Solid polymer electrolyte and all-solid-state battery comprising same

Abstract

The present invention relates to a solid polymer electrolyte, and an all-solid-state battery comprising same, the solid polymer electrolyte comprising: a lithium salt; a heterophasic matrix comprising a plurality of crystalline particles three-dimensionally connected and dispersed in a rubbery matrix; and inorganic oxide particles, wherein the solid polymer electrolyte has a tensile strain of at least 600% and a toughness of at least 1.5 MJ / ㎥.

Description

Solid polymer electrolyte and all-solid-state battery containing the same

[0001] The present invention relates to a solid polymer electrolyte and an all-solid-state battery including the same.

[0002] Lithium-ion batteries using liquid electrolytes have a structure where the anode and cathode are separated by a separator. Damage to the separator due to deformation or external impact can cause a short circuit, potentially leading to risks such as overheating or explosion. Consequently, interest in solid electrolytes, which can eliminate the risks of liquid electrolytes and ensure safety, is growing significantly.

[0003] Lithium secondary batteries using solid electrolytes offer increased safety, improved reliability by preventing electrolyte leakage, and the ease of manufacturing thin batteries. Furthermore, the use of lithium metal as the anode offers the advantage of improved energy density.

[0004] Solid electrolyte materials include sulfide, oxide, and polymer-based materials. Sulfide-based solid electrolytes have the disadvantage of high interfacial resistance, necessitating high-temperature and high-pressure compression, and are vulnerable to moisture. Furthermore, oxide-based solid electrolytes have the disadvantage of relatively low ionic conductivity. In contrast, polymer-based solid electrolytes are easy to manufacture and operate at room temperature, and extensive research is being conducted on them.

[0005] [Prior Art Literature]

[0006] [Patent Document]

[0007] Republic of Korea Patent Publication No. 10-2022-0026768

[0008] The present invention aims to provide a solid polymer electrolyte having both improved ductility and mechanical strength, which are complementary properties, and an all-solid-state battery including the same.

[0009] However, the technical problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0010] One embodiment of the present invention provides a solid polymer electrolyte comprising: a lithium salt; a heterogeneous matrix comprising a plurality of crystalline particles three-dimensionally connected and dispersed within a rubbery matrix; and inorganic oxide particles; and having a tensile strain of at least 600% and a toughness of at least 1.5 MJ / ㎥.

[0011] Another embodiment of the present invention provides a method for producing a solid polymer electrolyte, comprising the steps of: preparing a homogeneous solution comprising an acrylate monomer, a crosslinked polymer, a lithium salt, a nitrile compound, an initiator, and inorganic oxide particles; and subjecting the homogeneous solution to polymerization-induced phase separation.

[0012] Another embodiment of the present invention provides an all-solid-state battery including an electrolyte layer including the solid polymer electrolyte.

[0013] The solid polymer electrolyte according to the present invention has both very high elongation characteristics and improved mechanical properties, and therefore can realize very high life characteristics when applied to an all-solid-state battery.

[0014] In addition, the solid polymer electrolyte according to the present invention also has high ionic conductivity, and thus can achieve high efficiency when applied to an all-solid-state battery.

[0015] Furthermore, the solid polymer electrolyte according to the present invention has the advantage of being able to make close contact with the electrode interface due to its high ductility, and minimizing the degradation of battery performance due to dendrites that occur during battery operation due to its high mechanical properties.

[0016] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

[0017] Figure 1 shows an SEM image of a heterogeneous matrix in a solid polymer electrolyte manufactured according to an embodiment.

[0018] Figure 2 shows an SEM image of the surface of a solid polymer electrolyte (L5) manufactured according to Example 1.

[0019] Figure 3 shows an SEM image of the surface of a solid polymer electrolyte (L10) manufactured according to Example 2.

[0020] Figure 4 shows the ionic conductivity of solid polymer electrolytes according to Example 1, Example 2, and Comparative Example.

[0021] Figure 5 shows the results of tensile strain and toughness experiments of solid polymer electrolytes according to Example 1, Example 2, and Comparative Example.

[0022] Figure 6 shows the results of life evaluation of lithium metal batteries according to Example 1, Example 2, and Comparative Example.

[0023] Figure 7 shows the overall image, surface SEM image, and EDS image of the solid polymer electrolyte according to Example 2.

[0024] Figure 8 shows an overall image of the solid polymer electrolyte according to Reference Example 1 and SEM images of the upper surface and lower surface.

[0025] Figure 9 shows the results of evaluating the life of a lithium metal battery according to Example 2, Comparative Example, and cases in which other inorganic particles were applied.

[0026] Figure 10 shows the driving results of a lithium metal battery according to Example 1 and Reference Example 2.

[0027] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless specifically stated otherwise.

[0028] The present inventors have recognized that the low toughness of rubber-based solid polymer electrolytes applicable to all-solid-state batteries can cause problems such as unstable operation of the battery due to physical deformation when manufacturing the battery by introducing a direct coating process. Accordingly, the present inventors have completed the present invention as a result of various attempts to significantly improve high tensile strain and complementary mechanical properties. The present invention has the advantage of significantly improving both tensile strain and toughness, which are complementary properties of the solid polymer electrolyte, so that when the solid polymer electrolyte is applied to a battery, high operation stability and durability can be realized. Furthermore, the solid polymer electrolyte has the advantage of enabling close contact with the electrode interface due to its high ductility, and minimizing performance degradation caused by dendrites that occur during battery operation due to its high mechanical properties.

[0029] Hereinafter, the present invention will be described in detail.

[0030] One embodiment of the present invention provides a solid polymer electrolyte comprising: a lithium salt; a heterogeneous matrix comprising a plurality of crystalline particles three-dimensionally connected and dispersed within a rubbery matrix; and inorganic oxide particles; and having a tensile strain of at least 600% and a toughness of at least 1.5 MJ / ㎥.

[0031] The heterogeneous matrix may have a co-continuous structure with controlled domain size and connectivity of phase-separated structures through polymerization-induced phase-separation (PIPS). Specifically, the polymerization-induced phase-separation is a process that utilizes the phenomenon in which a phase-separated structure appears between two different phases as polymerization progresses in a homogeneous monomer solution. The heterogeneous matrix may have a rubber-like polymer matrix and a crystalline phase independently distributed, and the crystalline particles may be provided in a three-dimensionally connected form. Furthermore, the plurality of crystalline particles may be provided in a form captured in the rubber-like polymer matrix. Fig. 1 illustrates an SEM image of the heterogeneous matrix in a solid polymer electrolyte manufactured according to an embodiment. Referring to Fig. 1, it can be confirmed that in the heterogeneous matrix, crystalline particles are captured in the rubber-like matrix, and the plurality of crystalline particles are three-dimensionally connected. The crystalline particles may provide an ion transport path within the rubber-like matrix, thereby improving ion conductivity.

[0032] The inorganic oxide particles maintain the phase-separated structure of the rubber matrix and the crystalline particles, and may be dispersed within the heterogeneous matrix. Specifically, the inorganic oxide particles may be trapped within the rubber matrix, or may be partially exposed to the surface of the heterogeneous matrix (i.e., the surface of the solid polymer electrolyte). The inorganic oxide particles may improve the mechanical strength of the solid polymer electrolyte, and may also improve the flexibility of the solid polymer electrolyte.

[0033] According to one embodiment of the present invention, the rubber matrix may be an acrylate polymer matrix. Specifically, the rubber matrix may be formed by a polymerization reaction of a rubber solution containing an acrylate monomer, a crosslinked polymer, and an initiator.

[0034] According to one embodiment of the present invention, the crystalline particles may be a nitrile-based compound. Specifically, the nitrile-based compound may be at least one selected from the group consisting of succinonitrile, adiponitrile, and glutonitrile.

[0035] The above crystalline particles may be a complex of a nitrile compound and a lithium salt. The crystalline particles may provide an ion transfer path within the solid polymer electrolyte, thereby realizing high ion conductivity. Alternatively, the lithium salt may be included in a dissociated ion state in the internal space between the polymer chains of the rubber matrix, thereby improving the mechanical properties of the solid polymer electrolyte. Alternatively, at least a portion of the dissociated cations and / or anions from the lithium salt may exist in an ion state within the crystalline particles, thereby exhibiting mobility during charging / discharging of the battery.

[0036] The above lithium salts are CF3SO3Li, CH3SO3Li, LiAlCl4, LiAsF6, LiB 10 Cl 10, LiBF4, LiBOB, LiBr, LiCF3CO2, LiCF3SO3, LiCl, LiClO4, LiDFBP, LiDFOB, LiFOB, LiI, LiPO2F2, LiSbF6, LiSCN, LiTFSI, LiAsF6, LiC(CF3SO2)3, LiFSI, LiTFOP and LiPF6. The lithium salt may be included in the rubbery solution in an amount of 0.1 M to 3 M. When the lithium salt is included within the above amount range, it provides high ionic conductivity to the solid polymer electrolyte, and further, it can effectively form a stable interfacial resistance layer (e.g., LiF) on the electrode.

[0037] According to one embodiment of the present invention, the lithium salt may be a combination of LITFSI and LiDFOB. According to one embodiment of the present invention, the molar ratio of LITFSI and LiDFOB may be 9:1 to 7:3, more specifically 8:2.

[0038] According to one embodiment of the present invention, the content of the inorganic oxide particles may be 4.5 parts by weight to 17.5 parts by weight based on the total weight of the solid polymer electrolyte. Within the content range of the inorganic oxide particles, the solid polymer electrolyte can effectively realize an improvement in toughness as well as an improvement in elasticity. Specifically, when the content of the inorganic oxide particles exceeds the above range, the ionic conductivity and mechanical properties may decrease due to aggregation between excessive inorganic particles, which may cause a deterioration in battery performance. In addition, when the content of the inorganic oxide particles is less than the above range, the effect due to the addition of the inorganic oxide particles may hardly appear.

[0039] According to one embodiment of the present invention, the inorganic oxide particles may include at least one of Ta-LLZO (LLZTO) in which LLZO is doped with Ta element and Ga-LLZO in which Ga element is doped. Specifically, the inorganic oxide particles may be Ta-LLZO. The inorganic oxide particles are not reactive with lithium metal and can form a stable interface with a lithium negative electrode.

[0040] According to one embodiment of the present invention, the diameter of the inorganic oxide particles may be 10 nm to 1 μm. If the diameter is less than 10 nm, the mechanical strength of the solid polymer electrolyte may not be improved due to the addition of the inorganic oxide particles, and if it exceeds 1 μm, there is a problem that homogeneous dispersion may be difficult due to aggregation between the inorganic oxide particles and the movement of lithium ions within the solid polymer electrolyte may be hindered.

[0041] According to one embodiment of the present invention, the solid polymer electrolyte may further include at least one stabilizer selected from difluoroethylene carbonate (DFEC) and fluorine ethylene carbonate (FEC). The stabilizer may prevent side reactions between the crystalline particles and lithium metal, thereby improving the stability of the battery.

[0042] According to one embodiment of the present invention, the solid polymer electrolyte may have a tensile strain of at least 1,000% and a toughness of at least 2.0 MJ / ㎥. When mechanical strength and flexibility are simultaneously realized, as in the solid polymer electrolyte according to the present invention, there are advantages in that lithium dendrites growing during battery operation can be effectively suppressed and volume changes of lithium metal can be flexibly accommodated during charge and discharge. That is, the solid polymer electrolyte according to the present invention significantly improves the tensile strain of conventional solid polymer electrolytes that exhibit a tensile strain of up to 500%, while also improving the mechanical strength, thereby significantly improving the physical properties of previously reported solid polymer electrolytes.

[0043] Another embodiment of the present invention provides a method for producing the solid polymer electrolyte. Specifically, the method comprises the steps of: preparing a homogeneous solution comprising an acrylate monomer, a crosslinked polymer, a lithium salt, a nitrile compound, an initiator, and inorganic oxide particles; and subjecting the homogeneous solution to polymerization-induced phase separation.

[0044] The above polymerization-induced phase separation is as described above, and can be performed through a polymerization reaction of the homogeneous solution.

[0045] According to one embodiment of the present invention, the homogeneous solution can be prepared by mixing a rubber solution containing an acrylate monomer, a crosslinking polymer, and an initiator, and a crystalline solution containing a nitrile compound and a lithium salt.

[0046] According to one embodiment of the present invention, the acrylate monomer can be represented by the following chemical formula 1.

[0047]

[0048] In the above chemical formula 1, R1 may be hydrogen; a straight or branched chain alkyl group having C2 to C10; or an aryl group having C6 to C20.

[0049] The above "alkyl group" may refer to both unsubstituted alkyl groups and substituted alkyl groups. For example, an unsubstituted alkyl group refers to a monovalent straight-chain or branched-chain saturated hydrocarbon group composed only of carbon and hydrogen atoms, and includes, but is not limited to, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, an octyl group, a dodecyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and the like. Additionally, the substituted alkyl group may be an alkyl group substituted with at least one of halogen, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, and thiol.

[0050] The above "aryl group" refers to an organic group derived from an aromatic hydrocarbon by the removal of one hydrogen, and includes a single or fused ring system. Specific examples of the aryl group include, but are not limited to, a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a fluorenyl group, a phenanthryl group, a triphenylenyl group, a pyrenyl group, a perylenyl group, a chrysenyl group, a naphthacenyl group, a fluoranthenyl group, and the like.

[0051] The above alkyl group and aryl group may each be substituted or unsubstituted. The term "substitution" above means that a hydrogen atom bonded to a carbon atom of a compound is replaced with another substituent, and the position of substitution is not limited as long as it is the position where the hydrogen atom is substituted, i.e., a position where the substituent can be substituted. When two or more substitutions are made, the two or more substituents may be the same or different from each other.

[0052] According to one embodiment of the present invention, the crosslinked polymer may be an alkylene glycol poly(meth)acrylate. Specifically, the alkylene glycol poly(meth)acrylate may include at least one selected from the group consisting of polyethylene glycol diacrylate (PEGDA), glycerin diacrylate, glycerin triacrylate, unmodified or ethoxylated trimethylol triacrylate (TMPTA), hexanediol diacrylate, and triethylene glycol diacrylate.

[0053] According to one embodiment of the present invention, the crosslinked polymer may be included in the homogeneous solution in an amount of 0.1 mol% to 10 mol% of the acrylate monomer. When the crosslinked polymer is included in the homogeneous solution in the above content range, it is advantageous in securing excellent mechanical properties (strength and flexibility) of the solid polymer electrolyte.

[0054] According to one embodiment of the present invention, the lithium salt may be included in the homogeneous solution in an amount of 0.1 M to 3 M. When the lithium salt is included within the above amount range, it provides high ionic conductivity to the solid polymer electrolyte, and further, it can effectively form a stable interfacial resistance layer (e.g., LiF) on the electrode.

[0055] According to one embodiment of the present invention, the nitrile compound may be included in the homogeneous solution at a volume ratio (v / v) of 0.2 to 5.0 with respect to the acrylic monomer. Specifically, the nitrile compound may be included in the homogeneous solution at a volume ratio (v / v) of 0.5 to 1.5, or a volume ratio (v / v) of 0.7 to 1.2 with respect to the acrylic monomer. In addition, the nitrile compound may be included in the homogeneous solution at 1 wt% to 80 wt% with respect to the acrylic monomer. The nitrile compound is formed as crystalline particles in the solid polymer electrolyte, and when included in the homogeneous solution within the above content range, the ionic conductivity of the solid polymer electrolyte can be effectively improved.

[0056] According to one embodiment of the present invention, the initiator may be a thermal initiator or a photoinitiator. However, a photoinitiator capable of curing within a short period of time may be suitable to ensure that the inorganic oxide particles are uniformly distributed within the solid polymer electrolyte. In the case of a thermal initiator, as the curing time increases, precipitation of the inorganic oxide particles may occur within the composition, resulting in poor dispersibility.

[0057] According to one embodiment of the present invention, the photoinitiator may include various IRGACURE products commercially available from BASF Corporation. For example, the photoinitiator may include at least one selected from, but not limited to, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819), 2-hydroxyl-2-methyl-1-phenyl-1-propanone, methyl benzoyl formate, and hydroxycyclohexyl phenyl ketone (Igracure 184).

[0058] The photoinitiator may be included in the homogeneous solution in an amount of 0.5 to 5 parts by weight relative to the acrylate monomer.

[0059] According to one embodiment of the present invention, the inorganic oxide particles may be included in a content of 5 wt% to 20 wt% with respect to the homogeneous solution. If the content of the inorganic oxide particles is less than the above range, the mechanical strength of the solid polymer electrolyte due to the addition of the inorganic oxide particles may not be improved, and if it exceeds the above range, there is a problem that homogeneous dispersion may be difficult due to aggregation between the inorganic oxide particles.

[0060] According to one embodiment of the present invention, the homogeneous solution may further include at least one stabilizer selected from difluoroethylene carbonate (DFEC) and fluorine ethylene carbonate (FEC). The stabilizer may be included in an amount of 1 to 10% by volume with respect to the homogeneous solution.

[0061] According to one embodiment of the present invention, the method for producing the solid polymer electrolyte may further include a step of applying the homogeneous solution onto a support. The applying method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, spray coating, or solution casting. In addition, the support may be SUS (Stainless Steel), polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinylacetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film, but is not limited thereto, and any material that can serve as a support in the application and polymerization of the homogeneous solution may be applied without limitation.

[0062] Another embodiment of the present invention provides an all-solid-state battery comprising an electrolyte layer including the solid polymer electrolyte. Specifically, the all-solid-state battery comprises a negative electrode, a positive electrode, and a solid electrolyte provided between the negative electrode and the positive electrode, wherein the solid electrolyte is the solid polymer electrolyte according to the present invention described above.

[0063] The positive electrode included in the above all-solid-state battery includes a positive electrode active material layer, and the positive electrode active material layer may be formed on one surface of the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, a binder, and a conductive material.

[0064] The above-mentioned positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions, and may include at least one selected from the group consisting of non-limiting examples: a manganese (Mn)-based positive electrode material; an NMC (nickel manganese cobalt)-based positive electrode material; an LCO (lithium cobalt oxide)-based positive electrode material; an LNCAO (lithium nickel cobalt aluminum oxide)-based positive electrode material; an LNMCO (lithium nickel manganese cobalt oxide)-based positive electrode material; an LFP (lithium iron phosphate)-based positive electrode material; a fluorine-based positive electrode material; a sulfur selenium-based positive electrode material; a ceramic; a spinel-based positive electrode material; and an Olivier lattice inorganic material.

[0065] The above binder and conductive agent can be applied by selecting the type and content according to the purpose, as long as they are commonly used in the industry.

[0066] The above negative electrode includes a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of the negative electrode current collector.

[0067] The negative electrode active material may include a material capable of reversibly intercalating or deintercalating lithium, a material capable of reversibly forming a lithium-containing compound by reacting with lithium ions, lithium metal, or a lithium alloy.

[0068] The material capable of reversibly inserting or de-inserting lithium ions may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material capable of reversibly forming a lithium-containing compound by reacting with lithium ions may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of a metal selected from the group consisting of lithium (Li) and sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn). Specifically, the negative electrode active material may be lithium metal, and more specifically, may be in the form of a lithium metal thin film.

[0069] The above solid polymer electrolyte can be provided in close contact with a lithium negative electrode due to its high flexibility, and can effectively prevent short circuits caused by dendrites formed in a lithium metal battery.

[0070] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0071] [Example 1]

[0072] A rubbery solution containing butyl acrylate monomer, 1 mol% of PEGDA (molecular weight: 575 g / mol) relative to the butyl acrylate monomer, and 1 mol% of a photoinitiator (1-Hydroxycyclohexyl phenyl ketone) relative to the butyl acrylate monomer was prepared. Then, a crystalline solution containing butyl acrylate monomer, succinonitrile in a volume ratio of 1:1, and 1 M of a lithium salt (LiTFSI:LiDFOB = 8:2 molar ratio) relative to the total content of butyl acrylate and succinonitrile was prepared.

[0073] The above rubber solution and crystal solution were mixed, and about 5 vol% of fluorine ethylene carbonate (FEC) and 5 wt% of Ta-LLZO particles having an average particle size of 500 nm were added to the mixed solution, followed by stirring to prepare a homogeneous solution.

[0074] After applying the above homogeneous solution to the support, it was irradiated with UV light having a wavelength of 365 nm for about 5 minutes to produce a solid polymer electrolyte (L5).

[0075] In addition, a homogeneous solution was injected into a prepared coin cell (negative electrode: lithium metal with a thickness of 400 ㎛, positive electrode: NCM811, loading of about 2.5 mg / cm2), and then UV with a wavelength of 365 nm was irradiated for about 5 minutes, and the coin cell was assembled to manufacture a lithium metal battery.

[0076] Fig. 2 shows a SEM image of the surface of a solid polymer electrolyte (L5) manufactured according to Example 1. According to Fig. 2, it can be confirmed that Ta-LLZO particles are very homogeneously distributed in the solid polymer electrolyte.

[0077] [Example 2]

[0078] A solid polymer electrolyte (L10) and a lithium metal battery were manufactured in the same manner as in Example 1, except that the content of Ta-LLZO particles was changed to 10 wt% with respect to the mixed solution.

[0079] Fig. 3 shows a SEM image of the surface of a solid polymer electrolyte (L10) manufactured according to Example 2. According to Fig. 2, it can be confirmed that Ta-LLZO particles are very homogeneously distributed in the solid polymer electrolyte.

[0080] [Comparative example]

[0081] A solid polymer electrolyte (L0), a lithium metal battery, and a lithium metal battery were manufactured in the same manner as in Example 1 without adding Ta-LLZO particles.

[0082] Figure 4 shows the ionic conductivities of solid polymer electrolytes according to Examples 1, 2, and Comparative Examples. According to Figure 4, all of the solid polymer electrolytes according to Examples 1, 2, and Comparative Examples have ionic conductivities of ~10 -3 It can be confirmed that excellent room temperature ionic conductivity of S / cm level is maintained, and in particular, it can be confirmed that Examples 1 and 2 maintain ionic conductivity at a level equivalent to that of the comparative example despite the addition of metal oxide particles.

[0083] Fig. 5 shows the results of tensile strain and toughness experiments of solid polymer electrolytes according to Examples 1, 2, and Comparative Examples. According to Fig. 5, the strain of the Comparative Example was 400%, and the toughness was 0.28 MJ / ㎥. In contrast, in Examples 1 and 2 with added Ta-LLZO particles, the strain and toughness were 960% and 1250%, and the toughness was 2.07 MJ / ㎥ and 2.74 MJ / ㎥, respectively, showing a significant increase in both strain and toughness compared to the Comparative Example. It is believed that the Ta-LLZO particles, as an inorganic filler, act as a plasticizer in the solid polymer electrolyte, thereby further improving the mechanical properties of the rubber matrix.

[0084] Fig. 6 shows the results of life evaluations of lithium metal batteries according to Examples 1, 2, and Comparative Examples. The life evaluation in Fig. 6 was conducted at a driving voltage of 3.0 to 4.3 V and a driving speed of 0.5 C-rate (however, the C-rate was changed to 0.5 after 3 stabilization cycles at 0.2 C-rate). According to Fig. 6, in the case of the Comparative Example, it was confirmed that unstable coulombic efficiency was shown in the initial driving and a low discharge capacity of 74 mAh / g (50% capacity retention rate) was shown at 200 cycles. In contrast, Examples 1 and 2 with added Ta-LLZO particles exhibited high discharge capacities of 157 mAh / g (92% capacity retention) and 167 mAh / g (95% capacity retention) at 200 cycles, respectively, and excellent average coulombic efficiencies of 99.5% and 99.6%, and very stable cycle characteristics under a driving speed condition of 0.5 C-rate. Through this, it was confirmed that the solid polymer electrolyte according to the present invention with added Ta-LLZO particles improved the driving stability of a lithium metal battery.

[0085] Fig. 9 shows the results of the life evaluation of lithium metal batteries according to Example 2, Comparative Example, and cases where other inorganic particles were applied. The life evaluation in Fig. 9 was performed at a driving voltage of 3.0 to 4.3 V and a driving speed of 0.5 C-rate (however, the C-rate was changed to 0.5 after 3 cycles of stabilization at 0.2 C-rate), which were the same conditions as Fig. 6. Unlike Example 2 where Ta-LLZO was applied, when Nb-LLZO or LAGP inorganic particles were applied, it was confirmed that low discharge capacity and unstable Coulombic efficiency were shown from the initial operation, and low discharge capacities of 60 mAh / g and 32 mAh / g were shown at 200 cycles, respectively.

[0086] [Reference Example 1]

[0087] A solid polymer electrolyte was prepared in the same manner as in Example 1, except that the photoinitiator of the rubber solution was changed to a thermal initiator (AIBN, azobisisobutyronitrile) and heating was performed at about 70°C for about 2 hours instead of UV irradiation.

[0088] Fig. 7 shows an overall image, a surface SEM image, and an EDS image of a solid polymer electrolyte according to Example 2. According to Fig. 7, it was confirmed that the solid polymer electrolyte according to Example 2 was polymerized quickly through photopolymerization, and Ta-LLZO particles were uniformly dispersed in a homogeneous solution.

[0089] Fig. 8 shows an overall image of the solid polymer electrolyte according to Reference Example 1 and SEM images of the upper surface and the lower surface. According to Fig. 8, the solid polymer electrolyte according to Reference Example 1 undergoes polymerization for a relatively long time through thermal polymerization, so that Ta-LLZO particles in a homogeneous solution settle to the bottom, and the solid polymer electrolyte is separated into two layers. Ta-LLZO particles are not observed on the upper surface, but clumped Ta-LLZO particles are observed on the lower surface.

[0090] [Reference Example 2]

[0091] A solid polymer electrolyte and a lithium metal battery were manufactured in the same manner as in Example 1, except that only LiTFSI was applied (single lithium salt) instead of applying two types of lithium salts, LiTFSI and LiDFOB (dual lithium salt).

[0092] Fig. 10 shows the driving results of lithium metal batteries according to Example 1 and Reference Example 2. The life evaluation in Fig. 10 was performed at a driving voltage of 3.0 to 4.3 V and a driving speed of 0.5 C-rate (however, the C-rate was changed to 0.5 after 3 stabilization cycles at 0.2 C-rate), which were the same conditions as Fig. 6. Specifically, it was confirmed that Example 1, which applied dual lithium salts, implemented improved battery stability compared to Reference Example 2, which applied a single lithium salt. This is expected to be because the addition of LiDFOB to LiTFSI forms a stable interfacial resistance layer (e.g., LiF), thereby reducing the interfacial resistance with the lithium negative electrode.

Claims

1. A lithium salt; a heterogeneous matrix comprising a plurality of crystalline particles three-dimensionally connected and dispersed within a rubber matrix; and inorganic oxide particles; A solid polymer electrolyte having a tensile strain of at least 600% and a toughness of at least 1.5 MJ / ㎥.

2. In claim 1, A solid polymer electrolyte wherein the above rubber matrix is ​​an acrylate-based polymer matrix.

3. In claim 1, A solid polymer electrolyte wherein the above-mentioned crystal particles are nitrile-based compounds.

4. In claim 3, A solid polymer electrolyte, wherein the nitrile compound is at least one selected from the group consisting of succinonitrile, adiponitrile, and glutonitrile.

5. In claim 1, A solid polymer electrolyte wherein the lithium salt is a combination of LITFSI and LiDFOB.

6. In claim 5, A solid polymer electrolyte wherein the molar ratio of LITFSI and LiDFOB is 9:1 to 7:

3.

7. In claim 1, A solid polymer electrolyte, wherein the content of the inorganic oxide particles is 4.5 parts by weight to 17.5 parts by weight based on the total weight of the solid polymer electrolyte.

8. In claim 1, A solid polymer electrolyte, wherein the inorganic oxide particles comprise at least one of Ta-LLZO and Ga-LLZO.

9. In claim 1, A solid polymer electrolyte having a tensile strain of at least 1,000% and a toughness of at least 2.0 MJ / ㎥.

10. A step of preparing a homogeneous solution containing an acrylate monomer, a crosslinked polymer, a lithium salt, a nitrile compound, and an initiator; and A step of polymerizing and separating the homogeneous solution; A method for producing a solid polymer electrolyte according to claim 1.

11. In claim 10, A method for producing a solid polymer electrolyte, wherein the above initiator is a photoinitiator.

12. An all-solid-state battery comprising an electrolyte layer including a solid polymer electrolyte according to claim 1.

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