Gel electrolyte suitable for silicon-based negative electrode or lithium metal negative electrode and battery

Abstract

The invention relates to the technical field of batteries, in particular to a gel electrolyte suitable for a silicon-based negative electrode or a lithium metal negative electrode and a battery. The gel electrolyte is formed by thermal initiation of a prepolymerization solution at 45-80 DEG C; the prepolymerization liquid comprises an electrolyte, monomers and an initiator, the monomers comprise a vinyl siloxane monomer, a long-chain fluorine-containing alkane monomer and an epoxy olefin copolymer, the carbon atom number of the long-chain fluorine-containing alkane monomer is not less than 6, and the long-chain fluorine-containing alkane monomer comprises an epoxy group. According to the invention, the prepolymerization liquid containing the specific monomer forms the GPEs through thermal initiation, and the GPEs are high in lithium ion transference number, good in normal-temperature and high-temperature cycle performance and excellent in electrochemical performance; meanwhile, the GPEs have better compatibility with a silicon-based negative electrode and lithium metal, and the GPEs are in tight contact with an electrode interface due to the strong adsorption characteristic of Si-O bonds; and the electrolyte is uniformly bound in the three-dimensional latticed framework of the GPEs, so that the safety performance is high.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more particularly to a gel electrolyte and battery suitable for silicon-based or lithium metal anodes. Background Technology

[0002] Using silicon-based anodes (4200 mAh / g, pure silicon) and lithium metal (3860 mAh / g) with extremely high specific capacity as anodes is a promising approach for developing next-generation high energy density (>400 Wh / kg) anodes. -1 This is an important research direction for batteries. Currently, traditional electrolytes using carbonate as a solvent have poor compatibility with silicon-based anodes and lithium metal, resulting in problems such as low coulombic efficiency, disordered lithium dendrite growth, and poor rate charge / discharge performance. To solve these problems, the design of novel electrolytes has become one of the key strategies.

[0003] Gel semi-solid electrolytes (GPEs) are formed by adding monomers and initiators to existing liquid electrolytes and polymerizing them in situ under specific initiation conditions to form gel polymer electrolytes with good flexibility, good interfacial contact, high ionic conductivity and non-flammability. They are an effective way to improve the electrochemical performance and safety of high-energy-density batteries.

[0004] Patent document CN120999108A ​​discloses a gel electrolyte prepolymer solution and a lithium battery. The prepolymer solution contains an electrolyte, a crosslinking monomer, an initiator, and a fluorocarbon surfactant, wherein the fluorocarbon surfactant contains a perfluoroalkyl chain C. n F 2n+1 Wherein, n≥6, the crosslinking monomer is selected from at least one of ethylene monomers, acrylic monomers, acrylate monomers, acrylamide monomers, epoxy monomers, halogenated ethylene monomers, siloxane monomers and their derivatives; the active material of the negative electrode in the lithium battery is a silicon-carbon composite material. This prior art provides a gel electrolyte suitable for silicon-carbon composite negative electrodes, but it is still not suitable for pure silicon negative electrodes or lithium metal negative electrodes, which have higher requirements for electrolytes. For example, pure silicon negative electrodes experience greater volume changes during charging and discharging, which leads to repeated rupture and regeneration of the SEI film, consuming lithium ions and electrolyte; another example is that lithium metal negative electrodes are prone to forming lithium dendrites; these two types of negative electrodes have higher requirements for electrolytes, requiring better interface stability and lithium ion migration ability. Summary of the Invention

[0005] The present invention aims to solve the above problems by providing a gel electrolyte and battery with excellent electrochemical performance, good interfacial contact with the electrode, high safety performance, and applicable to silicon-based anodes (especially pure silicon anodes) or lithium metal anodes.

[0006] The technical solution to the problem of the present invention is, in a first aspect, to provide a gel electrolyte suitable for silicon-based anodes or lithium metal anodes, wherein the gel electrolyte is formed by thermal initiation of a prepolymer solution at 45~80°C; the prepolymer solution includes an electrolyte, a monomer and an initiator, wherein the monomer includes vinylsiloxane monomers, long-chain fluorinated alkane monomers, and epoxy olefin copolymers, wherein the long-chain fluorinated alkane monomers have not less than 6 carbon atoms and include epoxy groups.

[0007] In this invention, a prepolymer liquid containing specific monomers is thermally initiated to form GPEs. These GPEs exhibit high lithium-ion transference numbers, good cycling performance at both room temperature (25°C) and high temperature (45°C), and excellent electrochemical performance. Furthermore, these GPEs demonstrate good compatibility with silicon-based anodes and lithium metal, and the strong adsorption properties of the Si-O bonds ensure close contact between the GPEs and the electrode interface. Moreover, the electrolyte is uniformly confined within the three-dimensional mesh-like framework of the GPEs, resulting in high safety performance.

[0008] Firstly, in this invention Using vinylsiloxane monomers as one of the polymerization monomers, the Si-O bond energy is high and the polarity is weak. Its polymer segments are similar to Li. + The interaction between them is a weak coordination effect, which reduces the Li + The binding energy, which is beneficial to Li + Rapid migration; in addition, the Si-O bond has excellent stability and flexibility, which helps to achieve a tighter and more stable bond between GPEs and the positive and negative electrode interfaces.

[0009] Preferably, the vinylsiloxane monomer contains 2 to 4 Si-O-Si bonds, including terminal vinyl groups. Terminal reactive vinyl groups facilitate crosslinking polymerization of the monomer, and the number of Si-O-Si bonds influences the Li... + Its mobility and compatibility with adsorption on silicon-based or lithium metal anodes.

[0010] Therefore, preferably, the vinylsiloxane monomer is selected from at least one of 1,7-divinyl-octamethyltetrasiloxane, 1,5-divinyl-hexamethyltrisiloxane, 1,3,5-trivinyl-1,1,3,5,5-pentamethyltrisiloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, and tris(vinyldimethylsiloxy)methylsilane.

[0011] In vinylsiloxane monomers, the topological structure of the siloxane segments is generally unrestricted and can be linear, branched, or cyclic. Preferably, the siloxane segment topological structure is linear. With the same number of Si-O-Si bonds, the vinyl activity is relatively mild, allowing the reaction to proceed more smoothly and controllably, which helps to form a uniform, defect-free crosslinked network. Furthermore, the flexible Si-O-Si segments in the middle help improve the elasticity and toughness of the crosslinked network, avoiding the impact of rigidity on ion mobility. Cyclic structures, on the other hand, suffer from steric hindrance, and branched structures have more complex crosslinking processes.

[0012] Therefore, more preferably, the vinylsiloxane monomer is selected from at least one of 1,7-divinyl-octamethyltetrasiloxane and 1,5-divinyl-hexamethyltrisiloxane.

[0013] More preferably, the vinylsiloxane monomer is 1,7-divinyl-octamethyltetrasiloxane. Appropriately increasing the length of the Si-O-Si chain segment is beneficial for improving ionic conductivity, but excessively long chains will lead to a significant decrease in mechanical strength.

[0014] Furthermore, the amount of vinylsiloxane monomers used in polymerization affects the electrolyte and battery performance. For example, excessive use may affect the flowability and uniformity of the prepolymer solution, while insufficient use may affect the density of GPEs and their adsorption compatibility with the electrodes. Preferably, the vinylsiloxane monomers account for 2wt% to 6wt% of the mass of the prepolymer solution. Examples include 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, and 6wt%.

[0015] Secondly, in this invention The introduction of long-chain fluorinated alkanes further enhances the overall Li content in GPEs. + It enhances the migration ability of GPEs; in addition, it can effectively broaden the electrochemical stability window of GPEs, enhance the high voltage resistance of GPEs, and the -CF2- group also significantly improves the non-flammability of GPEs.

[0016] The long-chain fluorinated alkane monomers have at least 6 carbon atoms and include epoxy groups. The epoxy groups are used for copolymerization with epoxy olefin copolymers. The long chain is beneficial for constructing microphase separation structures to improve electrochemical stability.

[0017] As a preferred embodiment of the present invention, the long-chain fluorinated alkane monomer has 6 to 13 carbon atoms. Excessively long chains are prone to forming continuous fluorinated phases and disrupting the continuity of ion transport channels.

[0018] As a preferred embodiment of the present invention, the long-chain fluorinated alkane monomer includes a terminal glycidyl group, which is beneficial for forming a ring-opening polymerization.

[0019] As a preferred embodiment of the present invention, the long-chain fluorinated alkane monomer does not contain vinyl groups, so that it does not enter the main chain and avoids interfering with the formation of flexible ion transport channels.

[0020] Therefore, preferably, the long-chain fluorinated alkane monomer is selected from at least one of 1,4-bis(2,3-epoxypropyl)perfluorobutane, 2,2-(2,2,3,3,4,4,5,5,6,6,7,7-dodecanooctane-1,8-diyl)bis(ethylene oxide), 3-(perfluorohexyl)propane, 3-(perfluorooctyl)-1,2-epoxypropane, (2,2,3,3,4,4,5,5,5-nonafluoropentyl)ethylene oxide, 3-perfluorodecyl-1,2-epoxypropane, and (2,2,3,3,4,4,4-heptafluorobutyl)ethylene oxide.

[0021] In a preferred embodiment of the present invention, the long-chain fluorinated alkane monomer includes at least two terminal glycidyl groups. The two-terminal molecules can participate in connections in two directions, forming a uniform and complete three-dimensional network, providing a more stable and continuous free volume distribution, which is beneficial for ion transport.

[0022] Or / and, as a preferred embodiment of the present invention, the long-chain fluoroalkane monomer includes a perfluoroalkane chain with 3 to 6 carbon atoms, more preferably a perfluoroalkane chain with 3 to 4 carbon atoms. The perfluoroalkane chain should not be too long, as excessive length may reduce wettability with the electrode and block ion transport channels.

[0023] Therefore, more preferably, the long-chain fluorinated alkane monomer is 1,4-bis(2,3-epoxypropyl)perfluorobutane.

[0024] Furthermore, the amount of long-chain fluorinated alkane monomers used in polymerization also affects the performance of the electrolyte and battery. For example, excessive use may cause macroscopic phase separation and damage to homogeneity, while insufficient use may cause GPEs to soften and become easily deformed and broken during cycling. Preferably, the long-chain fluorinated alkane monomers account for 1 wt% to 5 wt% of the mass of the prepolymer solution. Examples include 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, and 5 wt%.

[0025] Secondly, in this invention By using epoxy olefin copolymers, vinyl siloxane monomers and fluorinated alkane monomers are better crosslinked to construct GPEs with a three-dimensional crosslinked network structure, which have excellent electrochemical performance, outstanding mechanical strength, good interfacial compatibility and excellent safety.

[0026] The epoxy olefin copolymer does not need to be overly complex, and only includes epoxy groups and vinyl groups. Preferably, the epoxy olefin copolymer is selected from at least one of epoxide butene, isoprene monoxide, and 3,4-epoxy-2-methyl-1-butene.

[0027] In a preferred embodiment of the present invention, the epoxy olefin copolymer comprises a disubstituted olefinic carbon atom linked to an epoxy group. This carbon atom is connected to another carbon atom via a double bond on one side and to an epoxy group via a bond on the other side. It is simultaneously activated by the double bond and the strained ring, readily undergoing a ring-opening reaction. Furthermore, it exhibits low steric hindrance, which facilitates the formation of a more uniform network, reduces the impact of uneven crosslinking point distribution on ion transport, and provides a more continuous, low-resistance transport path for lithium ions.

[0028] Therefore, more preferably, the epoxy olefin copolymer is selected from epoxy butene.

[0029] Furthermore, the epoxy olefin copolymer participates in the free radical polymerization with vinylsiloxane monomers through olefin bonds, becoming part of the ionically conductive backbone; and through epoxy groups, it participates in the ring-opening polymerization with long-chain fluorinated siloxane monomers, becoming chemical bonding points connecting the backbone and the fluorinated crosslinked network. The amount of epoxy olefin copolymer determines the epoxy group density on the backbone and the number of connection points between the fluorinated crosslinked network and the flexible backbone. Too little copolymer may lead to insufficient crosslinking points, while too much may lead to over-crosslinking and a rigid crosslinked network. Preferably, the epoxy olefin copolymer accounts for 0.01wt% to 1wt% of the mass of the prepolymer liquid. For example, it may be 0.01wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, or 1wt%.

[0030] Finally, in this invention The copolymerization of the three components is initiated by an initiator and heating.

[0031] Thermal initiation allows the electrolyte to be uniformly bound within the three-dimensional mesh-like framework of GPEs, improving electrochemical performance and effectively avoiding the risk of electrolyte leakage, thus enhancing battery safety.

[0032] As a preferred embodiment of the present invention, thermal initiation is performed at 45~80°C for 2~5 hours. For example, the temperature can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C; and the time can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours.

[0033] As a preferred embodiment of the present invention, the initiator includes a free radical initiator.

[0034] Preferably, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, aluminum trifluoromethanesulfonate, benzoyl peroxide, di-tert-butyl peroxide, ammonium persulfate, and tert-butyl hydroperoxide.

[0035] More preferably, the initiator is azobisisobutyronitrile (AIBN).

[0036] Preferably, the initiator accounts for 0.01 wt% to 0.8 wt% of the mass of the prepolymer liquid. For example, it may be 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, or 0.8 wt%.

[0037] As a preferred embodiment of the present invention, the monomer is composed of vinylsiloxane monomers, long-chain fluorinated alkane monomers, and epoxy olefin copolymers, thereby avoiding the adverse effects of other substances.

[0038] Furthermore, the choice of electrolyte in the prepolymer solution is not limited; a conventional electrolyte containing lithium salt can be used.

[0039] As a preferred embodiment of the present invention, the electrolyte comprises a non-aqueous organic solvent, a lithium salt, and additives.

[0040] Preferably, the electrolyte is composed of a non-aqueous organic solvent, a lithium salt, and additives.

[0041] As a preferred embodiment of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium dioxolane borate (LiBOB), lithium difluorooxolane borate (LiDFOB), lithium difluorophosphate (LiPO2F2), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0042] Preferably, the concentration of the lithium salt in the electrolyte is 0.8~1.5M. For example, it can be 0.8M, 0.9M, 1.0M, 1.1M, 1.2M, 1.3M, 1.4M, or 1.5M.

[0043] As a preferred embodiment of the present invention, the additive is selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propenesulfonyl lactone (PST), 1,3-propanesulfonyl lactone (PS), methylene disulfonate (MMDS), vinyl sulfate (DTD), tris(trimethylsilyl)phosphate (TMSP), and tris(trimethylsilyl)borate (TMSB).

[0044] Preferably, the additive accounts for 0.1 to 10 wt% of the electrolyte mass. For example, it can be 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%.

[0045] Preferably, the non-aqueous organic solvent is selected from at least one of carbonates or carboxylic esters. More preferably, the non-aqueous organic solvent is selected from at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), propyl propionate (PP), ethyl propionate (EP), ethyl acetate (EA), ethyl butyrate (EB), and fluoroethylene carbonate (FEC).

[0046] Secondly, another objective of the present invention is to provide a battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is selected from the aforementioned gel electrolyte, and the negative electrode is a silicon-based negative electrode or a lithium metal negative electrode.

[0047] As a preferred embodiment of the present invention, the silicon-based anode comprises a pure silicon anode. Preferably, the pure silicon anode is a nano-silicon anode.

[0048] As a preferred embodiment of the present invention, the diaphragm is a poly(vinylidene fluoride-hexafluoropropylene) copolymer diaphragm.

[0049] As a preferred embodiment of the present invention, the positive electrode is lithium nickel cobalt manganese oxide.

[0050] The beneficial effects of this invention are:

[0051] 1. The present invention provides a gel electrolyte, which is formed by thermal initiation of a prepolymer liquid comprising vinylsiloxane monomers, long-chain fluorinated alkane monomers, epoxy olefin copolymers, and an initiator.

[0052] These GPEs exhibit excellent compatibility with silicon-based or lithium metal anodes, providing strong support for the design of high-performance, high-safety solid-state / gel polymer electrolytes.

[0053] These GPEs exhibit excellent electrochemical performance, safety, and resistance to high-voltage oxidation, and maintain tight contact with the electrode. Furthermore, the GPEs demonstrate good cycling performance at both room temperature and high temperature, high ionic conductivity, and Li... + The fast migration rate of GPEs is beneficial to the cycle and rate performance of the battery; moreover, GPEs can also regulate the composition of the electrode electrolyte interphase (EEI). The inorganic and organic components rich in LiF / Si-O introduced into the EEI make the EEI dense, thin and stable, effectively suppressing the occurrence of interfacial side reactions during subsequent cycles.

[0054] 2. This invention provides a silicon-based anode or lithium metal anode battery, which exhibits excellent cycling performance at room temperature and high temperature under high voltage, and high ionic conductivity. Detailed Implementation

[0055] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described, but the present invention is not limited to these embodiments.

[0056] Example 1

[0057] A gel electrolyte suitable for silicon-based or lithium metal anodes, wherein the gel electrolyte is formed by thermal initiation of a prepolymer solution at 60°C for 3 hours.

[0058] The prepolymer solution comprises 3 wt% of 1,7-divinyl-octamethyltetrasiloxane, 2 wt% of 1,4-di(2,3-epoxypropyl)perfluorobutane, 0.5 wt% of butylene oxide, and 0.1 wt% of azobisisobutyronitrile (AIBN), with the remainder being the electrolyte.

[0059] The electrolyte comprises 12.5 wt% LiPF6, 0.5 wt% LiFSI, 0.8 wt% LiPO2F2, 1 wt% LiDFOB, 10 wt% FEC, 1 wt% DTD, 0.5 wt% TMSP, and 0.5 wt% PS, with the remainder being a mixture of EC, PC, and EMC in a mass ratio of 5:15:80. The FEC, with its stronger oxidation resistance, partially replaces the solvent portion of the EC to suit the high-voltage testing environment of subsequent lithium metal anode-high nickel ternary cathode batteries and to prevent excessive oxidation and decomposition of the electrolyte.

[0060] A battery LMB includes a lithium nickel cobalt manganese oxide positive electrode, a lithium metal negative electrode, a poly(vinylidene fluoride-hexafluoropropylene) copolymer separator, and the aforementioned gel electrolyte.

[0061] The gel electrolyte and battery are prepared through the following steps:

[0062] S1. Electrolyte preparation: In an argon-filled glove box (moisture < 0.1 ppm, oxygen < 0.1 ppm), EC, PC, and EMC are mixed evenly in a mass ratio of 5:15:80. Then, 12.5 wt% LiPF6, 0.5 wt% LiFSI, 0.8 wt% LiPO2F2, 1 wt% LiDFOB, 10 wt% FEC, 1 wt% DTD, 0.5 wt% TMSP, and 0.5 wt% PS (by mass of the electrolyte) are added. The mixture is stirred until completely dissolved to obtain the electrolyte.

[0063] S2. Preparation of prepolymer solution: Add 3 wt% of 1,7-divinyl-octamethyltetrasiloxane, 2 wt% of 1,4-di(2,3-epoxypropyl)perfluorobutane, 0.5 wt% of epoxybutene, and 0.1 wt% of AIBN to the electrolyte and stir until completely dissolved to obtain the prepolymer solution for later use.

[0064] S3. Preparation of the positive electrode: The positive electrode active material is lithium nickel cobalt manganese oxide (MCN811). The positive electrode active material is mixed with conventional conductive agent and conventional binder in a certain proportion to form a slurry. The slurry is evenly coated on the aluminum current collector using a coating machine. After rolling, the positive electrode sheet is obtained. The positive electrode sheet is manually cut into 14mm diameter sheets, vacuum dried at 85℃ for 6 hours, and then placed in a glove box for later use.

[0065] S4. Battery separator preparation: Weigh 1.0g of poly(vinylidene fluoride-hexafluoropropylene) copolymer (PVDF-HFP) and add it to 4.0g of NMP. Heat and stir at 60℃ until completely dissolved to obtain a white, transparent, viscous solution. Then, use a dropper to drop this liquid onto aluminum foil, spread it evenly with a blade, place it in high-purity water, and let it stand for 1 hour. After it turns into a gel state, peel it off from the aluminum foil, dry it at 50℃ for 8 hours, and cut it into separator sizes (19mm in diameter) for later use.

[0066] S5. Battery negative electrode preparation: The negative electrode uses lithium metal with a specification of Φ15.4(mm)×0.6(mm).

[0067] S6. Formation of the gel electrolyte and preparation of the battery: Using a CR2032 coin cell battery case, an NCM811 positive electrode sheet was placed inside the positive electrode case. 100 μL of prepolymer solution was added to fully wet the electrode. A separator was then placed in the case, and another 100 μL of prepolymer solution was added to the separator. Finally, the lithium metal negative electrode, gasket, spring sheet, and negative electrode case were placed in sequence. The stacked battery case was transferred to a coin cell battery packaging machine and sealed under pressure. To ensure sufficient wetting of the battery, it was left to stand at room temperature for 12 hours. Then, the battery with the added prepolymer solution was placed in a 60°C oven for 3 hours to thermally initiate in-situ polymerization of monomers, forming a gel electrolyte suitable for the battery.

[0068] Example 2

[0069] This embodiment is basically the same as Embodiment 1, except that the long-chain fluorinated alkane monomers are different, and the long-chain fluorinated alkane monomers have only one end with an epoxypropyl group.

[0070] Specifically, 1,4-bis(2,3-epoxypropyl)perfluorobutane is replaced with (2,2,3,3,4,4,4-heptafluorobutyl)ethylene oxide.

[0071] Example 3

[0072] This embodiment is basically the same as Embodiment 2, except that the long-chain fluorinated alkane monomers are different and the number of perfluorinated segments is increased.

[0073] Specifically, (2,2,3,3,4,4,4-heptafluorobutyl) ethylene oxide is replaced with 3-(perfluorohexyl) propylene oxide.

[0074] Example 4

[0075] This embodiment is basically the same as Embodiment 2, except that the long-chain fluorinated alkane monomers are different and the perfluorinated segments are further increased.

[0076] Specifically, (2,2,3,3,4,4,4-heptafluorobutyl) ethylene oxide is replaced with 3-(perfluorooctyl)-1,2-epoxypropane.

[0077] Example 5

[0078] This embodiment is basically the same as Embodiment 1, except that the epoxy olefin copolymer is different, and the epoxy olefin copolymer is connected to a trisubstituted olefin carbon with an epoxy group.

[0079] Specifically, epoxybutene is replaced with 3,4-epoxy-2-methyl-1-butene.

[0080] Example 6

[0081] This embodiment is basically the same as Embodiment 1, except that the vinylsiloxane monomers are different and the siloxane chain length is reduced.

[0082] Specifically, 1,7-divinyl-octamethyltetrasiloxane is replaced with 1,5-divinyl-hexamethyltrisiloxane.

[0083] Example 7

[0084] This embodiment is basically the same as Embodiment 1, except that the vinylsiloxane monomers are different and the topological structure of the siloxane segments is branched.

[0085] Specifically, 1,7-divinyl-octamethyltetrasiloxane is replaced with tris(vinyldimethylsiloxy)methylsilane.

[0086] Example 8

[0087] This embodiment is basically the same as Embodiment 1, except that the vinylsiloxane monomers are different and the topological structure of the siloxane segments is cyclic.

[0088] Specifically, 1,7-divinyl-octamethyltetrasiloxane is replaced with 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane.

[0089] Example 9

[0090] This embodiment is basically the same as Embodiment 1, except that the negative electrode is a nano-silicon negative electrode.

[0091] The nano-silicon anode is prepared through the following steps: using nano-silicon with a particle size <150nm as the anode active material, the anode active material is mixed with a composite conductive agent composed of SP and CNT, a conventional binder, and a thickener in a certain proportion to form a slurry. The slurry is then uniformly coated onto a copper current collector using a coating machine, and the anode sheet is obtained after rolling. The anode sheet is manually cut into 14mm diameter sheets, vacuum dried at 85℃ for 6 hours, and then placed in a glove box for later use.

[0092] Comparative Example 1

[0093] This comparative example is basically the same as Example 1, except that: the electrolyte is different, and the electrolyte prepared in step S1 of Example 1 is used as the battery electrolyte; correspondingly, the separator is different, and the separator is a Celgard2400 model separator.

[0094] Specifically: A CR2032 button cell casing is used, and an NCM811 positive electrode plate is placed inside the positive electrode casing. Add 100μL of real The electrolyte prepared in step S1 of Example 1 is used to fully wet the electrode, and a Celgard 2400 type diaphragm is placed in it. 100 μL of the electrolyte prepared in step S1 of Example 1 was added to the Celgard 2400 diaphragm. Finally, the lithium metal anode, gasket, spring sheet, and anode shell are placed in sequence. The stacked battery casing is then transferred to a button cell packaging machine and sealed under pressure. To ensure sufficient battery immersion, it needs to be left at room temperature for 12 hours. Then, the battery with prepolymer solution is placed in a 60°C oven for 3 hours.

[0095] Comparative Example 2

[0096] This comparative example is basically the same as Example 1, except that thermal initiation is not performed.

[0097] The only difference lies in step S6: A CR2032 coin cell battery case is used. An NCM811 positive electrode sheet is placed inside the positive electrode case, and 100 μL of prepolymer solution is added to fully wet the electrode. A separator is then placed inside, and another 100 μL of prepolymer solution is added to the separator. Finally, the lithium metal negative electrode, gasket, spring sheet, and negative electrode case are placed in sequence. The stacked battery case is then transferred to a coin cell battery packaging machine and sealed under pressure. To ensure sufficient battery wetting, it needs to be left at room temperature for 12 hours. Then, the battery with the added prepolymer solution is... Let it stand at 25℃ for 3 hours.

[0098] Comparative Example 3

[0099] This comparative example is basically the same as Example 1, except that the electrolyte is different and does not contain epoxy olefin copolymers.

[0100] The only difference is in step S2: 1,7-divinyl-octamethyltetrasiloxane (3 wt% of the prepolymer solution mass), 1,4-di(2,3-epoxypropyl)perfluorobutane (2 wt% of the prepolymer solution mass), and AIBN (0.1 wt% of the prepolymer solution mass) are added to the electrolyte and stirred until completely dissolved to obtain the prepolymer solution for later use.

[0101] Comparative Example 4

[0102] This comparative example is basically the same as Example 1, except that the electrolyte is different and does not contain long-chain fluorinated alkane monomers.

[0103] The only difference is in step S2: 1,7-divinyl-octamethyltetrasiloxane (3 wt% of the prepolymer solution mass), 0.5 wt% epoxybutene, and 0.1 wt% AIBN are added to the electrolyte and stirred until completely dissolved to obtain the prepolymer solution for later use.

[0104] Performance testing

[0105] Room temperature cycle performance: Under room temperature (25℃) conditions, the above battery was activated by charging and discharging at a constant current of 0.1C for three cycles, with a voltage range of 3.0~4.3V. Then, it was charged at a constant current and constant voltage of 1C to 4.3V, with a cutoff current of 0.05C; rested for 10 minutes, and then discharged at a constant current of 1C to 3.0V, and rested for 10 minutes. This is the first cycle, and the discharge capacity obtained is the first discharge capacity C0. The battery was then cycled for 500 more cycles to obtain the discharge capacity C1 of the 500th cycle. The capacity retention rate of the 500th cycle was calculated using the following formula: Capacity retention rate (%) of the 500th cycle = (C1 / C0) × 100%.

[0106] High-temperature cycle performance: Under high-temperature (45℃) conditions, the battery was charged to 4.3V at a constant current and constant voltage of 1C, with a cutoff current of 0.05C; it was then allowed to rest for 10 minutes, followed by discharge at a constant current of 1C to 3.0V, and then allowed to rest for 10 minutes. This is the first cycle, and the resulting discharge capacity is the first discharge capacity C0. The battery was then cycled 500 times to obtain the discharge capacity C1 of the 500th cycle. The capacity retention rate after the 500th cycle was calculated using the following formula: Capacity retention rate after the 500th cycle (%) = (C1 / C0) × 100%.

[0107] Lithium-ion transport number test: Lithium-lithium symmetric batteries were assembled using the electrolytes from Examples 1-9 and Comparative Examples 1-4. After assembly, the batteries were allowed to stand for 12 hours. Examples 1-9 and Comparative Examples 3-4 were placed in an oven at 60°C for 3 hours to form a gel. The initial EIS of the lithium-lithium symmetric batteries was tested using an electrochemical workstation. The bulk impedance value R0 of the electrolyte was obtained by fitting using the equivalent circuit method. Using the i~t function in the electrochemical workstation, the battery was kept at a constant potential of 10mV for 1 hour to obtain the initial current (I0) and steady-state current (I0) curves. s After the i~t test is completed, the battery is then subjected to an EIS test, and the battery impedance R is obtained by fitting using the equivalent circuit method. s Substituting the values ​​obtained above into the formula below, we can obtain the lithium-ion mobility: .

[0108] The test results are shown in Table 1 below.

[0109] Table 1. .

[0110] As shown in Table 1, Examples 1-8 and Comparative Examples 1-4 are lithium metal anode batteries, and Example 9 is a nano-silicon anode battery.

[0111] As shown in Example 9, it is known that the cycle performance of nano-silicon anodes is generally poor, typically only around 100 cycles. During these 100 cycles, the battery capacity rapidly decreases until the battery performance completely fails. However, the nano-silicon anode of this invention, after being improved by the gel electrolyte, can withstand up to 500 cycles at both room temperature and high temperature without completely failing. This demonstrates the applicability and improvement of the gel electrolyte of this invention for silicon-based anodes, especially pure silicon anodes.

[0112] As can be seen from Examples 1-8 and Comparative Examples 1-4, and compared with Example 1 and Comparative Example 1, the gel electrolyte of the present invention can effectively improve the room temperature and high temperature cycling performance of LMBs under high voltage, as well as the lithium ion transference number, compared with conventional electrolytes.

[0113] As can be seen from the comparison between Example 1 and Comparative Example 2, whether the gel electrolyte is thermally initiated to form a gel electrolyte is particularly crucial for improving the electrical performance of LMBs. Adding monomers, copolymers and initiators to the electrolyte without thermally initiating them to gel may only affect the electrical performance of LMBs as additives.

[0114] As can be seen from the comparison of Example 1 and Comparative Examples 3 and 4, the addition of epoxy olefin copolymers enables vinyl siloxane monomers and fluorinated alkane monomers to crosslink better, which promotes the overall electrical properties of the gel electrolyte; fluorinated alkane monomers significantly help improve the electrical properties of the gel electrolyte and have a significant effect on increasing the lithium ion transference number.

[0115] Furthermore, as can be seen from the comparison within the examples, selecting appropriate vinylsiloxane monomers, long-chain fluorinated alkane monomers, and epoxy olefin copolymers can further improve battery performance.

[0116] Comparing Examples 1 and 2, it is evident that the two-terminal epoxypropyl groups, compared to the single-terminal epoxypropyl groups, can form a more uniform and complete three-dimensional network, thus improving electrical performance. Comparing Examples 2, 3, and 4, it is evident that the length of the perfluorinated segments should be appropriate; excessive length may actually lead to a decrease in electrical performance. Comparing Examples 1 and 5, it is evident that the high activity and low steric hindrance of the disubstituted olefin carbons linked to the epoxy groups in epoxy olefin copolymers contribute to the formation of a more uniform network, providing a more continuous and low-resistance transport path. Comparing Examples 1 and 6, it is evident that an appropriate siloxane segment length in vinylsiloxane monomers is beneficial to improving ionic conductivity. Comparing Examples 1 and 7 and 8, it is evident that the preferred topology of the siloxane segments in vinylsiloxane monomers is a straight chain, with relatively mild vinyl activity, which helps to subsequently form a uniform and defect-free crosslinked network; and the flexible Si-O-Si segments in the middle help improve the elasticity and toughness of the crosslinked network, avoiding rigidity from affecting ion mobility.

[0117] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A gel electrolyte suitable for silicon-based or lithium metal anodes, characterized in that: The gel electrolyte is formed by thermal initiation of a prepolymer solution at 45~80°C; The prepolymer solution includes an electrolyte, monomers, and an initiator. The monomers include vinylsiloxane monomers, long-chain fluorinated alkane monomers, and epoxy olefin copolymers. The long-chain fluorinated alkane monomers have at least 6 carbon atoms and include epoxy groups.

2. The gel electrolyte according to claim 1, suitable for silicon-based or lithium metal anodes, characterized in that: The monomer is composed of vinylsiloxane monomers, long-chain fluorinated alkane monomers, and epoxy olefin copolymers.

3. A gel electrolyte suitable for silicon-based or lithium metal anodes according to claim 1 or 2, characterized in that: The topological structure of the siloxane segments in the vinylsiloxane monomers is linear.

4. A gel electrolyte suitable for silicon-based or lithium metal anodes according to claim 1 or 2, characterized in that: The long-chain fluorinated alkane monomers include at least two terminal glycidyl groups.

5. A gel electrolyte suitable for silicon-based or lithium metal anodes according to claim 1 or 2, characterized in that: The long-chain fluorinated alkane monomers include perfluoroalkane chains with 3 to 6 carbon atoms.

6. A gel electrolyte suitable for silicon-based or lithium metal anodes according to claim 1 or 2, characterized in that: The epoxy olefin copolymer includes disubstituted olefin carbons linked to epoxy groups.

7. A gel electrolyte suitable for silicon-based or lithium metal anodes according to claim 1 or 2, characterized in that: The initiator includes a free radical initiator.

8. A gel electrolyte suitable for silicon-based or lithium metal anodes according to claim 1 or 2, characterized in that: The vinylsiloxane monomers account for 2wt% to 6wt% of the mass of the prepolymer liquid; And / or, the long-chain fluorinated alkane monomer accounts for 1wt% to 5wt% of the mass of the prepolymer liquid; And / or, the epoxy olefin copolymer accounts for 0.01 wt% to 1 wt% of the mass of the prepolymer liquid; And / or, the initiator accounts for 0.01wt% to 0.8wt% of the mass of the prepolymer liquid.

9. A battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that: The electrolyte is selected from the gel electrolyte described in any one of claims 1 to 8. The negative electrode is a silicon-based negative electrode or a lithium metal negative electrode, and the silicon-based negative electrode includes a pure silicon negative electrode.

10. A battery according to claim 9, characterized in that: The diaphragm is a poly(vinylidene fluoride-hexafluoropropylene) copolymer diaphragm.