Gel polymer electrolyte-separator composite and electrochemical device including same

Abstract

The invention relates to a gel polymer electrolyte-separator composite for an electrochemical device and an electrochemical device including the same. According to the present invention, provided are a gel polymer electrolyte-separator composite material for an electrochemical device capable of preventing the occurrence of an internal short circuit caused by the growth of lithium dendrites, and an electrochemical device comprising the same.

Description

TECHNICAL FIELD

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0077201, filed on June 13, 2024, and Korean Patent Application No. 10-2025-0075673, filed on June 10, 2025, and the entire contents of the documents of said Korean Patent Applications are incorporated as part of the present specification.

[0003] The present application relates to a gel polymer electrolyte-separator composite and an electrochemical device including the same. BACKGROUND

[0004] As the functionality of mobile phones, notebook computers, tablet computers, mobile batteries, electric vehicles, personal mobile devices, and the like is increasing, the demand for electrochemical devices used as a driving power source therefor is steadily increasing. In particular, lithium secondary batteries having a high operating voltage and a high energy density per unit weight are most widely used.

[0005] A lithium secondary battery can generally be manufactured using a cathode and an anode including an electrode active material capable of intercalating and deintercalating lithium ions, and an electrolyte as a medium for transporting lithium ions.

[0006] Conventionally, as an electrolyte, a liquid electrolyte, particularly an ion-conductive organic liquid electrolyte prepared by dissolving a salt in a non-aqueous organic solvent, has been mainly used. However, such a liquid electrolyte has a risk of leakage during operation, and the high flammability of the non-aqueous organic solvent used causes problems such as fire and explosion. In addition, the liquid electrolyte can be decomposed during charging and discharging of the lithium secondary battery, or can generate a side reaction with the electrode, thereby generating gas inside the battery. Such a phenomenon is further accelerated during high-temperature storage, and thus the amount of generated gas can increase. The continuously generated gas not only causes an increase in the internal pressure of the battery, resulting in deformation of the battery such as swelling, but also causes adhesive partial imbalance on the electrode surface inside the battery, resulting in a problem that electrode reactions cannot occur uniformly over the entire electrode surface.

[0007] In order to overcome these stability problems of the liquid electrolyte, a method of using a gel polymer electrolyte having a low risk of leakage has been proposed. However, since the gel polymer electrolyte also contains a non-aqueous organic solvent, a problem regarding the thermal stability of the electrochemical device is still under discussion.

[0008] Meanwhile, in the case of an electrochemical device in which lithium metal is applied as an anode, uneven lithium deposition occurs during repeated charging and discharging processes, and due to this, lithium dendrites grow on the surface of the lithium metal. However, the abnormally grown lithium dendrites can penetrate a separator and cause internal short-circuiting with a cathode, thereby causing a fire and explosion. SUMMARY

[0009] TECHNICAL PROBLEM

[0010] The present application aims to provide a gel polymer electrolyte-separator composite for an electrochemical device that can prevent the occurrence of internal short-circuiting due to the growth of lithium dendrites.

[0011] Furthermore, the present application aims to provide an electrochemical device including a gel polymer electrolyte-separator composite for an electrochemical device.

[0012] TECHNICAL SOLUTION

[0013] According to one embodiment of the present application,

[0014] A gel polymer electrolyte-separator composite for an electrochemical device is provided, which includes:

[0015] a porous polymer substrate,

[0016] a plurality of porous coating layers sequentially stacked on the porous polymer substrate, and

[0017] a gel polymer electrolyte impregnated into the porous polymer substrate and the porous coating layers;

[0018] wherein the plurality of porous coating layers includes:

[0019] a porous coating layer including a first inorganic fine particle of at least one type selected from the group consisting of lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), a glass based on (LiAlTiP) x O y (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w, 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), and SiS2-based glasses (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), and

[0020] The porous coating layer comprises at least one type of second inorganic fine particles selected from the group consisting of SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, SiC, and BaTiO3.

[0021] According to another embodiment of the present application, there is provided an electrochemical device comprising a gel polymer electrolyte-separator composite.

[0022] Hereinafter, a more detailed description of the gel polymer electrolyte-separator composite for an electrochemical device according to the embodiments of the present application and the electrochemical device comprising the same will be given.

[0023] The terms or words used in the present specification and claims should not be interpreted as being limited to the commonly used meanings or meanings in dictionaries, but should be interpreted based on the concept of the inventor's intention, which is properly defined in the principles of the present application, on the basis of the technical spirit of the present application, and on the meaning and concept consistent with the technical spirit of the present application.

[0024] Unless otherwise defined herein, all technical and scientific terms used have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0025] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0026] As used herein, the meaning of "include" or "comprise" designates the presence of the stated features, regions, integers, steps, operations, elements, and / or components but does not exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0027] Since the present application is capable of various modifications and is capable of having various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present application to a particular disclosed form, and it should be understood that it includes all modifications, equivalents, and alternatives included in the spirit and scope of the present application.

[0028] In the present specification, when a positional relationship between two parts is described as, for example, "on", "above", "below", "next to", and the like, unless the expression "directly" or "immediately" is used, one or more other parts can be positioned between the two parts.

[0029] In the present specification, when a chronological order is described as, for example, "after", "next", "subsequent to", "before", and the like, unless the expression "directly" or "immediately" is used, it can include a non-continuous case.

[0030] In the present specification, the term "at least one" is to be understood as including all possible combinations of one or more relevant items.

[0031] Further, the terms including ordinal numbers such as "first" and "second" in the present specification are used to distinguish one component from another component, and do not limit the components. For example, the first component can also be referred to as the second component, and similarly, the second component can also be referred to as the first component, within the scope of the present application.

[0032] According to one embodiment of the present application,

[0033] A gel polymer electrolyte-separator composite for an electrochemical device is provided, which includes:

[0034] a porous polymer substrate,

[0035] a plurality of porous coating layers sequentially stacked on the porous polymer substrate, and

[0036] a gel polymer electrolyte impregnated into the porous polymer substrate and the porous coating layers;

[0037] wherein the plurality of porous coating layers includes:

[0038] a porous coating layer including a first inorganic fine particle of at least one type selected from the group consisting of lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), a glass based on (LiAlTiP) x O y (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Lix Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), and SiS2-based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), and

[0039] a porous coating containing at least one type of second inorganic fine particles selected from the following: SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, SiC, and BaTiO3.

[0040] As a result of continuous research by the inventors, it has been determined that a gel polymer electrolyte-separator composite including a plurality of porous coatings satisfying the above configuration can prevent the occurrence of an internal short circuit caused by the growth of lithium dendrites on a lithium metal electrode. The first inorganic fine particles contained in the plurality of porous coatings can electrochemically inhibit the growth of lithium dendrites. In addition, the second inorganic fine particles contained in the plurality of porous coatings provide excellent density and durability, thereby preventing the physical penetration of lithium dendrites into the gel polymer electrolyte-separator composite. The gel polymer electrolyte-separator composite for an electrochemical device can provide a highly safe electrochemical device through the complementary properties exhibited by the plurality of porous coatings.

[0041] The gel polymer electrolyte-separator composite for an electrochemical device according to the above embodiment includes a porous polymer substrate, a plurality of porous coatings sequentially stacked on the porous substrate, and a gel polymer electrolyte impregnated into the porous polymer substrate and the porous coatings.

[0042] In the gel polymer electrolyte-separator composite for an electrochemical device, the porous polymer substrate has a high porosity that allows lithium ions to migrate between the cathode and the anode, and can be applied without particular limitation as long as it does not cause a chemical change in the electrochemical device.

[0043] According to one embodiment, the porous polymer substrate may contain at least one polymer selected from the following: polyethylene, polypropylene, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyamide-imide, polyetherimide, polyether ether ketone, polyether sulfone, polyphenylene ether, polyphenylene sulfide, and polyethylene naphthalate.

[0044] According to one embodiment, the thickness of the porous polymer substrate can range from 5 μm to 100 μm. To ensure the required mechanical properties of the substrate, a thickness of at least 5 μm is preferred. However, if the substrate is too thick, the ionic conductivity may decrease, which could lead to a reduction in the performance of the electrochemical device. Therefore, a thickness of no more than 100 μm is preferred for the porous polymer substrate.

[0045] According to one embodiment, the tensile strength of the porous polymer substrate in both the machine direction (MD) and transverse direction (TD) is preferably 300 kgf / cm. 2 Up to 1000 kgf / cm 2 To prevent defects in the porous polymer substrate during the manufacture and operation of the electrochemical device, the substrate preferably meets this tensile strength range.

[0046] According to one embodiment, the porous polymer substrate can have a pore size in the range of 10 nm to 1000 nm and a porosity of 10% to 90%. When the porous polymer substrate has a pore size and porosity within this range, it can provide the necessary separation function and mechanical strength of a separator without acting as a barrier to ion conduction.

[0047] The pore size and porosity of polymer substrates can be measured using instruments such as scanning electron microscopy (SEM) or capillary flow porometer (CFP). Alternatively, the porosity of porous polymer substrates can be calculated as a percentage (%) using the following equation: the actual density of the porous polymer substrate (i.e., weight per unit area divided by thickness, denoted as X) divided by the theoretical density of the polymer substrate (denoted as Y), subtracting the resulting ratio from 1, and then multiplying by 100.

[0048] Porosity (%) of porous polymer substrate = [1 - (W / Z)] × 100

[0049] In a gel polymer electrolyte-separator composite material for electrochemical devices, a plurality of porous coatings are sequentially stacked on a porous polymer substrate.

[0050] Multiple porous coatings include two or more porous coatings.

[0051] In one example, a plurality of porous coatings includes a first porous coating comprising first inorganic fine particles that can electrochemically inhibit the growth of lithium dendrites on a lithium metal electrode. The first porous coating is formed on a porous polymer substrate. Additionally, the plurality of porous coatings includes a second porous coating comprising second inorganic fine particles that can prevent the physical penetration of lithium dendrites through a gel polymer electrolyte-separator composite. The second porous coating is formed on the first porous coating.

[0052] Preferably, a gel polymer electrolyte-separator composite for an electrochemical device can include a porous polymer substrate, a first porous coating stacked on the porous polymer substrate and comprising first inorganic fine particles, a second porous coating stacked on the first porous coating and comprising second inorganic fine particles, and a gel polymer electrolyte impregnated into the porous polymer substrate and the porous coatings.

[0053] The gel polymer electrolyte-separator composite for an electrochemical device has a structure in which the layers are stacked in sequence on the porous polymer substrate. The first porous coating comprises first inorganic fine particles capable of electrochemically inhibiting the growth of lithium dendrites, while the second porous coating comprises second inorganic fine particles in the form of needle-like particles having a high aspect ratio, which are used to prevent the physical penetration of lithium dendrites. By acting complementarily, these two coatings can effectively prevent dendrite growth and electrode short-circuiting at the lithium metal anode. This layered structure significantly enhances the safety and reliability of the electrochemical device and ensures high stability even during long-term operation in a high energy density environment of a lithium metal secondary battery.

[0054] According to one embodiment, the first inorganic fine particles can be inorganic particles comprising at least one compound selected from the following: lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), glass based on (LiAlTiP) x O y (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li<0000​​​​​​​​​​​​Si y S z 0 <x<3,0<y<2,0<z<4)。

[0055] The second inorganic fine particles may be inorganic particles containing at least one compound selected from the following: SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, SiC, and BaTiO3.

[0056] According to one embodiment, the first inorganic fine particles and the second inorganic fine particles may each independently have a particle shape selected from needle-shaped particles, angular particles, dendritic particles, fibrous particles, flaky particles, granular particles, irregular particles, nodular particles and spherical particles.

[0057] Preferably, the first inorganic fine particles can be angular particles, granular particles, or spherical particles.

[0058] Preferably, the second inorganic fine particles can be needle-shaped particles with an aspect ratio in the range of 5 to 10. Aspect ratio refers to the ratio of the length of a particle to its diameter. To impart excellent density and durability to the second porous coating, the second inorganic fine particles are preferably needle-shaped particles with an aspect ratio of 5.0 or greater, or 5.1 or greater, or 5.2 or greater. However, if the aspect ratio is too large, the porosity of the second porous coating may become too low, resulting in increased resistance. Therefore, the second inorganic fine particles are preferably needle-shaped particles with an aspect ratio of 10.0 or less, or 9.5 or less, or 8.0 or less, or 7.5 or less, or 7.0 or less, or 6.5 or less, or 6.0 or less, or 5.5 or less. Specifically, the second inorganic fine particles can be needle-shaped particles with an aspect ratio in the range of 5.0 to 10.0, or 5.1 to 10.0, or 5.1 to 9.5, or 5.1 to 9.0, or 5.1 to 8.5, or 5.1 to 8.0, or 5.2 to 8.0, or 5.2 to 7.5, or 5.2 to 7.0, or 5.2 to 6.5, or 5.2 to 6.0, or 5.2 to 5.5.

[0059] Because of the relatively high aspect ratio of the needle-like particles, the contact area between particles within the porous coating is increased, enabling the formation of a more densely packed particle structure. Therefore, the mechanical strength and structural stability of the second porous coating are improved, and this layer can more effectively act as a barrier to physically block the penetration of lithium dendrites. In particular, due to the directional nature of the needle-like particles, if the particles are aligned in parallel during the coating process, they can further deflect or redirect the dendrite growth path within the layered structure, thereby enhancing the safety of the electrochemical device. Furthermore, the high surface area to volume ratio of the needle-like particles enhances the bonding with the polymer binder, which is beneficial for improving the heat resistance and durability of the coating.

[0060] According to one implementation, the cumulative 50% particle size (D50) of the first inorganic fine particles and the second inorganic fine particles, as measured by laser diffraction scattering particle size distribution analysis, is independently between 20 nm and 500 nm.

[0061] Laser diffraction scattering particle size distribution measurement is performed by dispersing inorganic fine particles in a dispersion medium, irradiating the dispersion with a laser beam, and simultaneously collecting the scattered light (forward scattered light) to obtain a diffraction pattern. The particle size distribution is then determined from the diffraction pattern. This method allows for relatively simple, rapid, and high-precision measurement of particle size distribution. Here, the cumulative 50% particle size (D50) refers to the particle size accumulated from the smallest size to 50% of the particle mass, as measured using a laser diffraction scattering particle size distribution apparatus.

[0062] To ensure uniform dispersion of inorganic fine particles during the formation of the porous coating, the D50 value is preferably 20 nm or greater, 50 nm or greater, 100 nm or greater, or 150 nm or greater. However, if the particle size of the inorganic fine particles is too large, it becomes difficult to uniformly coat the porous coating, and damage to the porous polymer substrate or electrodes may occur during the rolling process after drying. Therefore, the D50 value is preferably 500 nm or less, 450 nm or less, 400 nm or less, or 350 nm or less.

[0063] Specifically, the D50 value can be 20 nm to 500 nm, or 50 nm to 500 nm, or 50 nm to 450 nm, or 100 nm to 450 nm, or 100 nm to 400 nm, or 150 nm to 400 nm, or 150 nm to 350 nm.

[0064] More specifically, the D50 value of the first inorganic fine particles is preferably 20 nm to 500 nm, or 100 nm to 450 nm, or 150 nm to 350 nm, or 200 nm to 350 nm, or 250 nm to 350 nm, which is advantageous for forming a porous coating and electrochemically suppressing the growth of lithium dendrites. Furthermore, the second inorganic fine particles are preferably needle-like particles with a D50 value of 20 nm to 500 nm, or 50 nm to 400 nm, or 100 nm to 300 nm, or 150 nm to 200 nm, which is advantageous for forming a porous coating and physically preventing the penetration of lithium dendrites.

[0065] Each of the plurality of porous coatings contains a polymer binder and inorganic fine particles dispersed in the polymer binder.

[0066] In one example, in a porous coating, inorganic fine particles are interconnected and fixed by a polymer binder, and a porous structure can be formed due to the interstitial volume between the inorganic fine particles.

[0067] After impregnation with a gel polymer electrolyte, the polymer binder can gel, thereby exhibiting high swelling degree. Preferably, the polymer binder is a compound selected from at least one of the following: polyvinylidene fluoride, poly(vinylidene fluoride-copolymer-trichloroethylene), poly(vinylidene fluoride-copolymer-trifluorochloroethylene), poly(vinylidene fluoride-copolymer-trifluoroethylene), poly(vinylidene fluoride-copolymer-tetrafluoroethylene), poly(vinylidene fluoride-copolymer-hexafluoropropylene), spandex, butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, and polyvinyl acetate.

[0068] In addition to the compounds exemplified above, polymeric adhesives may also include at least one compound selected from the following: polyimide, polyetherimide, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluorinated rubber.

[0069] In one embodiment, each of the plurality of porous coatings may comprise 1% to 90% by weight of a polymeric binder and 10% to 99% by weight of inorganic fine particles. To ensure the porous coatings have appropriate porosity and insulating properties, it is preferred that the inorganic fine particles be included in an amount of at least 10% by weight. However, if the inorganic fine particles are included in excess, the mechanical properties of the porous coating may be reduced due to decreased adhesion. Therefore, it is preferred that the inorganic fine particles be included in an amount of 99% by weight or less.

[0070] In one embodiment, the thickness of each of the porous coatings is preferably adjusted to be in the range of 2 μm to 100 μm, or 2 μm to 80 μm, or 2 μm to 50 μm, or 2 μm to 20 μm to achieve suitable performance.

[0071] Gel polymer electrolyte-separator composites for electrochemical devices include gel polymer electrolytes impregnated into a porous polymer substrate and a porous coating.

[0072] Gel polymer electrolytes contain lithium salts, matrix gel polymers, and non-aqueous organic solvents.

[0073] Lithium salts are used as lithium-ion sources in electrochemical devices, enabling basic operation of the device and facilitating the migration of lithium ions between electrodes.

[0074] Specifically, lithium salts may include one or more compounds selected from the following: LiBF4, LiPF6, LiSbF6, LiAsF6, LiOH, LiOH·H2O, LiBOB, LiClO4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO2)2, LiN(CF3SO2)2, CF3SO3Li, LiC(CF3SO2)3, LiC4BO8, LiTFSI, LiFSI, LiCl, LiI, LiB(C2O4)2, and LiClO4.

[0075] Based on 100 parts by weight of the total composition used to form the gel polymer electrolyte, lithium salt may be included in an amount of 10 to 50 parts by weight. To ensure an appropriate level of ionic conductivity in the gel polymer electrolyte, lithium salt is preferably included in an amount of 10 parts by weight or more, 12 parts by weight or more, or 15 parts by weight or more based on 100 parts by weight of the total composition. However, if an excessive amount of lithium salt is applied, the undissociated lithium salt remaining in a crystalline state may reduce ionic conductivity and decrease the mechanical strength of the gel polymer electrolyte. Therefore, based on 100 parts by weight of the total composition, lithium salt is preferably included in an amount of 50 parts by weight or less, 47 parts by weight or less, or 45 parts by weight or less. Specifically, based on 100 parts by weight of the total composition, lithium salt may be included in an amount of 10 to 50 parts by weight, 12 to 50 parts by weight, 12 to 47 parts by weight, 15 to 47 parts by weight, or 15 to 45 parts by weight.

[0076] The matrix gel polymer can be formed into a three-dimensional gel network structure through the polymerization of polyfunctional acrylate compounds.

[0077] In one example, a multifunctional acrylate compound may include one or more of the following: tetraethylene glycol diacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyester dimethacrylate, trimethylolpropane trimethacrylate, ethoxylated bisphenol A dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, bis(trimethylolpropane) tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0078] Based on a total of 100 parts by weight of the composition for forming the gel polymer electrolyte, the polyfunctional acrylate compound may be included in an amount from 0.5 parts by weight to 20 parts by weight. To minimize the content of free liquid and ensure proper gel matrix formation, the polyfunctional acrylate compound is preferably included in an amount of 0.5 parts by weight or more, or 1 part by weight or more, or 2 parts by weight or more, based on a total of 100 parts by weight of the composition. However, if the polyfunctional acrylate compound is included in excess, it may reduce the ion transport capacity of the gel polymer electrolyte. Therefore, based on a total of 100 parts by weight of the composition, the polyfunctional acrylate compound is preferably included in an amount of 20 parts by weight or less, or 17 parts by weight or less, or 15 parts by weight or less. Specifically, based on a total of 100 parts by weight of the composition, the polyfunctional acrylate compound may be included in an amount of 0.5 to 20 parts by weight, or 1 to 20 parts by weight, or 1 to 17 parts by weight, or 2 to 17 parts by weight, or 2 to 15 parts by weight.

[0079] The composition for forming the gel polymer electrolyte may also contain a polymerization initiator for initiating the polymerization reaction of the polyfunctional acrylate compound.

[0080] The polymerization initiator can be any compound known in the art suitable for initiating polymerization reactions of polyfunctional acrylate compounds, without particular limitation. Preferably, the polymerization initiator can be selected from acetyl peroxide, benzoyl peroxide, dilauroyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide-2-ethylhexanoate, cumyl hydroperoxide, hydroperoxide, 2,2'-azobis(cyanobutane), 2,2'-azobis(methylbutyronitrile), azobisisobutyronitrile, and azobis-dimethylpentanonitrile, or a combination of one or more thereof.

[0081] Based on a total of 100 parts by weight of the composition, the polymerization initiator may be included in an amount from 0.01 parts by weight to 5 parts by weight. To ensure a proper polymerization reaction, the polymerization initiator is preferably included in an amount of 0.01 parts by weight or more, or 0.05 parts by weight or more, or 0.1 parts by weight or more, based on a total of 100 parts by weight of the composition. However, if an excessive amount of polymerization initiator is used, the residual initiator after the polymerization reaction may degrade the properties of the gel polymer electrolyte. Therefore, based on a total of 100 parts by weight of the composition, the polymerization initiator is preferably included in an amount of 5 parts by weight or less, or 4.5 parts by weight or less, or 4 parts by weight or less. Specifically, based on a total of 100 parts by weight of the composition, the polymerization initiator may be included in an amount of 0.01 parts by weight to 5 parts by weight, or 0.05 parts by weight to 5 parts by weight, or 0.05 parts by weight to 4.5 parts by weight, or 0.1 parts by weight to 4.5 parts by weight, or 0.1 parts by weight to 4 parts by weight.

[0082] The non-aqueous organic solvent contained in the gel polymer electrolyte can be any compound known in the art as suitable for gel polymer electrolytes, without particular limitation.

[0083] Specifically, non-aqueous organic solvents may include one or more of the following: ester solvents, such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents, such as dibutyl ether and tetrahydrofuran; ketone solvents, such as cyclohexanone; aromatic hydrocarbon solvents, such as benzene and fluorobenzene; carbonate solvents, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents, such as ethanol and isopropanol; nitriles in the form of R-CN (where R is a C2-C20 straight-chain, branched, or cyclic hydrocarbon group, which may include double bonds, cyclic structures, or ether bonds); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane; and sulfolane.

[0084] Preferably, the non-aqueous organic solvent may include one or more of the following: methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone, dibutyl ether, tetrahydrofuran, cyclohexanone, benzene, fluorobenzene, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, butyl carbonate, ethanol, isopropanol, dimethylformamide, 1,3-dioxolane, dimethyl sulfone, sulfolane, and triethylene glycol dimethyl ether.

[0085] Based on a total of 100 parts by weight of the composition for forming the gel polymer electrolyte, a non-aqueous organic solvent may be included in an amount of 15 to 85 parts by weight. To ensure uniform mixing of the composition, the non-aqueous organic solvent is preferably included in an amount of 15 parts by weight or more, or 17 parts by weight or more, or 20 parts by weight or more, based on a total of 100 parts by weight of the composition. However, if an excessive amount of non-aqueous organic solvent is used, it may hinder the formation of the gel matrix and may reduce the mechanical strength of the gel polymer electrolyte. Therefore, based on a total of 100 parts by weight of the composition, the non-aqueous organic solvent is preferably included in an amount of 85 parts by weight or less, or 80 parts by weight or less, or 75 parts by weight or less. Specifically, based on a total of 100 parts by weight of the composition, the non-aqueous organic solvent may be included in an amount of 15 to 85 parts by weight, or 17 to 85 parts by weight, or 17 to 80 parts by weight, or 20 to 80 parts by weight, or 20 to 75 parts by weight.

[0086] In one embodiment, the lithium salt may be included at a concentration of 0.5 M to 2.5 M, or 0.5 M to 2.0 M, or 0.5 M to 1.5 M relative to the non-aqueous organic solvent. Considering the relative proportion of the lithium salt to the non-aqueous organic solvent that can ionize the lithium salt, and to ensure a proper supply of lithium ions required for the operation of the electrochemical device, the lithium salt may be added in an appropriate amount. To ensure a sufficient level of ionic conductivity in the gel polymer electrolyte, the lithium salt is preferably included at a concentration of 0.5 M or higher relative to the non-aqueous organic solvent. However, if an excessive amount of lithium salt is used, the residual lithium salt in an undissociated or crystalline state may reduce ionic conductivity and decrease the mechanical strength of the gel polymer electrolyte. Therefore, the lithium salt is preferably included at a concentration of 2.5 M or lower, or 2.0 M or lower, or 1.5 M or lower relative to the non-aqueous organic solvent.

[0087] The composition for forming the gel polymer electrolyte can be prepared by dissolving a lithium salt in a non-aqueous organic solvent and then adding a polyfunctional acrylate compound thereto.

[0088] The composition for forming the gel polymer electrolyte can be incorporated into an electrochemical device in a state of being impregnated onto a porous polymer substrate and multiple porous coatings. Appropriate thermal initiation polymerization is applied to the composition to form the gel polymer electrolyte.

[0089] Meanwhile, the gel polymer electrolyte-separator composite material for electrochemical devices can be provided by a method comprising: applying a slurry containing a polymer binder, first inorganic fine particles and a solvent to a porous polymer substrate to form a first porous coating; applying a slurry containing a polymer binder, second inorganic fine particles and a solvent to the first porous coating to form a second porous coating; and impregnating the porous polymer substrate, the first porous coating and the second porous coating with a gel polymer electrolyte.

[0090] Alternatively, the gel polymer electrolyte-separator composite material for electrochemical devices can be provided via a method comprising: applying a slurry comprising a polymer binder, first inorganic fine particles, second inorganic fine particles, and a solvent onto a porous polymer substrate to form a first porous coating comprising the first inorganic fine particles and a second porous coating comprising the second inorganic fine particles; and impregnating the porous polymer substrate, the first porous coating, and the second porous coating with a gel polymer electrolyte. In a manufacturing method in which the first and second inorganic fine particles are mixed and coated together, phase separation occurs due to differences in particle shape and size range between the first and second inorganic fine particles, thereby forming the first and second porous coatings. Due to this phase separation, the first porous coating is predominantly occupied by the first inorganic fine particles, while the second porous coating is predominantly occupied by the second inorganic fine particles.

[0091] In the manufacturing method according to the second method, when a mixed slurry containing first and second inorganic fine particles is applied during a single coating process, the first porous coating and the second porous coating can be formed simultaneously by utilizing natural phase separation phenomena based on differences in the physical properties of the particles (e.g., particle shape, particle size, density, surface energy, etc.). To stably achieve such phase separation-based structure formation, the coating and drying process conditions of the mixed slurry must be precisely controlled.

[0092] For example, the slurry temperature during coating plays a crucial role in maintaining particle dispersion stability and slurry viscosity. At temperatures too low, particle agglomeration is promoted due to increased viscosity, while at temperatures too high, particle fixation may occur before phase separation due to rapid solvent evaporation. Therefore, it is preferable to control the slurry temperature during coating within the range of 15°C to 50°C or 20°C to 40°C, thereby appropriately maintaining the interaction and dispersion state between particles.

[0093] As another example, the drying conditions after coating are a major factor determining the phase separation effect utilizing the differences in gravity and viscosity of the inorganic fine particles. Specifically, the drying temperature and time should provide sufficient time for the particles in the slurry to gradually move their positions, while also preventing interlayer mixing due to excessively rapid solvent evaporation. Preferably, the drying process after coating is carried out at a temperature of 50°C to 90°C or 60°C to 85°C for 1 to 30 minutes or 5 to 25 minutes, thereby causing the first inorganic fine particles to preferentially locate in the lower part, while the second inorganic fine particles preferentially locate in the upper part. The drying time can be adjusted according to the coating thickness, the viscosity of the slurry, and the volatility characteristics of the solvent used.

[0094] Furthermore, the air velocity applied during the drying process also affects the positional movement of the particles. If the air velocity is too high, it causes rapid drying of the solvent, thereby reducing particle flowability and hindering phase separation. Conversely, if the air velocity is too low, an uneven porous structure may form in the coating due to excessive solvent residue. Therefore, drying is preferably carried out under constant air velocity conditions of 0.3 m / s to 5.0 m / s or 0.5 m / s to 4.5 m / s, depending on the composition of the slurry and the characteristics of the coating apparatus. It is advantageous to set the air velocity to act parallel to the coating surface to promote the vertical positioning of the inorganic fine particles.

[0095] By employing these process conditions and controlling the natural density gradient and gravitational settling phenomena based on the particle size and shape within the slurry, a dual-porous coating, in which first and second inorganic fine particles are predominantly distributed, can be formed without separate multilayer coating processes. This not only improves process efficiency but also reduces process sensitivity in controlling the shape of the multilayer structure, thereby improving stability and reproducibility in large-area applications.

[0096] As a solvent contained in the slurry, a solvent that exhibits a solubility of 1% or more, 2.5% or more, 5% or more, 7.5% or more, or 10% or more of solubility relative to the polymer binder at room temperature (25°C) can preferably be used.

[0097] Preferably, the solvent may be selected from at least one of the following: methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone, dibutyl ether, tetrahydrofuran, cyclohexanone, benzene, fluorobenzene, N-methyl-2-pyrrolidone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, dimethylformamide, 1,3-dioxolane, and sulfolane.

[0098] The slurry preferably has a solids content of 40% to 80% by weight. If the solids content of the slurry is too high, it may lead to an increase in viscosity, thereby preventing the slurry from penetrating into the pore regions of the porous polymer substrate, and as a result, the interfacial adhesion between the porous polymer substrate and the porous coating may deteriorate. However, if the solids content of the slurry is too low, pinholes may occur during slurry coating, and the drying efficiency of the slurry coating may deteriorate. Specifically, the solids content of the slurry can be 40% by weight or more; and 80% by weight or less, or 70% by weight or less, or 60% by weight or less. Preferably, the solids content of the slurry can be 40% to 80% by weight, or 40% to 70% by weight, or 40% to 60% by weight.

[0099] As a method for applying a slurry to a porous polymer substrate, conventional coating methods known in the art to which this invention pertains can be applied. For example, spin coating, dip coating, die coating, roll coating, comma coating, gravure coating, bar coating, screen coating, silkscreen printing, inkjet printing, doctor blade coating, or combinations thereof can be used for slurry coating. The thickness of the coating formed on the porous polymer substrate during slurry coating can be adjusted taking into account the composition of the slurry and the thickness of the final porous coating to be formed.

[0100] The step of forming a porous coating can be performed by vaporizing the solvent from the slurry coated on the porous polymer substrate. Preferably, the step of forming the porous coating can be performed at a temperature of 80°C to 120°C or 80°C to 110°C. If this temperature range is not met, the drying efficiency may decrease or the shape of the porous polymer substrate or the porous coating may change, resulting in defects.

[0101] The porous coating formed by the above method can contain 1% to 90% by weight of polymer binder and 10% to 99% by weight of inorganic fine particles. To impart appropriate porosity and insulating properties to the porous layer, the inorganic fine particles are preferably included in an amount of 10% by weight or more. However, if the inorganic fine particles are included in excess, the mechanical properties of the porous coating may deteriorate due to weakened adhesive strength. Therefore, the inorganic fine particles are preferably included in an amount of 99% by weight or less.

[0102] Meanwhile, according to another embodiment of the present invention, an electrochemical device comprising the above-described gel polymer electrolyte-separator composite material is provided.

[0103] When the above-mentioned gel polymer electrolyte-separator composite material is applied to an electrochemical device, internal short circuits caused by the growth of lithium dendrites can be prevented.

[0104] According to one embodiment, the electrochemical device includes a cathode, an anode, and a gel polymer electrolyte-separator composite material between the cathode and the anode.

[0105] Electrochemical devices include any device that undergoes an electrochemical reaction. Examples include primary batteries, secondary batteries, fuel cells, solar cells, and capacitors. Secondary batteries can be lithium-ion batteries. Lithium-ion batteries can be lithium metal batteries, lithium-ion batteries, lithium polymer batteries, lithium-ion polymer batteries, etc.

[0106] Electrochemical devices can be manufactured using conventional methods according to the art to which this invention pertains. As a non-limiting example, an electrochemical device can be manufactured by including: (i) inserting an electrode assembly formed by winding a cathode, an anode, and a separator between the cathode and the anode into a housing of the electrochemical device; and (ii) forming a gel polymer electrolyte by injecting the aforementioned composition for forming a gel polymer electrolyte into the housing and then allowing it to polymerize. Here, the separator comprises a porous polymer substrate and a plurality of porous coatings sequentially stacked on the porous polymer substrate.

[0107] The electrochemical device includes two electrodes, each comprising an electrode current collector layer and an electrode active material layer stacked on the electrode current collector layer.

[0108] For the electrode current collector layer, electrode current collectors that are conductive and will not cause chemical changes in the electrochemical device, as known in the technical field to which this invention pertains, can be used. For example, stainless steel; aluminum; nickel; titanium; calcined carbon; or electrode current collectors with surface treatments of carbon, nickel, titanium, silver, etc., on aluminum or stainless steel surfaces can be used as electrode current collectors.

[0109] Preferably, the thickness of the electrode current collector can be from 3 μm to 500 μm. To increase the adhesion strength with the electrode material, the electrode current collector can have fine irregularities formed on its surface. The electrode current collector can be in various forms, such as films, sheets, foils, meshes, porous bodies, foams, nonwoven fabrics, etc.

[0110] The electrode active material layer may comprise an electrode material composition, which is a mixture of electrode active material, conductive agent and binder.

[0111] Conductive agents can be used to impart electronic conductivity to electrodes. As conductive agents, any conductive agent possessing electronic conductivity without causing chemical changes in the electrochemical device can be used without particular limitation. As non-limiting examples, conductive agents can be carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lampblack, thermal cracking black, and carbon fiber; graphite, such as natural or artificial graphite; metal powders or fibers, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives. As conductive agents, one or a mixture of two or more of the above examples can be used.

[0112] The content of the conductive agent can be adjusted within a range that exhibits an appropriate level of conductivity without causing a reduction in the capacity of the electrochemical device. Preferably, the content of the conductive agent can be from 1% to 10% by weight or from 1% to 5% by weight relative to the total weight of the electrode material composition.

[0113] An adhesive is used to suitably attach the electrode material composition to the electrode current collector. As a non-limiting example, the adhesive may be polyvinyl alcohol, polyacrylate, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon resin, etc. One or a mixture of two or more of the above examples may be used as the adhesive.

[0114] The binder content can be adjusted within a range that exhibits an appropriate level of adhesion without causing a reduction in the capacity of the electrochemical device. Preferably, the binder content can be from 1% to 10% by weight or from 1% to 5% by weight relative to the total weight of the electrode material composition.

[0115] When the electrode is a cathode, any material capable of reversibly inserting and extracting lithium ions can be used as the cathode active material without particular restriction. For example, the cathode active material can be a composite oxide or phosphate containing lithium and metallic cobalt, manganese, nickel, iron, or combinations thereof.

[0116] As another example, the cathode active material can be a compound represented by any of the following chemical formulas: Li a A 1-b R b D2 (0.90≤a≤1.8, 0≤b≤0.5); Li a E 1-b R b O 2-c Dc (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);LiE 2-b R b O 4-c D c (0≤b≤0.5,0≤c≤0.05);Li a Ni 1-b-c Co b R c D d (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0 <d≤2);Li a Ni 1-b-c Co b R c O 2-d Z d (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0 <d<2);Li a Ni 1-b-c Co b R c O 2-d Z2(0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0 <d<2);Li a Ni 1-b- c Mr b R c D d (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0 <d≤2);Li a Ni 1-b-c Mr b R c O 2-d Z d (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0 <d<2);Li a Ni 1-b-c Mr b R c O 2-d Z2(0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0 <d<2);Li a Ni b HAVE BEEN c G d O2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0.001≤d≤0.1.);Li a Ni b Co c Mr d G eO2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a MnG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1.8, 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiTO2; LiNiVO4; Li (3-f) J2(PO4)3 (0≤f≤2); Li (3-f) Fe2(PO4)3 (0≤f≤2); and LiFePO4.

[0117] In the above chemical formulas, A is Ni, Co, Mn, or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; Z is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; T is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0118] Materials with a coating on the surface of the cathode active material can also be used, or a mixture of the cathode active material and the coated cathode active material can be used. As coating elements included in the coating, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof can be used.

[0119] According to one embodiment, the cathode active material may be included in an amount of 80% to 95% by weight relative to the total weight of the electrode material composition. Preferably, the content of the cathode active material may be 82% to 95% by weight, or 82% to 93% by weight, or 85% to 93% by weight, or 85% to 90% by weight relative to the total weight of the electrode material composition.

[0120] When the electrode is an anode, as the anode active material, it may include materials capable of reversibly undergoing insertion and extraction of lithium ions, lithium metal, lithium metal alloys, materials capable of doping and undoping lithium, and transition metal oxides.

[0121] As materials capable of reversibly undergoing insertion and extraction of lithium ions, carbonaceous materials can be exemplified, such as crystalline carbon, amorphous carbon, or a mixture thereof. Specifically, the carbonaceous material can be natural graphite, artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch, mesophase pitch-based carbon fiber, mesophase carbon microspheres, coke derived from petroleum or coal tar pitch, soft carbon, hard carbon, etc.

[0122] The lithium metal alloy can be an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, Bi, Ga, and Cd.

[0123] Materials capable of doping and undoping lithium can be Si, Si-C composites, SiOx (0 < x < 2), Si-Q alloys (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof; provided that Si is excluded), Sn, SnO2, Sn-R alloys (where R is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof; provided that Sn is excluded), etc. In addition, as materials capable of doping and undoping lithium, a mixture of at least one of the above examples and SiO2 can be used. Q and R can be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, etc.

[0124] In addition, the transition metal oxide can be vanadium oxide, lithium vanadium oxide, lithium titanium oxide, etc.

[0125] Preferably, the anode active material may include at least one compound selected from carbonaceous materials and silicon compounds. Here, the carbonaceous material is at least one material selected from natural graphite, artificial graphite, primary graphite, pyrolytic carbon, mesophase pitch, carbon fiber based on mesophase pitch, carbon microbeads, petroleum - or coal - based coke, soft carbon, and hard carbon as exemplified above. In addition, the silicon compound may be a compound containing Si as exemplified above, i.e., Si, Si - C composite material, SiOx (0 < x < 2), Si - Q alloy, mixtures thereof, or mixtures of at least one of these with SiO2.

[0126] Relative to the total weight of the electrode material composition, the anode active material may be included in an amount of 85 wt% to 98 wt%. Preferably, relative to the total weight of the anode material, the content of the anode active material may be 85 wt% to 97 wt%, or 87 wt% to 97 wt%, or 87 wt% to 95 wt%, or 90 wt% to 95 wt%.

[0127] In order to exhibit appropriate performance, preferably, the thickness of the electrode active material layer is adjusted within the range of 5 μm to 500 μm, or 5 μm to 450 μm, or 10 μm to 450 μm.

[0128] Preferably, the electrochemical device may be a lithium secondary battery including a lithium metal or a lithium metal alloy as an anode as described above.

[0129] Among all anode materials, lithium metal has the highest theoretical capacity (3,860 mAh / g) and the lowest electrochemical potential ( - 3.04 V relative to SHE), making it very promising as an anode material for next - generation high - energy - density batteries. Due to these electrochemical characteristics, lithium - metal - based secondary batteries are particularly suitable for next - generation applications that require both high power and long cycle life, such as electric vehicles, high - power storage systems, drones, and aerospace applications.

[0130] When using an alloy of lithium metal and other metals as the anode material, the stability of lithium deposition and stripping can be improved, and both mechanical stability and interfacial stability can be enhanced. For example, compared with pure lithium, such a lithium metal alloy can reduce dendrite formation and exhibits excellent performance in terms of cycle stability.

[0131] However, lithium secondary batteries using such lithium metal-based anodes are prone to short lifespan and safety issues due to dendrite formation and interfacial instability during repeated charging and discharging. Therefore, the gel polymer electrolyte-separator composite material according to the invention is very useful in battery systems in which lithium metal or its alloys are used as the anode. This composite material helps improve battery life and safety by suppressing lithium dendrite growth and simultaneously physically blocking them.

[0132] The electrochemical device can be used as a power source to enhance performance and safety in portable electronic devices such as mobile phones, laptops, tablets, mobile batteries, and digital cameras, as well as in transportation applications including electric vehicles, electric motorcycles, and personal mobile devices.

[0133] Beneficial effects

[0134] According to the present invention, a gel polymer electrolyte-separator composite material for an electrochemical device is provided, which can prevent the occurrence of internal short circuits caused by the growth of lithium dendrites. Attached Figure Description

[0135] Figure 1 This is a scanning electron microscope (SEM) image of the surface of the anode included in the lithium secondary battery according to Example 1.

[0136] Figure 2 This is a SEM image of the surface of the anode included in the lithium secondary battery according to Example 2.

[0137] Figure 3 This is a SEM image of the surface of the anode included in the lithium secondary battery according to Example 3.

[0138] Figure 4 This is a SEM image of the surface of the anode included in the lithium secondary battery according to Example 4.

[0139] Figure 5 This is a SEM image of the surface of the anode included in the lithium secondary battery according to Comparative Example 1.

[0140] Figure 6 This is a SEM image of the surface of the anode included in the lithium secondary battery according to Comparative Example 2.

[0141] Figure 7 This is a SEM image of the surface of the anode included in the lithium secondary battery according to Comparative Example 3. Detailed Implementation

[0142] The following describes specific embodiments of the present invention to illustrate its operation and effects in more detail. These embodiments are presented only as examples to assist in understanding the present invention. The scope of the present invention is not intended to be limited in any way by these embodiments, and it will be apparent to those skilled in the art that various modifications and changes can be made within the scope and spirit of the present invention.

[0143] Example 1

[0144] (1) Preparation of the separator

[0145] Prepare lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3; manufacturer Ganfeng Lithium; angular particles; D50 = 300 nm) as the first inorganic fine particles. Prepare boehmite (AlO(OH); manufacturer Boyaun; needle-like particles with an aspect ratio of 5.2; D50 = 155 nm) as the second inorganic fine particles. Prepare a dispersion liquid by dispersing 7 g of the first inorganic fine particles and 3 g of the second inorganic fine particles in N-methyl-2-pyrrolidone (NMP). Add poly(vinylidene fluoride-co-hexafluoropropylene) as a polymer binder to the dispersion liquid and mix uniformly using a homogenizer, thereby preparing a slurry with a solid content of 40%.

[0146] Apply the slurry (the temperature of the slurry is 25°C) to a porous polyethylene substrate with a thickness of 9 μm (manufacturer: Senior) using a double slit die. Form a porous coating with a thickness of 6 μm through a drying process of vaporizing the solvent at 80°C for 20 minutes. During the drying process, supply air with a wind speed of 2.0 m / s in a direction parallel to the coating surface.

[0147] As a result of the analysis, the porous coating is formed by a first porous coating with a thickness of about 4.5 μm in which the first inorganic fine particles occupy the main volume and a second porous coating with a thickness of about 1.5 μm in which the second inorganic fine particles occupy the main volume. A structure is formed in which the first porous coating and the second porous coating are stacked in sequence on the porous polyethylene substrate. The composition of the first porous coating and the second porous coating consists of a ratio of 90 wt% inorganic fine particles and 10 wt% polymer binder.

[0148] (2) Preparation of the composition for forming the gel polymer electrolyte

[0149] After dissolving lithium salt LiFSI in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7 to a concentration of 1 M, 10 parts by weight of tetraethylene glycol diacrylate as a polyfunctional acrylate compound and 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator are added based on 100 parts by weight of the total weight of the composition to prepare a composition for forming a gel polymer electrolyte.

[0150] (3) Preparation of anode components

[0151] An anode plate was prepared in which lithium metal was deposited on a Cu foil to a thickness of 2 μm. The anode plate was then punched to a size of 31 mm × 43 mm to fabricate the anode component.

[0152] (4) Preparation of cathode components

[0153] A uniformly dispersed slurry was prepared by placing a mixture of 94 wt% LiNiCoMnO2 (Ni:Co:Mn = 8:1:1) as the cathode active material, 3 wt% conductive carbon black (Super P; IMERYS Graphite & Carbon) as a conductive agent, and 3 wt% polyvinylidene fluoride as a binder into NMP. The slurry was coated onto one surface of an aluminum current collector, dried, and rolled to prepare a cathode plate on which layers of cathode active material were stacked. The cathode plate was then stamped into a size of 30 mm × 42 mm using a die-stamping machine to prepare the cathode component.

[0154] (5) Preparation of lithium secondary batteries

[0155] An electrode assembly was prepared by sequentially stacking the anode, separator, and cathode components and pressure laminating them at 90°C. The electrode assembly was then placed in a bag, and the composition to be used to form the gel polymer electrolyte was injected into it. Subsequently, the composition was polymerized in a chamber at 50°C for 5 hours to form the gel polymer electrolyte.

[0156] Example 2

[0157] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the separator was prepared by the following method.

[0158] Prepare lithium aluminum titanium phosphate (Li x Al y Ti z(PO4)3, where 0 < x < 2, 0 < y < 1, 0 < z < 3; manufacturer: Ganfeng Lithium; angular particles; D50 = 300 nm) as the first inorganic fine particles. A dispersion liquid is prepared by dispersing 10 g of the first inorganic fine particles in N-methyl-2-pyrrolidone (NMP). Poly(vinylidene fluoride-co-hexafluoropropylene) is added as a polymer binder to the dispersion liquid and uniformly mixed using a homogenizer to prepare a first slurry with a solid content of 40%.

[0159] Prepare boehmite (AlO(OH); manufacturer: Boyaun; acicular particles with an aspect ratio of 5.2; D50 = 155 nm) as the second inorganic fine particles. A dispersion liquid is prepared by dispersing 10 g of the second inorganic fine particles in N-methyl-2-pyrrolidone (NMP). Poly(vinylidene fluoride-co-hexafluoropropylene) is added as a polymer binder to the dispersion liquid and uniformly mixed using a homogenizer to prepare a second slurry with a solid content of 40%.

[0160] The first slurry (the temperature of the slurry is 25°C) is applied to a porous polyethylene substrate with a thickness of 9 μm (manufacturer: Senior) using a double slit die. A first porous coating with a thickness of 4.5 μm is formed through a drying process of vaporizing the solvent at 80°C for 15 minutes. The second slurry (the temperature of the slurry is 25°C) is applied to the first porous coating. A second porous coating with a thickness of 1.5 μm is formed through a drying process of vaporizing the solvent at 80°C for 15 minutes. During each drying process, air with a wind speed of 2.0 m / s is supplied in a direction parallel to the coating surface.

[0161] The composition of each of the first porous coating and the second porous coating consists of a ratio of 90 wt% of inorganic fine particles and 10 wt% of polymer binder.

[0162] Example 3

[0163] A lithium secondary battery is manufactured in the same manner as in Example 1, except that lithium titanium phosphate (Li x Ti y (PO4)3, where 0 < x < 2, 0 < y < 3; manufacturer: Tokyo Chemical Industry Co.; angular particles; D50 = 350 nm) is used instead of lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3) as the first inorganic fine particles.

[0164] Example 4 [[ID=~30]]

[0165] The lithium secondary battery was manufactured in the same manner as in Example 2, except that Al2O3 particles (manufacturer Boyaun; needle-shaped particles with an aspect ratio of 5.5; D50=160 nm) were used instead of boehmite (AlO(OH)) as the second inorganic fine particles.

[0166] Comparative Example 1

[0167] The lithium secondary battery was manufactured in the same manner as in Example 1, except that no second inorganic fine particles were added during the preparation of the separator. It was determined that the separator according to Comparative Example 1 formed a porous coating containing lithium aluminum titanium phosphate with a thickness of 6 μm on a porous polyethylene substrate.

[0168] Comparative Example 2

[0169] The lithium secondary battery was manufactured in the same manner as in Example 1, except that no first inorganic fine particles were added during the preparation of the separator. It was determined that the separator according to Comparative Example 2 had a porous coating containing boehmite with a thickness of 6 μm formed on a porous polyethylene substrate.

[0170] Comparative Example 3

[0171] The lithium secondary battery was manufactured in the same manner as in Example 1, except that during the manufacture of the lithium secondary battery, a porous polyethylene substrate (manufacturer: Senior) with a thickness of 9 μm and no porous coating was formed thereon was used as a separator.

[0172] Experimental Example 1

[0173] [1] A mixture of 7 g of lithium aluminum titanium phosphate (LATP) and 3 g of boehmite (AlO(OH)) used to prepare the separator of Example 1 was mixed with 10 g of the composition for forming the gel polymer electrolyte. The polymerization reaction of the composition was carried out in a chamber at 50°C for 5 hours to form the gel polymer electrolyte. It was then vacuum sealed and stored at 85°C for 48 hours, after which the escaping gases were analyzed by gas chromatography.

[0174] [2] The same experiment as [1] was performed, except that 10 g of lithium aluminum titanium phosphate was used alone as inorganic fine particles instead of the mixture of lithium aluminum titanium phosphate and boehmite.

[0175] [3] The same experiment as [1] was performed, except that 10 g of boehmite was used alone as inorganic fine particles instead of the mixture of lithium aluminum titanium phosphate and boehmite.

[0176] [Table 1]

[0177]

[0178] Referring to Table 1, the total gas production (Σ) was lowest when lithium aluminum titanium phosphate (LATP) was applied alone, while it was highest when boehmite (AlO(OH)) was applied alone. When a mixture of lithium aluminum titanium phosphate (LATP) and boehmite (AlO(OH)) was applied, a significant reduction in gas production was observed compared to the application of boehmite alone.

[0179] Experimental Example 2

[0180] For the lithium secondary batteries according to the examples and comparative examples, cycling was performed at 45°C. They were charged to 4.25 V using a constant current-constant voltage method at 0.1 C, followed by constant current discharge to 2.5 V, with a 20-minute resting period between charge and discharge. The formation capacity and charge-discharge capacity were then measured.

[0181] [Table 2]

[0182]

[0183] [Table 3]

[0184]

[0185] [Table 4]

[0186]

[0187] Referring to Tables 2 to 4, the coulombic efficiency (CE) is typically low in the first cycle due to side reactions of the polymerization initiator and increased ionic resistance, but it improves from the second cycle onwards. In the lithium secondary battery of the examples, dendrite growth is suppressed, thus exhibiting relatively superior cycling performance.

[0188] Experimental Example 3

[0189] After 50 cycles according to the method in Example 2, the anode surface of the lithium secondary battery was observed using a scanning electron microscope. The image is shown below. Figures 1 to 7 middle.

[0190] Reference Figures 1 to 4 It was determined that dendrite growth on the anode surface was suppressed in the lithium secondary batteries according to Examples 1 to 4.

[0191] In comparison, refer to Figures 5 to 7 It was determined that in the lithium secondary batteries according to Comparative Examples 1 to 3, a large number of dendrites grew on the surface of the anode or were in a state where they were easy to grow.

[0192] Although the invention has been described with reference to limited embodiments, it is not limited thereto, and various modifications and variations can be made by those skilled in the art within the scope of the inventive concept and the equivalents defined by the appended claims.

Claims

1. A gel polymer electrolyte-separator composite material for an electrochemical device, comprising: Porous polymer substrate, A plurality of porous coatings are sequentially stacked on the porous polymer substrate, and A gel polymer electrolyte impregnated in the porous polymer substrate and the porous coating; The plurality of porous coatings include: A porous coating comprising at least one type of first inorganic fine particles selected from the following: lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -based glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), and SiS2-based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), and A porous coating comprising at least one type of second inorganic fine particles selected from the following: SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, SiC, and BaTiO3.

2. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 1, wherein... The first inorganic fine particles are angular particles, granular particles, or spherical particles, and The second inorganic fine particles are needle-shaped particles with an aspect ratio in the range of 5 to 10.

3. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 1, comprising: The porous polymer substrate; A first porous coating stacked on the porous polymer substrate and containing the first inorganic fine particles; A second porous coating is stacked on the first porous coating and contains the second inorganic fine particles; as well as The gel polymer electrolyte is impregnated into the porous polymer substrate and the porous coating.

4. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 1, wherein... Each of the plurality of porous coatings comprises a polymer binder and inorganic fine particles dispersed in the polymer binder.

5. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 4, wherein... The polymer binder is a compound selected from at least one of the following: polyvinylidene fluoride, poly(vinylidene fluoride-copolymer-trichloroethylene), poly(vinylidene fluoride-copolymer-trifluorochloroethylene), poly(vinylidene fluoride-copolymer-trifluoroethylene), poly(vinylidene fluoride-copolymer-tetrafluoroethylene), poly(vinylidene fluoride-copolymer-hexafluoropropylene), spandex, butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, and polyvinyl acetate.

6. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 4, wherein... Each of the plurality of porous coatings comprises 1% to 90% by weight of the polymer binder and 10% to 99% by weight of the inorganic fine particles.

7. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 1, wherein... The porous polymer substrate comprises at least one polymer selected from the following: polyethylene, polypropylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene butylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyamide-imide, polyetherimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, and polyethylene naphthalate.

8. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 1, wherein... The gel polymer electrolyte comprises a lithium salt, a matrix gel polymer, and a non-aqueous organic solvent.

9. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 8, wherein... The lithium salt is selected from at least one of the following compounds: LiBF4, LiPF6, LiSbF6, LiAsF6, LiOH, LiOH·H2O, LiBOB, LiClO4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO2)2, LiN(CF3SO2)2, CF3SO3Li, LiC(CF3SO2)3, LiC4BO8, LiTFSI, LiFSI, LiCl, LiI, LiB(C2O4)2, and LiClO4.

10. The gel polymer electrolyte-separator composite material for an electrochemical device according to claim 8, wherein... The matrix gel polymer is a polymer that forms a three-dimensional gel network structure through the polymerization of polyfunctional acrylate compounds.

11. The gel polymer electrolyte-separator composite material for an electrochemical device according to claim 10, wherein... The polyfunctional acrylate compound is selected from at least one of the following compounds: tetraethylene glycol diacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyester dimethacrylate, trimethylolpropane trimethacrylate, ethoxylated bisphenol A dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, bis(trimethylolpropane) tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

12. The gel polymer electrolyte-separator composite material for electrochemical devices according to claim 8, wherein... The non-aqueous organic solvent is a compound selected from at least one of the following: methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone, dibutyl ether, tetrahydrofuran, cyclohexanone, benzene, fluorobenzene, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, butyl carbonate, ethanol, isopropanol, dimethylformamide, 1,3-dioxolane, dimethyl sulfone, sulfolane, and triethylene glycol dimethyl ether.

13. An electrochemical device comprising the gel polymer electrolyte-separator composite material according to claim 1.

14. The electrochemical device of claim 13, comprising a cathode, an anode, and the gel polymer electrolyte-separator composite material between the cathode and the anode.

15. The electrochemical device according to claim 14, wherein... The anode contains lithium metal or a lithium metal alloy.

16. The electrochemical device according to claim 13, wherein The electrochemical device is a lithium secondary battery.

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