Composite in-situ solid electrolyte and secondary lithium battery

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a composite in-situ solid electrolyte and a secondary lithium battery. Compared with the prior art, the composite in-situ solid electrolyte has the advantages that the sulfonate cross-linking agent and the amidated vinyl carbonate monomer are compounded, and the constructed composite in-situ solid electrolyte has excellent oxidation resistance and is compatible with high-specific-energy battery cell systems such as high-nickel lithium cobalt oxide and high-pressure lithium cobalt oxide; the composite in-situ solid electrolyte does not contain perfluoroalkyl groups and meets the European Union standard; the composite polymer electrolyte can be combined with other special monomers for use, is completely compatible with the current liquid lithium battery production process, and can meet the customization requirements of different battery cell systems; the composite in-situ solid electrolyte contains a relatively large proportion of low-electronegativity elements, and the ion conduction capability of the composite in-situ solid electrolyte is remarkably superior to that of a traditional polymer electrolyte; the sulfonate cross-linking agent can improve the high-temperature stability of the polymerized electrolyte, can ensure that the structure is not changed at high temperature, and further embodies the dynamic advantages.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a composite in-situ solidified electrolyte and a secondary lithium battery. Background Art

[0002] New energy technologies are developing and iterating rapidly, and lithium-ion batteries have become one of the leaders. Although lithium-ion batteries have been widely used in the fields of power, energy storage, and 3C, they still face challenges of higher safety and higher energy density. To achieve a further breakthrough in the energy density of lithium-ion batteries and improve the safety of battery cells, solid-state battery technology has emerged and has developed rapidly in recent years.

[0003] As an important part of solid-state lithium battery technology, in-situ solidification technology can achieve excellent interfacial contact and improve the thermal safety of battery cells. However, the electrolyte after in-situ solidification contains polymer materials, and conventional polymer materials such as acrylate, carbonate, ether, etc. have weak antioxidant capabilities and it is difficult to ensure long-term material stability when facing strongly oxidizing cathodes or high-voltage systems. Usually, materials containing perfluoroalkyl (PFAS) or polyfluoroalkyl are used in electrolyte design to improve the antioxidant ability of the electrolyte.

[0004] Chinese Patent with publication number CN115295865A discloses a preparation method of an in-situ polymerization solid polymer electrolyte lithium-ion battery; the method includes the following steps: Step 1, dissolving polyvinylidene fluoride hexafluoropropylene in an organic solvent, stirring and mixing evenly to obtain a mixed solution A; Step 2, using the mixed solution A obtained in Step 1 as an electrospinning solution, and obtaining a polymer separator matrix by electrospinning; Step 3, drying the polymer separator matrix in a vacuum oven; Step 4, mixing a polymer monomer, a lithium salt, an initiator, and an electrolyte additive, and stirring to obtain a mixed solution B; Step 5, placing the polymer separator matrix obtained in Step 3 into a battery case with an electrode assembly, then dropping the mixed solution B obtained in Step 4, sealing and standing to form a lithium-ion battery; Step 6, heating the lithium-ion battery obtained in Step 5 to in-situ composite the polymer monomer. However, the in-situ solidified electrolyte described in the above solution needs to use PVDF-HFP and fluorine-containing additives, which will increase the cost of the electrolyte.

[0005] At present, most electrolytes applicable to strongly oxidizing cathode materials and high-voltage systems need to use fluorinated solvents or add a large amount of compounds containing perfluoroalkyl functional groups, which has an adverse impact on cost control and environmental protection.

[0006] In summary, developing an in-situ solidified electrolyte applicable to strongly oxidizing cathodes and high-voltage systems and without perfluoroalkyl materials is an important direction for the development of lithium-ion battery technology. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a composite in-situ solidified electrolyte and a secondary lithium battery.

[0008] The present invention provides a composite in-situ solidified electrolyte, which is formed by a polymerization monomer and a cross-linking agent being initiated by an initiator in an electrolyte solution;

[0009] The polymerization monomer includes an amidated vinyl carbonate monomer;

[0010] The amidated vinyl carbonate monomer is formed by a carbonate containing an alkenyl group and an amine compound;

[0011] The cross-linking agent includes a compound having the structure shown in formula (I):

[0012] Formula (I);

[0013] Wherein, n is an integer from 1 to 10, and R 1 is selected from alkenyl groups having 2 to 10 carbon atoms.

[0014] Preferably, the carbonate containing an alkenyl group is selected from one or more of vinyl ethylene carbonate, vinylene carbonate, and methylene vinyl carbonate;

[0015] And / or, the amine compound is selected from one or more of amino alcohol, aminoethanol, aminopropanol, aminobutanol, aminobenzyl alcohol, aminoethylene glycol, aminopropylene glycol, aminopentanol, aminohexanol, aminocyclohexanol, aminobenzyl alcohol, and aminobenzaldehyde.

[0016] Preferably, the amidated vinyl carbonate monomer has the structure shown in formula (II):

[0017] Formula (II);

[0018] Wherein, m is an integer from 0 to 10, and R 2 is selected from substituted or unsubstituted alkylamino groups having 1 to 10 carbon atoms, substituted or unsubstituted aromatic amine groups having 6 to 20 carbon atoms, substituted or unsubstituted cycloalkylamine groups having 6 to 20 carbon atoms, and substituted or unsubstituted heterocyclic amine groups having 2 to 10 carbon atoms;

[0019] The substituents in the substituted alkylamino group having 1 to 10 carbon atoms, the substituted aromatic amine group having 6 to 20 carbon atoms, the substituted cycloalkylamine group having 6 to 20 carbon atoms, and the substituted heterocyclic amine group having 2 to 10 carbon atoms are selected from one or more of alkyl groups having 1 to 5 carbon atoms, hydroxyl groups, aldehyde groups having 1 to 5 carbon atoms, and hydroxyalkyl groups having 1 to 5 carbon atoms.

[0020] Preferably, the R 2Selected from one of the structures shown in Formula (1) to Formula (6):

[0021] Formula (1); Formula (2); Formula (3);

[0022] Formula (4); Formula (5); Formula (6).

[0023] Preferably, the electrolyte includes an organic solvent, a lithium salt, and an additive;

[0024] The organic solvent includes a carbonate solvent;

[0025] The concentration of the lithium salt in the electrolyte is 0.5 to 2 mol / L;

[0026] The additive includes a nitrile additive; the nitrile additive includes a compound shown in Formula (III):

[0027] Formula (III);

[0028] Wherein, p and q are each independently an integer from 1 to 10.

[0029] Preferably, the nitrile additive further includes one or more of succinonitrile, 1,3,6-hexanetricarbonitrile, trans-hexenedinitrile, 1,2-bis(cyanoethoxy)ethane, 3-(trimethylsilyloxy)propionitrile, and bis(cyanoethyl)sulfone;

[0030] And / or, the additive further includes one or more of a sulfonate compound, a sulfate compound, a fluorinated additive, an unsaturated cyclic carbonate compound, a borate compound, a trimethylsilyl ester compound, and a fluorinated lithium salt compound;

[0031] And / or, the mass of the additive is 0.1% to 6% of the mass of the electrolyte.

[0032] Preferably, the fluorinated additive is selected from one or more of fluorinated ethylene carbonate, trifluoropropylene carbonate, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether;

[0033] And / or, the sulfonate compound is selected from one or more of 1,3-propane sultone, 1,4-butane sultone, methylene methanedisulfonate, and 1,3-propene sultone;

[0034] And / or, the sulfate compound is selected from one or more of ethylene sulfate, trimethylene cyclic sulfate, vinyl methyl sulfate, 4,4'-bis(ethylene sulfate), and propylene sulfite;

[0035] And / or, the unsaturated cyclic carbonate compound is selected from vinylene carbonate and / or vinyl ethylene carbonate;

[0036] And / or, the borate compound is selected from one or more of trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, and triphenyl borate;

[0037] And / or, the trimethylsilyl ester compound is selected from one or more of tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, and tris(trimethylsilyl) trifluoromethanesulfonate;

[0038] And / or, the fluorine-containing lithium salt compound is selected from lithium difluorophosphate.

[0039] Preferably, the mass of the amidated vinyl carbonate monomer is 1% - 5% of the mass of the composite in-situ solidified electrolyte;

[0040] And / or, the mass of the crosslinking agent is 0.5% - 2% of the mass of the composite in-situ solidified electrolyte;

[0041] And / or, the mass of the initiator is 0.01% - 0.3% of the mass of the composite in-situ solidified electrolyte.

[0042] Preferably, the amidated vinyl carbonate monomer is prepared by the following method:

[0043] Mix a carbonate containing an alkenyl group and an amine compound in a solvent, then add a base catalyst, and heat for reaction to obtain the amidated vinyl carbonate monomer.

[0044] The present invention also provides a secondary lithium battery, including the above-mentioned composite in-situ solidified electrolyte.

[0045] Compared with the prior art, the composite in-situ solidified electrolyte provided by the present invention has the following advantages:

[0046] 1) The present invention combines a sulfonate crosslinking agent with an amidated vinyl carbonate monomer to construct a composite in-situ solid electrolyte with excellent antioxidant properties, which is compatible with high-energy density cell systems such as high-nickel and high-voltage lithium cobaltate;

[0047] 2) This composite in-situ solid electrolyte does not contain perfluoroalkyl groups and meets EU standards;

[0048] 3) The composite polymer electrolyte can be used in combination with other special monomers and is fully compatible with the current liquid lithium battery production process, meeting the customized requirements of different cell systems;

[0049] 4) The composite in-situ solidified electrolyte contains a relatively high proportion of elements with low electronegativity, and its ionic conductivity is significantly better than that of traditional polymer electrolytes;

[0050] 5) The sulfonate cross-linking agent can improve the high-temperature stability of the polymerized electrolyte, ensuring that the structure remains unchanged at high temperatures and further demonstrating kinetic advantages. Description of the Drawings

[0051] Figure 1 1H NMR spectrum of the styrene sulfonate obtained in Example 1 of the present invention;

[0052] Figure 2 1H NMR spectrum of the styrene sulfonate obtained in Example 1 of the present invention;

[0053] Figure 3 is Figure 2 the enlarged view of area A in

[0054] Figure 4 is Figure 2 the enlarged view of area B in Detailed Embodiments

[0055] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0056] The present invention provides a composite in-situ solidified electrolyte, which is formed by polymerizing monomers and a cross-linking agent in an electrolyte solution under the initiation of an initiator;

[0057] The polymerizing monomers include aminated vinyl carbonate monomers;

[0058] The aminated vinyl carbonate monomers are formed by carbonates containing alkenyl groups and amine compounds;

[0059] The cross-linking agent includes a compound having the structure shown in formula (I):

[0060] Formula (I);

[0061] wherein n is an integer from 1 to 10, and R 1 is selected from alkenyl groups having 2 to 10 carbon atoms.

[0062] According to the present invention, the polymerization monomer includes an amidated vinyl carbonate monomer; the amidated vinyl carbonate monomer is formed by a vinyl group-containing carbonate and an amine compound; in a specific embodiment provided by the present invention, the vinyl group-containing carbonate is preferably one or more of vinyl ethylene carbonate, vinylene carbonate, and methylene vinyl carbonate; in a specific embodiment provided by the present invention, the amine compound is preferably one or more of amino alcohol, aminoethanol, aminopropanol, aminobutanol, aminobenzyl alcohol, aminoethylene glycol, aminopropylene glycol, aminopentanol, aminohexanol, aminocyclohexanol, aminobenzyl alcohol, and aminobenzaldehyde.

[0063] In a specific embodiment provided by the present invention, the amidated vinyl carbonate monomer is preferably prepared by the following method: mixing the vinyl group-containing carbonate and the amine compound in a solvent, then adding a base catalyst, and heating for reaction to obtain the amidated vinyl carbonate monomer; the molar ratio of the vinyl group-containing carbonate to the amine compound is preferably 1:1 to 1:2.5, more preferably 1:1.5 to 1:2.5, still more preferably 1:1.8 to 1:2.2, and most preferably 1:2; the solvent can be any organic solvent well-known to those skilled in the art without special limitations, and in the present invention, it is preferably N,N-dimethylformamide (DMF); the molar ratio of the vinyl group-containing carbonate to the solvent is preferably 1:5 to 1:10; the base catalyst can be any base catalyst well-known to those skilled in the art without special limitations, and in the present invention, it is preferably one or more of sodium bicarbonate, potassium carbonate, and triethylamine; the mass ratio of the base catalyst to the vinyl group-containing carbonate is preferably 0.2:1 to 1:1, more preferably 0.2:1 to 0.8:1, still more preferably 0.2:1 to 0.5:1; the reaction temperature is preferably 45°C to 80°C, more preferably 45°C to 60°C; the reaction time is preferably 2 to 5 h.

[0064] In a specific embodiment provided by the present invention, the amidated vinyl carbonate monomer is prepared specifically according to the following steps: Step 1) Mix the alkenyl-containing carbonate with a solvent to obtain a mixed solvent 1; Step 2) Mix the mixed solvent 1 with an amine compound to obtain a mixed solvent 2; Step 3) Mix the mixed solvent 2 with a base catalyst and heat for reaction to obtain the amidated vinyl carbonate monomer; wherein, the mixing speed in the step 1) is preferably 200-400 rpm; the mixing speed in the step 2) is preferably 200-400 rpm; the mixing time in the step 2) is preferably 2-3 h; the mixing speed in the step S3) is preferably 100-200 rpm; the reaction temperature in the step 3) is preferably 45°C-80°C, more preferably 45°C-60°C; the reaction time is preferably 2-5 h; after the reaction is completed, it is preferably cooled to room temperature, and the precipitate is washed with saturated brine and dried to obtain the amidated vinyl carbonate monomer.

[0065] According to the present invention, the amidated vinyl carbonate monomer preferably has the structure shown in formula (II):

[0066] Formula (II);

[0067] wherein, m is an integer from 0 to 10, preferably an integer from 0 to 8, more preferably an integer from 0 to 6, still more preferably an integer from 0 to 4, still more preferably an integer from 0 to 2, and most preferably 0.

[0068] R 2 is a substituted or unsubstituted C1-C10 alkylamino, a substituted or unsubstituted C6-C20 aromatic amino, a substituted or unsubstituted C6-C20 cycloalkylamino, a substituted or unsubstituted C2-C10 heterocyclic amino; the substituents in the substituted C1-C10 alkylamino, the substituted C6-C20 aromatic amino, the substituted C6-C20 cycloalkylamino and the substituted C2-C10 heterocyclic amino are one or more of C1-C5 alkyl, hydroxyl, C1-C5 aldehyde and C1-C5 hydroxyalkyl, preferably one or more of C1-C3 alkyl, hydroxyl, C1-C3 aldehyde and C1-C3 hydroxyalkyl, more preferably one or more of C1-C2 alkyl, hydroxyl, C1-C2 aldehyde and C1-C2 hydroxyalkyl.

[0069] In a specific embodiment provided by the present invention, R 2It is a substituted or unsubstituted C1-C8 alkylamino group, a substituted or unsubstituted C6-C15 aromatic amino group, a substituted or unsubstituted C6-C15 cycloalkylamino group, or a substituted or unsubstituted C2-C8 heterocyclic amino group; the substituents in the substituted C1-C8 alkylamino group, the substituted C6-C15 aromatic amino group, the substituted C6-C15 cycloalkylamino group, and the substituted C2-C8 heterocyclic amino group are one or more of a C1-C5 alkyl group, a hydroxyl group, a C1-C5 aldehyde group, and a C1-C5 hydroxyalkyl group, preferably one or more of a C1-C3 alkyl group, a hydroxyl group, a C1-C3 aldehyde group, and a C1-C3 hydroxyalkyl group, more preferably one or more of a C1-C2 alkyl group, a hydroxyl group, a C1-C2 aldehyde group, and a C1-C2 hydroxyalkyl group.

[0070] In a specific embodiment provided by the present invention, R 2 is a substituted or unsubstituted C1-C6 alkylamino group, a substituted or unsubstituted C6-C10 aromatic amino group, a substituted or unsubstituted C6-C10 cycloalkylamino group, or a substituted or unsubstituted C2-C6 heterocyclic amino group; the substituents in the substituted C1-C6 alkylamino group, the substituted C6-C10 aromatic amino group, the substituted C6-C10 cycloalkylamino group, and the substituted C2-C6 heterocyclic amino group are one or more of a C1-C5 alkyl group, a hydroxyl group, a C1-C5 aldehyde group, and a C1-C5 hydroxyalkyl group, preferably one or more of a C1-C3 alkyl group, a hydroxyl group, a C1-C3 aldehyde group, and a C1-C3 hydroxyalkyl group, more preferably one or more of a C1-C2 alkyl group, a hydroxyl group, a C1-C2 aldehyde group, and a C1-C2 hydroxyalkyl group.

[0071] In a specific embodiment provided by the present invention, the heteroatoms in the heterocycle can be heteroatoms well-known to those skilled in the art, without special limitations, and can be one or more of S, O, and N; the heterocycle can be an aromatic heterocycle or a non-aromatic heterocycle, without special limitations.

[0072] In a specific embodiment provided by the present invention, the R 2 is preferably one of the structures shown in formulas (1)-(6):

[0073] Formula (1); Formula (2); Formula (3);

[0074] Formula (4); Formula (5); Formula (6).

[0075] In a specific embodiment provided by the present invention, the mass of the amidated vinyl carbonate monomer is preferably 1% - 5% of the mass of the composite in-situ solidified electrolyte, more preferably 3% - 5%, still more preferably 4% - 5%, and most preferably 5%.

[0076] According to the present invention, the cross-linking agent includes a compound having the structure shown in formula (I):

[0077] Formula (I);

[0078] wherein, n is an integer from 1 to 10, and R 1 is an alkenyl group with 2 to 10 carbon atoms; optionally, n is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10; optionally, R 1 is an alkenyl group with 2 carbon atoms, an alkenyl group with 3 carbon atoms, an alkenyl group with 4 carbon atoms, an alkenyl group with 5 carbon atoms, an alkenyl group with 6 carbon atoms, an alkenyl group with 7 carbon atoms, an alkenyl group with 8 carbon atoms, an alkenyl group with 9 carbon atoms or an alkenyl group with 10 carbon atoms.

[0079] In a specific embodiment provided by the present invention, n is preferably 2 - 6, more preferably 2 - 5, still more preferably 2 - 4, and most preferably 3.

[0080] In a specific embodiment provided by the present invention, the R 1 is preferably an alkenyl group with 2 to 6 carbon atoms, more preferably an alkenyl group with 2 to 4 carbon atoms, and still more preferably a vinyl group.

[0081] In a specific embodiment provided by the present invention, the compound of the structure shown in formula (I) is prepared according to the following steps: reacting the compound shown in formula (IV) with the compound shown in formula (V) in the presence of a basic substance to obtain the compound of the structure shown in formula (I); the basic substance can be any basic substance well-known to those skilled in the art without special limitation, and in the present invention, it is preferably one or more of pyridine, potassium carbonate, triethylamine, sodium carbonate and potassium hydroxide; the molar ratio of the compound shown in formula (IV) to the compound shown in formula (V) is preferably (2-2.5):(1-1.5); the reaction is carried out under stirring; the stirring speed is preferably 100-300 rpm; in the present invention, it is preferred to first mix the compound shown in formula (IV) with the basic substance, and then add the compound shown in formula (V) for reaction to obtain the compound of the structure shown in formula (I); the mixing speed of the compound shown in formula (IV) and the basic substance is preferably 100-300 rpm; the mixing time of the compound shown in formula (IV) and the basic substance is preferably 0.2-1 h; the compound shown in formula (V) is preferably added under the condition of an ice-water bath; the reaction is preferably carried out at room temperature; the reaction time is preferably 15-30 h, more preferably 20-26 h, and still more preferably 24 h; after the reaction is completed, it is preferably washed with a dilute hydrochloric acid solution, then benzene is added for extraction, the obtained organic phase is washed with saturated brine, concentrated, and purified to obtain the compound of the structure shown in formula (I); the mass concentration of the dilute hydrochloric acid solution is preferably 3%-10%, more preferably 3%-8%, and still more preferably 5%; the purification is preferably column chromatography purification; the elution solvent used for the column chromatography purification is preferably n-hexane and dichloromethane; the volume ratio of n-hexane to dichloromethane is preferably 1:(1-3), more preferably 1:(1.5-2.5), and still more preferably 1:2.

[0082] Formula (IV); Formula (V);

[0083] Wherein, X is a halogen, preferably Cl or Br.

[0084] The present invention uses a sulfonate crosslinking agent to improve the high-temperature stability of the polymerized electrolyte, which can ensure that the structure does not change at high temperature and further reflects the kinetic advantages.

[0085] In a specific embodiment provided by the present invention, the crosslinking agent may further include one or more of bis(trimethylolpropane) tetraacrylate, ethoxylated trimethylolpropane triacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate and methylene bisacrylamide.

[0086] In a specific embodiment provided by the present invention, the mass of the crosslinking agent is preferably 0.5% to 2% of the mass of the composite in-situ solidified electrolyte, more preferably 0.5% to 1.5%, and still more preferably 0.5% to 1%.

[0087] According to the present invention, the electrolyte includes an organic solvent, a lithium salt, and an additive.

[0088] In a specific embodiment provided by the present invention, the organic solvent includes a carbonate solvent; the carbonate solvent preferably includes a cyclic carbonate solvent and / or a linear carbonate solvent, more preferably includes a cyclic carbonate solvent and a linear carbonate solvent; the mass ratio of the cyclic carbonate solvent to the linear carbonate solvent is preferably 1:(1 - 3), more preferably 1:(1.5 - 2.5), and still more preferably 1:2; the cyclic carbonate solvent is preferably ethylene carbonate (EC) and / or propylene carbonate (PC); the linear carbonate solvent is preferably one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), more preferably two of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC); the mass ratio of two of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) is preferably 1:1.

[0089] In a specific embodiment provided by the present invention, the organic solvent includes ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate; the mass ratio of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate is preferably 1:1:1.

[0090] In a specific embodiment provided by the present invention, the concentration of the lithium salt in the electrolyte is preferably 0.5 - 2 mol / L, more preferably 0.8 - 1.5 mol / L, and still more preferably 1 - 1.2 mol / L; the lithium salt can be a lithium salt well-known to those skilled in the art without special limitation. In the present invention, it is preferably lithium hexafluorophosphate (LiPF 6 )), lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) or one or more of them.

[0091] In a specific embodiment provided by the present invention, the mass of the additive is preferably 0.1% - 10% of the mass of the electrolyte; optionally, the mass of the additive is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the mass of the electrolyte, or a range between any two of the above values.

[0092] In a specific embodiment provided by the invention, the additive includes a nitrile additive; the nitrile additive preferably includes a compound represented by formula (III):

[0093] Formula (III);

[0094] Wherein, p and q are each independently an integer from 1 to 10, preferably an integer from 2 to 8, more preferably an integer from 2 to 6, still more preferably an integer from 2 to 4, and most preferably 2 or 3.

[0095] In a specific embodiment provided by the invention, the compound represented by formula (III) is prepared according to the following steps: reacting the compound represented by formula (VI) with malononitrile in a solvent by heating, and then removing the solvent to obtain the compound represented by formula (III); the solvent can be any organic solvent well-known to those skilled in the art without special limitation, and in the present invention, it is preferably one or more of tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and dichloromethane (CH 2 Cl 2 ); the temperature of the heating reaction is preferably 40°C to 50°C, more preferably 45°C; the time of the heating reaction is preferably 4 to 8 h; the heating reaction is preferably carried out under stirring; the stirring speed is preferably 50 to 200 rpm; the method for removing the solvent can be any method well-known to those skilled in the art without special limitation, and in the present invention, it is preferably vacuum rotary evaporation.

[0096] The present invention uses the nitrile material represented by formula (III) to be compounded with a sulfonate cross-linking agent and an amidated vinyl carbonate monomer, and the constructed composite in-situ solid electrolyte has excellent antioxidant properties and is compatible with high specific energy battery cell systems such as high-nickel and high-voltage lithium cobaltate.

[0097] In a specific embodiment provided by the invention, the nitrile additive preferably further includes one or more of succinonitrile, 1,3,6-hexanetricarbonitrile, trans-hexenedinitrile, 1,2-bis(cyanoethoxy)ethane, 3-(trimethylsilyloxy)propionitrile, and bis(cyanoethyl)sulfone.

[0098] In a specific embodiment provided by the invention, the mass of the nitrile additive is preferably 0.1% to 5% of the mass of the electrolyte; optionally, the mass of the nitrile additive is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% of the mass of the electrolyte, or the range between any two of the above values. In some embodiments provided by the present invention, the mass of the nitrile additive is specifically 2% of the mass of the electrolyte.

[0099] In a specific embodiment provided by the present invention, the additive preferably further comprises one or more of sulfonate compounds, sulfate compounds, fluorinated additives, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, and fluorinated lithium salt compounds; the fluorinated additive is preferably one or more of fluoroethylene carbonate, trifluoropropylene carbonate, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether; the sulfonate compound is preferably one or more of 1,3-propane sultone, 1,4-butane sultone, methylene methanedisulfonate, and 1,3-propene sultone; the sulfate compound is preferably one or more of ethylene sulfate, trimethylene cyclic sulfate, vinyl methyl sulfate, 4,4'-bis(vinyl sulfate), and propylene sulfite; the unsaturated cyclic carbonate compound is preferably vinylene carbonate and / or vinyl ethylene carbonate; the borate compound is preferably one or more of trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, and triphenyl borate; the trimethylsilyl ester compound is preferably one or more of tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, and tris(trimethylsilyl) trifluoromethanesulfonate; the fluorinated lithium salt compound is preferably lithium difluorophosphate.

[0100] In a specific embodiment provided by the present invention, the mass of the sulfonate compound is preferably 0.1% to 3% of the mass of the electrolyte; optionally, the mass of the sulfonate compound is 0.1%, 0.3%, 0.5%, 0.7%, 1%, 1.5%, 2%, 2.5%, 3% of the mass of the electrolyte, or a range between any two of the above values.

[0101] In a specific embodiment provided by the present invention, the mass of the sulfate compound is preferably 0.1% to 3% of the mass of the electrolyte; optionally, the mass of the sulfate compound is 0.1%, 0.3%, 0.5%, 0.7%, 1%, 1.5%, 2%, 2.5%, 3% of the mass of the electrolyte, or a range between any two of the above values.

[0102] In a specific embodiment provided by the present invention, the mass of the fluorinated additive is preferably 0.1% to 5% of the mass of the electrolyte; optionally, the mass of the fluorinated additive is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% of the mass of the electrolyte, or a range between any two of the above values.

[0103] In a specific embodiment provided by the present invention, the mass of the unsaturated cyclic carbonate compound is preferably 0% to 3% of the mass of the electrolyte; optionally, the mass of the unsaturated cyclic carbonate compound is 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% of the mass of the electrolyte, or in the range between any two of the above values.

[0104] In a specific embodiment provided by the present invention, the mass of the borate compound is preferably 0% to 3% of the mass of the electrolyte; optionally, the mass of the borate compound is 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% of the mass of the electrolyte, or in the range between any two of the above values.

[0105] In a specific embodiment provided by the present invention, the mass of the trimethylsilyl ester compound is preferably 0% to 3% of the mass of the electrolyte; optionally, the mass of the trimethylsilyl ester compound is 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% of the mass of the electrolyte, or in the range between any two of the above values.

[0106] In a specific embodiment provided by the present invention, the mass of the fluorinated lithium salt compound is preferably 0% to 3% of the mass of the electrolyte; optionally, the mass of the fluorinated lithium salt compound is 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% of the mass of the electrolyte, or in the range between any two of the above values.

[0107] In a specific embodiment provided by the present invention, the electrolyte is preferably prepared according to the following steps: Step 1) adding a lithium salt to an organic solvent and mixing to obtain a mixed solvent 1; Step 2) mixing the mixed solvent 1 with an additive to obtain the electrolyte; the mixing speed in Step 1) is preferably 400 to 800 rpm, more preferably 400 to 600 rpm; the mixing speed in Step 2) is preferably 400 to 800 rpm, more preferably 400 to 600 rpm.

[0108] According to the present invention, the initiator can be an initiator well-known to those skilled in the art without special limitations. In the present invention, an azo initiator is preferably used, and more preferably azobisisobutyronitrile (AIBN).

[0109] In a specific embodiment provided by the present invention, the mass of the initiator is preferably 0.01% to 0.3% of the mass of the composite in-situ solidified electrolyte, more preferably 0.01% to 0.2%, still more preferably 0.01% to 0.1%, and most preferably 0.01% to 0.05%.

[0110] The present invention also provides a method for preparing the above-mentioned composite in-situ solidified electrolyte, which specifically includes: mixing a polymerization monomer, a cross-linking agent, an initiator and an electrolyte to obtain a precursor of the composite in-situ solidified electrolyte; injecting the precursor of the composite in-situ solidified electrolyte into a semi-finished secondary lithium battery for reaction to obtain the composite in-situ solidified electrolyte; the semi-finished secondary lithium battery includes a positive electrode, a negative electrode and a separator.

[0111] The present invention also provides a secondary lithium battery, including the above-mentioned composite in-situ solidified electrolyte.

[0112] In a specific embodiment provided by the present invention, the secondary lithium battery further includes a positive electrode, a negative electrode and a separator.

[0113] In a specific embodiment provided by the present invention, the positive electrode preferably includes a positive electrode current collector and a positive electrode active layer provided on the surface of the positive electrode current collector; the positive electrode active layer includes a positive electrode active material, a conductive agent and a binder; the positive electrode active material can be an active material well-known to those skilled in the art without special limitations. In the present invention, it is preferably one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide and lithium nickel manganese oxide, more preferably NCM811, NCM523, NCM613, 4.53VLCO, 4.6VLCO or LNMO; the conductive agent can be a conductive agent well-known to those skilled in the art without special limitations. In the present invention, it is preferably conductive carbon black (SuperP) and / or carbon nanotubes, more preferably conductive carbon black and carbon nanotubes; the mass ratio of the conductive carbon black to the carbon nanotubes is preferably (6-8):(7-9), more preferably 7:8; the binder can be a binder well-known to those skilled in the art without special limitations. In the present invention, it is preferably polyvinylidene fluoride (PVDF); the mass ratio of the positive electrode active material, the conductive agent and the binder is preferably 95-98:1-2:1-2, more preferably 96-98:1.5:1.5.

[0114] In a specific embodiment provided by the present invention, the negative electrode preferably includes a negative electrode current collector and a negative electrode active layer provided on the surface of the negative electrode current collector; the negative electrode active layer includes a negative electrode active material, a negative electrode conductive agent and a negative electrode binder; the negative electrode active material can be a negative electrode active material well-known to those skilled in the art without special limitations. In the present invention, it is preferably graphite, more preferably artificial graphite; the negative electrode conductive agent is preferably conductive carbon black (SuperP) and / or carbon nanotubes; the negative electrode binder is preferably sodium carboxymethyl cellulose and / or styrene-butadiene rubber, more preferably sodium carboxymethyl cellulose and styrene-butadiene rubber; the mass ratio of the sodium carboxymethyl cellulose to the styrene-butadiene rubber is preferably (1-2):(2-3), more preferably 1.5:2.5; the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is preferably (94-96):1:(3-5), more preferably 95:1:4.

[0115] The separator can be a separator well-known to those skilled in the art without any special limitation. In the present invention, a polyethylene separator coated with alumina on one side is preferably used, and it is left standing in a drying room with a dew point of -35°C for 72 hours before use.

[0116] In order to further illustrate the present invention, a composite in-situ solidified electrolyte and a secondary lithium battery provided by the present invention will be described in detail below in conjunction with embodiments.

[0117] All the reagents used in the following examples are commercially available.

[0118] Example 1

[0119] 1.1 Synthesis of nitrile electrolyte material C 10 H 14 N 2

[0120]

[0121] Heptanone and ethanedinitrile are added to DMF in a molar ratio of 1:1 to obtain a mixed solvent 1;

[0122] The mixed solvent 1 is placed in a water bath at 45°C and stirred constantly at a constant speed of 150 rpm for 4 hours to obtain a mixed solvent 2;

[0123] The mixed solvent 2 is subjected to vacuum rotary evaporation in a water bath at 60°C to obtain a light yellow final product.

[0124] The obtained product is analyzed by gas chromatography - mass spectrometry, and the result is GCMS (m / z): calcd.for C 10 H 14 N 2 , 162.12, found 162.76.

[0125] 1.2 Synthesis of alkenesulfonate crosslinking agent

[0126]

[0127] Add 2 mol of styrenesulfonyl chloride and 300 mL of pyridine into a three-necked flask, stir at a speed of 100 rpm for 1 h, then slowly add 1 moL of propylene glycol into the three-necked flask under an ice-water bath condition, and react at room temperature for 24 h; add 400 mL of 5% HCl solution to wash the product, repeat three times; add 400 mL of benzene for extraction, repeat three times; wash the obtained organic phase with saturated brine three times; use an appropriate amount of anhydrous magnesium sulfate to remove water and perform suction filtration; rotary evaporate and concentrate the obtained liquid; purify by column chromatography using a mixed solvent of n-hexane and dichloromethane (volume ratio 1:2) to obtain the final product p-styrenesulfonate.

[0128] Analyze the p-styrenesulfonate obtained in 1.2 by nuclear magnetic resonance, and obtain its nuclear magnetic resonance hydrogen spectrum as shown in Figure 1 shown.

[0129] 1.3 Synthesis of amidated vinyl carbonate monomer

[0130]

[0131] Step 1: In a three-necked flask, pour an appropriate amount of vinyl ethylene carbonate monomer (VEC) into DMF (the molar ratio of DMF to VEC is 5:1), stir at a speed of 200 rpm until uniform to obtain mixed solvent 1.

[0132] Step 2: Add the amino reagent aminobutane to mixed solvent 1, the molar ratio of the amino reagent to vinyl ethylene carbonate is 2:1, stir at a speed of 200 rpm for 2 h to obtain mixed solvent 2.

[0133] Step 3: Add sodium bicarbonate to mixed solvent 2, the mass ratio of sodium bicarbonate to vinyl ethylene carbonate is 0.2:1, seal the three-necked flask, and place it in a water bath at 45 °C to heat, stir at a speed of 100 rpm for 2 h to obtain mixed solvent 3.

[0134] Step 4: Cool mixed solvent 3 to room temperature to obtain the final white precipitate. Wash the obtained product with saturated brine three times, and use an appropriate amount of anhydrous magnesium sulfate to remove water and vacuum dry to obtain the final product.

[0135] Analyze the product obtained in 1.3 by gas chromatography-mass spectrometry, and obtain the result GCMS (m / z): calcd. for C 14 H 26 O 4 N 2 , 286.19, found 285.79.

[0136] 1.4 Preparation of in-situ solidified electrolyte precursor

[0137] Step 1: Add 1 mol / L LiFSi to the solvent of EC:DEC:EMC = 1:1:1 in multiple portions, and stir at a speed of 400 rpm until completely dissolved to obtain mixed solvent 1.

[0138] Step 2: Add 3 wt% fluoroethylene carbonate (FEC), 1 wt% vinyl sulfate additive ethylene sulfate, 1 wt% 1,3 - propane sultone and 2 wt% nitrile - based electrolyte material C 10 H 14 N 2 to mixed solvent 1, and stir at a speed of 400 rpm until completely dissolved to obtain mixed solvent 2.

[0139] Step 3: Add 0.5 wt% of the alkenesulfonate cross - linker obtained in 1.2, 5 wt% of the amidated vinyl carbonate monomer obtained in 1.3, and 0.01 wt% of the initiator AIBN to mixed solvent 1, and stir evenly at a speed of 400 rpm to obtain an in - situ solidified electrolyte precursor.

[0140] 1.5 Preparation of secondary lithium batteries

[0141] Preparation of the positive electrode sheet: Weigh and mix the positive electrode material 8 - series nickel cobalt manganese lithium oxide (NCM811), conductive agent carbon black (SuperP), carbon nanotubes (CNT, an NMP solution with a mass fraction of 5%), and binder polyvinylidene fluoride (PVDF, an NMP solution with a mass fraction of 5%) according to a mass ratio of 97:0.7:0.8:1.5. After mixing, add an appropriate amount of NMP to control the theoretical solid content to 65%, and homogenize using a planetary homogenizer to obtain a positive electrode paste. Then evenly coat the positive electrode paste on an aluminum foil with a thickness of 13 μm, and after drying, rolling, and cutting, obtain a 50 mm×70 mm positive electrode sheet (surface density 320 g / m 2 , compaction density 3.2 g / cm 3 )

[0142] Preparation of the separator: Use a polyethylene separator with single - sided alumina coating as the separator, and let it stand in a drying room with a dew point of - 35°C for 72 h before use.

[0143] Preparation of the negative electrode sheet: The negative electrode material artificial graphite (specific capacity 355 mAh·g -1), the conductive agent SuperP, the thickening agent sodium carboxymethyl cellulose (CMC, deionized water solution with a solid content of 1.5%), and the binder styrene-butadiene rubber (SBR, deionized water solution with a solid content of 48%) are mixed in a mass ratio of 95:1:1.5:2.5. After mixing, deionized water is added to control the theoretical solid content to 52%. The anode slurry is obtained by homogenization using a planetary homogenizer, and the anode slurry is uniformly coated on a 17-μm-thick copper foil. After drying, rolling, and cutting, a 52 mm×72 mm anode plate (surface density 200 g / m 2 , and the tap density is 1.6 g / cm 3 ). The N / P ratio of the positive and negative electrodes is 1.1.

[0144] Preparation of the battery: The battery is made in a drying room with an environmental dew point ≤ -35°C. The separator is folded in a Z shape, and the positive electrode plate and the negative electrode plate are placed on each side. There are 12 layers of positive electrode plates and 13 layers of negative electrode plates. The positive electrode, separator, and negative electrode are stacked in sequence and aligned to obtain an electrode group. Then, the electrode group is fixed with polyimide tape and the tabs are welded. Subsequently, it is placed in an aluminum-plastic film, and then vacuum baked at 90°C for 12 h. After cooling, the prepared in-situ solidified electrolyte precursor is injected. Finally, after vacuum packaging, high-temperature infiltration, formation, aging, secondary sealing, and grading, an experimental battery 1 with a capacity of about 2.5 Ah is obtained. Among them, the high-temperature infiltration is at 45°C for 24 h; the formation process is charging at 0.1C to 3.4V and then charging at 0.3C to 3.9V; the aging process is standing at 45°C for 24 h; the secondary sealing process is vacuum secondary sealing; the grading process is: charging at 0.1C to 4.2V and discharging at 0.33C to 3V.

[0145] Example 2

[0146] The difference in the preparation process from Example 1 is that the amino reagent in step 2 of the synthesis of the amidated vinyl carbonate monomer is replaced with n-propylamine.

[0147]

[0148] The obtained product is analyzed by gas chromatography-mass spectrometry, and the result is GCMS (m / z): calcd.for C 13 H 24 O 3 N 2 , 256.18, found 257.11.

[0149] The preparation process of the secondary lithium battery is the same as that of Example 1.

[0150] Example 3

[0151] The difference in the preparation process from Example 1 lies in that: in the synthesis of the amidated vinyl carbonate monomer, the amino reagent in Step 2 is replaced with methanolamine, and in Step 3 of the preparation of the in-situ solidified electrolyte precursor, the initiator is replaced with BPO.

[0152]

[0153] The obtained product was analyzed by gas chromatography-mass spectrometry, and the result was GCMS (m / z): calcd. for C 8 H 14 O 4 N 2 , 202.10, found 200.97.

[0154] The preparation process of the secondary lithium battery is the same as that of Example 1.

[0155] Example 4

[0156] The difference in the preparation process from Example 1 lies in that: in the synthesis of the amidated vinyl carbonate monomer, the amino reagent in Step 2 is replaced with 2-aminopentane.

[0157]

[0158] The obtained product was analyzed by gas chromatography-mass spectrometry, and the result was GCMS (m / z): calcd. for C 16 H 30 O 4 N 2 , 314.22, found 315.22.

[0159] The preparation process of the secondary lithium battery is the same as that of Example 1.

[0160] Example 5

[0161] The difference in the preparation process from Example 1 lies in that: in the synthesis of the amidated vinyl carbonate monomer, the amino reagent in Step 2 is replaced with 3-aminopentane.

[0162]

[0163] The obtained product was analyzed by gas chromatography-mass spectrometry, and the result was GCMS (m / z): calcd. for C 16 H 30 O 4 N 2 , 314.22, found 316.21.

[0164] The preparation process of the secondary lithium battery is the same as that of Example 1.

[0165] Example 6

[0166] The difference in the preparation process from Example 1 is that the amino reagent in Step 2 of the synthesis of the amidated vinyl carbonate monomer is replaced with n-hexylamine.

[0167]

[0168] The obtained product was analyzed by gas chromatography-mass spectrometry, and the results were GCMS (m / z): calcd. for C 18 H 34 O 4 N 2 , 342.25, found 340.62.

[0169] The preparation process of the secondary lithium battery is the same as that of Example 1.

[0170] Comparative Example 1

[0171] The vinyl sulfonate crosslinking agent in Example 1 was replaced with an amide-type crosslinking agent N,N'-methylenebisacrylamide. The rest remained unchanged.

[0172] The preparation process of the secondary lithium battery is the same as that of Example 1.

[0173] Comparative Example 2

[0174] The amidated vinyl carbonate monomer in Example 1 was replaced with methacrylate, and the crosslinking agent was replaced with bis(tris(hydroxymethyl)propane) tetraacrylate. The rest remained unchanged.

[0175] The preparation process of the secondary lithium battery is the same as that of Example 1.

[0176] The secondary lithium batteries prepared in Examples 1 to 6 and Comparative Examples 1 to 2 were subjected to 1C / 1C cycle tests, and the comparative diagram of the cycle performance was obtained as shown in Figure 2 shown; Figure 2 The enlarged view of area A in Figure 3 shown; Figure 2 The enlarged view of area B in Figure 4 shown.

[0177] From Figure 2 the cycle performance data in, it can be seen that the in-situ solid-state electrolyte using styrene sulfonate and amidated vinyl carbonate can effectively improve the cycle life of the secondary lithium battery. At a rate of 1C / 1C at room temperature for 500 cycles, the capacity retention rate can reach more than 96%.

[0178] In Comparative Example 1 without using a styrene sulfonate crosslinker, rapid attenuation occurred in the initial stage of cycling, and the capacity decayed to less than 85% after 400 cycles. This was because the ionic conductivity decreased significantly after the amidated vinyl carbonate was crosslinked with the highly functional bis(tris(hydroxymethyl)propane) tetraacrylate, unable to meet the requirements of normal cycling of the battery cell. After replacing the amidated vinyl carbonate monomer with an acrylate monomer, the capacity showed a significant attenuation. The capacity decreased by 11.5% compared with Example 1 after 500 cycles. This was because the antioxidant ability of the acrylate monomer was average, and it was prone to oxidative decomposition when applied to the ternary lithium cathode with strong oxidizing property, continuously consuming active lithium and continuously generating CEI on the surface of the cathode particles, all of which would lead to the attenuation of the cycling capacity.

[0179] In Comparative Example 2, a methacrylate monomer was used. This monomer was easily oxidized by the high-nickel cathode and would continuously decompose at the cathode during the battery formation and cycling processes, resulting in the attenuation of the cycling performance.

[0180] Using a styrene sulfonate crosslinker and an amidated vinyl carbonate monomer can construct an in-situ solid electrolyte with oxidation resistance and fast ion conduction. By regulating the polymer structure with the styrene sulfonate crosslinker, the mechanical properties of the polymer structure can be increased. At the same time, as a functional group with strong electron-withdrawing ability, the amide group can effectively improve the antioxidant ability and ion conduction ability, thus achieving stable cycling in the ternary system.

[0181] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A composite in-situ solid-state electrolyte, characterized in that: It is formed by polymerization of monomers and cross-linking agents in electrolyte via initiator; The polymerizable monomers include amidated vinyl carbonate monomers; The amidated vinyl carbonate monomer is formed from an olefin-containing carbonate and an amine compound; The cross-linking agent includes a compound having a structure shown in formula (I): Formula (I); Wherein, n is an integer of 1 to 10, and R1 is selected from C2 to C10 alkenyl.

2. The composite in-situ solid-state electrolyte according to claim 1, characterized in that: The alkenyl-containing carbonate is selected from one or more of vinyl carbonate, vinylene carbonate and methylene carbonate; And / or, the amine compound is selected from one or more of amino alcohol, aminoethanol, aminopropanol, aminobutanol, aminobenzyl alcohol, aminoethylene glycol, aminopropylene glycol, aminopentanol, aminohexanol, aminocyclohexanol, aminobenzyl alcohol and aminobenzaldehyde.

3. The composite in-situ solid-state electrolyte according to claim 1, characterized in that: The amidated vinyl carbonate monomer has a structure shown in formula (II): Formula (II); Wherein, m is an integer of 0 to 10, and R2 is selected from substituted or unsubstituted C1 to C10 alkylamino groups, substituted or unsubstituted C6 to C20 aromatic amine groups, substituted or unsubstituted C6 to C20 cycloalkylamine groups, and substituted or unsubstituted C2 to C10 heterocyclic amine groups; The substituents in the substituted C1-C10 alkylamino group, the substituted C6-C20 aromatic amine group, the substituted C6-C20 cycloalkylamine group and the substituted C2-C10 heterocyclic amine group are selected from one or more of C1-C5 alkyl groups, hydroxyl groups, C1-C5 aldehyde groups and C1-C5 hydroxyalkyl groups.

4. The composite in-situ solid-state electrolyte according to claim 3, characterized in that: The R2 is selected from one of the structures shown in formula (1) to formula (6): Formula (1); Formula (2); Formula (3); Formula (4); Formula (5); Formula (6).

5. The composite in-situ solid-state electrolyte according to claim 1, characterized in that: The electrolyte includes an organic solvent, a lithium salt and an additive; The organic solvent includes a carbonate solvent; The concentration of the lithium salt in the electrolyte is 0.5-2 mol / L; The additive includes a nitrile additive; the nitrile additive includes a compound represented by formula (III): Formula (III); Wherein, p and q are each independently selected from integers of 1 to 10.

6. The composite in-situ solid-state electrolyte according to claim 5, characterized in that: The nitrile additives also include one or more of succinonitrile, 1,3,6-hexanetricarbonitrile, trans-hexenedinitrile, 1,2-bis(cyanoethoxy)ethane), 3-(trimethylsilyloxy)propionitrile and bis(cyanoethyl)sulfone; And / or, the additive further includes one or more of sulfonate compounds, sulfate compounds, fluorinated additives, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds and fluorine-containing lithium salt compounds; And / or, the mass of the additive is 0.1% to 6% of the mass of the electrolyte.

7. The composite in-situ solid-state electrolyte according to claim 6, characterized in that: The fluorinated additive is selected from one or more of fluoroethylene carbonate, trifluoropropylene carbonate, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; And / or, the sulfonate compound is selected from one or more of 1,3-propane sultone, 1,4-butane sultone, methylene disulfonate and 1,3-propylene sultone; And / or, the sulfate compound is selected from one or more of vinyl sulfate, trimethylene cyclosulfate, vinyl methyl sulfate, 4,4'-vinyl sulfate and propylene sulfite; and / or, the unsaturated cyclic carbonate compound is selected from vinylene carbonate and / or vinyl ethylene carbonate; And / or, the borate ester compound is selected from one or more of trimethyl borate, triethyl borate, tripropyl borate, tributyl borate and triphenyl borate; And / or, the trimethylsilyl ester compound is selected from one or more of tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite and tris(trimethylsilyl)trifluoromethanesulfonate; And / or, the fluorine-containing lithium salt compound is selected from lithium difluorophosphate.

8. The composite in-situ solid-state electrolyte according to claim 1, characterized in that: The mass of the amidated vinyl carbonate monomer is 1% to 5% of the mass of the composite in-situ solid-state electrolyte; And / or, the mass of the cross-linking agent is 0.5% to 2% of the mass of the composite in-situ solid-state electrolyte; And / or, the mass of the initiator is 0.01% to 0.3% of the mass of the composite in-situ solid-state electrolyte.

9. The composite in-situ solid-state electrolyte according to claim 1, characterized in that: The amidated vinyl carbonate monomer is prepared according to the following method: The alkenyl-containing carbonate and the amine compound are mixed in a solvent, and then a base catalyst is added and heated to react to obtain an amidated vinyl carbonate monomer.

10. A secondary lithium battery, characterized in that: Comprising the composite in-situ solid-state electrolyte according to any one of claims 1 to 9.

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