A semi-interpenetrating polymer network (SIPN) electrolyte, comprising the following raw materials: poly(vinylidene fluoride-co-hexafluoropropylene), a diallyl compound, a crosslinking agent, a plasticizer, a photoinitiator, and a lithium salt; wherein the poly(vinylidene fluoride-co-hexafluoropropylene), the diallyl compound, the crosslinking agent, the plasticizer, and the photoinitiator are at a mass ratio of::::; the lithium salt and the SIPN electrolyte are at a mass ratio of 1:; the diallyl compound has a structure shown in Formula 1: wherein n is a positive integer;a preparation method of the diallyl compound comprises the following steps: mixing N,N'-carbonyldiimidazole, N,N'-diisopropylethylamine, and polyethylene glycol monomethyl ether with a first organic solvent to allow first elimination to obtain a terminal methylimidazole-based polyethylene oxide; and mixing the terminal methylimidazole-based polyethylene oxide and 2,2-bis(allyloxymethyl)-1-butanol (containing mono- and tri-substituted products) with a second organic solvent to allow second elimination to obtain the diallyl compound; wherein the crosslinking agent is one or more selected from the group consisting of pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetrakis(2-mercaptoacetate); and a preparation method of the SIPN electrolyte comprises the following steps: mixing the poly(vinylidene fluoride-co-hexafluoropropylene), the lithium salt, the diallyl compound, the crosslinking agent, the plasticizer, and the photoinitiator with an organic solvent to obtain a precursor solution; and forming a film from the precursor solution, and subjecting the film to ultraviolet irradiation to obtain the SIPN electrolyte. the poly(vinylidene fluoride-co-hexafluoropropylene), the diallyl compound, the crosslinking agent, the plasticizer, and the photoinitiator are at a mass ratio of::::; the lithium salt and the SIPN electrolyte are at a mass ratio of 1:; the diallyl compound has a structure shown in Formula 1: wherein n is a positive integer;a preparation method of the diallyl compound comprises the following steps: mixing N,N'-carbonyldiimidazole, N,N'-diisopropylethylamine, and polyethylene glycol monomethyl ether with a first organic solvent to allow first elimination to obtain a terminal methylimidazole-based polyethylene oxide; and mixing the terminal methylimidazole-based polyethylene oxide and 2,2-bis(allyloxymethyl)-1-butanol (containing mono- and tri-substituted products) with a second organic solvent to allow second elimination to obtain the diallyl compound; wherein the crosslinking agent is one or more selected from the group consisting of pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetrakis(2-mercaptoacetate); and a preparation method of the SIPN electrolyte comprises the following steps: mixing the poly(vinylidene fluoride-co-hexafluoropropylene), the lithium salt, the diallyl compound, the crosslinking agent, the plasticizer, and the photoinitiator with an organic solvent to obtain a precursor solution; and forming a film from the precursor solution, and subjecting the film to ultraviolet irradiation to obtain the SIPN electrolyte. mixing N,N'-carbonyldiimidazole, N,N'-diisopropylethylamine, and polyethylene glycol monomethyl ether with a first organic solvent to allow first elimination to obtain a terminal methylimidazole-based polyethylene oxide; and mixing the terminal methylimidazole-based polyethylene oxide and 2,2-bis(allyloxymethyl)-1-butanol (containing mono- and tri-substituted products) with a second organic solvent to allow second elimination to obtain the diallyl compound; wherein the crosslinking agent is one or more selected from the group consisting of pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetrakis(2-mercaptoacetate); and a preparation method of the SIPN electrolyte comprises the following steps: mixing the poly(vinylidene fluoride-co-hexafluoropropylene), the lithium salt, the diallyl compound, the crosslinking agent, the plasticizer, and the photoinitiator with an organic solvent to obtain a precursor solution; and forming a film from the precursor solution, and subjecting the film to ultraviolet irradiation to obtain the SIPN electrolyte. mixing the poly(vinylidene fluoride-co-hexafluoropropylene), the lithium salt, the diallyl compound, the crosslinking agent, the plasticizer, and the photoinitiator with an organic solvent to obtain a precursor solution; and forming a film from the precursor solution, and subjecting the film to ultraviolet irradiation to obtain the SIPN electrolyte.