Lithium metal secondary battery

Abstract

The invention relates to a lithium metal secondary battery. The lithium metal secondary battery has a negative electrode current collector layer, a composite alloy layer, a lithium metal layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order, and the composite alloy layer contains a combination of a lithium-gallium alloy and a lithium-tin alloy and / or a lithium-indium alloy.

Description

Technical Field

[0001] The present disclosure relates to a lithium metal secondary battery. Background Art

[0002] In the case of lithium metal secondary batteries, lithium metal, which has a high ionization tendency among metals, is used as the negative electrode active material. Since the potential difference between the negative electrode and the positive electrode of the lithium metal secondary battery is large, a high output voltage is obtained, and the lithium metal secondary battery has a high theoretical capacity density, so its practical application is expected, and the following lithium metal secondary battery is disclosed.

[0003] For example, Japanese Patent Publication No. 2023-035226 discloses a lithium metal secondary battery having a solid electrolyte layer between a positive electrode and a negative electrode, wherein the negative electrode has a negative electrode collector and a protective layer, wherein the protective layer contains a metal that can be alloyed with lithium, and the volume capacity density is 1000 mAh / L or more. According to the lithium metal secondary battery of Japanese Patent Publication No. 2023-035226, it is said that durability can be improved. Summary of the invention

[0004] Lithium metal secondary batteries are expected to have excellent battery characteristics, but in reality, they have high resistance and low reversible capacity. Therefore, lithium metal secondary batteries have room for improvement from the perspectives of resistance and reversible capacity.

[0005] Therefore, an object of the present disclosure is to provide a lithium metal secondary battery capable of reducing resistance and increasing reversible capacity.

[0006] The present disclosure adopts the following means to achieve the above-mentioned objectives.

[0007] <Scheme 1>

[0008] A lithium metal secondary battery, which has a negative electrode collector layer, a composite alloy layer, a lithium metal layer, an electrolyte layer, a positive electrode active material layer and a positive electrode collector layer in sequence, and the composite alloy layer contains a combination of a lithium-gallium alloy and a lithium-tin alloy and / or a lithium-indium alloy.

[0009] <Scheme 2>

[0010] The lithium metal secondary battery according to claim 1, wherein the composite alloy layer includes a lithium-gallium alloy and a lithium-tin alloy, and the atomic ratio of gallium in the composite alloy layer to the total of gallium and tin is 10 to 90 atomic %.

[0011] <Scheme 3>

[0012] The lithium metal secondary battery according to embodiment 1 or 2, wherein the composite alloy layer contains a lithium-gallium alloy and a lithium-indium alloy, and the atomic ratio of gallium in the composite alloy layer to the total of gallium and indium is 10 to 45 atomic %.

[0013] According to the lithium metal secondary battery of the present disclosure, it is possible to reduce resistance and increase reversible capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and

[0015] in:

[0016] Figure 1A It is a schematic diagram for explaining the lithium metal secondary battery of the present disclosure.

[0017] Figure 1B It is a schematic diagram for explaining the lithium metal secondary battery of the present disclosure.

[0018] Figure 2A The following is an image showing a surface SEM image of the composite metal layer A3 of Example 3.

[0019] Figure 2B An image showing the results of EDX mapping analysis using surface SEM-EDX for each element of the composite metal layer A3 of Example 3 (overlap of the elements of oxygen (O), iron (Fe), nickel (Ni), gallium (Ga), and tin (Sn)).

[0020] Figure 2C This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for the composite metal layer A3 of Example 3 (oxygen (O)).

[0021] Figure 2D This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for the composite metal layer A3 of Example 3 (iron (Fe)).

[0022] Figure 2E This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for the composite metal layer A3 of Example 3 (nickel (Ni)).

[0023] Figure 2F This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for composite metal layer A3 of Example 3 (gallium (Ga)).

[0024] Figure 2G This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for the composite metal layer A3 of Example 3 (tin (Sn)).

[0025] Figure 3AAn image showing the results of EDX mapping analysis using cross-sectional SEM-EDX for each element of the lithium metal secondary battery D3 of Example 3 (overlap of the elements of sulfur (S), oxygen (O), iron (Fe), nickel (Ni), gallium (Ga), and tin (Sn)).

[0026] Figure 3B This is an image showing the results of EDX mapping analysis using cross-sectional SEM-EDX for each element in the lithium metal secondary battery D3 of Example 3 (sulfur (S)).

[0027] Figure 3C This is an image showing the results of EDX mapping analysis using cross-sectional SEM-EDX for each element in the lithium metal secondary battery D3 of Example 3 (oxygen (O)).

[0028] Figure 3D This is an image showing the results of EDX mapping analysis using cross-sectional SEM-EDX for each element in the lithium metal secondary battery D3 of Example 3 (iron (Fe)).

[0029] Figure 3E This is an image showing the results of EDX mapping analysis using cross-sectional SEM-EDX for each element in the lithium metal secondary battery D3 of Example 3 (nickel (Ni)).

[0030] Figure 3F This is an image showing the results of EDX mapping analysis using cross-sectional SEM-EDX for each element in the lithium metal secondary battery D3 of Example 3 (gallium (Ga)).

[0031] Figure 3G This is an image showing the results of EDX mapping analysis using cross-sectional SEM-EDX for each element in the lithium metal secondary battery D3 of Example 3 (tin (Sn)).

[0032] Figure 4A The image shows a cross-sectional SEM image of the lithium metal secondary battery D3 of Example 3.

[0033] Figure 4B It is a schematic diagram of the cross-sectional structure of the lithium metal secondary battery D3 of Example 3.

[0034] Figure 5A An image showing a surface SEM image of the composite metal layer A7 of Example 7.

[0035] Figure 5B This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for the composite metal layer A7 of Example 7 (overlap of the elements of oxygen (O), gallium (Ga), and indium (In)).

[0036] Figure 5C This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for the composite metal layer A7 of Example 7 (oxygen (O)).

[0037] Figure 5D This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for the composite metal layer A7 of Example 7 (gallium (Ga)).

[0038] Figure 5E This is an image showing the results of EDX mapping analysis using surface SEM-EDX for each element for the composite metal layer A7 of Example 7 (indium (In)). DETAILED DESCRIPTION

[0039] The following is a detailed description of the embodiments of the present disclosure. It should be noted that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the main purpose of the present disclosure. In addition, in the description of the drawings, the same reference numerals are used for the same elements, and repeated descriptions are omitted.

[0040] In the present disclosure, "composite material" means a composition that can form a positive electrode active material layer and an electrolyte layer by being either as is or further containing other components. In addition, in the present disclosure, "composite material slurry" means a slurry that contains a dispersion medium in addition to the "composite material" and can be applied and dried to form a positive electrode active material layer and an electrolyte layer.

[0041] The lithium metal secondary battery disclosed in the present invention may be a liquid battery containing an electrolyte as an electrolyte layer, or a solid battery having a solid electrolyte layer as an electrolyte layer. It should be noted that, with respect to the present disclosure, "solid battery" means a battery using at least a solid electrolyte as an electrolyte, and therefore, a solid battery may use a combination of a solid electrolyte and a liquid electrolyte as an electrolyte. In addition, the lithium metal secondary battery disclosed in the present invention may be an all-solid battery, that is, a battery using only a solid electrolyte as an electrolyte.

[0042] 《Lithium Metal Secondary Batteries》

[0043] The lithium metal secondary battery disclosed in the present invention has a negative electrode collector layer, a composite alloy layer, a lithium metal layer, an electrolyte layer, a positive electrode active material layer and a positive electrode collector layer in sequence, and the above-mentioned composite alloy layer contains a combination of lithium-gallium alloy, lithium-tin alloy and / or lithium-indium alloy.

[0044] According to the lithium metal secondary battery of the present disclosure, it is possible to reduce resistance and increase reversible capacity.

[0045] In the present disclosure, the composite alloy layer is not particularly limited, and can be formed by a composite metal layer comprising a combination of gallium and tin and / or indium. Figure 2A , Figure 2B , Figure 2C , Figure 2D , Figure 2E , Figure 2F , Figure 2G and Figure 5A , Figure 5B , Figure 5C , Figure 5D , Figure 5E As shown, a composite body is formed in a manner that gallium surrounds tin particles or indium particles. By charging a lithium metal secondary battery including a composite metal layer, gallium, tin and / or indium in the composite metal layer can react with lithium moved from the positive electrode active material layer holding lithium, so that each metal in the composite metal layer is alloyed with lithium, thereby forming a composite alloy layer containing a composite body of a lithium-gallium alloy, a lithium-tin alloy and / or a lithium-indium alloy.

[0046] Not limited by theory, specifically, for example Figure 1A , Figure 1B As shown, it is speculated that by forming the composite alloy layer 120 including the above-mentioned composite near the negative electrode collector layer 110, the interface peeling between the electrolyte layer 130 and the lithium metal layer 121 during lithium separation is suppressed, thereby reducing the resistance and increasing the reversible capacity.

[0047] <Structure of lithium metal secondary battery>

[0048] The lithium metal secondary battery disclosed herein includes a negative electrode current collector layer, a composite alloy layer, a lithium metal layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order.

[0049] 〈Negative electrode current collector layer〉

[0050] There is no particular limitation on the material used in the negative electrode collector layer, and the material generally used as the negative electrode collector of the lithium metal secondary battery can be appropriately adopted. As the material for the negative electrode collector layer, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, or carbon sheet can be listed, but it is not limited to this case. In particular, from the viewpoint of ensuring reduction resistance and the viewpoint of difficulty in alloying with lithium, the material for the negative electrode collector layer may include at least one metal selected from Cu, Ni and stainless steel, and may also be composed of a carbon sheet. As for the negative electrode collector layer, in order to adjust the resistance, etc., some coatings may be provided on its surface.

[0051] The shape of the negative electrode current collector layer is not particularly limited, and examples thereof include a foil shape, a plate shape, a mesh shape, etc. Among these, a foil shape is preferred.

[0052] The thickness of the negative electrode current collector layer is not particularly limited, and may be 0.1 μm or more, or 1 μm or more, and may be 1 mm or less, or 100 μm or less.

[0053] 〈Composite alloy layer〉

[0054] The composite alloy layer of the lithium metal secondary battery disclosed herein comprises a combination of a lithium-gallium alloy and at least one selected from a lithium-tin alloy and a lithium-indium alloy.

[0055] 〈Composite alloy layer: lithium-gallium alloy / lithium-tin alloy layer〉

[0056] The composite alloy layer of the lithium metal secondary battery of the present disclosure may include a lithium-gallium alloy and a lithium-tin alloy.

[0057] The atomic ratio of gallium to the total of gallium and tin in the composite alloy layer is not particularly limited, and may be 10 to 90 atomic %. The atomic ratio is not particularly limited, and may be 5 atomic % or more, 10 atomic % or more, 20 atomic % or more, 30 atomic % or more, 40 atomic % or more, 50 atomic % or more, or 60 atomic % or more, and may be 95 atomic % or less, 90 atomic % or less, 85 atomic % or less, or 80 atomic % or less.

[0058] The composite alloy layer may further contain metals other than gallium, tin and lithium. There is no particular limitation on the metals other than gallium, tin and lithium, and in the composite alloy layer, the metals may be 0 atomic % or more, 1 atomic % or more, 3 atomic % or more, or 5 atomic % or less, 20 atomic % or less, or 10 atomic % or less.

[0059] 〈Composite alloy layer: lithium-gallium alloy / lithium-indium alloy layer〉

[0060] The composite alloy layer of the lithium metal secondary battery of the present disclosure may include a lithium-gallium alloy and a lithium-indium alloy.

[0061] The atomic ratio of gallium to the total of gallium and indium in the composite alloy layer is not particularly limited, and may be 10 to 45 atomic %. The atomic ratio is not particularly limited, and may be 5 atomic % or more, 10 atomic % or more, 15 atomic % or more, 20 atomic % or more, 25 atomic % or more, 30 atomic % or more, 35 atomic % or more, or 40 atomic % or more, and may be 90 atomic % or less, 80 atomic % or less, 70 atomic % or less, 60 atomic % or less, 50 atomic % or less, or 45 atomic % or less.

[0062] The composite alloy layer may further contain metals other than gallium, indium and lithium. There is no particular limitation on the metals other than gallium, indium and lithium, and in the composite alloy layer, the metals may be 0 atomic % or more, 1 atomic % or more, 3 atomic % or more, or 5 atomic % or less, 50 atomic % or less, 20 atomic % or less, or 10 atomic % or less.

[0063] There is no particular limitation on the thickness of the composite alloy layer. In a fully charged state, it may be greater than 0.1 μm, greater than 0.2 μm, greater than 0.5 μm, or greater than 1.0 μm; it may be less than 5.0 μm, less than 4.0 μm, less than 3.0 μm, or less than 2.0 μm.

[0064] The composite alloy layer is not particularly limited, and can be easily formed by a composite metal layer containing gallium, tin and / or indium in combination. Specifically, by charging a lithium metal secondary battery including a composite metal layer, gallium, tin and / or indium in the composite metal layer can react with lithium moved from the positive electrode active material layer that retains lithium, so that each metal in the composite metal layer is alloyed with lithium, thereby forming a composite alloy layer containing a composite of a lithium-gallium alloy, a lithium-tin alloy and / or a lithium-indium alloy.

[0065] In addition, the composite metal layer can be easily formed on the negative electrode current collector by a two-component vapor deposition method using ion plating, for example, but is not limited to this case.

[0066] 〈Lithium metal layer〉

[0067] The lithium metal secondary battery of the present disclosure has a lithium metal layer. The lithium metal layer functions as a negative electrode active material layer in the lithium metal secondary battery of the present disclosure.

[0068] Among them, the lithium metal layer functions as a "negative electrode active material layer". Therefore, in the charged state, there is a layer of lithium metal serving as the "negative electrode active material layer". In the discharged state, the lithium metal moves to the positive electrode active material layer as lithium ions, and sometimes there is no layer of lithium metal serving as the "negative electrode active material layer".

[0069] The shape of the lithium metal layer is not particularly limited, and may be, for example, a substantially flat sheet-shaped lithium metal layer. The thickness of the lithium metal layer is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more, and may be 2 mm or less, 1 mm or less, or 500 μm or less in a fully charged state.

[0070] 〈Electrolyte layer〉

[0071] <Electrolyte layer-solid electrolyte layer>

[0072] The lithium metal secondary battery of the present disclosure can be a solid battery, that is, a battery having a solid electrolyte layer as an electrolyte layer.

[0073] The solid electrolyte layer contains a solid electrolyte and may contain a binder and the like as necessary.

[0074] (Solid Electrolyte)

[0075] The material of the solid electrolyte is not particularly limited, and may be, for example, a sulfide solid electrolyte, an oxide solid electrolyte, or a polymer electrolyte.

[0076] Examples of sulfide solid electrolytes include, but are not limited to, sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include Li2S-P2S5 (Li7P3S 11 , Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2 (Li 13 GeP3S 16 , Li 10 GeP2S 12 etc.), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl x etc.; or combinations thereof, but are not limited to these.

[0077] Examples of oxide solid electrolytes include Li7La3Zr2O 12 , Li 7-x Ln3Z 1-x Nb x O 12 , Li 7- 3x La3Zr2Al x O 12 , Li 3x La 2 / 3-x TiO3、Li 1+x Al x Ti 2-x (PO4)3、Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, or Li 3+x PO 4- x N x (LiPON), etc., but are not limited to these.

[0078] The sulfide solid electrolyte and the oxide solid electrolyte may be glass or crystallized glass (glass ceramic).

[0079] Examples of the polymer electrolyte include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof, but the polymer electrolyte is not limited thereto.

[0080] (Adhesive)

[0081] There is no particular limitation on the binder. The binder may be, for example, polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR) and the like, but is not limited thereto. There is no particular limitation on the binder, and only one type may be used alone or two or more types may be used in combination.

[0082] The thickness of the solid electrolyte layer is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more, and may be 2 mm or less, 1 mm or less, or 500 μm or less.

[0083] The solid electrolyte layer can be easily formed by, for example, molding an electrolyte composite material containing the above-mentioned solid electrolyte and a binder etc. in a dry or wet manner.

[0084] <Electrolyte layer-separator layer>

[0085] The lithium metal secondary battery of the present disclosure may be a liquid-based battery, that is, a battery having an electrolyte solution, particularly an electrolyte solution retained by a separator layer, as an electrolyte layer.

[0086] (Electrolyte)

[0087] The electrolyte solution is not particularly limited, but preferably contains a supporting salt and a solvent.

[0088] The supporting salt (lithium salt) of the electrolyte having lithium ion conductivity is not particularly limited, and inorganic lithium salts, organic lithium salts, etc. can be listed. As inorganic lithium salts, for example, LiPF6, LiBF4, LiClO4, LiAsF6, etc. can be listed, but it is not limited to these cases. As organic lithium salts, for example, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, LiC(CF3SO2)3, etc. can be listed, but it is not limited to these cases.

[0089] As the solvent for the electrolyte, it is not particularly limited, and cyclic carbonates, chain carbonates, etc. can be listed. As cyclic carbonates, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be listed, but it is not limited to this case. As chain carbonates, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc. can be listed, but it is not limited to this case. The electrolyte is not particularly limited, and only one kind can be used alone, or two or more kinds can be used in combination.

[0090] (Separator)

[0091] The separator is not particularly limited, and any separator generally used as a separator for lithium metal secondary batteries can be appropriately adopted. As the separator, for example, a nonwoven fabric of a polyolefin, polyamide, or polyimide type can be used.

[0092] <Positive electrode active material layer>

[0093] The positive electrode active material layer contains at least a positive electrode active material, and further optionally contains a conductive aid, a solid electrolyte, and a binder, etc. The positive electrode active material layer may also contain various additives. The content of each of the positive electrode active material, conductive aid, binder, etc. in the positive electrode active material layer can be appropriately determined according to the target battery performance. For example, the entirety of the positive electrode active material layer (the entire solid component) is set to 100% by mass, and the content of the positive electrode active material can be more than 40% by mass, more than 50% by mass, more than 60% by mass, and can be less than 100% by mass, or less than 90% by mass.

[0094] (Positive electrode active material)

[0095] The material of the positive electrode active material is not particularly limited as long as it can absorb and release lithium ions. Examples of the positive electrode active material include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), nickel-cobalt-manganese oxide (NCM), LiCO 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, nickel-cobalt-aluminum oxide (NCA; LiNi x Co y Al z O2), by Li 1+x Mn 2-x-y M y The heterogeneous element-substituted Li—Mn spinel having a composition represented by O4 (M is one or more metal elements selected from Al, Mg, Co, Fe, Ni and Zn) is not limited to these.

[0096] The positive electrode active material is not particularly limited and may have a coating layer. The coating layer is a layer containing a material having lithium ion conductivity, low reactivity with the positive electrode active material and the solid electrolyte, and capable of maintaining a coating layer shape that does not flow even when in contact with the active material and the solid electrolyte. Specific examples of materials constituting the coating layer include Li4Ti5O 12 , Li3PO4, etc., but are not limited to these.

[0097] The shape of the positive electrode active material is not particularly limited as long as it is a general shape of a positive electrode active material for a lithium metal secondary battery. The positive electrode active material may be, for example, in the form of particles. The positive electrode active material may be a primary particle or a secondary particle formed by agglomerating a plurality of primary particles. The average particle size D of the positive electrode active material is 50 For example, the average particle size D may be 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. 50 It is a particle diameter (median diameter) at a cumulative value of 50% in a volume-based particle size distribution determined by a laser diffraction scattering method.

[0098] (Conductive additive)

[0099] There is no particular limitation on the conductive aid. The conductive aid may be, for example, vapor grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotube (CNT), carbon nanofiber (CNF), etc., but is not limited thereto. The conductive aid may be, for example, in the form of particles or fibers, and there is no particular limitation on the size thereof. There is no particular limitation on the conductive aid, and one type may be used alone, or two or more types may be used in combination.

[0100] For the solid electrolyte and the binder, reference can be made to the description in the above-mentioned “<Electrolyte layer—Solid electrolyte layer>”.

[0101] The shape of the positive electrode active material layer is not particularly limited, and for example, it can be a sheet-shaped positive electrode active material layer with a substantially flat surface. The thickness of the positive electrode active material layer is not particularly limited, and for example, it can be 0.1 μm or more, 1 μm or more, or 10 μm or more, and can be 2 mm or less, 1 mm or less, or 500 μm or less.

[0102] 〈Positive electrode collector layer〉

[0103] There is no particular limitation on the material used in the positive electrode collector layer, and a positive electrode collector generally used as a positive electrode collector of a lithium metal secondary battery can be appropriately used. As materials for the positive electrode collector layer, for example, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. can be listed, but it is not limited to this case. In addition, for the positive electrode collector layer, in order to adjust the resistance, etc., some coatings may be provided on its surface. In addition, the positive electrode collector layer may be formed by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate.

[0104] The shape of the positive electrode current collector layer is not particularly limited, and examples thereof include a foil shape, a plate shape, a mesh shape, etc. Among these, a foil shape is preferred.

[0105] The thickness of the positive electrode current collector layer is not particularly limited, and may be 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0106] The positive electrode active material layer can be manufactured by applying a known method. For example, the positive electrode active material layer can be easily molded by molding the positive electrode composite material containing the above-mentioned various components in a dry or wet manner. The positive electrode active material layer can be molded together with the positive electrode collector layer, or can be molded separately from the positive electrode collector layer.

[0107] Figure 1A , Figure 1B This is a schematic diagram showing one embodiment of the lithium metal secondary battery of the present disclosure, but the present invention is not limited to this embodiment.

[0108] In the discharge state, the lithium metal secondary battery 100 is Figure 1A As shown in FIG. 1 , the negative electrode current collector layer 110, the composite alloy layer 120, the electrolyte layer 130, the positive electrode active material layer 140 and the positive electrode current collector layer 150 may be stacked in sequence, and the lithium metal layer 121 may not be present. In the charged state, the lithium metal secondary battery 100 is as Figure 1B As shown, it can be a battery in which a negative electrode collector layer 110, a composite alloy layer 120, a lithium metal layer 121, an electrolyte layer 130, a positive electrode active material layer 140 and a positive electrode collector layer 150 are stacked in sequence, and there is a lithium metal layer 121 as a negative electrode active material layer. The composite alloy layer 120 includes a combination of a lithium-gallium alloy and a lithium-tin alloy and / or a lithium-indium alloy. By forming the composite alloy layer 120 near the negative electrode collector layer 110, the interface peeling between the electrolyte layer 130 and the lithium metal layer 121 when lithium is separated is suppressed, thereby reducing the resistance and increasing the reversible capacity.

[0109] With regard to the lithium metal secondary battery disclosed in the present invention, for example, a stack is prepared in which a negative electrode collector layer, a composite metal layer, an electrolyte layer, a positive electrode active material layer and a positive electrode collector layer are stacked in sequence, and the stack is contained in a stacking film, vacuum-sealed and pressed to prepare a preparatory lithium metal secondary battery. The preparatory lithium metal secondary battery is charged, so that the various metals contained in the composite metal layer react with the lithium moved from the positive electrode active material to alloy, thereby forming a composite alloy layer, and a lithium metal secondary battery can be obtained, but it is not limited to this case.

[0110] Examples of the shape of the lithium metal secondary battery include a coin shape, a stacked shape, a cylindrical shape, and a square shape, but the shape is not limited to these.

[0111] The present disclosure will be described in more detail with reference to the following examples, but the scope of the present disclosure is not limited to these examples.

[0112] 《Example 1》

[0113] <Production of Composite Metal Layer A1>

[0114] A composite metal layer containing gallium and tin was formed on a stainless steel (SUS) foil as a negative electrode current collector in a manner of 1.0 μm thick by binary evaporation based on an ion plating method, thereby producing a composite metal layer A1 formed on the SUS foil. At this time, the composite metal layer A1 was produced in a manner in which the atomic ratio of gallium to the total of gallium and tin was 10 atomic %. The composite metal layer A1 obtained had an atomic ratio of gallium to the total of gallium and tin of 13 atomic %.

[0115] <Preparation of Electrolyte Layer B1>

[0116] The electrolyte composite slurry was prepared by mixing a sulfide solid electrolyte (92.6 parts by mass) as a solid electrolyte, a binder (7.4 parts by mass) and an appropriate amount of butyl butyrate as a dispersion medium. The obtained electrolyte composite slurry was applied on a release film with a coating gap of 325 μm. Then, it was pre-dried at room temperature for 3 hours and fully dried at 165°C for 1 hour. The fully dried coated film was coated with Two sheets were punched out, overlapped so that the coated surfaces faced each other, and pressed at 7 tons to peel off the release film, thereby producing an independent electrolyte layer B1.

[0117] <Preparation of Positive Electrode Active Material Layer C1>

[0118] Nickel-cobalt-aluminate (NCA) (84.7 parts by mass) as a positive electrode active material, a sulfide solid electrolyte (13.4 parts by mass) as a solid electrolyte, a binder (0.6 parts by mass), a conductive aid (1.3 parts by mass) and an appropriate amount of butyl butyrate as a dispersion medium are mixed to prepare a positive electrode composite slurry. The obtained positive electrode composite slurry is coated on an aluminum (Al) foil as a positive electrode collector with a coating gap of 225 μm, pre-dried at 60°C, and formally dried at 165°C for 1 hour to prepare a positive electrode active material layer C1 formed on the Al foil. The design capacity of the positive electrode active material layer C1 is 3.0 mAh / cm 2 , the mass per unit area is 18.7 mg / cm 2 .

[0119] 〈Preparation of lithium metal secondary battery〉

[0120] The composite metal layer A1 is Punch out the positive electrode active material layer C1 to Punching. An electrolyte layer B1 is arranged between the composite metal layer A1 and the positive electrode active material layer C1 to produce a laminated body in which the negative electrode collector layer, the composite metal layer A1, the electrolyte layer B1, the positive electrode active material layer C1, and the positive electrode collector layer are sequentially stacked. Next, the laminated body is contained in a laminated film, vacuum-sealed, and isotropically pressed at 392 MPa by cold isostatic pressing to produce a preparatory lithium metal secondary battery. Among them, aluminum (Al) is used for the positive electrode sheet and nickel (Ni) is used for the negative electrode sheet.

[0121] 〈Formation and electrochemical evaluation of lithium metal secondary battery D1: initial cycle reversible capacity〉

[0122] The prepared lithium metal secondary battery was constrained to 1 MPa using a constant pressure fixture with a spring inserted in it so that the constraining pressure was constant. Next, the prepared lithium metal secondary battery was placed in a constant temperature bath at 60°C and a constant current (current density: 0.15 mA / cm 2 , equivalent to 0.05C)-constant voltage (cut-off current density: 0.03mA / cm 2 , equivalent to 0.01C) test. By charging the prepared lithium metal secondary battery, the gallium and tin contained in the composite metal layer A1 react with the lithium moved from the positive electrode active material layer, so that the gallium and tin are alloyed with lithium, thereby forming a composite alloy layer to obtain a lithium metal secondary battery D1. The initial cycle reversible capacity of the lithium metal secondary battery D1 is 2.37mAh / cm 2 .

[0123] <Electrochemical measurement of lithium metal secondary battery D1: resistance after initial charge and discharge>

[0124] After the initial charge and discharge at 60°C, the resistance of the lithium metal secondary battery D1 was measured by the AC impedance method. The resistance of the lithium metal secondary battery D1 was 108 Ωcm 2 .

[0125] 《Example 2》

[0126] <Production of composite metal layer A2>

[0127] The composite metal layer A2 formed on the SUS foil was produced in the same manner as in Example 1 except that the atomic ratio of gallium to the total of gallium and tin was 20 atomic %. The atomic ratio of gallium to the total of gallium and tin in the obtained composite metal layer A2 was 25 atomic %.

[0128] <Fabrication and electrochemical measurement of lithium metal secondary battery D2>

[0129] Except that the composite metal layer A2 was used instead of the composite metal layer A1, the lithium metal secondary battery D2 was prepared in the same manner as in Example 1. The electrochemical measurement of the lithium metal secondary battery D2 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery D2 are shown in Table 1.

[0130] 《Example 3》

[0131] <Production of composite metal layer A3>

[0132] The composite metal layer A3 formed on the SUS foil was prepared in the same manner as in Example 1 except that the atomic ratio of gallium to the total of gallium and tin was 50 atomic %. The atomic ratio of gallium to the total of gallium and tin in the obtained composite metal layer A3 was 44 atomic %.

[0133] <Surface SEM-EDX observation of composite metal layer A3>

[0134] The surface of the composite metal layer A3 was observed by scanning electron microscopy (SEM) using secondary electron imaging and element mapping using energy dispersive X-ray analysis (EDX) with an applied voltage of 5 kV.

[0135] 〈Fabrication and electrochemical measurement of lithium metal secondary battery D3〉

[0136] A lithium metal secondary battery D3 was prepared in the same manner as in Example 1 except that the composite metal layer A3 was used instead of the composite metal layer A1. The electrochemical measurement of the lithium metal secondary battery D3 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery D3 are shown in Table 1.

[0137] <Cross-sectional SEM-EDX observation of lithium metal secondary battery D3>

[0138] The cross section of the charged lithium metal secondary battery D3 was observed by scanning electron microscopy (SEM) using secondary electron imaging and element mapping using energy dispersive X-ray analysis (EDX) at an applied voltage of 5 kV.

[0139] 《Example 4》

[0140] <Production of composite metal layer A4>

[0141] The composite metal layer A4 formed on the SUS foil was prepared in the same manner as in Example 1 except that the atomic ratio of gallium to the total of gallium and tin was 80 atomic %. The atomic ratio of gallium to the total of gallium and tin in the obtained composite metal layer A4 was 75 atomic %.

[0142] 〈Fabrication and electrochemical measurement of lithium metal secondary battery D4〉

[0143] A lithium metal secondary battery D4 was prepared in the same manner as in Example 1 except that the composite metal layer A4 was used instead of the composite metal layer A1. The electrochemical measurement of the lithium metal secondary battery D4 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery D4 are shown in Table 1.

[0144] Comparative Example 1

[0145] <Production of composite metal layer a1>

[0146] The composite metal layer a1 formed on the SUS foil was prepared in the same manner as in Example 1 except that the atomic ratio of gallium to the total of gallium and tin was 0 atomic %, that is, it was prepared using only tin. The composite metal layer a1 obtained had an atomic ratio of gallium to the total of gallium and tin of 0 atomic %.

[0147] <Fabrication and electrochemical measurement of lithium metal secondary battery d1>

[0148] A lithium metal secondary battery d1 was prepared in the same manner as in Example 1 except that the composite metal layer a1 was used instead of the composite metal layer A1. The electrochemical measurement of the lithium metal secondary battery d1 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery d1 are shown in Table 1.

[0149] 《Comparative Example 2》

[0150] <Production of composite metal layer a2>

[0151] The composite metal layer a2 formed on the SUS foil was produced in the same manner as in Example 1 except that the atomic ratio of gallium to the total of gallium and tin was 100 atomic %, that is, it was produced only with gallium. The atomic ratio of gallium to the total of gallium and tin in the obtained composite metal layer a2 was 100 atomic %.

[0152] <Fabrication and electrochemical measurement of lithium metal secondary battery d2>

[0153] A lithium metal secondary battery d2 was prepared in the same manner as in Example 1 except that the composite metal layer a2 was used instead of the composite metal layer A1. The electrochemical measurement of the lithium metal secondary battery d2 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery d2 are shown in Table 1.

[0154] Table 1 shows the evaluation results of the electrochemical measurements of Examples 1 to 4 and Comparative Examples 1 and 2.

[0155] [Table 1]

[0156]

Table 1

[0157]

[0158] The surface SEM-EDX observation of the composite metal layer A3 showed that a composite body was formed in which gallium surrounded the tin particles. In addition, the cross-sectional SEM-EDX of the lithium metal secondary battery D3 showed that, as for the composite metal layer A3, a lithium-gallium and lithium-tin composite metal layer was formed near the negative electrode collector layer when lithium was inserted during the initial charge.

[0159] Among Examples 1 to 4, the lithium metal secondary battery D4 having a composite alloy layer including a lithium-gallium alloy and a lithium-tin alloy formed by the composite metal layer A4 (Example 4) showed the highest value (2.50 mAh / cm 2 ). When the composite metal layers A2 and A3 (Examples 2 and 3) were used, the reversible capacity of the first cycle was also improved compared with that of tin and gallium. In addition, for the resistance after the first charge and discharge at 60°C, the lithium metal secondary batteries D1 to D4 having a composite alloy layer formed by the composite metal layers A1 to A4 were lower than the lithium metal secondary batteries d1 and d2 having a composite alloy layer formed by the composite metal layers a1 and a2 of tin and gallium.

[0160] It is speculated that a composite alloy layer formed by a composite metal layer including a composite formed in which gallium surrounds tin particles is formed near the negative electrode collector layer, thereby suppressing the interface peeling between the electrolyte layer and the lithium metal layer during lithium detachment, thereby reducing the resistance and increasing the reversible capacity.

[0161] 《Example 5》

[0162] <Production of composite metal layer A5>

[0163] A composite metal layer containing gallium and indium was formed on a stainless steel (SUS) foil as a negative electrode current collector in a manner of 1.0 μm thick by binary evaporation based on an ion plating method, thereby producing a composite metal layer A5 formed on the SUS foil. At this time, the composite metal layer A5 was produced in a manner in which the atomic ratio of gallium to the total of gallium and indium was 10 atomic %. The composite metal layer A5 obtained had an atomic ratio of gallium to the total of gallium and indium of 15 atomic %.

[0164] 〈Fabrication and electrochemical measurement of lithium metal secondary battery D5〉

[0165] A lithium metal secondary battery D5 was prepared in the same manner as in Example 1 except that the composite metal layer A5 was used instead of the composite metal layer A1. The electrochemical measurement of the lithium metal secondary battery D5 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery D5 are shown in Table 2.

[0166] Example 6

[0167] <Production of composite metal layer A6>

[0168] The composite metal layer A6 formed on the SUS foil was produced in the same manner as in Example 5 except that the atomic ratio of gallium to the total of gallium and indium was 20 atomic %. The atomic ratio of gallium to the total of gallium and indium in the obtained composite metal layer A6 was 25 atomic %.

[0169] 〈Fabrication and electrochemical measurement of lithium metal secondary battery D6〉

[0170] A lithium metal secondary battery D6 was prepared in the same manner as in Example 1 except that the composite metal layer A6 was used instead of the composite metal layer A1. The electrochemical measurement of the lithium metal secondary battery D6 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery D6 are shown in Table 2.

[0171] Example 7

[0172] <Production of composite metal layer A7>

[0173] The composite metal layer A7 formed on the SUS foil was prepared in the same manner as in Example 5 except that the atomic ratio of gallium to the total of gallium and indium was 50 atomic %. The atomic ratio of gallium to the total of gallium and indium in the obtained composite metal layer A7 was 43 atomic %.

[0174] <Surface SEM-EDX observation of composite metal layer A7>

[0175] The surface of the composite metal layer A7 was observed by scanning electron microscopy (SEM) using secondary electron imaging and by energy dispersive X-ray analysis (EDX) element mapping with an applied voltage of 5 kV.

[0176] 〈Fabrication and electrochemical measurement of lithium metal secondary battery D7〉

[0177] A lithium metal secondary battery D7 was prepared in the same manner as in Example 1, except that the composite metal layer A7 was used instead of the composite metal layer A1. The electrochemical measurement of the lithium metal secondary battery D7 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery D7 are shown in Table 2.

[0178] Comparative Example 3

[0179] <Production of composite metal layer a3>

[0180] The composite metal layer a3 formed on the SUS foil was prepared in the same manner as in Example 5 except that the atomic ratio of gallium to the total of gallium and indium was 0 atomic %, that is, it was prepared using only indium. The atomic ratio of gallium to the total of gallium and indium in the obtained composite metal layer a3 was 0 atomic %.

[0181] 〈Fabrication and electrochemical measurement of lithium metal secondary battery d3〉

[0182] The lithium metal secondary battery d3 was prepared in the same manner as in Example 1 except that the composite metal layer a3 was used instead of the composite metal layer A1. The electrochemical measurement of the lithium metal secondary battery d3 was carried out in the same manner as in Example 1. The initial cycle reversible capacity and the resistance after the initial charge and discharge of the lithium metal secondary battery d3 are shown in Table 2.

[0183] Table 2 shows the evaluation results of the electrochemical measurements of Examples 5 to 7 and Comparative Examples 2 and 3.

[0184] [Table 2]

[0185] @Table 2】

[0186]

[0187] From SEM-EDX observation of the surface of the composite metal layer A7, it was confirmed that a composite body was formed in which gallium surrounded the indium particles.

[0188] Among Examples 5 to 7, the lithium metal secondary battery D6 having a composite alloy layer including a lithium-gallium alloy and a lithium-indium alloy formed by the composite metal layer A6 (Example 6) showed the highest value (2.41 mAh / cm 2 ). In addition, regarding the resistance after the initial charge and discharge at 60°C, the lithium metal secondary batteries D5 to D7 having a composite alloy layer formed by the composite metal layers A5 to A7 have lower resistance than the lithium metal secondary batteries d2 and d3 having a composite alloy layer formed by the composite metal layers a2 and a3 of indium and gallium.

[0189] It is speculated that a composite alloy layer formed by a composite metal layer including a composite formed in which gallium surrounds indium particles is formed near the negative electrode collector layer, thereby inhibiting interface peeling between the electrolyte layer and the lithium metal layer during lithium detachment, thereby reducing resistance and increasing reversible capacity.

[0190] Although preferred embodiments of the lithium metal secondary battery of the present disclosure are described, it will be appreciated by those skilled in the art that changes may be made without departing from the scope of the patent claims.

Claims

1. A lithium metal secondary battery, which comprises, in sequence, a negative electrode collector layer, a composite alloy layer, a lithium metal layer, an electrolyte layer, a positive electrode active material layer and a positive electrode collector layer, and the composite alloy layer comprises a combination of a lithium-gallium alloy and a lithium-tin alloy and / or a lithium-indium alloy.

2. The lithium metal secondary battery according to claim 1, wherein The composite alloy layer includes a lithium-gallium alloy and a lithium-tin alloy, and the atomic ratio of gallium in the composite alloy layer relative to the total of gallium and tin is 10 to 90 atomic %.

3. The lithium metal secondary battery according to claim 1 or 2, wherein: The composite alloy layer includes a lithium-gallium alloy and a lithium-indium alloy, and the atomic ratio of gallium in the composite alloy layer relative to the total of gallium and indium is 10 to 45 atomic %.

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