Lithium metal battery with low resistance performance and method for manufacturing the same

Abstract

According to one embodiment of the present invention, a lithium metal battery is provided, comprising a positive electrode including a positive electrode current collector and a positive electrode active material layer formed on one or both sides of the positive electrode current collector, a negative electrode including a lithium metal layer, a substrate and a separation membrane including an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP) formed on one or both sides of the substrate, wherein the oxide-based solid electrolyte layer of the separation membrane faces the lithium metal layer of the negative electrode, and an inorganic layer containing a reduced product of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority rights under Korean Patent Application No. 10-2023-0174492 dated December 5, 2023, and Korean Patent Application No. 10-2024-0178245 dated December 4, 2024, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

[0002] The present invention relates to a lithium metal battery having low resistance performance and a method for manufacturing the same. [Background technology]

[0003] The rapid increase in fossil fuel use has led to a growing demand for alternative and clean energy sources, and one of the most actively researched areas in this field is electrochemical power generation and energy storage.

[0004] Currently, a prime example of an electrochemical element that utilizes such electrochemical energy is the secondary battery, and its range of applications is steadily expanding.

[0005] Recently, with the technological development and increasing demand for portable devices such as portable computers, mobile phones, and cameras, the demand for secondary batteries as an energy source has increased rapidly. Among these, lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, have been the subject of much research and have been commercialized and are widely used.

[0006] Furthermore, as concern for environmental issues grows, much research is being conducted on electric vehicles and hybrid electric vehicles that can replace vehicles that use fossil fuels such as gasoline and diesel vehicles, which are one of the main causes of air pollution. Nickel-metal hydride secondary batteries are mainly used as the power source for such electric vehicles and hybrid electric vehicles, but research using lithium secondary batteries with high energy density and discharge voltage is actively progressing and some are already at the commercialization stage.

[0007] Generally, lithium secondary batteries have a structure in which an electrode assembly consisting of a positive electrode, a negative electrode, and a porous separation membrane is impregnated with a non-aqueous electrolyte. Generally, the positive electrode is manufactured by coating aluminum foil with a positive electrode mixture containing a positive electrode active material, and the negative electrode is manufactured by coating copper foil with a negative electrode mixture containing a negative electrode active material.

[0008] Typically, the positive electrode active material is a lithium transition metal oxide, and the negative electrode active material is a carbon-based material.

[0009] However, recently, lithium metal batteries that use lithium metal itself, which exhibits high energy density, as the negative electrode active material have been commercialized.

[0010] At this time, the lithium metal used as the negative electrode has a density of (0.54 g / cm³). 3 Due to its low saturation and extremely low standard reduction potential (-3.045V SHE), it is the most noteworthy material for anodes in high-energy-density batteries. Furthermore, despite the problems arising from its extremely high chemical reactivity, the need for its use as anode in lithium metal batteries continues to be raised due to the ever-increasing demand for the development of high-energy-density secondary batteries driven by the sustained increase and rapid development of mobile communications and portable electronic devices.

[0011] However, lithium metal has excessively high reactivity, leading to safety issues such as the formation of lithium dendrites during charging and discharging. Furthermore, to improve the output characteristics, one of the most important performance aspects of lithium secondary batteries, the formation of SEI, which accounts for the largest portion of cell resistance, remains a challenge.

[0012] Therefore, there is a pressing need to develop lithium metal batteries that solve these problems, improve output characteristics, and alleviate safety concerns. [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The present invention aims to ensure the safety of lithium metal batteries while improving their output characteristics. [Means for solving the problem]

[0014] According to one embodiment of the present invention, A positive electrode comprising a positive electrode current collector and a positive electrode active material layer formed on one or both sides of the positive electrode current collector, A negative electrode containing a lithium metal layer, The material comprises a substrate and a separation membrane formed on one or both sides of the substrate, which includes an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP). The oxide-based solid electrolyte layer of the separation membrane faces the lithium metal layer of the negative electrode, A lithium metal battery is provided in which an inorganic layer containing the reduced product of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0015] Here, the inorganic layer may be included in the form of filling some or all of the voids in the oxide-based solid electrolyte layer, forming a separate layer at the interface between the oxide-based solid electrolyte layer and the lithium metal layer, or in all of these forms.

[0016] In this case, more specifically, the inorganic layer may be formed to fill the voids in the oxide-based solid electrolyte layer by 10% to 100% of the total volume of the voids, forming a separate layer with a thickness of 1 nm to 10 nm.

[0017] The reduced product of LATP, which is one component of the inorganic layer, may include lithium-LATP, which is formed by a spontaneous lithiumization reaction represented by the following reaction formula 1.

[0018] [Reaction Equation 1] Li 1.3 Al 0.3 Ti 1.7 (PO4)3->Li3Al 0.3 Ti 1.7 (PO4)3 Taking it a step further, the lithium metal battery further comprises a lithium non-aqueous electrolyte, The inorganic layer may further contain the reduced product of LATP and an SEI substance, the SEI substance being one or more substances selected from the group consisting of LiF, Li2CO3, and Li2O.

[0019] More specifically, the inorganic layer may be composed of a reduced form of LATP and an SEI substance.

[0020] On the other hand, the oxide-based solid electrolyte layer may be formed on both sides of the substrate.

[0021] The substrate may be a polyolefin substrate, and the oxide-based solid electrolyte layer may be composed of an oxide-based solid electrolyte containing lithium aluminum titanium phosphate (LATP) and a binder.

[0022] Here, the oxide-based solid electrolyte layer may be formed on one surface of the substrate with a thickness of 0.1 μm to 20 μm.

[0023] Furthermore, the positive electrode active material layer may contain a lithium transition metal oxide represented by the following chemical formula 1 as the positive electrode active material.

[0024] [Chemical Formula 1] Li 1+x Ni a Co b Mn c M 1-(a+b+c) O2 In the above formula, M is one or more selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, 0 ≦ x ≦ 0.5, 0 < a < 1, 0 < b < 1, 0 < c < 1.

[0025] On the other hand, according to still another embodiment of the present invention, there is provided a method for manufacturing the lithium metal battery, A lithium metal battery including an electrode assembly in which a separator film having an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP) formed on one or both surfaces is interposed between a negative electrode and a positive electrode such that the oxide-based solid electrolyte contacts the lithium metal layer, and the method includes a step of activating the lithium metal battery, and an inorganic layer containing a reduced product of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0026] At this time, the lithium metal battery can be manufactured by incorporating the electrode assembly and a lithium non-aqueous electrolyte into a battery case.

[0027] The inorganic layer further includes a reduced product of the LATP and a SEI substance, and the SEI substance may be one or more substances selected from the group consisting of LiF, Li2CO3, and Li2O. <00​​​​​​​​​​​​ [Figure 2] This is a photograph of the separation membrane surface obtained by disassembling a Li / Li symmetric cell manufactured according to Experimental Example 1. [Figure 3] These are the XRD patterns of the separation membrane before and after activation of the Li / Li symmetric cell produced by Experimental Example 2. [Figure 4] This is a graph of XPS spectra analysis of the Li metal surface after activation and cycling of the Li / Li symmetric cell fabricated according to Experimental Example 3. [Figure 5] This is a graph evaluating the Li plating / stripping of Li / Li symmetric cells manufactured using Experimental Example 4. [Figure 6] This is a potentiostatic electrochemical impedance spectroscopy (PEIS) evaluation graph of a coin-half cell manufactured according to Experimental Example 5. [Figure 7] This is a voltage graph per unit time of the OCV of a coin-half cell from Experimental Example 6. [Figure 8] This is a voltage graph per unit time of the OCV of a coin-half cell from Experimental Example 6. [Modes for carrying out the invention]

[0030] Hereafter, terms and words used in this specification and in the claims shall not be interpreted in a manner limited to their ordinary or dictionary meanings, but in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention, and shall be interpreted in a manner and concept consistent with the technical idea of ​​the present invention.

[0031] Unless otherwise defined, all terms used herein (including technical and scientific terms) should be used in a sense that is commonly understood by a person of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly defined otherwise.

[0032] The terms used herein are for illustrative purposes only and are not intended to limit the invention. In this specification, the singular form includes the plural form unless otherwise specified. The terms “comprises” and / or “comprising” as used in this specification do not preclude the presence or addition of one or more other components beyond those mentioned.

[0033] On the other hand, as used in the specification, "consists of" and / or "consisting of" means that, in addition to the components mentioned, other components are present only in trace amounts, i.e., in trace amounts.

[0034] A lithium metal battery according to one embodiment of the present invention is A positive electrode comprising a positive electrode current collector and a positive electrode active material layer formed on one or both sides of the positive electrode current collector, A negative electrode containing a lithium metal layer, The material comprises a substrate and a separation membrane formed on one or both sides of the substrate, which includes an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP). The oxide-based solid electrolyte layer of the separation membrane faces the lithium metal layer of the negative electrode, A feature is that an inorganic layer containing the reduced product of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0035] positive electrode The positive electrode may have a structure that includes a positive electrode current collector and a positive electrode active material layer formed on one or both sides of the positive electrode current collector.

[0036] Here, the positive electrode current collector can be any material that is conductive without inducing a chemical change in the battery, and is not particularly limited. For example, the current collector can be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc.

[0037] The positive electrode current collector can have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to enhance adhesion to the positive electrode active material layer. For example, it can be used in a variety of forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics.

[0038] The positive electrode active material layer comprises a positive electrode active material and may optionally include conductive materials, binders, and other additives.

[0039] The positive electrode active material is not limited to any compound capable of reversible intercalation and deintercalation of lithium, but specifically, it may include lithium metal oxides containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the positive electrode active material may include lithium transition metal oxides represented by the following chemical formula 1.

[0040] [Chemical formula 1] Li 1+x Ni a Co b Mn c M 1-(a+b+c) O2 In the above formula, M is one or more elements selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo. 0 ≤ x ≤ 0.5, 0 <a<1、0<b<1、0<c<1である。

[0041] In addition, as the positive electrode active material, lithium-metal oxides include lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., Li 1+x’ Ni 1-Y Mn Y O2 (where -0.5 ≤ x’ ≤ 0.5, 0 < Y < 1), Li 1+x’’ Mn 2-Z Ni Z O4 (where -0.5 ≤ x’’ ≤ 0.5, 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., Li 1+x’’’ Ni 1-Y1 Co Y1 O2 (where -0.5 ≤ x’’’ ≤ 0.5, 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., Li 1+x’’’’ Co 1-Y2 Mn Y2 O2 (where -0.5 ≤ x’’’’ ≤ 0.5, 0 < Y2 < 1), Li 1+x’’’’’ Mn 2-Z1 Co Z1 O4 (where -0.5 ≤ x’’’’’ ≤ 0.5, 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li 1+a1 (Ni p Co q Mn[[ID=3,7]] r )O2 (where -o.5 ≤ a1 ≤ 0.5, 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li 1+a2 (Ni p1 Co q1 Mn r1 )O4 (where -0.5 ≤ a2 ≤ 0.5, 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li 1+a3 (Ni p2 Co q2 Mn r2 M s2)O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and a3, p2, q2, r2, and s2 are atomic fractions of independent elements, respectively, -0.5 ≦ a3 ≦ 0.5, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.), lithium iron phosphate (e.g., Li 1+a4 Fe 1-p3 M p3 (PO 4-b4 )X b4 (where M is one or more selected from Al, Mg, and Ti, X is one or more selected from F, S, and N, -0.5 ≦ a4 ≦ 0.5, 0 ≦ p3 ≦ 0.5, 0 ≦ b4 ≦ 0.1), etc., and any one or two or more of these compounds may be included.

[0042] Among these, in terms of enhancing the capacity characteristics and stability of the battery, the lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), or lithium nickel manganese cobalt aluminum oxide (e.g., Li(Ni 0.86 Co<​​​​It may be lithium iron phosphorus oxide (e.g., LiFePO4), or a mixture of one or more of these, and Li(Ni) is a lithium transition metal oxide represented by the chemical formula 1. 0.86 Co 0.05 Mn 0.07 Al 0.02 ) May contain O2.

[0043] The positive electrode active material may be present in an amount of 60 to 98% by weight, preferably 80 to 98% by weight, and more preferably 90 to 98% by weight, based on the total weight of the positive electrode active material layer.

[0044] The conductive material is a component for further improving the conductivity of the positive electrode active material, and such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, carbon powders such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders such as natural graphite, artificial graphite, or graphite with a highly developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0045] The conductive material may be present in an amount of 0.1 to 20% by weight, more specifically 0.5 to 10% by weight, or more specifically 0.5 to 5% by weight, based on the total weight of the positive electrode active material layer.

[0046] The binder is a component that helps to bond the conductive material, the positive electrode active material, and the positive electrode current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0047] Typically, the binder may be present in an amount of 0.5 to 20% by weight, more specifically 0.5 to 10% by weight, or more specifically 0.5 to 5% by weight, based on the total weight of the positive electrode active material layer.

[0048] Furthermore, the aforementioned other additives may include, for example, fillers as components that suppress expansion. The fillers are not particularly limited as long as they can suppress the expansion of the electrodes without inducing chemical changes in the battery, and for example, olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fibers and carbon fibers; etc. can be used.

[0049] negative electrode The negative electrode has a structure including a lithium metal layer. More specifically, it may consist of a lithium metal layer, or it may have a structure in which a lithium metal layer is formed on one or both sides of a separate negative electrode current collector.

[0050] The negative electrode, which consists of the lithium metal layer, may be formed from lithium metal itself without a separate negative electrode current collector. In this case, the lithium metal layer can have a sufficient thickness, for example, 10 μm to 300 μm.

[0051] On the other hand, a structure that includes a separate current collector in addition to the lithium metal layer used as the negative electrode active material layer is even more preferable in terms of stability and structural integrity.

[0052] Here, the negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treatments with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used.

[0053] The negative electrode current collector can typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the negative electrode current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in a variety of forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics.

[0054] The lithium metal layer may be formed by physically bonding, rolling, or vapor-depositing lithium metal onto the negative electrode current collector. The vapor deposition method can be either electro-depositing or chemical vapor deposition.

[0055] Here, the lithium metal layer may include an alloy that contains, in addition to lithium (Li), a metal selected from the group consisting of nickel (Ni), tin (Sn), copper (Cu), and indium (In).

[0056] Here, the lithium metal layer can be formed to a total thickness of 10 to 300 μm so that it can function sufficiently as a negative electrode active material.

[0057] separation membrane The separation membrane has a structure comprising a substrate and an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP) formed on one or both sides of the substrate.

[0058] Here, the substrate can be used without any special limitations as long as it is one that is normally used as a separation membrane substrate in lithium metal batteries, and is particularly preferred if it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture absorption capacity.

[0059] For example, the substrate is a polyolefin-based substrate such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, and a porous polymer film or a laminated structure of two or more layers thereof can be used. Alternatively, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used as the separation membrane, but more specifically, a polyolefin substrate may also be used.

[0060] An oxide-based solid electrolyte layer is formed on one or both sides of the substrate.

[0061] In this case, the oxide-based solid electrolyte layer may contain an oxide-based solid electrolyte containing lithium aluminum titanium phosphate (LATP) and a binder.

[0062] The oxide-based solid electrolyte may further include, in addition to lithium aluminum titanium phosphate, one or more lithium metal oxides or lithium metal phosphoroxides selected from Nasicon-type solid electrolytes, Lisicon-type solid electrolytes, Garnet-type solid electrolytes, Perovskite-type solid electrolytes, and LiPON-type solid electrolytes. More specifically, it may further include one or more compounds selected from the group consisting of LAGP (lithium aluminum germanium phosphate) compounds, LLZO (lithium lanthanum zirconium oxide) compounds, LLZTO (lithium lanthanum zirconium tantalum oxide) compounds, LLTO (lithium lanthanum titanium oxide) compounds, LSTP (lithium silicon titanium phosphate) compounds, and LGPO (lithium germanium phosphate) compounds.

[0063] Such oxide-based solid electrolytes may be present in an amount of 70% to 99% by weight, or more specifically, 80% to 99% by weight, based on the total weight of the oxide-based solid electrolyte layer.

[0064] If the content is excessively low beyond the aforementioned range, it may not be possible to obtain a sufficient reduced product as intended by this application. Conversely, if the content is excessively high, the amount of binder linking them together may be too low, potentially weakening the adhesive strength between these particles and degrading their mechanical properties, which is undesirable.

[0065] The average diameter (D50) of the oxide-based solid electrolyte particles may be 50 nanometers to 10 micrometers, more specifically 50 nanometers to 5 micrometers, or even more specifically 50 nanometers to 1 micrometer.

[0066] If the size is excessively small beyond the aforementioned range, aggregation between particles may occur due to decreased dispersibility. Conversely, if it is excessively large, the oxide-based solid electrolyte will form large pores, which is detrimental in terms of resistance. In other words, when the aforementioned range is satisfied, lithium-ion conductivity can be increased, resistance can be reduced, and improved secondary battery performance can be achieved.

[0067] The average diameter (D50) mentioned above represents the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. D50 can be measured, for example, using the laser diffraction method. This laser diffraction method generally allows for the measurement of particle sizes ranging from the submicron region to several millimeters, and provides highly reproducible and high-resolution results.

[0068] On the other hand, the binder, which is another component of the oxide-based solid electrolyte layer, is not limited as long as it does not undergo side reactions with the electrolyte, but in particular, a binder with the lowest possible glass transition temperature (Tg) can be used, preferably in the range of -200 to 200°C.

[0069] Furthermore, while the binder does not necessarily need to have ion-conducting ability, it is even more preferable to use a polymer that does have ion-conducting ability.

[0070] Therefore, it is preferable that the binder has as high a dielectric constant as possible, because the degree of dissociation of salts in an electrolyte actually depends on the dielectric constant of the electrolyte solvent. The higher the dielectric constant of the polymer, the better the degree of dissociation of salts in the electrolyte can be. The dielectric constant of the polymer can be 1 or higher, more specifically in the range of 1.0 to 100 (measurement frequency = 1 kHz), and is particularly preferably 10 or higher.

[0071] In addition to the functions described above, the binder may have the characteristic of gelling upon impregnation with liquid electrolyte, exhibiting a high degree of electrolyte impregnation. In fact, if the binder is a polymer with excellent electrolyte impregnation, the electrolyte injected after battery assembly permeates the polymer, and the polymer holding the absorbed electrolyte has electrolyte ion conductivity. Therefore, the solubility index should be as high as possible, between 15 and 45 MPa. 1 / 2 A polymer is preferred, and the pressure is 15-25 MPa. 1 / 2 and 30-45 MPa 1 / 2 A range of 15 MPa is even more preferable. 1 / 2 Less than and 45 MPa 1 / 2 If the amount exceeds the limit, it becomes difficult for the material to be impregnated (swelled) by the liquid electrolyte used in normal batteries.

[0072] Examples of such binders include polyvinylidene fluoride co-hexafluoropropylene, polyvinylidene fluoride cotrichloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. It may be one or more selected from the group consisting of propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and polyvinyl alcohol.

[0073] More specifically, the oxide-based solid electrolyte layer of the present invention aims to form a reduced product of LATP by direct contact between the LATP contained in the oxide-based solid electrolyte layer and the lithium metal layer of the negative electrode. Therefore, it is preferable that the oxide-based solid electrolyte containing LATP and a binder are composed of these two components, and it is preferable that no other substances are included, as these may hinder the reduction of LATP.

[0074] Therefore, the binder may be present in an amount of 1% to 30% by weight, more specifically 1% to 20% by weight, based on the total weight of the oxide-based solid electrolyte layer.

[0075] Such an oxide-based solid electrolyte layer may be formed on one or both sides of the substrate, but it is more preferable to form it on both sides, as this exhibits even better overpotential reduction. Of course, if the oxide-based solid electrolyte layer is formed on only one side, the electrode assembly must be manufactured so that the oxide-based solid electrolyte layer faces the lithium metal layer of the negative electrode in order to form the LATP reduction product intended in this application.

[0076] In this case, the oxide-based solid electrolyte layer may be formed on one surface of the substrate to a thickness of 0.1 μm to 20 μm.

[0077] If the concentration is excessively thin beyond the aforementioned range, the intended effect of LATP reduction may not be fully achieved, and if it is excessively thick, the resistance may actually increase, which is undesirable.

[0078] On the other hand, the total thickness of the separation membrane, which includes the substrate and the oxide-based solid electrolyte layer, may be 5 micrometers to 50 micrometers, more specifically 5 micrometers to 40 micrometers, and more specifically 10 micrometers to 30 micrometers. When the thickness of the separation membrane satisfies the above range, it is possible to effectively prevent short circuits between the positive and negative electrodes while minimizing the resistance of the lithium metal battery. As a result, it is possible to prevent a decrease in the energy density of the lithium secondary battery and improve its lifespan characteristics.

[0079] On the other hand, whether the oxide-based solid electrolyte layer is formed on one surface or on both surfaces, the oxide-based solid electrolyte layer faces the lithium metal layer of the negative electrode, thereby forming the reduced product of LATP at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0080] Here, the reduced product of LATP may include lithified-LATP, which is formed by a spontaneous lithiation reaction represented by the following reaction formula 1, upon contact between LATP and the lithium metal layer.

[0081] [Reaction Equation 1] Li 1.3 Al 0.3 Ti 1.7 (PO4)3->Li3Al 0.3 Ti 1.7 (PO4)3 Furthermore, the lithium metal battery may further contain a lithium non-aqueous electrolyte, thereby allowing for the inclusion of SEI material on the surface of the lithium metal layer of the negative electrode. Therefore, in the lithium metal battery of the present invention, the inorganic layer formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer may contain both the reduced product of LATP and the SEI material, and more specifically, may be composed of the reduced product of LATP and the SEI material.

[0082] In this case, the SEI substance may be one or more substances selected from the group consisting of LiF, Li2CO3, and Li2O, and the inorganic layer may contain one or more substances selected from the group consisting of lithium-LATP, LiF, Li2CO3, and Li2O.

[0083] Since such an inorganic layer is formed by contact between the LATP and the lithium metal, and by the reaction between the lithium metal and the lithium non-aqueous electrolyte due to the activation of the lithium metal battery, it can be mainly formed on the surface of the lithium metal layer.

[0084] More specifically, the reduced product of LATP can be formed by the reaction of the oxide-based solid electrolyte layer and the metal of the lithium metal layer of the negative electrode, and the SEI material is formed by the reaction of lithium ions generated by the activation process with a lithium non-aqueous electrolyte.

[0085] The lithium non-aqueous electrolyte can contain a lithium salt and a non-aqueous organic solvent.

[0086] At this time, the lithium salt is used as a medium for transmitting ions in the lithium secondary battery. The lithium salt, for example, contains Li as a cation, and as an anion, it includes F, Cl, Br, I, NO3, N(CN)2, BF4, ClO4, BCl, AlCl4, AlO2, PF6, CF3SO3, CH3CO2, CF3CO2, AsF6, SbF6, CH3SO3, (CF3CF2SO2)2N, (CF3SO2)2N, (FSO2)2N, BF2C2O4, BC4O8, PF4C2O4, PF2C4O8, (CF3)2PF4, (CF3)3PF3, (CF3)4PF2, (CF3)5PF, (CF3)6P, C4F9SO3, CF3CF2SO3, CF3CF2(CF3)2CO, (CF3SO2)2CH, CF3(CF2)7SO3, + including at least any one selected from the group consisting of F, - Cl, - Br, - I, - NO3, - N(CN)2, - BF4, - ClO4, - B, 10 Cl, 10 - AlCl4, - AlO2, - PF6, - CF3SO3, - CH3CO2, - CF3CO2, - AsF6, - SbF6, - CH3SO3, - (CF3CF2SO2)2N, - (CF3SO2)2N, - (FSO2)2N, - ]BF2C2O4, - BC4O8, - PF4C2O4, - PF2C4O8, - (CF3)2PF4, - (CF3)3PF3, - (CF3)4PF2, - (CF3)5PF, - (CF3)6P, - C4F9SO3, - CF3CF2SO3, - CF3CF2(CF3)2CO, - (CF3SO2)2CH, - CF3(CF2)7SO3, - and SCN. - At least any one selected from the group is included.

[0087] Specifically, the lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB 10 Cl 10 It may include a single substance or a mixture of two or more substances selected from the group consisting of LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, lithium bis(trifluoromethanesulfonyl)imide (LiFSI: Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), lithium bis(perfluoroethanesulfonyl)imide (LiBETI: lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI: lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2), but it is preferable to include Li(N(SO2CF3)2 in terms of superior stability.

[0088] In addition to these, lithium salts commonly used as electrolytes in lithium secondary batteries can be used without restriction.

[0089] The lithium salt can be appropriately changed within a range of normal use, but in order to obtain the optimal effect of forming a corrosion-preventive coating on the electrode surface, it may be included in the electrolyte at a concentration of 0.5 M to 3 M, more specifically, 1 M to 2.5 M, and more specifically, 1 M to 2 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, the viscosity of the electrolyte is appropriate, and the electrolyte impregnation can be improved.

[0090] The aforementioned non-aqueous organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions during the charging and discharging process of the lithium secondary battery and exhibit the desired properties together with the additive. For example, carbonate-based organic solvents, ether-based organic solvents, or ester-based organic solvents can be used individually or in combination of two or more types. In particular, carbonate-based organic solvents can be used.

[0091] The carbonate-based organic solvent among the aforementioned organic solvents may include at least one of cyclic carbonate-based organic solvents and linear carbonate-based organic solvents. Specifically, the cyclic carbonate-based organic solvent may include at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate (FEC). Specifically, it may include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively lower melting point compared to ethylene carbonate.

[0092] Furthermore, the linear carbonate-based organic solvent is a solvent having low viscosity and low dielectric constant, and may contain at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and more specifically, it may contain dimethyl carbonate.

[0093] The ether-based organic solvent may be one selected from the group consisting of ethylene glycol dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether, or a mixture of two or more of these, but is not limited thereto.

[0094] The ester-based organic solvent mentioned above is at least one selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents.

[0095] The linear ester-based organic solvent can typically be any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, or a mixture of two or more of these, but is not limited to these.

[0096] The cyclic ester organic solvent may, but is not limited to, one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more of these.

[0097] Among the ester solvents mentioned above, cyclic carbonate compounds are preferable because they are high-viscosity organic solvents with high dielectric constants that effectively dissociate lithium salts in electrolytes. Furthermore, when such cyclic carbonate compounds are mixed with low-viscosity, low-dielectric-constant linear carbonate compounds and linear ester compounds, such as dimethyl carbonate and diethyl carbonate, in appropriate ratios, it is possible to create an electrolyte with high electrical conductivity, making it even more preferable to use such a mixture.

[0098] Furthermore, the lithium non-aqueous electrolyte may further contain functional additives, which may be included to prevent the induction of anode collapse in high-power environments, and to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and swelling improvement effects during high-temperature storage.

[0099] Specifically, the functional additive may include, as a representative example, one or more functional additives selected from the group consisting of sultone compounds, sulfite compounds, sulfone compounds, sulfate compounds, halogen-substituted carbonate compounds, nitrile compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and lithium salt compounds. More specifically, halogen-substituted carbonate compounds and / or lithium salt compounds may contain halogen elements, and more specifically, carbonate compounds substituted with a fluoro group (F) and / or lithium salt compounds containing a fluoro group (F) may be included.

[0100] The sultone compound mentioned above includes at least one compound selected from the group consisting of 1,3-propanesultone (PS), 1,4-butanesultone, ethensultone, 1,3-propensultone (PRS), 1,4-butensultone, and 1-methyl-1,3-propensultone, and may be present in an amount of 0.3% to 5% by weight, specifically 1% to 5% by weight, based on the total weight of the electrolyte. If the content of the sultone compound in the electrolyte exceeds 5% by weight, an excessively thick film may be formed on the electrode surface, leading to increased resistance and output degradation. The resistance due to the excess additive may also increase, potentially degrading the output characteristics.

[0101] The sulfite compound mentioned above includes one or more compounds selected from the group consisting of ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethylpropylene sulfite, 4,5-diethylpropylene sulfite, 4,6-dimethylpropylene sulfite, 4,6-diethylpropylene sulfite, and 1,3-butylene glycol sulfite, and may be present in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0102] The sulfone compound may be one or more compounds selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone, and may be present in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0103] The aforementioned sulfate compound may be ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS), and may be present in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0104] Furthermore, the halogen-substituted carbonate compound may be fluoroethylene carbonate (FEC), and may be present in an amount of 10% by weight or less, more specifically 5% by weight or less, based on the total weight of the electrolyte. If the content of the halogen-substituted carbonate compound in the electrolyte exceeds 10% by weight, the cell swelling performance may deteriorate.

[0105] Furthermore, the nitrile compounds include at least one compound selected from the group consisting of succinonitrile, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0106] The cyclic carbonate compound may be vinylene carbonate (VC) or vinylethylene carbonate, and may be present in an amount of 3% by weight or less based on the total weight of the electrolyte. If the content of the cyclic carbonate compound in the electrolyte exceeds 3% by weight, the cell swelling suppression performance may deteriorate.

[0107] The phosphate compound mentioned above may be one or more compounds selected from the group consisting of lithium difluoro(bisoxalato) phosphate, lithium difluorophosphate, tetramethyltrimethylsilyl phosphate, trimethylsilyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphate, and may be present in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0108] The borate compound mentioned above may include lithium oxalyl difluoroborate, and may be present in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0109] The lithium salt compound is a compound different from the lithium salt contained in the lithium non-aqueous electrolyte, and includes one or more compounds selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalate borate (LiB(C2O4)2), lithium bis(trifluoromethanesulfonyl)imide (LiFSI: Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), and LiBF4, and may be lithium bis(trifluoromethanesulfonyl)imide (LiFSI: Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), and may be present in an amount of 3% by weight or less, more specifically 1% by weight or less, based on the total weight of the electrolyte.

[0110] The functional additives may be a mixture of two or more types, and may be present in an amount of 20% by weight or less, specifically 0.1% to 10% by weight, based on the total weight of the lithium non-aqueous electrolyte. If the content of the functional additives exceeds 20% by weight, excessive side reactions may occur in the lithium non-aqueous electrolyte during battery charging and discharging. In particular, they may not decompose sufficiently at high temperatures and remain unreacted or precipitated in the lithium non-aqueous electrolyte at room temperature. This may cause side reactions that reduce the lifespan or resistance characteristics of the lithium metal battery.

[0111] More specifically, for the formation of the SEI substance of the present application, and in particular for the inclusion of LiF, the lithium non-aqueous electrolyte may include, as functional additives, halogen-substituted carbonate compounds and / or lithium salt compounds, for example, fluoroethylene carbonate (FEC) and / or lithium bis(trifluoromethanesulfonyl)imide (LiFSI: Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2).

[0112] On the other hand, since the oxide-based solid electrolyte layer contains voids inside, the inorganic layer may be formed in a manner that fills some or all of the voids in the oxide-based solid electrolyte layer, or it may be formed as a separate layer at the interface between the oxide-based solid electrolyte layer and the lithium metal layer, or it may be in all of these forms, that is, it may be formed by being included in the voids or forming a layer.

[0113] When the inorganic layer fills the voids in the oxide-based solid electrolyte layer, it can fill 10% to 100% of the total volume of the voids, more specifically 30% to 100% of the total volume, and more specifically 50% to 80% of the total volume.

[0114] Furthermore, if the inorganic layer is formed as a separate layer at the interface between the oxide-based solid electrolyte layer and the lithium metal layer, the thickness of this layer may be 1 nm to 100 nm, more specifically 2 nm to 80 nm, or even more specifically 3 nm to 50 nm.

[0115] To more clearly explain the formation of such an inorganic layer, Figure 1 shows a schematic diagram of the interface where the separation membrane and the negative electrode of the present invention come into contact.

[0116] Referring to Figure 1, the separation membrane 110 has a structure comprising a substrate 111 and an oxide-based solid electrolyte layer 112 containing LATP formed on one surface of the substrate 111. When such an oxide-based solid electrolyte layer 112 comes into contact with the lithium metal layer 121 of the negative electrode, it forms an inorganic layer 130 containing lithified-LATP, which is obtained by the spontaneous reaction of LATP and Li. At this time, the inorganic layer 130 is formed on the surface of the lithium metal layer 121, either by filling the gaps in the oxide-based solid electrolyte layer 112 or by being formed as a separate layer with a thickness t.

[0117] Manufacturing method for lithium metal batteries On the other hand, according to yet another embodiment of the present invention, A method for manufacturing a lithium metal battery is provided, comprising the steps of manufacturing a lithium metal battery including an electrode assembly in which a separation membrane having an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP) formed on one or both sides is interposed between a negative electrode and a positive electrode such that the oxide-based solid electrolyte is in contact with a lithium metal layer, and activating the lithium metal battery, wherein an inorganic layer containing a reduced product of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0118] In other words, the positive electrode, negative electrode, and separation membrane are manufactured separately, and the electrode assembly is manufactured by laminating them so that the oxide-based solid electrolyte of the separation membrane is in contact with the lithium metal layer of the negative electrode.

[0119] Thereafter, the electrode assembly and the lithium non-aqueous electrolyte are incorporated into a battery case to manufacture a lithium metal battery.

[0120] In such lithium metal batteries, the LATP in the oxide-based solid electrolyte layer and the lithium in the lithium metal layer react to spontaneously form a reduced product of LATP, i.e., lithified LATP.

[0121] However, the lithium metal battery undergoes an activation process after manufacturing, and as a result of the reaction between the electrolyte and the lithium metal layer during activation, an inorganic layer containing a reduced form of LATP is formed on the surface of the lithium metal layer. That is, an inorganic layer containing a reduced form of LATP, along with, for example, one or more SEI substances selected from the group consisting of LiF, Li2CO3, and Li2O.

[0122] At this time, the basement-free layer is as described above.

[0123] On the other hand, such an activation process may include aging at room temperature for 12 to 36 hours, during which time the reduction of LATP can occur spontaneously.

[0124] Furthermore, the activation step may include a process of charging the lithium metal battery once or more times, and SEI material can be formed by such a process.

[0125] When an inorganic layer is formed on the surface of the lithium metal layer through such an activation process, a denser interface can be formed between the separation membrane and the negative electrode, reducing the driving force required for Li ions to permeate the SEI, thereby improving the output characteristics.

[0126] On the other hand, the lithium non-aqueous electrolyte incorporated together with the electrode assembly in the manufacture of the lithium metal battery is as described above.

[0127] The following description will refer to an example to demonstrate the improved effects of a lithium secondary battery according to one embodiment of the present invention.

[0128] <Example 1> A separation membrane was manufactured by forming an oxide-based solid electrolyte layer (thickness: 20 μm) on one surface of a polyolefin substrate (thickness: 9 micrometers).

[0129] Here, the oxide-based solid electrolyte layer is Li 1.3 Al 0.3 Ti 1.7 (PO4)3: An electrolyte slurry was prepared by mixing an acrylic copolymer (CSB130, Toyoink Co., Ltd.) in a weight-based ratio of 95:5 and dispersing it in acetone. This slurry was then coated onto one surface of a polyolefin substrate and dried to produce the product.

[0130] <Example 2> A separation membrane was manufactured in the same manner as in Example 1, except that the oxide-based solid electrolyte layer was formed on both sides of the polyolefin substrate (thickness: 2 μm each).

[0131] <Comparative Example 1> A separation membrane was manufactured by forming an organic-inorganic mixed layer (thickness: 20 μm) on one surface of a polyolefin substrate (thickness: 15 micrometers).

[0132] Here, the organic-inorganic mixed layer was produced by mixing Al2O3:PVdF in a weight-based ratio of 95:5, dispersing the resulting organic-inorganic slurry in NMP, coating one surface of the polyolefin substrate with the slurry, and drying it.

[0133] <Comparative Example 2> A polyolefin substrate (thickness: 35 micrometers) was prepared.

[0134] <Experimental Example 1> An electrode assembly was manufactured by interposing the separation membrane produced in Example 1 and Comparative Example 1 as the positive electrode between two lithium foils (thickness: 300 μm) and as the negative electrode between two lithium foils (thickness: 300 μm), and by facing the oxide-based solid electrolyte layer or organic-inorganic mixed layer toward the lithium foil of the negative electrode. LiPF6 was dissolved in a non-aqueous organic solvent having a composition of ethylene carbonate (EC):ethyl methyl carbonate (EMC) = 30:70 (volume ratio) to a concentration of 1.0 M, and the mixture contained 0.5 wt% fluoroethylene carbonate (FEC), lithium bis(trifluoromethanesulfonyl)imide (LiFSI: Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), vinylene carbonate (VC), 0.5 wt% 1,3-propanesultone (PS), and ethylene sulfate (Ethylene Li / Li symmetric cells were prepared by injecting an electrolyte containing 1.0 wt% sulfate (Esa) and 0.2 wt% 1,3-propensultone (PRS) as additives.

[0135] After leaving the Li / Li symmetric cell at 25°C for 24 hours, it was disassembled, and the surface of the separation membrane was observed. A photograph of this observation is shown in Figure 2 below.

[0136] Referring to Figure 2, it can be seen that in the case of the separation membrane according to Example 1, reduced substances are formed on the surface of the oxide-based solid electrolyte layer, whereas in the case of the separation membrane of Comparative Example 2 using alumina, no substances are formed on the surface.

[0137] <Experimental Example 2> Using the separation membrane of Example 1, a Li / Li symmetric cell manufactured in the same manner as in Experimental Example 1 was charged at 25°C with a constant current of 0.33C until it reached 4.35V, then aged at 25°C for 24 hours, then at 60°C for 20 hours, and finally activated by complete discharge with a constant current of 0.33C.

[0138] XRD analysis was performed on the separation film coating layer before and after the activation process of the Li / Li symmetric cell, and the results are shown in Figure 3.

[0139] Before activation, no peak for the lithium-LATP composition was detected. However, after activation, a general peak broadening occurred, and it can be confirmed that a peak for the lithium-LATP composition, which is presumed to be a reduced form of LATP, was detected.

[0140] <Experimental Example 3> In Experimental Example 2, the Li metal surface facing the separation film coating layer was analyzed after activation. The Li / Li symmetric cell was then charged again at 25°C with a constant current-voltage of 0.33C and 4.35V, and discharged with a constant current of 0.33C 70 times. The Li metal surface was then analyzed twice, and the results are shown in Figure 4 below.

[0141] The analysis of the Li metal surface was performed using XPS spectroscopy, with the following instruments: Nexsa G2 ESCA system, Thermo Fisher Scientific.

[0142] -X-ray source: Monochromated Al Ka(1486.6eV) - X-ray spot size: 400 μm - Sputtering gun: Monatomic Ar (Energy: 1000eV, current: low, raster width: 2mm) -Operation mode: Constant Analyzer Energy mode - Survey scan: Pass energy 200 eV, Energy step 1 eV - Narrow scan: Scanned mode, pass energy 50 eV, energy step 0.1 eV

[0143] Referring to Figure 4, we can see that a significant metal oxide peak is observed, and the LiF peak is clearly visible. This is due to the reaction between LATP and the lithium metal layer, Li + The coordination number decreases, Li + This is because the electron bias towards is alleviated, making the reduction of fluoro groups (F) contained in lithium non-aqueous electrolytes relatively easier.

[0144] <Experimental Example 4> Using the separation membranes of Examples 1 and 2 and Comparative Example 2, a Li / Li symmetric cell similar to that in Experimental Example 1 was fabricated.

[0145] For the aforementioned Li / Li symmetric cell, 1 mA / cm 2 Li plating / stripping evaluation was performed for 20 hours by alternately applying oxidation and reduction currents for 1 hour, and the results are shown in Figure 5 below.

[0146] Referring to Figure 5, it can be seen that the Li / Li symmetric cells using the separation membranes of Examples 1 and 2 exhibit overpotential reduction behavior compared to the Li / Li symmetric cell using the separation membrane of Comparative Example 2.

[0147] <Experimental Example 5> Using the separation membranes of Example 1 and Comparative Example 1, a Li / Li symmetric cell similar to that in Experimental Example 1 was fabricated.

[0148] For the aforementioned Li / Li symmetric cells, PEIS evaluation was performed to show the current signals obtained by applying AC voltages in the frequency range from 1 MHz to 50 mHz under charge states of SOC 10, 30, 50, 70, and 90, respectively. The results are shown in Figure 6 below.

[0149] Referring to Figure 6, it can be confirmed that the separation membrane of Example 1, which is coated with an oxide-based solid electrolyte layer, exhibits a smaller Seim circle size and lower resistance compared to the separation membrane of Comparative Example 1, which is coated with alumina over the entire SOC region.

[0150] <Example 3> A 15-micrometer thick aluminum (Al) metal thin film is prepared as the positive electrode current collector, and Li(Ni) is used as the positive electrode active material on one surface of the aluminum metal thin film. 0.86 Co 0.05 Mn 0.07 Al 0.02 A cathode slurry was prepared by dispersing O2 (carbon nanotubes as a conductive material) and PVDF (PVDF as a binder) in an NMP solvent in a weight ratio of 96:1:3. The cathode slurry was then coated to a thickness of 60 micrometers, dried, and rolled to produce the cathode.

[0151] An electrode assembly was manufactured by interposing the separation membrane of Example 1 between the positive electrode and a lithium foil (thickness: 300 μm) as the negative electrode, with the oxide-based solid electrolyte layer facing the negative electrode. This electrode assembly was then placed in a case along with an electrolyte prepared by dissolving LiPF6 to a concentration of 1.0 M in a non-aqueous organic solvent having a composition of ethylene carbonate (EC):ethyl methyl carbonate (EMC) = 30:70 (volume ratio), to produce a coin half-cell.

[0152] <Comparative Example 3> A coin half-cell was manufactured in the same manner as in Example 3, except that the oxide-based solid electrolyte layer was interposed so as to face the positive electrode when the electrode assembly was manufactured.

[0153] <Experimental Example 6> For each of the coin half-cells produced in Example 3 and Comparative Example 3, the open-circuit voltage (OCV) was measured after being left at 25°C for 24 hours, and the results are shown in Figures 7 and 8 below.

[0154] Referring to Figures 7 and 8, it can be confirmed that the OCV fluctuation behavior due to the spontaneous reduction reaction of LATP is observed only in Figure 7 of Example 3.

[0155] Anyone with ordinary skill in the art to which this invention belongs will be able to make various applications and modifications within the scope of this invention based on the above. [Industrial applicability]

[0156] The lithium metal battery according to the present invention ensures safety by forming an oxide-based solid electrolyte layer containing LATP on a separation membrane substrate. At the same time, by directly contacting such an oxide-based solid electrolyte layer containing LATP with a lithium metal layer and forming a reduced form of LATP at the interface between them, the driving force required for Li ions to permeate the SEI can be reduced by forming a dense interface between the negative electrode containing the lithium metal layer and the separation membrane. This has the effect of lowering the resistance caused by the formation of SEI and improving the output characteristics of the lithium metal battery.

Claims

1. A positive electrode comprising a positive electrode current collector and a positive electrode active material layer formed on one or both sides of the positive electrode current collector, A negative electrode containing a lithium metal layer, The material comprises a substrate and a separation membrane formed on one or both sides of the substrate, which includes an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP). The oxide-based solid electrolyte layer of the separation membrane faces the lithium metal layer of the negative electrode, A lithium metal battery in which an inorganic layer containing the reduced form of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

2. The lithium metal battery according to claim 1, wherein the inorganic layer is included in any form that fills some or all of the voids in the oxide-based solid electrolyte layer, or forms a separate layer at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

3. The lithium metal battery according to claim 2, wherein the inorganic layer is formed to fill the voids in the oxide-based solid electrolyte layer by 10% to 100% by volume, based on the total volume of the voids, and to form a separate layer with a thickness of 1 nm to 100 nm.

4. The lithium metal battery according to claim 1, wherein the reduced product of LATP includes lithified-LATP formed by a spontaneous lithiation reaction represented by the following reaction formula 1: [Reaction Equation 1] Li １．３ Al ０．３ Today １．７ (PO ４ ) ３ ->L+ ３ Al ０．３ Today １．７ (PO ４ ) ３

5. The lithium metal battery further comprises a lithium non-aqueous electrolyte, The inorganic layer further comprises the reduced product of LATP and an SEI substance, wherein the SEI substance is LiF, Li ２ CO ３ , and Li ２ The lithium metal battery according to claim 1, wherein the material is one or more substances selected from the group consisting of O.

6. The lithium metal battery according to claim 5, wherein the inorganic layer is composed of a reduced product of LATP and an SEI substance.

7. The lithium metal battery according to claim 1, wherein the oxide-based solid electrolyte layer is formed on both sides of the substrate.

8. The lithium metal battery according to claim 1, wherein the substrate is a polyolefin substrate.

9. The lithium metal battery according to claim 1, wherein the oxide-based solid electrolyte layer is composed of an oxide-based solid electrolyte containing lithium aluminum titanium phosphate (LATP) and a binder.

10. The lithium metal battery according to claim 1, wherein the oxide-based solid electrolyte layer is formed on one surface of the substrate with a thickness of 0.1 μm to 20 μm.

11. The lithium metal battery according to claim 1, wherein the positive electrode active material layer contains a lithium transition metal oxide represented by the following chemical formula 1 as the positive electrode active material: [Chemical formula 1] Li １＋ｘ Ni ａ Co ｂ Mn ｃ M １－（ａ＋ｂ＋ｃ） O ２ In the above formula, M is one or more elements selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo. 0 ≤ x ≤ 0.5, 0 < a < 1, 0 < b < 1, 0 < c < 1.

12. A method for manufacturing a lithium metal battery as described in claim 1, A method for manufacturing a lithium metal battery, comprising the steps of: manufacturing a lithium metal battery including an electrode assembly in which a separation membrane having an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP) formed on one or both sides is interposed between a negative electrode and a positive electrode such that the oxide-based solid electrolyte layer is in contact with a lithium metal layer; and activating the lithium metal battery, wherein an inorganic layer containing a reduced form of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

13. The method for manufacturing a lithium metal battery according to claim 12, wherein the lithium metal battery is manufactured by incorporating the electrode assembly and a lithium non-aqueous electrolyte into a battery case.

14. The inorganic layer further comprises the reduced product of LATP and an SEI substance, wherein the SEI substance is LiF, Li ２ CO ３ , and Li ２ A method for producing a lithium metal battery according to claim 12, wherein the substance is one or more substances selected from the group consisting of O.

15. The method for manufacturing a lithium metal battery according to claim 12, wherein the activation step includes a step of aging at room temperature for 12 to 36 hours.

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