EINZELION CONDUCTIVE GEL POLYMER ELECTROLYTE AND METHOD FOR ITS PREPARATION

Abstract

A single-ion conductive gel polymer electrolyte contains a fluorine-based compound in which 25 to 40% of the main chain is converted into carbon double bonds and 35 to 55 wt% of a lithium salt. The polymer ensures anion immobilization, thus restricting conductivity primarily to lithium ions. By including an optional additive such as PEGMEMA in specific weight ratios, the electrolyte achieves both high ionic conductivity and robust film formation. One method for producing this gel polymer electrolyte involves mixing the fluorine-based compound, the lithium salt, and a radical initiator, followed by in-situ cross-linking. The resulting freestanding film exhibits improved lithium metal anode stability and suppresses dendrite formation.Also revealed is a lithium secondary battery with this gel polymer electrolyte layer between the positive and negative electrodes, which exhibits improved cycle life and higher voltage stability.

Description

BACKGROUND TECHNICAL AREA

[0001] The present disclosure relates to a single-ion conductive gel polymer electrolyte containing a fluorine-based compound with an introduced carbon double bond. BACKGROUND

[0002] With the growth of the electric vehicle market, the demand for high-performance batteries that outperform conventional lithium-ion batteries is increasing, creating a need for negative and positive electrode materials with high energy density and long stability.

[0003] With the growth of the battery market, it is necessary to develop negative lithium metal electrodes with a high theoretical capacity (3860 mAh g). -1 ) as a replacement for graphite (372 mAh g -1 ), which is a conventional negative electrode material, and positive high-voltage electrode materials are needed to increase the energy density of the batteries.

[0004] Furthermore, dendrites that form in lithium metal batteries can cause short circuits and thus pose a fire hazard. To address this, a single-ion conductor with a high lithium transfer number can be used to suppress dendrite growth and achieve uniform lithium ion deposition, or a protective layer can be introduced for a positive lithium electrode to form a stable SEI layer.

[0005] On the other hand, a study is being conducted in which a polymer obtained by copolymerization of poly(ethylene glycol) methacrylate (PEGMA) and LiMTFSI is used as the electrolyte for a solid-state lithium metal battery. However, the polymer is unsuitable due to its low lithium-ion conductivity (2.3 × 10⁻⁶). -6 S cm -1at 25 °C) is only effective at low positive electrode capacity and current density (0.2 C-rate) and exhibits low high-voltage stability, which makes its use in batteries with NCM positive electrode difficult.

[0006] Therefore, there is a need for a polymer electrolyte that can provide higher ionic conductivity while simultaneously improving high-voltage stability. SUMMARY

[0007] One embodiment of the present disclosure aims to provide a gel polymer electrolyte with high single-ion conductivity and a method for its production.

[0008] Furthermore, in one embodiment of the present disclosure, the aim is to provide a gel polymer electrolyte and a method for its preparation which is capable of suppressing the dendrite growth that occurs when using a high-density electrolyte and a positive high-voltage electrode.

[0009] A gel polymer electrolyte according to an embodiment of the present disclosure is a single-ion conductive gel polymer electrolyte comprising a fluorine-based compound with a carbon double bond and a lithium salt.

[0010] In some aspects, the carbon double bond can be a carbon-carbon double bond. Other carbon double bonds may also be present, such as a carbon-nitrogen double bond.

[0011] In some aspects, a carbon double bond can be introduced into the fluorine-based compound; for example, the resulting fluorine-based compound can be treated to introduce a carbon double bond. For instance, a fluoropolymer or oligomer can be modified in one or more synthesis steps to contain or introduce a carbon double bond, such as a carbon-carbon double bond.

[0012] The lithium salt may be present in an amount of 35 wt.% to 55 wt.%, based on the total weight of the fluorine-based compound with an introduced carbon double bond and the lithium salt.

[0013] 30% to 35% of a main chain of the fluorine-based compound with a carbon double bond can be a double bond.

[0014] The lithium salt may comprise one or more selected from the group consisting of lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylic acid, and lithium 3-(2-methylprop-2-enoyloxy)propane-1-sulfonate.

[0015] The fluorine-based compound can be selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride co-chlorotrifluoroethylene (PVDF-CTFE), polyvinylidene fluoride co-trifluoroethylene (PVDF-TrFE), polyvinylidene fluoride co-trifluoroethylene co-chlorofluoroethylene, polyvinylidene fluoride co-hexafluoroethylene, and polyvinylidene fluoride co-hexafluoroethylene.

[0016] The gel polymer electrolyte may also contain an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA).

[0017] The additive can be present in an amount of 10 wt.% to 40 wt.%, based on the total weight of the fluorine-based compound with a carbon double bond and the lithium salt.

[0018] The gel polymer electrolyte may also contain an impregnated liquid electrolyte.

[0019] In one aspect, a process for producing a gel polymer electrolyte is provided, which may include a) preparing a mixture by mixing a fluorine-based compound with a carbon double bond, a lithium salt, and a radical initiator; b) applying the mixture to a base material; and c) crosslinking the mixture thereafter. In preferred aspects, the lithium salt is added in an amount of about 35 wt% to 55 wt%, based on the total weight of the fluorine-based compound, the lithium salt, and a crosslinking agent. In these aspects, the mixture can be crosslinked in situ after application to the base material.

[0020] In another aspect, a process for producing a gel polymer electrolyte of the present disclosure may include: producing a mixture by mixing a fluorine-based compound with a carbon double bond, a lithium salt, and a radical initiator; and applying the mixture to a base material, followed by an in situ cross-linking reaction.

[0021] The lithium salt can be added in an amount of 35 wt.% to 55 wt.%, based on the total weight of the fluorine-based compound, the lithium salt, and a crosslinking agent.

[0022] In certain aspects, the fluorine-based compound with a carbon double bond can be obtained by mixing a fluorine-based compound and a basic substance to form a fluorine-based compound with an introduced carbon double bond.

[0023] The basic substance may be one or more selected from the group consisting of ethylenediamine (EDA), isopropylethylenediamine (IEDA), 1,3-phenylenediamine (PDA), 1,5-naphthalenediamine (NDA), 2,4,4-trimethyl-1- or 6-hexanediamine (THDA), dicumyl peroxide (DCP), benzoyl peroxide, bisphenol A, and methylenediamine.

[0024] The fluorine-based compound may be one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP).

[0025] Mixing the fluorine-based compound and the basic substance to form a fluorine-based compound with an introduced carbon double bond may involve stirring the fluorine-based compound and the basic substance at room temperature for 60 to 100 hours.

[0026] The lithium salt may contain one or more selected from the group consisting of lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium 4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylic acid, and lithium 3-(2-methylprop-2-enoyloxy)propane-1-sulfonate.

[0027] When producing the mixture by mixing the fluorine-based compound with an introduced carbon double bond, the lithium salt, and the radical initiator, an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) can also be mixed.

[0028] The additive can be mixed in an amount of 10 wt.% to 40 wt.%, based on the total weight of the fluorine-based compound with an introduced carbon double bond and the lithium salt.

[0029] Another embodiment of the present disclosure may be a lithium secondary battery comprising: a positive electrode layer; a negative electrode layer; and an electrolyte layer arranged between the positive electrode layer and the negative electrode layer, wherein the electrolyte layer contains a gel polymer electrolyte layer, and the gel polymer electrolyte layer contains the gel polymer electrolyte described above.

[0030] The gel polymer electrolyte according to an embodiment of the present disclosure has the advantage of high single-ion conductivity.

[0031] The method for producing a gel polymer electrolyte according to a further embodiment of the present disclosure has the advantage of being able to produce a gel polymer electrolyte with high single-ion conductivity.

[0032] In some embodiments, a gel polymer electrolyte, which is a single-ion conductive gel polymer electrolyte, includes a fluorine-based compound with an introduced carbon double bond selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-cochlorotrifluoroethylene (PVDF-CTFE), polyvinylidene fluoride-co-trifluoroethylene (PVDF-TrFE), polyvinylidene fluoride-co-trifluoroethylene-co-chlorofluoroethylene, polyvinylidene fluoride-co-hexafluoroethylene, polyvinylidene fluoride-co-hexafluoroethylene, and a combination thereof; and a lithium salt selected from the group consisting of lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium 4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylic acid, and lithium 3-(2-methylprop-2-enoyloxy)propane-1-sulfonate, and a combination thereof.Approximately 25% to 40% of a main chain of the fluorine-based compound with an introduced carbon double bond is a double bond, and the lithium salt is present in an amount of approximately 35% to approximately 55% by weight, based on a total weight of the fluorine-based compound and the lithium salt.

[0033] The gel polymer electrolyte may further comprise an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA). The additive may be present in an amount of approximately 10 wt% to 40 wt%, based on the total weight of the fluorine-based compound and the lithium salt.

[0034] As explained, the procedure and the system expediently include the use of a controller or processor.

[0035] In another embodiment, vehicles are provided which include a device disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of a process for producing a gel polymer electrolyte according to an embodiment of the present disclosure. Fig. Figure 2 is a schematic cross-sectional view showing a positive electrode layer, an electrolyte layer and a negative electrode layer of a lithium secondary battery. Fig. Figure 3 shows an IR analysis result of EDA-PVdF, which was produced according to manufacturing example 1. Fig. Figure 4 shows an XPS analysis result of EDA-PVdF produced according to manufacturing example 1. Fig. Figure 5 shows the results of the lithium ion conductivity analysis of gel polymer electrolytes produced according to the comparison examples and examples. Fig. 6(a) is a photograph of a gel polymer electrolyte according to Example 2, and Fig. Figure 6(b) shows a result of a cross-linking test. Fig.Figure 7 is a photograph showing that a gel polymer electrolyte is not separated from a substrate according to comparative example 3. Fig. Figure 8 shows the results of the high voltage stability measurement at 4.55 V for a lithium metal battery of a comparison example and a lithium metal battery of an example. Fig. Figure 9 shows results of a cycle lifetime characteristic analysis for a lithium metal battery of a comparison example and a lithium metal battery of an example. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0036] The terms "first," "second," and "third" are used for descriptive purposes but are not limited to different parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another. Therefore, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without this constituting a deviation from the scope of this disclosure.

[0037] The technical terms used herein serve only to mention specific embodiments and are not intended to limit the present disclosure.

[0038] Singular forms used herein are intended to include plural forms unless expressions clearly indicate an opposite meaning. In this description, the term "inclusive" is intended to embody certain properties, ranges, integers, steps, operations, elements, and / or components, but not to exclude the presence or addition of other properties, ranges, integers, steps, operations, elements, and / or components.

[0039] It is understood that the term "vehicle" or "vehicle-related" or other similar terms as used herein include motor vehicles in general, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft and the like, and hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen vehicles and other vehicles powered by alternative fuels (e.g., fuels derived from resources other than petroleum). As used herein, a hybrid vehicle is a vehicle that has two or more sources of propulsion, for example, both gasoline-powered and electric vehicles.

[0040] The terminology used herein serves only to describe certain embodiments and is not intended to limit the disclosure. As used herein, the singular forms "a," "an," "one," and "the" are intended to include the plural forms unless the context clearly requires otherwise. These terms serve only to distinguish one component from another and do not limit the nature, sequence, or order of the constituents. As used herein, the term "and / or" includes all combinations of one or more of the elements listed. Furthermore, the terms "unit," "-er," "-or," and "module" used in the description refer to units for processing at least one function and operation, which may be implemented by hardware components or software components and combinations thereof.

[0041] Although the exemplary embodiment is described using a plurality of units to carry out the exemplary process, it is understood that the exemplary processes can also be carried out by one or more modules. Furthermore, it is understood that the term "controller / control unit" refers to a hardware device that includes memory and a processor and is specifically programmed to execute the processes described herein. The memory is configured to store the modules, and the processor is specifically configured to execute the modules to perform one or more processes described below.

[0042] Furthermore, the control logic of the present disclosure can be embodied as a non-transitory computer-readable medium on a computer-readable medium containing executable program instructions that are executed by a processor, control unit, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable medium can also be distributed in network-connected computer systems, such that the computer-readable medium is stored and executed in a distributed manner, for example, by a telematics server or a controller area network (CAN).

[0043] Unless explicitly stated or evident from the context, the term "approximately" is to be understood here as within a tolerance range customary in the field, for example, within 2 standard deviations from the mean. "Approximately" may be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise indicated by the context, all numerical values ​​provided herein are modified by the term "approximately".

[0044] When a part is described as "above" or "on" another part, it can be located directly above or on top of the other part, or there can be an intervening part. Conversely, when a part is described as "directly above" another part, there is no intervening part.

[0045] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meanings as they are generally understood by a person skilled in the art in the field of the present disclosure. Terms as defined in common dictionaries are to be interpreted as having meanings consistent with the relevant technical literature and the present disclosure, and are not to be interpreted as idealized or overly formal meanings unless expressly defined herein.

[0046] In the present description, the term ‘combination(s) thereof’ contained in the Markush formulation means one or more mixtures or combinations selected from the group consisting of the constituents described in the Markush formulation, and means that one or more selected from the group consisting of the constituents are included.

[0047] The following section describes in detail embodiments of the present disclosure so that a person skilled in the art can easily implement them. As the person skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the present disclosure. <gelpolymerelektrolyt>

[0048] A gel polymer electrolyte according to an embodiment of the present disclosure may contain a fluorine-based compound with a carbon double bond and a lithium salt.

[0049] In one embodiment of the present disclosure, the lithium salt can be present in an amount of 35 wt.% to 55 wt.%, particularly 40 wt.% or 45 wt.%, based on the total weight of the fluorine-based compound with an introduced carbon double bond and the lithium salt. Containing the lithium salt in the above range is preferred because it provides high conductivity for lithium ions and improves stability at high voltages, thus enabling excellent cycle life in lithium secondary batteries. If the lithium salt content falls below the above range, it is difficult to obtain the desired ionic conductivity. If the lithium salt content exceeds the above range, it is difficult to separate a gel polymer electrolyte from a substrate during the gel polymer electrolyte manufacturing process, leading to a reduction in quality.

[0050] The fluorine-based compound can be selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride co-chlorotrifluoroethylene (PVDF-CTFE), polyvinylidene fluoride co-trifluoroethylene (PVDF-TrFE), polyvinylidene fluoride co-trifluoroethylene co-chlorofluoroethylene, polyvinylidene fluoride co-hexafluoroethylene and polyvinylidene fluoride co-hexafluoroethylene.

[0051] 25% to 40%, and especially 30% to 35%, of a main chain of the fluorine-based compound containing a carbon-carbon double bond can be a double bond. If the carbon-carbon double bond (C=C), as analyzed by XPS, falls within the above range, anions are trapped in the polymer main chain, allowing only lithium ions to migrate and suppressing dendrite growth due to uneven lithium ion deposition caused by anion migration on the surface of the negative lithium metal electrode, which is preferred.

[0052] The lithium salt can contain lithium cations and anions. Using the lithium salt can suppress battery polarization and the growth of lithium dendrites.

[0053] The lithium salt may comprise one or more selected from the group consisting of lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylic acid, and lithium 3-(2-methylprop-2-enoyloxy)propane-1-sulfonate.

[0054] The gel polymer electrolyte can further contain an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA). This offers the advantages of increasing the cross-linking density and lowering the glass transition temperature of the polymer, thereby facilitating lithium transport and providing additional ionic conductivity.

[0055] In one embodiment of the present disclosure, the additive can be included in an amount of 10 wt.% to 40 wt.%, based on a total weight of the fluorine-based compound with a carbon double bond and the lithium salt.

[0056] In one embodiment of the present disclosure, the gel polymer electrolyte may further contain an impregnated liquid electrolyte.

[0057] The liquid electrolyte may comprise one or more selected from the group consisting of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl 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, succinonitrile, sulfolane, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, adiponitrile, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and dimethylacetamide.

[0058] The liquid electrolyte may further contain a lithium salt, and the lithium salt contained in the liquid electrolyte may include one or more selected from the group consisting of LiNO3, LiPF6, LiBF6, LiClO4, LiCF3SO3, LiBr, and LiI. <Verfahren zur Herstellung eines Gelpolymerelektrolyten>

[0059] Fig. Figure 1 is a schematic diagram of a process for producing a gel polymer electrolyte according to an embodiment of the present disclosure.

[0060] The following describes a method for producing a gel polymer electrolyte according to an embodiment of the present disclosure with reference to Fig. 1. specifically described.

[0061] With reference to Fig. 1. A method for producing a gel polymer electrolyte according to an embodiment of the present disclosure may comprise steps of producing a mixture by mixing a fluorine-based compound with a carbon double bond, a lithium salt, and a radical initiator, and applying the mixture to a base material, followed by an in-situ cross-linking reaction.

[0062] The fluorine-based compound with a carbon double bond can be formed by treating a fluorine-based compound with a base and can in particular be obtained by a step of mixing a fluorine-based compound and a basic substance to form a fluorine-based compound with an introduced carbon double bond.

[0063] In the step of mixing a fluorine-based compound and a basic substance to form a fluorine-based compound with a carbon double bond, ethylenediamine (EDA) was used, which has a relatively low pKa value.

[0064] In particular, EDA was used at a molar ratio of 45 to 55% of the repeating units of the fluorine-based compound. If the molar ratio range above is exceeded, purification becomes impossible due to cross-linking via a dehydrofluorination reaction between the chains of the fluorine-based compound. If the molar ratio falls below the range above, carbon double bonds are not effectively introduced.

[0065] The fluorine-based compound and the basic substance can be mixed and stirred at room temperature for 60 hours or longer, in particular for 60 to 100 hours, 60 to 80 hours or 65 to 75 hours.

[0066] The fluorine-based compound may be one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and may in particular be polyvinylidene fluoride (PVDF).

[0067] The basic substance may be one or more selected from the group consisting of ethylenediamine (EDA), isopropylethylenediamine (IEDA), 1,3-phenylenediamine (PDA), 1,5-naphthalenediamine (NDA), 2,4,4-trimethyl-1- or 6-hexanediamine (THDA), dicumyl peroxide (DCP), benzoyl peroxide, bisphenol A, and methylenediamine, and may in particular be ethylenediamine (EDA).

[0068] The lithium salt may contain one or more selected from the group consisting of lithium 1-(3-(methacryloyloxy) propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI) and lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI).

[0069] The initiator may contain one or more selected from the group consisting of azobis(isobutyronitrile) (AIBN), benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, t-butyl peroxy-2-ethylhexanoate, cumyl hydroperoxide, hydrogen peroxide, 2,2-azobis(2-cyanobutane) [2,2-azobis(methylbutyronitrile)], and azobisdimethylvaleronitrile (AMVN), and may in particular be azobis(isobutyronitrile) (AIBN).

[0070] It should be noted that in the step of preparing the mixture by mixing the fluorine-based compound with an introduced carbon double bond, the lithium salt and the radical initiator, an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) may also be mixed.

[0071] The additive can be mixed in amounts ranging from 10 wt% to 40 wt%, based on the total weight of the fluorine-based compound with an introduced carbon double bond and the lithium salt. If the additive is mixed within this range, a high-quality polymer gel electrolyte can be produced. If the additive exceeds this range, it is difficult to form a self-supporting polymer gel electrolyte, and if the additive falls below this range, the quality of the produced polymer gel electrolyte deteriorates. <Lithium-Sekundärbatterie>

[0072] Fig. Figure 2 is a cross-sectional view that schematically shows a positive electrode layer, an electrolyte layer and a negative electrode layer of a lithium secondary battery.

[0073] With reference to Fig. 2(a) A lithium secondary battery according to one embodiment of the present disclosure may comprise a positive electrode layer 20, a negative electrode layer 10, and an electrolyte layer 30 arranged between the positive electrode layer and the negative electrode layer. The electrolyte layer 30 may comprise the gel polymer electrolyte layer 31 mentioned above, and the gel polymer electrolyte layer 31 may comprise a gel polymer electrolyte. Since the gel polymer electrolyte has been described in detail above, it is omitted here.

[0074] It should be noted that the gel polymer electrolyte can be arranged as a thin film between the negative electrode layer and the electrolyte layer, and in particular, can be a thin film with a thickness in the range of 30 µm to 40 µm. If the thickness of the gel polymer electrolyte exceeds the aforementioned range, the initial discharge capacity decreases, and if the thickness falls below the aforementioned range, damage to the intermediate layer occurs during the separation process from the substrate.

[0075] It should be noted that, according to one embodiment of the present disclosure, the positive electrode layer of the lithium secondary battery may contain a positive electrode active material for which a charging voltage within a range of 4.3 V or less is used.

[0076] The following are preferred examples of the present revelation and examples for comparison. However, the following examples are only preferred examples of the present revelation, and the present revelation is not limited to the following examples. (Production example 1) Production of a fluorine-based compound with an introduced carbon double bond

[0077] 3 g of polyvinylidene fluoride (PVDF) and 2.8 g of ethylenediamine (EDA) were dispersed by ultrasonic treatment in 30 ml of dimethylformamide (DMF) as solvent and stirred at room temperature (about 25 °C) for about 72 hours, then precipitated in ethanol and filtered to produce EDA-PVdF.

[0078] The synthesized EDA-PVdF, lithium-1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI) as the lithium salt, and azobis(isobutyronitrile) (AIBN) as the initiator were added. They were then dispersed by ultrasonic treatment for approximately 3 hours and poured onto a glass plate. The resulting product was subjected to in-situ cross-linking under vacuum conditions 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. (Examples and comparative examples) Production of a gel polymer electrolyte

[0079] Lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI) as the lithium salt and azobis(isobutyronitrile) (AIBN) as the initiator were added to the EDA-PVdF prepared according to the manufacturing example. They were then dispersed by ultrasonic treatment for approximately 3 hours and poured onto a glass plate. The resulting product was subjected to in-situ cross-linking under vacuum conditions at approximately 70 °C to obtain a gel polymer electrolyte. The gel polymer electrolyte was washed with ethanol to remove unreacted lithium salt.

[0080] The weight fractions of EDA-PVdF and lithium salt LiMTFSI according to the examples and comparison examples are listed in the following Table 1. (Evaluation example 1: IR analysis)

[0081] An IR analysis was performed on EDA-PVdF, which was manufactured according to manufacturing example 1, and the analysis results are presented in Fig. 3 shown.

[0082] With reference to Fig. 3 confirms the C=C bonding signal at a wavelength of 1650 cm -1 , that the double bond was introduced into the EDA-PVdF produced according to the manufacturing example. (Evaluation example 2: XPS analysis)

[0083] An XPS analysis was performed on EDA-PVdF produced according to manufacturing example 1, and the analysis results are presented in Fig. 4 shown.

[0084] With reference to Fig. 4 confirms the area calculation of the CC and C=C signals in the XPS analysis that 32% of the main chain of EDA-PVdF is a double bond. (Evaluation example 3: Analysis of ionic conductivity)

[0085] The gel polymer electrolytes produced according to the examples and comparative examples were each impregnated for approximately 24 hours in a liquid electrolyte, which served as the electrolyte layer for assembling a button cell with a spacer / electrolyte layer / spacer structure. The resistance of the button cell was measured over a temperature range of 10 °C to 80 °C and converted into lithium-ion conductivity (a Zahner Electrik IM6 device was used, with a frequency range of 100 Hz to 1 MHz at an applied voltage of 10 mV).

[0086] The procedure for analyzing lithium ion conductivity is as follows. a) The amount of liquid electrolyte impregnation is based on 100 parts by weight of gel polymer electrolyte. b) Measured at 25 °C. The liquid electrolyte used is a mixed solvent of ethylene carbonate and dimethyl carbonate. c) Electrochemical window measured by linear sweep voltammetry

[0087] The results of the lithium ion conductivity analysis are in Fig. 5 and Table 1 shown below. (Table 1) sample LiMTFSI (wt%) EDA-PVdF (wt%) Ionic conductivity at 30 °C (S cm-1) Comparative example 1 SIPE 0.2 80 2,88 × 10-5 Comparative example 2 SIPE 0.3 30 70 4,90 × 10 -5 Design 1 SIPE 0.4 40 60 1,29 × 10 -4 Design 2 SIPE 0.5 50 50 2,45 × 10 -4 Comparative example 3 SIPE 0.6 60 40 -

[0088] With reference to Fig. 5 and Table 1 confirm that the lithium ion conductivity tends to increase with increasing content of lithium salt LiMTFSI.

[0089] Fig. 6(a) shows a photograph of a gel polymer electrolyte according to Example 2, and Fig. Figure 6(b) shows a result of a cross-linking test.

[0090] With reference to Fig. 6(a) It can be confirmed that the gel polymer electrolyte produced according to Example 2 forms a free-standing form after separation from the substrate. With reference to Fig. 6(b) It can be confirmed that the gel polymer electrolyte produced according to Example 2 retains its shape even after impregnation in the DMF solvent without dissolving. This is attributed to the introduction of the cross-linking structure during the manufacturing process.

[0091] On the other hand, in comparative example 3, where the lithium salt LiMTFSI content was 60 wt%, the membrane exhibited a low degree of cross-linking and low elasticity due to the insufficient amount of PVDF. Consequently, the membrane was damaged during separation from the substrate, making it impossible to prepare the gel polymer electrolyte and measure the lithium ion conductivity.

[0092] Fig. Figure 7 is a photograph showing that a gel polymer electrolyte is not separated from a substrate according to comparative example 3. (Experimental example)

[0093] The electrolyte layer structure was implemented using a commercially available membrane layer. A lithium metal battery with a Li / electrolyte layer / NCM(NCM900505) structure of a comparative example was fabricated, and a lithium metal battery with a Li / gel polymer electrolyte layer / electrolyte layer / NCM(NCM900505) structure of an example was fabricated.

[0094] In this case, the gel polymer electrolyte layer in the lithium metal battery of the example was composed of the gel polymer electrolyte according to Example 2.

[0095] Fig. Figure 8 shows the results of the high voltage stability measurement at 4.55 V for a lithium metal battery of a comparison example and a lithium metal battery of an example.

[0096] With reference to Fig. 8 can be confirmed that the high voltage stability in the lithium metal battery of the example, which includes the layer composed of the gel polymer electrolyte according to Example 2 of the present disclosure, is superior.

[0097] Fig. Figure 9 shows the results of the analysis of the cycle life characteristics for a lithium metal battery of a comparison example and a lithium metal battery of an example.

[0098] It can be confirmed that the lithium metal battery of the example according to the present disclosure has a stable cycle life of 300 cycles or more at a C-rate of 1 / 3 at the positive electrode made of NCM900505 at 4.0 mAh·cm -2 with a drive voltage of 3.0 to 4.3 V, which demonstrates superior performance compared to the lithium metal battery of the comparison example.

[0099] The present disclosure has been described in connection with embodiments currently considered practical; however, it is understood that the disclosure is not limited to the disclosed embodiments. On the contrary, it is intended to include various modifications and equivalent arrangements contained within the scope and meaning of the appended claims.

[0100] Therefore, it should be noted that the practical scope of the present disclosure is defined by the attached claims and their equivalents.< / gelpolymerelektrolyt>

Claims

Gel polymer electrolyte, which is a single-ion conductive gel polymer electrolyte, comprising: a fluorine-based compound with a carbon double bond; and a lithium salt. Gel polymer electrolyte according to claim 1, wherein the carbon double bond is a carbon-carbon double bond. Gel polymer electrolyte according to claim 1, wherein the lithium salt is contained in an amount of about 35 wt.% to 55 wt.%, based on a total weight of the fluorine-based compound with carbon double bond and the lithium salt. Gel polymer electrolyte according to claim 1, wherein about 30% to 35% of a main chain of the fluorine-based compound with carbon double bond is a double bond. Gel polymer electrolyte according to claim 1, wherein the lithium salt is one or more selected from the group consisting of lithium-1-(3-(methacryloyloxy) propylsulfonyl) -1-(trifluoromethanesulfonyl) imide (LiMTFSI), lithium-(4-styrenesulfonyl) (trifluoromethanesulfonyl) imide (LiSTFSI), lithium methacrylic acid, and lithium-3-(2-methylprop-2-enoyloxy) propane-1-sulfonate. Gel polymer electrolyte according to claim 1, wherein: the fluorine-based compound is one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride co-chlorotrifluoroethylene (PVDF-CTFE), polyvinylidene fluoride co-trifluoroethylene (PVDF-TrFE), polyvinylidene fluoride co-trifluoroethylene co-chlorofluoroethylene, polyvinylidene fluoride co-hexafluoroethylene, and polyvinylidene fluoride co-hexafluoroethylene. Gel polymer electrolyte according to claim 1, wherein: the gel polymer electrolyte further comprises an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA). Gel polymer electrolyte according to claim 7, wherein the additive is contained in an amount of about 10 wt.% to 40 wt.%, based on a total weight of the fluorine-based compound with carbon double bond and the lithium salt. Gel polymer electrolyte according to claim 1, wherein the gel polymer electrolyte further comprises an impregnated liquid electrolyte. A process for producing a gel polymer electrolyte, comprising: providing a mixture by mixing a fluorine-based compound with a carbon double bond, a lithium salt, and a radical initiator; and applying the mixture to a base material, and subsequently crosslinking the mixture, wherein the lithium salt is added in an amount of about 35 wt.% to 55 wt.%, based on a total weight of the fluorine-based compound, the lithium salt, and a crosslinking agent. The method of claim 10, wherein the fluorine-based compound with a carbon double bond is obtained by mixing a fluorine-based compound and a basic substance to form a fluorine-based compound with a carbon double bond. The method of claim 11, wherein the basic substance is one or more selected from the group consisting of ethylenediamine (EDA), isopropylethylenediamine (IEDA), 1,3-phenylenediamine (PDA), 1,5-naphthalenediamine (NDA), 2,4,4-trimethyl-1- or 6-hexanediamine (THDA), dicumyl peroxide (DCP), benzoyl peroxide, bisphenol A, and methylenediamine. The method of claim 11, wherein the fluorine-based compound is one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polyvinylidene fluoride hexafluoropropylene (PVDF-HFP). The method of claim 11, wherein the mixing of the fluorine-based compound and the basic substance to form a fluorine-based compound with an introduced carbon double bond comprises: stirring the fluorine-based compound and the basic substance at room temperature for about 60 hours or longer. The method of claim 10, wherein the lithium salt is one or more selected from the group consisting of lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium 4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylic acid, and lithium 3-(2-methylprop-2-enoyloxy)propane-1-sulfonate. The method of claim 10, wherein: when providing the mixture by mixing the fluorine-based compound with an introduced carbon double bond, the lithium salt, and the radical initiator, an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) is further mixed. The method of claim 16, wherein the additive is mixed in an amount of about 10 wt.% to 40 wt.%, based on a total weight of the fluorine-based compound with a carbon double bond and the lithium salt. Lithium secondary battery comprising: a positive electrode layer; a negative electrode layer; and an electrolyte layer arranged between the positive electrode layer and the negative electrode layer, wherein the electrolyte layer comprises a gel polymer electrolyte layer, and wherein the gel polymer electrolyte layer comprises the gel polymer electrolyte of claim 1. Gel polymer electrolyte, which is a single-ion conductive gel polymer electrolyte, comprising: a fluorine-based compound with an introduced carbon double bond selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-co-chlorotrifluoroethylene (PVDF-CTFE), polyvinylidene fluoride-co-trifluoroethylene (PVDF-TrFE), polyvinylidene fluoride-co-trifluoroethylene-co-chlorofluoroethylene, polyvinylidene fluoride-co-hexafluoroethylene, polyvinylidene fluoride-co-hexafluoroethylene, and a combination thereof;and a lithium salt selected from the group consisting of lithium 1-(3-(methacryloyloxy)propylsulfonyl)-1-(trifluoromethanesulfonyl)imide (LiMTFSI), lithium 4-styrenesulfonyl)(trifluoromethanesulfonyl)imide (LiSTFSI), lithium methacrylic acid, and lithium 3-(2-methylprop-2-enoyloxy)propane-1-sulfonate, and a combination thereof, wherein about 25% to 40% of a main chain of the fluorine-based compound with a carbon double bond is a double bond, and wherein the lithium salt is present in an amount of about 35% to about 55% by weight, based on a total weight of the fluorine-based compound and the lithium salt. Gel polymer electrolyte according to claim 19, wherein the gel polymer electrolyte further comprises an additive composed of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA).

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