In-situ preparation method and recovery method for solid polymer electrolyte, and lithium ion battery

Abstract

The present invention belongs to the field of lithium ion batteries, and specifically relates to an in-situ preparation method and a recovery method for a solid polymer electrolyte, as well as a lithium ion battery. The preparation method provided by the present invention comprises the following steps: a) loading an electrolyte precursor onto a surface of a battery separator, and then assembling same with a lithium ion battery positive electrode and a lithium ion battery negative electrode, to obtain a semi-finished lithium ion battery product, components of the electrolyte precursor in step a) comprising a polymer monomer, a lithium salt and an initiator, the lithium salt being lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, or the like; b) under heating conditions, performing in-situ polymerization of the electrolyte precursor on the battery separator in the semi-finished lithium ion battery product, 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 prepared solid polymer electrolyte can be depolymerized by means of heating, and has good environmental and economic benefits.

Description

In-situ preparation method of solid polymer electrolyte and recovery method thereof and lithium ion battery

[0001] This application claims priority to a Chinese patent application filed with the Patent Office of China on January 8, 2024, with application number 202410023888.4 and invention name “A method for in-situ preparation of a solid polymer electrolyte, its recovery method and lithium-ion battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention belongs to the field of lithium ion batteries, and in particular relates to an in-situ preparation method of a solid polymer electrolyte, a recovery method thereof, and a lithium ion battery. Background Art

[0003] Since its development, lithium-ion batteries have been widely used in various fields such as new energy vehicles, consumer electronics, and energy storage. Lithium batteries have high energy density and long cycle life. The energy density can reach 100-200Wh / kg, and the cycle life is greater than 1,000 times, which is much higher than other secondary batteries. They are currently the object of vigorous development. Currently, most of the commercialized lithium-ion batteries on the market are liquid lithium-ion batteries, in which the electrolyte used is a low-boiling point and flammable organic liquid such as carbonate and ether. If this type of liquid battery has an internal short circuit and a large amount of heat is released, it is very easy to cause a safety accident such as battery combustion or even explosion. Compared with traditional electrolyte lithium-ion batteries, solid-state polymer batteries are safer, have better mechanical properties, and are more processable. At the same time, high-energy-density electrode materials such as metallic lithium can be used to further increase the battery's energy density. Therefore, solid-state polymer batteries have very broad application prospects.

[0004] Compared with liquid electrolyte 10 -2 ~10 -3 S cm -1 The development of solid polymer electrolytes is limited by their low ionic conductivity (usually below 10 -5 ~10 -6 S cm -1 ). Due to its low ionic conductivity, solid-state polymer batteries are difficult to use at room temperature and difficult to implement fast charging technology. Moreover, due to the large internal resistance of solid-state polymer batteries, irreversible energy loss will occur during the charging process, resulting in a decrease in capacity. In addition, the preparation process of solid-state polymer batteries is complicated, and solid polymer electrolytes need to be prepared in advance, and then assembled with the positive and negative electrodes of the battery in a winding or stacked manner. The interface compatibility between the electrodes and the solid electrolyte in the all-solid-state battery obtained by this ex situ preparation method is poor, resulting in a very large interface impedance, which seriously affects the power density of the battery, and the preparation process is complicated and the cost is high.

[0005] To address these issues with ex situ solid polymer electrolyte preparation, researchers are continuously developing systems for preparing solid polymer electrolytes through in situ polymerization directly on battery components. However, existing in situ polymerization techniques generally require the introduction of additional catalysts, which can deteriorate battery performance.

[0006] Furthermore, as the market share of lithium-ion batteries continues to expand, the problem of post-use battery disposal is gradually emerging. Common solid polymer electrolytes are based on polyolefin or polyether structures. Because these polymers are difficult to degrade and separate from lithium salts, solid polymer electrolytes are currently commonly disposed of by landfill or incineration. This not only results in the waste of large amounts of high-value electrolyte salts, but also poses a risk of environmental pollution. Summary of the Invention

[0007] In view of this, the object of the present invention is to provide an in-situ preparation method of a solid polymer electrolyte, a recovery method thereof, and a lithium-ion battery. The preparation method provided by the present invention uses an electrolyte salt as a catalyst and does not require an external catalyst, thereby avoiding the deterioration of battery performance caused by the external catalyst; moreover, the prepared solid polymer electrolyte can be depolymerized by heating after use, thereby realizing the recovery and utilization of the polymerized monomers and lithium salts in the solid polymer electrolyte, which has good environmental and economic benefits.

[0008] The present invention provides an in-situ preparation method of a solid polymer electrolyte, comprising the following steps:

[0009] 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;

[0010] In step a), the components of the electrolyte precursor include a polymeric monomer, a lithium salt and an initiator, the polymeric monomer is one or more of a cyclic carbonate, a lactone, a lactide and a cycloketene acetal, the lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate, bismalonate borate, lithium malonate oxalatoborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(trifluoromethanesulfonylmethyl) 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;

[0011] b) Under heating conditions, the electrolyte precursor in the lithium-ion battery semi-finished product is in-situ polymerized on the battery separator to obtain a solid polymer electrolyte supported on the battery separator.

[0012] Preferably, 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.

[0013] Preferably, the molar ratio of the polymerizable monomer, the lithium salt and the initiator is 300:(20-60):(1-2).

[0014] Preferably, the heating temperature is 80-150° C.; and the heating time is 0.5-24 h.

[0015] Preferably, 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.

[0016] 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.

[0017] Preferably, the battery separator is one or more of a glass fiber separator, a cellulose separator, a polyethylene separator and a polypropylene separator.

[0018] The present invention provides a method for recovering a solid polymer electrolyte, comprising the following steps:

[0019] The solid polymer electrolyte prepared by the preparation method described in the above technical solution is collected, heated for depolymerization, and the product is separated and recovered to obtain the polymerized monomer and / or lithium salt.

[0020] Preferably, the temperature of the heating depolymerization is 150-200° C.; and the time of the heating depolymerization is 0.5-10 h.

[0021] The present invention provides a lithium ion battery comprising: a lithium ion battery positive electrode, a lithium ion battery negative electrode, 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.

[0022] Compared with the prior art, the present invention provides an in-situ preparation method of a solid polymer electrolyte, a recovery 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 polymer monomer, a lithium salt, and an initiator, the polymer monomer is one or more of cyclic carbonate, lactone, lactide, and cycloenone acetal, and the lithium salt is lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(oxalatoborate), or difluorooxalatoborate. One or more of lithium, lithium tetrafluoroborate, bismalonic acid boric acid, lithium malonate oxalate borate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, bistrifluoromethanesulfonylmethyl lithium and 4,5-dicyano-2-trifluoromethylimidazole lithium, 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 lithium ion battery semi-finished product is in situ polymerized 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, which has good environmental and economic benefits. More specifically, it has the following technical advantages:

[0023] (1) The existing technical solution for preparing solid polymer electrolytes by in situ polymerization requires the additional introduction of catalysts, which may deteriorate battery performance. However, the present invention uses lithium salt 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 solid polymer electrolytes prepared by in situ polymerization are all based on polyolefin or polyether structures. These polymers are difficult to degrade and difficult to separate from lithium salts. Therefore, these polymer electrolytes can only be landfilled or burned after being discarded, which not only causes a large amount of waste of high-value electrolyte salts, but also may cause environmental pollution. The polymer electrolyte obtained by the present invention can be depolymerized by heating after use, and then the high-value lithium salts and some reaction monomers in the electrolyte can be recovered through simple separation steps (recrystallization, sublimation, etc.). This not only solves the problem of polymer electrolyte pollution to the environment, but also has more economic benefits.

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

[0026] (4) Due to the uncontrollability of the polymer structure, the room temperature ionic conductivity of the all-solid-state polymer electrolyte prepared by the existing technical solution is low, and the conductivity can only be improved by adding plasticizers, which makes the formula more complicated; while the solid-state polymer electrolyte obtained by the present invention can precisely control the degree of polymerization reaction by adjusting the heating time and temperature, so that the remaining polymerized monomers can be used as internal plasticizers, simplifying the electrolyte formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0028] FIG1 is an EIS spectrum provided in Example 1 of the present invention;

[0029] FIG2 is a hydrogen nuclear magnetic spectrum provided in Example 1 of the present invention;

[0030] FIG3 is a NMR lithium spectrum diagram provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

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

[0033] 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;

[0034] b) Under heating conditions, the electrolyte precursor in the lithium-ion battery semi-finished product is in-situ polymerized on the battery separator to obtain a solid polymer electrolyte supported 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 polymer monomer, a lithium salt and an initiator; wherein the polymer monomer is one or more of cyclic carbonate, lactone, lactide and cycloketone acetal, preferably one or more of trimethylene carbonate, ethylene carbonate, ε-caprolactone, β-butyrolactone and lactide; the lithium salt is lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate, One or more of bismalonate boric acid, lithium malonate oxalate borate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium bistrifluoromethanesulfonylmethyl and lithium 4,5-dicyano-2-trifluoromethylimidazole; the initiator is one or more of carboxylic acid initiators, alcohol initiators, phenol initiators and amine initiators, preferably one or more of terephthalic acid, trimesic acid, terephthalic acid methanol, dipentaerythritol, 1,4-butanediol and hydroquinone. In the present invention, the molar ratio of the polymerized monomer, the lithium salt and the initiator is preferably 300:(20-60):(1-2), wherein the molar ratio of the polymerized monomer and the lithium salt may be specifically 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 polymerized 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 the form of a solution. In the present invention, when the electrolyte precursor is not in a solution 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 a glass fiber separator, a cellulose separator, a polyethylene separator and a polypropylene separator.

[0038] In the preparation method provided by the present invention, in step a), the material of the lithium-ion battery positive electrode is preferably 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.

[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 the heating, the lithium ion battery semi-finished product is preferably allowed to stand for a period of time to ensure that the electrolyte precursor is in full contact with 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 0.5-24h, specifically 0.5h, 1h, 1.5h, 2h, 3h, 4h, 6h, 8h, 12h, 16h or 24h.

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

[0043] The solid polymer electrolyte prepared by the preparation method described in the above technical solution is collected, heated for depolymerization, and the product is separated and recovered to obtain the polymerized monomer and / or lithium salt.

[0044] In the recovery method provided by the present invention, the temperature of the heating depolymerization 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 time of the heating depolymerization is preferably 0.5-10h, specifically 0.5h, 1h, 1.5h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0045] In the recovery method provided by the present invention, the product separation method is preferably recrystallization and / or sublimation.

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

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

[0048] The technical solution provided by the present invention eliminates the need for an external catalyst during the in-situ preparation of a solid polymer electrolyte, and the resulting solid polymer electrolyte can be depolymerized by heating, resulting in favorable environmental and economic benefits. More specifically, the technical advantages are as follows:

[0049] (1) The existing technical solution for preparing solid polymer electrolytes by in situ polymerization requires the additional introduction of catalysts, which may deteriorate battery performance. However, the present invention uses lithium salt as a catalyst, which not only avoids possible adverse side reactions in the battery but also simplifies the electrolyte formulation.

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

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

[0052] (4) Due to the uncontrollability of the polymer structure, the room temperature ionic conductivity of the all-solid-state polymer electrolyte prepared by the existing technical solution is low, and the conductivity can only be improved by adding plasticizers, which makes the formula more complicated; while the solid-state polymer electrolyte obtained by the present invention can precisely control the degree of polymerization reaction by adjusting the heating time and temperature, so that the remaining polymerized monomers can be used as internal plasticizers, simplifying the electrolyte formula.

[0053] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples.

[0054] Example 1

[0055] (1) Preparation of polymer electrolyte precursor solution:

[0056] In an argon glove box, 1.0 g of trimethylene carbonate as a polymerization monomer, 281.2 mg of lithium bis(trifluoromethanesulfonyl)imide as a catalyst and lithium source, and 4.5 mg of p-phenylenediol as an initiator were weighed and mixed at 45°C to obtain a polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator]=300 / 30 / 1, molar ratio, the same below).

[0057] (2) In-situ polymerization to prepare solid-state batteries:

[0058] A lithium-ion button cell was assembled in an argon glove box. The positive electrode was a commercially purchased lithium nickel cobalt manganese oxide electrode, the negative electrode was a commercially purchased graphite electrode, and the separator was a commercially purchased glass fiber separator. 100 μL of the polymer electrolyte precursor solution was dropwise added to the glass fiber separator to assemble the button cell. The cell was then allowed to stand in the glove box for 2 hours to ensure sufficient infiltration of the electrolyte and electrode materials. The cell was then placed in a 110°C oven for 1 hour to allow in-situ polymerization to occur, forming a lithium-ion button cell with a solid polymer electrolyte. The resulting lithium-ion button cell was subjected to a 0.2C constant current charge-discharge test at room temperature. After 50 cycles, the capacity retention rate was 95.0%, and the capacity retention rate at a 1C rate was 89.6%. The ionic conductivity of the solid polymer electrolyte prepared using the above method was tested, and the result was an ionic conductivity of 1.2 mS / cm at room temperature (25°C). Its EIS spectrum is shown in Figure 1.

[0059] (3) Depolymerization to recover high-value lithium salts:

[0060] The solid polymer electrolyte prepared above was collected in a reaction tube and heated in an oil bath at 180°C for 1 hour. Ether was added to the depolymerized product for recrystallization. Trimethylene carbonate crystals were obtained in the lower layer. Its H NMR spectrum is shown in Figure 2 below, and the recovery rate was 85%. The upper ether solution was dried to obtain lithium bis(trifluoromethanesulfonyl)imide. The recovery rate was 96%, and its lithium NMR spectrum is shown in Figure 3 below.

[0061] Example 2

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

[0063] In an argon glove box, 1.0 g of trimethylene carbonate as a polymerization monomer, 182.0 mg of lithium hexafluoroarsenate as a catalyst and lithium source, and 16.6 mg of dipentaerythritol as an initiator were weighed and mixed at 45° C. to obtain a polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator]=300 / 30 / 2).

[0064] (2) In-situ polymerization to prepare solid-state batteries:

[0065] A lithium-ion button cell was assembled in an argon glove box. The positive electrode was a commercially purchased lithium iron manganese phosphate electrode, the negative electrode was a commercially purchased graphite electrode, and the separator was a commercially purchased cellulose membrane. 100 μL of the polymer electrolyte precursor solution was dropwise added to the cellulose membrane to assemble the button cell. The cell was then allowed to stand in the glove box for 2 hours to ensure sufficient infiltration of the electrolyte and electrode materials. The cell was then placed in a 110°C oven for 2 hours to allow in-situ polymerization to occur, forming a lithium-ion button cell with a solid polymer electrolyte. The resulting lithium-ion button cell was subjected to 0.2C constant current charge-discharge testing at room temperature. After 50 cycles, the capacity retention rate was 92.8%, and the capacity retention rate at 1C was 88.2%. The ionic conductivity of the solid polymer electrolyte prepared using this method was also tested, and the result was a room temperature ionic conductivity of 0.95 mS / cm.

[0066] (3) Depolymerization to recover high-value lithium salts:

[0067] The solid polymer electrolyte prepared above was collected in a reaction tube and heated in an oil bath at 180°C for 1 hour. Ether was added to the depolymerized product for recrystallization. Trimethylene carbonate crystals were obtained in the lower layer with a recovery rate of 86%. Lithium hexafluorophosphate was obtained after drying the upper ether solution with a recovery rate of 96%.

[0068] Example 3

[0069] (1) Preparation of polymer electrolyte precursor solution:

[0070] In an argon glove box, 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 were weighed and mixed uniformly to obtain a polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator]=300 / 60 / 1).

[0071] (2) In-situ polymerization to prepare solid-state batteries:

[0072] Lithium-ion button cells were assembled in an argon glove box, using a commercially available lithium iron phosphate cathode, a commercially available graphite cathode, and a commercially available polypropylene separator. 100 μL of the polymer electrolyte precursor solution was dropwise added to the polypropylene separator, and the cell was then allowed to stand in the glove box for 2 hours to ensure sufficient infiltration of the electrolyte and electrode materials. The cell was then placed in a 100°C oven for 1 hour to allow in-situ polymerization, forming a lithium-ion button cell with a solid polymer electrolyte. The resulting cell was subjected to 0.2C constant current charge-discharge testing at room temperature, demonstrating a capacity retention of 91.3% after 50 cycles and 84.9% at a 1C rate. The ionic conductivity of the solid polymer electrolyte prepared using this method was also tested, revealing a room-temperature ionic conductivity of 1.1 mS / cm.

[0073] (3) Depolymerization to recover high-value lithium salts:

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

[0075] Example 4

[0076] (1) Preparation of polymer electrolyte precursor solution:

[0077] In an argon glove box, 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 were weighed and mixed at 95° C. to obtain a polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator]=300 / 20 / 2).

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

[0079] Lithium metal coin cells were assembled in an argon glove box, using a commercially purchased lithium cobalt oxide cathode, a commercially purchased lithium sheet as the negative electrode, and a commercially purchased polypropylene separator as the separator. 100 μL of the polymer electrolyte precursor solution was dropwise added to the polypropylene separator, and the coin cell was then allowed to stand in the glove box for 2 hours to ensure sufficient infiltration of the electrolyte and electrode materials. The cell was then placed in a 120°C oven for 0.5 hours to allow in-situ polymerization, forming a battery containing a solid polymer electrolyte. The resulting lithium-ion coin cell was subjected to 0.2C constant current charge-discharge testing at room temperature, demonstrating a capacity retention of 79.6% after 50 cycles and a capacity retention of 74% at a 1C rate. The ionic conductivity of the solid polymer electrolyte prepared using this method was also tested, revealing a room-temperature ionic conductivity of 0.76 mS / cm.

[0080] (3) Depolymerization to recover high-value lithium salts:

[0081] The solid polymer electrolyte prepared above was collected in a reaction tube and heated in an oil bath at 170°C for 1 hour. Ether was added to the depolymerized product for recrystallization. Lactide was obtained in the lower layer with a recovery rate of 85%. Lithium hexafluorophosphate and lithium perchlorate were obtained after drying the upper ether solution with a recovery rate of 89%.

[0082] Example 5

[0083] (1) Preparation of polymer electrolyte precursor solution:

[0084] In an argon glove box, 1.0 g of ethylene carbonate as a polymerization monomer, 177.4 mg of lithium tetrafluoroborate as a catalyst and lithium source, and 8.0 mg of trimesic acid as an initiator were weighed and mixed uniformly to obtain a polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator]=300 / 50 / 1).

[0085] (2) In-situ polymerization to prepare solid-state batteries:

[0086] Lithium metal coin cells were assembled in an argon glove box, using a commercially available lithium nickelate cathode, a commercially available lithium sheet as the negative electrode, and a commercially available polyethylene separator as the separator. 100 μL of the polymer electrolyte precursor solution was dropwise added to the polyethylene separator, and the coin cell was then allowed to stand in the glove box for 2 hours to ensure sufficient infiltration of the electrolyte and electrode materials. The cell was then placed in a 150°C oven for 1 hour to allow in-situ polymerization, forming a battery containing a solid polymer electrolyte. The resulting lithium-ion coin cell was subjected to 0.1C constant current charge-discharge testing at room temperature. After 50 cycles, the capacity retention rate was 90.6%, and the capacity retention rate at 1C was 86.5%. The ionic conductivity of the solid polymer electrolyte prepared using this method was also tested, revealing a room temperature ionic conductivity of 0.88 mS / cm.

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

[0088] The solid polymer electrolyte prepared above was collected in a reaction tube, connected to a cold trap, and heated in an oil bath at 200°C under vacuum conditions for 1 hour. Ethylene carbonate was collected in the cold trap with a recovery rate of 94%. The remaining solid was recrystallized in ether to obtain lithium tetrafluoroborate with a recovery rate of 95%.

[0089] Example 6

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

[0091] In an argon glove box, 1.0 g of β-butyrolactone as a polymerization monomer, 181.2 mg of lithium trifluoromethanesulfonate as a catalyst and lithium source, and 3.5 mg of 1,4-butanediol as an initiator were weighed and mixed uniformly to prepare a polymer electrolyte precursor solution ([monomer] / [lithium salt] / [initiator]=300 / 30 / 1).

[0092] (2) In-situ polymerization to prepare solid-state batteries:

[0093] A lithium metal coin cell was assembled in an argon glove box, using a commercially available lithium manganese oxide cathode and a commercially available lithium metal cathode as the negative electrode. A commercially available glass fiber separator was used as the separator. 100 μL of the polymer electrolyte precursor solution was dropwise added to the glass fiber separator, and the coin cell was then allowed to stand in the glove box for 2 hours to ensure sufficient infiltration of the electrolyte and electrode materials. The cell was then placed in a 100°C oven for 2 hours for in-situ polymerization, forming a lithium-ion coin cell with a solid polymer electrolyte. The resulting lithium-ion coin cell was subjected to 0.2C constant current charge-discharge testing at room temperature. After x cycles, the capacity retention rate was 81.6%, and the capacity retention rate at 1C was 76%. The ionic conductivity of the solid polymer electrolyte prepared using this method was also tested, revealing a room temperature ionic conductivity of 0.61 mS / cm.

[0094] (3) Depolymerization to recover high-value lithium salts:

[0095] The solid polymer electrolyte prepared above was collected in a reaction tube, connected to a cold trap, and heated in an oil bath at 170°C for 3 h under vacuum conditions. β-Butyrolactone was collected in the cold trap with a recovery rate of 74%. The remaining solid was recrystallized from ether to obtain lithium trifluoromethanesulfonate with a recovery rate of 81%.

[0096] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An in-situ preparation method of a solid polymer electrolyte, characterized in that, It includes the following steps: a) Load the electrolyte precursor onto the surface of the battery separator, and then assemble the battery separator loaded with the electrolyte precursor, the lithium-ion battery positive electrode, and the 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-(trifluoromethyl)imidazole lithium. 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.

2. The in-situ preparation method according to claim 1, wherein The polymerizable 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, dipentaerythritol, 1,4-butanediol, and hydroquinone.

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

4. The in-situ preparation method according to claim 1, characterized in that, The heating temperature is 80 - 150 °C; the heating time is 0.5 - 24 h.

5. The in-situ preparation method according to claim 1, wherein, The material of the lithium-ion battery positive electrode 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.

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

7. The in-situ preparation method according to claim 1, characterized in that, The battery separator is one or more of glass fiber separators, cellulose separators, polyethylene separators, and polypropylene separators.

8. A method for recycling a solid polymer electrolyte, characterized in that, It includes the following steps: Collect the solid polymer electrolyte prepared by the preparation method according to any one of claims 1 - 7, heat and depolymerize it, separate the products, and recycle to obtain the polymerizable monomer and / or the lithium salt.

9. The recovery method according to claim 8, wherein The heating and depolymerization temperature is 150 - 200 °C; the heating and depolymerization time is 0.5 - 10 h.

10. A lithium-ion battery, comprising: A lithium-ion battery positive electrode, a lithium-ion battery negative electrode, a battery separator, and an electrolyte, wherein the electrolyte is a solid polymer electrolyte prepared by the preparation method according to any one of claims 1 - 7.

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