An in-situ solidified semi-solid gel electrolyte and lithium ion battery and a preparation method thereof

Abstract

This invention belongs to the field of lithium-ion battery technology, specifically disclosing an in-situ cured semi-solid gel electrolyte and a lithium-ion battery, as well as its preparation method. It solves the technical problems of existing single-component semi-solid electrolytes where mechanical stability and interfacial stability cannot be simultaneously achieved, and the short cycle life of silicon-based lithium-ion batteries. The electrolyte is prepared by in-situ copolymerization and curing of a fluorinated aromatic olefin monomer, a multifunctional (meth)acrylate monomer, an initiator, and an electrolyte. The fluorinated aromatic olefin monomer enhances the electrolyte's oxidation resistance and mechanical strength, while the multifunctional (meth)acrylate monomer optimizes interfacial stability. The copolymerization of these two monomers constructs a rigid-flexible three-dimensional polymer network, which can suppress the volume expansion of the silicon anode and maintain the integrity of the electrode structure. This invention also discloses the preparation method of the electrolyte and a lithium-ion battery containing this electrolyte. The electrolyte of this invention exhibits excellent ionic conductivity and interfacial stability, and the preparation process is simple.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to an in-situ solidified semi-solid gel electrolyte and a lithium-ion battery and their preparation method. Background Technology

[0002] The widespread adoption of portable consumer electronics and long-range electric vehicles has spurred the pursuit of higher safety and cycle performance in lithium-ion batteries. Silicon (Si)-based materials, with their extremely high theoretical specific capacity (approximately 4200 mAh / g), have emerged as the most promising next-generation anode material. However, silicon undergoes drastic volume changes (>300%) during charge and discharge. Although silicon anodes can be oxidized or combined with carbon materials, a series of bottlenecks remain in practical applications: Irreversible damage to the solid electrolyte interface (SEI): The massive volume expansion and contraction during charge-discharge cycles cause the SEI on the silicon surface to repeatedly break and regenerate. This process irreversibly consumes the active lithium and electrolyte within the battery, leading to rapid capacity decay.

[0003] Electrode structure failure: The continuous stress during the negative electrode cycling process can cause silicon particles to break and decompose, and detach from the current collector, leading to electrode structure and electrical contact failure.

[0004] The inherent safety risks of liquid electrolytes: Traditional organic carbonate electrolytes are prone to leakage and explosion, while the unstable interface of silicon-based anodes further exacerbates the risks and hidden dangers of liquid electrolytes.

[0005] To address these issues, researchers have focused on solid / semi-solid electrolyte systems, such as oxide, sulfide, and polymer electrolytes. Oxide solid electrolytes suffer from poor interfacial contact, leading to brittle films; sulfide solid electrolytes are prone to reaction with air and failure, and are also costly. In contrast, polymer electrolytes offer advantages in terms of low cost and device flexibility, but their room-temperature ionic conductivity limits their further application. For example, Chinese patent CN117996175A introduces high-voltage resistant propylene carbonate groups and fluorinated groups into lithium metal batteries, but this may present incompatibility issues with silicon-based anodes. Patent CN115275334B uses pentaerythritol tetra(3-mercaptopropionate) and divinyl adipate copolymerization, initiating polymerization with visible light, but uneven curing may occur in thick electrodes. Our previous work, patent 202511132601.2, uses a copolymerization method of polyfluorinated acrylates and PEGDA, demonstrating its application prospects in high-nickel silicon-based systems, but its cycle life still has room for improvement.

[0006] In addition, single-component in-situ cured semi-solid electrolytes are commonly used, such as acrylate monomers or cyclic ether monomers. Because there is only one monomer, the chemical structure and physical properties (such as modulus and toughness) of its polymer network are fixed and cannot be adjusted. If its modulus (toughness) is too low, it cannot restrain the huge volume expansion of the silicon anode during charging and discharging, leading to electrode structure damage and continuous rupture of the electrolyte interface (SEI). If its modulus is too high, it cannot take advantage of the in-situ polymerization process, resulting in interface separation and increased impedance. Therefore, single-component semi-solid electrolytes often cannot simultaneously achieve mechanical stability and interfacial stability, resulting in a rapid decline in cycle life. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an in-situ solidified semi-solid gel electrolyte and a lithium-ion battery and a method for preparing the same, so as to solve the problem that in the prior art, single-component semi-solid electrolytes often cannot simultaneously achieve mechanical stability and interfacial stability, resulting in rapid decay of cycle life.

[0008] To achieve the above objectives, the present invention employs the following technical solution: An in-situ cured semi-solid gel electrolyte is obtained by curing raw materials, the raw materials including fluorinated aromatic olefin monomers, multifunctional (meth)acrylate monomers, initiators and electrolytes.

[0009] A further improvement of the present invention is that: Preferably, the fluorinated aromatic olefin monomer is one or more of 3-(trifluoromethyl)styrene, 2,3,4,5,6-pentafluorostyrene, 1,3-bis(trifluoromethyl)-5-vinylbenzene, 4-(2,2,2-trifluoroethoxy)styrene, 1-allyl-3,5-bis(trifluoromethyl)benzene, 6-(trifluoromethyl)-2-vinylnaphthalene, and 2,7-bis(trifluoromethyl)-4-vinylbiphenyl.

[0010] Preferably, the multifunctional (meth)acrylate monomer is one or more selected from trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate, bis(trimethylolpropane)tetraacrylate and 2-acrylamidoethyl acrylate.

[0011] Preferably, the initiator is one or more selected from benzoyl peroxide, azobisisobutyronitrile, potassium persulfate, di-tert-butyl peroxide, cumene hydroperoxide, boron trifluoride-diethyl ether complex, di(2,4-dichlorobenzoyl peroxide), di-tert-pentyl peroxide, and dicumene peroxide.

[0012] The mass ratio of the fluorinated aromatic olefin monomer, (meth)acrylate monomer, initiator and electrolyte is (0.01~20):(0.01~20):(0.0001~2):(20~95).

[0013] Preferably, the electrolyte comprises a lithium salt, an organic solvent, and an additive; the lithium salt is one or more selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalate borate; the organic solvent is one or more selected from ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propyl propionate, and fluoroethylene carbonate; and the additive is vinylene carbonate.

[0014] A lithium-ion battery includes a positive electrode, a negative electrode, and an in-situ solidified semi-solid gel electrolyte as described in any one of claims 1-6.

[0015] Preferably, the positive electrode is a high-nickel ternary material or a lithium-rich material, and the negative electrode is a silicon-carbon composite material or a silicon-oxygen composite material.

[0016] A method for preparing a lithium-ion battery includes the following steps: S1, fluorinated aromatic olefin monomer, multifunctional (meth)acrylate monomer, initiator and electrolyte are mixed and stirred to obtain electrolyte precursor; S2, the electrolyte precursor is injected into the cell, which contains a positive electrode and a negative electrode. After standing, it is hot-pressed and then polymerized and solidified in situ to obtain a lithium-ion battery.

[0017] Preferably, the hot pressing temperature in S2 is 40-70℃, the hot pressing pressure is 0.1-2MPa, and the hot pressing time is 6-48h.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses an in-situ cured electrolyte, in which fluorinated aromatic olefin monomers and multifunctional (meth)acrylate monomers are introduced. In the fluorinated aromatic olefin monomers, the fluorine atoms introduced onto the benzene ring have a strong electron-withdrawing inductive effect and high CF bond energy, effectively reducing the electron cloud density of the polymer chain, thereby broadening the electrochemical window and endowing the material with excellent high-pressure oxidation stability. Simultaneously, the rigid aromatic ring structure enhances the main chain backbone stiffness of the molecular chain, while the low polarity of the fluorine atoms helps promote close stacking between polymer chains and forms a hydrophobic microphase separation structure, synergistically improving the mechanical toughness and structural density of the copolymer, resulting in higher tensile strength and modulus, forming the final rigid polymer. In this fluorinated aromatic olefin monomer, the fluorine atoms bonded to the main chain aromatic ring stabilize the chain segment electron cloud density through a conjugated system, providing intrinsic oxidation resistance. Furthermore, the fixed fluorine element is less prone to migration and loss, resulting in a final structure with electrolyte oxidation resistance and mechanical strength. The stability of fluorine also contributes to the formation of an optimized interface in the battery. The active hydrogen in the polyfunctional (meth)acrylate monomer contributes to interface stability, and the fluorinated aromatic olefin monomer and the polyfunctional (meth)acrylate monomer form a crosslinked network through double bond copolymerization under free radical initiation. The rigid aromatic ring of the fluorinated aromatic olefin and the electron-withdrawing fluorine atoms enhance the oxidation resistance and segment rigidity of the polymer main chain, while the polyfunctional (meth)acrylate provides high-density crosslinking sites. The two copolymerize in situ to construct a rigid-flexible three-dimensional network structure. This structure not only restricts chain segment movement and improves mechanical strength through chemical bonding but also optimizes interface stability with the low surface energy of the fluorine component, thereby achieving long battery cycle life. A rigid framework allows the electrolyte network to exert mechanical binding forces, suppressing the expansion of silicon anode particles during lithium intercalation; flexible segments enable the electrolyte network to exhibit resilience during the shrinkage of the silicon anode after lithium deintercalation, ensuring a tight fit. These mechanisms maximize the integrity of the silicon anode electrode structure during cycling, synergistically resolving the conflict between mechanical strength and interfacial flexibility. This reduces damage to the solid electrolyte interphase (SEI) film caused by drastic deformation, resulting in ultra-long cycle life for silicon-based lithium-ion batteries. Through molecular design and ratio optimization of the two monomers, the final electrolyte exhibits good ionic conductivity and lithium-ion transference number, along with excellent interfacial stability.

[0019] This invention also discloses a method for preparing a lithium-ion battery. The electrolyte precursor solution is directly placed within the battery cell, where a polymerization reaction occurs inside the battery. A liquid solvent / plasticizer is used to increase the amorphous regions in the polymer matrix and enhance ion transport capabilities. Compared to traditional film-forming and assembly processes, the electrolyte is directly generated on the surface and within the pores of the electrodes, particularly the silicon anode, forming an integrated interface that conforms to the electrode morphology and is entangled in all three dimensions. This method achieves a controllable transformation from a liquid precursor to a semi-solid electrolyte, forming a fully integrated interface where the electrode and electrolyte are completely bonded, thereby significantly improving the cycle life of silicon-based high-energy-density lithium-ion batteries. Attached Figure Description

[0020] Figure 1 The semi-solid electrolyte and in-situ solidification preparation process provided by this invention; Figure 2 The infrared spectrum of Example 1; Figure 3 This is a comparison of the microstructure of the battery electrode in Example 1 of the present invention and Comparative Example 2 (liquid electrolyte); Among them, (a) is a microstructure diagram of the positive electrode of Example 1; (b) is a microstructure diagram of the positive electrode of the liquid battery of Comparative Example 2; (c) is a microstructure diagram of the negative electrode of Example 1; and (d) is a microstructure diagram of the negative electrode of the liquid battery of Comparative Example 2. Figure 4 This is a comparison of the cycling performance of Example 1 and Comparative Example 2 (liquid electrolyte) at 1C. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings: To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0024] The following examples use conventional instruments and equipment in the art. Unless otherwise specified, the raw materials used in this invention are all commercially available conventional products, and the instruments used are all conventional instruments in the field of lithium-ion battery preparation; the experimental process is carried out in a high-purity argon atmosphere with a moisture and oxygen content of less than 0.1 ppm to avoid the influence of moisture and oxygen on the electrolyte and battery performance; "%" in the text means weight percentage, "parts" means parts by weight, and all ratios are by weight.

[0025] The core of this invention lies in constructing a rigid-flexible three-dimensional polymer network through in-situ copolymerization of fluorinated aromatic olefin monomers and multifunctional (meth)acrylate monomers. This network, combined with electrolyte and initiator, forms an in-situ solidified semi-solid gel electrolyte, solving the problem of the inability to simultaneously achieve mechanical and interfacial stability in a single-component semi-solid electrolyte. Furthermore, the in-situ hot-press polymerization method within the battery cell allows for perfect bonding between the electrolyte and the silicon-based anode, significantly improving the cycle life of silicon-based lithium-ion batteries.

[0026] The first aspect of this invention discloses an in-situ cured semi-solid gel electrolyte, which is obtained by curing raw materials, including fluorinated aromatic olefin monomers, multifunctional (meth)acrylate monomers, an initiator, and an electrolyte. In this invention, fluorinated aromatic olefin monomers and multifunctional (meth)acrylate monomers are copolymerized in situ in an electrolyte under the action of an initiator to form a hybrid crosslinked network with both a rigid framework and flexible segments. The fluorinated aromatic rings provide electronic structural stability and mechanical modulus support, while the multifunctional acrylates provide high-density crosslinking points and interfacial anchoring ability. The two synergistically regulate the degree of microphase separation and free volume distribution of the polymer network, thereby suppressing the lithium insertion expansion (>300%) of the silicon anode while maintaining interfacial adhesion in the delithiation contraction state. This solves the technical problem that existing single-component semi-solid electrolytes cannot simultaneously achieve mechanical stability and interfacial stability, and that silicon-based lithium-ion batteries have short cycle life.

[0027] In a preferred embodiment, the fluorinated aromatic olefin monomer is any one or more of 3-(trifluoromethyl)styrene, 2,3,4,5,6-pentafluorostyrene, 1,3-di(trifluoromethyl)-5-vinylbenzene, 4-(2,2,2-trifluoroethoxy)styrene, 1-allyl-3,5-bis(trifluoromethyl)benzene, 6-(trifluoromethyl)-2-vinylnaphthalene, and 2,7-di(trifluoromethyl)-4-vinylbiphenyl. In this invention, by introducing aromatic olefin monomers containing multiple fluorine atoms or strongly electron-withdrawing trifluoromethyl substitutions, the high bond energy and strong electronegativity of the C–F bond significantly reduce the electron cloud density of the polymer backbone, broadening the electrochemical stability window. Simultaneously, the rigid aromatic ring structure enhances the backbone stiffness, and the low polarity of the fluorine atoms promotes tight interchain stacking and induces hydrophobic microphase separation, synergistically improving the tensile strength and density of the polymer network.

[0028] In a preferred embodiment, the multifunctional (meth)acrylate monomer is one or more selected from trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate, bis(trimethylolpropane)tetraacrylate, and 2-acrylamidoethyl acrylate. The polyethylene glycol diacrylate selected in this invention possesses flexible ether segments that enhance lithium salt dissociation ability and react with Li. + The amide groups enhance interfacial adhesion by interacting with hydroxyl groups on the silicon oxide surface through hydrogen bonding, while the branched structure strengthens the physical anchoring of silicon particles. This design improves the dynamic adaptability of the electrolyte to the volume deformation of the silicon anode during cycling.

[0029] In a preferred embodiment, the initiator is one or more of benzoyl peroxide, azobisisobutyronitrile, potassium persulfate, di-tert-butyl peroxide, cumene hydroperoxide, boron trifluoride-ethyl ether complex, di(2,4-dichlorobenzoyl peroxide), di-tert-pentyl peroxide, and dicumene peroxide.

[0030] In a preferred embodiment, the mass ratio of the fluorinated aromatic olefin monomer, (meth)acrylate monomer, initiator, and electrolyte is (0.01~20):(0.01~20):(0.0001~2):(20~95). For example, this ratio can be 0.01:0.01:0.0001:20, 10:10:0.01:50, or 20:20:2:90. By limiting the mass ratio range of the four components, the balance between the polymer network crosslinking density and the electrolyte retention rate is controlled: when the total mass percentage of the fluorinated aromatic olefin monomer and acrylate monomer is less than 5 wt%, the network modulus is insufficient, and it cannot effectively constrain the expansion of silicon particles; when the total percentage is greater than 40 wt%, the free volume is significantly reduced, and the ionic conductivity decreases.

[0031] In a preferred embodiment, the electrolyte comprises a lithium salt, an organic solvent, and an additive. For example, the concentration of the lithium salt in the organic solvent is 1 mol / L, and the additive is vinylene carbonate (VC) at an exemplary concentration of 1 wt.%. The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalate borate. The organic solvent is one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DE), propyl propionate (PP), and fluoroethylene carbonate (FEC).

[0032] The second aspect of the present invention discloses a lithium-ion battery, comprising a positive electrode, a negative electrode and the above-described in-situ solidified semi-solid gel electrolyte.

[0033] The positive electrode is a high-nickel ternary material or a lithium-rich material, and the negative electrode is a silicon-carbon composite material or a silicon-oxygen composite material.

[0034] When existing polymers are used as electrolyte gels, using a single but structurally complex multifunctional monomer can form a network with certain mechanical properties, but its molecular design is difficult, costly, and performance control is inflexible. If polymer blending or physical crosslinking is used, a certain polymer system can also be formed through physical interactions such as van der Waals forces and crystalline regions, but the strength of physical bonds is lower than that of chemical bonds, resulting in low mechanical strength of the polymer system, which cannot meet the stability requirements under long-term electrochemical coupling. If ring-opening self-polymerization initiated by lithium salts is used, a certain semi-solid system can also be formed, but its aging process is difficult to control, it is prone to premature initiation, and the polymerization process is difficult to control, resulting in unstable final performance. If thermal polymerization is not performed under other conditions, the initiator can also play a role in monomer polymerization, but its polymerization process can only be controlled by temperature and time, which cannot guarantee the stability of interfacial contact and cell structure, resulting in large variance of final performance parameters.

[0035] See Figure 1 To address the aforementioned problems, a third aspect of the present invention discloses a method for preparing a lithium-ion battery, comprising the following steps: S1, fluorinated aromatic olefin monomer, multifunctional (meth)acrylate monomer, initiator and electrolyte are mixed and stirred to obtain electrolyte precursor; S2, the electrolyte precursor is injected into the cell, which contains a positive electrode and a negative electrode. After standing, it is hot-pressed and then polymerized and solidified in situ to obtain a lithium-ion battery.

[0036] In a preferred embodiment, the stirring time in S1 is preferably 0.1-10h; more preferably 0.2-3h; and even more preferably 0.3-1h, such as 25min, 45min, 100min, etc.

[0037] After stirring, it is preferable to inject the liquid immediately without letting it stand to avoid polymerization of the monomers. In step S2, after the electrolyte precursor solution is injected into the battery cell, it is immersed for a period of 2 hours to 72 hours, such as 5 hours, 10 hours, 24 hours, 48 ​​hours, etc.

[0038] In S2, hot pressing refers to uniform heating under pressure, with a hot pressing temperature of 40-70℃, a hot pressing pressure of 0.1-2MPa, and a hot pressing time of 6-48h. For example, polymerization is carried out at 70℃ and 2MPa for 40h. Preferably, in S2, the above-mentioned precursor solution is injected into a clean battery cell, and controlled stepwise hot pressing polymerization is carried out in a hot pressing machine.

[0039] In S2, the in-situ solidified cell includes an in-situ solidified electrolyte, a positive electrode, a negative electrode, a separator, and other essential battery components.

[0040] It should be understood that the above-mentioned initiation method is thermal initiation, and other initiation methods can achieve the same effect.

[0041] The following description, in conjunction with specific embodiments, provides further details.

[0042] Example 1 1g of polyethylene glycol diacrylate, 1g of 2,3,4,5,6-pentafluorostyrene, 0.1g of azobisisobutyronitrile, and 10g of electrolyte (EC / FEC=5:1 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at 25°C for 48 hours to ensure complete electrolyte impregnation. Afterward, it was placed in a hot-pressing machine with a clamping layer and polymerized in situ at 45°C and 1MPa for 48 hours to obtain a battery cell that had completed in-situ curing. The polymeric structural formulas of polyethylene glycol diacrylate and pentafluorostyrene in this battery cell are as follows: [ CH2 CH(C6F5) ] m [ CH2 CH(COO (CH2CH2O) n COO CH=CH2) ] p Where m,p is 10 to 10 4 n is 4 to 20.

[0043] The infrared spectrum of the polymer is as follows: Figure 2As shown, the first group (LE) is a pure electrolyte system (including EC, FEC, LiPF6, and VC). The graph shows only the characteristic absorption peaks of the functional groups contained in the electrolyte itself, with no additional unsaturated bond-related characteristic signals. The second group (precursor solution) is a mixed system in which functional monomers are added to the electrolyte but no polymerization reaction is initiated. In addition to the inherent absorption peaks of the electrolyte, the characteristic absorption peaks corresponding to the carbon-carbon double bonds (C=C) in the monomer molecules can be clearly detected in the spectrum, proving that the monomers are uniformly dispersed in the electrolyte system in a free state, without cross-linking or polymerization reactions, and the molecular structure remains intact. The third group (Polymerized precursor solution) is a semi-solid / gel electrolyte system prepared by polymerization. The characteristic absorption peaks corresponding to the carbon-carbon double bonds of the monomers completely disappear in the spectrum, with no residual double bond characteristic signals. This indicates that the unsaturated monomers contained in the system underwent sufficient free radical polymerization under polymerization conditions, and the carbon-carbon double bonds fully participated in cross-linking polymerization, forming a stable polymer network structure. The double bond functional groups were completely consumed by the polymerization reaction, so the corresponding characteristic absorption peaks could not be detected in the infrared spectrum.

[0044] Example 2 2g of trimethylolpropane triacrylate, 2g of 3-(trifluoromethyl)styrene, 0.1g of azobisisobutyronitrile, and 15g of electrolyte (EC / FEC=5:1 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into NCM811 / SiC lithium-ion soft-pack cells. The mixture was kept at 35°C for 24 hours to allow the electrolyte to fully impregnate the cells. After this process, the cells were placed in the spacer of a hot press machine and polymerized in situ at 60°C under a pressure of 2 MPa for 48 hours to obtain cells that have been cured in situ.

[0045] Example 3 4g of trimethylolpropane triacrylate, 1g of 1,3-bis(trifluoromethyl)-5-vinylbenzene, 0.1g of azobisisobutyronitrile, and 20g of electrolyte (EC / FEC=5:1 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into NCM811 / SiC lithium-ion soft-pack cells. The mixture was kept at 35°C for 24 hours to allow the electrolyte to fully impregnate the cells. After this process, the cells were placed in the spacer of a hot press machine and polymerized in situ at 70°C under a pressure of 0.5 MPa for 24 hours to obtain cells that have been cured in situ.

[0046] Example 4 0.5g of polyethylene glycol diacrylate, 2g of 2,3,4,5,6-pentafluorostyrene, 0.1g of azobisisobutyronitrile, and 10g of electrolyte (EC / FEC=5:1 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at 25°C for 24 hours to allow the electrolyte to fully impregnate it. After this process, the mixture was placed in the spacer of a hot press machine and polymerized in situ at 70°C under a pressure of 0.5 MPa for 10 hours to obtain a battery cell that had been completely cured in situ.

[0047] Example 5 0.5g pentaerythritol triacrylate, 1g 3-(trifluoromethyl)styrene, 0.1g azobisisobutyronitrile, and 20g electrolyte (EC / FEC=5:1 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into NCM811 / SiC lithium-ion soft-pack cells. The mixture was kept at 35°C for 48 hours to allow the electrolyte to fully impregnate the cells. After this process, the cells were placed in the spacer of a hot press machine and polymerized in situ at 60°C under a pressure of 1 MPa for 10 hours to obtain cells that have been cured in situ.

[0048] Example 6 0.5g of bis(trimethylolpropane)tetraacrylate, 1.5g of 1,3-bis(trifluoromethyl)-5-vinylbenzene, 0.05g of benzoyl peroxide, and 12g of electrolyte (EC / DMC=1:1, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack cell. The mixture was kept at 25°C for 24 hours to allow the electrolyte to fully impregnate it. After this process, the cell was placed in the spacer of a hot press and polymerized in situ at 40°C under a pressure of 0.1MPa for 6 hours to obtain a cell that had been completely cured in situ.

[0049] Example 7 1g of 2-acrylamidoethyl acrylate, 1g of 2,3,4,5,6-pentafluorostyrene, 0.08g of azobisisobutyronitrile, and 15g of electrolyte (EC / EMC=3:7, 1M LiFSI, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at a constant temperature of 30℃ for 36h to ensure complete electrolyte impregnation. After this process, the mixture was placed in the clamping layer of a hot press machine and polymerized in situ at a pressure of 0.5MPa at 50℃ for 24h to obtain a battery cell that had been completely cured in situ.

[0050] Example 8 1.2g of trimethylolpropane triacrylate, 0.8g of 6-(trifluoromethyl)-2-vinylnaphthalene, 0.06g of dicumyl peroxide, and 14g of electrolyte (EC / PP=4:6, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at a constant temperature of 25°C for 48h. After the electrolyte was fully impregnated, the mixture was placed in the clamping layer of a hot press machine and polymerized in situ at a pressure of 1.2MPa at 55°C for 30h to obtain a battery cell that had been completely cured in situ.

[0051] Example 9 1.5g of polyethylene glycol diacrylate, 1.5g of 2,7-bis(trifluoromethyl)-4-vinylbiphenyl, 0.1g of azobisisobutyronitrile, and 18g of electrolyte (EC / DEC=1:1, 1M LiDFOB, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at 25°C for 48 hours to allow the electrolyte to fully impregnate it. After this process, the mixture was placed in the spacer of a hot press machine and polymerized in situ at 65°C under a pressure of 1.5MPa for 12 hours to obtain a battery cell that had been completely cured in situ.

[0052] Example 10 1g of pentaerythritol triacrylate, 1g of 4-(2,2,2-trifluoroethoxy)styrene, 0.05g of azobisisobutyronitrile, and 12g of electrolyte (EC / DEC = 5:1, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion pouch cell. The mixture was then in-situ polymerized at 65°C and 1.5MPa for 12h to obtain a cell that had been completely cured in situ.

[0053] Example 11 1g of trimethylolpropane triacrylate, 1g of 1-allyl-3,5-bis(trifluoromethyl)benzene, 0.04g of di-tert-butyl peroxide, and 15g of electrolyte (EC / DEC / DMC=3:3:4, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at a constant temperature of 25°C for 24 hours to allow the electrolyte to fully impregnate it. After this process, the mixture was placed in the spacer of a hot press machine and polymerized in situ at 70°C and a pressure of 0.8MPa for 16 hours to obtain a battery cell that had been completely cured in situ.

[0054] Example 12 0.01g of 2,3,4,5,6-pentafluorostyrene, 0.01g of polyethylene glycol diacrylate, 0.0001g of azobisisobutyronitrile, and 20g of electrolyte (EC / FEC=5:1, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into a lithium-ion soft-pack cell of NCM811 / SiC. The mixture was kept at a constant temperature of 25°C for 48h. After the electrolyte was fully impregnated, the mixture was placed in the clamping layer of a hot press machine and polymerized in situ at a pressure of 1MPa at 70°C for 48h to obtain a cell that had been cured in situ.

[0055] Example 13 20g of 2,3,4,5,6-pentafluorostyrene, 20g of polyethylene glycol diacrylate, 2g of azobisisobutyronitrile, and 20g of electrolyte (EC / FEC=5:1, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into a lithium-ion soft-pack cell of NCM811 / SiC. The mixture was kept at a constant temperature of 25°C for 48h. After the electrolyte was fully impregnated, the mixture was placed in the clamping layer of a hot press machine and polymerized in situ at 70°C and a pressure of 1MPa for 48h to obtain a cell that had been cured in situ.

[0056] Example 14 20g of 2,3,4,5,6-pentafluorostyrene, 20g of polyethylene glycol diacrylate, 2g of azobisisobutyronitrile, and 95g of electrolyte (EC / FEC=5:1, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into NCM811 / SiC lithium-ion soft-pack cells. The mixture was kept at 25°C for 48 hours to allow the electrolyte to fully impregnate the cells. After this process, the cells were placed in the spacer of a hot press machine and polymerized in situ at 70°C and 1MPa for 48 hours to obtain cells that had been cured in situ.

[0057] Example 15 20g of 2,3,4,5,6-pentafluorostyrene, 0.01g of polyethylene glycol diacrylate, 1g of azobisisobutyronitrile, and 50g of electrolyte (EC / FEC=5:1, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at a constant temperature of 25°C for 48h. After the electrolyte was fully impregnated, the mixture was placed in the clamping layer of a hot press machine and polymerized in situ at 70°C and a pressure of 1MPa for 48h to obtain a battery cell that had been completely cured in situ.

[0058] Example 16 0.01g of 2,3,4,5,6-pentafluorostyrene, 20g of polyethylene glycol diacrylate, 1g of azobisisobutyronitrile, and 50g of electrolyte (EC / FEC=5:1, 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at a constant temperature of 25°C for 48h. After the electrolyte was fully impregnated, the mixture was placed in the clamping layer of a hot press machine and polymerized in situ at 70°C and a pressure of 1MPa for 48h to obtain a battery cell that had been completely cured in situ.

[0059] Comparative Example 1 1g of polyethylene glycol diacrylate, 1g of butyl acrylate, 0.1g of azobisisobutyronitrile, and 10g of electrolyte (EC / FEC=5:1 1M LiPF6, 1wt.% VC) were uniformly mixed and injected into an NCM811 / SiC lithium-ion soft-pack battery cell. The mixture was kept at a constant temperature of 25°C for 48 hours to ensure complete electrolyte impregnation. After this process, the mixture was placed in the spacer of a hot press machine and polymerized in situ at a pressure of 1 MPa at 45°C for 48 hours to obtain a battery cell that had been completely cured in situ.

[0060] Comparative Example 2 10g of electrolyte (EC / FEC=5:1 1M LiPF6, 1wt.% VC) was uniformly mixed and injected into NCM811 / SiC lithium-ion soft-pack cells. The cells were kept at a constant temperature of 25℃ for 48h. After the electrolyte was fully impregnated, the cells were placed in an oven and polymerized in situ at 45℃ and 1MPa pressure for 48h using a fixture in the oven to obtain cells that have been completely cured in situ.

[0061] Table 1 Electrical performance parameter tests for Examples 1-5

[0062] See Figure 3 To compare the microstructure of the battery electrodes in Example 1 and Comparative Example 2 (liquid electrolyte) of the present invention, by Figure 3 It is known that after treatment with hot-pressing in-situ polymerization, a dense coating layer can be uniformly formed on the surface of the positive and negative electrode particles. This in-situ formed semi-solid gel coating layer can stabilize the electrode. Electrolyte interface, suppression of side reactions and increase in interfacial impedance, mitigation of electrode material volume deformation, and maintenance of electrode structure and ion transport channel integrity significantly reduce capacity decay and improve battery cycle stability. Figure 4 As shown in the cycle performance curves, the experimental group of the present invention has achieved a significant improvement in cycle life performance compared with the liquid battery comparative example 2. The battery can still maintain 85% of its capacity retention rate after 500 cycles. At the same time, compared with the comparative example 1 without the addition of fluorinated aromatic olefin monomers, the battery of the experimental group of the present invention has a slower capacity decay rate and better cycle stability.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An in-situ solidified semi-solid gel electrolyte, characterized in that, The in-situ cured semi-solid gel electrolyte is obtained by curing raw materials, which include fluorinated aromatic olefin monomers, multifunctional (meth)acrylate monomers, initiators, and electrolytes.

2. The in-situ solidified semi-solid gel electrolyte according to claim 1, characterized in that, The fluorinated aromatic olefin monomer is one or more of 3-(trifluoromethyl)styrene, 2,3,4,5,6-pentafluorostyrene, 1,3-bis(trifluoromethyl)-5-vinylbenzene, 4-(2,2,2-trifluoroethoxy)styrene, 1-allyl-3,5-bis(trifluoromethyl)benzene, 6-(trifluoromethyl)-2-vinylnaphthalene, and 2,7-bis(trifluoromethyl)-4-vinylbiphenyl.

3. The in-situ solidified semi-solid gel electrolyte according to claim 1, characterized in that, The multifunctional (meth)acrylate monomer is one or more of trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate, bis(trimethylolpropane)tetraacrylate, and 2-acrylamidoethyl acrylate.

4. The in-situ solidified semi-solid gel electrolyte according to claim 1, characterized in that, The initiator is one or more of the following: benzoyl peroxide, azobisisobutyronitrile, potassium persulfate, di-tert-butyl peroxide, cumene hydroperoxide, boron trifluoride-diethyl ether complex, di(2,4-dichlorobenzoyl peroxide), di-tert-pentyl peroxide, and dicumene peroxide.

5. The in-situ solidified semi-solid gel electrolyte according to claim 1, characterized in that, The mass ratio of the fluorinated aromatic olefin monomer, (meth)acrylate monomer, initiator and electrolyte is (0.01~20):(0.01~20):(0.0001~2):(20~95).

6. The in-situ solidified semi-solid gel electrolyte according to claim 1, characterized in that, The electrolyte comprises a lithium salt, an organic solvent, and an additive; the lithium salt is one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalate borate; the organic solvent is one or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propyl propionate, and fluoroethylene carbonate; and the additive is vinylene carbonate.

7. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and an in-situ cured semi-solid gel electrolyte as described in any one of claims 1-6.

8. A lithium-ion battery according to claim 7, characterized in that, The positive electrode is a high-nickel ternary material or a lithium-rich material, and the negative electrode is a silicon-carbon composite material or a silicon-oxygen composite material.

9. A method for preparing a lithium-ion battery, characterized in that, Includes the following steps: S1, fluorinated aromatic olefin monomer, multifunctional (meth)acrylate monomer, initiator and electrolyte are mixed and stirred to obtain electrolyte precursor; S2, the electrolyte precursor is injected into the cell, which contains a positive electrode and a negative electrode. After standing, it is hot-pressed and then polymerized and solidified in situ to obtain a lithium-ion battery.

10. A method for preparing a lithium-ion battery according to claim 9, characterized in that, In S2, the hot-pressing temperature is 40-70℃, the hot-pressing pressure is 0.1-2MPa, and the hot-pressing time is 6-48h.

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