Single ion conductive gel polymer electrolyte and method for producing same

Abstract

A single ion conductive gel polymer electrolyte comprises 25-40% of a fluorine-containing compound converted into a carbon double bond of a main chain and 35-55 wt% of a lithium salt. The polymer ensures anion immobilization, thereby limiting conductivity primarily to lithium ions. By adding an optional additive such as PEGMEMA in a specific weight ratio, the electrolyte achieves high ionic conductivity and strong film-forming properties. The preparation method of the gel polymer electrolyte comprises the following steps: mixing the fluorine-containing compound, the lithium salt and the free radical initiator, and then carrying out in-situ crosslinking. The obtained self-supporting film shows enhanced lithium metal negative electrode stability and inhibits formation of dendritic crystals. Also disclosed is a lithium secondary battery in which the gel polymer electrolyte layer is positioned between a positive electrode and a negative electrode, the lithium secondary battery exhibiting a longer cycle life and higher voltage stability.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0166275, filed with the Korean Intellectual Property Office on November 20, 2024, pursuant to 35U.SC §119(a), the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to a single-ion conducting gel polymer electrolyte comprising a fluorine-based compound having carbon double bonds. Background Technology

[0004] As the electric vehicle market grows, the demand for high-capacity batteries that surpass traditional lithium-ion batteries is increasing, which in turn drives the demand for high-energy-density anode and cathode materials that offer excellent energy density and long-term stability.

[0005] With the growth of the battery market, it is necessary to apply batteries with high theoretical capacity (3860mAh g). -1 Lithium metal anodes are used to replace graphite (372mAh g) as traditional anode materials. -1 Furthermore, high-voltage cathode materials are required to improve the energy density of the battery.

[0006] Furthermore, dendrites formed in lithium metal batteries can cause short circuits, posing a fire risk. To address this issue, single-ion conductors with high lithium mobility numbers can be used to suppress dendrite growth and achieve uniform lithium-ion deposition, or a lithium cathode protective layer can be introduced to form a stable SEI layer.

[0007] On the other hand, the use of polymers obtained by copolymerizing poly(ethylene glycol) methacrylate (PEGMA) and LiMTFSI as electrolytes for all-solid-state lithium metal batteries is being investigated. However, due to the low lithium-ion conductivity (2.3 × 10⁻⁶ at 25°C), this method is not feasible. -6 S cm -1 The aforementioned polymers are only effective at low cathode capacity and current density (0.2C rate) and have low high voltage stability, making them difficult to apply to NCM-based batteries.

[0008] Therefore, there is a demand for polymer electrolytes that can provide higher ionic conductivity while also enhancing high voltage stability. Summary of the Invention

[0009] The embodiments disclosed herein aim to provide a gel polymer electrolyte with high single-ion conductivity and a method for manufacturing the same.

[0010] Furthermore, embodiments of this disclosure aim to provide a gel polymer electrolyte and a method for manufacturing the same, capable of suppressing dendrite growth that occurs when using a high-density electrolyte and a high-voltage positive electrode.

[0011] The gel polymer electrolyte according to embodiments of this disclosure is a single-ion conductive gel polymer electrolyte comprising a fluorinated compound having carbon double bonds and a lithium salt.

[0012] In some respects, a carbon double bond can be a carbon-carbon double bond. It can also include other carbon double bonds, such as a carbon-nitrogen double bond.

[0013] In some respects, carbon double bonds can be introduced into fluorinated compounds. For example, the resulting fluorinated compound can be treated to introduce carbon double bonds. For instance, fluoropolymers or oligomers can be modified in one or more synthetic steps to include or introduce carbon double bonds, such as carbon-carbon double bonds.

[0014] Based on the total weight of the fluorinated compound with carbon double bonds and the lithium salt, the lithium salt content can be from 35 wt% to 55 wt%.

[0015] In fluorinated compounds with carbon double bonds, 30% to 35% of the main chain can be double bonds.

[0016] The lithium salt may include one or more selected from lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylate, and lithium 3-(2-methylprop-2-enoyloxy)prop-1-sulfonate.

[0017] Fluorine-containing compounds can be selected from polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, and polyvinylidene fluoride-hexafluoroethylene copolymer.

[0018] The gel polymer electrolyte may also include additives composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA).

[0019] The content of the additive can be from 10 wt% to 40 wt%, depending on the total weight of the fluorinated compound with carbon double bonds and the lithium salt.

[0020] Gel polymer electrolytes may also include impregnated liquid electrolytes.

[0021] In one aspect, a method for manufacturing a gel polymer electrolyte is provided, the method comprising: a) preparing a mixture by mixing a fluorinated compound having carbon double bonds, a lithium salt, and a free radical initiator; b) applying the mixture to a base material; and subsequently c) crosslinking the mixture. In a preferred aspect, the amount of lithium salt added is from about 35 wt% to 55 wt% based on the total weight of the fluorinated compound, the lithium salt, and the crosslinking agent. In a preferred aspect, after the mixture is applied to the base material, the mixture can be crosslinked in situ.

[0022] In another aspect, the method of manufacturing the gel polymer electrolyte disclosed herein may include: preparing a mixture by mixing a fluorinated compound having carbon double bonds, a lithium salt and a free radical initiator; and applying the mixture to a substrate followed by an in-situ crosslinking reaction.

[0023] The amount of lithium salt added can be from 35 wt% to 55 wt%, depending on the total weight of the fluorinated compound, lithium salt, and crosslinking agent.

[0024] In some respects, fluorinated compounds with carbon double bonds can be obtained by mixing fluorinated compounds with alkaline substances to form fluorinated compounds with carbon double bonds.

[0025] The alkaline substance may be one or more selected from ethylenediamine (EDA), isopropylethylenediamine (IEDA), 1,3-phenylenediamine (PDA), 1,5-naphthyldiamine (NDA), 2,4,4-trimethyl-1 or 6-hexanediamine (THDA), dicumyl peroxide (DCP), benzoyl peroxide, bisphenol A, and methyldiamine.

[0026] The fluorinated compound may be one or more selected from polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, and polyvinylidene fluoride-hexafluoroethylene copolymer.

[0027] The step of mixing a fluorinated compound and an alkaline substance to form a fluorinated compound with carbon double bonds may include stirring the fluorinated compound and the alkaline substance at room temperature for 60 to 100 hours.

[0028] The lithium salt may include one or more selected from lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylate, and lithium 3-(2-methylprop-2-enoyloxy)prop-1-sulfonate.

[0029] When preparing a mixture by mixing a fluorinated compound with carbon double bonds, a lithium salt, and a free radical initiator, an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) can also be mixed in.

[0030] The amount of additives can be from 10 wt% to 40 wt%, depending on the total weight of the fluorinated compound with carbon double bonds and the lithium salt.

[0031] Another embodiment of this disclosure may be a lithium secondary battery, comprising: a positive electrode layer; a negative electrode layer; and an electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein the electrolyte layer comprises a gel polymer electrolyte layer, and the gel polymer electrolyte layer comprises the aforementioned gel polymer electrolyte.

[0032] The gel polymer electrolyte according to the embodiments of this disclosure has the advantage of high single-ion conductivity.

[0033] A method for manufacturing a gel polymer electrolyte according to another embodiment of the present disclosure has the advantage of being able to manufacture a gel polymer electrolyte with high single-ion conductivity.

[0034] In some embodiments, the gel polymer electrolyte, as a single-ion conductive gel polymer electrolyte, includes: a fluorinated compound containing carbon double bonds selected from polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, polyvinylidene fluoride-hexafluoroethylene copolymer, and combinations thereof; and lithium salts selected from lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylate, and lithium 3-(2-methylprop-2-enoyloxy)prop-1-sulfonate, and combinations thereof. The main chain of the fluorinated compound containing carbon double bonds is approximately 25% to 40% double bonds, and the lithium salt content is approximately 35 wt% to 55 wt% based on the total weight of the fluorinated compound and the lithium salt.

[0035] The gel polymer electrolyte may also include additives composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA). The content of the additives can range from approximately 10 wt% to 40 wt%, based on the total weight of the fluorinated compound and the lithium salt.

[0036] As described above, the method and system appropriately include the use of a controller or processor.

[0037] In another embodiment, a vehicle comprising the lithium secondary battery described herein is provided. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a method for manufacturing a gel polymer electrolyte according to an embodiment of the present disclosure.

[0039] Figure 2 It is a schematic cross-sectional view showing the positive electrode layer, electrolyte layer and negative electrode layer of a lithium secondary battery.

[0040] Figure 3 The IR analysis results of the EDA-PVdF prepared according to Preparation Example 1 are shown.

[0041] Figure 4 The XPS analysis results of the EDA-PVdF prepared according to Preparation Example 1 are shown.

[0042] Figure 5 The results of lithium-ion conductivity analysis of the gel polymer electrolytes prepared according to the comparative examples and embodiments are shown.

[0043] Figure 6 (a) is a photograph of the gel polymer electrolyte according to Example 2. Figure 6 (b) shows the results of the crosslinking test.

[0044] Figure 7 This is a photograph showing that the gel polymer electrolyte according to Comparative Example 3 did not separate from the substrate.

[0045] Figure 8 To compare the high-voltage stability measurement results of the lithium metal battery in the experimental example and the lithium metal battery in the experimental example at 4.55V.

[0046] Figure 9 To compare the cycle life characteristics of the lithium metal battery in the experimental example and the lithium metal battery in the experimental example. Detailed Implementation

[0047] Terms such as first, second, and third are used to describe (but are not limited to) various parts, components, regions, layers, and / or portions. These terms are used only to distinguish one part, component, region, layer, or portion from another. Therefore, without departing from the scope of this disclosure, a first part, component, region, layer, or portion described below may be referred to as a second part, component, region, layer, or portion.

[0048] The technical terms used herein are for reference only and are not intended to limit the scope of this disclosure. The singular forms used herein are intended to include the plural forms unless the wording clearly indicates the opposite. In this specification, the term "comprising" is intended to represent a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0049] It should be understood that the terms "vehicle" or "of a vehicle" or other similar terms as used herein generally encompass motor vehicles in general, such as passenger cars (including SUVs), buses, trucks, various commercial vehicles, ships (including various small and large vessels), aircraft, etc., and include hybrid electric vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). Hybrid electric vehicles, as referred to herein, are vehicles with two or more power sources, such as gasoline-powered and electric-powered vehicles.

[0050] The specialized terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the scope of this disclosure. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” used herein include the plural forms as well. These terms are used only to distinguish one component from another and do not limit the nature, order, or sequence of the constituent components. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. Furthermore, the terms “unit,” “device,” “person,” and “module” described in the specification refer to a unit for performing at least one function and operation, and can be implemented by hardware components, software components, and combinations thereof.

[0051] Although exemplary embodiments are described as using multiple units to perform exemplary processes, it should be understood that exemplary processes can also be performed by one or more modules. Furthermore, it should be understood that the term "controller / control unit" refers to a hardware device that includes a memory and a processor and is specifically programmed to perform the processes described herein. The memory is configured to store modules, and the processor is specifically configured to execute said modules to perform one or more processes described in detail below.

[0052] Furthermore, the control logic of this disclosure can be embodied in a non-transient computer-readable medium, including executable program instructions that are executed by a processor, controller, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium can also be distributed across a network-coupled computer system for distributed storage and execution, for example, via a telematics server or a controller area network (CAN).

[0053] Unless otherwise stated or the context clearly indicates, the term "about" as used herein should be understood to mean within the normal tolerance range in the field, such as within 2 standard deviations of the mean. "About" can be understood as a deviation from the stated value of 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01%. All numerical values ​​provided herein are modified by the term "about" unless the context clearly indicates otherwise.

[0054] When it is said that one part is "above" or "on top of" another part, the part can be directly above or above the other part, or there can be an intermediate part. Conversely, when it is said that one part is "directly" above another part, there is no intermediate part.

[0055] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Terms such as those defined in common dictionaries shall be interpreted as having the same meaning as those in the relevant technical literature and this disclosure, and shall not be interpreted as having an idealized or overly formal meaning unless expressly defined herein.

[0056] In this specification, the term "combination of" included in Markush formal expressions refers to one or more mixtures or combinations of the constituent elements described in the Markush formal expressions, and means including one or more of the constituent elements.

[0057] The embodiments of this disclosure will be described in detail below to enable those skilled in the art to readily implement this disclosure. Those skilled in the art will understand that modifications can be made to the described embodiments in various ways without departing from the spirit or scope of this disclosure.

[0058] <Gel Polymer Electrolytes>

[0059] The gel polymer electrolyte according to embodiments of this disclosure may include a fluorinated compound having carbon double bonds and a lithium salt.

[0060] In embodiments of this disclosure, the lithium salt content can be from 35 wt% to 55 wt%, particularly 40 wt% to 55 wt%, or 45 wt% to 55 wt%, based on the total weight of the fluorinated compound with carbon double bonds and the lithium salt. A lithium salt content within this range is preferred because it provides high conductivity for lithium ions and enhances stability at high voltages, thereby enabling excellent cycle life when applied to lithium secondary batteries. If the lithium salt content is below the above range, it is difficult to obtain satisfactory ionic conductivity. If the lithium salt content exceeds the above range, it is difficult to separate the gel polymer electrolyte from the substrate during the manufacturing process, resulting in a decrease in quality.

[0061] Fluorine-containing compounds can be selected from polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, and polyvinylidene fluoride-hexafluoroethylene copolymer.

[0062] The backbone of the fluorinated compound having carbon double bonds can be 25% to 40%, especially 30% to 35%, of double bonds. Preferably, when the carbon double bonds (C=C) fall within the above range, as determined by XPS analysis, the anions are included in the polymer backbone, thereby allowing only lithium ion migration and suppressing dendrite growth caused by uneven lithium ion deposition due to anion migration on the surface of the lithium metal anode.

[0063] Lithium salts can contain both lithium cations and anions. Using lithium salts can suppress battery polarization and the growth of lithium dendrites.

[0064] The lithium salt may include one or more selected from lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylate, and lithium 3-(2-methylprop-2-enoyloxy)prop-1-sulfonate.

[0065] Gel polymer electrolytes may also include additives composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA). This provides the following advantages: increased crosslinking density and lower glass transition temperature of the polymer, which is beneficial for lithium transport and provides additional ionic conductivity.

[0066] In embodiments of this disclosure, the content of the additive can be from 10 wt% to 40 wt% based on the total weight of the fluorinated compound having carbon double bonds and the lithium salt.

[0067] In embodiments of this disclosure, the gel polymer electrolyte may further include an impregnated liquid electrolyte.

[0068] The liquid electrolyte may include one or more selected from ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethylene glycol dimethyl ether, trimethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, succinate, sulfolane, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, adiponitrile, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and dimethylacetamide.

[0069] The liquid electrolyte may also include lithium salts, which may include one or more selected from LiNO3, LiPF6, LiBF6, LiClO4, LiCF3SO3, LiBr and LiI.

[0070] <Method for manufacturing gel polymer electrolytes>

[0071] Figure 1 This is a schematic diagram of a method for manufacturing a gel polymer electrolyte according to an embodiment of the present disclosure.

[0072] In the following text, we will combine Figure 1 A method for manufacturing a gel polymer electrolyte according to embodiments of the present disclosure is described in detail.

[0073] refer to Figure 1 The method for manufacturing a gel polymer electrolyte according to embodiments of the present disclosure may include the following steps: preparing a mixture by mixing a fluorinated compound having carbon double bonds, a lithium salt and a free radical initiator; applying the mixture to a substrate and then performing an in-situ crosslinking reaction.

[0074] Fluorinated compounds with carbon double bonds can be formed by treating fluorinated compounds with an alkali. Specifically, this can be achieved by mixing fluorinated compounds with an alkaline substance to form fluorinated compounds with carbon double bonds.

[0075] In the step of mixing a fluorinated compound with a basic substance to form a fluorinated compound with carbon double bonds, ethylenediamine (EDA), which has a relatively low pKa value, is used.

[0076] Specifically, EDA is used at a molar ratio corresponding to 45% to 55% of the repeating units of the fluorinated compound. If the molar ratio exceeds this range, purification cannot be performed due to cross-linking caused by the defluorination reaction between the chains of the fluorinated compound. Furthermore, if the molar ratio is below the range, carbon double bonds cannot be effectively introduced.

[0077] Fluorine compounds and alkaline substances can be mixed and stirred at room temperature for 60 hours or longer, specifically 60 to 100 hours, 60 to 80 hours, or 65 to 75 hours.

[0078] The fluorinated compound may be selected from one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, and polyvinylidene fluoride-hexafluoroethylene copolymer, specifically, it may be polyvinylidene fluoride (PVDF).

[0079] The alkaline substance may be one or more selected from ethylenediamine (EDA), isopropylethylenediamine (IEDA), 1,3-phenylenediamine (PDA), 1,5-naphthylenediamine (NDA), 2,4,4-trimethyl-1 or 6-hexanediamine (THDA), dicumyl peroxide (DCP), benzoyl peroxide, bisphenol A, and methyldiamine, specifically ethylenediamine (EDA).

[0080] The lithium salt may include one or more selected from lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI) and lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI).

[0081] The initiator may include one or more selected from azobis(isobutyronitrile) (AIBN), benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, tert-butyl peroxide-2-ethylhexanoate, cumyl hydroperoxide, hydrogen peroxide, 2,2-azobis(2-cyanobutane) [2,2-azobis(methylbutyronitrile)] and azobis(isobutyronitrile) (AMVN), specifically azobis(isobutyronitrile) (AIBN).

[0082] It should be noted that in the step of preparing the mixture by mixing a fluorinated compound with carbon double bonds, a lithium salt and a free radical initiator, an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) may also be mixed.

[0083] Based on the total weight of the fluorinated compound with carbon double bonds and the lithium salt, the amount of additives mixed can be from 10 wt% to 40 wt%. When the amount of additives mixed is within the above range, high-quality polymer gel electrolytes can be produced. If the amount of additives mixed exceeds the above range, it is difficult to form a self-supporting polymer gel electrolyte; if the amount of additives mixed is below the above range, the quality of the produced polymer gel electrolyte will decrease.

[0084] <Lithium secondary batteries>

[0085] Figure 2 It is a schematic cross-sectional view showing the positive electrode layer, electrolyte layer and negative electrode layer of a lithium secondary battery.

[0086] refer to Figure 2 (a) The lithium secondary battery according to the embodiments of the present disclosure may include a positive electrode layer 20, a negative electrode layer 10, and an electrolyte layer 30 located between the positive electrode layer and the negative electrode layer. The electrolyte layer 30 may include the aforementioned gel polymer electrolyte layer 31, which may include a gel polymer electrolyte. Since the gel polymer electrolyte has been described in detail above, it will not be described again here.

[0087] It is important to note that the gel polymer electrolyte can be located in the form of a thin film between the negative electrode layer and the electrolyte layer, specifically, a film with a thickness of 30 μm to 40 μm. If the thickness of the gel polymer electrolyte exceeds this range, the initial discharge capacity will decrease; if the thickness is less than this range, the intermediate layer will be damaged during separation from the substrate.

[0088] It should be noted that the positive electrode layer of the lithium secondary battery according to the embodiments of this disclosure may contain positive electrode active material, which is used in the range of charging voltage of 4.3V or lower.

[0089] Preferred embodiments and comparative examples of this disclosure will be described below. However, the following embodiments are merely preferred embodiments of this disclosure, and this disclosure is not limited to these embodiments.

[0090] (Preparation Example 1) Preparation of fluorine-containing compounds with carbon double bonds

[0091] 3 g of polyvinylidene fluoride (PVDF) and 2.8 g of ethylenediamine (EDA) were ultrasonically dispersed in 30 mL of dimethylformamide (DMF) as a solvent, and stirred at room temperature (approximately 25°C) for about 72 hours. The mixture was then precipitated in ethanol and filtered to prepare EDA-PVdF. (Examples and Comparative Examples) Preparation of Gel Polymer Electrolytes

[0092] EDA-PVdF prepared according to the preparation example, lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI) as the lithium salt, and azobisisobutyronitrile (AIBN) as the initiator were added. Subsequently, they were dispersed by ultrasonication for approximately 3 hours and cast onto a glass plate. The resulting product was in-situ crosslinked under vacuum at approximately 70°C for 18 hours to obtain a gel polymer electrolyte. The gel polymer electrolyte was washed with ethanol to remove unreacted lithium salt.

[0093] The weight contents of EDA-PVdF and lithium salt LiMTFSI according to the examples and comparative examples are shown in Table 1 below.

[0094] (Evaluation Example 1: IR Analysis)

[0095] The EDA-PVdF prepared according to Preparation Example 1 was subjected to IR analysis. Specifically, the FT-IR spectra were recorded using a Nicolet 6700 spectrometer in absorption mode with a resolution of 4 cm⁻¹. -1 The vibration frequency range is 600 to 4000 cm. -1 The analysis results are as follows: Figure 3 As shown.

[0096] refer to Figure 3 Through a wavelength of 1650cm -1 The C=C bond signal at the location was confirmed, and according to the preparation example, the double bond was introduced into EDA-PVdF.

[0097] (Evaluation Example 2: XPS Analysis)

[0098] XPS analysis was performed on the EDA-PVdF prepared according to Preparation Example 1. Specifically, X-ray photoelectron spectroscopy (XPS) was performed using a PHI 5000 VersaProbe spectrometer (ULVAC PHI, Japan), with monochromatic Al Kα as the radiation source. The analytical results are as follows: Figure 4 As shown.

[0099] refer to Figure 4 By calculating the area of ​​CC and C=C signals in XPS analysis, it was confirmed that 32% of the EDA-PVdF backbone consists of double bonds.

[0100] (Evaluation Example 3: Ion conductivity analysis)

[0101] The gel polymer electrolytes prepared according to the examples and comparative examples were immersed in liquid electrolytes for approximately 24 hours and used as electrolyte layers to assemble coin cells with a separator / electrolyte / separator structure. The resistance of the coin cells was measured in the temperature range of 10°C to 80°C and converted into lithium-ion conductivity (using a Zahner Electrorik IM6 instrument, at an applied voltage of 10 mV, in the frequency range of 100 Hz to 1 MHz).

[0102] The method for analyzing lithium-ion conductivity is as follows.

[0103] a) Liquid electrolyte impregnation amount is based on 100 parts by weight of gel polymer electrolyte.

[0104] b) Measurements were taken at 30°C. The liquid electrolyte used was a mixture of ethylene carbonate and dimethyl carbonate.

[0105] c) The electrochemical window was measured using a linear sweep voltammetry method.

[0106] The results of lithium-ion conductivity analysis are as follows: Figure 5 As shown in Table 1 below.

[0107] [Table 1]

[0108]

[0109] like Figure 5 As shown in Table 1, it can be confirmed that the lithium-ion conductivity increases with the increase of the LiMTFSI content.

[0110] Figure 6 (a) shows a photograph of the gel polymer electrolyte according to Example 2. Figure 6 (b) shows the results of the crosslinking test.

[0111] refer to Figure 6 (a) It can be confirmed that the gel polymer electrolyte prepared according to Example 2 forms a free-standing morphology after separation from the substrate. (See reference) Figure 6 (b) It can be confirmed that the gel polymer electrolyte prepared according to Example 2 retains its shape and does not dissolve even after being immersed in DMF solvent. This is believed to be due to the introduction of cross-linked structures during the preparation process.

[0112] On the other hand, in Comparative Example 3, the content of lithium salt LiMTFSI was 60 wt%. Due to insufficient PVDF content, the membrane exhibited low crosslinking degree and low elasticity. As a result, the membrane was damaged during separation from the substrate, making it impossible to prepare a gel polymer electrolyte and measure lithium-ion conductivity.

[0113] Figure 7 This is a photograph showing that the gel polymer electrolyte according to Comparative Example 3 did not separate from the substrate.

[0114] (Experimental Example)

[0115] The electrolyte layer structure is achieved using commercially available membrane layers. Specifically, a three-layer polypropylene / polyethylene / polypropylene membrane (PP / PE / PP) is used in electrochemical testing. 2320, thickness: 25 μm) as a separator (electrolyte layer). Preparation of a Li / electrolyte layer ( A comparative example of a lithium metal battery with a 2320) / NCM (NCM900505) structure was prepared, and a Li / gel polymer electrolyte layer / electrolyte layer ( A lithium metal battery of an embodiment with a 2320) / NCM (NCM900505) structure.

[0116] In this case, the gel polymer electrolyte layer in the lithium metal battery of the embodiment is composed of the gel polymer electrolyte of Example 2.

[0117] Figure 8 The results of high-voltage stability measurements of the lithium metal battery in the comparative experiment and the lithium metal battery in the experimental example are shown.

[0118] refer to Figure 8 It can be confirmed that the lithium metal battery of the experimental example, including the layer composed of the gel polymer electrolyte according to Example 2 of this disclosure, has excellent high-voltage stability.

[0119] Figure 9 The results of the cycle life characteristics analysis of the lithium metal battery in the comparative experiment and the lithium metal battery in the experimental example are shown.

[0120] It can be confirmed that the lithium metal battery using the positive electrode NCM900505NCM according to the experimental examples of this disclosure operates at a rate of 1 / 3C and a capacity of 4.0 mAh·cm⁻¹. -2 Under driving voltages of 3.0 to 4.3V, it exhibits a stable cycle life of 300 cycles or more, demonstrating superior performance compared to the lithium metal batteries in the comparative experimental cases.

[0121] While this disclosure has been described in conjunction with exemplary embodiments that are now considered practical, it should be understood that this disclosure is not limited to the disclosed exemplary embodiments. Rather, this disclosure is intended to cover various modifications and equivalents within the spirit and scope of the appended claims.

[0122] Therefore, it should be noted that the actual scope of this disclosure is defined by the appended claims and their equivalents.

Claims

1. A gel polymer electrolyte, which is a single-ion conductive gel polymer electrolyte, comprising: Fluorine-containing compounds with carbon double bonds; and Lithium salts.

2. The gel polymer electrolyte according to claim 1, wherein the carbon double bond is a carbon-carbon double bond.

3. The gel polymer electrolyte according to claim 1, wherein: Based on the total weight of the fluorine-containing compound with carbon double bonds and the lithium salt, the content of the lithium salt is from 35 wt% to 55 wt%.

4. The gel polymer electrolyte according to claim 1, wherein: The main chain of the fluorinated compound having carbon double bonds comprises 30% to 35% double bonds.

5. The gel polymer electrolyte according to claim 1, wherein: The lithium salt is selected from one or more of the following: lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide lithium LiMTFSI, lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide lithium LiSTFSI, lithium methacrylate, and lithium 3-(2-methylprop-2-enoyloxy)prop-1-sulfonate.

6. The gel polymer electrolyte according to claim 1, wherein: The fluorinated compound is selected from one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, and polyvinylidene fluoride-hexafluoroethylene copolymer.

7. The gel polymer electrolyte according to claim 1, wherein: The gel polymer electrolyte also includes an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA).

8. The gel polymer electrolyte according to claim 7, wherein: The content of the additive is from 10 wt% to 40 wt%, based on the total weight of the fluorine-containing compound with carbon double bonds and the lithium salt.

9. The gel polymer electrolyte according to claim 1, wherein: The gel polymer electrolyte also includes an impregnated liquid electrolyte.

10. A method for manufacturing a gel polymer electrolyte, the method comprising the following steps: A mixture was prepared by mixing a fluorinated compound with carbon double bonds, a lithium salt, and a free radical initiator; and The mixture is applied to the substrate, and then Crosslinking of the mixture, The amount of lithium salt added is 35 wt% to 55 wt%, based on the total weight of the fluorine-containing compound with carbon double bonds, the lithium salt, and the crosslinking agent.

11. The method of claim 10, wherein: The fluorinated compound with carbon double bonds is obtained by mixing a fluorinated compound with an alkaline substance to form a fluorinated compound with carbon double bonds.

12. The method according to claim 11, wherein: The alkaline substance is selected from one or more of ethylenediamine (EDA), isopropylethylenediamine (IEDA), 1,3-phenylenediamine (PDA), 1,5-naphthyldiamine (NDA), 2,4,4-trimethyl-1 or 6-hexanediamine (THDA), dicumyl peroxide (DCP), benzoyl peroxide, bisphenol A, and methyldiamine.

13. The method according to claim 11, wherein: The fluorinated compound is selected from one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, and polyvinylidene fluoride-hexafluoroethylene copolymer.

14. The method of claim 11, wherein: The step of mixing the fluorinated compound with the alkaline substance to form the fluorinated compound having carbon double bonds includes: The fluorinated compound and the alkaline substance are stirred at room temperature for 60 hours or longer.

15. The method of claim 10, wherein: The lithium salt is selected from one or more of the following: lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide lithium LiMTFSI, lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide lithium LiSTFSI, lithium methacrylate, and lithium 3-(2-methylprop-2-enoyloxy)prop-1-sulfonate.

16. The method of claim 10, wherein: In the process of providing a mixture by mixing the fluorinated compound having carbon double bonds, the lithium salt, and the free radical initiator, Further mix in an additive consisting of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA).

17. The method of claim 16, wherein: The amount of the additive is 10 wt% to 40 wt% based on the total weight of the fluorine-containing compound with carbon double bonds and the lithium salt.

18. A lithium secondary battery, comprising: Positive electrode layer; Negative electrode layer; and The electrolyte layer located between the positive electrode layer and the negative electrode layer, The electrolyte layer comprises a gel polymer electrolyte layer, and The gel polymer electrolyte layer thereunder comprises the gel polymer electrolyte according to any one of claims 1-9.

19. A gel polymer electrolyte, which is a single-ion conductive gel polymer electrolyte, comprising: Fluorine-containing compounds with carbon double bonds selected from polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, polyvinylidene fluoride-hexafluoroethylene copolymer, and combinations thereof; and Lithium salts selected from lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide lithium LiMTFSI, (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide lithium LiSTFSI, lithium methacrylate, and lithium 3-(2-methylprop-2-enoyloxy)prop-1-sulfonate and combinations thereof, The fluorinated compound having carbon double bonds has a main chain comprising 25% to 40% double bonds, and The lithium salt content is between 35 wt% and 55 wt%, based on the total weight of the fluorine-containing compound and the lithium salt.

20. The gel polymer electrolyte according to claim 19, wherein: The gel polymer electrolyte also includes an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA).

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