Modified polyion liquid-based solid electrolyte, preparation method thereof and secondary battery

Abstract

The invention provides a modified polyion liquid-based solid electrolyte, a preparation method thereof and a secondary battery. The modified polyion liquid-based solid electrolyte comprises an electrolyte salt and a modified polyion liquid, the main chain of the modified polyion liquid is a carbon-carbon alkyl chain, and the side chain of the modified polyion liquid is an ester structure comprising a quaternary ammonium salt cationic group containing a functional group and an anionic group. By regulating and controlling the side chain structure and the functional group type of the polyion liquid, the ion transference number and the electrochemical window can be improved, and the compatibility of the polymer solid electrolyte and an electrode interface is remarkably improved, so that the charge-discharge performance of a secondary battery is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and particularly relates to a modified poly-ionic liquid-based solid electrolyte, a preparation method thereof and a secondary battery. BACKGROUND

[0002] With the synergistic resonance of technology iteration and market demand, developing lithium ion batteries with high energy density and high safety is an important research direction in the current new energy field, which has a wide application prospect in the fields of electric vehicles, energy storage systems and portable electronic devices. Among them, lithium metal batteries are considered as an ideal system to break through the energy density bottleneck of existing lithium ion batteries because the negative electrode has a very high theoretical specific capacity (3860 mAh / g) and the lowest electrochemical potential (-3.04 V vs. SHE). However, lithium metal batteries face many challenges in practical application: for example, the traditional liquid electrolyte can easily cause lithium dendrite growth, interface side reactions and leakage of flammable substances, which further aggravates the safety hazard. In order to solve the above problems, researchers actively develop solid-state battery technology, which uses solid-state electrolyte to replace the traditional liquid electrolyte, which can effectively inhibit the growth of lithium dendrites, thereby improving the safety of the secondary battery. In addition, the above solid-state electrolyte can also be compatible with high-voltage cathodes and lithium metal anodes, so that the energy density of the secondary battery breaks through 500 Wh / kg.

[0003] Polymer electrolytes are attracting much attention due to their light weight, good flexibility, easy processing and tight contact with electrode interface. In fact, traditional polyethylene oxide (PEO) and other polymer electrolytes have problems such as low room temperature ionic conductivity (<10 -4 S / cm), insufficient lithium ion transference number (~0.2) and narrow electrochemical window (<4 V). In recent years, poly-ionic liquid (PILs) based solid electrolytes exhibit unique application potential by combining the properties of ionic liquids (such as non-combustible, wide electrochemical stability window and excellent thermal / chemical stability) and polymers (such as mechanical stability and easy processability). However, the poly-ionic liquid-based solid electrolytes disclosed in the prior art are mostly prepared by copolymerization, which is difficult to overcome the defects of monomers, and there are still problems such as low room temperature ionic conductivity and poor interface performance with electrodes in the application process.

[0004] Therefore, in the field, there is an urgent need to develop a poly-ionic liquid-based solid electrolyte with high viscoelasticity, which has a simple preparation method and ensures high ionic conductivity, and has good interface compatibility with electrodes. SUMMARY

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a modified polyionic liquid-based solid electrolyte and its preparation method, which can improve ion transference number and electrochemical window, significantly improve the compatibility of polymer solid electrolyte with electrode interface, thereby improving the charge and discharge performance of secondary batteries.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a modified polyionic liquid-based solid electrolyte, wherein the modified polyionic liquid-based solid electrolyte comprises an electrolyte salt and a modified polyionic liquid, and the general structural formula of the modified polyionic liquid is shown in Formula 1:

[0008]

[0009] Among them, R 1 Selected from any one of hydrogen atoms, C1-C4 straight-chain aliphatic alkyl groups, C3-C6 branched aliphatic alkyl groups, or aromatic alkyl groups, R 2 It includes quaternary ammonium salt cationic and anionic groups containing functional groups, where n is 10 to 1000 and m is an integer selected from 0 to 3;

[0010] The functional group is selected from at least one of hydrogen atom, halogen atom or cyano group.

[0011] In this invention, the C1-C4 straight-chain aliphatic alkyl group exemplarily includes any one of methyl, ethyl, n-propyl or n-butyl; the C3-C6 branched aliphatic alkyl group exemplarily includes any one of isopropyl, isobutyl or isopentyl; and the aromatic alkyl group exemplarily includes phenyl.

[0012] In this invention, n is 10 to 1000, for example, it can be 10, 20, 50, 80, 100, 200, 500, 800 or 1000, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] In this invention, m is selected from integers from 0 to 3, for example, it can be 0, 1, 2 or 3.

[0014] In this invention, the halogen atom exemplarily includes any one of fluorine, chlorine, bromine, or iodine atoms.

[0015] First, this invention provides a functionalized polyionic liquid-based solid electrolyte. From the perspective of polymer molecular chain structure design, based on a carbon-carbon alkyl chain as the main chain, by controlling the branching structure of the side chains and introducing specific types of functional groups, the mobility of the main chain is promoted, the crystallinity and glass transition temperature of the polymer are reduced, thereby promoting the dissociation of lithium salts and improving lithium ion migration, significantly improving the room-temperature ionic conductivity of the polyionic liquid-based solid electrolyte. Second, by introducing polar functional groups into the side chain structure of the polymer, this invention can lower the HOMO level of the polyionic liquid-based solid electrolyte, improve its electrochemical oxidation stability, and thus increase the electrochemical oxidation window of the polyionic liquid-based solid electrolyte. Furthermore, the aforementioned polar functional groups can regulate the interaction between functional groups in the polyionic liquid and nearby Li... + The ion-dipole interaction, recombining Li + Solvation structure, improved Li + The desolvation process is an effective pathway, which facilitates the construction of a stable electrode / electrolyte interface, thereby improving the interfacial contact performance between the polymer electrolyte and the electrode. Finally, this invention improves the viscosity and elasticity of the polymer solid electrolyte by introducing dynamic bonds such as hydrogen bonds within the polymer chain segments, and the three-dimensional network of the polymer compound itself can store elastic potential energy to cope with high deformation conditions.

[0016] Preferably, please refer to Figure 1 As shown, the general structural formula of the modified polyionic liquid is shown in Formula 2:

[0017]

[0018] Wherein, A is selected from any one of hydrogen atoms, C1-C4 straight-chain aliphatic alkyl groups, C3-C6 branched aliphatic alkyl groups, or aromatic alkyl groups; B, C, or D are each independently selected from any one of hydrogen atoms, C1-C4 straight-chain aliphatic alkyl groups, C3-C6 branched aliphatic alkyl groups, aromatic alkyl groups, aliphatic alkyl groups containing functional groups, or aromatic alkyl groups containing functional groups; and at least one of B, C, or D is selected from any one of hydrogen atoms, aliphatic alkyl groups containing functional groups, or aromatic alkyl groups containing functional groups; X - It is an anionic group, n is 10 to 1000, and m is an integer selected from 0 to 3.

[0019] More preferably, A is selected from methyl, and B, C, or D are each independently selected from any one of hydrogen atoms, C1-C4 straight-chain aliphatic alkyl groups, or C1-C4 straight-chain aliphatic alkyl groups containing functional groups, and at least one of B, C, or D is selected from hydrogen atoms or C1-C4 straight-chain aliphatic alkyl groups containing functional groups. -It is an anionic group, n is 10 to 1000, and m is an integer selected from 0 to 3, but not limited thereto.

[0020] Specifically, the C1-C4 straight-chain aliphatic alkyl group exemplary includes any one of methyl, ethyl, n-propyl, or n-butyl. Exemplarily, B, C, or D are each independently selected from any one of hydrogen atom, methyl, ethyl, n-propyl, n-butyl, ethyl containing a functional group, n-propyl containing a functional group, or n-butyl containing a functional group.

[0021] Specifically, X is selected from Cl - ,Br - I - Tetrafluoroborate (BF4) - ), hexafluorophosphate (PF6) - It may be any one of the following, but is not limited to: bis(trifluoromethanesulfonate) imine anion (TFSI), bis(fluoromethanesulfonate) imine anion (FSI), or difluorooxalateborate anion (DFOB).

[0022] Preferably, the functional group is selected from at least one of hydrogen atom, fluorine atom or cyano group.

[0023] Preferably, the modified polyionic liquid is any one of the following compounds:

[0024]

[0025] Preferably, based on the total mass of the modified polyionic liquid-based solid electrolyte as 100%, the mass percentage of the modified polyionic liquid is 50wt% to 95wt%, and the mass percentage of the electrolyte salt is 5wt% to 50wt%.

[0026] Specifically, the mass percentage of the modified polyionic liquid can be, for example, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, or 95wt%, etc.; the mass percentage of the electrolyte salt can be, for example, 5wt%, 10wt%, 20wt%, 30wt%, 40wt%, or 50wt%, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the number average molecular weight of the modified polyionic liquid is 1,000 to 50,000, more preferably 1,000 to 10,000, for example, it can be 1,000, 2,000, 5,000, 8,000, 10,000, 20,000, 30,000, 40,000 or 50,000, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] In this invention, by adjusting the number-average molecular weight of the modified polyionic liquid to a suitable range, the viscosity and elasticity of the polyionic liquid-based solid electrolyte are improved, as well as its ease of processing.

[0029] Preferably, the modified polyionic liquid-based solid electrolyte has a room temperature ionic conductivity of up to 5 × 10⁻⁶. -4 Scm -1 For example, it can be 1×10 -4 S cm -1 2×10 -4 S cm -1 3×10 -4 S cm -1 4×10 -4 S cm -1 Or 5×10 -4 S cm -1 The term "etc." is not limited to the listed values; it also applies to other unlisted values ​​within the range.

[0030] Preferably, the metal ion transference number of the modified polyionic liquid-based solid electrolyte is >0.5, for example, it can be 0.55, 0.58, 0.6, 0.62, 0.65 or 0.7, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] In a second aspect, the present invention provides a method for preparing a modified polyionic liquid-based solid electrolyte as described in the first aspect, the method comprising the following steps:

[0032] The monomers, electrolyte salts, and initiators of the modified polyionic liquid are formulated into a precursor solution, and the precursor solution is subjected to a polymerization reaction to obtain the modified polyionic liquid-based solid electrolyte.

[0033] Preferably, the method for preparing the monomer of the modified polyionic liquid includes the following steps:

[0034] An intermediate product is obtained by reacting an alkyl amine ester of olefinic acid, a functionalizing agent, and a solvent; the intermediate product is then subjected to anion exchange with a metal salt to obtain the monomer of the modified polyionic liquid.

[0035] More preferably, the general structural formula of the tertiary amine alkyl ester of olefinic acid is shown in Formula 3:

[0036]

[0037] Wherein, A is selected from any one of hydrogen atom, C1-C4 straight-chain aliphatic alkyl, C3-C6 branched aliphatic alkyl or aromatic alkyl, and m is selected from an integer from 0 to 3.

[0038] Preferably, the functionalizing agent includes at least one of hydrochloric acid, polyhalogenated alkanes, or cyano-containing haloalkanes.

[0039] Preferably, the polyhalogenated alkane contains at least two halogen atoms.

[0040] Preferably, the molar ratio of the alkyl tertiary amine ester of olefinic acid to the functionalizing reagent is 1:1.2 to 1:3, for example, it can be 1:1.2, 1:1.5, 1:2, 1:1.2.5 or 1:3, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, the reaction temperature is 25℃ to 95℃, for example, it can be 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃ or 95℃, etc.; the reaction time is 4h to 24h, for example, it can be 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h or 24h, etc., not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0042] In this invention, the process of anion exchange between the intermediate product and the metal salt includes: adding an aqueous solution containing the metal salt dropwise to an aqueous solution containing the intermediate product, stirring at room temperature for 24 hours, washing three times with deionized water, testing the water for residual halide ions with silver nitrate, and obtaining the monomer of the modified polyionic liquid after extraction.

[0043] Specifically, the monomer of the modified polyionic liquid is any one of the following compounds:

[0044]

[0045] This invention cleverly obtains monomers of modified polyionic liquids containing functional groups by selecting inexpensive and readily available tertiary amine raw materials containing alkenyl active groups and reacting them with dilute hydrochloric acid or haloalkanes containing halogen atoms or cyano groups to achieve carbon-nitrogen bond construction.

[0046] Preferably, the mass ratio of the initiator, the monomer of the modified polyionic liquid, and the electrolyte salt is (0.1–5):100, for example, it can be 0.1:100, 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, or 5:100, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the polymerization reaction includes photopolymerization and / or thermal polymerization.

[0048] Preferably, the photopolymerization reaction is carried out under 365nm ultraviolet light, and the photopolymerization reaction time is 2min to 10min, for example, 2min, 5min, 8min or 10min, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0049] Preferably, the temperature of the thermal polymerization reaction is 40℃ to 80℃, for example, 40℃, 50℃, 60℃, 70℃ or 80℃; the time of the thermal polymerization reaction is 6h to 12h, for example, 6h, 8h, 10h or 12h, and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] In this invention, the initiator includes a photoinitiator and / or a thermal initiator.

[0051] Furthermore, the initiator may be, for example, any one or a combination of at least two of the following thermal initiators: azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dialkyl peroxide, cumene hydroperoxide, or tert-butyl hydroperoxide; or any one or a combination of at least two of the following photoinitiators: 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; but is not limited thereto.

[0052] Thirdly, the present invention provides a secondary battery comprising a modified polyionic liquid-based solid electrolyte as described in the first aspect.

[0053] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] This invention provides a modified polyionic liquid-based solid electrolyte, which combines excellent room-temperature ionic conductivity, good electrode / electrolyte interface contact, excellent thermal stability, and a wide electrochemical window. It is particularly suitable for high-voltage cathodes and lithium metal anodes with high energy density, and the secondary battery prepared from it exhibits excellent room-temperature and high-temperature cycling stability, as detailed below:

[0056] (1) First, this invention provides a functionalized polyionic liquid-based solid electrolyte. From the perspective of polymer molecular chain structure design, based on a carbon-carbon alkyl chain as the main chain, by controlling the branching structure of the side chains and introducing specific types of functional groups, the mobility of the main chain is promoted, the crystallinity and glass transition temperature of the polymer are reduced, thereby promoting the dissociation of lithium salts and improving the migration of lithium ions, significantly improving the room temperature ionic conductivity of the polyionic liquid-based solid electrolyte. Second, by introducing polar functional groups into the side chain structure of the polymer, this invention can reduce the HOMO energy level of the polyionic liquid-based solid electrolyte, improve its electrochemical oxidation stability, and thus increase the electrochemical oxidation window of the polyionic liquid-based solid electrolyte. Finally, the above-mentioned polar functional groups can regulate the interaction between the functional groups in the polyionic liquid and the nearby Li + The ion-dipole interaction, recombining Li + Solvation structure, improved Li + An effective approach to the desolvation process is to facilitate the construction of a stable electrode / electrolyte interface, thereby improving the interfacial contact performance between the polymer electrolyte and the electrode.

[0057] (2) The functionalized modified polyionic liquid-based solid electrolyte provided by this invention has a room temperature ionic conductivity of up to 5 × 10⁻⁶. -4 S cm -1 It also has the advantages of high temperature resistance and non-combustibility.

[0058] (3) The functionalized modified polyionic liquid-based solid electrolyte provided by the present invention has the advantage of high viscoelasticity to cope with high deformation conditions. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the structure of the modified polyionic liquid provided by the present invention.

[0060] Figure 2 This is a schematic diagram of the preparation reaction of each reactant in each step of Examples 1-12 of the present invention.

[0061] Figure 3 This is a schematic diagram of the preparation reaction of the modified polyionic liquid in each step of Examples 1-12 of the present invention.

[0062] Figure 4 These are the hydrogen NMR spectrum and carbon NMR spectrum of monomer A corresponding to the modified polyionic liquid in Example 1 of this invention.

[0063] Figure 5 This is the 1H NMR spectrum of monomer B corresponding to the modified polyionic liquid in Example 2 of this invention.

[0064] Figure 6This is the 1H NMR spectrum of monomer D corresponding to the modified polyionic liquid in Example 4 of this invention.

[0065] Figure 7 This is a viscoelastic photograph of the modified polyionic liquid-based solid electrolyte in Example 1 of this invention. Detailed Implementation

[0066] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the manufacturer.

[0067] Example 1

[0068] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0069] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and hydrogen substituent groups (monomer A)

[0070] 15.7 g of dimethylaminoethyl methacrylate was dissolved in 40 mL of ethyl acetate. 10.2 g of 37% concentrated hydrochloric acid was diluted with 10 mL of deionized water. The diluted hydrochloric acid was added dropwise and the mixture was reacted at room temperature for 12 h. After the reaction was complete, the mixture was extracted three times with 10 mL of ethyl acetate to obtain an aqueous solution of the intermediate product. Then, 34.5 g of lithium bis(trifluoromethanesulfonylimide) was added, and the mixture was stirred at room temperature for 12 h. The mixture was washed three times with 20 mL of deionized water, and the extract was separated. The washing water was tested with AgNO3 solution to ensure the absence of chloride ions. After freeze-drying for 12 h, 35.9 g (82%) of the product was obtained. The NMR spectrum is shown in [reference needed]. Figure 4 .

[0071] (2) The polymer electrolyte precursor solution composition is as follows: monomer A: lithium bis(trifluoromethanesulfonylimide) = 1:1 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0072] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and hydrogen-substituted groups and lithium salts were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane, and polymerization was carried out under 365 nm ultraviolet light for 2 minutes to obtain the following:Figure 7 The modified polyionic liquid-based solid electrolyte (number-average molecular weight 2710) exhibits high viscoelasticity, wherein the modified polyionic liquid comprises 60 wt% by mass and the lithium salt comprises 38 wt% by mass. An SS|polymer electrolyte|SS battery was assembled, and the tested ionic conductivity was 1.0 × 10⁻⁶. -4 S cm -1 .

[0073] Example 2

[0074] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0075] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and fluorine substituent groups (monomer B)

[0076] 15.7 g of dimethylaminoethyl methacrylate and 20.7 g of 3-fluoro-1-iodopropane were dissolved in 40 mL of ethyl acetate and reacted at 85 °C for 12 h. After the reaction was complete, the mixture was filtered to obtain a crude solid product, which was washed three times with ethyl acetate (50 mL) and filtered again to obtain an intermediate product. Then, 34.5 g of lithium bis(trifluoromethanesulfonylimide) was added, and the mixture was stirred at room temperature for 12 h. The mixture was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure the absence of iodide ions. After freeze-drying for 12 h, 42.4 g (85%) of the product was obtained. The NMR spectrum is shown in [reference needed]. Figure 5 .

[0077] (2) The polymer electrolyte precursor solution composition is: monomer B: lithium bis(trifluoromethanesulfonylimide) = 1:1 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0078] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and fluorine substituents and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 3880). The mass percentage of modified polyionic liquid was 63 wt%, and the mass percentage of lithium salt was 35 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 1.6 × 10⁻⁶. -4 Scm -1 .

[0079] Example 3

[0080] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0081] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing vinyl and cyano substituents (monomer C)

[0082] 14.3 g of dimethylaminoethyl ethylene vinylate and 16.2 g of 4-bromobutyronitrile were dissolved in 40 mL of ethyl acetate and reacted at 85 °C for 12 h. After the reaction was complete, the mixture was filtered to obtain a crude solid product, which was washed three times with ethyl acetate (50 mL) and filtered again to obtain an intermediate product. Then, 34.5 g of lithium bis(trifluoromethanesulfonyl)imide was added, and the mixture was stirred at room temperature for 12 h. The mixture was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure the absence of bromide ions. After freeze-drying for 12 h, 38.8 g (79%) of the product was obtained.

[0083] (2) The polymer electrolyte precursor solution composition is: monomer C: lithium bis(trifluoromethanesulfonylimide) = 1:1 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0084] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing vinyl and cyano substituents and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 5390). The mass percentage of modified polyionic liquid was 63 wt%, and the mass percentage of lithium salt was 35 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 2.8 × 10⁻⁶. -4 S cm -1 .

[0085] Example 4

[0086] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0087] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and cyano substituents (monomer D)

[0088] 15.7 g of dimethylaminoethyl methacrylate and 16.2 g of 4-bromobutyronitrile were dissolved in 40 mL of ethyl acetate and reacted at 85 °C for 12 h. After the reaction was complete, the mixture was filtered to obtain a crude product solid, which was washed three times with ethyl acetate (50 mL) and filtered again to obtain an intermediate product. Then, 34.5 g of lithium bis(trifluoromethanesulfonyl)imide was added, and the mixture was stirred at room temperature for 12 h. The mixture was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure the absence of bromide ions. After freeze-drying for 12 h, 37.4 g (74%) of the product was obtained. The NMR spectrum is shown in [reference needed]. Figure 6 .

[0089] (2) The polymer electrolyte precursor solution composition is: monomer D: lithium bis(trifluoromethanesulfonylimide) = 1:1 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0090] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and cyano substituents and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 4320). The mass percentage of modified polyionic liquid was 64 wt%, and the mass percentage of lithium salt was 34 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 5.0 × 10⁻⁶. -4 S cm -1 .

[0091] Example 5

[0092] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each reactant monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0093] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and hydrogen substituent groups (monomer A)

[0094] 15.7 g of dimethylaminoethyl methacrylate was dissolved in 40 mL of ethyl acetate. 10.2 g of 37% concentrated hydrochloric acid was diluted with 10 mL of deionized water. The diluted hydrochloric acid was added dropwise and the mixture was reacted at room temperature for 12 h. After the reaction was complete, the mixture was extracted three times with 10 mL of ethyl acetate to obtain an aqueous solution of the intermediate product. Then, 34.5 g of lithium bis(trifluoromethanesulfonylimide) was added, and the mixture was stirred at room temperature for 12 h. The mixture was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure that there were no chloride ions. After freeze-drying for 12 h, 35.9 g (82%) of the product was obtained.

[0095] (2) Composition of polymer electrolyte precursor solution: Monomer A: Lithium bis(trifluoromethanesulfonylimide) = 1:0.4 (molar ratio), and photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0096] (3) Modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and hydrogen-substituted groups and lithium salts were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 4570). The mass percentage of the modified polyionic liquid was 80 wt%, and the mass percentage of the lithium salt was 18 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 6.8 × 10⁻⁶. -5 S cm -1 .

[0097] Example 6

[0098] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each reactant monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0099] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and hydrogen substituent groups (monomer A)

[0100] 15.7 g of dimethylaminoethyl methacrylate was dissolved in 40 mL of ethyl acetate. 10.2 g of 37% concentrated hydrochloric acid was diluted with 10 mL of deionized water. The diluted hydrochloric acid was added dropwise and the mixture was reacted at room temperature for 12 h. After the reaction was complete, the mixture was extracted three times with 10 mL of ethyl acetate to obtain an aqueous solution of the intermediate product. Then, 34.5 g of lithium bis(trifluoromethanesulfonylimide) was added, and the mixture was stirred at room temperature for 12 h. The mixture was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure that there were no chloride ions. After freeze-drying for 12 h, 35.9 g (82%) of the product was obtained.

[0101] (2) The polymer electrolyte precursor solution composition is as follows: monomer A: lithium bis(trifluoromethanesulfonylimide) = 1:0.5 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0102] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and NH substituent groups and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 5980). The mass percentage of modified polyionic liquid was 75 wt%, and the mass percentage of lithium salt was 23 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 8.8 × 10⁻⁶. -5 Scm -1 .

[0103] Example 7

[0104] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0105] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and hydrogen substituent groups (monomer A)

[0106] 15.7 g of dimethylaminoethyl methacrylate was dissolved in 40 mL of ethyl acetate. 10.2 g of 37% concentrated hydrochloric acid was diluted with 10 mL of deionized water, and the diluted hydrochloric acid was added dropwise to the solution. The mixture was reacted at room temperature for 12 h. After the reaction was complete, the solution was extracted three times with 10 mL of ethyl acetate to obtain an aqueous solution of the intermediate product. Then, 34.5 g of lithium bis(trifluoromethanesulfonylimide) was added, and the mixture was stirred at room temperature for 12 h. The solution was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure that there were no chloride ions. After freeze-drying for 12 h, 35.9 g (82%) of the product was obtained.

[0107] (2) The polymer electrolyte precursor solution composition is as follows: monomer A: lithium bis(trifluoromethanesulfonylimide) = 1:0.8 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0108] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and hydrogen-substituted groups and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 6140). The mass percentage of modified polyionic liquid was 65 wt%, and the mass percentage of lithium salt was 33 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 9.8 × 10⁻⁶. -5 Scm -1 .

[0109] Example 8

[0110] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0111] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and hydrogen substituent groups (monomer E)

[0112] 15.7 g of dimethylaminoethyl methacrylate was dissolved in 40 mL of ethyl acetate. 10.2 g of 37% concentrated hydrochloric acid was diluted with 10 mL of deionized water. The diluted hydrochloric acid was added dropwise and the mixture was reacted at room temperature for 12 h. After the reaction was complete, the mixture was filtered to obtain a crude product solid. The crude product solid was washed three times with ethyl acetate (50 mL) and filtered again to obtain an intermediate product. Then, 22.5 g of lithium bis(fluorosulfonyl)imide was added, and the mixture was stirred at room temperature for 12 h. The intermediate product was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure that there were no chloride ions. After freeze-drying for 12 h, 26.7 g (79%) of the product was obtained.

[0113] (2) The polymer electrolyte precursor solution composition is: monomer E: lithium bis(fluorosulfonyl)imide = 1:1 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0114] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and hydrogen-substituted groups and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 8540). The mass percentage of modified polyionic liquid was 70 wt%, and the mass percentage of lithium salt was 28 wt%. SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 2.1 × 10⁻⁶. -4 Scm -1 .

[0115] Example 9

[0116] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0117] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and fluorine substituent groups (monomer F)

[0118] 15.7 g of dimethylaminoethyl methacrylate and 20.7 g of 3-fluoro-1-iodopropane were dissolved in 40 mL of ethyl acetate and reacted at 85 °C for 12 h. After the reaction was complete, the mixture was filtered to obtain a crude solid product, which was washed three times with ethyl acetate (50 mL) and filtered again to obtain an intermediate product. Then, 22.5 g of lithium bis(fluorosulfonyl)imide was added, and the mixture was stirred at room temperature for 12 h. The mixture was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure the absence of iodide ions. After freeze-drying for 12 h, 31.9 g (83%) of the product was obtained.

[0119] (2) The polymer electrolyte precursor solution composition is: monomer F: lithium bis(fluorosulfonyl)imide = 1:1 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0120] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and fluorine substituents and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 6770). The mass percentage of modified polyionic liquid was 73 wt%, and the mass percentage of lithium salt was 25 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 2.6 × 10⁻⁶.-4 Scm -1 .

[0121] Example 10

[0122] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each reactant monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0123] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing vinyl and cyano substituents (monomer G)

[0124] 14.3 g of dimethylaminoethyl ethylene vinylate and 16.2 g of 4-bromobutyronitrile were dissolved in 40 mL of ethyl acetate and reacted at 85 °C for 12 h. After the reaction was completed, the mixture was filtered to obtain a crude solid product, which was washed three times with ethyl acetate (50 mL) and filtered again to obtain an intermediate product. Then, 22.5 g of lithium bis(fluorosulfonyl)imide was added, and the mixture was stirred at room temperature for 12 h. After washing three times with 20 mL of deionized water, the mixture was extracted and separated. The washing water was tested with AgNO3 solution to find that there were no bromide ions. After freeze-drying for 12 h, 28.5 g (72%) of the product was obtained.

[0125] (2) The polymer electrolyte precursor solution composition is: monomer G: lithium bis(fluorosulfonyl)imide = 1:1 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0126] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing vinyl and cyano substituents and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 5680). The mass percentage of modified polyionic liquid was 73 wt%, and the mass percentage of lithium salt was 25 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 3.1 × 10⁻⁶. -4 S cm -1 .

[0127] Example 11

[0128] This embodiment provides a modified polyionic liquid-based solid electrolyte and its preparation method. Please refer to the schematic diagrams of the reaction between each reactant monomer and the modified polyionic liquid in each step. Figures 2-3 As shown:

[0129] (1) Preparation of quaternary ammonium salt cationic ionic liquid monomers containing allyl and cyano substituents (monomer H)

[0130] 15.7 g of dimethylaminoethyl methacrylate and 16.2 g of 4-bromobutyronitrile were dissolved in 40 mL of ethyl acetate and reacted at 85 °C for 12 h. After the reaction was complete, the mixture was filtered to obtain a crude solid product, which was washed three times with ethyl acetate (50 mL) and filtered again to obtain an intermediate product. Then, 22.5 g of lithium bis(fluorosulfonyl)imide was added, and the mixture was stirred at room temperature for 12 h. The mixture was washed three times with 20 mL of deionized water, extracted, and separated. The washing water was tested with AgNO3 solution to ensure the absence of bromide ions. After freeze-drying for 12 h, 27.5 g (68%) of the product was obtained.

[0131] (2) The polymer electrolyte precursor solution composition is: monomer H: lithium bis(fluorosulfonyl)imide = 1:1 (molar ratio), and the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt).

[0132] (3) Preparation of modified polyionic liquid-based solid electrolyte: Quaternary ammonium salt cationic liquid monomers containing allyl and cyano substituents and lithium salt were uniformly mixed according to the formula, and then a photoinitiator was added. After magnetic stirring for 2 hours, a homogeneous solution was obtained. The solution was dropped onto a glass fiber membrane and polymerized under 365 nm ultraviolet light for 2 minutes to obtain a modified polyionic liquid-based solid electrolyte (number average molecular weight of 4230). The mass percentage of modified polyionic liquid was 73 wt%, and the mass percentage of lithium salt was 25 wt%. The SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 4.8 × 10⁻⁶. -4 S cm -1 .

[0133] Example 12

[0134] The difference between this embodiment and Embodiment 1 is that, in the preparation process of the modified polyionic liquid-based solid electrolyte, the photoinitiator is replaced with an equal amount of benzoyl peroxide thermal initiator, resulting in a modified polyionic liquid-based solid electrolyte (number-average molecular weight of 4670). The modified polyionic liquid comprises 60 wt% of the electrolyte, and the lithium salt comprises 38 wt% of the lithium salt. An SS|polymer electrolyte|SS battery was assembled, and the tested ionic conductivity was 4.5 × 10⁻⁶. -7 S cm -1 Everything else is the same as in Example 1.

[0135] Comparative Example 1

[0136] The difference between this comparative example and Example 1 is that lithium bis(trifluoromethanesulfonylimide) was not added to the polymer electrolyte precursor solution, and the photoinitiator was bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (2% of the total mass of monomer and lithium salt), resulting in a modified polyionic liquid-based solid electrolyte (number-average molecular weight of 8380). An SS|polymer electrolyte|SS battery was assembled, and the tested ionic conductivity was 4.5 × 10⁻⁶. -7 S cm -1 Everything else is the same as in Example 1.

[0137] Comparative Example 2

[0138] The difference between this comparative example and Example 1 is that the modified polyionic liquid obtained from monomer A is replaced with an equal mass percentage of trifluoroethyl polyacrylate, resulting in a modified polyionic liquid-based solid electrolyte. An SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was measured to be 1.5 × 10⁻⁶. -7 S cm -1 Everything else is the same as in Example 1.

[0139] Comparative Example 3

[0140] The difference between this comparative example and Example 1 is that the cationic group in monomer A was replaced with an equal mass percentage of N,N,N-trimethyl-2-[(2-methyl-2-acryloyl)oxy]ethylamine (CAS No.: 33611-56-2), resulting in a modified polyionic liquid-based solid electrolyte (number average molecular weight 5950). The modified polyionic liquid comprised 61 wt% of the electrolyte, and the lithium salt comprised 37 wt%. An SS|polymer electrolyte|SS battery was assembled, and the ionic conductivity was tested to be 1.8 × 10⁻⁶. -4 S cm -1 Everything else is the same as in Example 1.

[0141] Test conditions

[0142] The polymer electrolytes provided in Examples 1 to 11 and Comparative Example 3 were used to assemble lithium-ion solid-state batteries, and performance tests were conducted under the following conditions:

[0143] (1) Fabrication of lithium-ion solid-state batteries:

[0144] 1. Preparation of positive electrode sheet

[0145] LiNi 0.8 Co 0.1 Mn 0.1O2 cathode material, conductive agent Super P, and binder PVDF are mixed in a mass ratio of 97:1:2. The mixture is then dispersed in N-methylpyrrolidone to form a uniform cathode slurry. Subsequently, the cathode slurry is uniformly coated onto aluminum foil, and after drying and rolling processes, the cathode sheet is finally obtained.

[0146] 2. Preparation of negative electrode sheet

[0147] Artificial graphite anode active material, conductive agent Super P, and binder styrene-butadiene latex are mixed in a mass ratio of 95:3:2 and dispersed in appropriate deionized water to form a negative electrode slurry. Next, the negative electrode slurry is coated onto copper foil, and after drying and rolling, a negative electrode sheet is obtained.

[0148] 3. Lithium-ion solid-state batteries

[0149] The above-mentioned positive electrode, negative electrode and polymer electrolyte are assembled to obtain a lithium-ion solid-state battery.

[0150] (2) Performance testing:

[0151] The specific capacity of the lithium-ion solid-state battery under the charge / discharge voltage range of 2.7V to 4.3V and the current density of 1C was tested, as well as the capacity retention rate after 100 cycles.

[0152] The test results are shown in Table 1:

[0153] Table 1

[0154]

[0155]

[0156] As can be seen from Table 1, by regulating the structure of the modified polyionic liquid and the functional groups it contains, and further optimizing the type and content of lithium salt, the present invention can improve the ion transference number and electrochemical window of the polymer electrolyte, significantly improve the compatibility of the polymer solid electrolyte and the electrode interface, and make the assembled lithium-ion solid battery have high capacity and good cycle performance.

[0157] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A modified polyionic liquid-based solid electrolyte, characterized in that, The modified polyionic liquid-based solid electrolyte comprises an electrolyte salt and a modified polyionic liquid, the general structural formula of which is shown in Formula 1: Among them, R 1 Selected from any one of hydrogen atoms, C1-C4 straight-chain aliphatic alkyl groups, C3-C6 branched aliphatic alkyl groups, or aromatic alkyl groups, R 2 It includes quaternary ammonium salt cationic and anionic groups containing functional groups, where n is 10 to 1000 and m is an integer selected from 0 to 3; The functional group is selected from at least one of hydrogen atom, halogen atom or cyano group.

2. The modified polyionic liquid-based solid electrolyte according to claim 1, characterized in that, The general structural formula of the modified polyionic liquid is shown in Formula 2: Wherein, A is selected from any one of hydrogen atoms, C1-C4 straight-chain aliphatic alkyl groups, C3-C6 branched aliphatic alkyl groups, or aromatic alkyl groups; B, C, or D are each independently selected from any one of hydrogen atoms, C1-C4 straight-chain aliphatic alkyl groups, C3-C6 branched aliphatic alkyl groups, aromatic alkyl groups, aliphatic alkyl groups containing functional groups, or aromatic alkyl groups containing functional groups; and at least one of B, C, or D is selected from any one of hydrogen atoms, aliphatic alkyl groups containing functional groups, or aromatic alkyl groups containing functional groups; X - It is an anionic group, n is 10 to 1000, and m is an integer selected from 0 to 3.

3. The modified polyionic liquid-based solid electrolyte according to claim 2, characterized in that, A is selected from methyl, and B, C, or D are each independently selected from any one of hydrogen atoms, C1-C4 straight-chain aliphatic alkyl groups, or C1-C4 straight-chain aliphatic alkyl groups containing functional groups, and at least one of B, C, or D is selected from hydrogen atoms or C1-C4 straight-chain aliphatic alkyl groups containing functional groups. - It is an anionic group, n is 10 to 1000, and m is an integer selected from 0 to 3; And / or, the functional group is selected from at least one of hydrogen atom, fluorine atom or cyano group.

4. The modified polyionic liquid-based solid electrolyte according to any one of claims 1-3, characterized in that, The modified polyionic liquid is any one of the following compounds:

5. The modified polyionic liquid-based solid electrolyte according to claim 1, characterized in that, Based on the total mass of the modified polyionic liquid-based solid electrolyte as 100%, the mass percentage of the modified polyionic liquid is 50wt% to 95wt%, and the mass percentage of the electrolyte salt is 5wt% to 50wt%. And / or, the number-average molecular weight of the modified polyionic liquid is 1000 to 50000.

6. The modified polyionic liquid-based solid electrolyte according to claim 1, characterized in that, The modified polyionic liquid-based solid electrolyte has a room temperature ionic conductivity of up to 5 × 10⁻⁶. -4 Scm -1 ; And / or, the metal ion transference number of the modified polyionic liquid-based solid electrolyte is >0.

5.

7. A method for preparing a modified polyionic liquid-based solid electrolyte as described in any one of claims 1-6, characterized in that, The preparation method includes the following steps: The monomers, electrolyte salts, and initiators of the modified polyionic liquid are formulated into a precursor solution, and the precursor solution is subjected to a polymerization reaction to obtain the modified polyionic liquid-based solid electrolyte.

8. The preparation method according to claim 7, characterized in that, The method for preparing the monomer of the modified polyionic liquid includes the following steps: An intermediate product is obtained by reacting an alkyl amine ester of olefinic acid, a functionalizing agent, and a solvent; the intermediate product is then subjected to anion exchange with a metal salt to obtain the monomer of the modified polyionic liquid. The general structural formula of the alkyl tertiary amine ester of olefinic acid is shown in Formula 3: Wherein, A is selected from any one of hydrogen atom, C1-C4 straight-chain aliphatic alkyl, C3-C6 branched aliphatic alkyl or aromatic alkyl, and m is selected from an integer from 0 to 3; The functionalizing agent includes at least one of hydrochloric acid, polyhalogenated alkanes, or cyano-containing haloalkanes. The polyhalogenated alkanes contain at least two halogen atoms. The molar ratio of the alkyl tertiary amine ester of the olefinic acid to the functionalizing reagent is 1:1.2 to 1:3; The reaction temperature is 25℃~95℃, and the reaction time is 4h~24h.

9. The preparation method according to claim 7, characterized in that, The mass ratio of the initiator to the monomer and electrolyte salt of the modified polyionic liquid is (0.1-5):100; And / or, the polymerization reaction may be carried out in the manner of photopolymerization and / or thermal polymerization; The photopolymerization reaction is carried out under ultraviolet light, and the photopolymerization reaction time is 2 min to 10 min. The temperature of the thermal polymerization reaction is 40℃~80℃, and the time of the thermal polymerization reaction is 6h~12h.

10. A secondary battery, characterized in that, The secondary battery comprises a modified polyionic liquid-based solid electrolyte as described in any one of claims 1-6.

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