Novel fluorinated aromatic multifunctional lithium battery gel electrolyte, and preparation method and application thereof

Abstract

The application provides a novel fluorinated aromatic multifunctional lithium battery gel electrolyte, a preparation method and application thereof. The electrolyte comprises a basic electrolyte, a fluorinated aromatic additive, a polymerizable monomer containing a trifluoromethyl group, a crosslinking agent and an initiator; the basic electrolyte comprises lithium hexafluorophosphate and an organic solvent; the fluorinated aromatic additive is an aromatic compound containing a tetrafluoroethoxy group; the polymerizable monomer containing a trifluoromethyl group and the crosslinking agent undergo a free radical polymerization reaction in the presence of the initiator to form a three-dimensional crosslinked polymer network. The gel electrolyte has the advantages of synergistically regulating lithium ion solvation structure and electrode interface chemistry, inhibiting hydrogen fluoride-induced electrode corrosion, giving consideration to good ionic conductivity and a wide electrochemical stability window, and improving the cycle stability of a high-voltage lithium metal battery.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a novel fluorinated aromatic multifunctional lithium battery gel electrolyte, its preparation method, and its application. Background Technology

[0002] On the negative electrode side, the high reactivity of lithium metal triggers continuous side reactions between the lithium metal negative electrode and the electrolyte, leading to the formation of an unstable solid-state electrolyte interface (SEI) and inducing the growth of lithium dendrites. On the positive electrode side, lithium cobalt oxide (LiCoO2LCO) is prone to electrolyte-triggered surface instability under high voltage (>4.45V), including cobalt dissolution, lattice oxygen release, and structural reconstruction, further exacerbating interface degradation and capacity decay. All of these problems are closely related to the stability of the electrolyte at the electrode interface.

[0003] Therefore, developing an electrolyte system that can simultaneously stabilize the positive and negative electrode interfaces remains a key issue that needs to be addressed in high-voltage lithium metal batteries. Summary of the Invention

[0004] In view of this, in order to solve at least one of the above-mentioned technical problems, it is necessary to provide a novel fluorinated aromatic multifunctional lithium battery gel electrolyte.

[0005] In addition, this application also provides a method for preparing the electrolyte and its applications.

[0006] In a first aspect, this application provides a novel fluorinated aromatic multifunctional lithium battery gel electrolyte, comprising: a base electrolyte, a fluorinated aromatic additive, a polymerizable monomer containing trifluoromethyl groups, a crosslinking agent, and an initiator. The polymerizable monomer and the crosslinking agent can undergo a free radical polymerization reaction under the action of the initiator to form a three-dimensional crosslinked polymer network. The base electrolyte contains lithium hexafluorophosphate and an organic solvent. The fluorinated aromatic additive is an aromatic compound containing tetrafluoroethoxy groups, and the structure of the tetrafluoroethoxy-containing aromatic compound is shown in formula (I). F—X—O-CF2-CF2H, formula (I), where X is an aromatic ring, and one or more hydrogen atoms on the aromatic ring are substituted by substituents selected from C. 1-4 Alkyl, C 1-4 At least one of alkoxy and halogen; the aromatic compound containing tetrafluoroethoxy includes at least one of 1-(1,1,2,2-tetrafluoroethoxy)-4-fluorobenzene and its derivatives, and 1-(1,1,2,2-tetrafluoroethoxy)-2,4-difluorobenzene and its derivatives.

[0007] Based on the first aspect, in some embodiments of this application, the polymerizable monomer includes at least one of 3,5-bis(trifluoromethyl)styrene, p-trifluoromethylstyrene, m-trifluoromethylstyrene, o-trifluoromethylstyrene, 2,4-bis(trifluoromethyl)styrene, 2,5-bis(trifluoromethyl)styrene, 4-vinyltrifluorotoluene, p-trifluoromethylphenyl acrylate, p-trifluoromethylphenyl methacrylate, and derivatives thereof.

[0008] Based on the first aspect, in some embodiments of this application, the weight ratio of the base electrolyte, the fluorinated aromatic additive, the polymerizable monomer, the crosslinking agent and the initiator is (85~92):(6~10):(3~6):(2~4):(0.05~0.2).

[0009] Based on the first aspect, in some embodiments of this application, in the basic electrolyte, the organic solvent includes diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate, wherein the weight ratio of diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate is (0.8~1.2):(0.8~1.2):(1.3~1.7); and / or in the basic electrolyte, the weight ratio of lithium hexafluorophosphate to the organic solvent is (0.10~0.18):1.

[0010] Based on the first aspect, in some embodiments of this application, the crosslinking agent includes at least one of triethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, and derivatives thereof; and / or, the initiator includes at least one of azobisisobutyronitrile and derivatives thereof.

[0011] Secondly, this application provides a method for preparing a novel fluorinated aromatic multifunctional lithium battery gel electrolyte, comprising: dissolving lithium hexafluorophosphate in an organic solvent to obtain a basic electrolyte; adding a fluorinated aromatic additive to the basic electrolyte and mixing to obtain a mixed solution, wherein the fluorinated aromatic additive is an aromatic compound containing a tetrafluoroethoxy group, and the structure of the aromatic compound containing the tetrafluoroethoxy group is shown in formula (I): F—X—O-CF2-CF2H, formula (I), wherein X is an aromatic ring, and one or more hydrogen atoms on the aromatic ring are substituted by substituents selected from C 1-4 Alkyl, C 1-4 At least one of alkoxy and halogen; add a polymerizable monomer containing trifluoromethyl, a crosslinking agent and an initiator to the mixture, stir to obtain a precursor solution; and heat the precursor solution to allow the polymerizable monomer and the crosslinking agent to undergo a free radical polymerization reaction in the presence of the initiator to form a three-dimensional crosslinked polymer network, and cure to obtain the novel fluorinated aromatic multifunctional lithium battery gel electrolyte.

[0012] Based on the second aspect, in some embodiments of this application, when the precursor solution is heated, the heating temperature is 50°C to 70°C and the heating time is 2h to 8h.

[0013] Based on the second aspect, in some embodiments of this application, the aromatic compound of the tetrafluoroethoxy group includes at least one of 1-(1,1,2,2-tetrafluoroethoxy)-4-fluorobenzene, 1-(1,1,2,2-tetrafluoroethoxy)-2,4-difluorobenzene, and its derivatives; and / or, the polymerizable monomer containing trifluoromethyl groups includes at least one of 3,5-bis(trifluoromethyl)styrene, p-trifluoromethylstyrene, m-trifluoromethylstyrene, o-trifluoromethylstyrene, 2,4-bis(trifluoromethyl)styrene, 2,5-bis(trifluoromethyl)styrene, 4-vinyltrifluorotoluene, p-trifluoromethylphenyl acrylate, p-trifluoromethylphenyl methacrylate, and its derivatives.

[0014] Thirdly, this application provides an electrochemical device comprising a positive electrode, a negative electrode, and the aforementioned novel fluorinated aromatic multifunctional lithium battery gel electrolyte located between the positive and negative electrode.

[0015] This application provides a novel fluorinated aromatic multifunctional lithium-ion battery gel electrolyte. By introducing an aromatic additive containing tetrafluoroethoxy and a polymerizable monomer containing trifluoromethyl, and with the aid of an initiator, free radical polymerization occurs to form a three-dimensional cross-linked polymer network. Based on the synergistic effect between the components, on the one hand, the ether oxygen sites in the aromatic additive containing tetrafluoroethoxy can preferentially coordinate with lithium ions, thereby regulating the solvation structure of lithium ions; on the other hand, the three-dimensional network formed by the polymerization of the polymerizable monomer containing trifluoromethyl helps to confine solvent molecules and construct a lithium fluoride-rich interface layer on the electrode surface, thereby stabilizing the electrode interface chemistry. Thus, this application achieves synergistic regulation of the lithium-ion solvation structure and the electrode interface chemistry. Specifically, the ether oxygen sites in the aromatic additive containing tetrafluoroethoxy can preferentially coordinate with lithium ions, thereby partially replacing organic solvent molecules into the solvation sheath layer, changing the coordination environment of lithium ions, thereby reducing the activity of free solvent molecules, inhibiting the oxidative decomposition of solvents under high voltage, and promoting the desolvation process of lithium ions to facilitate interface transport.

[0016] Furthermore, the rigid aromatic skeleton and fluorinated structure of this additive help improve the antioxidant stability of the system and enhance the interfacial structural strength. The three-dimensional network formed by the polymerization of the polymerizable monomer containing trifluoromethyl groups can confine solvent molecules to suppress side reactions. The trifluoromethyl groups in the trifluoromethyl group help to build a dense and lithium fluoride-rich solid electrolyte interfacial layer on the positive and negative electrode surfaces, thereby alleviating the electrode corrosion problem caused by the generation of hydrogen fluoride through hydrolysis of lithium hexafluorophosphate.

[0017] Based on the above synergistic effect, the gel electrolyte provided in this application has good ionic conductivity and a wide electrochemical stability window at room temperature. When applied to high-voltage lithium metal batteries, it can achieve relatively stable long-term cycling performance, while inhibiting aluminum current collector corrosion and interfacial impedance growth, thereby improving the battery's overall performance such as safety, cycle life and energy density. Attached Figure Description

[0018] Figure 1 A process flow diagram of the preparation method of the multifunctional gel polymer electrolyte (MGPE) provided in the embodiments of this application.

[0019] Figure 2 Optical photographs of the multifunctional gel polymer electrolyte (MGPE) before and after polymerization, provided for embodiments of this application.

[0020] Figure 3 The Fourier transform infrared (FTIR) spectra of ETPTA, TEGDMA, BTFMS, and MGPE in the embodiments of this application are shown.

[0021] Figure 4 This is a comparison chart of the ionic conductivity at room temperature for Example 1 (MGPE), Comparative Example 1 (BE), and Comparative Example 2 (BEM) of this application.

[0022] Figure 5 The figures show the linear sweep voltammetry (LSV) curves of Examples 1, 1, and 2 of this application at room temperature.

[0023] Figure 6 The graphs show the comparison of the cycle performance of Example 1, Comparative Example 1, and Comparative Example 2 of this application applied to Li||LCO button cells in the voltage range of 2.8-0.5V. Detailed Implementation

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this application pertain. The terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the embodiments of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0025] The following describes some embodiments of this application in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] Conventional liquid electrolytes are prone to oxidative decomposition under high voltage, making it difficult to simultaneously meet the interfacial stability requirements of both the positive and negative electrodes. Gel polymer electrolytes (GPEs), combining the high ionic conductivity of liquid electrolytes with the structural confinement effect of a polymer backbone, are considered an effective solution to alleviate these problems. However, above 4.5V, GPEs still struggle to effectively protect the positive and negative electrode interfaces simultaneously, meaning they cannot simultaneously achieve both antioxidant stability and long-term interfacial stability.

[0027] To address the aforementioned shortcomings, existing technologies attempt to introduce highly fluorinated solvents or additives to improve interfacial stability. However, these methods still face challenges at high voltages, including additive consumption, interfacial reconstruction, and the trade-off between ion transport and interfacial stability. Meanwhile, regarding lithium salt selection, while lithium hexafluorophosphate effectively passivates aluminum current collectors and exhibits high conductivity, it is extremely sensitive to moisture and readily decomposes to produce HF, especially in systems containing fluorinated ethylene carbonate, which further accelerates interfacial degradation.

[0028] Therefore, there is an urgent need to develop an electrolyte system that can synergistically regulate the solvation structure and interface stability in order to simultaneously suppress HF-induced corrosion, stabilize the positive and negative electrode interfaces, and ensure ion transport performance.

[0029] Therefore, this application provides a novel fluorinated aromatic multifunctional lithium battery gel electrolyte, comprising: a base electrolyte, a fluorinated aromatic additive, a polymerizable monomer containing trifluoromethyl, a crosslinking agent, and an initiator. The polymerizable monomer and the crosslinking agent can undergo a free radical polymerization reaction under the action of the initiator to form a three-dimensional crosslinked polymer network. The base electrolyte contains lithium hexafluorophosphate and an organic solvent. The fluorinated aromatic additive is an aromatic compound containing tetrafluoroethoxy, and the structure of the aromatic compound containing tetrafluoroethoxy is shown in formula (I): F—X—O-CF2-CF2H, formula (I), where X is an aromatic ring, and one or more hydrogen atoms on the aromatic ring are replaced by substituents selected from C. 1-4 Alkyl, C 1-4 At least one of alkoxy groups and halogens.

[0030] This application introduces an aromatic additive containing tetrafluoroethoxy groups, along with a polymerizable monomer containing trifluoromethyl groups, a crosslinking agent, and an initiator, into a lithium hexafluorophosphate-based electrolyte. A three-dimensional crosslinked polymer network is formed through free radical polymerization, thereby achieving synergistic regulation of the lithium-ion solvation structure and electrode interface chemistry, thus improving the interfacial chemical stability and structural stability of high-voltage Li||LCO batteries. Specifically, in existing technologies, lithium ions in the basic electrolyte typically coordinate with organic solvent molecules; however, this conventional solvation structure is prone to solvent decomposition under high voltage. To address this, this application introduces the aforementioned tetrafluoroethoxy-containing aromatic additive. Because its ether oxygen sites can preferentially coordinate with lithium ions, it can partially replace solvent molecules in the lithium-ion solvation sheath, thereby altering the lithium-ion coordination environment. With the adjustment of the coordination environment, the activity of free solvent molecules is reduced, thus inhibiting the oxidative decomposition of the solvent under high voltage; simultaneously, the desolvation process of lithium ions is promoted, which is beneficial for ion transport at the interface.

[0031] Meanwhile, in addition to regulating the solvation structure, the tetrafluoroethoxy aromatic additives, with their rigid aromatic skeleton and fluorinated structure, help improve the system's antioxidant stability and enhance interfacial structural strength. Furthermore, the trifluoromethyl polymerizable monomers, under the action of an initiator, form a three-dimensional network through free radical polymerization. This network effectively confines solvent molecules, thereby further suppressing side reactions. Simultaneously, the trifluoromethyl groups also help construct a dense, lithium fluoride-rich solid electrolyte interfacial layer on the positive and negative electrode surfaces. Therefore, the electrode corrosion problem caused by the hydrolysis of lithium hexafluorophosphate to produce hydrogen fluoride can be alleviated.

[0032] Therefore, by synergistically regulating the solvation structure and interface chemistry, this application enables the gel electrolyte prepared in this application to have good ionic conductivity at room temperature and exhibit a wide electrochemical stability window. Thus, when applied to high-voltage lithium metal batteries, it can achieve relatively stable long-term cycling performance, while suppressing aluminum current collector corrosion and interface impedance growth, ultimately improving the overall performance of high-voltage lithium metal batteries, such as safety, cycle life, and energy density.

[0033] In some embodiments, the aromatic compound containing tetrafluoroethoxy groups includes at least one of 1-(1,1,2,2-tetrafluoroethoxy)-4-fluorobenzene and its derivatives, and 1-(1,1,2,2-tetrafluoroethoxy)-2,4-difluorobenzene and its derivatives. By selecting the above-mentioned tetrafluoroethoxy aromatic compounds, it is beneficial to adjust the solvation structure of lithium ions, improve the antioxidant stability of the electrolyte, and enhance the structural strength and compatibility of the electrode / electrolyte interface. It should be noted that the derivatives in "and their derivatives" above refer to compounds obtained by further substituting the aromatic ring based on 1-(1,1,2,2-tetrafluoroethoxy)-4-fluorobenzene or 1-(1,1,2,2-tetrafluoroethoxy)-2,4-difluorobenzene. In some embodiments, polymerizable monomers include at least one of 3,5-bis(trifluoromethyl)styrene, p-trifluoromethylstyrene, m-trifluoromethylstyrene, o-trifluoromethylstyrene, 2,4-bis(trifluoromethyl)styrene, 2,5-bis(trifluoromethyl)styrene, 4-vinyltrifluorotoluene, p-trifluoromethylphenyl acrylate, p-trifluoromethylphenyl methacrylate, and their derivatives. By selecting the aforementioned polymerizable monomers containing trifluoromethyl groups, it is beneficial to form a stable three-dimensional cross-linked polymer network in the free radical polymerization reaction, confining solvent molecules to suppress side reactions. Simultaneously, the trifluoromethyl groups they contain help to construct a dense and lithium fluoride-rich solid electrolyte interface layer on the positive and negative electrode surfaces, thereby alleviating the electrode corrosion problem caused by the generation of hydrogen fluoride through hydrolysis of lithium hexafluorophosphate. It should be noted that the "derivatives" mentioned above refer to compounds obtained by further substituting the aromatic ring based on 3,5-di(trifluoromethyl)styrene, p-trifluoromethylstyrene, m-trifluoromethylstyrene, o-trifluoromethylstyrene, 2,4-di(trifluoromethyl)styrene, 2,5-di(trifluoromethyl)styrene, 4-vinyltrifluorotoluene, p-trifluoromethylphenyl acrylate, or p-trifluoromethylphenyl methacrylate.

[0034] In some embodiments, the organic solvent includes diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate, wherein the weight ratio of diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate is (0.8~1.2):(0.8~1.2):(1.3~1.7). By selecting diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate in the above weight ratio as a mixed solvent, it is beneficial to optimize the ionic conductivity and film-forming stability of the electrolyte, and further improve the interfacial compatibility and cycling performance of the gel electrolyte under high voltage.

[0035] In some embodiments, the crosslinking agent includes at least one selected from triethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, and derivatives thereof. By selecting the above-mentioned crosslinking agent, it is advantageous to provide multiple reaction sites during free radical polymerization, promoting the formation of a stable three-dimensional crosslinked polymer network between polymerizable monomers containing trifluoromethyl groups. It should be noted that the "derivatives thereof" mentioned above refer to compounds obtained by further substituting the ester side chains or acrylate end groups based on triethylene glycol dimethacrylate or ethoxylated trimethylolpropane triacrylate as the base structure.

[0036] In some embodiments, the initiator includes at least one of azobisisobutyronitrile (AIBN) and its derivatives. Using the above-mentioned initiator facilitates the stable initiation of the free radical polymerization reaction between the trifluoromethyl-containing polymerizable monomer and the crosslinking agent under mild heating conditions, thereby forming a uniform three-dimensional crosslinked polymer network. It should be noted that the "derivatives" mentioned above refer to compounds obtained by substituting the alkyl groups on both sides of the azo group into the AIBN base structure, which retains the free radical initiation activity of azo initiators. In some embodiments, the weight ratio of the base electrolyte, fluorinated aromatic additive, trifluoromethyl-containing polymerizable monomer, crosslinking agent, and initiator is (85~92):(6~10):(3~6):(2~4):(0.05~0.2). By controlling the weight ratio of the above components within the appropriate range, it is beneficial to form a stable three-dimensional crosslinked polymer network while balancing ion transport performance and interfacial stability.

[0037] In some embodiments, the weight ratio of lithium hexafluorophosphate to organic solvent is (0.10~0.18):1. By controlling the weight ratio of lithium hexafluorophosphate to organic solvent within the above-mentioned suitable range, it is beneficial to balance the ionic conductivity and interfacial wettability of the electrolyte.

[0038] This application also provides a method for preparing a novel fluorinated aromatic multifunctional lithium battery gel electrolyte, comprising: Step S1: Dissolve lithium hexafluorophosphate in an organic solvent to obtain a basic electrolyte.

[0039] This step helps to form a basic electrolyte with high ionic conductivity, providing a lithium-ion-containing liquid environment for subsequent polymerization reactions.

[0040] Step S2: Add a fluorinated aromatic additive to the base electrolyte and mix to obtain a mixture; the fluorinated aromatic additive is an aromatic compound containing a tetrafluoroethoxy group, the structure of which is shown in formula (I): F—X—O-CF2-CF2H, formula (I), where X is an aromatic ring, and one or more hydrogen atoms on the aromatic ring are replaced by substituents selected from C. 1-4Alkyl, C 1-4 At least one of alkoxy groups and halogens.

[0041] This step facilitates the introduction of ether oxygen sites and rigid aromatic skeletons that can participate in lithium ion coordination, thereby initially regulating the solvation structure and enhancing antioxidant capacity.

[0042] Step S3: Add a polymerizable monomer containing trifluoromethyl, a crosslinking agent, and an initiator to the mixture, stir, and obtain a precursor solution.

[0043] This step helps to ensure that the components are mixed evenly, providing a homogeneous reaction system for the subsequent free radical polymerization reaction, thereby ensuring the uniform formation of the three-dimensional cross-linked network.

[0044] Step S4: The precursor solution is heated to allow the polymerizable monomer containing trifluoromethyl groups and the crosslinking agent to undergo a free radical polymerization reaction in the presence of the initiator, forming a three-dimensional crosslinked polymer network to obtain a novel fluorinated aromatic multifunctional lithium battery gel electrolyte.

[0045] This step facilitates the formation of a three-dimensional cross-linked network through in-situ polymerization, confining solvent molecules and suppressing side reactions. At the same time, it enables the trifluoromethyl groups to construct a lithium fluoride-rich protective layer on the electrode surface, ultimately obtaining a gel electrolyte with both good ionic conductivity and high voltage stability.

[0046] In some embodiments, when the precursor solution is heated, the heating temperature is 50°C to 70°C, and the heating time is 2 hours to 8 hours. This is beneficial for fully initiating the free radical polymerization reaction under mild conditions, allowing the precursor solution to uniformly solidify into a stable three-dimensional cross-linked polymer network, while avoiding side reactions or electrolyte decomposition caused by excessively high temperatures or prolonged heating times.

[0047] Compared with the prior art, the novel fluorinated aromatic multifunctional lithium battery gel electrolyte provided in this application has the following beneficial effects: 1. This application introduces an aromatic additive containing tetrafluoroethoxy to preferentially coordinate its ether oxygen sites with lithium ions, thereby changing the solvation structure. At the same time, it combines a dense lithium fluoride-rich interface layer formed by polymerizing a polymerizable monomer containing trifluoromethyl groups, which can effectively alleviate the corrosion of high-voltage cathodes by HF and improve the long-term stability of the electrode / electrolyte interface.

[0048] 2. This application utilizes the confinement effect of the three-dimensional cross-linked polymer network on solvent molecules and the antioxidant properties of fluorinated aromatic additives to enable the gel electrolyte to maintain good ionic conductivity at room temperature while possessing a wide electrochemical stability window, thus matching high-voltage cathode materials above 4.45V.

[0049] 3. This application utilizes a three-dimensional network structure formed by polymerizing trifluoromethyl polymerizable monomers and a solid electrolyte interface layer rich in lithium fluoride to suppress lithium dendrite growth and side reactions in the long term, while reducing the risk of aluminum current collector corrosion and interface impedance growth, thereby enabling high-voltage lithium metal batteries to achieve more stable long-term cycle performance and higher safety.

[0050] This application also provides an electrochemical device comprising a positive electrode, a negative electrode, and the aforementioned novel fluorinated aromatic multifunctional lithium battery gel electrolyte located between the positive and negative electrode plates. Because this gel electrolyte possesses good ionic conductivity and a wide electrochemical stability window, and can effectively control the lithium-ion solvation structure and construct a dense interface layer rich in lithium fluoride on the electrode surface, this electrochemical device exhibits relatively stable cycle performance and high safety under high voltage.

[0051] The present application will be further described below with reference to specific embodiments and comparative examples.

[0052] The English abbreviations and Chinese names of some chemical components appearing in the examples and comparative examples are as follows: LiPF6: Lithium hexafluorophosphate. DEC: Diethyl carbonate. EMC: Ethyl methyl carbonate. FEC: Fluorinated vinyl carbonate. TFEOB: 1,1,2,2-Tetrafluorophenylethyl ether. BTFMS: 3,5-Bis(trifluoromethyl)styrene. TEGDMA: Triethylene glycol dimethacrylate. ETPTA: Ethoxylated trimethylolpropane triacrylate. AIBN: Azobisisobutyronitrile.

[0053] Example 1 Step 1: Dissolve 1M LiPF6 in an organic solvent formed by DEC:EMC:FEC in a volume ratio of 1:1:1 to obtain a basic electrolyte, labeled BE.

[0054] Step 2: Mix 1.0 mL of BE with 0.10 mL of TFEOB to obtain a liquid electrolyte containing TFEOB, labeled as BEM.

[0055] Step 3: Add 0.0685g of BTFMS, 0.0102g of TEGDMA and 0.0304g of ETPTA to 1.0mL of BEM, stir thoroughly to obtain the precursor solution.

[0056] Step 4: Add 0.0014 g of AIBN to the precursor solution as a thermal initiator.

[0057] Step 5: Place the precursor solution obtained in Step 4 in a vacuum oven and heat at 60°C for 4 hours to carry out free radical polymerization, and obtain a translucent multifunctional gel polymer electrolyte, labeled as MGPE.

[0058] Comparative Example 1 Step 1: Prepare the basic electrolyte BE according to Step 1 of Example 1.

[0059] Step 2: Use BE directly as the electrolyte without adding any additives or monomers, and do not carry out a polymerization reaction.

[0060] Comparative Example 2 Step 1: Prepare the basic electrolyte BE according to Step 1 of Example 1.

[0061] Step 2: Prepare the electrolyte BEM containing TFEOB according to Step 2 of Example 1.

[0062] Step 3: Use BEM directly as the electrolyte, without adding monomers or crosslinking agents, and without carrying out a polymerization reaction.

[0063] Preparation of the positive electrode: The positive electrode was prepared by slurry coating. Lithium cobalt oxide (LiCoO2), Super P as the conductive agent, and polyvinylidene fluoride (PVDF, type 5130) as the binder were weighed out at a mass ratio of 8:1:1. All materials were dissolved in anhydrous N-methylpyrrolidone (NMP) and magnetically stirred for 2-4 hours until a uniform, flowing black slurry was formed. The slurry was uniformly coated onto a 16 μm thick aluminum foil current collector using a doctor blade automatic coating machine. The doctor blade gap was set to 180 μm, and the coating speed was 30 mm / s. The coated electrode was first pre-dried in a 120℃ forced-air oven for 4 hours to remove most of the NMP solvent, and then transferred to a 120℃ vacuum oven (-0.095 MPa) for further drying for 12 hours to reduce the residual solvent to below 500 ppm. After drying, the electrode sheets are rolled by a roller press, and finally cut into circular positive electrode sheets with a diameter of 12 mm using a manual punching machine for later use.

[0064] Fabrication of coin cells: The coin cells used were of the CR2032 model. All assembly operations were performed in a glove box filled with high-purity argon gas, where the water and oxygen content was below 0.1 ppm. A lithium metal sheet (15.6 mm in diameter, 0.45 mm in thickness, 99.9% purity) was used as the negative electrode, and a Celgard 2400 polypropylene membrane (19 mm in diameter, 25 μm in thickness) was used as the separator. The electrolyte was a mixture of 1 M LiPF6 dissolved in diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate in a 1:1:1 volume ratio, with a specific amount of fluorinated aromatic additives added. The assembly sequence from bottom to top was as follows: First, the positive electrode shell (CR2032 stainless steel positive electrode shell, opening upwards) was placed. Then, the prepared lithium cobalt oxide positive electrode sheet, coated side down, was placed in the center of the positive electrode shell, with the aluminum foil side in contact with the bottom of the shell. 30 μL of electrolyte was dropped onto the positive electrode sheet to uniformly wet its surface. Then cover with the separator, ensuring it completely centers and covers the positive electrode. Add 30 μL of electrolyte to the center of the separator. Next, place the negative lithium electrode (bright side facing the separator), the stainless steel gasket (15 mm diameter, 0.5 mm thickness), and the spring sheet (15 mm diameter, 1.0 mm thickness) in sequence. Finally, attach the negative electrode shell, ensuring all layers are aligned. Place the assembled battery in an automatic sealing machine and seal it at 650 psi (approximately 5.2 MPa) for 2 seconds. After sealing, test the open-circuit voltage with a multimeter. An OCV greater than 2.5 V indicates good contact, with no edge deformation or electrolyte leakage. Let the assembled battery stand at room temperature for 10 hours to allow the electrolyte to fully wet the electrodes before electrochemical testing.

[0065] Ionic conductivity testing: The AC impedance method was used in a CR2032 stainless steel symmetrical battery (SS|electrolyte|SS). After assembly in an argon glove box, the battery was allowed to stand for 12 hours to ensure sufficient electrolyte wetting and stable interfacial contact. The test frequency range was 1MHz to 1Hz, with an AC disturbance voltage of 10mV, and the test was conducted at a constant temperature of 25°C. The electrolyte bulk resistance was obtained from the high-frequency intercept of the Nyquist plot. Ionic conductivity was calculated by combining the electrolyte thickness and the effective contact area of ​​the electrodes. The test subjects were the basic electrolyte BE, the electrolyte BEM containing TFEOB, and the multifunctional gel polymer electrolyte MGPE. Ionic conductivity was calculated using the formula σ=L / (R·S).

[0066] Linear sweep voltammetry test: A CR2032 coin cell (SS|electrolyte|Li) was assembled using stainless steel as the working electrode, lithium metal as the counter electrode and reference electrode. After assembly in an argon glove box, the cell was allowed to stand at room temperature for 12 hours. The test voltage range was from open circuit voltage to 6.0V (vs. Li). + / Li), scan rate 0.5 mV·s -1The oxidative stability of the electrolyte was tested at room temperature, and the test subjects were BE, BEM and MGPE.

[0067] Fourier transform infrared spectroscopy (FTIR) test: The test was conducted in attenuated total reflectance (ATR) mode, with a scanning range of 4000-400 cm⁻¹. -1 The resolution is 4cm. -1 The number of scans was 32, and the test was conducted at room temperature.

[0068] Battery cycle performance test: Assemble Li||LCO coin cells and first perform 3 activation cycles at a current density of 0.2C. Then, conduct long-term cycle tests at a rate of 0.5C, a voltage range of 2.8-4.5V, and a temperature of 25°C. Record the capacity retention rate after 400 cycles. BE, BEM, and MGPE were used as electrolytes for the test subjects.

[0069] Discharge specific capacity test: The assembled CR2032 coin cell was subjected to constant current charge-discharge testing using a LAND CT2001A battery testing system at a temperature of 25±1℃ (controlled by a constant temperature chamber). The positive electrode was lithium cobalt oxide, and the negative electrode was a lithium metal sheet. The charge-discharge voltage range was set to 2.8 V to 4.5 V (vs. Li). + / Li). First, the battery was activated and cycled at a 0.2C rate for 3 weeks, with the 1C rate current density calculated at 180 mA / g (corresponding to 180 mAh / g of the theoretical specific capacity of lithium cobalt oxide).

[0070] The experimental test results of the examples and comparative examples are shown in Table 1.

[0071] Table 1 Results analysis: Figure 2 Optical photographs of the multifunctional gel polymer electrolyte (MGPE) provided in Example 1 before and after polymerization, wherein Figure 2 Figure (a) shows the precursor solution state before polymerization. Figure 2 Figure (b) shows the semi-transparent gel state after polymerization. As shown, the MGPE precursor is a transparent solution with good fluidity before polymerization, which is conducive to its full penetration and uniform distribution in the electrode channels and interface regions. After in-situ polymerization, the system gradually transforms from a liquid state to a semi-transparent gel electrolyte, forming a three-dimensional cross-linked network structure inside. This structural transformation not only inhibits the migration of the liquid electrolyte but also helps to fix solvent molecules and regulate ion transport pathways, thereby improving the stability of the electrode / electrolyte interface.

[0072] Figure 3Fourier transform infrared (FTIR) spectra of the MGPE sample prepared in Example 1 and the three monomer raw materials (ETPTA, TEGDMA, and BTFMS) used in it. The results show that MGPE contains [a specific component] located at 1630 cm⁻¹. -1 The characteristic peaks of the nearby C=C stretching vibration almost completely disappeared after polymerization, indicating that the unsaturated double bonds in the system had essentially participated in the polymerization reaction. This change suggests that the precursor underwent sufficient cross-linking transformation, and the system transitioned from a monomer / oligomer state to a stable polymeric network structure, thus achieving a high degree of polymerization transformation.

[0073] Figure 4 This study compares the ionic conductivity of three electrolytes (BE, BEM, and MGPE) in Example 1 and Comparative Examples 1 and 2 at room temperature. The tests were conducted using AC impedance spectroscopy in a CR2032 stainless steel symmetric cell (SS|electrolyte|SS), with a frequency range of 1 MHz to 1 Hz, an AC perturbation voltage of 10 mV, and a constant temperature of 25°C. The results show that the ionic conductivity of MGPE in Example 1 is on the same order of magnitude as that of BE in Comparative Example 1 and BEM in Comparative Example 2, and the difference is within an acceptable range. This indicates that despite the introduction of a polymer matrix, MGPE does not significantly sacrifice ion transport capacity and still exhibits good room-temperature conductivity, meeting the basic operating requirements of solid-state batteries.

[0074] Figure 5 Linear sweep voltammetry (LSV) curves of Example 1 (MGPE), Comparative Example 1 (BE), and Comparative Example 2 (BEM) at room temperature are shown. The tests used stainless steel as the working electrode and lithium metal as both the counter and reference electrode (SS|electrolyte|Li), with the voltage range from open-circuit voltage to 6.0V (vs. Li). + / Li), scan rate 0.5 mV·s -1 The results showed that BE exhibited a significant oxidation current response at approximately 3.8 V, indicating that it undergoes electrolyte decomposition at lower potentials and has limited oxidation stability. After introducing TFEOB, the oxidation onset potential of BEM significantly increased to approximately 4.5 V, suggesting that the additives and polymer network, to some extent, suppressed the high-potential decomposition of solvent molecules and improved the system's antioxidant capacity. Furthermore, MGPE maintained a low and stable background current throughout the entire scanning range (up to 5.0 V), with no obvious oxidation peaks or current spikes observed, demonstrating superior electrochemical stability. This improvement is mainly attributed to the synergistically regulated solvation structure and restricted molecular motion behavior in MGPE: on the one hand, the optimized Li... +The solvation environment reduces the activity of free solvent molecules; on the other hand, the spatial confinement of the electrolyte by the polymer network effectively suppresses side reactions at the electrode interface. Therefore, MGPE can remain stable over a wide voltage window, providing a reliable electrolyte basis for matching high-voltage cathode materials.

[0075] Figure 6 This study compares the cycling performance of Li||LCO coin cells using BE, BEM, and MGPE electrolytes in the 2.8–4.5 V voltage range. All cells were first activated at a current density of 0.2C for three cycles, followed by long-term cycling tests at 0.5C. The results show that Li|BE|LCO and Li|BEM|LCO cells exhibited significant capacity decay and low capacity retention in the later stages of cycling. In contrast, the MGPE-based cell maintained a high capacity retention after the same number of cycles, demonstrating superior long-term cycling stability. This result is attributed to the synergistic effect of the tetrafluoroethoxy aromatic additives and the trifluoromethyl polymer network in MGPE, which effectively suppresses degradation behaviors such as cobalt dissolution on the cathode surface, lattice oxygen release, and interface reconstruction, while also mitigating HF corrosion of the electrode, thereby delaying the increase in interfacial impedance and the intensification of cell polarization.

[0076] The above description describes some specific embodiments of this application, but in actual applications, the application should not be limited to these embodiments. For those skilled in the art, other modifications and alterations made based on the technical concept of this application should fall within the protection scope of this application.

Claims

1. A novel fluorinated aromatic multifunctional lithium battery gel electrolyte, characterized in that, include: The electrolyte comprises a base electrolyte, a fluorinated aromatic additive, a polymerizable monomer containing trifluoromethyl groups, a crosslinking agent, and an initiator. The polymerizable monomer and the crosslinking agent undergo free radical polymerization under the action of the initiator to form a three-dimensional crosslinked polymer network. The base electrolyte contains lithium hexafluorophosphate and an organic solvent. The fluorinated aromatic additive is an aromatic compound containing a tetrafluoroethoxy group, and the structure of the tetrafluoroethoxy-containing aromatic compound is shown in formula (I). F—X—O-CF2-CF2H, formula (I), Wherein, X is an aromatic ring, and one or more hydrogen atoms on the aromatic ring are replaced by substituents selected from C. 1-4 Alkyl, C 1-4 At least one of alkoxy groups and halogens; The aromatic compounds containing tetrafluoroethoxy groups include at least one of 1-(1,1,2,2-tetrafluoroethoxy)-4-fluorobenzene and its derivatives, and 1-(1,1,2,2-tetrafluoroethoxy)-2,4-difluorobenzene and its derivatives.

2. The novel fluorinated aromatic multifunctional lithium battery gel electrolyte according to claim 1, characterized in that, The polymerizable monomers include at least one of 3,5-bis(trifluoromethyl)styrene, p-trifluoromethylstyrene, m-trifluoromethylstyrene, o-trifluoromethylstyrene, 2,4-bis(trifluoromethyl)styrene, 2,5-bis(trifluoromethyl)styrene, 4-vinyltrifluorotoluene, p-trifluoromethylphenyl acrylate, p-trifluoromethylphenyl methacrylate, and derivatives thereof.

3. The novel fluorinated aromatic multifunctional lithium battery gel electrolyte according to claim 1, characterized in that, The weight ratio of the base electrolyte, the fluorinated aromatic additive, the polymerizable monomer, the crosslinking agent, and the initiator is (85~92):(6~10):(3~6):(2~4):(0.05~0.2).

4. The novel fluorinated aromatic multifunctional lithium battery gel electrolyte according to claim 1, characterized in that, In the basic electrolyte, the organic solvent comprises diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate, wherein the weight ratio of diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate is (0.8~1.2):(0.8~1.2):(1.3~1.7); and / or, In the basic electrolyte, the weight ratio of lithium hexafluorophosphate to the organic solvent is (0.10~0.18):

1.

5. The novel fluorinated aromatic multifunctional lithium battery gel electrolyte according to claim 1, characterized in that, The crosslinking agent includes at least one of triethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, and its derivatives; and / or, The initiator includes at least one of azobisisobutyronitrile and its derivatives.

6. A method for preparing a novel fluorinated aromatic multifunctional lithium battery gel electrolyte, characterized in that, include: Lithium hexafluorophosphate is dissolved in an organic solvent to obtain a basic electrolyte; Fluorinated aromatic additives are added to the basic electrolyte and mixed to obtain a mixture; The fluorinated aromatic additive is an aromatic compound containing a tetrafluoroethoxy group, the structure of which is shown in formula (I): F—X—O-CF2-CF2H, formula (I), where X is an aromatic ring, and one or more hydrogen atoms on the aromatic ring are substituted by substituents selected from C. 1-4 Alkyl, C 1-4 At least one of alkoxy groups and halogens; Add a polymerizable monomer containing trifluoromethyl, a crosslinking agent, and an initiator to the mixture, and stir to obtain a precursor solution; as well as The precursor solution is heated to allow the polymerizable monomer and the crosslinking agent to undergo a free radical polymerization reaction in the presence of the initiator, forming a three-dimensional crosslinked polymer network, which is then cured to obtain the novel fluorinated aromatic multifunctional lithium battery gel electrolyte.

7. The preparation method according to claim 6, characterized in that, When the precursor solution is heated, the heating temperature is 50℃~70℃ and the heating time is 2h~8h.

8. The preparation method according to claim 6, characterized in that, The aromatic compounds of the tetrafluoroethoxy group include at least one of 1-(1,1,2,2-tetrafluoroethoxy)-4-fluorobenzene, 1-(1,1,2,2-tetrafluoroethoxy)-2,4-difluorobenzene, and derivatives thereof; and / or, The polymerizable monomers containing trifluoromethyl groups include at least one of 3,5-bis(trifluoromethyl)styrene, p-trifluoromethylstyrene, m-trifluoromethylstyrene, o-trifluoromethylstyrene, 2,4-bis(trifluoromethyl)styrene, 2,5-bis(trifluoromethyl)styrene, 4-vinyltrifluorotoluene, p-trifluoromethylphenyl acrylate, p-trifluoromethylphenyl methacrylate, and derivatives thereof.

9. An electrochemical device, characterized in that, The electrochemical device includes a positive electrode, a negative electrode, and a novel fluorinated aromatic multifunctional lithium battery gel electrolyte as described in any one of claims 1 to 5, located between the positive and negative electrode.

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