All-solid-state lithium-ion secondary battery and method for manufacturing the same

Abstract

The present invention addresses the problem of providing an all-solid-state lithium-ion secondary battery that has excellent charging / discharging characteristics.　The present invention includes at least a negative electrode layer, a separator layer, and a positive electrode layer. The negative electrode layer contains a negative electrode active substance which includes graphite. The separator layer is made of an oxide solid electrolyte. A resistance reduction layer is formed between the negative electrode layer and the separator layer, and the resistance reduction layer is made of a lithium alloy. Alternatively, the present invention includes a substance with which a lithium alloy is formed as a result of a secondary battery operation in which current flows between the negative electrode layer and the positive electrode layer.

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state lithium-ion secondary battery and a method for producing the same. [Background technology]

[0002] High-capacity secondary batteries are used in a wide variety of applications, including electric vehicles including hybrids, as energy sources for electronic devices, and as storage equipment for renewable energy sources such as solar cells. However, in order to realize a low-carbon, smart society, there is a need for secondary batteries with even higher capacities and better charge / discharge characteristics.

[0003] Lithium-ion secondary batteries have a high energy density and utilize a carbon material such as graphite for the negative electrode to store lithium ions, while the positive electrode is made of an oxide of lithium and a transition metal, which suppresses metal deposition during charging and discharging. For these reasons, lithium-ion secondary batteries are highly practical and have become the mainstream of high-capacity secondary batteries. The next generation of lithium-ion secondary batteries is expected to be all-solid-state lithium-ion secondary batteries, which will have even larger capacities and be safer and easier to handle.

[0004] Lithium ion secondary batteries using a negative electrode made of graphite include lithium ion secondary batteries using an organic electrolyte solution and sulfide-type all-solid-state lithium ion secondary batteries using a sulfide solid electrolyte. The organic electrolyte solution can penetrate into the porous graphite anode layer to bond with the graphite anode active material particles over a wide reaction area. Furthermore, the sulfide solid electrolyte can also be easily bonded between the electrolyte particles and between the electrolyte and the active material particles by cold-pressing a mixture of the solid electrolyte particles and the graphite anode active material particles.

[0005] In contrast, oxide-type all-solid-state lithium-ion secondary batteries with high atmospheric stability are fabricated by high-temperature sintering to bond between solid electrolyte particles and between the solid electrolyte and active material particles, as disclosed in Patent Document 1 and Non-Patent Document 1. However, graphite is difficult to sinter, and therefore bonding between the solid electrolyte and active material particles must be achieved by other methods, such as pressure bonding, making it difficult to fabricate a low-resistance anode that can operate at room temperature. A high-resistance anode increases the internal resistance of the battery and adversely affects charge / discharge characteristics. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6686945 [Patent Document 2] Patent No. 6748035 [Non-patent literature]

[0007] [Non-Patent Document 1] Martin Finsterbusch, Timo Danner, Chin-Long Tsai, Sven Uhlenbruck, Arnulf Latz, and Olivier Guillon, ACS Appl. Mater. Interfaces 2018, 10, 22329-22339. [Non-patent document 2] Narumi Ohta, Shin Kimura, Junichi Sakabe, Kazutaka Mitsuishi, Tsuyoshi Ohnishi, and Kazunori Takada, ACS Appl. Energy Mater. 2019, 2, 7005-7008. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide an all-solid-state lithium-ion secondary battery with excellent charge-discharge characteristics and a method for producing the same. [Means for solving the problem]

[0009] The configuration of the present invention to solve the problems is shown below. (Configuration 1) An all-solid-state lithium ion secondary battery having at least a negative electrode layer, a separator layer, and a positive electrode layer, the negative electrode layer includes a negative electrode active material having graphite, the separator layer is made of an oxide solid electrolyte, a low resistance layer is formed between the negative electrode layer and the separator layer, the low resistance layer is made of a lithium alloy or has a substance that forms a lithium alloy when a secondary battery operation is performed in which a current flows between the negative electrode layer and the positive electrode layer. (Configuration 2) 2. The all-solid-state lithium-ion secondary battery according to claim 1, wherein the low resistance layer contains one or more elements selected from the group consisting of gold, silver, platinum, aluminum, tin, indium, germanium, lead, zinc, antimony, magnesium, silicon, cadmium, gallium, tellurium, and bismuth. (Configuration 3) 2. The all-solid-state lithium-ion secondary battery of claim 1, wherein the low resistance layer has a thickness of 1 to 500 nm. (Configuration 4) 2. The all-solid-state lithium-ion secondary battery according to claim 1, wherein the low resistance layer is made of one or more selected from the group consisting of gold, silver, platinum, tin, indium, and silicon. (Configuration 5) 5. The all-solid-state lithium-ion secondary battery according to any one of configurations 1 to 4, wherein the low resistance layer is disposed in contact with the separator layer. (Configuration 6) 6. The all-solid-state lithium-ion secondary battery according to any one of configurations 1 to 5, wherein the low resistance layer is disposed in contact with the negative electrode layer. (Configuration 7) The solid electrolyte contained in the separator layer is a garnet type with high ionic conductivity or a garnet type - similar crystal structure, and the all - solid - state lithium - ion secondary battery according to any one of Configurations 1 to 6. (Configuration 8) The solid electrolyte contained in the separator layer is composed of a composite oxide containing Li and one or more selected from the group consisting of ceramics having a garnet - type structure, a perovskite - type structure, and a LISICON - type structure, and the all - solid - state lithium - ion secondary battery according to any one of Configurations 1 to 7. (Configuration 9) The negative electrode active material is made of graphite, and the all - solid - state lithium - ion secondary battery according to any one of Configurations 1 to 8. (Configuration 10) The negative electrode active material contains graphite and a material capable of occluding less than 10% of lithium ions, and the all - solid - state lithium - ion secondary battery according to any one of Configurations 1 to 9. (Configuration 11) The positive electrode contains a positive electrode active material, The positive electrode active material is LiM 2 , (1-y-x) , 3 , 1 , , 2 , x , (2-k) , z , y , x , 2-x , x , 1 , 1-x , l x Mn 2-x O4 (where M 1 is at least one element selected from the group consisting of Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn, Sb, In, Nb, Mo, W, Y, Ru, and Rh, and 0.01 ≤ x ≤ 0.5), a spinel - type lithium manganese composite oxide represented by x Mn (1-y-x) Ni y M 2 z [[ID=3...]]O (2-k) F l (where M 2 is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr, and W, and 0.8 ≤ x ≤ 1.2, 0 < y < 0.5, 0 ≤ z ≤ 0.5, k + l < 1, −0.1 ≤ k ≤ 0.2, 0 ≤ l ≤ 0.1), a layered compound represented by 1-x M 3 x O2 (where M3 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5), lithium cobalt composite oxide, LiNi 1-x M 4 x O2 (However, M 4 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5), lithium nickel composite oxide, LiM 5 1-x N 1 x PO4 (However, M 5 is at least one element selected from the group consisting of Fe, Mn and Co, and N 1 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5), an olivine-type composite oxide represented by Li4Ti5O 12 11. The all-solid-state lithium-ion secondary battery according to any one of aspects 1 to 10, comprising one or more selected from the group consisting of lithium titanium composite oxides represented by the following formula: (Configuration 12) 12. A method for producing an all-solid-state lithium-ion secondary battery according to any one of Configurations 1 to 11, wherein the low-resistance layer is formed by one or more methods selected from the group consisting of a sputtering method, a vapor deposition method, a coating method, and a foil pasting method. [Effects of the Invention]

[0010] According to the present invention, an all-solid-state lithium-ion secondary battery having excellent charge-discharge characteristics and a method for producing the same are provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a structural explanatory diagram showing a cross-sectional view of the configuration of an all-solid-state lithium ion secondary battery of the present invention. [Figure 2] FIG. 1 is a structural explanatory diagram showing, in cross section, the configuration of an all-solid-state lithium ion half cell (hereinafter referred to as half cell) of an embodiment. [Figure 3] This is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 1 (Example 1). Here, since the explanation is from the viewpoint of the negative electrode of the whole battery, the reaction of inserting lithium ions into graphite, which is the test electrode active material, is called the charge reaction, and the reaction of desorbing lithium ions from graphite, which is the test electrode active material, is called the discharge reaction. [Figure 4] FIG. 1 is an AC impedance spectrum diagram of the half cell obtained in Example 1 (Example 1) after the first charge. [Figure 5] FIG. 2 is a characteristic diagram showing the initial charge characteristics of the half cell obtained in Example 2 (Example 2). [Figure 6] FIG. 2 is a diagram showing the X-ray diffraction pattern of the half cell obtained in Example 2 (Example 2) after the first charge. [Figure 7] FIG. 1 is a characteristic diagram showing the initial charge / discharge of a half cell obtained in Example 3 (Example 3). [Figure 8] FIG. 10 is a characteristic diagram showing the battery capacity versus the number of charge / discharge cycles of the half-cell obtained in Example 3 (Example 3). [Figure 9] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half cell obtained in Example 4 (Example 4). [Figure 10] FIG. 1 is an AC impedance spectrum diagram of the half cell obtained in Example 4 (Example 4) after the first charge. [Figure 11] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half cell obtained in Example 5 (Example 5). [Figure 12] FIG. 1 is an AC impedance spectrum diagram of the half cell obtained in Example 5 (Example 5) after the first charge. [Figure 13] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half cell obtained in Example 6 (Example 6). [Figure 14] FIG. 1 is an AC impedance spectrum diagram of the half cell obtained in Example 6 (Example 6) after the first charge. [Figure 15] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half cell obtained in Example 7 (Example 7). [Figure 16] FIG. 1 is an AC impedance spectrum diagram of the half cell obtained in Example 7 (Example 7) after the first charge. [Figure 17] FIG. 1 is a characteristic diagram showing the initial charge characteristics of the half cell obtained in Comparative Example 1 (Example 8). [Figure 18] FIG. 1 is an AC impedance spectrum diagram of the half cell obtained in Comparative Example 1 (Example 8) after the first charge. [Figure 19] This is a characteristic diagram showing the initial charge characteristics of a half-cell obtained in Example 9. Since the explanation is given here from the perspective of the negative electrode of the whole cell, the reaction of inserting lithium ions into graphite, which is the test electrode active material, is referred to as the charge reaction, and the reaction of desorbing lithium ions from graphite, which is the test electrode active material, is referred to as the discharge reaction. [Figure 20] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 9, which is an embodiment, after the first charge. [Figure 21] FIG. 1 shows an X-ray diffraction pattern of the half-cell obtained in Example 9 after the first charge. [Figure 22] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 10, which is an embodiment. [Figure 23] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 10 after the first charge. [Figure 24] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 11, which is an embodiment. [Figure 25] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 11 after the first charge. [Figure 26] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 12, which is an embodiment. [Figure 27] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 12 after the first charge. [Figure 28] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 13, which is an embodiment. [Figure 29] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 13 after the first charge. [Figure 30] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 14, which is an embodiment. [Figure 31] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 14, which is an embodiment, after the first charge. [Figure 32] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 15, which is an embodiment. [Figure 33] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 15 after the first charge. [Figure 34] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 16, which is an embodiment. [Figure 35] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 16 after the first charge. [Figure 36] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 17, which is an embodiment. [Figure 37] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 17 after the first charge. [Figure 38] FIG. 10 is a characteristic diagram showing the initial charge characteristics of the half-cell obtained in Example 18, which is an embodiment. [Figure 39] FIG. 10 is an AC impedance spectrum diagram of the half-cell obtained in Example 18, which is an embodiment, after the first charge. [Figure 40] FIG. 1 shows an X-ray diffraction pattern of the half-cell obtained in Example 18 after the first charge. [Figure 41] 1 is a diagram showing the element distribution in the depth direction of the negative electrode layer obtained in Example 19, which is an embodiment of the present invention, in which the horizontal axis represents the sputtering time (seconds) and the vertical axis represents the intensity. [Figure 42] 1 is a diagram showing the element distribution in the depth direction of the negative electrode layer obtained in Example 20. The horizontal axis represents the sputtering time (seconds), and the vertical axis represents the intensity. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description, AB means A or more and B or less.

[0013] <Battery structure> As shown in FIG. 1 , the all-solid-state lithium-ion secondary battery 101 of this embodiment includes a negative electrode current collector 11, a negative electrode active material layer 12, a low-resistance layer 13, a separator layer 15, a positive electrode active material layer 16, and a positive electrode current collector 17. Here, the negative electrode current collector 11 and the negative electrode active material layer 12 form a negative electrode (negative electrode layer) 14, and the positive electrode active material layer 16 and the positive electrode current collector 17 form a positive electrode (positive electrode layer) 18. The negative electrode active material layer 12 and the negative electrode current collector 11 may not be separated, and the negative electrode active material layer 12 may also function as the negative electrode current collector 11. Furthermore, the positive electrode active material layer 16 and the positive electrode current collector 17 may not be separated, and the positive electrode active material layer 16 may also function as the positive electrode current collector 17.

[0014] The negative electrode current collector 11 and the positive electrode current collector 17 (hereinafter, both are also referred to as collectors) are electrodes intended to mediate the movement of electrons from one surface in contact with the positive electrode active material layer 16 (the surface where the positive electrode current collector 17 is in contact with the positive electrode active material layer 16 according to FIG. 1) to the other surface in contact with the negative electrode active material layer 12 (the surface where the negative electrode current collector 11 is in contact with the negative electrode active material layer 12 according to FIG. 1), and are not particularly limited as long as they are made of conductive materials, and metals and conductive resins can be used.

[0015] Specifically, the electrodes may include electrodes made of a metal selected from the group consisting of copper (Cu), tungsten (W), aluminum (Al), nickel (Ni), iron (Fe), titanium (Ti), gold (Au), silver (Ag), platinum (Pt), and palladium (Pd). Specifically, the negative electrode current collector 11 and the positive electrode current collector 17 may be electrodes made of a metal selected from this group, an alloy containing a metal selected from this group, or a compound of a metal selected from this group with carbon (C), nitrogen (N), or the like. Stainless steel or a foil with a metal surface coated with aluminum may also be used. Among these, aluminum, stainless steel, copper, and nickel are preferred from the viewpoints of electronic conductivity, battery operating potential, and applicability to sputtering, which is inexpensive and easy to handle.

[0016] A preferred conductive resin is a non-conductive polymer material with a conductive filler added. Examples of non-conductive polymer materials include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide (PI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), and polystyrene (PS). Examples of the conductive filler include one or more metals selected from the group consisting of nickel (Ni), titanium (Ti), aluminum (Al), copper (Cu), platinum (Pt), chromium (Cr), iron (Fe), zinc (Zn), tin (Sn), indium (In) and antimony (Sb), alloys containing these metals, metal compounds, or one or more selected from the group consisting of acetylene black, carbon nanofibers, carbon nanotubes, carbon nanohorns, carbon nanoballoons and fullerenes.

[0017] The negative electrode active material layer 12 is preferably made of graphite or a material containing graphite as a main component, and more preferably made of a material containing graphite as a main component. The negative electrode active material layer 12 is preferably made of graphite. Graphite is excellent in terms of improving the energy density of the battery, ease of production, and cost reduction. Here, "mainly composed of graphite" means that the material contains 90% or more but less than 100% graphite by molar ratio. The material added to the graphite is a material capable of absorbing lithium ions (i.e., a material capable of absorbing), and examples thereof include materials containing silicon and tin. When the negative electrode active material layer 12 is made of graphite and silicon, the molar ratio may be, for example, 95% graphite and 5% silicon.

[0018] The low-resistance layer 13 is a layer made of a material containing a metal that can be alloyed with lithium (Li) (i.e., a metal that can be alloyed). For example, it is a layer made of a lithium alloy, or a layer that becomes a lithium alloy through secondary battery operation (charge / discharge operation), and the presence of the low-resistance layer 13 makes it possible to reduce the electrical resistance between the negative electrode active material layer 12 and the separator layer 15 (at the interface if they are in contact with each other). When the electrical resistance between the negative electrode active material layer 12 and the separator layer 15 is reduced, the internal resistance of the secondary battery also decreases, improving the charge / discharge characteristics and increasing the electrical capacity.

[0019] Specific examples of materials for the low resistance layer 13 include materials containing one or more elements selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), aluminum (Al), tin (Sn), indium (In), germanium (Ge), lead (Pb), zinc (Zn), antimony (Sb), magnesium (Mg), silicon (Si), cadmium (Cd), gallium (Ga), tellurium (Te), and bismuth (Bi). In particular, one or more elements selected from the group consisting of gold, silver, platinum, tin, indium, and silicon are preferably used because of their stability and ease of handling. Furthermore, the shape of the material of the low resistance layer 13 (specifically, a material containing one or more elements selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), aluminum (Al), tin (Sn), indium (In), germanium (Ge), lead (Pb), zinc (Zn), antimony (Sb), magnesium (Mg), silicon (Si), cadmium (Cd), gallium (Ga), tellurium (Te), and bismuth (Bi), and particularly preferably one or more elements selected from the group consisting of gold, silver, platinum, tin, indium, and silicon) may be such that it is in contact with the separator layer 15 so as to achieve the effects of the present invention. Therefore, the material is not limited to a layered structure (specifically, a structure in which particles of the material are continuously aligned and fixed on the separator layer 15, forming a thin sheet-like film in contact with the separator layer 15) so long as the material is in contact with the separator layer 15 so as to achieve the effects of the present invention. For example, the material may be in a shape in which particles of the material are discontinuously aligned and fixed on the separator layer 15, adhering to the separator layer. The low-resistance layer 13 is preferably layered. This is because a layered structure can increase the contact area between the separator layer 15 and the negative electrode layer 14 during charge / discharge operations, thereby reducing the resistance of the interface between them and improving charge / discharge characteristics. Furthermore, when the thickness of the layered structure is calculated from the weight of the material used, the thickness is preferably 1 to 500 nm, more preferably 5 to 300 nm, and even more preferably 10 to 260 nm. If the thickness is too thin, a continuous layered film will not form, and if it is too thick, material costs and process costs will increase. Therefore, the thickness is preferably within the above range.

[0020] The low resistance layer 13 is preferably disposed in contact with the separator layer 15, and is preferably disposed in contact with the negative electrode layer 14, particularly the negative electrode active material layer 12. This is because when the low resistance layer 13 is in contact with these layers, the resistance is further reduced, and the contact further improves the reliability and stability of the secondary battery operation.

[0021] The low-resistance layer 13 can be formed by one or more methods selected from the group consisting of sputtering, vapor deposition methods such as electron beam vapor deposition and thermal evaporation, coating methods, and foil lamination methods. Sputtering and vapor deposition methods are commonly used industrially, and the coating methods and foil lamination methods are easy to handle because they do not require a vacuum environment. The low-resistance layer 13 is designed to reduce resistance across the entire interface, so it has high tolerance for defects such as local pinholes (in other words, it is less susceptible to the effects of such defects). For this reason, low-cost methods such as foil lamination can be used for the low-resistance layer 13.

[0022] The separator layer 15 is a layer that functions as a separator for the all-solid-state lithium ion secondary battery, and contains or is made of an oxide solid electrolyte. The oxide solid electrolyte may be a highly ion-conductive garnet-type electrolyte or an electrolyte having a garnet-like crystal structure. Specific examples of such materials include Li7La3Zr2O 12 , Li 7-x La3Zr 2-x Ta x O 12 (where x is between 0 and 2), Li 7-3x La3Zr2Al x O 12 (where x is between 0 and 0.5), Li 7-x La3Zr 2-x Nb x O 12 (where x is between 0 and 2) and Li 7-x-3y La3Zr 2-x Ta x Al y O 12 (where x is 0 or more and 2 or less, and y is 0 or more and 0.5 or less). The solid electrolyte contained in the separator layer 15 may be one or more selected from the group consisting of composite oxides containing lithium (Li) and ceramics having a garnet structure, a perovskite structure, and a LISICON structure. Specific examples of such materials include LISICON, NASICON, PEO, LIPON, PVDF, LiN, LiP, LiI, LiBr, LiCl, LiF, and Li. 0.5 TiO3, Li2S-SiS2-Li3PO4, Lithium nitride, doped Li3N, Li2S-SiS2-Li3PO4, Li 14 Zn(GeO4)4, Li-β-alumina, Li 3.6 Si 0.6 P 0.4 O4, PEO-LiClO4, LiN(CF3SO2)2 / (CH2CH2O)8, Li7La3Zr2O doped with one or more elements selected from the group consisting of Al, Ga, Nb, Ta, Ca, and Sr 12 , Li3BO3.

[0023] There are no particular limitations on the positive electrode active material layer 16 as long as it is a positive electrode active material containing lithium, but a representative example is a lithium-containing composite metal oxide. Specific materials for the positive electrode active material layer 16 include LiM 1 x Mn 2-x O4 (However, M 1 is at least one element selected from the group consisting of Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn, Sb, In, Nb, Mo, W, Y, Ru, and Rh, and 0.01≦x≦0.5), a spinel-type lithium manganese composite oxide represented by x Mn (1-y-x) Ni y M 2 z O (2-k) F l (However, M 2is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr, and W, and is represented by 0.8 ≦ x ≦ 1.2, 0 < y < 0.5, 0 ≦ z ≦ 0.5, k + l < 1, -0.1 ≦ k ≦ 0.2, 0 ≦ l ≦ 0.1), and a layered compound, LiCo 1-x M 3 x O2 (where M 3 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and is represented by 0 ≦ x ≦ 0.5), and a lithium cobalt composite oxide, LiNi 1-x M 4 x O2 (where M 4 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and is represented by 0 ≦ x ≦ 0.5), and a lithium nickel composite oxide, LiM 5 1-x N 1 x PO4 (where M 5 is at least one element selected from the group consisting of Fe, Mn, and Co, and N 1 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and is represented by 0 ≦ x ≦ 0.5), and an olivine-type composite oxide, Li4Ti5O 12 represented by a lithium titanium composite oxide selected from the group consisting of can be mentioned one or more.

[0024] With the battery having the above structure, as a all-solid-state lithium-ion secondary battery according to an embodiment of the present invention, a all-solid-state lithium-ion secondary battery 101 with a small internal resistance and excellent charge-discharge characteristics is provided.

[0025] <Manufacturing method of battery> First, a solid electrolyte is prepared by sintering a solid electrolyte material using a hot press sintering method or the like to form the separator layer 15. The sintering temperature can be, for example, 800°C or higher and 1200°C or lower.

[0026] Next, the low resistance layer 13 is formed on one of the main surfaces (first main surface) of the separator layer 15. As described above, the formation method can be one or more methods selected from the group consisting of sputtering, vapor deposition methods such as electron beam vapor deposition and thermal vapor deposition, coating methods, and foil lamination methods. In this application, the main surface of the separator layer refers to the surface in contact with the low resistance layer, the positive electrode active material layer, or the counter electrode.

[0027] Thereafter, a positive electrode current collector 17 coated with a positive electrode active material layer 16 and a negative electrode current collector 11 coated with a negative electrode active material layer 12 are fabricated. The materials described in the section on the battery structure may be used for the positive electrode active material layer 16, the positive electrode current collector 17, the negative electrode active material layer 12, and the negative electrode current collector 11. Examples of deposition methods include lamination, sputtering, vapor deposition, CVD (Chemical Vapor Deposition), spray coating, blade coating, slit die coating, and roll coating.

[0028] Thereafter, the separator layer 15 is placed on the negative electrode current collector 11 on which the negative electrode active material layer 12 is deposited, with the negative electrode active material layer 12 facing the low resistance layer 13. Furthermore, the positive electrode current collector 17 on which the positive electrode active material layer 16 is deposited is placed on a main surface of the separator layer 15 opposite to the first main surface on which the low resistance layer 13 is disposed (this main surface is referred to as the second main surface in the present application to distinguish it from the first main surface). The negative electrode current collector 11, the negative electrode active material layer 12, the low resistance layer 13, the separator layer 15, the positive electrode active material layer 16, and the positive electrode current collector 17 are bundled and pressed together, and then the resultant is housed in a housing (not shown) to produce an all-solid-state lithium-ion secondary battery 101 (FIG. 1).

[0029] The above manufacturing method makes it possible to provide the all-solid-state lithium-ion secondary battery 101 having the above structure. The all-solid-state lithium-ion secondary battery 101 is characterized by low internal resistance and excellent charge / discharge characteristics. [Example]

[0030] In the examples, in order to eliminate the influence of the positive electrode used and to investigate purely the interfacial bonding with the graphite negative electrode active material, an all-solid-state lithium-ion half-cell 102 ( FIG. 2 ) was fabricated using graphite for the test electrode 22, a LiLaZrTaO sintered body for the separator layer 25, and lithium foil for the counter electrode 26, and its characteristics were evaluated. Eight types of samples were fabricated: Examples 1 to 7 and Comparative Example 1. The low resistance layer 23 was made of gold (Au) for Examples 1 to 3, indium (In) for 4, silver (Ag) for 5, platinum (Pt) for 6, and silicon (Si) for 7, while no low resistance layer 23 was provided in Comparative Example 1. Here, we first summarize the sample preparation methods, and then summarize the characteristics. In this application, examples and comparative examples are sometimes simply referred to as "examples" for convenience. In this case, examples 1 to 7 will be referred to as examples 1 to 7, and comparative example 1 will be referred to as example 8.

[0031] [Sample preparation] <Example 1> (solid electrolyte) The separator layer 25 (solid electrolyte) is made of Li with a diameter of 10 mm and a thickness of 2 mm. 6.6 La3Zr 1.6 Ta 0.4 O 12 A sintered body (manufactured by Toshima Manufacturing Co., Ltd.) was used.

[0032] (Graphite dispersion) The graphite dispersion used was a dispersion prepared by dispersing 450 mg of graphite powder (manufactured by Imerys, KS6, average diameter 4.4 μm) in 30 g of 99.5% ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0033] (preparation process) First, a small spray coating device (AV-8 model, manufactured by Acing Technologies) was used to spray the graphite dispersion onto an unpolished SUS304 disk with a diameter of 10 mm and a thickness of 0.5 mm, with a coating amount of 1.77 mg / cm. 2 A test electrode 22 made of graphite was obtained. Next, a compact sputtering device (SC-701MkII ADVANCE, manufactured by Sanyu Electronics Co., Ltd.) was used to deposit a sintered body (diameter 10 mm, thickness 2 mm) of solid electrolyte that forms the separator layer 25 on both main surfaces of the body with a weight of 0.29 mg / cm. 2 Here, the gold layer on the side in contact with the test electrode 22 corresponds to the low resistance layer 23. Thereafter, a 50 μm thick lithium (Li) foil (manufactured by Honjo Chemical Co., Ltd.) was prepared as a counter electrode 26, and the lithium foil was placed on one surface of the solid electrolyte 25 coated with a gold layer. Subsequently, a test electrode 22 made of graphite was placed on the other surface of the solid electrolyte 25 coated with a gold layer, which would become the low resistance layer 23. Then, a test electrode 22 made of graphite, a solid electrolyte 25 coated on both sides with gold layers, and a counter electrode 26 (Li foil) were combined to obtain a primary assembly. In Example 1 (Example 1), the SUS304 used as the spray-coated substrate was used as the current collector 21, and a new unpolished SUS304 disk with a diameter of 10 mm and a thickness of 0.5 mm was used as the current collector 27, which was placed on one surface of the counter electrode 26 (Li foil).

[0034] (Pressure process) The obtained primary assembly was screwed with a torque of 2.0 Nm to apply a confining pressure of 40 MPa in the stacking direction, thereby obtaining a half-cell 102 of Example 1.

[0035] <Example 2 (Example 2) and Example 3 (Example 3)> Half-cells 102 of Example 2 (Example 2) and Example 3 (Example 3) were obtained in the same manner as in Example 1 (Example 1), except that the amount of graphite powder applied in Example 1 (Example 1) was changed as shown in Table 1.

[0036] [Table 1]

[0037] <Example 4> In Example 1 (Example 1), only one surface of the sintered body 25 of the solid electrolyte on which the lithium foil serving as the counter electrode 26 was disposed was coated with a gold layer, and the other surface of the sintered body 25 of the solid electrolyte on which the test electrode 22 made of graphite was disposed, i.e., the surface facing the test electrode 22, was coated with a gold layer having a weight of 0.17 mg / cm 2 A half-cell 102 of Example 4 (Example 4) was obtained in the same manner as in Example 1 (Example 1), except that the low resistance layer 23 of Example 4 (Example 4) was coated with an indium (In) layer and the amount of graphite powder applied was changed as shown in Table 1. Therefore, the low resistance layer 23 of Example 4 (Example 4) was formed of an indium layer.

[0038] <Example 5> In Example 1 (Example 1), only one surface of the sintered body 25 of the solid electrolyte on which the lithium foil serving as the counter electrode 26 was disposed was coated with a gold layer, and the other surface of the sintered body 25 of the solid electrolyte on which the test electrode 22 made of graphite was disposed, i.e., the surface facing the test electrode 22, was coated with a gold layer having a weight of 0.27 mg / cm. 2 A half-cell 102 of Example 5 (Example 5) was obtained in the same manner as in Example 1 (Example 1), except that the low resistance layer 23 of Example 5 (Example 5) was coated with a silver (Ag) layer of 1000 kJ / cm 2 and the amount of graphite powder applied was changed as shown in Table 1. Therefore, the low resistance layer 23 of Example 5 (Example 5) was formed of a silver layer.

[0039] Example 6 In Example 1 (Example 1), only one surface of the sintered body 25 of the solid electrolyte on which the lithium foil serving as the counter electrode 26 was disposed was coated with a gold layer, and the other surface of the sintered body 25 of the solid electrolyte on which the test electrode 22 made of graphite was disposed, i.e., the surface facing the test electrode 22, was coated with a gold layer having a weight of 0.41 mg / cm 2 A half-cell 102 of Example 6 (Example 6) was obtained in the same manner as in Example 1 (Example 1), except that the low resistance layer 23 of Example 6 (Example 6) was coated with a platinum (Pt) layer and the amount of graphite powder applied was changed as shown in Table 1. Therefore, the low resistance layer 23 of Example 6 (Example 6) was formed of a platinum layer.

[0040] <Example 7> In Example 1 (Example 1), only one surface of the sintered body 25 of the solid electrolyte on which the lithium foil serving as the counter electrode 26 was disposed was coated with a gold layer, and the other surface of the sintered body 25 of the solid electrolyte on which the test electrode 22 made of graphite was disposed, i.e., the surface facing the test electrode 22, was coated with a gold layer having a weight of 0.06 mg / cm 2 A half-cell 102 of Example 7 (Example 7) was obtained in the same manner as in Example 1 (Example 1), except that the low resistance layer 23 of Example 7 (Example 7) was coated with a silicon layer of 1000 kJ / cm 2 and the amount of graphite powder applied was changed as shown in Table 1. Therefore, the low resistance layer 23 of Example 7 (Example 7) was formed of a silicon layer.

[0041] <Comparative Example 1 (Example 8)> A half cell of Comparative Example 1 (Example 8) was obtained in the same manner as in Example 1 (Example 1), except that only one surface of the sintered body 25 of the solid electrolyte on which the counter electrode 26 was disposed was coated with a gold layer and the amount of graphite powder applied was changed as shown in Table 1. Therefore, Comparative Example 1 (Example 8) does not have the low-resistance layer 23.

[0042] [Characteristics evaluation] (First charge test) Using the half-cells obtained in Example 1 (Example 1), Example 2 (Example 2), Examples 4 to 6 (Examples 4 to 6), and Comparative Example 1 (Example 8), a CC charging test was performed at a current value of 0.05 C until the voltage reached 0.01 V on a lithium metal basis. The initial charge curves obtained as a result of the test are shown in Figures 3, 5, 9, 11, 13 and 17, respectively. Using the half-cell obtained in Example 7 (Example 7), CC charging was performed for 12 hours and 10 hours at currents of 0.0005C and 0.005C, respectively. The half-cell was then CC charged at a current of 0.05C until the voltage reached 0V relative to lithium metal, and then a CV charging test was performed at 0V for 10 hours. The initial charge curve obtained from the test is shown in Figure 15. The test environment was an argon atmosphere at room temperature of approximately 25°C under atmospheric pressure.

[0043] (First charge test results) Table 2 shows the test results for the initial charge capacity.

[0044] [Table 2]

[0045] The weight of graphite contained in the test electrode 22 made of graphite incorporated in the half-cells obtained in Example 1 (Example 1), Example 2 (Example 2), and Comparative Example 1 (Example 8) was all about 1 mg / cm 2 However, Example 1 (Example 1) and Example 2 (Example 2), in which test electrode 22 made of graphite is arranged on the surface of solid electrolyte 25 coated with a gold layer, which is low-resistance layer 23, show a decrease of about 0.3 to 0.4 mAh / cm compared to Comparative Example 1 (Example 8), in which test electrode 22 made of graphite is arranged on the surface of solid electrolyte 25 that is not coated with a gold layer (no low-resistance layer 23 is arranged). 2 A large charging capacity was also obtained. The weights of graphite contained in the test electrodes 22 made of graphite incorporated in the half-cells obtained in Example 4 (Example 4), Example 5 (Example 5), Example 6 (Example 6), and Comparative Example 1 (Example 8) were also almost the same. However, in Example 4 (Example 4), Example 5 (Example 5), and Example 6 (Example 6), in which the test electrodes 22 made of graphite were arranged on the surface of the solid electrolyte 25 coated with an indium layer, a silver layer, or a platinum layer, respectively, the electric current was about 0.2 to 0.3 mAh / cm compared to Comparative Example 1 (Example 8), in which the test electrodes 22 made of graphite were arranged on the surface of the solid electrolyte 25 that was not coated with these layers. 2 That is, even when an indium layer, a silver layer, or a platinum layer was provided as the low resistance layer 23, the charge capacity was about 0.2 to 0.3 mAh / cm compared to when the low resistance layer 23 was not provided. 2 A large charging capacity was also obtained. Furthermore, the weight of graphite contained in test electrode 22 made of graphite incorporated in the half-cells obtained in Example 7 (Example 7) and Comparative Example 1 (Example 8) was also almost the same. However, in Example 7 (Example 7), test electrode 22 made of graphite was placed on the surface of solid electrolyte 25 coated with a silicon layer, which was low-resistance layer 23, and CC charging was performed until the voltage reached 0 V relative to lithium metal, and CV charging was further performed for 10 hours. In Example 7 (Example 7), test electrode 22 made of graphite was placed on the surface of solid electrolyte 25 not coated with a silicon layer, and CC charging was performed until the voltage reached 0 V relative to lithium metal, i.e., in Comparative Example 1 (Example 8) in which low-resistance layer 23 was not placed, the electric current consumption was about 0.5 mAh / cm 2 A large charging capacity was also obtained.

[0046] (Method for measuring AC impedance after the first charging test) The half-cells obtained in Example 1 (Example 1), Example 4 (Example 4), Example 5 (Example 5), Example 6 (Example 6), Example 7 (Example 7) and Comparative Example 1 (Example 8) were subjected to the above-mentioned initial charging test, and then AC impedance measurements were performed at an applied AC voltage of 10 mV based on the natural potential in the frequency range of 10 mHz to 1 MHz. The AC impedance spectra obtained as a result of the test are shown in Figures 4, 10, 12, 14, 16, and 18. The test environment was an argon atmosphere at room temperature of about 25°C under atmospheric pressure.

[0047] (AC impedance measurement results after the first charging test) Table 3 shows the AC impedance measurement results after the initial charging test.

[0048] [Table 3]

[0049] From the AC impedance spectra obtained after the initial charge of the half-cells obtained in Example 1 (Example 1) and Comparative Example 1 (Example 8), in the structure without a gold layer sandwiched between them, the interfacial resistance of the test electrode 22 made of solid electrolyte separator layer 25 and graphite was 3188 Ω cm 2On the other hand, in the structure in which the low resistance layer 23 made of a gold layer is sandwiched, the interface resistance is 31 Ω·cm 2 It was found that the interfacial resistance was reduced to 0.05. The half-cell obtained by employing the interface structure of Example 1 (Example 1) had significantly lower interfacial resistance and internal cell resistance, which improved the charge / discharge characteristics and the energy density of the battery. Furthermore, from the AC impedance spectra obtained after the initial charging of the half-cells obtained in Example 4 (Example 4), Example 5 (Example 5), Example 6 (Example 6), and Example 7 (Example 7), it was found that the interfacial resistance was 180 Ω cm even in the structures in which an indium (In) layer, a silver (Ag) layer, a platinum (Pt) layer, and a silicon (Si) layer were sandwiched. 2 , 330 Ω·cm 2 , 955 Ω·cm 2 and 67 Ω·cm 2 and the interface resistance (3188 Ω cm) of the half cell obtained in Comparative Example 1 (Example 8). 2 ), it was confirmed that the interfacial resistance of the structure was also reduced in the same way as in the case of the structure sandwiching the gold layer.

[0050] (X-ray diffraction measurement after the first charging test) After an initial charge test was performed using half-cell 102 obtained in Example 2 (Example 2), half-cell 102 was disassembled in a glove box under an argon gas atmosphere, and the surface of the graphite layer that had been in contact with current collector 21 was facing the X-ray irradiation side, and the half-cell was sealed in an X-ray diffraction atmosphere separator (manufactured by Rigaku Corporation) (argon gas atmosphere). X-ray diffraction measurement was performed using an X-ray diffractometer (manufactured by Rigaku Corporation, Miniflex600) in the diffraction angle range of 20° to 30° (2θ). The X-ray diffraction pattern obtained as a result of the test is shown in FIG.

[0051] (X-ray diffraction measurement results after the first charging test) The X-ray diffraction pattern of the half-cell 102 obtained in Example 2 (Example 2) after the initial charge revealed that the gold layer reacted with lithium to form an alloy Li3Au. This indicates that the volume expansion during the alloying reaction contributes significantly to the reduction in interfacial resistance observed in the structure in which the gold layer (low-resistance layer 23) is sandwiched between the test electrode 22 and the separator layer 25. Furthermore, it was found that the reduction in interfacial resistance allows lithium to be inserted into the graphite contained in the graphite layer near the current collector from stage 2 to stage 1 of charge, even during CC charging at room temperature using a current value of 0.05 C.

[0052] (Charge-discharge cycle test) Using the half-cell 102 obtained in Example 3 (Example 3), a charge-discharge test was conducted at a current value of 0.05 C in a voltage range of 0.01 to 1.2 V vs. lithium metal. The initial charge-discharge curve obtained from the test is shown in Figure 7, and the battery capacity as a function of the number of charge-discharge cycles up to 20 cycles is shown in Figure 8. The test environment was an argon atmosphere at room temperature of approximately 25°C under atmospheric pressure.

[0053] (Charge / discharge cycle test results) The initial charge-discharge curve of the half-cell 102 obtained in Example 3 (Example 3) showed that no significant hysteresis was observed in the charge-discharge curve, and the initial Coulombic efficiency was also found to be greater than 70%. High reversibility was observed in the second and subsequent cycles, and no significant capacity loss was observed. This indicates that the half-cell 102 obtained using the interface structure of the present disclosure exhibits not only high energy density but also high stability.

[0054] Furthermore, as shown below, Examples 9 to 20 were added. 12 types of samples were fabricated for the added Examples, Examples 9 to 20. In the added Examples, as in the above Examples (i.e., Examples 1 to 8), in order to eliminate the influence of the positive electrode used and to investigate purely the interfacial bonding with the graphite negative electrode active material, an all-solid-state lithium-ion half-cell 102 ( FIG. 2 ) was fabricated using graphite (including those mainly composed of graphite) for test electrode 22, a LiLaZrTaO sintered body for separator layer 25, and lithium foil for counter electrode 26, and its characteristics were evaluated. The low resistance layer 23 was made of gold (Au) in Examples 9 and 10, and Examples 17 to 20, indium (In) in Examples 11 and 12, silver (Ag) in Examples 13 and 14, and platinum (Pt) in Examples 15 and 16. In Example 17, no test electrode 22 was placed, and in Example 18, a test electrode 22 made of graphite and silicon was incorporated to fabricate a prototype half-cell, and its characteristics were evaluated. Examples 19 and 20 are negative electrodes fabricated to evaluate the element distribution in the thickness direction of the test electrode 22. In Example 19, the test electrode 22 is made of graphite, and in Example 20, it is made of graphite and silicon. Here, as in the above examples (i.e., Examples 1 to 8), the sample preparation methods will be summarized first, followed by a summary of the properties. In this case, for comparison, Example 3 (i.e., Example 3) and Example 8 (i.e., Comparative Example 1) described in the above examples will also be used as appropriate.

[0055] [Sample preparation] <Example 9> (solid electrolyte) The separator layer 25 (solid electrolyte) is made of Li with a diameter of 10 mm and a thickness of 2 mm. 6.6 La3Zr 1.6 Ta 0.4 O 12 A sintered body (manufactured by Toshima Manufacturing Co., Ltd.) was used.

[0056] (Graphite dispersion) The graphite dispersion used was a dispersion prepared by dispersing 450 mg of graphite powder (manufactured by Imerys, KS6, average diameter 4.4 μm) in 30 g of 99.5% ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0057] (preparation process) First, a small spray coating device (AV-8 model, manufactured by Acing Technologies) was used to spray the graphite dispersion onto an unpolished SUS304 disk with a diameter of 10 mm and a thickness of 0.5 mm, with a coating amount of 1.231 mg / cm. 2 A test electrode 22 made of graphite was obtained. Next, a compact sputtering device (SC-701MkII ADVANCE, manufactured by Sanyu Electronics Co., Ltd.) was used to deposit a sintered body (diameter 10 mm, thickness 2 mm) of solid electrolyte that forms the separator layer 25 on both main surfaces of the body with a weight of 0.29 mg / cm. 2 Here, the gold layer on the side in contact with the test electrode 22 corresponds to the low resistance layer 23. Therefore, the low resistance layer 23 of Example 9 is formed of a gold layer with a thickness of 150 nm. Thereafter, a 50 μm thick lithium (Li) foil (manufactured by Honjo Chemical Co., Ltd.) was prepared as a counter electrode 26, and the lithium foil was placed on one surface of the solid electrolyte 25 coated with a gold layer. Subsequently, a test electrode 22 made of graphite was placed on the other surface of the solid electrolyte 25 coated with a gold layer, which would become the low resistance layer 23. Then, a test electrode 22 made of graphite, a solid electrolyte 25 coated on both sides with gold layers, and a counter electrode 26 (Li foil) were combined to obtain a primary assembly. In Example 9, the SUS304 used for the spray-coated substrate was used as the current collector 21, and a new unpolished SUS304 disk with a diameter of 10 mm and a thickness of 0.5 mm was used as the current collector 27, placed on one surface of the counter electrode 26 (Li foil).

[0058] (Pressure process) The obtained primary assembly was screwed with a torque of 2.0 Nm to apply a confining pressure of 40 MPa in the stacking direction, thereby obtaining a half-cell 102 of Example 9.

[0059] [Table 4]

[0060] <Example 10> In Example 9, the surface facing the test electrode 22 made of graphite was coated with a material having a weight of 0.05 mg / cm 2 A half-cell 102 of Example 10 was obtained in the same manner as in Example 9, except that the graphite powder was coated with a gold (Au) layer of 26 nm and the amount of graphite powder applied was changed as shown in Table 4. Therefore, the low resistance layer 23 of Example 10 was formed of a gold layer with a thickness of 26 nm.

[0061] [Table 5]

[0062] <Example 11> In Example 9, only one surface of the sintered body 25 of the solid electrolyte on which the lithium foil serving as the counter electrode 26 was placed was coated with a gold layer, and the other surface of the sintered body 25 of the solid electrolyte on which the test electrode 22 made of graphite was placed, i.e., the surface facing the test electrode 22, was coated with a gold layer having a weight of 0.08 mg / cm 2 A half-cell 102 of Example 11 was obtained in the same manner as in Example 9, except that the low resistance layer 23 of Example 11 was coated with an indium (In) layer of 109 nm and the amount of graphite powder applied was changed as shown in Table 4. Therefore, the low resistance layer 23 of Example 11 was formed of an indium layer with a thickness of 109 nm.

[0063] <Example 12> In Example 11, the surface of the sintered body 25 of the solid electrolyte facing the test electrode 22 made of graphite was coated with a weight of 0.01 mg / cm 2 A half-cell 102 of Example 12 was obtained in the same manner as in Example 11, except that the half-cell 102 was coated with an indium (In) layer of 14 nm and the amount of graphite powder applied was changed as shown in Table 4. Therefore, the low resistance layer 23 of Example 12 was formed of an indium layer with a thickness of 14 nm.

[0064] <Example 13> In Example 9, only one surface of the sintered body 25 of the solid electrolyte on which the lithium foil serving as the counter electrode 26 was placed was coated with a gold layer, and the other surface of the sintered body 25 of the solid electrolyte on which the test electrode 22 made of graphite was placed, i.e., the surface facing the test electrode 22, was coated with a gold layer having a weight of 0.11 mg / cm 2A half-cell 102 of Example 13 was obtained in the same manner as in Example 9, except that the low resistance layer 23 of Example 13 was coated with a silver (Ag) layer of 104 nm and the amount of graphite powder applied was changed as shown in Table 4. Therefore, the low resistance layer 23 of Example 13 was formed of a silver layer with a thickness of 104 nm.

[0065] <Example 14> In Example 13, the surface of the sintered body 25 of the solid electrolyte facing the test electrode 22 made of graphite was coated with a weight of 0.03 mg / cm 2 A half-cell 102 of Example 14 was obtained in the same manner as in Example 13, except that the low resistance layer 23 of Example 14 was coated with a silver (Ag) layer of 29 nm and the amount of graphite powder applied was changed as shown in Table 4. Therefore, the low resistance layer 23 of Example 14 was formed of a silver layer with a thickness of 29 nm.

[0066] <Example 15> In Example 9, only one surface of the sintered body 25 of the solid electrolyte on which the lithium foil serving as the counter electrode 26 was placed was coated with a gold layer, and the other surface of the sintered body 25 of the solid electrolyte on which the test electrode 22 made of graphite was placed, i.e., the surface facing the test electrode 22, was coated with a gold layer having a weight of 0.16 mg / cm 2 A half-cell 102 of Example 15 was obtained in the same manner as in Example 9, except that the low resistance layer 23 of Example 15 was coated with a platinum (Pt) layer of 75 nm and the amount of graphite powder applied was changed as shown in Table 4. Therefore, the low resistance layer 23 of Example 15 was formed of a platinum layer with a thickness of 75 nm.

[0067] <Example 16> In Example 15, the surface of the sintered body 25 of the solid electrolyte facing the test electrode 22 made of graphite was coated with a weight of 0.04 mg / cm 2 A half-cell 102 of Example 16 was obtained in the same manner as in Example 15, except that the low resistance layer 23 of Example 16 was coated with a platinum (Pt) layer of 19 nm and the amount of graphite powder applied was changed as shown in Table 4. Therefore, the low resistance layer 23 of Example 16 was formed of a platinum layer with a thickness of 19 nm.

[0068] <Example 17> In Example 9, the weight of the gold layer of the resistance reducing layer 23 was 0.34 mg / cm 2A half-cell 102 of Example 17 was obtained in the same manner as in Example 9, except that the current collector 21 was changed to the test electrode 22 and the current collector 21 was disposed adjacent to the gold layer that was the low-resistance layer 23. Therefore, Example 17 did not have the test electrode 22, and the low-resistance layer 23 was formed of a gold layer with a thickness of 175 nm.

[0069] <Example 18> In Example 9, the graphite dispersion was replaced with a graphite-silicon dispersion and spray-applied, with a coating amount of 1.37 mg / cm 2 The half-cell 102 of Example 18 was obtained in the same manner as in Example 9, except that the test electrode 22 made of graphite and silicon was incorporated and the weight of the gold layer of the resistance-reducing layer 23 was changed as shown in Table 5.

[0070] (Graphite-silicon dispersion) The graphite-silicon dispersion was prepared by dispersing 450 mg of graphite powder (Imerys, KS6, average diameter 4.4 μm) and 45 mg of 50 nm silicon powder (Alfa Aesar) in 30 g of 99.5% ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.). The molar ratio of dispersed graphite to silicon was 95:5.

[0071] <Example 19> A negative electrode (negative electrode layer) consisting of only a test electrode 22 made of graphite and a current collector 21, which was an unpolished SUS304 disc having a diameter of 10 mm and a thickness of 0.5 mm, was obtained in the same manner as in Example 9, except that the amount of graphite powder applied was changed as shown in Table 4.

[0072] <Example 20> The coating weight of the test electrode 22 made of graphite and silicon was 1.717 mg / cm 2 A negative electrode (negative electrode layer) consisting of only a test electrode 22 made of graphite and silicon and a current collector 21, which was an unpolished SUS304 disk with a diameter of 10 mm and a thickness of 0.5 mm, was obtained in the same manner as in Example 18, except for changing the above.

[0073] [Characteristics evaluation] (First charge test) Using the half-cells 102 obtained in Examples 9, 10 to 16, 18, and 8, CC charging tests were performed at a current value of 0.05 C until the voltage reached 0.01 V on a lithium metal basis. The value of each C rate was calculated from the amount of graphite applied to the test electrode 22. For the half-cell obtained in Example 18, the amount of graphite applied was estimated (1.243 mg / cm) assuming that the graphite and silicon dispersed in the graphite-silicon dispersion liquid used for spray application were applied while maintaining a weight ratio of 10:1. 2 The calculation was based on the assumption that The initial charge curves obtained as a result of the test are shown in Figures 19, 22, 24, 26, 28, 30, 32 and 34, respectively. Using the half-cell 102 obtained in Example 7, CC charging was performed for 12 hours and 10 hours at current values ​​of 0.0005C and 0.005C, respectively. Then, CC charging was performed at a current value of 0.05C until the voltage reached 0V relative to lithium metal, and a CV charging test was then performed at 0V for 10 hours. The initial charge curve obtained as a result of the test is shown in Figure 15. The test environment was an argon atmosphere at room temperature of approximately 25°C under atmospheric pressure.

[0074] (First charge test results) Table 6 shows the test results for the initial charge capacity.

[0075] [Table 6]

[0076] The weight of graphite contained in the test electrode 22 made of graphite incorporated in the half-cells 102 obtained in Examples 9, 10, and 8 was about 1 mg / cm 2 However, in Examples 9 and 10, in which the test electrode 22 made of graphite was arranged on the surface of the solid electrolyte 25 coated with a gold layer, which is the low-resistance layer 23, the current density was about 0.2 to 0.4 mAh / cm compared to Example 8, in which the test electrode 22 made of graphite was arranged on the surface of the solid electrolyte 25 that was not coated with a gold layer (no low-resistance layer 23 was arranged). 2 A large charging capacity was also obtained. Furthermore, the weight of the graphite contained in the test electrode 22 made of graphite and silicon incorporated in the half-cell 102 obtained in Example 18 and the weight of the gold layer of the low-resistance layer 23 were approximately equal to the weight of the graphite contained in the test electrode 22 made of graphite incorporated in the half-cell obtained in Example 9 and the weight of the gold layer of the low-resistance layer 23, respectively. However, it was found that the charge capacity obtained in Example 18 was nearly twice that of Example 9. The weight of graphite contained in the test electrode 22 made of graphite incorporated in the half-cells 102 obtained in Examples 11 to 16 and Example 8 was also approximately the same. However, in Examples 11 to 16, in which the test electrode 22 made of graphite was disposed on the surface of the solid electrolyte 25 coated with an indium layer, a silver layer, or a platinum layer, the electric current was about 0.2 to 0.3 mAh / cm compared to Example 8, in which the test electrode 22 made of graphite was disposed on the surface of the solid electrolyte 25 that was not coated with these layers. 2 That is, even when an indium layer, a silver layer, or a platinum layer was provided as the low resistance layer 23, the charge capacity was about 0.2 to 0.3 mAh / cm compared to when the low resistance layer 23 was not provided. 2 A large charging capacity was also obtained. Furthermore, the weight of graphite contained in test electrode 22 made of graphite incorporated in half-cells 102 obtained in Examples 7 and 8 was also approximately the same. However, in Example 14, in which test electrode 22 made of graphite was placed on the surface of solid electrolyte 25 coated with a silicon layer, which was low-resistance layer 23, and CC charging was performed until the voltage reached 0 V relative to lithium metal, and CV charging was further performed for 10 hours, the electric current consumption was approximately 0.5 mAh / cm compared to Example 8, in which test electrode 22 made of graphite was placed on the surface of solid electrolyte 25 not coated with a silicon layer, and CC charging was performed until the voltage reached 0 V relative to lithium metal, i.e., in which low-resistance layer 23 was not placed. 2 A large charging capacity was also obtained.

[0077] (Method for measuring AC impedance after the first charging test) The half-cells 102 obtained in Examples 9, 10 to 16, 7, 18, and 8 were subjected to the above-mentioned initial charging test, and then AC impedance measurements were performed at an applied AC voltage of 10 mV based on the natural potential in the frequency range of 10 mHz to 1 MHz. The AC impedance spectra obtained as a result of the test are shown in Figures 20, 23, 25, 27, 29, 31, 33, 35, 16, 39, and 18. The test environment was an argon atmosphere at room temperature of around 25°C under atmospheric pressure.

[0078] (AC impedance measurement results after the first charging test) Table 7 shows the AC impedance measurement results after the initial charging test.

[0079] [Table 7]

[0080] From the AC impedance spectra obtained after the initial charge of the half-cells 102 obtained in Examples 9, 10, and 8, in the structure without a gold layer, the interfacial resistance of the test electrode 22 made of the solid electrolyte separator layer 25 and graphite was 3188 Ω cm 2 On the other hand, in the structure in which the low resistance layer 23 made of a gold layer is sandwiched, the interface resistance is about 30 Ω·cm 2 It was found that the interfacial resistance was reduced to as low as 1000 kJ / cm. The half-cell obtained by employing the interface structure of Example 9 exhibited significantly lower interfacial resistance and cell internal resistance. This resulted in improved charge / discharge characteristics and improved battery energy density. From the AC impedance spectra obtained after the initial charge of the half-cells 102 obtained in Examples 11 to 16 and Example 7, it was found that the interface resistance was about 20 to 70 Ω cm even in the structure in which an indium (In) layer, a silver (Ag) layer, a platinum (Pt) layer, and a silicon (Si) layer were sandwiched. 2 and the interface resistance (3188 Ω cm) of the half cell obtained in Comparative Example 1 (Example 8). 2 ), it was confirmed that the interface resistance of the structure was also reduced in the same way as in the case of the structure sandwiching the gold layer. Furthermore, the low resistance layers 23 incorporated in the half cells 102 obtained in Examples 10, 12, 14, and 16 were formed of metal layers having a thickness of 10 to 30 nm, and it was found that they exhibited low interfacial resistance almost equivalent to that of Examples 9, 11, 13, and 15, in which the low resistance layers 23 incorporated corresponding metal layers having a thickness of 100 to 200 nm. Furthermore, from the AC impedance spectrum obtained after the initial charge of the half-cell 102 obtained in Example 18, in the structure in which the low-resistance layer 23 made of a gold layer is sandwiched, the interfacial resistance between the solid electrolyte separator layer 25 and the test electrode 22 made of graphite and silicon is 20 Ω cm, which is almost the same as that of the half-cells obtained in Examples 9 and 10. 2 It was found that this would be the case.

[0081] (X-ray diffraction measurement after the first charging test) After performing an initial charge test using half-cells 102 obtained in Examples 9 and 18, half-cells 102 were disassembled in a glove box under an argon gas atmosphere, and the surface of the graphite layer that had been in contact with current collector 21 was placed facing the X-ray irradiation side, sealed in an X-ray diffraction atmosphere separator (manufactured by Rigaku Corporation) (argon gas atmosphere), and X-ray diffraction measurement was performed using an X-ray diffractometer (manufactured by Rigaku Corporation, Miniflex600) in the diffraction angle range of 20° to 30° (2θ). The X-ray diffraction patterns obtained as a result of the test are shown in Figures 5 and 28, respectively.

[0082] (X-ray diffraction measurement results after the first charging test) The X-ray diffraction pattern after the initial charge of the half-cell 102 obtained in Example 9 revealed that the gold layer reacted with lithium to form an alloy Li3Au. This indicates that the volume expansion during the alloying reaction contributes significantly to the reduction in interfacial resistance observed in the structure in which the gold layer (low-resistance layer 23) is sandwiched between the test electrode 22 and the separator layer 25. Furthermore, it was found that the reduction in interfacial resistance allows lithium to be inserted into the graphite contained in the graphite layer near the current collector up to a stage 2 charge state, even during CC charging at room temperature using a current value of 0.05 C. The X-ray diffraction pattern of the half-cell 102 obtained in Example 18 after the initial charge confirmed that the gold layer reacted with lithium to form an alloy Li3Au, as in Example 9. This indicates that the volume expansion during the alloying reaction also significantly contributes to the reduction in interfacial resistance observed when the gold layer (low-resistance layer 23) was sandwiched between the test electrode 22 and the separator layer 25. However, unlike Example 9, during CC charging at room temperature using a current of 0.05 C, lithium was inserted into the graphite contained in the graphite-silicon layer near the current collector up to the stage 1 charge state. Since no peak from crystalline silicon was observed, it was determined that the silicon contained in the test electrode 22 reacted with lithium to form an amorphous lithium alloy. This indicates that the volume expansion during the alloying reaction significantly contributes to the increase in the depth of charge of graphite observed when the test electrode 22 contains a metal that undergoes volume change upon alloying with lithium.

[0083] (Measurement of element distribution in the depth direction of the negative electrode layer) The element distribution in the depth direction was measured for the negative electrode layer consisting of the test electrode 22 and current collector 21 obtained in Examples 19 and 20 using a glow discharge optical emission spectrometer (Horiba, GD-Profiler2). The element distribution in the depth direction obtained as a result of the test is shown in Figures 41 and 42, respectively. Sputtering was performed using a pulse method, and a two-kind mixed gas of argon (Ar) and oxygen (O2) in a volume ratio of 95:5 was used as the sputtering gas. The sputtering area was 4 mm in diameter.

[0084] (Measurement results of element distribution in the depth direction of the negative electrode layer) From the element distribution in the depth direction of the negative electrode layer obtained in Example 19, it can be seen that the iron (Fe) signal, which is the signal from the SUS disk of the current collector 21, is hardly observed until just before the carbon (C) signal begins to drop, which indicates that the test electrode 22 is a graphite particle laminate of uniform thickness. Regarding the element distribution in the depth direction of the negative electrode layer obtained in Example 20, the iron (Fe) signal, which is the signal from the SUS disk of the current collector 21, is hardly observed until just before the carbon (C) signal begins to drop, which indicates that the test electrode 22 is a graphite particle laminate of uniform thickness. In addition, the silicon (Si) signal continues to be observed at a constant intensity until the carbon signal begins to drop, which indicates that silicon is uniformly distributed within the test electrode 22.

[0085] (Initial charging test of low resistance layer) Using the half-cell 102 obtained in Example 17, a current value of 23.7 μA / cm 2 was applied until the voltage reached 0.01 V on a lithium metal basis. 2 The CC charging test was carried out at 1.274 mg / cm when 1.00 mg of graphite was applied to a current collector 21 having a diameter of 10 mm. 2 This is the same as charging the test electrode 22 made of graphite at 0.05 C. In other words, it is almost the same current value as that used in Example 9. The initial charge curve obtained as a result of the test is shown in Figure 36. Here, the test environment was an argon atmosphere at room temperature of about 25°C under atmospheric pressure.

[0086] (Results of the initial charging test on the low resistance layer) The half-cell 102 obtained in Example 17 did not incorporate the test electrode 22 made of graphite, but the gold layer of the low resistance layer 23 reacted with lithium to form an alloy, resulting in a capacity of 0.154 mAh / cm 2 A charging capacity of 1000kJ / s was obtained.

[0087] (Method for measuring AC impedance after the first charge test of the low resistance layer) After the above-mentioned initial charging test was carried out using the half cell 102 obtained in Example 17, AC impedance was measured at an applied AC voltage of 10 mV with respect to the natural potential in the frequency range of 10 mHz to 1 MHz. The AC impedance spectrum obtained as a result of the test is shown in Figure 37. The test environment was an argon atmosphere at room temperature of about 25°C under atmospheric pressure.

[0088] (AC impedance measurement results after the first charge test of the low resistance layer) The interface resistance calculated from the AC impedance measurement results after the first charging test was 31 Ω cm 2 It was found that the interface resistance was approximately the same as that of the half cells obtained in Examples 9 and 10 in which a gold layer was used as the resistance-reducing layer 23 and a test electrode 22 made of graphite was incorporated.

[0089] (Initial charge capacity of graphite layer) The half-cell 102 obtained in Example 9 incorporates a test electrode 22 made of graphite that reacts with lithium and a gold layer as the resistance-reducing layer 23. Therefore, the obtained 2 The charge capacity of the half-cell obtained in Example 17 includes the capacities of both active materials. The half-cell obtained in Example 17 incorporates only the gold layer, which is the low resistance layer 23, and its weight is almost the same as that of Example 9. Therefore, the charge capacity of the half-cell obtained in Example 17 is 0.154 mAh / cm. 2 can be considered to be the charge capacity of the gold layer, which is the low resistance layer 23, among the charge capacities of the half-cell obtained in Example 9. That is, in the half-cell 102 obtained in Example 9, the charge capacity of the test electrode 22 made of graphite was 0.359 mAh / cm 2 (=0.513mAh / cm 2 - 0.154mAh / cm 2 ) and it was found that charging was possible with a weight capacity density of 291mAh / g.

[0090] (Initial charge capacity of graphite-silicon layer) The half-cell 102 obtained in Example 18 incorporates a test electrode 22 made of graphite and silicon that react with lithium, and a gold layer as the resistance-reducing layer 23. Therefore, the obtained 2 The charge capacity of the half-cell obtained in Example 17 includes the capacities of the three active materials. The half-cell obtained in Example 17 incorporates only the gold layer, which is the low resistance layer 23, and its weight is approximately the same as that of Example 9. Therefore, the charge capacity of the half-cell 102 obtained in Example 17 is 0.154 mAh / cm 2can be considered to be the charge capacity of the gold layer, which is the low resistance layer 23, among the charge capacities of the half-cell 102 obtained in Example 18. In other words, in the half-cell 102 obtained in Example 18, the charge capacity of the test electrode 22 made of graphite and silicon was 0.970 mAh / cm 2 (=1.124mAh / cm 2 -0.154mAh / cm 2 ) In addition, the charge capacity is calculated as 0.525mAh / cm, assuming that the weight ratio of graphite dispersed in the graphite-silicon dispersion liquid used for spray application was maintained at 10:1 and the silicon was charged to its theoretical capacity based on the amount of silicon applied. 2 is the charge capacity of the silicon of the test electrode 22, the charge capacity of the graphite of the test electrode 22 is 0.445 mAh / cm 2 It was found that the battery was able to be charged with a weight capacity density of 359mAh / g. It was found that the graphite contained in test electrode 22, which was a mixture of graphite and silicon at a molar ratio of 95:5 in half-cell 102 obtained in Example 18, exhibited a greater weight capacity density, closer to the theoretical capacity, than the weight capacity density exhibited by test electrode 22 made of graphite alone in half-cell 102 obtained in Example 9. This is consistent with the result that the X-ray diffraction pattern measured after the first charge showed that the graphite had intercalated lithium up to the stage 1 charge state. Measurement of the elemental distribution in the depth direction of the negative electrode layer revealed that silicon was uniformly distributed within the test electrode 22, which was made of graphite and silicon and was prepared by spray coating using a graphite-silicon dispersion. Furthermore, X-ray diffraction measurements after the first charge revealed that the silicon contained in the test electrode 22 reacted with lithium and transformed into an amorphous silicon alloy after charging. These findings suggest that the higher weight capacity density of graphite in the test electrode 22, where silicon was mixed with graphite, compared with the weight capacity density of graphite in the test electrode 22 made solely of graphite, is largely due to the volume expansion during the silicon alloying reaction and the network formation within the test electrode 22 due to the bonding of alloy particles, as seen in Patent Document 2 and Non-Patent Document 2.

[0091] (Charge-discharge cycle test) Using the half-cell 102 obtained in Example 3, a charge-discharge test was conducted at a current value of 0.05 C in a voltage range of 0.01 to 1.2 V vs. lithium metal. The initial charge-discharge curve obtained as a result of the test is shown in Figure 7, and the battery capacity versus the number of charge-discharge cycles up to 20 cycles is shown in Figure 8. The test environment was an argon atmosphere at room temperature of around 25°C under atmospheric pressure.

[0092] (Charge / discharge cycle test results) The initial charge-discharge curve of the half-cell 102 obtained in Example 3 showed no significant hysteresis and the initial Coulombic efficiency exceeded 70%. High reversibility was observed in the second and subsequent cycles, and no significant capacity loss was observed. This indicates that the half-cell 102 obtained using the interface structure of the present disclosure exhibits not only high energy density but also high stability. [Industrial Applicability]

[0093] The present invention relates to an all-solid-state lithium-ion secondary battery, which is expected to be a next-generation secondary battery for electric vehicles including hybrids, submarines, homes, and industries due to its electric capacity, charge / discharge and large-current characteristics, miniaturization, and safety. The present invention provides an all-solid-state lithium-ion secondary battery with low internal resistance and excellent charge / discharge characteristics. Therefore, it is believed that the present invention will greatly contribute to the development of the industry. [Explanation of symbols]

[0094] 11: Negative electrode current collector 12: Negative electrode active material layer (e.g., graphite) 13: Low resistance layer 14: Negative electrode (negative electrode layer) 15: Separator layer (all-solid electrolyte layer, solid electrolyte, sintered body) 16: Positive electrode active material layer 17: Positive electrode current collector 18: Positive electrode (positive electrode layer) 21: Current collector 22: Test electrode (e.g., graphite) 23: Low resistance layer 25: Separator layer (all-solid electrolyte layer, solid electrolyte, sintered body) 26: Counter electrode (lithium foil) 27: Current collector 101: All-solid-state lithium-ion secondary battery 102: All-solid-state lithium-ion half-cell

Claims

1. An all-solid-state lithium ion secondary battery having at least a negative electrode layer, a separator layer, and a positive electrode layer, the negative electrode layer includes a negative electrode active material having graphite, the separator layer contains a solid electrolyte, a low resistance layer is formed at the interface between the negative electrode layer and the separator layer, the low resistance layer is made of a lithium alloy or has a substance that forms a lithium alloy when a secondary battery operation is performed in which a current flows between the negative electrode layer and the positive electrode layer, and is a layer in which the substance is continuously arranged and fixed.

2. 2. The all-solid-state lithium ion secondary battery in accordance with claim 1, wherein the material of the low resistance layer contains one or more elements selected from the group consisting of gold, silver, platinum, aluminum, tin, indium, germanium, lead, zinc, antimony, magnesium, silicon, cadmium, gallium, tellurium, and bismuth.

3. 2. The all-solid-state lithium ion secondary battery in accordance with claim 1, wherein the low resistance layer has a thickness of 1 to 500 nm.

4. 2. The all-solid-state lithium-ion secondary battery according to claim 1, wherein the material of the low resistance layer is one or more selected from the group consisting of gold, silver, platinum, tin, indium, and silicon.

5. The all-solid-state lithium-ion secondary battery of claim 1, wherein the solid electrolyte contained in the separator layer has a highly ionic conductive garnet-type or garnet-like crystal structure.

6. The all-solid-state lithium ion secondary battery according to claim 1, wherein the solid electrolyte contained in the separator layer is one or more selected from the group consisting of a composite oxide containing Li and a ceramic having a garnet structure, a perovskite structure, and a lisicon structure.

7. The all-solid-state lithium ion secondary battery of claim 1, wherein the negative electrode active material is graphite.

8. The all-solid-state lithium-ion secondary battery of claim 1, wherein the negative electrode active material comprises graphite and a material capable of absorbing less than 10% lithium ions.

9. The positive electrode layer includes a positive electrode active material, The positive electrode active material is a spinel-type lithium manganese composite oxide represented by LiM 1 x Mn 2-x O 4 (wherein M 1 is at least one element selected from the group consisting of Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn, Sb, In, Nb, Mo, W, Y, Ru, and Rh, and 0.01≦x≦0.5), Li x Mn (1-y-x) Ni y M 2 z O (2-k) F l (wherein M 2 is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr and W, and is represented by 0.8≦x≦1.2, 0<y<0.5, 0≦z≦0.5, k+l<1, −0.1≦k≦0.2, 0≦l≦0.1); lithium cobalt composite oxides represented by LiCo 1-x M 3 x O 2 (where M 3 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, and is represented by 0≦x≦0.5); 2. The all-solid-state lithium-ion secondary battery according to claim 1, comprising one or more elements selected from the group consisting of a lithium nickel composite oxide represented by the formula LiM51-xN1xPO4 (wherein M5 is at least one element selected from the group consisting of Fe, Mn, and Co, and N1 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5); an olivine-type composite oxide represented by the formula LiM51-xN1xPO4 (wherein M5 is at least one element selected from the group consisting of Fe, Mn, and Co, and N1 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5); and a lithium titanium composite oxide represented by the formula Li4Ti5O12.

10. A method for manufacturing an all-solid-state lithium ion secondary battery according to any one of claims 1 to 9, wherein the low resistance layer is formed by one or more methods selected from the group consisting of a sputtering method, a vapor deposition method, a coating method, and a foil pasting method.

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