Local high-concentration in-situ polymerization gel electrolyte and application thereof in lithium metal battery
By introducing fluorine or polyfluoroalkyl functional groups into epoxy ether-based fluorinated derivatives at the C-position of epoxy ethers, locally high-concentration gel electrolytes are constructed, solving the problems of narrow voltage window and poor cycle stability of lithium-ion batteries, and improving the electrochemical performance and safety of lithium metal batteries.
Patent Information
- Application Number
- CN202610198166.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-11
- Publication Date
- 2026-05-12
AI Technical Summary
Existing lithium-ion batteries have narrow voltage windows and poor cycle stability due to the use of polyether-based electrolytes. Furthermore, monomer residues from the in-situ polymerization process are prone to oxidation and decomposition, which affects battery performance.
Electron-withdrawing fluorine or polyfluoroalkyl functional groups are introduced at the C-site of epoxy ether to construct epoxy ether-based fluorinated derivatives as diluents, forming locally high-concentration gel electrolytes. Through in-situ polymerization, a stable interfacial protective layer is formed on the electrode surface, enhancing antioxidant properties and cycle stability.
It achieves a wide voltage window, good cycle stability, suppresses electrolyte oxidation and decomposition, and improves the electrochemical performance and safety of lithium metal batteries.
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Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of lithium batteries, and particularly relates to a gel electrolyte. Background Technology
[0002] In recent years, the development of electric vehicles has placed higher demands on key performance indicators of lithium-ion batteries, such as energy density, safety, and lifespan. Solid-state lithium batteries, which use solid electrolytes instead of traditional liquid electrolytes, offer advantages such as high safety and compatibility with high-capacity positive and negative electrodes, and are considered the most competitive solution to overcome the performance bottlenecks of traditional liquid lithium-ion batteries. In-situ polymerization is one of the easiest strategies for the commercial application of solid-state lithium metal batteries. Its polymerization process is simple, and the polymerization reaction occurring inside the battery allows for close contact between the electrodes and the electrolyte, thereby reducing interfacial impedance and enabling lithium metal batteries to exhibit excellent electrochemical performance. The most common polymerization monomers are epoxy ethers, represented by 1,3-dioxolane (DOL). Epoxy ether solvents typically have low viscosity, which is beneficial for the in-situ polymerization precursor electrolyte to wet the separator and electrodes, and they also exhibit significant stability compared to lithium metal, leading to extensive research in recent years. However, the terminal hydroxyl groups and ether oxygen chains of polyether-based electrolytes exhibit intrinsic instability at high potentials, poor oxidation resistance, narrow voltage windows, and are prone to side reactions, thus affecting cycle performance. Meanwhile, unpolymerized monomers remain during in-situ polymerization and are easily oxidized and decomposed under high pressure, further deteriorating the cycle performance.
[0003] To overcome the above problems, the interfacial stability, voltage window, and cycle stability can be improved by optimizing the composition of the in-situ polymerized electrolyte. Chinese patent application CN118553996A utilizes dopamine to modify glass fibers, and then synthesizes a silane coupling agent-modified PDOL-based polymer gel electrolyte on the modified glass fibers through in-situ polymerization. This significantly improves a series of problems existing in the PDOL system, such as low ionic conductivity, low lithium-ion transference number, and poor electrochemical stability. However, modifying the glass fibers increases the manufacturing process and production cost. Chinese patent application CN119742439A uses a deep eutectic solution as a plasticizer to obtain a high-voltage resistant in-situ polymerized solid electrolyte with excellent properties such as a wide electrochemical window, high ionic conductivity, high mechanical strength, good flame retardancy, and wide temperature applicability, making it suitable for high-voltage systems above 4.6V. However, one of the main components of the deep eutectic solution used is a nitrile solvent, which has excessively high viscosity, affecting electrode wettability, and is also highly toxic.
[0004] Therefore, it is necessary to design an in-situ polymerized gel electrolyte that can form a stable solid electrolyte interphase (SEI) film on the electrode surface, has low monomer residue, a wide voltage window, good cycle performance, good wettability of the polymerization precursor, and a simple process. Summary of the Invention
[0005] To address the technical problems of narrow voltage windows and poor cycle stability in polyether-based electrolytes, this invention proposes a locally highly concentrated in-situ polymerized gel electrolyte and its application in lithium metal batteries. By introducing electron-withdrawing fluorine, polyfluorinated, or perfluoroalkyl functional groups at the C-site of the epoxy ether, an epoxy ether-based fluorinated derivative is constructed. These electron-withdrawing fluorine, polyfluorinated, or perfluoroalkyl functional groups can hinder ring-opening polymerization and reduce solvation capacity. Introduced as a diluent into the in-situ polymerized gel electrolyte, these groups can maintain the tight coordination structure of solvent molecules and anions with lithium ions in a localized environment, forming a locally highly concentrated gel electrolyte. The solvation structure in this gel electrolyte is predominantly anionic, with contact ion pairs (CIPs) and aggregated ion pairs (AGGs) dominating. This allows for the formation of a more stable inorganic-rich interfacial protective layer on the electrode surface, enhancing oxidation resistance, inhibiting electrolyte oxidative decomposition, and improving high-voltage performance. In particular, when the polymerizing monomer is an epoxy ether, it can induce uniform polymerization of the monomer. Benefiting from these advantages, this gel electrolyte exhibits a wide voltage window and good cycle stability. At the same time, the addition of this type of diluent results in a low viscosity of the diluent itself, which reduces the viscosity of the polymerization precursor and improves wettability.
[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:
[0007] A locally high-concentration in-situ polymerized gel electrolyte is obtained through an in-situ polymerization reaction of a precursor solution. The precursor solution comprises the following components: cyclic ether polymerizable monomers, epoxy ether-based fluorinated derivative diluents, plasticizers, additives, initiators, and lithium salts. The epoxy ether-based fluorinated derivative diluents are fluorinated derivatives in which the carbon atoms of the epoxy ether are substituents of hydrogen, fluorine, polyfluoroalkyl, or perfluoroalkyl groups, with at least one substituent being a perfluoroalkyl group. After polymerization, the in-situ polymerized gel electrolyte forms locally high-concentration lithium salt regions, where the lithium salt concentration is higher than the overall average lithium salt concentration.
[0008] The epoxy ether-based fluorinated derivative diluent is one or more of 4-(trifluoromethyl)-1,3-dioxolane, 2,2-bis(trifluoromethyl)-1,3-dioxolane, 4,4,5,5-tetrafluoro-2,2-bis(trifluoromethyl)-1,3-dioxacyclopentane, and 2-trifluoromethyl-2-(2,2,2-trifluoroethyl)-1,3-dioxolane.
[0009] The concentrations of each component in the precursor solution are as follows (based on the total mass of the precursor solution, and the lithium salt based on the solution volume): 30wt%-70wt% of cyclic ether polymer monomers, 9wt%-50wt% of epoxy ether-based fluorinated derivative diluent, 2wt%-30wt% of plasticizer, 0.5wt%-10wt% of additives, 0.5wt%-20wt% of initiator, and 10wt%-40wt% of lithium salt.
[0010] The mass ratio of the cyclic ether polymer monomer to the epoxy ether fluorinated derivative diluent is 1-5:1.
[0011] The cyclic ether polymer monomers are any one or two or more of 1,3-dioxolane, 1,3,5-trioxane, 1,3-dioxane, 1,4-dioxane, propylene oxide, tetrahydrofuran, methyltetrahydrofuran, and tetrahydropyran.
[0012] The plasticizer is any one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, and propyl acetate.
[0013] The additive is any one or more of the following: fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, propylene sulfonate lactone, lithium difluorophosphate, 1,3-propane sulfonate lactone, tris(trimethylsilane) phosphate, 4-propyl-[1,3]-dioxolane-2-one, lithium tetrafluoroborate, lithium oxalate borate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and lithium nitrate.
[0014] The initiator is any one or two or more of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium difluorosulfonyl imide, azobisisobutyronitrile, stannous octoate, tin trifluoromethanesulfonate, and aluminum trifluoromethanesulfonate.
[0015] Preferably, the initiator is lithium hexafluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, or lithium difluorosulfonyl imide.
[0016] The lithium salt is any one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(oxalate-borate), lithium difluorodioxalate phosphate, lithium difluorophosphate, and lithium hexafluoroarsenate.
[0017] The application of a locally highly concentrated in-situ polymerized gel electrolyte in lithium metal batteries is characterized by comprising the following steps:
[0018] (1) Under the protection of an inert gas, the cyclic ether polymer monomer and the lithium salt are mixed evenly to obtain a mixed solution A;
[0019] (2) Mix the epoxy ether-based fluorinated derivative diluent, additives, plasticizers and initiators evenly to obtain mixed solution B;
[0020] (3) Add mixed solution A to mixed solution B and stir until homogeneous to obtain precursor solution;
[0021] (4) Inject the precursor solution into the unfilled battery, assemble the battery, place the battery and allow it to undergo in-situ polymerization to obtain a lithium metal battery containing the gel electrolyte.
[0022] The temperature for placement in step (4) is 25℃-60℃, and the placement time is 6h-168h; the in-situ polymerization reaction proceeds spontaneously under these placement conditions.
[0023] The beneficial effects of this invention are:
[0024] (1) This invention constructs an epoxy ether-based fluorinated derivative by introducing electron-withdrawing fluorine, polyfluoroalkyl, or perfluoroalkyl functional groups at the C-site of the epoxy ether, and introduces it as a diluent into the in-situ polymerized gel electrolyte system. In the epoxy ether-based fluorinated derivative, the electron-withdrawing fluorine, polyfluoroalkyl, or perfluoroalkyl functional groups can effectively hinder the disordered ring-opening polymerization of the monomers, especially when the monomers are epoxy ethers, they can specifically induce the uniform polymerization of the monomers, ensuring the uniformity of the gel electrolyte structure; on the other hand, they can significantly reduce the solvation ability of the diluent, prompting the gel electrolyte to maintain a close coordination structure of solvent molecules, anions, and lithium ions in the local environment, successfully constructing a locally high-concentration gel electrolyte. This locally high-concentration structure makes the solvation structure in the gel electrolyte mainly anionic, with contact ion pairs (CIPs) and aggregated ion pairs (AGGs) dominating, thereby forming a more stable inorganic-rich interface protective layer on the electrode surface, effectively enhancing the antioxidant performance of the electrolyte, inhibiting the oxidative decomposition of the electrolyte, and achieving a wide voltage window and good cycle stability of the gel electrolyte.
[0025] (2) The in-situ polymerized gel electrolyte precursor solution of the present invention is synergistically composed of cyclic ether polymerizing monomers, the above-mentioned epoxy ether-based fluorinated derivative diluent, plasticizer, additives, initiator, and lithium salt. The addition of the epoxy ether-based fluorinated derivative diluent can effectively reduce the viscosity of the polymerizing precursor, significantly improve its wettability to the electrode, and ensure that the precursor solution can uniformly cover the electrode surface. At the same time, the entire preparation process does not require complex equipment. It only requires mixing the components step by step to obtain the precursor solution, and then injecting it into the battery to complete the in-situ polymerization. The process is simple and convenient to operate, which greatly reduces the difficulty of large-scale production and enhances the industrial application potential of the gel electrolyte.
[0026] (3) When the locally high-concentration in-situ polymerized gel electrolyte of the present invention is applied to lithium metal batteries, it has advantages such as a wide voltage window, good cycle stability, stable electrode interface protective layer and excellent wettability, which effectively solves the problems of interface instability, insufficient high-voltage resistance, short battery cycle life and poor safety that are easily encountered when existing gel electrolytes are applied to lithium metal batteries. By preparing the precursor under inert gas protection and injecting it into the battery for in-situ polymerization, the gel electrolyte can be fully combined with the lithium metal battery electrode, further suppressing the occurrence of side reactions inside the battery, extending the battery life, improving battery safety, and giving full play to the performance advantages of lithium metal batteries. Detailed Implementation
[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0028] Example 1
[0029] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0030] (1) Preparation of polymerization precursor solution: Lithium bis(trifluoromethanesulfonyl)imide was added to the liquid monomer 1,3-dioxolane and stirred until homogeneous to obtain mixed solution A; lithium hexafluorophosphate was added to a mixture of diluent 4-(trifluoromethyl)-1,3-dioxolane, additive fluoroethylene carbonate, plasticizer ethylene carbonate, and diethyl carbonate and stirred until homogeneous to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred until homogeneous to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution were 34wt%, 20wt%, 8wt%, 8wt%, 8wt%, 4wt%, and 18wt%, respectively.
[0031] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0032] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 45°C for 24 hours to allow the precursor solution to gradually polymerize.
[0033] Example 2
[0034] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0035] (1) Preparation of polymerization precursor solution: Lithium bis(trifluoromethanesulfonyl)imide was added to the liquid monomer 1,3-dioxolane and stirred until homogeneous to obtain mixed solution A; lithium hexafluorophosphate was added to a mixture of diluent 4-(trifluoromethyl)-1,3-dioxolane, additive fluoroethylene carbonate, plasticizer ethylene carbonate, and diethyl carbonate and stirred until homogeneous to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred until homogeneous to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution were 34wt%, 34wt%, 8wt%, 1wt%, 1wt%, 4wt%, and 18wt%, respectively.
[0036] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0037] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 45°C for 24 hours to allow the precursor solution to gradually polymerize.
[0038] Example 3
[0039] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0040] (1) Preparation of polymerization precursor solution: Lithium bis(trifluoromethanesulfonyl)imide was added to the liquid monomer 1,3-dioxolane and stirred until homogeneous to obtain mixed solution A; lithium hexafluorophosphate was added to a mixture of diluent 4-(trifluoromethyl)-1,3-dioxolane, additive fluoroethylene carbonate, plasticizer ethylene carbonate, and diethyl carbonate and stirred until homogeneous to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred until homogeneous to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution were 45wt%, 9wt%, 8wt%, 8wt%, 8wt%, 4wt%, and 18wt%, respectively.
[0041] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0042] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 45°C for 24 hours to allow the precursor solution to gradually polymerize.
[0043] Example 4
[0044] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0045] (1) Preparation of polymerization precursor solution: Lithium bis(trifluoromethyl)-1,3-dioxolane was added to the liquid monomer 1,3-dioxolane and stirred until homogeneous to obtain mixed solution A; lithium hexafluorophosphate was added to a mixture of diluent 2,2-bis(trifluoromethyl)-1,3-dioxolane, additive fluoroethylene carbonate, plasticizer ethylene carbonate, and diethyl carbonate and stirred until homogeneous to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred until homogeneous to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution are 34wt%, 20wt%, 8wt%, 8wt%, 8wt%, 4wt%, and 18wt%, respectively.
[0046] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0047] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 45°C for 24 hours to allow the precursor solution to gradually polymerize.
[0048] Example 5
[0049] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0050] (1) Preparation of polymerization precursor liquid: Lithium bis(trifluoromethanesulfonyl)imide was added to the polymer monomer 1,3-dioxolane liquid and stirred evenly to obtain mixed solution A; lithium hexafluorophosphate was added to a mixture of diluent 4,4,5,5-tetrafluoro-2,2-bis(trifluoromethyl)-1,3-dioxane, additive fluoroethylene carbonate, plasticizer ethylene carbonate and diethyl carbonate and stirred evenly to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred evenly to obtain polymerization precursor liquid. The components in the precursor fluid, namely 1,3-dioxolane, 4,4,5,5-tetrafluoro-2,2-bis(trifluoromethyl)-1,3-dioxacyclopentane, fluoroethylene carbonate, ethylene carbonate, diethyl carbonate, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide, were present in the following mass proportions: 34 wt%, 20 wt%, 8 wt%, 8 wt%, 8 wt%, 4 wt%, and 18 wt%, respectively.
[0051] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0052] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 45°C for 24 hours to allow the precursor solution to gradually polymerize.
[0053] Example 6
[0054] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0055] (1) Preparation of polymerization precursor liquid: Lithium bis(trifluoromethanesulfonyl)imide was added to the polymer monomer 1,3-dioxane liquid and stirred evenly to obtain mixed solution A; lithium hexafluorophosphate was added to a mixture of diluent 4,4,5,5-tetrafluoro-2,2-bis(trifluoromethyl)-1,3-dioxane, additive fluoroethylene carbonate, plasticizer ethylene carbonate and diethyl carbonate and stirred evenly to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred evenly to obtain polymerization precursor liquid. The components in the precursor fluid, namely 1,3-dioxane, 4,4,5,5-tetrafluoro-2,2-bis(trifluoromethyl)-1,3-dioxane, fluoroethylene carbonate, ethylene carbonate, diethyl carbonate, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide, were present in the following mass proportions: 34 wt%, 20 wt%, 8 wt%, 8 wt%, 8 wt%, 4 wt%, and 18 wt%, respectively.
[0056] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0057] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 45°C for 24 hours to allow the precursor solution to gradually polymerize.
[0058] Example 7
[0059] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0060] (1) Preparation of polymerization precursor solution: Lithium perchlorate was added to the 1,4-dioxane ring liquid of the polymerization monomer and stirred evenly to obtain mixed solution A; 4-(trifluoromethyl)-1,3-dioxolane, vinyl sulfate, azobisisobutyronitrile, propyl propionate and ethylene carbonate were mixed and stirred evenly to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred evenly to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution were 30wt%, 20wt%, 0.5wt%, 0.5wt%, 15wt%, 15wt% and 19wt%, respectively.
[0061] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0062] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 25°C for 168 hours to allow the precursor solution to gradually polymerize.
[0063] Example 8
[0064] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0065] (1) Preparation of polymerization precursor solution: Lithium difluorophosphate was added to the liquid monomer 1,3,5-trioxane and stirred until homogeneous to obtain mixed solution A; lithium difluorooxalate borate initiator was added to a mixture of diluent 4-(trifluoromethyl)-1,3-dioxolane, additive lithium tetrafluoroborate, and plasticizer dimethyl carbonate and stirred until homogeneous to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred until homogeneous to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution were 70wt%, 15wt%, 1.5wt%, 3wt%, 0.5wt%, and 10wt%, respectively.
[0066] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0067] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 60°C for 6 hours to allow the precursor solution to gradually polymerize.
[0068] Example 9
[0069] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0070] (1) Preparation of polymerization precursor solution: Lithium hexafluoroarsenate (LiHFA) was added to liquid propylene oxide monomer and stirred until homogeneous to obtain mixed solution A; lithium difluorosulfonylimide (DISI) was added to a mixture of diluent 4-(trifluoromethyl)-1,3-dioxolane, additive triphenyl phosphate, and plasticizer ethyl acetate and stirred until homogeneous to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred until homogeneous to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution as follows: propylene oxide, 4-(trifluoromethyl)-1,3-dioxolane, triphenyl phosphate, ethyl acetate, lithium difluorosulfonylimide, and lithium hexafluoroarsenate were 40 wt%, 10 wt%, 10 wt%, 10 wt%, 20 wt%, and 10 wt%, respectively.
[0071] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0072] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 60°C for 6 hours to allow the precursor solution to gradually polymerize.
[0073] Comparative Example 1
[0074] An in-situ polymerized gel electrolyte without diluent is prepared by the following method:
[0075] (1) Preparation of polymerization precursor solution: Lithium bis(trifluoromethanesulfonyl)imide was added to the liquid monomer 1,3-dioxolane and stirred until homogeneous to obtain mixed solution A; lithium hexafluorophosphate was added to a mixture of additives fluoroethylene carbonate, plasticizers ethylene carbonate and diethyl carbonate and stirred until homogeneous to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred until homogeneous to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution were 34wt%, 8wt%, 18wt%, 18wt%, 4wt%, and 18wt%, respectively.
[0076] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0077] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 45°C for 24 hours to allow the precursor solution to gradually polymerize.
[0078] An in-situ polymerized gel electrolyte without diluent.
[0079] Without adding diluent, the components in the precursor fluid were as follows: 1,3-dioxolane, fluoroethylene carbonate, ethylene carbonate, diethyl carbonate, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide in the following mass ratios: 34 wt%, 8 wt%, 18 wt%, 18 wt%, 4 wt%, and 18 wt%, respectively. Other steps were the same as in Example 1.
[0080] Comparative Example 2
[0081] A locally highly concentrated in-situ polymerized gel electrolyte, the preparation method of which is as follows:
[0082] (1) Preparation of polymerization precursor solution: Lithium bis(trifluoromethanesulfonyl)imide was added to the liquid monomer 1,3-dioxolane and stirred until homogeneous to obtain mixed solution A; lithium hexafluorophosphate was added to a mixture of diluent 4-(trifluoromethyl)-1,3-dioxolane, additive fluoroethylene carbonate, plasticizer ethylene carbonate, and diethyl carbonate and stirred until homogeneous to obtain mixed solution B; mixed solution A was added to mixed solution B and stirred until homogeneous to obtain polymerization precursor solution. The mass ratios of the components in the precursor solution were 24wt%, 34wt%, 8wt%, 6wt%, 6wt%, 4wt%, and 18wt%, respectively.
[0083] (2) Preparation of positive electrode: The active material of positive electrode is high nickel ternary NCM811, the conductive agent is carbon black, and the binder is polyvinylidene fluoride. The mass ratio of NCM811: carbon black: polyvinylidene fluoride is 8:1:1. The mixture is dry-ground and mixed evenly. Then, a certain amount of solvent NMP is added to the mixture, and the mixture is stirred and coated evenly on 12μm aluminum foil. The mixture is then transferred to an oven to dry to obtain the positive electrode.
[0084] (3) Use the prepared precursor solution to assemble lithium metal batteries. The battery assembly process is as follows: Assemble the CR2025 button battery in the following order: negative electrode shell, negative electrode lithium foil, electrolyte (prepared precursor solution), separator, electrolyte (prepared precursor solution), positive electrode (prepared positive electrode), gasket, spring sheet and positive electrode shell. After assembly, place it at 45°C for 24 hours to allow the precursor solution to gradually polymerize.
[0085] Cyclic performance testing: The lithium metal batteries prepared in the examples and comparative examples were subjected to charge-discharge tests between 2.75-4.2V (1C current density of 200mA g). -1 The cyclic performance is shown in Table 1.
[0086] Electrochemical window testing: The prepared lithium-stainless steel coin cells were subjected to linear scan voltammetry testing with a voltage range of 3V-6V and a scan rate of 1mV / s. The electrochemical window is shown in Table 1.
[0087] Table 1 Electrochemical Performance Table
[0088]
[0089] Compared with Comparative Example 1, Examples 1, 2, and 3 demonstrate that the addition of diluent helps improve cycle performance and electrochemical window. Compared with Comparative Example 2, Examples 1, 2, and 3 demonstrate that the monomer and diluent must meet a certain ratio for the addition of diluent to have an improving effect.
[0090] 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. A locally highly concentrated in-situ polymerized gel electrolyte, characterized in that, The in-situ polymerized gel electrolyte is obtained through an in-situ polymerization reaction of a precursor solution. The precursor solution comprises the following raw materials: cyclic ether polymer monomers, epoxy ether-based fluorinated derivative diluents, plasticizers, additives, initiators, and lithium salts. The epoxy ether-based fluorinated derivative diluents refer to fluorinated derivatives in which the carbon atoms of the epoxy ether are substituents of hydrogen, fluorine, polyfluoroalkyl, or perfluoroalkyl, and at least one substituent is a perfluoroalkyl group.
2. The locally highly concentrated in-situ polymerized gel electrolyte according to claim 1, characterized in that, The concentrations of each component in the precursor solution are as follows: 30wt%-70wt% of cyclic ether polymer monomers, 9wt%-50wt% of epoxy ether fluorinated derivative diluent, 2wt%-30wt% of plasticizer, 0.5wt%-10wt% of additives, 0.5wt%-20wt% of initiator, and 10wt%-40wt% of lithium salt.
3. The locally highly concentrated in-situ polymerized gel electrolyte according to claim 2, characterized in that, The mass ratio of the cyclic ether polymer monomer to the epoxy ether fluorinated derivative diluent is 1-5:
1.
4. The locally highly concentrated in-situ polymerized gel electrolyte according to claim 3, characterized in that, The cyclic ether polymer monomer is any one or more of 1,3-dioxolane, 1,3,5-trioxane, 1,3-dioxane, 1,4-dioxane, propylene oxide, tetrahydrofuran, methyltetrahydrofuran, and tetrahydropyran; the epoxy ether-based fluorinated derivative diluent is any one or more of 4-(trifluoromethyl)-1,3-dioxolane, 2,2-bis(trifluoromethyl)-1,3-dioxolane, 4,4,5,5-tetrafluoro-2,2-bis(trifluoromethyl)-1,3-dioxane, and 2-trifluoromethyl-2-(2,2,2-trifluoroethyl)-1,3-dioxolane.
5. The locally highly concentrated in-situ polymerized gel electrolyte according to claim 1, characterized in that, The plasticizer is any one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, and propyl acetate.
6. The locally highly concentrated in-situ polymerized gel electrolyte according to claim 1, characterized in that, The additive is any one or more of the following: fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, propylene sulfonate lactone, lithium difluorophosphate, 1,3-propane sulfonate lactone, tris(trimethylsilane) phosphate, 4-propyl-[1,3]-dioxolane-2-one, lithium tetrafluoroborate, lithium oxalate borate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and lithium nitrate.
7. The locally highly concentrated in-situ polymerized gel electrolyte according to claim 1, characterized in that, The initiator is any one or two or more of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium difluorosulfonylimide, aluminum trifluoromethanesulfonate, tin trifluoromethanesulfonate, stannous octoate, and azobisisobutyronitrile.
8. The locally highly concentrated in-situ polymerized gel electrolyte according to claim 1, characterized in that, The lithium salt is any one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(oxalate-borate), lithium difluorodioxalate phosphate, lithium difluorophosphate, and lithium hexafluoroarsenate.
9. The application of the locally highly concentrated in-situ polymerized gel electrolyte according to any one of claims 1-8 in lithium metal batteries, characterized in that, Includes the following steps: (1) Under the protection of an inert gas, the cyclic ether polymer monomer and the lithium salt are mixed evenly to obtain a mixed solution A; (2) Mix the epoxy ether-based fluorinated derivative diluent, additives, plasticizers and initiators evenly to obtain mixed solution B; (3) Add mixed solution A to mixed solution B to obtain the precursor solution; (4) Inject the precursor solution into the unfilled battery, then assemble the battery, place the battery and allow it to undergo a polymerization reaction to obtain a lithium metal battery containing the gel electrolyte.
10. The application of the locally highly concentrated in-situ polymerized gel electrolyte according to claim 9 in lithium metal batteries, characterized in that, The temperature in step (4) is 25℃-60℃ and the time is 6h-168h.