Lithium metal battery having low-resistance performance and manufacturing method therefor

Abstract

According to an embodiment of the present invention, a lithium metal battery and a manufacturing method therefor are provided. The lithium metal battery comprises: a positive electrode comprising a positive electrode current collector and a positive electrode active material layer formed on one surface or both surfaces of the positive electrode current collector; a negative electrode comprising a lithium metal layer; and a separator comprising a substrate and an oxide-based solid electrolyte layer formed on one surface or both surfaces of the substrate and containing lithium aluminum titanium phosphate (LATP), wherein the oxide-based solid electrolyte layer of the separator 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

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

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0174492, filed December 5, 2023, and Korean Patent Application No. 10-2024-0178245, filed December 4, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a lithium metal battery having low resistance performance and a method for manufacturing the same.

[0004] Due to the rapid increase in fossil fuel use, the demand for alternative and clean energy is increasing, and as part of this, the most actively researched field is the field of power generation and storage using electrochemistry.

[0005] A representative example of an electrochemical device that currently utilizes this type of electrochemical energy is the secondary battery, and its application area is gradually expanding.

[0006] Recently, with the increase in technological development and demand for portable devices such as portable computers, mobile phones, and cameras, the demand for secondary batteries as an energy source has been rapidly increasing. Among them, much research has been conducted on lithium secondary batteries that exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, and they have also been commercialized and widely used.

[0007] Furthermore, with growing concern about environmental issues, research is being conducted on electric vehicles and hybrid electric vehicles as alternatives to fossil fuel-powered vehicles like gasoline and diesel, a major source of air pollution. While nickel-metal hydride secondary batteries are primarily used as power sources for these electric and hybrid electric vehicles, research into the use of lithium secondary batteries, which boast high energy density and discharge voltage, is actively underway, and some are nearing commercialization.

[0008] Typically, lithium secondary batteries are structured to have an electrode assembly comprising a positive electrode, a negative electrode, and a porous separator, each impregnated with a non-aqueous electrolyte. Furthermore, the positive electrode is typically manufactured by coating a positive electrode mixture containing a positive electrode active material onto aluminum foil, while the negative electrode is typically manufactured by coating a negative electrode mixture containing a negative electrode active material onto copper foil.

[0009] Typically, the positive electrode active material is a lithium transition metal oxide, and the negative electrode active material is a carbon-based material.

[0010] However, recently, lithium metal batteries that use lithium metal itself, which exhibits high energy density, as the negative electrode active material have been commercialized.

[0011] At this time, the lithium metal used as the negative electrode has a density (0.54 g / cm 3 ) and a very low standard reduction potential (-3.045 V SHE), making it the most sought-after material as an anode material for high-energy-density batteries. In addition, despite the problems arising from its very high chemical activity, the need for the development of high-energy-density secondary batteries continues to grow due to the continuous increase and rapid development of mobile communication and portable electronic devices, and thus the need for the use of anodes for lithium metal batteries continues to arise.

[0012] However, lithium metal has safety issues such as its high activity and the formation of lithium dendrites during charge and discharge. Furthermore, the formation of SEI, which accounts for the largest portion of cell resistance, remains a challenge in order to improve output characteristics, which is one of the most important performances in lithium secondary batteries.

[0013] Therefore, there is an urgent need to develop lithium metal batteries that solve these problems, improve output characteristics, and also improve safety issues.

[0014] The purpose of the present invention is to improve the output characteristics while ensuring the safety of a lithium metal battery.

[0015] According to one embodiment of the present invention,

[0016] A cathode comprising a cathode current collector and a cathode active material layer formed on one or both sides of the cathode current collector,

[0017] A cathode comprising a lithium metal layer, and

[0018] A separator comprising a substrate and an oxide-based solid electrolyte layer formed on one or both sides of the substrate and including lithium aluminum titanium phosphate (LATP);

[0019] The oxide-based solid electrolyte layer of the separator faces the lithium metal layer of the negative electrode,

[0020] A lithium metal battery is provided in which an inorganic layer including a reduced product of the LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0021] Here, the inorganic layer may be included in the form of filling part or all of the pores of 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 the form of all of these.

[0022] At this time, in detail, the inorganic layer may be formed to fill the pores of the oxide-based solid electrolyte layer by 10 to 100 volume% based on the total pore volume, and to form a separate layer having a thickness of 1 nm to 10 nm.

[0023] The reduced product of the LATP, which is one component of the above-mentioned inorganic layer, may include lithiated-LATP formed by a spontaneous lithiation reaction represented by the following reaction formula 1.

[0024] [Reaction Formula 1]

[0025] Li 1.3 Al 0.3 Ti 1.7 (PO4)3-> Li3Al 0.3 Ti 1.7 (PO4)3

[0026] Furthermore, the lithium metal battery further comprises a lithium non-aqueous electrolyte,

[0027] The above-mentioned inorganic layer may further include the LATP reduction product and SEI material, and the SEI material may be at least one material selected from the group consisting of LiF, Li2CO3, and Li2O.

[0028] Moreover, in detail, the above-mentioned inorganic layer may be composed of a LATP reduction product and an SEI material.

[0029] Meanwhile, the oxide-based solid electrolyte layer can be formed on both sides of the substrate.

[0030] The above substrate may be a polyolefin substrate, and the oxide-based solid electrolyte layer may be composed of an oxide-based solid electrolyte including lithium aluminum titanium phosphate (LATP) and a binder.

[0031] Here, the oxide-based solid electrolyte layer may be formed on one side of the substrate to a thickness of 0.1 µm to 20 µm.

[0032] In addition, furthermore, the positive electrode active material layer may include a lithium transition metal oxide represented by the following chemical formula 1 as a positive electrode active material.

[0033] [Chemical Formula 1]

[0034] Li 1+x Ni a Co b Mn c M 1-(a+b+c) O2

[0035] In the above formula,

[0036] M is at least one selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo,

[0037] 0≤x≤0.5, 0 <a<1, 0<b<1, 0<c<1이다.

[0038] Meanwhile, according to another embodiment of the present invention, as a method for manufacturing the lithium metal battery,

[0039] A method for manufacturing a lithium metal battery is provided, comprising: manufacturing a lithium metal battery including an electrode assembly in which a separator having an oxide-based solid electrolyte layer including lithium aluminum titanium phosphate (LATP) formed on one or both sides thereof is interposed between a negative electrode and an positive electrode such that the oxide-based solid electrolyte is in contact with the lithium metal layer; and including a process for activating the lithium metal battery, such that an inorganic layer including a reduced product of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0040] At this time, the lithium metal battery can be manufactured by embedding the electrode assembly and the lithium non-aqueous electrolyte in a battery case.

[0041] The above-mentioned inorganic layer further includes a reduced product of the LATP and an SEI material, and the SEI material may be at least one material selected from the group consisting of LiF, Li2CO3, and Li2O.

[0042] Here, the activating process may include a room temperature aging process for 12 to 36 hours.

[0043] Figure 1 is a schematic diagram showing the formation of an inorganic layer at the interface between a cathode and a separator according to one embodiment of the present invention.

[0044] Figure 2 is a photograph of the surface of a separator obtained by disassembling Li / Li symmetric cells manufactured according to Experimental Example 1.

[0045] Figure 3 shows XRD patterns of the separator before and after activation of a Li / Li symmetric cell manufactured according to Experimental Example 2.

[0046] Figure 4 is a graph of XPS spectra analysis of the Li metal surface after activation and cycling of a Li / Li symmetric cell manufactured according to Experimental Example 3.

[0047] Figure 5 is a graph showing the Li plating / stripping evaluation of Li / Li symmetric cells manufactured according to Experimental Example 4.

[0048] Figure 5 is a graph showing the PEIS (Potentiostatic Electrochemical Impedance Spectroscopy) evaluation of coin-half cells manufactured according to Experimental Example 5.

[0049] Figures 7 and 8 are hourly voltage graphs of OCV of coin-half cells according to Experimental Example 6.

[0050] Hereinafter, the terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, and should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0051] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0052] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0053] Meanwhile, the terms “consists of” and / or “consisting of” used in the specification mean that other components are not included in amounts greater than trace amounts, i.e., impurities, other than the mentioned components.

[0054]

[0055] A lithium metal battery according to one embodiment of the present invention,

[0056] A cathode comprising a cathode current collector and a cathode active material layer formed on one or both sides of the cathode current collector,

[0057] A cathode comprising a lithium metal layer, and

[0058] A separator comprising a substrate and an oxide-based solid electrolyte layer formed on one or both sides of the substrate and including lithium aluminum titanium phosphate (LATP);

[0059] The oxide-based solid electrolyte layer of the separator faces the lithium metal layer of the negative electrode,

[0060] It is characterized in that an inorganic layer containing a reduced product of the LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0061]

[0062] anode

[0063] The positive electrode may have a structure 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.

[0064] Here, the positive electrode current collector may be any conductive material that does not induce chemical changes in the battery, and is not particularly limited. For example, the current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like.

[0065] The positive electrode current collector (121) may have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to increase adhesion to the positive electrode active material layer. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0066] The above positive electrode active material layer includes a positive electrode active material and may include a conductive agent, a binder, and other additives as needed.

[0067] The above positive electrode active material is not limited to a compound capable of reversible intercalation and deintercalation of lithium, but specifically may include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the positive electrode active material may include a lithium transition metal oxide represented by the following chemical formula 1.

[0068] [Chemical Formula 1]

[0069] Li 1+x Ni a Cob Mn c M 1-(a+b+c) O2

[0070] In the above formula,

[0071] M is at least one selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo,

[0072] 0≤x≤0.5, 0 <a<1, 0<b<1, 0<c<1이다.

[0073] In addition, the positive electrode active material is a lithium metal oxide, such as a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (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 oxides (e.g., Li 1+x’’’ Ni 1-Y1 Co Y1 O2(here, -0.5≤x'''≤0.5, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, Li 1+x’’’’ Co 1-Y2 Mn Y2 O2(here, -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 oxides (e.g., Li 1+a1 (Ni p Co q Mn r )O2(where, -0.5≤a1≤0.5, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li 1+a2 (Ni p1Co q1 Mn r1 )O4 (wherein, -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) oxide (e.g., Li 1+a3 (Ni p2 Co q2 Mn r2 M s2 )O2 (wherein, 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, p2+q2+r2+s2=1), etc.), lithium iron phosphate (e.g., Li 1+a4 Fe 1-p3 M p3 (PO 4-b4 )X b4 (Here, M is at least one selected from Al, Mg, and Ti, X is at least one selected from F, S, and N, and -0.5≤a4≤0.5, 0≤p3≤0.5, 0≤b4≤0.1) and the like, and any one or two or more compounds thereof may be included.

[0074] Among these, the lithium metal oxides are LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni)) in that they can improve the capacity characteristics and stability of the battery. 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 0.05 Mn 0.07 Al 0.02 )O2), lithium iron phosphate (e.g., LiFePO4), etc., and one or a mixture of two or more of these may be used, and Li(Ni) which 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.

[0075] The above positive electrode active material may be included in an amount of 60 to 98 wt%, preferably 80 to 98 wt%, and more preferably 90 to 98 wt%, based on the total weight of the positive electrode active material layer.

[0076] The conductive agent is a component for further improving the conductivity of the positive electrode active material, and the conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0077] The above-mentioned conductive material may be included in an amount of 0.1 to 20 wt%, specifically 0.5 to 10 wt%, and more specifically 0.5 to 5 wt%, based on the total weight of the positive electrode active material layer.

[0078] The above binder is a component that assists in bonding between the conductive material, the positive electrode active material, and the positive electrode current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0079] Typically, the binder may be included in an amount of 0.5 to 20 wt%, specifically 0.5 to 10 wt%, and more specifically 0.5 to 5 wt%, based on the total weight of the positive electrode active material layer.

[0080] In addition, the above-mentioned other additives may further include, for example, fillers as components that suppress expansion. The fillers are not particularly limited as long as they can suppress expansion of the electrode without causing chemical changes in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber; and the like.

[0081]

[0082] cathode

[0083] The above negative electrode has a structure including a lithium metal layer. More specifically, it may be formed of a lithium metal layer, or may have a structure in which a lithium metal layer is formed on one or both sides of a separate negative electrode current collector.

[0084] The negative electrode formed of the lithium metal layer may be formed of lithium metal itself without a separate negative electrode current collector. Accordingly, in this case, the lithium metal layer may have a sufficient thickness, for example, a thickness of 10 μm to 300 μm.

[0085] Meanwhile, a structure including a separate current collector in addition to the lithium metal layer used as the negative electrode active material layer is more preferable in terms of stability and structural aspects.

[0086] Here, the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

[0087] The above-mentioned negative electrode collector may typically have a thickness of 3 μm to 500 μm, and like the positive electrode collector, it may be provided with fine irregularities on the surface of the negative electrode collector to enhance the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0088] The above lithium metal layer can be formed by physically bonding, rolling, or depositing lithium metal on the negative electrode current collector. The deposition method can use an electrical deposition method or a chemical vapor deposition method.

[0089] Here, the lithium metal layer may include an alloy that partially contains, in addition to lithium (Li), one type of metal selected from the group consisting of nickel (Ni), tin (Sn), copper (Cu), and indium (In).

[0090] Here, the lithium metal layer can be formed to a total thickness of 10 to 300 μm so that it can sufficiently function as a negative electrode active material.

[0091]

[0092] membrane

[0093] The above separator has a structure including a substrate and an oxide-based solid electrolyte layer formed on one or both sides of the substrate and including lithium aluminum titanium phosphate (LATP).

[0094] Here, the above-mentioned substrate can be used without any special restrictions as long as it is commonly used as a separator substrate in a lithium metal battery, and in particular, it is preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity.

[0095] For example, the substrate may be 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 may be used. In addition, a typical porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc., may be used as the separator, but more specifically, it may be a polyolefin substrate.

[0096] An oxide-based solid electrolyte layer is formed on one or both sides of the above-mentioned substrate.

[0097] At this time, the oxide-based solid electrolyte layer may include an oxide-based solid electrolyte including lithium aluminum titanium phosphate (LATP) and a binder.

[0098] In addition to lithium aluminum titanium phosphate, the above oxide-based solid electrolyte may further include at least one lithium metal oxide or lithium metal phosphate selected from a Nasicon-type solid electrolyte, a Lisicon-type solid electrolyte, a Garnet-type solid electrolyte, a Perovskite-type solid electrolyte, and a LiPON-type solid electrolyte, in which case more specific examples thereof include at least one selected from the group consisting of a LAGP (lithium aluminum germanium phosphate)-based compound, an LLZO (lithium lanthanum zirconium oxide)-based compound, an LLZTO (lithium lanthanum zirconium tantalum oxide)-based compound, an LLTO (lithium lanthanum titanium oxide)-based compound, an LSTP (lithium silicon titanium phosphate)-based compound, and an LGPO (lithium germanium phosphate)-based compound.

[0099] Such oxide-based solid electrolyte may be included in an amount of 70 wt% to 99 wt%, and specifically, 80 wt% to 99 wt%, based on the total weight of the oxide-based solid electrolyte layer.

[0100] If the content is too low outside the above range, sufficient reduction intended by the present invention cannot be obtained, and if the content is too high, the content of the binder connecting them is too low, which may result in a decrease in the mechanical properties due to weakened adhesive force between the particles, which is not desirable.

[0101] The average diameter (D50) of the above oxide-based solid electrolyte particles may be 50 nanometers to 10 micrometers, specifically 50 nanometers to 5 micrometers, and more specifically 50 nanometers to 1 micrometer.

[0102] If the particle size is too small outside the above range, agglomeration between particles may occur due to reduced dispersibility. Conversely, if the particle size is too large, large pores are formed by the oxide-based solid electrolyte, which is rather unfavorable in terms of resistance. In other words, if the particle size is within the above range, lithium ion conductivity can be increased, resistance can be reduced, and improved secondary battery performance can be achieved.

[0103] The average diameter (D50) described above refers to the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The D50 can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0104] Meanwhile, the binder, which is another component of the oxide-based solid electrolyte layer, is not limited as long as it does not cause a side reaction with the electrolyte, but in particular, a glass transition temperature (Tg) as low as possible can be used, and is preferably in the range of -200 to 200°C.

[0105] In addition, the binder does not necessarily need to have ion conducting ability, but it is more preferable to use a polymer having ion conducting ability.

[0106] Therefore, it is preferable that the binder have a high dielectric constant as much as possible, and since the degree of salt dissociation in the electrolyte actually depends on the dielectric constant of the electrolyte solvent, the higher the dielectric constant of the polymer, the better the degree of salt dissociation in the electrolyte. The dielectric constant of the polymer is preferably 1 or more, specifically, a range of 1.0 to 100 (measurement frequency = 1 kHz), and is particularly preferably 10 or more.

[0107] In addition to the aforementioned functions, the binder may have the characteristic of being gelled when impregnated with a liquid electrolyte, thereby exhibiting a high degree of swelling. In fact, if the binder is a polymer having an excellent electrolyte swelling rate, the electrolyte injected after battery assembly will permeate into the polymer, and the polymer containing the absorbed electrolyte will have electrolyte ion conducting ability. Therefore, if possible, the solubility index should be in the range of 15 to 45 MPa. 1 / 2 Polymers are preferred, with a viscosity of 15 to 25 MPa. 1 / 2 and 30 to 45 MPa 1 / 2 The range is more desirable. The solubility index is 15 MPa. 1 / 2 Less than and 45 MPa 1 / 2 If it exceeds , it becomes difficult to be impregnated (swelled) by a conventional battery liquid electrolyte.

[0108] Examples of such binders include polyvinylidene fluorideco-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, It may be at least one selected from the group consisting of cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and polyvinylalcohol.

[0109] Specifically, the oxide-based solid electrolyte layer of the present invention is intended to form a reduced product of LATP by having LATP included in the oxide-based solid electrolyte layer directly contact the lithium metal layer of the negative electrode, and therefore is preferably composed of an oxide-based solid electrolyte including LATP and a binder, and it is preferable that no other materials are included as they may interfere with the reduction of LATP.

[0110] Accordingly, the binder may be included in an amount of 1 wt% to 30 wt%, specifically 1 wt% to 20 wt%, based on the total weight of the oxide-based solid electrolyte layer.

[0111] The oxide-based solid electrolyte layer may be formed on one or both sides of the substrate, but is more preferably formed on both sides because it exhibits better overvoltage reduction when formed on both sides. Of course, when 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 by the present invention.

[0112] At this time, the oxide-based solid electrolyte layer can be formed with a thickness of 0.1 ㎛ to 20 ㎛ on each side of the substrate.

[0113] If it is too thin beyond the above range, the effect of generating LATP reduction intended by the original cannot be sufficiently obtained, and if it is too thick, the resistance may rather increase, which is not desirable.

[0114] Meanwhile, the total thickness of the separator including the substrate and the oxide-based solid electrolyte layer may be 5 micrometers to 50 micrometers, specifically 5 micrometers to 40 micrometers, and more specifically 10 micrometers to 30 micrometers. When the thickness of the separator satisfies the above range, the resistance value of the lithium metal battery can be minimized while effectively preventing a short circuit between the positive and negative electrodes. As a result, the reduction in energy density of the lithium secondary battery can be prevented and the life characteristics can be improved.

[0115] Meanwhile, whether the oxide-based solid electrolyte layer is formed on one side or both sides, the oxide-based solid electrolyte layer faces the lithium metal layer of the negative electrode, and accordingly, the LATP reduction product is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0116] Here, the reduced product of the LATP may include lithiated-LATP formed by a spontaneous lithiation reaction represented by the following reaction formula 1 through contact between the LATP and the lithium metal layer.

[0117] [Reaction Formula 1]

[0118] Li 1.3 Al 0.3 Ti 1.7 (PO4)3-> Li3Al 0.3 Ti 1.7 (PO4)3

[0119] In addition, the lithium metal battery may further include a lithium non-aqueous electrolyte, whereby an SEI material may be further included on the surface of the lithium metal layer of the negative electrode. Accordingly, 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 include both the LATP reduced substance and the SEI material, and more specifically, may be composed of the LATP reduced substance and the SEI material.

[0120] At this time, the SEI material may be at least one material selected from the group consisting of LiF, Li2CO3, and Li2O, and the inorganic layer may include at least one material selected from the group consisting of lithiated-LATP, LiF, Li2CO3, and Li2O.

[0121] Since this inorganic layer is formed by contact between the LATP and lithium metal, and reaction between the lithium metal and the lithium non-aqueous electrolyte due to activation of the lithium metal battery, it can be formed mainly on the surface of the lithium metal layer.

[0122] More specifically, the LATP reduction product can be formed by a reaction between 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 a reaction between lithium ions generated by the activation process and the lithium non-aqueous electrolyte.

[0123] The above lithium non-aqueous electrolyte may include a lithium salt and a non-aqueous organic solvent.

[0124] At this time, the lithium salt is used as a medium for transferring ions within a lithium secondary battery. Lithium salt is, for example, Li as a cation. + , and the anion is 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 one selected from the group consisting of

[0125] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 , LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (Lithium bis(fluorosulfonyl) imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl) imide, LiN(SO2CF2CF3)2) and LiTFSI (lithium bis(trifluoromethanesulfonyl) imide, LiN(SO2CF3)2), but it is preferable to include Li(N(SO2CF3)2) in terms of excellent stability.

[0126] In addition to these, lithium salts commonly used in the electrolyte of lithium secondary batteries can be used without limitation.

[0127] The lithium salt may be appropriately changed within a generally usable range, but in order to obtain an optimal effect of forming a film for preventing corrosion on the electrode surface, it may be included in the electrolyte at a concentration of 0.5 M to 3 M, specifically, at a concentration of 1 M to 2.5 M, and more specifically, at a concentration of 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 a lithium secondary battery is sufficient, and the viscosity of the electrolyte is appropriate, so that the electrolyte impregnation property can be improved.

[0128] The above non-aqueous organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions during the charge / discharge process of a lithium secondary battery and can exhibit the desired properties together with additives. For example, carbonate-based organic solvents, ether-based organic solvents, or ester-based organic solvents can be used alone or in combination of two or more, and specifically, carbonate-based organic solvents can be used.

[0129] Among the organic solvents, the carbonate-based organic solvent may include at least one of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. 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), and specifically, may include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively low melting point compared to ethylene carbonate.

[0130] In addition, the linear carbonate-based organic solvent is a solvent having low viscosity and low dielectric constant, and may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and more specifically, may include dimethyl carbonate.

[0131] The above ether organic solvent may be any 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 thereof, but is not limited thereto.

[0132] The above ester organic solvent may include at least one selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents.

[0133] Specific examples of the linear ester organic solvent include, but are not limited to, 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 thereof.

[0134] The above cyclic ester organic solvent may be, as a specific example, one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more thereof, but is not limited thereto.

[0135] Among the above ester solvents, cyclic carbonate compounds are preferably used as high-viscosity organic solvents with high dielectric constants, which facilitate the dissociation of lithium salts in the electrolyte. When low-viscosity, low-dielectric constant linear carbonate compounds and linear ester compounds, such as dimethyl carbonate and diethyl carbonate, are mixed and used in an appropriate ratio with these cyclic carbonate compounds, an electrolyte with high electrical conductivity can be produced, and thus the compounds can be used more preferably.

[0136] Furthermore, the lithium non-aqueous electrolyte further includes a functional additive, and the functional additive may be included to prevent cathode collapse from occurring in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and swelling improvement effects during high-temperature storage.

[0137] Specifically, the functional additive may include at least one functional additive selected from the group consisting of a sulfone-based compound, a sulfite-based compound, a sulfone-based compound, a sulfate-based compound, a halogen-substituted carbonate-based compound, a nitrile-based compound, a cyclic carbonate-based compound, a phosphate-based compound, a borate-based compound, and a lithium salt-based compound, as representative examples thereof, and specifically, a halogen-substituted carbonate-based compound and / or a lithium salt-based compound, which may include a halogen element, and more specifically, a carbonate-based compound substituted with a fluoro group (F), and / or a lithium salt-based compound including a fluorine group (F).

[0138] The above sultone-based compound may include at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone, and may be included in an amount of 0.3 wt% to 5 wt%, specifically 1 wt% to 5 wt%, based on the total weight of the electrolyte. When the content of the sultone-based compound in the electrolyte exceeds 5 wt%, an excessively thick film may be formed on the electrode surface, which may cause an increase in resistance and a deterioration in output, and the resistance may also increase due to an excessive amount of additive, which may deteriorate the output characteristics.

[0139] The above sulfite compound may include at least one compound 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-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, and 1,3-butylene glycol sulfite, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0140] The above sulfone compound may include at least one compound selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methylethyl sulfone, and methylvinyl sulfone, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0141] The above sulfate compound may include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS), and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0142] In addition, the halogen-substituted carbonate compound may be fluoroethylene carbonate (FEC), and may be included in an amount of 10 wt% or less, specifically 5 wt% or less, based on the total weight of the electrolyte. If the content of the halogen-substituted carbonate compound in the electrolyte exceeds 10 wt%, cell swelling performance may deteriorate.

[0143] In addition, the nitrile compound may include at least one compound selected from the group consisting of succinonitrile, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0144] The cyclic carbonate compound may be vinylene carbonate (VC) or vinylethylene carbonate, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte. If the content of the cyclic carbonate compound in the electrolyte exceeds 3 wt%, the cell swelling suppression performance may deteriorate.

[0145] The above phosphate compound may include at least one compound selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tetramethyl trimethyl silyl phosphate, trimethyl silyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphite, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0146] The above borate compound may include lithium oxalyldifluoroborate, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0147] The lithium salt-based compound is a compound different from the lithium salt included in the lithium non-aqueous electrolyte, and may include at least one compound selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalatoborate (LiB(C2O4)2), LiFSI (lithium bis(fluorosulfonyl) imide, LiN(SO2F)2), and LiBF4, and specifically, may be LiFSI (lithium bis(fluorosulfonyl) imide, LiN(SO2F)2), and may be included in an amount of 3 wt% or less, specifically, 1 wt% or less, based on the total weight of the electrolyte.

[0148] The functional additives may be mixed in an amount of two or more, and may be included in an amount of 20 wt% or less, specifically 0.1 wt% to 10 wt%, based on the total weight of the lithium non-aqueous electrolyte. If the content of the functional additive exceeds 20 wt%, there is a possibility that excessive side reactions may occur within the lithium non-aqueous electrolyte during charging and discharging of the battery. In particular, since they may not be sufficiently decomposed at high temperatures, they may exist as unreacted substances or precipitated substances within the lithium non-aqueous electrolyte at room temperature. Accordingly, side reactions that reduce the lifespan or resistance characteristics of the lithium metal battery may occur.

[0149] More specifically, for the formation of the SEI material of the present invention, particularly for including LiF, the lithium non-aqueous electrolyte may include a halogen-substituted carbonate-based compound and / or a lithium salt-based compound as a functional additive, for example, fluoroethylene carbonate (FEC) and / or LiFSI (Lithium bis(fluorosulfonyl) imide, LiN(SO2F)2).

[0150] Meanwhile, since the oxide-based solid electrolyte layer includes pores therein, the inorganic layer may be formed in a form that fills part or all of the pores of the oxide-based solid electrolyte layer, or may be formed as a separate layer at the interface between the oxide-based solid electrolyte layer and the lithium metal layer, or may be formed in a form of both of these, that is, may be formed while being included in the pores or forming a layer.

[0151] When the above-mentioned inorganic layer fills the pores of the above-mentioned oxide-based solid electrolyte layer, it can be filled at 10% to 100% by volume based on the total volume of the pores, specifically at 30% to 100% by volume, and more specifically at 50% to 80% by volume.

[0152] In addition, when 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, specifically 2 nm to 80 nm, and more specifically 3 nm to 50 nm.

[0153] To more easily explain the formation of this inorganic layer, Fig. 1 shows a schematic diagram of the interface where the separator of the present invention and the cathode come into contact.

[0154] Referring to FIG. 1, the separator (110) is structured to include a substrate (111) and an oxide-based solid electrolyte layer (112) including LATP formed on one surface of the substrate (111). When this oxide-based solid electrolyte layer (112) comes into contact with a lithium metal layer (121) of an anode (120), an inorganic layer (130) including lithiated LATP, which is LATP reduced by a spontaneous reaction between LATP and Li, is formed. At this time, the inorganic layer (130) fills the gaps between the oxide-based solid electrolyte layer (112), or is formed as a separate layer having a thickness (t) and is formed on the surface of the lithium metal layer (121).

[0155]

[0156] Lithium metal battery manufacturing method

[0157] Meanwhile, according to another embodiment of the present invention,

[0158] A method for manufacturing a lithium metal battery is provided, comprising: manufacturing a lithium metal battery including an electrode assembly in which a separator having an oxide-based solid electrolyte layer including lithium aluminum titanium phosphate (LATP) formed on one or both sides thereof is interposed between a negative electrode and an positive electrode such that the oxide-based solid electrolyte is in contact with the lithium metal layer; and including a process of activating the lithium metal battery, wherein an inorganic layer including a reduced product of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

[0159] That is, the positive electrode, negative electrode, and separator are manufactured separately, and the oxide-based solid electrolyte of the separator is laminated so as to be in contact with the lithium metal layer of the negative electrode to manufacture an electrode assembly.

[0160] Thereafter, a lithium metal battery is manufactured by embedding the electrode assembly and the lithium non-aqueous electrolyte into a battery case.

[0161] In these lithium metal batteries, LATP in the oxide-based solid electrolyte layer and lithium in the lithium metal layer react to spontaneously form a LATP reduced product, i.e., lithiated-LATP.

[0162] However, the lithium metal battery undergoes an activation process after manufacturing, and accordingly, as a result of the reaction between the electrolyte and the lithium metal layer during activation, an inorganic layer including a LATP reduction product is formed on the surface of the lithium metal layer, that is, an inorganic layer including, in addition to the LATP reduction product, an SEI material, specifically, one or more materials selected from the group consisting of LiF, Li2CO3, and Li2O.

[0163] At this time, the above-mentioned inorganic layer is as described above.

[0164] Meanwhile, this activation process may include a room temperature aging process for 12 to 36 hours, during which time the reduction of LATP may occur spontaneously.

[0165] Additionally, the activation process may include a process of charging the lithium metal battery one or more times, through which an SEI material may be formed.

[0166] When an inorganic layer is formed on the surface of the lithium metal layer through an activation process such as this, a denser interface can be formed between the separator and the negative electrode, which can reduce the driving force required for Li ions to penetrate the SEI, thereby exhibiting an effect of improving output characteristics.

[0167] Meanwhile, the lithium non-aqueous electrolyte incorporated together with the electrode assembly in the manufacture of the lithium metal battery is as described above.

[0168]

[0169] Hereinafter, examples will be described to demonstrate that a lithium secondary battery according to one embodiment of the present invention exhibits improved effects.

[0170]

[0171] <Example 1>

[0172] A separator was manufactured by forming an oxide-based solid electrolyte layer (thickness: 20 μm) on one side of a polyolefin material substrate (thickness: 9 μm).

[0173] 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) in a weight ratio of 95:5 and dispersing it in acetone, and coating one side of the polyolefin material substrate and drying it.

[0174]

[0175] <Example 2>

[0176] A separator was manufactured in the same manner as in Example 1, except that the oxide-based solid electrolyte layer was formed on both sides of a polyolefin material substrate (thickness: 2 μm each).

[0177]

[0178] <Comparative Example 1>

[0179] A separation membrane was manufactured by forming an organic-inorganic mixed layer (thickness: 20 μm) on one side of a polyolefin material substrate (thickness: 15 μm).

[0180] Here, the organic / inorganic mixed layer was manufactured by mixing Al2O3:PVdF in a weight ratio of 95:5 and dispersing it in NMP, coating the organic / inorganic slurry on one surface of the polyolefin material substrate, and drying it.

[0181]

[0182] <Comparative Example 2>

[0183] A substrate made of polyolefin material (thickness: 35 micrometers) was prepared.

[0184]

[0185] Experimental Example 1

[0186] The separators manufactured in Example 1 and Comparative Example 1 were sandwiched between lithium foil (thickness: 300 ㎛) as a positive electrode and lithium foil (thickness: 300 ㎛) as a negative electrode, and the oxide-based solid electrolyte layer or the organic-inorganic mixed layer was made to face the lithium foil of the negative electrode to manufacture an electrode assembly, and LiPF6 was dissolved to 1.0 M in a non-aqueous organic solvent having a composition of ethylene carbonate (EC) : ethyl methyl carbonate (EMC) = 30 : 70 (volume ratio), and fluoroethylene carbonate (FEC) 0.5 wt%, LiFSI (Lithium bis(fluorosulfonyl) imide, LiN(SO2F)2), vinylene carbonate (VC) 0.5 wt%, 1,3-propane sultone (PS) 0.5 wt%, ethylene sulfate (Ethylene Sulfate; Esa), 1.0 wt%, Li / Li symmetric cells were manufactured by injecting an electrolyte containing 0.2 wt% of 1,3-propene sultone (PRS) as an additive.

[0187] After the above Li / Li symmetric cells were left at 25°C for 24 hours, they were disassembled and the surface of the separator was observed, and the photograph thereof is shown in Figure 2 below.

[0188] Referring to FIG. 2, in the case of including a separator according to Example 1, it can be confirmed that a reduced substance is formed on the surface of the oxide-based solid electrolyte layer, whereas in the case of the separator of Comparative Example 2 using alumina, it can be seen that no substance is formed on the surface.

[0189]

[0190] Experimental Example 2

[0191] Using the separator of Example 1, a Li / Li symmetrical cell manufactured as in Experimental Example 1 was charged at 25°C with a constant current of 0.33C until the voltage reached 4.35 V, aged at 25°C for 24 hours, aged at 60°C for 20 hours, and then completely discharged at a constant current of 0.33C to perform activation.

[0192] XRD analysis was performed on the separator coating layer before and after the activation process of the above Li / Li symmetric cell, and the results are shown in Fig. 3.

[0193] Before activation, no peak of lithiated-LATP composition was found, but after activation, overall peak broadness appeared, and it was confirmed that a peak of lithiated-LATP composition, which is presumed to be a LATP reduction product, was found.

[0194]

[0195] Experimental Example 3

[0196] In the above Experimental Example 2, after activation, the Li metal surface facing the separator coating layer was analyzed, and again, the Li / Li symmetrical cell was charged at a constant current-constant voltage of 0.33 C and 4.35 V at 25°C, and discharged at a constant current of 0.33 C 70 times, and the Li metal surface was analyzed twice, and the results are shown in Fig. 4 below.

[0197] The above Li metal surface analysis was performed using the XPS spectra method, and the equipment used was the Nexsa G2 ESCA system, Thermo Fisher Scientific, and was performed under the following conditions.

[0198] -X ray source: Monochromated Al Ka ​​(1486.6eV),

[0199] -X-ray spot size: 400㎛

[0200] -Sputtering gun: Monatomic Ar (energy: 1000eV, current: low, raster width: 2mm)

[0201] -Operation mode Constant Analyzer Energy mode

[0202] -Survey scan: pass energy 200eV, energy step 1eV,

[0203] -Narrow scan: scanned mode, pass energy 50eV, energy step 0.1eV

[0204] Referring to Figure 4, it can be confirmed that the metal oxide peak is significantly observed and the LiF peak is clearly observed, which is due to the reaction between LATP and the lithium metal layer. + The coordination number decreases, and Li + This is because the electron bias of the fluorine group (F) contained in the lithium non-aqueous electrolyte is alleviated, making the reduction of the fluorine group (F) relatively easy.

[0205]

[0206] Experimental Example 4

[0207] Using the separators of Examples 1, 2, and Comparative Example 2, Li / Li symmetric cells similar to Experimental Example 1 were manufactured.

[0208] 1 mA / cm for the above Li / Li symmetric cells 2 Li plating / stripping evaluation was performed for 20 hours by applying oxidation and reduction currents alternately for 1 hour, and the results are shown in Figure 5 below.

[0209] Referring to FIG. 5, it can be seen that the Li / Li symmetric cells using the separators of Examples 1 and 2 show a reduced overvoltage behavior compared to the Li / Li symmetric cells using the separator of Comparative Example 2.

[0210]

[0211] Experimental Example 5

[0212] Using the separators of Example 1 and Comparative Example 1, Li / Li symmetrical cells similar to Experimental Example 1 were manufactured.

[0213] For the above Li / Li symmetrical cells, a PEIS evaluation was conducted to show the current signal that appears when an AC voltage in the frequency range of 1 MHz to 50 mHz is applied at SOC 10, 30, 50, 70, and 90 charge states, respectively, and the results are shown in Fig. 6 below.

[0214] Referring to Fig. 6, it can be confirmed that the Seim circle size of the separator of Example 1 coated with an oxide-based solid electrolyte layer is smaller and thus exhibits lower resistance compared to the case where the separator of Comparative Example 1 coated with alumina over the entire SOC region is used.

[0215]

[0216] <Example 3>

[0217] An aluminum (Al) metal thin film with a thickness of 15 micrometers is prepared as a cathode current collector, and Li(Ni) is applied as a cathode active material on one surface of the aluminum metal thin film. 0.86 Co 0.05 Mn 0.07 Al 0.02 )O2: A cathode slurry was prepared by dispersing carbon nanotubes as a conductive material and PVDF as a binder in a weight ratio of 96 1:3 in NMP solvent, and coating, drying, and rolling to a thickness of 60 micrometers to prepare a cathode.

[0218] An electrode assembly was manufactured by interposing the separator of Example 1 between the positive electrode and a lithium foil (thickness: 300 μm) as a negative electrode, with the oxide-based solid electrolyte layer facing the negative electrode, and then placing the electrode assembly in a case together with an electrolyte in which LiPF6 was dissolved 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 manufacture a coin half-cell.

[0219]

[0220] <Comparative Example 3>

[0221] A coin half-cell was manufactured in the same manner as in Example 3, except that the electrode assembly was manufactured by interposing the oxide-based solid electrolyte layer so that it faced the anode.

[0222]

[0223] Experimental Example 6

[0224] For each of the coin half-cells manufactured in Example 3 and Comparative Example 3, the cells were left at 25°C for 24 hours, and the OCV (open circuit voltage) was measured, which is shown in Figures 7 and 8 below.

[0225] Referring to FIGS. 7 and 8, it can be confirmed that the OCV shaking behavior due to the spontaneous reduction reaction of LATP is observed only in FIG. 7 of Example 3.

[0226]

[0227] Anyone with ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

[0228] The lithium metal battery according to the present invention secures safety by forming an oxide-based solid electrolyte layer containing LATP on a separator substrate, and by directly contacting the oxide-based solid electrolyte layer containing LATP with a lithium metal layer to form a LATP reduction product at the interface therebetween, thereby reducing the driving force required for Li ions to penetrate the SEI by forming a dense interface between the negative electrode containing the lithium metal layer and the separator, thereby lowering the resistance due to SEI formation and thus improving the output characteristics of the lithium metal battery.

Claims

1. A cathode including a cathode current collector and a cathode active material layer formed on one or both sides of the cathode current collector. A cathode comprising a lithium metal layer, and A separator comprising a substrate and an oxide-based solid electrolyte layer formed on one or both sides of the substrate and including lithium aluminum titanium phosphate (LATP); The oxide-based solid electrolyte layer of the above separator faces the lithium metal layer of the above negative electrode, A 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.

2. In paragraph 1, A lithium metal battery, wherein the inorganic layer fills part or all of the pores of the oxide-based solid electrolyte layer, forms a separate layer at the interface between the oxide-based solid electrolyte layer and the lithium metal layer, or is included in the form of all of these.

3. In paragraph 2, A lithium metal battery, wherein the inorganic layer fills the pores of the oxide-based solid electrolyte layer by 10 to 100 volume% based on the total pore volume and forms a separate layer having a thickness of 1 to 100 nm.

4. In paragraph 1, A lithium metal battery, wherein the reduced product of the above LATP comprises lithiated-LATP, wherein the LATP is formed by a spontaneous lithiation reaction represented by the following reaction scheme 1. [Reaction Formula 1] Li 1.3 Al 0.3 You 1.7 (PO 4 ) 3 -> Li 3 Al 0.3 You 1.7 (PO 4 ) 3 5. In paragraph 1, The above lithium metal battery further comprises a lithium non-aqueous electrolyte, The above inorganic layer further comprises the LATP reduction product and SEI material, and the SEI material comprises LiF, Li 2 CO 3 , and Li 2 A lithium metal battery comprising at least one substance selected from the group consisting of O.

6. In paragraph 5, A lithium metal battery, wherein the above-mentioned inorganic layer is composed of a LATP reduction product and an SEI material.

7. In paragraph 1, A lithium metal battery in which the above oxide-based solid electrolyte layers are formed on both sides of the substrate.

8. In paragraph 1, The above description relates to a lithium metal battery having a polyolefin substrate.

9. In paragraph 1, A lithium metal battery, wherein the oxide-based solid electrolyte layer is composed of an oxide-based solid electrolyte including lithium aluminum titanium phosphate (LATP) and a binder.

10. In paragraph 1, A lithium metal battery, wherein the oxide-based solid electrolyte layers are formed on one side of the substrate to a thickness of 0.1 ㎛ to 20 ㎛.

11. In paragraph 1, The above cathode active material layer is a lithium metal battery including a lithium transition metal oxide represented by the following chemical formula 1 as a cathode active material: [Chemical Formula 1] Li 1+x Ni a Co b Mr c M 1-(a+b+c) O 2 In the above formula, M is at least one 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<1이다.

12. A method for manufacturing a lithium metal battery according to Article 1, A method for manufacturing a lithium metal battery, comprising: a process for manufacturing a lithium metal battery including an electrode assembly in which a separator having an oxide-based solid electrolyte layer including lithium aluminum titanium phosphate (LATP) formed on one or both sides thereof is interposed between an anode and an cathode so that the oxide-based solid electrolyte is in contact with the lithium metal layer; and a process for activating the lithium metal battery, wherein an inorganic layer including a reduced product of LATP is formed at the interface between the oxide-based solid electrolyte layer and the lithium metal layer.

13. In paragraph 12, A method for manufacturing a lithium metal battery, wherein the above lithium metal battery is manufactured by embedding the electrode assembly and the lithium non-aqueous electrolyte in a battery case.

14. In paragraph 12, The above inorganic layer further comprises a reduced product of the LATP and an SEI material, and the SEI material comprises LiF, Li 2 CO 3 , and Li 2 Method for manufacturing a lithium metal battery, wherein at least one substance is selected from the group consisting of O 15. In paragraph 12, A method for manufacturing a lithium metal battery, wherein the above activating process includes a room temperature aging process for 12 to 36 hours.

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