Modified electrolyte, method for preparing the same, use thereof, and alkali metal solid-state secondary battery

Abstract

This invention belongs to the field of solid-state batteries, specifically relating to modified electrolytes, their preparation methods, applications, and alkali metal solid-state secondary batteries. The preparation method of the modified electrolyte involves polymerizing a mixed solution containing a composite monomer, an alkali metal conductive salt, a crosslinking agent, an initiator, and a solvent. The composite monomer comprises monomer 1 and monomer 2; monomer 1 is a compound having the structural formula 1; monomer 2 is at least one of an ether monomer, a carbonate monomer, and an acrylate monomer; and the solvent is a solvent containing amide bonds. This invention innovatively uses polymerizable monomer 1 as the monomer, combining it with monomer 2 and the solvent containing amide bonds. This achieves synergy, optimizes the polymerization behavior and polymerization network, and thus improves the stability of the prepared electrolyte under extreme conditions, especially under ultra-high temperatures.

Description

Technical Field

[0001] This invention belongs to the field of battery materials, specifically relating to the field of electrolyte technology. Background Technology

[0002] Solid-state alkali metal batteries (such as solid lithium / sodium / potassium metal batteries) use solid electrolytes instead of organic electrolytes, which offer higher mechanical strength, higher theoretical specific capacity, and lower standard electrode potential (compared to the standard hydrogen potential), potentially overcoming the technological bottlenecks of traditional batteries. However, the safety issues caused by the volatilization and gas expansion of electrolyte components at high temperatures remain significant concerns.

[0003] Cocrystalline electrolytes are low-melting-point eutectic mixtures formed by intermolecular interactions such as hydrogen bonds, van der Waals forces, and Lewis acid-base interactions between two or more components. Their core characteristic is that the melting point of the mixture is much lower than that of any single pure component, thus exhibiting a liquid state at or near room temperature. This property endows eutectic electrolytes with high flash and boiling points, making them less prone to volatilization in high-temperature environments, reducing the risk of battery fire and explosion, and improving battery safety. Furthermore, the unique solvation structure formed by eutectic electrolytes can create a robust electrolyte-interface layer at the interface, enabling stable battery operation at high temperatures. Therefore, using eutectic electrolytes is an advanced battery construction strategy for achieving excellent thermal and interfacial stability. Existing technologies also provide some eutectic electrolyte solutions; for example, patent document CN120690912A discloses a deep eutectic gel polymer electrolysis method, its preparation, and its application. Patent document CN120767401A discloses a deep eutectic polymer electrolyte, its preparation method, and its application. The raw materials for this deep eutectic polymer electrolyte include a deep eutectic solvent, polymer monomers, and a plasticizer. The deep eutectic solvent includes 1,11-dicyano-3,6,9-oxa-undecane and a lithium salt; the mass ratio of 1,11-dicyano-3,6,9-oxa-undecane, the lithium salt, and the plasticizer is (1~3):1:(0~1). The deep eutectic polymer electrolyte of this invention uses 1,11-dicyano-3,6,9-oxa-undecane and a lithium salt as the deep eutectic solvent. In addition, patent document CN119361815A discloses a deep eutectic gel electrolyte and its preparation method and application. The raw materials of the deep eutectic gel electrolyte include a polymerizable deep eutectic solvent and an initiator. The polymerizable deep eutectic solvent is obtained by heating a mixture of the following independently stored components: a hydrogen bond donor and a hydrogen bond acceptor.

[0004] In summary, existing technologies disclose some methods for eutectic modification of electrolytes, but these methods are difficult to fundamentally improve the stability of electrolytes under extreme conditions, especially at ultra-high temperatures. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for preparing a modified electrolyte, which is designed to provide an electrolyte that is suitable for extreme working conditions such as high temperatures and can operate stably.

[0006] The second objective of this invention is to provide the modified electrolyte prepared by the aforementioned method and its application in lithium, sodium, and potassium secondary batteries.

[0007] A third objective of this invention is to provide a lithium, sodium, or potassium secondary battery comprising the modified electrolyte.

[0008] A method for preparing a modified electrolyte involves polymerizing a mixed solution comprising a composite monomer, an alkali metal conductive salt, a crosslinking agent, an initiator, and a solvent; wherein the composite monomer comprises monomer 1 and monomer 2; monomer 1 is a compound having the structural formula 1; monomer 2 is at least one of an ether monomer, a carbonate monomer, and an acrylate monomer; and the solvent is a solvent containing an amide bond.

[0009] Formula 1;

[0010] In Formula 1, R1 and R2 are individually H, vinyl, ethynyl, substituted alkyl or substituted olefin; or R1 and R2 are cyclized to form a five- or six-membered ring;

[0011] The substituted alkyl group is a group with a substituent a on a C1-C6 alkyl group, and the substituted olefinic group is a group with a substituent b on a double bond; wherein, substituent a is at least one selected from olefinic group, alkyneic group, heterocyclic aryl group, benzene ring, alkoxy group, ester group, and acyl group; and substituent b is at least one selected from alkoxy group, aminoalkoxy group, alkyl group, and heterocyclic group.

[0012] The R3 is H, Li, Na, K, or a C1-C6 alkyl or allyl group;

[0013] In the R1~R3, at least one substituent contains a C=C double bond or an alkynyl group.

[0014] This invention innovatively uses polymerizable Formula 1 as a monomer, combining it with monomer 2 and the solvent of the amide bond. This enables synergy, optimizes polymerization behavior and polymerization network, and thus improves the stability of the prepared electrolyte under extreme conditions, especially under ultra-high temperature conditions.

[0015] In this invention, monomer 1 includes at least one of formula 1A, formula 1B, formula 1C, formula 1D, formula 1E and formula 1F;

[0016] Formula 1A; Formula 1B; Formula 1C; Formula 1D; Equation 1E; Formula 1F;

[0017] Preferably, monomer 1 comprises formula 1A and formula 1C in a weight ratio of 1:0.5~2. Studies have shown that the preferred composite monomer 1, in combination with the amide bond solvent and monomer 2, helps to further construct a highly stable eutectic structure and further enhances the wide-temperature-range conductivity and stability of the electrolyte.

[0018] In this invention, monomer 2 comprises one or more of ethylene oxide, propylene oxide, 1,3-dioxolane, vinylene carbonate, vinyl ethylene carbonate, methoxy polyethylene glycol acrylate, polyethylene glycol diacrylate, methoxy polyethylene glycol methacrylate, polyethylene glycol methacrylate, and polyethylene glycol dimethacrylate; more preferably, it comprises at least one of ether monomers (at least one of ethylene oxide, propylene oxide, and 1,3-dioxolane) and acrylate monomers (at least one of methoxy polyethylene glycol acrylate, polyethylene glycol diacrylate, methoxy polyethylene glycol methacrylate, polyethylene glycol methacrylate, and polyethylene glycol dimethacrylate). Preferred monomers, combined with the composite monomers described in this invention, contribute to further synergistic enhancement of performance.

[0019] Preferably, in the composite monomer, the weight ratio of monomer 1 to monomer 2 is 1:0.5~15; more preferably 1:1~10; and even more preferably 1:1~2.

[0020] In this invention, the alkali metal conductive salt includes at least one of lithium salt, sodium salt, and potassium salt, preferably including one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium nitrate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(perfluoroethylsulfonyl)imide, lithium bis(oxalate borate), sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium difluorooxalate borate, sodium ferrocyanide, sodium thiocyanate, potassium bis(trifluoromethanesulfonyl)imide, potassium hexafluorophosphate, potassium difluorooxalate borate, potassium ferrocyanide, and potassium thiocyanate.

[0021] Preferably, the crosslinking agent is selected from one or more of the following: ethoxylated glycerol triacrylate, ethoxylated bisphenol A diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol glycidyl ether, trimethylolpropane triglycidyl ether, glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether.

[0022] Preferably, the initiator comprises at least one of a thermal initiator and a photoinitiator, and more preferably includes one or more of the following: azobisisobutyronitrile, dimethyl azobisisobutyrate, azobisisoheptanenitrile, benzoyl peroxide, lauroyl peroxide, diisopropyl peroxide, dicyclohexyl peroxide, tert-butyl peroxide, tert-butyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, di-tert-butyl peroxide, dicumyl peroxide, and diisopropylbenzene peroxide, including 2-hydroxy-2-methyl-1-phenyl-1-propanone, phenyl di(2,4,6-trimethylbenzoyl)phosphine oxide, benzophenone, 2,2-dimethoxy-2-phenylethyl ketone, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-4'-(methylthio)-2-morpholinoacetone.

[0023] In this invention, the solvent includes one or more of acetamide, N-methylacetamide, trifluoroacetamide, N-methyltrifluoroacetamide, 2,2,2-trifluoro-N,N-dimethylacetamide, caprolactam, ethionamide, nicotinamide, isonicotinamide, benzamide, acetanilide, N,N-dimethylmethanesulfonamide, urea, and acetourea.

[0024] The preferred solvent of this invention contains amide bonds, which, when combined with the aforementioned composite monomer, facilitates the construction of a solvent-polymer-lithium salt ternary eutectic system, thereby significantly enhancing its stability and activity at high temperatures.

[0025] In this invention, the weight ratio of solvent, alkali metal conductive salt, monomer 1, monomer 2, crosslinking agent and initiator in the mixed solution is 1:0.5~1:0.1~2:0.2~2:0.05~0.5:0.005~0.02; further, it can be 1:0.5~0.7:0.1~1.0:0.4~1.5:0.1~0.5:0.01~0.015; even further, it is 1:0.5~0.7:0.4~0.6:0.4~0.6:0.1~0.5:0.01~0.015.

[0026] As an optional scheme, the content of alkali metal conductive salt in the mixed solution can be 15~25 wt.%, the content of monomer 2 is 15~40 wt.%, the content of monomer 1 is 2~20 wt.%, the content of crosslinking agent is 2~15 wt.%, the content of initiator is 0.1~0.5 wt.%, and the balance is solvent.

[0027] In this invention, the polymerization method is thermal polymerization (thermal initiation) and / or photopolymerization (photoinitiation);

[0028] When the polymerization method is thermal initiation, the temperature during thermal initiation is 60℃~120℃, and can be further 70~90℃. The initiation time can be reasonably adjusted according to the polymerization situation, for example, it can be 0.1~6 h, and can be further 1~3 h.

[0029] When the polymerization method is photoinitiated, the ultraviolet light irradiation wavelength in the photoinitiation is 254~365 nm, and the initiation time can be reasonably adjusted according to the polymerization situation, for example, it can be 0.1~100 min, and further, it can be 1~5 min.

[0030] The present invention also provides a modified electrolyte prepared by the aforementioned preparation method.

[0031] The preparation method described in this invention can endow the prepared electrolyte with a special network structure. In addition, based on the characteristics of the system, it is expected to construct a solvent-polymer-lithium salt ternary eutectic system, thereby enhancing the stability of the electrolyte and significantly improving its ion conduction ability and stability at ultra-high temperatures.

[0032] The present invention also provides an application of the modified electrolyte obtained by the preparation method described above, which is used to prepare alkali metal solid-state secondary batteries;

[0033] Preferably, the alkali metal solid secondary battery is prepared by combining it on the surface of at least one of the positive electrode, separator, and negative electrode, or by placing it between the positive electrode and the negative electrode.

[0034] Preferably, the alkali metal solid-state secondary battery is a lithium, sodium, or potassium secondary battery.

[0035] The present invention also provides an alkali metal solid-state secondary battery comprising the modified electrolyte prepared by the aforementioned preparation method.

[0036] The alkali metal solid-state battery of the present invention can be prepared by pre-forming the modified electrolyte on any surface of the positive electrode, negative electrode, or separator, and then assembling the battery. Alternatively, it can be prepared using conventional in-situ synthesis methods, for example, by assembling the positive electrode, separator, and negative electrode, injecting them into the mixed solution described in the present invention, and then encapsulating them for in-situ polymerization.

[0037] Beneficial effects

[0038] 1. This invention innovatively employs a combination of monomer 1 and monomer 2, which can optimize polymerization behavior and structure, optimize hydrogen bonding of polymerization segments, and is expected to significantly enhance the stability performance of electrolytes under extreme conditions such as ultra-high temperature.

[0039] 2. This invention also shows that combining the composite monomer with an amide-based flux and a lithium salt can potentially construct a ternary eutectic system of polymer-solvent and lithium salt, which can help further enhance the performance and stability of the electrolyte at ultra-high temperatures. Attached Figure Description

[0040] Figure 1This is an optical photograph of the amide eutectic solvent and lithium salt eutectic obtained in Example 1.

[0041] Figure 2 This is an optical photograph of the modified electrolyte obtained in Example 1.

[0042] Figure 3 The impedance diagrams of the modified electrolyte obtained in Example 1 at 25 °C and 120 °C are shown.

[0043] Figure 4 Linear scan voltammetry diagrams of the modified electrolyte obtained in Example 1 at 25 °C and 120 °C.

[0044] Figure 5 The graph shows the cycling performance of the modified electrolyte obtained in Example 1 at 60 °C. Detailed Implementation

[0045] The following examples are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the claims of the present invention.

[0046] In the following embodiments, the selected negative electrode is lithium metal, and the specific performance testing method includes the following steps:

[0047] (1) Impedance test: CR2025 coin cell batteries were used. The batteries were assembled in the following order: positive electrode shell-steel sheet-electrolyte-steel sheet-nickel mesh-negative electrode shell. The batteries were tested using AC impedance technology (EIS) in the Gamry electrochemical workstation.

[0048] (2) Electrochemical stability window test: CR2025 coin cell batteries were used. The batteries were assembled in the following order: positive electrode shell-steel sheet-electrolyte-lithium sheet-nickel mesh-negative electrode shell. The batteries were tested using linear sweep voltammetry (LSV) in the Gamry electrochemical workstation.

[0049] (3) Cyclic Test: CR2032 coin cells were used. The cells were assembled in the following stacking order: positive electrode shell - positive electrode sheet - electrolyte - lithium sheet - nickel mesh - negative electrode shell. A charge-discharge cycle test was performed on a Blue Electric Tester. The test conditions were 1C (170mAh / g) charge-discharge cycle, with the electrochemical window set to 2.5~4.0V and the test temperature at 60℃. The positive electrode sheet was a conventional commercial LFP positive electrode sheet, comprising an aluminum foil current collector and LFP positive electrode material composited on its surface. The LFP positive electrode material consisted of lithium iron phosphate, PVDF, and acetylene black in a weight ratio of 8:1:1.

[0050] Example 1

[0051] This embodiment provides a method for preparing and applying a modified electrolyte, wherein the solvent is N-methyltrifluoroacetamide, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide, the comonomer 1 is formula 1A; the comonomer 2 is methoxy polyethylene glycol acrylate, the crosslinking agent is trimethylolpropane triacrylate, and the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0052] The preparation method of the modified electrolyte includes the following steps:

[0053] (1) Preparation of precursor solution: Take 1 g of N-methyltrifluoroacetamide and 0.65 g of lithium bis(trifluoromethanesulfonylimide), stir at 25 °C for 12 h, then add 0.5 g of monomer 2 (methoxy polyethylene glycol acrylate), 0.5 g of monomer 1 (formula 1A), 0.1 g of trimethylolpropane triacrylate and 0.01 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone, and stir at room temperature for 4 h to obtain the precursor solution;

[0054] (2) Preparation of modified electrolyte membrane: Pour the precursor solution into a smooth and flat polytetrafluoroethylene circular ring, so that the prepolymer mixture slowly covers the bottom of the circular ring mold. After being irradiated with ultraviolet light for 3 minutes, the original material will polymerize into a film. Remove the polytetrafluoroethylene circular ring to obtain the modified electrolyte.

[0055] The modified electrolyte prepared in Example 1 has a room temperature ionic conductivity of 5.06 × 10⁻⁶. -4 S cm -1 The ionic conductivity at 120 ℃ is 1.30 × 10⁻⁶. -3 S cm -1 The electrochemical window at room temperature is 5.4 V, and the electrochemical window at 120 °C is 4.1 V.

[0056] Example 2

[0057] Compared with Example 1, the difference is that comonomer 1 is replaced with an equal weight of Formula 1B, the initiator is replaced with an equal weight of thermal initiator (azobisisobutyronitrile), the initiation condition is heating at 80°C for 2 h, and other operations and parameters are the same as in Example 1. The test results are shown in Table 1.

[0058] Example 3

[0059] Compared with Example 1, the only difference is that monomer 1 is changed, and the experimental group is:

[0060] Group A: Monomer 1 is Formula 1C;

[0061] Group B: Monomer 1 consists of Formula 1A and Formula 1C with a weight ratio of 1:1. The total amount of monomer 1 and other operations and parameters are the same as in Example 1. The test results are shown in Table 1.

[0062] Example 4

[0063] Compared with Example 1, the only difference is that the comonomer 2 is replaced with an equal weight of ether monomer 1,3-dioxolane (Group A) or carbonate monomer vinyl ethylene carbonate (Group B). All other operations and parameters are the same as in Example 1. The test results are shown in Table 1.

[0064] Example 5

[0065] Compared with Example 1, the only difference is that the concentrations of each substance are changed as follows: solvent (trifluoroacetamide) 0.69 g, lithium salt (lithium trifluoromethanesulfonate) 0.44 g, methoxy polyethylene glycol acrylate 1 g, formula 1A 0.1 g, crosslinking agent (pentaerythritol tetraacrylate) 0.3 g and initiator (2,2-dimethoxy-2-phenylethyl ketone) (0.01 g). All other operations and parameters are the same as in Example 1. The test results are shown in Table 1.

[0066] Comparative Example 1

[0067] Compared with Example 1, the only difference is that the composite monomer contains only comonomer 2, and the total amount of monomers is the same as that of the composite monomer in Example 1. All other operations and parameters are the same as those in Example 1. The test results are shown in Table 1.

[0068] Comparative Example 2

[0069] Compared with Example 1, the only difference is that the composite monomer contains only Formula 1A, and the total amount of monomer is the same as that of the composite monomer in Example 1. Other operations and parameters are the same as those in Example 1. The test results are shown in Table 1.

[0070] Comparative Example 3

[0071] Compared with Example 1, the only difference is that comparative formula A is used. The same amount of Formula 1A in the composite monomer was replaced, and other operations and parameters were the same as in Example 1. The test results are shown in Table 1.

[0072] Comparative Example 4

[0073] Compared with Example 1, the only difference is that N-methyltrifluoroacetamide solvent was replaced with an equal amount of fluoroethylene carbonate. All other operations and parameters were the same as in Example 1. The test results are shown in Table 1.

[0074] Comparative Example 5

[0075] Compared with Example 1, the only difference is that comparative formula B is used. The same amount of Formula 1A in the composite monomer was replaced, and other operations and parameters were the same as in Example 1. The test results are shown in Table 1.

[0076] The test results for each case are shown in Table 1;

[0077]

[0078] As shown in Table 1, and through Examples 1 to 5, the combination of monomer and amide solvent can synergistically improve ionic conductivity and oxidation stability, thereby improving the cycling and high-temperature stability of the solid electrolyte.

[0079] As can be seen from Examples 1, 2 and 3, using Formula 1A and Formula 1C together as monomer 1 can further optimize the performance of solid electrolytes and further enhance the cycling and high-temperature stability of gel electrolytes.

[0080] As can be seen from Examples 1 and 4, the combination of monomer 2 and monomer 1, as well as the amide solvent, can synergistically improve cycling and high-temperature stability.

[0081] Furthermore, as can be seen from Examples 1 and 5, good high-temperature stability can be maintained under the dosage described in this invention.

[0082] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified electrolyte, comprising polymerizing a mixed solution containing a complex monomer, an alkali metal conductive salt, a crosslinking agent and an initiator, and a solvent; characterized in that, The composite monomer includes monomer 1 and monomer 2; monomer 1 is a compound having the structural formula 1; monomer 2 is at least one of ether monomers, carbonate monomers and acrylate monomers; the solvent is a solvent containing amide bonds; Formula 1; In Formula 1, R1 and R2 are individually H, vinyl, ethynyl, substituted alkyl or substituted olefin; or R1 and R2 are cyclized to form a five- or six-membered ring; The substituted alkyl group is a group with a substituent a on a C1-C6 alkyl group, and the substituted olefinic group is a group with a substituent b on a double bond; wherein, substituent a is at least one selected from olefinic group, alkyneic group, heterocyclic aryl group, benzene ring, alkoxy group, ester group, and acyl group; and substituent b is at least one selected from alkoxy group, aminoalkoxy group, alkyl group, and heterocyclic group. The R3 is H, Li, Na, K, or a C1-C6 alkyl or allyl group; In the R1~R3, at least one substituent contains a C=C double bond or an alkynyl group.

2. The method for preparing a modified electrolyte according to claim 1, wherein Monomer 1 includes at least one of Formula 1A, Formula 1B, Formula 1C, Formula 1D, Formula 1E and Formula 1F; Formula 1A; Formula 1B; Formula 1C; Formula 1D; Formula 1E; Formula 1F; Preferably, monomer 1 comprises formula 1A and formula 1C in a weight ratio of 1:0.5~2.

3. The method for preparing a modified electrolyte according to claim 1, wherein The monomer 2 includes one or more of the following: ethylene oxide, propylene oxide, 1,3-dioxolane, vinylene carbonate, vinyl ethylene carbonate, methoxy polyethylene glycol acrylate, polyethylene glycol diacrylate, methoxy polyethylene glycol methacrylate, polyethylene glycol methacrylate, and polyethylene glycol dimethacrylate. Preferably, in the composite monomer, the weight ratio of monomer 1 to monomer 2 is 1:0.5~15; more preferably 1:1~10; and even more preferably 1:1~2.

4. The method for preparing a modified electrolyte according to claim 1, wherein The alkali metal conductive salt includes at least one of lithium salt, sodium salt, and potassium salt, preferably including one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium nitrate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(perfluoroethylsulfonyl)imide, lithium bis(oxalate borate), sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium difluorooxalate borate, sodium ferrocyanide, sodium thiocyanate, potassium bis(trifluoromethanesulfonyl)imide, potassium hexafluorophosphate, potassium difluorooxalate borate, potassium ferrocyanide, and potassium thiocyanate. Preferably, the crosslinking agent is selected from one or more of the following: ethoxylated glycerol triacrylate, ethoxylated bisphenol A diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol glycidyl ether, trimethylolpropane triglycidyl ether, glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether. Preferably, the initiator comprises at least one of a thermal initiator and a photoinitiator, and more preferably includes one or more of the following: azobisisobutyronitrile, dimethyl azobisisobutyrate, azobisisoheptanenitrile, benzoyl peroxide, lauroyl peroxide, diisopropyl peroxide, dicyclohexyl peroxide, tert-butyl peroxide, tert-butyl peroxyvalerate, methyl ethyl ketone peroxide, cyclohexanone peroxide, di-tert-butyl peroxide, dicumyl peroxide, and diisopropylbenzene peroxide; and 2-hydroxy-2-methyl-1-phenyl-1-propanone, phenyl di(2,4,6-trimethylbenzoyl)phosphine oxide, benzophenone, 2,2-dimethoxy-2-phenylethyl ketone, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-4'-(methylthio)-2-morpholinoacetone.

5. The method for preparing the modified electrolyte as described in claim 1, characterized in that, The solvents include one or more of acetamide, N-methylacetamide, trifluoroacetamide, N-methyltrifluoroacetamide, 2,2,2-trifluoro-N,N-dimethylacetamide, caprolactam, ethionamide, nicotinamide, isonicotinamide, benzamide, acetanilide, N,N-dimethylmethanesulfonamide, urea, and acetourea.

6. The method for preparing the modified electrolyte according to any one of claims 1 to 5, characterized in that, In the mixed solution, the weight ratio of solvent, alkali metal conductive salt, monomer 1, monomer 2, crosslinking agent and initiator is 1:0.5~1:0.1~2:0.2~2:0.05~0.5:0.005~0.02; further, it can be 1:0.5~0.7:0.1~1.0:0.4~1.5:0.1~0.5:0.01~0.015; even further, it can be 1:0.5~0.7:0.4~0.6:0.4~0.6:0.1~0.5:0.01~0.

015.

7. The method for preparing the modified electrolyte as described in claim 1, characterized in that, The polymerization methods are thermal polymerization and / or photopolymerization; The thermal polymerization temperature is 60℃~120℃, and the initiation time is 0.1~6 h; Preferably, the ultraviolet light irradiation wavelength in photopolymerization is 254~365 nm, and the initiation time is 0.1~100 min.

8. A modified electrolyte prepared by the preparation method according to any one of claims 1 to 7.

9. The application of a modified electrolyte prepared by the method according to any one of claims 1 to 7, characterized in that, It was used to prepare alkali metal solid-state secondary batteries; Preferably, the alkali metal solid secondary battery is prepared by combining it on the surface of at least one of the positive electrode, separator, and negative electrode, or by placing it between the positive electrode and the negative electrode. Preferably, the alkali metal solid-state secondary battery is a lithium, sodium, or potassium secondary battery.

10. An alkali metal solid-state secondary battery, characterized in that, The modified electrolyte comprises the preparation method described in any one of claims 1 to 7.

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