Prepare a polymer electrolyte precursor solution:

[0077] Weigh 1.0 g of lactide as a polymerization monomer, 49.2 mg of lithium perchlorate as a catalyst and lithium source, and 5.1 mg of hydroquinone as an initiator in an argon glove box, and mix them evenly at 95 °C to obtain a polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator] = 300 / 20 / 2).

[0078] (2) In-situ polymerization to prepare a solid-state battery:

[0079] Assemble a lithium metal button battery in an argon glove box. The positive electrode is a commercially purchased lithium cobalt oxide electrode sheet, the negative electrode is a commercially purchased lithium sheet, and the separator is a commercially purchased polypropylene separator; drop 100 μL of the above polymer electrolyte precursor solution onto the polypropylene separator, assemble the button battery, then let it stand in the glove box for 2 h to ensure that the electrolyte and the electrode material are fully infiltrated, and then place it in an oven at 120 °C for heat preservation for 0.5 h for in-situ polymerization to form a battery with a solid polymer electrolyte. The prepared lithium-ion button battery is subjected to a constant current charge-discharge test at 0.2 C at room temperature. After 50 cycles, the capacity retention rate is 79.6%, and the capacity retention rate at a 1 C rate is 74%; the ionic conductivity of the solid polymer electrolyte prepared by the above method is tested, and the result is an ionic conductivity of 0.76 mS / cm at room temperature.

[0080] (3) Depolymerize and recycle high-value lithium salts:

[0081] Collect the solid polymer electrolyte prepared above in a reaction tube, heat it in an oil bath at 170 °C for 1 h, add diethyl ether to the depolymerization product for recrystallization, the lower layer obtains lactide, and the recovery rate is 85%. The upper layer of the diethyl ether solution is dried to obtain lithium hexafluorophosphate lithium perchlorate, and the recovery rate is 89%.

[0082] Example 5

[0083] (1) Prepare a polymer electrolyte precursor solution:

[0084] Weigh 1.0 g of ethylene carbonate as the polymerization monomer, 177.4 mg of lithium tetrafluoroborate as the catalyst and lithium source, and 8.0 mg of trimesic acid as the initiator in an argon glove box, and mix them evenly to obtain the polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator] = 300 / 50 / 1).

[0085] (2) Preparation of solid-state battery by in-situ polymerization:

[0086] Assemble a lithium metal button battery in an argon glove box. The positive electrode is a commercially purchased lithium nickelate electrode sheet, the negative electrode is a commercially purchased lithium sheet, and the separator is a commercially purchased polyethylene separator; drop 100 μL of the above polymer electrolyte precursor solution onto the polyethylene separator, assemble the button battery, and then let it stand in the glove box for 2 h to ensure that the electrolyte fully infiltrates the electrode material. Subsequently, place it in an oven at 150 °C and keep it warm for 1 h for in-situ polymerization to form a battery with a solid polymer electrolyte. The prepared lithium-ion button battery is subjected to a constant current charge-discharge test at 0.1 C at room temperature. After 50 cycles, the capacity retention rate is 90.6%, and the capacity retention rate at 1 C is 86.5%; the ionic conductivity of the solid polymer electrolyte prepared by the above method is tested, and the result is an ionic conductivity of 0.88 mS / cm at room temperature.

[0087] (3) Depolymerization to recover high-value lithium salt:

[0088] Collect the solid polymer electrolyte prepared above in a reaction tube, connect a cold trap, and heat it in an oil bath at 200 °C under vacuum for 1 h. Ethylene carbonate is collected in the cold trap, and the recovery rate is 94%. The remaining solid is recrystallized in diethyl ether to obtain lithium tetrafluoroborate, and the recovery rate is 95%.

[0089] Example 6

[0090] (1) Preparation of polymer electrolyte precursor solution:

[0091] Weigh 1.0 g of β-butyrolactone as the polymerization monomer, 181.2 mg of lithium trifluoromethanesulfonate as the catalyst and lithium source, and 3.5 mg of 1,4-butanediol as the initiator in an argon glove box, and mix them evenly to obtain the polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator] = 300 / 30 / 1).

[0092] (2) Preparation of solid-state battery by in-situ polymerization:

[0093] Assemble the lithium metal button battery inside an argon glove box. The positive electrode is a commercially purchased lithium manganese oxide electrode sheet, the negative electrode is a commercially purchased metallic lithium electrode sheet, and the separator is a commercially purchased glass fiber separator. Drop 100 μL of the above polymer electrolyte precursor solution onto the glass fiber separator, assemble the button battery, and then let it stand in the glove box for 2 h to ensure that the electrolyte fully infiltrates the electrode materials. Subsequently, place it in an oven at 100 °C and keep it warm for 2 h for in-situ polymerization to form a lithium-ion button battery with a solid polymer electrolyte. Perform a constant current charge-discharge test on the prepared lithium-ion button battery at 0.2C at room temperature. After x cycles, the capacity retention rate is 81.6%, and the capacity retention rate at 1C is 76%. Test the ionic conductivity of the solid polymer electrolyte prepared by the above method, and the result is an ionic conductivity of 0.61 mS / cm at room temperature.

[0094] (3) Depolymerize and recycle high-value lithium salts:

[0095] Collect the solid polymer electrolyte prepared above in a reaction tube, connect a cold trap, heat it in an oil bath at 170 °C under vacuum conditions for 3 h, and collect β-butyrolactone in the cold trap with a recovery rate of 74%. Recrystallize the remaining solid in diethyl ether to obtain lithium trifluoromethanesulfonate with a recovery rate of 81%.

[0096] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for recovering a solid polymer electrolyte, characterized in that: The following steps are involved: Collecting the solid polymer electrolyte, heating and depolymerizing it, separating the product, and recovering the polymerized monomer and / or lithium salt; The temperature of the heating depolymerization is 150-200°C; the time of the heating depolymerization is 0.5-10h; The solid polymer electrolyte is prepared according to the following steps: a) loading an electrolyte precursor onto the surface of a battery separator, and then assembling the battery separator loaded with the electrolyte precursor, a lithium-ion battery positive electrode, and a lithium-ion battery negative electrode to obtain a lithium-ion battery semi-finished product; In step a), the components of the electrolyte precursor include a polymerizable monomer, a lithium salt and an initiator, the polymerizable monomer is one or more of a cyclic carbonate, a lactone, a lactide and a cycloenone acetal, the lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bismalonateborate, lithium malonateoxalatoborate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bistrifluoromethanesulfonyl imide, lithium bistrifluoromethanesulfonylmethyl and lithium 4,5-dicyano-2-trifluoromethylimidazole, and the initiator is one or more of a carboxylic acid initiator, an alcohol initiator, a phenol initiator and an amine initiator; b) Under heating conditions, the electrolyte precursor in the lithium-ion battery semi-finished product is polymerized in situ on the battery separator to obtain a solid polymer electrolyte supported on the battery separator.

2. The recycling method according to claim 1, characterized in that: The polymerization monomer is one or more of trimethylene carbonate, ethylene carbonate, ε-caprolactone, β-butyrolactone and lactide; the initiator is one or more of terephthalic acid, trimesic acid, terephthalic acid, dipentaerythritol, 1,4-butanediol and hydroquinone.

3. The recycling method according to claim 1, characterized in that: The molar ratio of the polymerization monomer, the lithium salt and the initiator is 300:(20-60):(1-2).

4. The recycling method according to claim 1, characterized in that: In step b), the heating temperature is 80 to 150° C. and the heating time is 0.5 to 24 hours.

5. The recycling method according to claim 1, characterized in that: The material of the positive electrode of the lithium-ion battery is one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide and lithium nickel cobalt oxide.

6. The recycling method according to claim 1, characterized in that: The material of the negative electrode of the lithium-ion battery is one or more of lithium, graphite, soft carbon, hard carbon and silicon.

7. The recycling method according to claim 1, characterized in that: The battery separator is one or more of a glass fiber separator, a cellulose separator, a polyethylene separator and a polypropylene separator.

Images