Composition for gel polymer electrolyte, gel polymer electrolyte, and lithium secondary battery comprising gel polymer electrolyte

Abstract

The present disclosure provides: a composition for a gel polymer electrolyte comprising an electrolyte salt, an organic solvent, a polymerizable monomer, a polymerization initiator, and a polymerization inhibitor; a gel polymer electrolyte prepared by using the composition for a gel polymer electrolyte; and a lithium secondary battery comprising the gel polymer electrolyte.

Description

Composition for gel polymer electrolyte, gel polymer electrolyte and lithium secondary battery comprising gel polymer electrolyte

[0001] The present disclosure relates to a composition for a gel polymer electrolyte, a gel polymer electrolyte, and a lithium secondary battery including the gel polymer electrolyte.

[0002] With growing concern about environmental issues, exhaust fumes from vehicles running on fossil fuels like gasoline and diesel have been identified as a major cause of air pollution. Research is actively underway on alternatives, such as electric vehicles (EVs) and hybrid electric vehicles (HEVs). Lithium secondary batteries, with their high discharge voltage and stable output, are primarily used as power sources for these vehicles.

[0003] Depending on the type of electrolyte used, lithium secondary batteries can be categorized into lithium-ion batteries, which use liquid electrolytes, and lithium polymer batteries, which use polymer electrolytes. Lithium-ion batteries, due to their liquid electrolytes, pose a risk of leakage and explosion, complicating battery design. Conversely, lithium polymer batteries, which utilize solid polymer or gel polymer electrolytes, offer improved stability, leading to active development of lithium polymer batteries.

[0004] A lithium secondary battery including a gel polymer electrolyte can be manufactured by dissociating a polymerizable monomer and a polymerization initiator in a liquid electrolyte to prepare a liquid gel polymer electrolyte composition, pouring the gel polymer electrolyte composition into a battery case, and then impregnating an electrode assembly including a positive electrode, a negative electrode, and a separator under appropriate temperature and time conditions to form a gel polymer electrolyte.

[0005] In the process of impregnating the above gel polymer electrolyte composition into an electrode assembly, the gel polymer electrolyte composition may prematurely harden due to the reaction between the monomer and the polymerization initiator, thereby forming a gel polymer electrolyte having an uneven degree of crosslinking and surface, which may result in deterioration of secondary battery cell performance due to liquid leakage, etc. Accordingly, a technology for preventing premature hardening of the gel polymer electrolyte composition is required.

[0006] The present disclosure provides a composition for a gel polymer electrolyte including a polymerization inhibitor, a gel polymer electrolyte, and a lithium secondary battery including the gel polymer electrolyte.

[0007] A composition for a gel polymer electrolyte according to the present disclosure may include an electrolyte salt, an organic solvent, a polymerizable monomer, a polymerization initiator, and a polymerization inhibitor.

[0008] The above polymerization inhibitor may include at least one selected from the group consisting of aromatic compounds containing a hydroxyl group or an alkoxy group, quinone-based compounds, phenocyazine-based compounds, and nitrosobenzene-based compounds.

[0009] The aromatic compound containing the above hydroxyl group or alkoxy group may contain two or more hydroxyl groups or two or more alkoxy groups.

[0010] The aromatic compound containing the above hydroxyl group or alkoxy group may further contain a nitro group or an alkyl group.

[0011] The aromatic compound containing the above hydroxyl group or alkoxy group may contain a single ring or a fused ring in which two or more single rings are fused.

[0012] The above polymerization inhibitors are 4-methoxyphenol (MEHQ), 1,2-benzoquinone, 4-tert-butylcatechol (TBC), nitrobenzene, picric acid, t-butylhydroquinone (TBHQ), hydroquinone, p-methoxyphenol, phenothiazine, tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 2-tert-butyl-1,4-benzoquinone, It may include at least one selected from the group consisting of 6-tert-butyl-2,4-xylenol, 2,6-di-tert-butylphenol, 6-tert-butyl-2,4-xylenol, and 2,6-di-tert-butylphenol.

[0013] The above polymerization inhibitor may be included in an amount of 150 ppm or less based on the total weight of the composition for the gel polymer electrolyte.

[0014] The above polymerizable monomer may have a polymerizable functional group including at least one group selected from the group consisting of a vinyl group, an epoxy group, an allyl group, an acrylic group, a (meth)acrylic group, an ether group, and a fluorine (F) group and a phosphate group.

[0015] The above polymerizable monomer may include three or more of the above polymerizable functional groups.

[0016] The above polymerizable monomer may include a phosphate group, an acrylate group, and an ether group.

[0017] The polymerizable monomer comprising the phosphate group may include an electron donating group (EGD).

[0018] The gel polymer electrolyte according to the present disclosure may include a polymerizable polymer, an electrolyte salt, an organic solvent, a polymerization initiator, and a polymerization inhibitor.

[0019] The above polymerization inhibitor may include at least one selected from the group consisting of aromatic compounds containing a hydroxyl group or an alkoxy group, quinone-based compounds, phenocyazine-based compounds, and nitrosobenzene-based compounds.

[0020] The above polymerization inhibitors are 4-methoxyphenol (MEHQ), 1,2-benzoquinone, 4-tert-butylcatechol (TBC), nitrosobenzene, picric acid, t-butylhydroquinone (TBHQ), hydroquinone, p-methoxyphenol, phenothiazine, tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 2-tert-butyl-1,4-benzoquinone, It may include at least one selected from the group consisting of 6-tert-butyl-2,4-xylenol, 2,6-di-tert-butylphenol, 6-tert-butyl-2,4-xylenol, and 2,6-di-tert-butylphenol.

[0021] A lithium secondary battery according to the present disclosure may include the gel polymer electrolyte and a positive electrode and a negative electrode impregnated with the gel polymer electrolyte.

[0022] The composition for a gel polymer electrolyte according to the present disclosure can prevent premature polymerization between polymerizable monomers at room temperature by including a polymerization inhibitor.

[0023] A gel polymer electrolyte manufactured by the above gel polymer electrolyte composition can have a uniform degree of crosslinking.

[0024] The storage stability of the composition for the gel polymer electrolyte at room temperature can be improved, and the processability of the impregnation process of the composition for the gel polymer electrolyte can be improved.

[0025] The impregnation property of the above gel polymer electrolyte is improved, so that the gel polymer electrolyte can be uniformly impregnated into the electrode assembly.

[0026] By including a gel polymer electrolyte of one embodiment of the present disclosure, the performance of a secondary battery cell can be improved.

[0027] Figure 1 is an image showing whether a polymerization inhibitor is dissolved in a gel polymer electrolyte composition of an example and a comparative example of the present disclosure.

[0028] Figure 2 is a graph showing whether a polymerization inhibitor is detected in a gel polymer electrolyte composition of an example and a comparative example of the present disclosure.

[0029] FIG. 3 is a graph showing the amount of polymerization inhibitor detected in a gel polymer electrolyte composition of an embodiment of the present disclosure.

[0030] Figure 4 is an image showing whether the gel polymer electrolyte composition of the present disclosure and comparative examples is polymerized when stored at room temperature.

[0031] Figure 5 is an image showing whether the gel polymer electrolyte composition of the present disclosure and comparative examples is polymerized at high temperature.

[0032] A gel polymer electrolyte composition according to the present disclosure may include an electrolyte salt, an organic solvent, a polymerizable monomer, a polymerization initiator, and a polymerization inhibitor. In addition, the gel polymer electrolyte composition may further include an additive.

[0033] electrolyte salt

[0034] The above electrolyte salt is used as a medium for transferring ions within a secondary battery, and may not be particularly limited as long as it is a commonly used electrolyte salt for secondary batteries.

[0035] In exemplary embodiments, the electrolyte salt may be a lithium salt, for example, Li as the cation. + , and contains F as an anion. - , Cl - , Br - , BF4 - , I - , NO3 - , N(CN)2 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N -, CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include at least one selected from the group consisting of LiPF6, LiBETI (lithium bisperfluoroethanesulfonimide, LiN(SO2C2F5)2), LiFSI (lithium fluorosulfonyl imide, LiN(SO2F)2), LiTFSI (lithium (bis)trifluoromethanesulfonimide, LiN(SO2CF3)2), and LiDFOB (lithium difluoro(oxalato) borate). In one embodiment, the electrolyte salt may include at least one selected from the group consisting of LiPF6, LiBETI (lithium bisperfluoroethanesulfonimide, LiN(SO2C2F5)2), LiFSI (lithium fluorosulfonyl imide, LiN(SO2F)2), LiTFSI (lithium (bis)trifluoromethanesulfonimide, LiN(SO2CF3)2), and LiDFOB (lithium difluoro(oxalato) borate).

[0036] In one embodiment, the electrolyte salt may be included in the gel polymer electrolyte composition at a concentration of about 0.5 to about 2 M, specifically, at a concentration of about 0.8 to about 1.5 M. As the electrolyte salt is included in the gel polymer electrolyte composition at a concentration within the above range, an optimal corrosion-preventing film is formed on the electrode surface, resistance due to depletion of lithium ions during high-rate charge / discharge is reduced, and due to an increase in lithium ions in the gel polymer electrolyte composition, high lithium ion transfer characteristics, i.e., ion transfer number, are secured and lithium ion diffusion resistance is reduced, so that cycle capacity characteristics, ion conductivity, and rate characteristics can be improved.

[0037] organic solvent

[0038] The above organic solvent is a non-aqueous organic solvent, and may not be particularly limited as long as it minimizes decomposition due to oxidation reactions, etc. during the charging and discharging process of a secondary battery and can exhibit the desired characteristics together with an additive.

[0039] In exemplary embodiments, the organic solvent may be, for example, a carbonate-based organic solvent, an ether-based organic solvent, or an ester-based organic solvent, each of which may be used alone or in combination of two or more thereof.

[0040] In exemplary embodiments, the carbonate-based organic solvent may include at least one of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent.

[0041] In one embodiment, the cyclic carbonate-based organic solvent may include at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate (FEC). The cyclic carbonate-based organic solvent may include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively low melting point compared to ethylene carbonate.

[0042] In one embodiment, the linear carbonate-based organic solvent is a solvent having low viscosity and low dielectric constant, and may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate.

[0043] In exemplary embodiments, the ether organic solvent may include one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether, or a mixture of two or more thereof.

[0044] In exemplary embodiments, the ester organic solvent may include at least one selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents.

[0045] In one embodiment, the linear ester organic solvent may include one or a mixture of two or more selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0046] In one embodiment, the cyclic ester organic solvent may include any one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more thereof.

[0047] polymerizable monomer

[0048] The above polymerizable monomer has a polymerizable functional group including at least one group selected from the group consisting of a vinyl group, an epoxy group, an allyl group, an acrylic group, a (meth)acrylic group, an ether group, and a fluorine (F) group capable of undergoing a polymerization reaction, and a phosphate group, and can be changed into a gel phase by polymerization or crosslinking. At this time, the acrylic group may include an acrylate group, and the (meth)acrylic group may include an acrylic group and a methacrylic group.

[0049] The above polymerizable monomer may not be particularly limited as long as it is a monomer used as a conventional gel polymer electrolyte.

[0050] In exemplary embodiments, the polymerizable monomer may include three or more of the polymerizable functional groups. Specifically, the polymerizable monomer may include a phosphate group, an acrylate group, and an ether group. More specifically, the polymerizable monomer may be, for example, tetraethylene glycol diacrylate, polyethylene glycol diacrylate (molecular weight 50 to 20,000), 1,4-butanediol diacrylate, 1,6-hexandiol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol. pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, poly(ethylene glycol) diglycidyl ether, 1,5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether,It may include at least one selected from the group consisting of vinylcyclohexene dioxide, 1,2,7,8-diepoxyoctane, 4-vinylcyclohexene dioxide, butyl glycidyl ether, diglycidyl 1,2-cyclohexanedicarboxylate, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and glycidyl methacrylate.

[0051] Meanwhile, the polymerizable monomer containing a phosphate group having flame retardancy can make the gel polymer electrolyte produced by the composition for the gel polymer electrolyte have flame retardancy.

[0052] In one embodiment, the polymerizable monomer comprising the phosphate group may comprise an electron donating group (EGD).

[0053] In one embodiment, the polymerizable monomer may be included in an amount of about 2 to about 30 wt%, specifically about 2 to about 20 wt%, and more specifically about 4 to about 10 wt%, based on the total weight of the composition for the gel polymer electrolyte. When the polymerizable monomer is included in the above range based on the total weight of the composition for the gel polymer electrolyte, the polymerizable monomers may form a sufficient crosslinking network and improve the ionic conductivity of the electrolyte, thereby improving the capacity development and capacity retention rate of the secondary battery.

[0054] polymerization initiator

[0055] The polymerization initiator may be a thermal or photopolymerization initiator. The polymerization initiator is decomposed by heat or light to form radicals, and these radicals can initiate a polymerization reaction between polymerizable monomers.

[0056] In exemplary embodiments, organic peroxides or hydroperoxides such as benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, t-butyl peroxy-2-ethyl-hexanoate, t-butyl peroxypivalate, cumyl hydroperoxide and hydrogen peroxide, and 2,2'-azobis(2-cyanobutane), 2,2'-azobis(methylbutyronitrile), 2,2'-azobis(isobutyronitrile) (AIBN) and It may include one or more azo compounds selected from the group consisting of 2,2'-azobisdimethyl-valeronitrile (AMVN).

[0057] In one embodiment, the polymerization initiator can be decomposed by heat at a temperature of about 50 to about 90° C. to form radicals and initiate a polymerization reaction between polymerizable monomers.

[0058] In one embodiment, the polymerization initiator may be included in an amount of about 0.025 to about 0.3 wt% based on the total weight of the composition for the gel polymer electrolyte. If the polymerization initiator is included in an amount greater than about 0.3 wt% based on the total weight of the composition for the gel polymer electrolyte, a polymerization reaction between polymerizable monomers may be initiated before the composition for the gel polymer electrolyte reaches a curing temperature, thereby causing the composition for the gel polymer electrolyte to be cured prematurely. If the polymerization initiator is included in an amount less than about 0.025 wt% based on the total weight of the composition for the gel polymer electrolyte, a polymerization reaction between polymerizable monomers may not be sufficiently initiated, thereby preventing the polymerizable monomers from forming a sufficient crosslinking network.

[0059] polymerization inhibitor

[0060] The polymerization inhibitor can prevent premature polymerization between the polymerizable monomers. Specifically, the polymerization inhibitor can prevent premature polymerization between the polymerizable monomers by quickly reacting with radicals formed from the polymerization initiator and stabilizing the radicals.

[0061] In exemplary embodiments, the polymerization inhibitor may include at least one selected from the group consisting of an aromatic compound containing a hydroxyl group or an alkoxy group, a quinone-based compound, a phenocyanidin-based compound, and a nitrosobenzene-based compound.

[0062] In one embodiment, the aromatic compound comprising a hydroxyl group or an alkoxy group may comprise two or more hydroxyl groups or may comprise two or more alkoxy groups.

[0063] In one embodiment, the aromatic compound comprising a hydroxyl group or an alkoxy group may further comprise a nitro group or an alkyl group.

[0064] In one embodiment, the aromatic compound comprising the hydroxyl group or the alkoxy group may comprise a single ring or a fused ring in which two or more single rings are fused.

[0065] Specifically, the aromatic compound containing a hydroxyl group or an alkoxy group may include at least one selected from the group consisting of, for example, 4-methoxyphenol (MEHQ), 4-tert-butylcatechol (TBC), picric acid, t-butylhydroquinone (TBHQ), hydroquinone, p-methoxyphenol, tert-butylhydroquinone, 6-tert-butyl-2,4-xylenol, 2,6-di-tert-butylphenol, and dibutylhydroxytoluene (BHT).

[0066] Specifically, the quinone compound may include, for example, 1,2-benzoquinone or 2-tert-butyl-1,4-benzoquinone, the phenothiazine compound may include, for example, phenothiazine, and the nitrosobenzene compound may include, for example, nitrosobenzene.

[0067] In one embodiment, the polymerization inhibitor may be included in an amount of about 150 ppm or less, specifically about 5 to about 100 ppm, more specifically about 10 to about 100 ppm, about 15 to about 80 ppm, about 20 to 80 ppm, or about 20 to about 50 ppm, based on the total weight of the gel polymer electrolyte composition. If the polymerization inhibitor is included in the above range, premature polymerization between the polymerizable monomers can be suppressed, while the solubility of the polymerization inhibitor and the curability of the gel polymer electrolyte composition are excellent, so that a gel polymer electrolyte having a uniform crosslinking degree and surface and a gel in which the liquid electrolyte does not separate from the gel can be formed.

[0068] additives

[0069] The above additive may be included in the gel polymer electrolyte composition to prevent the gel polymer electrolyte composition from decomposing in a high-power environment during the manufacture of the gel polymer electrolyte, causing cathode collapse, and to form a more stable ion-conductive film on the electrode surface.

[0070] In exemplary embodiments, the additive may include at least one selected from the group consisting of sulfone compounds, sulfite compounds, sulfone compounds, sulfate compounds, halogen-substituted carbonate compounds, nitrile compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, lithium salt compounds, and fluorine compounds.

[0071] As described above, the polymerizable monomers can be prematurely polymerized by the polymerization initiator. In particular, when the polymerizable monomer includes a monomer having a phosphate group having flame retardancy, the monomer including the phosphate group includes an electron-donating group, thereby further accelerating premature polymerization between the polymerizable monomers, and such premature polymerization can occur even at room temperature.

[0072] However, in exemplary embodiments, since the gel polymer electrolyte composition includes the polymerization inhibitor, premature polymerization between the polymerizable monomers at room temperature can be prevented. Accordingly, the gel polymer electrolyte manufactured using the gel polymer electrolyte composition can have flame retardancy and a uniform degree of crosslinking. As a result, the storage stability of the gel polymer electrolyte composition at room temperature can be improved, and the processability of the impregnation process of the gel polymer electrolyte composition can be improved. Consequently, the impregnation property of the gel polymer electrolyte is improved, so that the gel polymer electrolyte is uniformly impregnated into the electrode assembly, and thus the performance of the secondary battery cell can be improved.

[0073] Hereinafter, the process for manufacturing a gel polymer electrolyte using the aforementioned gel polymer electrolyte composition will be described. While describing this process, the effects of the present disclosure achieved by the aforementioned gel polymer electrolyte composition including the polymerization inhibitor will be described in more detail.

[0074] First, the electrolyte salt, the polymerizable monomer, the polymerization inhibitor, and the additive can be dissolved in the organic solvent.

[0075] In one embodiment, the electrolyte salt, the polymerizable monomer, the polymerization inhibitor, and the additive can be dissolved in the organic solvent by stirring at room temperature for about 1 hour or more.

[0076] Thereafter, the composition for the gel polymer electrolyte can be prepared by dissolving the polymerization initiator in the organic solvent at room temperature.

[0077] Thereafter, the gel polymer electrolyte composition may be stored at room temperature for a certain period of time before being injected into a battery case. Since the gel polymer electrolyte composition includes the polymerization inhibitor, premature polymerization between the polymerizable monomers at room temperature is prevented, and thus the composition may be stored in a liquid state without changing into a gel state. In one embodiment, the gel polymer electrolyte composition may be stored at a temperature of about 30°C or lower for about 24 hours.

[0078] Thereafter, the gel polymer electrolyte composition may be injected into a battery case and then impregnated into an electrode assembly including a positive electrode and a negative electrode at room temperature for a certain period of time to produce a gel polymer electrolyte. Since the gel polymer electrolyte composition includes the polymerization inhibitor, premature polymerization between the polymerizable monomers at room temperature is prevented, so that the gel polymer electrolyte can be uniformly impregnated into the electrode assembly. In one embodiment, the impregnation process may be performed at a temperature of about 30°C or less for about 10 hours or more.

[0079] Thereafter, the gel polymer electrolyte composition can be formed by raising the temperature and curing the composition. Since the gel polymer electrolyte composition is stored at room temperature and premature polymerization is prevented by the polymerization inhibitor while being impregnated into the electrode assembly, when the gel polymer electrolyte composition is raised and cured, the gel polymer electrolyte having a uniform degree of crosslinking can be formed.

[0080] In exemplary embodiments, the impregnation process may further include a degassing process. The degassing process may remove gas present within the battery case before the gel polymer electrolyte composition is cured.

[0081] In this way, the gel polymer electrolyte can be manufactured.

[0082] If the gel polymer electrolyte composition does not include the polymerization inhibitor, when the gel polymer electrolyte composition is stored at room temperature, the polymerizable monomers may prematurely polymerize, resulting in at least a portion of the gel polymer electrolyte composition being cured. Subsequently, as the cured gel polymer electrolyte composition is injected into the battery case, the gel polymer electrolyte composition may be completely cured before the process temperature and time are reached in the impregnation process. This results in the formation of a gel polymer electrolyte having an uneven degree of crosslinking, and the gel polymer electrolyte may be unevenly impregnated into the electrode assembly.

[0083] However, in exemplary embodiments, the gel polymer electrolyte composition includes the polymerization inhibitor, thereby preventing premature polymerization between polymerizable monomers when the gel polymer electrolyte composition is stored at room temperature. Accordingly, the storage stability of the gel polymer electrolyte composition can be improved.

[0084] In addition, since the uncured gel polymer electrolyte composition is injected into the battery case, the gel polymer electrolyte composition can be cured at the process temperature and time during the impregnation process. Accordingly, a gel polymer electrolyte having a uniform degree of crosslinking is formed, and the gel polymer electrolyte can be uniformly impregnated into the electrode assembly. In other words, the processability of the impregnation process of the gel polymer electrolyte composition can be improved.

[0085] Meanwhile, the gel polymer electrolyte may include a polymerizable polymer formed by crosslinking the polymerizable monomers, the electrolyte salt, the organic solvent, the polymerization initiator, and the polymerization inhibitor.

[0086] Additionally, the secondary battery may include the gel polymer electrolyte and the positive electrode and the negative electrode impregnated with the gel polymer electrolyte.

[0087] The above positive electrode is not particularly limited, and may include a lithium-transition metal oxide such as lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), or lithium nickel oxide (LiNiO2) as a positive electrode active material, or a lithium-transition metal composite oxide in which some of these transition metals are replaced with other transition metals.

[0088] For example, the lithium-transition metal oxide may include nickel (Ni) and further include at least one selected from the group consisting of cobalt (Co) and manganese (Mn). For example, the cathode active material may include an NCM-based cathode active material; a Mn-rich-based cathode active material; or an LLO (Li-rich layered oxides, Over Lithiated Oxides, Over-lithiated layered oxide, OLO, LLOs)-based cathode active material. For example, the lithium-transition metal oxide may have a structure represented by the following chemical formulas 1 to 3.

[0089] [Chemical Formula 1]

[0090] Li a Ni b M 1-b O2

[0091] In the above chemical formula 1, 0.9≤a≤1.2, b≥0.5, and M is at least one of Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Ba, and Zr. Specifically, in the above chemical formula 1, 0.95≤a≤1.08 may be satisfied, and b may be 0.6 or more, 0.8 or more, greater than 0.8, 0.9 or more, or 0.98 or more. Specifically, in the above chemical formula 1, M may include Co, Mn, or Al, and more specifically, M may include Co and Mn, and optionally further include Al.

[0092] [Chemical Formula 2]

[0093] pLi2MnO3ㆍ(1-p)Li q JO2

[0094] In the above chemical formula 2, 0 <p<1이고, 0.9≤q≤1.2이며, J는 Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg 및 B로 이루어진 군에서 선택되는 하나 이상의 원소일 수 있다.

[0095] [Chemical Formula 3]

[0096] Li 1+x M 1-x O2

[0097] In the above chemical formula 3, 0≤x≤0.4, and M is at least one of Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ni, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Ba, and Zr. Specifically, in the above chemical formula 3, M may include Ni, Co, Mn, or Al, and more specifically, may include Ni, Co, and Mn, and optionally further include Al.

[0098] Additionally, the above cathode active material may be a lithium iron phosphate (LFP)-based cathode active material represented by the chemical formula LiFePO4.

[0099] In addition, the lithium-transition metal oxide may be a secondary particle formed by assembling or agglomerating a plurality of primary particles to form a substantially single particle, or may be in the form of a single particle. The single particle form may mean, for example, excluding a secondary particle formed by assembling or agglomerating a plurality of primary particles (for example, more than 10) to form a substantially single particle. However, the single particle form does not exclude a case where 2 to 10 single particles are attached or adhered to each other to form a substantially single body form (for example, a structure converted into a single particle). In some embodiments, the positive electrode active material may include both a secondary particle form and a single particle form.

[0100] The above negative electrode is not particularly limited, and the negative electrode active material may include a carbon-based active material such as artificial graphite or natural graphite, or silicon oxide (SiOx; 0 <x<2), Si-C 복합체, pure Si 등의 규소계 활물질, 리튬 메탈, 리튬-메탈 합금 등의 금속을 포함할 수 있다.

[0101] Meanwhile, the lithium secondary battery may be a non-anode secondary battery. That is, it may be a battery in which a negative electrode active material layer is not formed on the negative electrode current collector during the battery assembly process. When a non-anode lithium secondary battery is initially charged or charged for the first time, the main positive electrode active material and the sacrificial positive electrode active material are delithiated, and lithium ions generated from the positive electrode active material are reduced on the negative electrode current collector to form a lithium layer of a lithium metal layer or a solid lithium layer.

[0102] Hereinafter, the present disclosure will be described in more detail with reference to examples. The following examples are intended to illustrate one example of the present disclosure and are not intended to limit the present disclosure.

[0103] Examples 1 to 4 and Comparative Examples 1 to 3

[0104] A polymerizable monomer and a polymerization inhibitor were dissolved in a composition in which LiPF6, ethyl carbonate, and ethyl methyl carbonate were mixed in amounts of 12.3 wt%, 31.5 wt%, and 56.2 wt%, respectively, based on the total weight of LiPF6, ethyl carbonate, and ethyl methyl carbonate, by stirring at room temperature for 2 hours. Thereafter, a polymerization initiator was dissolved at room temperature to prepare a composition for a gel polymer electrolyte.

[0105] 2-[(Dimethoxyphosphoryl)oxy]ethyl acrylate was used as a polymerizable monomer, and was included in the composition for the gel polymer electrolyte at 7.5 wt%.

[0106] T-butyl peroxypivalate was used as a polymerization initiator, and was included in the composition for gel polymer electrolyte at 1 wt% of the total weight of the polymerizable monomer.

[0107] 4-Methoxyphenol was used as a polymerization inhibitor, and was included in the composition for gel polymer electrolyte in the amount shown in Table 1 below.

[0108] Polymerization inhibitor (ppm) Example 120 Example 240 Example 350 Example 480 Comparative Example 10 Comparative Example 210 Comparative Example 3100

[0109] Whether the polymerization inhibitor is dissolved

[0110] After dissolving the electrolyte salt, polymerizable monomer, and polymerization inhibitor in an organic solvent by stirring at room temperature (25°C) for 2 hours, the polymerization initiator was added to the organic solvent at room temperature. Thereafter, the organic solvent containing the polymerization initiator was left at room temperature to evaluate whether the polymerization inhibitor was dissolved in the gel polymer electrolyte composition (see Fig. 1), and the results are shown in Table 2 below.

[0111] Detection of polymerization inhibitor and amount detected

[0112] High performance liquid chromatography (HPLC) analysis was performed on the polymerization inhibitor and the gel polymer electrolyte compositions of Examples 1 to 3 and Comparative Example 2. The presence and amount of the polymerization inhibitor in the gel polymer electrolyte compositions were confirmed through HPLC analysis (see FIGS. 2 and 3), and the results are shown in Table 2 below.

[0113] Meanwhile, with regard to whether a polymerization inhibitor was detected, since the polymerization inhibitor exhibited a peak at 6.413 min, it was determined that a polymerization inhibitor was detected if a peak appeared at a time similar to 6.413 min in Fig. 2.

[0114] Furthermore, the detection amount according to the content of the polymerization inhibitor introduced in the gel polymer electrolytes of Examples 1, 2, and 4 is shown in Figure 3.

[0115] Whether the polymerization inhibitor is dissolved Whether the polymerization inhibitor is detected Example 1OO Example 2OO Example 3OO Example 4OO Comparative Example 1-X Comparative Example 2O- Comparative Example 3X-

[0116] Polymerization at room temperature (25℃)

[0117] The gel polymer electrolyte compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were stored at room temperature (25°C). The polymerization of the gel polymer electrolyte compositions was checked after 0, 3, 8, and 24 hours (see Fig. 4), and the results are shown in Table 3 below.

[0118] High temperature (70℃) polymerization

[0119] Polymerization was performed at a high temperature (70°C) for the gel polymer electrolyte compositions of Examples 1 to 4 and Comparative Examples 1 and 2. The polymerization of the gel polymer electrolyte compositions was confirmed after 10 and 30 minutes (see Fig. 5), and the results are shown in Table 3 below.

[0120] Time Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Whether polymerized at room temperature 0hXXXXXX-3hXXXXOO-8hXXXXOO-24hXXXXOO- Whether polymerized at high temperature 10minXXXXOO-30minOOOOOO-

[0121] As can be seen from Table 2 and Figure 1, the polymerization inhibitors of Examples 1 to 4 and Comparative Example 2 were dissolved in organic solvents, and the polymerization inhibitor of Comparative Example 3 was confirmed to be saturated with the organic solvent and swelled. From this, it can be seen that the polymerization inhibitor is smoothly dissolved in the organic solvent when included in the gel polymer electrolyte composition in an amount of 10 to 80 ppm.

[0122] In addition, as can be seen from Table 2 and Figure 2, the gel polymer electrolyte compositions of Examples 1 to 3 were confirmed to have a peak at a time similar to 6.413 min, but the gel polymer electrolyte composition of Comparative Example 1 was confirmed to have no peak at a time similar to 6.413 min. From this, it can be seen that the gel polymer electrolyte composition of the present disclosure includes a polymerization inhibitor.

[0123] Meanwhile, from Fig. 3, the greater the content of the polymerization inhibitor introduced into the gel polymer electrolyte composition, the greater the amount of polymerization inhibitor detected.

[0124] In addition, as can be seen from Table 3 and FIG. 4, when the gel polymer electrolyte compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were stored at room temperature, it was confirmed that the gel polymer electrolyte compositions of Examples 1 to 4 did not polymerize even after 0 hours, 3 hours, 8 hours, and 24 hours had passed. On the other hand, the gel polymer electrolyte compositions of Comparative Examples 1 and 2 did not polymerize when 0 hours had passed, but polymerized after 3 hours, 8 hours, and 24 hours had passed. From this, it can be seen that when the polymerization inhibitor is included in the gel polymer electrolyte composition at 20 to 80 ppm, the gel polymer electrolyte composition does not polymerize even if the gel polymer electrolyte composition is stored at room temperature for 24 hours. That is, it can be seen that the gel polymer electrolyte composition of the present disclosure is stored in a liquid state including 20 to 80 ppm of a polymerization inhibitor and is injected into the battery case.

[0125] In addition, as can be seen from Table 3 and Fig. 5, when the gel polymer electrolyte compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were polymerized at high temperatures, it was confirmed that the gel polymer electrolyte compositions of Examples 1 to 4 were not polymerized after 10 minutes, but were polymerized after 30 minutes. On the other hand, it was confirmed that the gel polymer electrolyte compositions of Comparative Examples 1 and 2 were polymerized after 10 and 30 minutes.

[0126] From this, it can be seen that when the polymerization inhibitor is included in the gel polymer electrolyte composition at 20 to 80 ppm, the gel polymer electrolyte composition does not polymerize even when polymerization proceeds at high temperature for 10 minutes, but polymerizes when polymerization proceeds for 30 minutes.

[0127] That is, since the impregnation process of the present disclosure is performed for at least 10 minutes and the composition for a gel polymer electrolyte includes 20 to 80 ppm of a polymerization inhibitor, it can be confirmed that the gel polymer electrolyte is not prematurely polymerized and can form a gel polymer electrolyte having a uniform degree of crosslinking upon curing. In addition, it can be seen that even if the composition for a gel polymer electrolyte includes 20 to 80 ppm of a polymerization inhibitor, the composition for a gel polymer electrolyte is not permanently non-polymerized.

[0128] While the embodiments of the present disclosure have been described in detail above, they are merely exemplary, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present disclosure should be determined by the technical spirit of the appended claims.

[0129] The specific implementations described in the examples are exemplary and do not limit the scope of the examples in any way. Furthermore, unless specifically stated as "essential," "important," or the like, an element may not be absolutely necessary for the application of the present disclosure.

[0130] The use of the term "above" and similar referential terms in the specification of embodiments (especially in the claims) may refer to both the singular and the plural. Furthermore, if a range is described in the embodiments, it is intended to include disclosure applying individual values ​​within the range (unless otherwise stated), and is equivalent to describing each individual value constituting the range in the detailed description. Finally, unless the order of steps constituting a method according to an embodiment is explicitly stated or otherwise stated to the contrary, the steps may be performed in any suitable order. The embodiments are not necessarily limited by the order in which the steps are described. The use of all examples or exemplary terms (e.g., "for example," etc.) in the embodiments is merely intended to further illustrate the embodiments, and the scope of the embodiments is not limited by the examples or exemplary terms, unless otherwise defined by the claims. Furthermore, those skilled in the art will recognize that various modifications, combinations, and variations may be made within the scope of the appended claims or their equivalents, depending on design conditions and factors.

Claims

1. A composition for a gel polymer electrolyte comprising an electrolyte salt, an organic solvent, a polymerizable monomer, a polymerization initiator, and a polymerization inhibitor.

2. In paragraph 1, A composition for a gel polymer electrolyte, wherein the polymerization inhibitor comprises at least one selected from the group consisting of an aromatic compound containing a hydroxyl group or an alkoxy group, a quinone-based compound, a phenocyanidin-based compound, and a nitrosobenzene-based compound.

3. In paragraph 2, A composition for a gel polymer electrolyte, wherein the aromatic compound containing the above hydroxyl group or alkoxy group contains two or more hydroxyl groups or two or more alkoxy groups.

4. In paragraph 2, A composition for a gel polymer electrolyte, wherein the aromatic compound containing the above hydroxyl group or alkoxy group further contains a nitro group or an alkyl group.

5. In paragraph 2, A composition for a gel polymer electrolyte, wherein the aromatic compound containing the above hydroxyl group or alkoxy group comprises a single ring or a fused ring in which two or more single rings are fused.

6. In paragraph 1, The above polymerization inhibitors are 4-methoxyphenol (MEHQ), 1,2-benzoquinone, 4-tert-butylcatechol (TBC), nitrobenzene, picric acid, t-butylhydroquinone (TBHQ), hydroquinone, p-methoxyphenol, phenothiazine, tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 2-tert-butyl-1,4-benzoquinone, A composition for a gel polymer electrolyte, comprising at least one selected from the group consisting of 6-tert-butyl-2,4-xylenol, 2,6-di-tert-butylphenol, 6-tert-butyl-2,4-xylenol, and 2,6-di-tert-butylphenol.

7. In paragraph 1, A composition for a gel polymer electrolyte, wherein the polymerization inhibitor is contained in an amount of 150 ppm or less based on the total weight of the composition for a gel polymer electrolyte.

8. In paragraph 1, A composition for a gel polymer electrolyte, wherein the polymerizable monomer has a polymerizable functional group including at least one group selected from the group consisting of a vinyl group, an epoxy group, an allyl group, an acrylic group, a (meth)acrylic group, an ether group, and a fluorine (F) group and a phosphate group.

9. In paragraph 8, A composition for a gel polymer electrolyte, wherein the polymerizable monomer comprises three or more of the polymerizable functional groups.

10. In paragraph 8, A composition for a gel polymer electrolyte, wherein the polymerizable monomer comprises a phosphate group, an acrylate group, and an ether group.

11. In paragraph 8, A composition for a gel polymer electrolyte, wherein the polymerizable monomer containing the phosphate group contains an electron donating group (EGD).

12. A gel polymer electrolyte comprising a polymerizable polymer, an electrolyte salt, an organic solvent, a polymerization initiator, and a polymerization inhibitor.

13. In paragraph 12, A gel polymer electrolyte, wherein the polymerization inhibitor comprises at least one selected from the group consisting of an aromatic compound containing a hydroxyl group or an alkoxy group, a quinone-based compound, a phenocyanidin-based compound, and a nitrosobenzene-based compound.

14. In paragraph 12, The above polymerization inhibitors are 4-methoxyphenol (MEHQ), 1,2-benzoquinone, 4-tert-butylcatechol (TBC), nitrobenzene, picric acid, t-butylhydroquinone (TBHQ), hydroquinone, p-methoxyphenol, phenothiazine, tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 2-tert-butyl-1,4-benzoquinone, A gel polymer electrolyte comprising at least one selected from the group consisting of 6-tert-butyl-2,4-xylenol, 2,6-di-tert-butylphenol, 6-tert-butyl-2,4-xylenol, and 2,6-di-tert-butylphenol.

15. A lithium secondary battery comprising a gel polymer electrolyte according to any one of claims 12 to 14 and a positive electrode and a negative electrode impregnated with the gel polymer electrolyte.

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