Battery

Abstract

The invention discloses a battery. A battery provided with a positive electrode current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer, and a negative electrode current collector in this order, the negative electrode layer having a first layer disposed on the electrolyte layer side in the thickness direction and a second layer disposed closer to the negative electrode current collector side than the first layer in the thickness direction, the first layer and the second layer each contain a Si-based active material as a negative electrode active material and a solid electrolyte, the value obtained by subtracting the ion conductivity of the second layer from the ion conductivity of the first layer is 0.08 mS / cm or more, and the ratio of the solid electrolyte in the first layer is 47.5 vol% or less.

Description

Technical Field

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

[0002] Regarding the batteries disclosed in, for example, JP-A-2023-044620, JP-A-2015-225855, JP-A-2012-104270, and JP-A-2011-124028, various techniques have been proposed. Summary of the Invention

[0003] In a conventional battery using an electrode containing a solid electrolyte, there is room for improvement in the capacity retention rate (cycle characteristics) during charge and discharge cycles. If the content of the solid electrolyte in the electrode is increased to improve the capacity retention rate, there is a problem that the energy density of the battery decreases.

[0004] The present disclosure has been made in view of the above actual situation, and its main object is to provide a battery capable of improving the energy density and the capacity retention rate.

[0005] That is, the present disclosure includes the following aspects.

[0006] <1> A battery including a positive electrode current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer, and a negative electrode current collector in this order,

[0007] The negative electrode layer has a first layer disposed on the electrolyte layer side in the thickness direction and a second layer disposed on the negative electrode current collector side in the thickness direction with respect to the first layer,

[0008] The first layer and the second layer each contain an Si-based active material as a negative electrode active material and a solid electrolyte,

[0009] A value obtained by subtracting the ionic conductivity of the second layer from the ionic conductivity of the first layer is 0.08 mS / cm or more,

[0010] The solid electrolyte ratio in the first layer is 47.5 vol% or less.

[0011] <2> The battery according to <1>,

[0012] The solid electrolyte ratio in the first layer is 35.3 vol% or more.

[0013] <3> The battery according to <1> or <2>,

[0014] The Si-based active material is porous.

[0015] <4> The battery according to any one of <1> to <3>,

[0016] The volume ratio of the solid electrolyte in the first layer to the negative electrode active material (SE / AM) is greater than the volume ratio of the solid electrolyte in the second layer to the negative electrode active material (SE / AM).

[0017] <5>The battery according to any one of <1> to <4>,

[0018] The thickness of the first layer is 7 to 25 μm,

[0019] The thickness of the negative electrode layer is 40 μm or more.

[0020] According to the present disclosure, a battery capable of improving the energy density and the capacity retention rate can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Hereinafter, the features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described with reference to the drawings, and the same reference numerals denote the same elements.

[0022] Figure 1 It is a cross-sectional schematic view showing an example of the battery of the present disclosure. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present disclosure will be described. Furthermore, matters necessary for implementing the present disclosure other than those specifically mentioned in this specification (for example, batteries not representing the present disclosure) can be grasped as design matters of those skilled in the art based on the prior art in the art. The present disclosure can be implemented based on the content disclosed in this specification and the common technical knowledge in the art.

[0024] In the present disclosure, unless otherwise specified, the average particle diameter of the particles is the particle diameter (median diameter (D50)) at which the cumulative value in the volume-based particle size distribution measured by laser diffraction-scattering particle size distribution measurement is 50%.

[0025] In the present disclosure, a battery is provided that sequentially includes a positive electrode current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer, and a negative electrode current collector.

[0026] The negative electrode layer has a first layer disposed on the electrolyte layer side in the thickness direction and a second layer disposed on the negative electrode current collector side closer to the negative electrode current collector than the first layer in the thickness direction.

[0027] The first layer and the second layer each contain an Si-based active material and a solid electrolyte as negative electrode active materials.

[0028] The value obtained by subtracting the ionic conductivity of the second layer from the ionic conductivity of the first layer is 0.08 mS / cm or more.

[0029] The ratio of the solid electrolyte in the first layer is 47.5% by volume or less.

[0030] In the present disclosure, by making the negative electrode layer multi-layered and having a higher ionic conductivity of the negative electrode layer on the electrolyte layer side than on the negative electrode current collector side, it is possible to suppress a decrease in the amount of the negative electrode active material in the negative electrode layer, and the entire negative electrode layer is uniformly charged, so that swelling near the electrolyte layer interface of the negative electrode layer can be suppressed, and the cycle characteristics can be improved.

[0031] The battery of the present disclosure includes a positive electrode current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer, and a negative electrode current collector in this order.

[0032] [Positive Electrode]

[0033] The positive electrode includes a positive electrode layer and a positive electrode current collector.

[0034] [Positive Electrode Layer]

[0035] The positive electrode layer contains a positive electrode active material, and may also contain a solid electrolyte, a conductive material, a binder, etc. as needed.

[0036] Examples of the positive electrode active material include lithium nickel cobalt aluminum oxide (NCA), LiCoO2, LiNi x Co 1-x O2 (0 < x < 1), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, LiMn2O4, LiNiO2, LiVO2, hetero-element substituted Li-Mn spinel, lithium titanate, metal lithium phosphate, LiCoN, Li2SiO3, and Li4SiO4, etc. Examples of the hetero-element substituted Li-Mn spinel are LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4, and LiMn 1.5 Zn 0.5 O4, etc. Examples of lithium titanate are Li4Ti5O 12 etc. Examples of metal lithium phosphate are LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4, etc.

[0037] The shape of the positive electrode active material is not particularly limited, and it may be in the form of particles (positive electrode active material particles). The average particle diameter of the positive electrode active material particles is not particularly limited, and may be 1 nm to 100 μm.

[0038] A coating containing a Li ion-conductive oxide can also be formed on the surface of the positive electrode active material. This is because the reaction between the positive electrode active material and the solid electrolyte can be suppressed.

[0039] Examples of the Li ion-conductive oxide include LiNbO3, Li4Ti5O 12 and Li3PO4, etc. The thickness of the coating is, for example, 0.1 nm or more and can be 1 nm or more. On the other hand, the thickness of the coating is, for example, 100 nm or less and can be 20 nm or less. The coverage rate of the coating on the surface of the positive electrode active material is, for example, 70% or more and can be 90% or more.

[0040] As the conductive material, known materials can be used. Examples include carbon materials and metal particles, etc. Examples of the carbon materials include acetylene black (AB), furnace black, VGCF, carbon nanotubes, multi-walled carbon nanotubes (MWCNT), and carbon nanofibers, etc. Among them, from the viewpoint of electron conductivity, it can be at least one selected from VGCF, carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers. Examples of the metal particles include particles of Ni, Cu, Fe, and SUS (stainless steel), etc.

[0041] The content of the conductive material in the positive electrode layer is not particularly limited.

[0042] As the solid electrolyte, a solid electrolyte that can be contained in the electrolyte layer can be exemplified.

[0043] The content of the solid electrolyte in the positive electrode layer is not particularly limited. When the total mass of the positive electrode layer is set to 100% by mass, for example, it can be in the range of 1% to 80% by mass.

[0044] Examples of the binder include rubber-based binders, fluoride-based binders, etc. Examples of the rubber-based binders include butadiene rubber, acrylonitrile-butadiene rubber (ABR), hydrogenated butadiene rubber, styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber, nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, and ethylene-propylene rubber, etc. Examples of the fluoride-based binders include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, and fluororubber, etc.

[0045] The content of the binder in the positive electrode layer is not particularly limited.

[0046] Regarding the thickness of the positive electrode layer, there is no particular limitation.

[0047] The positive electrode layer can be formed by a conventionally known method.

[0048] For example, a positive electrode paste is prepared by putting a positive electrode active material and other components added as needed into a solvent and stirring them, and the positive electrode paste is coated on one surface of a support such as a positive electrode current collector and dried, whereby a positive electrode layer is obtained.

[0049] Examples of the solvent include butyl acetate, butyl butyrate, heptane, and N-methyl-2-pyrrolidone.

[0050] The method of coating the positive electrode paste on one surface of a support such as a positive electrode current collector is not particularly limited, and examples thereof include a doctor blade method, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, an intaglio coating method, and a screen printing method.

[0051] As the support, a support having self-supporting properties can be appropriately selected and used, and there is no particular limitation. For example, metal foils such as Cu and Al can be used.

[0052] [Positive Electrode Current Collector]

[0053] As the positive electrode current collector, a known metal that can be used as a current collector of a battery can be used. Examples of such a metal include metal materials containing one or more elements selected from Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Examples of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon.

[0054] The form of the positive electrode current collector is not particularly limited, and various forms such as a foil shape and a mesh shape can be adopted.

[0055] [Negative Electrode]

[0056] The negative electrode includes a negative electrode layer and a negative electrode current collector.

[0057] [Negative Electrode Layer]

[0058] The negative electrode layer has a first layer disposed on the electrolyte layer side in the thickness direction and a second layer disposed on the negative electrode current collector side in the thickness direction and closer to the negative electrode current collector than the first layer.

[0059] The first layer and the second layer each contain a Si-based active material as a negative electrode active material and a solid electrolyte, and may contain at least one of a conductive material and a binder as needed.

[0060] The value obtained by subtracting the ionic conductivity of the second layer from the ionic conductivity of the first layer may be 0.08 mS / cm or more, and the upper limit is not particularly limited.

[0061] The ratio of the solid electrolyte in the first layer may be 47.5% by volume or less, and the lower limit may be 35.3% by volume or more.

[0062] The volume ratio of the solid electrolyte (SE) to the negative electrode active material (AM) in the first layer (SE / AM) can be greater than the volume ratio of the solid electrolyte to the negative electrode active material in the second layer (SE / AM).

[0063] The volume ratio of the solid electrolyte to the negative electrode active material in the first layer (SE / AM) can be 1 or more and 1.855 or less.

[0064] The thickness of the first layer can be 7 to 25 μm.

[0065] The thickness of the second layer can be 15 μm or more.

[0066] The thickness of the negative electrode layer can be 40 μm or more and 1000 μm or less.

[0067] Examples of the negative electrode active material include Si-based active materials. Examples of the Si-based active material include elemental Si, Si alloys, and silicon oxides. The Si-based active material can be porous Si. The Si-based active material can be diamond-type crystalline Si, clathrate Si, amorphous Si, etc., and can be porous clathrate Si. Clathrate Si can be clathrate type I or clathrate type II.

[0068] The negative electrode active material can be negative electrode active material particles. The average particle diameter of the negative electrode active material particles is not particularly limited and can be 1 nm to 100 μm.

[0069] Examples of the conductive material, solid electrolyte, and binder used in the negative electrode layer include the same materials as those exemplified as the conductive material, solid electrolyte, and binder that can be included in the positive electrode layer.

[0070] [Negative electrode current collector]

[0071] The material of the negative electrode current collector can be a material that does not alloy with Li, and examples thereof include SUS, copper, and nickel. Examples of the form of the negative electrode current collector include foil and plate. The top view shape of the negative electrode current collector is not particularly limited, and examples thereof include circular, elliptical, rectangular, and arbitrary polygons. In addition, the thickness of the negative electrode current collector varies depending on the shape and can be in the range of 1 μm to 50 μm, or can be in the range of 5 μm to 20 μm.

[0072] [Electrolyte layer]

[0073] The electrolyte layer can be a liquid-based electrolyte layer containing an electrolytic solution as the electrolyte, or can be a solid electrolyte layer containing a solid electrolyte as the electrolyte.

[0074] The electrolyte layer may be an electrolyte layer such as a separator that prevents contact between the positive electrode layer and the negative electrode layer while retaining the electrolyte solution. The thickness of the electrolyte layer is not particularly limited. For example, it may be 0.1 μm or more, or 1 μm or more, and may be 2 mm or less, or 1 mm or less.

[0075] Examples of the separator include a separator made of a resin such as polyethylene (PE), polypropylene (PP), polyester, and polyamide. The separator may be a single-layer structure or a multi-layer structure. As the separator of the multi-layer structure, for example, a separator having a two-layer structure of PE / PP, or a separator having a three-layer structure of PP / PE / PP or PE / PP / PE can be cited. The separator may also be a separator made of a non-woven fabric such as a cellulose non-woven fabric, a resin non-woven fabric, or a glass fiber non-woven fabric.

[0076] Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, halide solid electrolytes, and nitride solid electrolytes, and organic polymer electrolytes such as polymer electrolytes. From the viewpoint of suppressing peeling of the positive electrode layer and the negative electrode layer from the solid electrolyte layer and further reducing the resistance of the solid battery, a relatively soft sulfide solid electrolyte can be used as the solid electrolyte. The solid electrolyte may be used alone or in combination of two or more. In addition, when two or more solid electrolytes are used, two or more solid electrolytes may be mixed, or layers of two or more solid electrolytes may be formed to form a multi-layer structure.

[0077] The proportion of the solid electrolyte in the solid electrolyte layer is not particularly limited. For example, it is 50% by mass or more and may be 99% by mass or less.

[0078] Sulfide solid electrolytes include, for example, solid electrolytes containing Li element, A element, and S element. The A element is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In. The sulfide solid electrolyte may also contain at least one of O element and halogen element. As the halogen element (X), for example, F element, Cl element, Br element, and I element can be cited. The sulfide solid electrolyte can be glass (amorphous), can be glass-ceramics, or can be crystalline. When the sulfide solid electrolyte is crystalline, the sulfide solid electrolyte has a crystalline phase. As the crystalline phase, for example, Thio-LISICON type crystalline phase, LGPS type crystalline phase, and argyrodite type crystalline phase can be cited. As the sulfide solid electrolyte, for example, Li2S-P2S5, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, and Li2S-P2S5-GeS2 can be cited. Furthermore, the description of "Li2S-P2S5" above means a material formed using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions. The molar ratio of each element in the sulfide solid electrolyte can be controlled by adjusting the content of each element in the raw material. In addition, the molar ratio and composition of each element in the sulfide solid electrolyte can be measured, for example, by ICP emission spectrometry.

[0079] Oxide solid electrolytes include, for example, solid electrolytes containing Li element, Z element (Z is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O element. As the oxide solid electrolyte, for example, it can be Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, Li 1.3 Al 0.3 Ti 0.7 (PO4)3, Li5La3Ta2O 12 、Li7La3Zr2O 12 、Li6BaLa2Ta2O 12 、Li 3.6 Si 0.6 P 0.4 O4, Li4SiO4, Li3PO4, and Li 3+x PO 4-x N x (1≤x≤3), etc.

[0080] Hydride solid electrolytes, for example, have Li and a complex anion containing hydrogen. As the complex anion, for example, (BH4) － , (NH2) － , (AlH4)－ and (AlH6) 3－ etc.

[0081] As the halogenated solid electrolyte, for example, LiF, LiCl, LiBr, LiI, and LiI-Al2O3 etc. can be cited.

[0082] As the nitrided solid electrolyte, for example, Li3N etc. can be cited.

[0083] As the binder, the binder contained in the above-mentioned positive electrode layer can be exemplified.

[0084] When the solid electrolyte layer contains a binder, the content of the binder can be 0 to 3 parts by mass relative to the total amount of the solid electrolyte layer.

[0085] The solid electrolyte can be solid electrolyte particles.

[0086] The average particle size (D50) of the solid electrolyte particles is not particularly limited, but from the viewpoint of being able to reduce the battery resistance, it can be 0.1 μm or more, it can be 0.5 μm or more, it can be 100 μm or less, and it can be 10 μm or less.

[0087] The solid electrolyte layer can be formed, for example, by the following method.

[0088] The solid electrolyte layer can be formed by preparing a solid electrolyte slurry containing a solid electrolyte, a binder, and a solvent, and coating the above-mentioned solid electrolyte slurry on a release film.

[0089] As the solvent, the solvent that can be used in the preparation of the above-mentioned positive electrode slurry can be exemplified.

[0090] The battery may include an outer package that houses the positive electrode layer, the negative electrode layer, the solid electrolyte layer, etc. as needed.

[0091] The material of the outer package is not particularly limited as long as it is a material that is stable in the electrolyte, and resins such as aluminum, polypropylene, polyethylene, and acrylic resin etc. can be cited.

[0092] As the shape of the battery, for example, coin type, laminate type, cylindrical type, and square type etc. can be cited.

[0093] The battery of the present disclosure can be a liquid battery or a solid battery.

[0094] Furthermore, in the present disclosure, the so-called solid battery means a battery containing a solid electrolyte. As the solid battery, it can be a semi-solid battery that contains a solid electrolyte and a liquid-based material, or a all-solid battery that does not contain a liquid-based material.

[0095] In the case where a set of a positive electrode, an electrolyte layer, and a negative electrode is used as a power generation unit, the battery may have only 1 power generation unit, or may have 2 or more power generation units. In the case where the battery has 2 or more power generation units, these power generation units may be connected in series or in parallel.

[0096] The battery may be a primary battery or a secondary battery. As uses of the battery, for example, power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles can be cited. Among them, it can also be used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). In addition, the battery can be used as a power source for moving bodies other than vehicles (such as trains, ships, and airplanes), and can also be used as a power source for electrical products such as information processing devices.

[0097] Figure 1 It is a cross-sectional schematic view showing an example of the battery of the present disclosure.

[0098] The battery 100 sequentially includes a positive electrode current collector 10, a positive electrode layer 20, an electrolyte layer 30, a first layer 40 of the negative electrode layer, a second layer 50 of the negative electrode layer, and a negative electrode current collector 60.

[0099] (Examples 1 to 10, Comparative Examples 6 to 8)

[0100] [Production of negative electrode paste]

[0101] A porous Si-based active material as a negative electrode active material, a sulfide solid electrolyte as a solid electrolyte, a conductive material (0.4 mg), SBR (20 mg) as a binder, and diisobutyl ketone (1765 mg) as a solvent were mixed, and ultrasonic waves with an amplitude of 40 μm and a frequency of 20 kHz were used to disperse for 10 minutes to produce a negative electrode paste.

[0102] [Production of the first layer]

[0103] The paste prepared as described above was applied to an Al foil and dried using a hot plate to produce the first layer. The volume % of the solid electrolyte, the volume % of the Si-based active material, SE / AM, and thickness in each first layer of Examples 1 to 10 and Comparative Examples 6 to 8 are shown in Table 1.

[0104] [Production of the second layer]

[0105] The paste prepared as described above was applied to a roughened Ni foil and dried using a hot plate to produce the second layer. The volume % of the solid electrolyte, the volume % of the Si-based active material, SE / AM, and thickness in each second layer of Examples 1 to 10 and Comparative Examples 6 to 8 are shown in Table 1.

[0106] [Fabrication of the negative electrode]

[0107] The first layer on the Al foil and the second layer on the Ni foil are opposed to each other, and are roll-pressed at a linear pressure of 0.25 ton / cm to transfer the first layer to the second layer on the Ni foil side, and the Al foil is peeled off, thereby fabricating a negative electrode having a two-layer structure negative electrode layer and a Ni foil as a negative electrode current collector.

[0108] [Fabrication of the solid electrolyte layer]

[0109] To 0.8 g of heptane as a solvent, 0.4 g of a sulfide solid electrolyte as a solid electrolyte and 0.05 g of a 5 wt% heptane solution of ABR as an adhesive are added, and ultrasonic dispersion is carried out for 10 minutes. The obtained solid electrolyte slurry is applied to a stainless steel foil using a doctor blade with a gap of 50 μm to fabricate a solid electrolyte layer.

[0110] [Fabrication of the positive electrode]

[0111] To 1 g of diisobutyl ketone as a solvent, 2 g of NCA as a positive electrode active material, 0.03 g of multi-walled carbon nanotubes (MWCNT) as a conductive material, 0.3 g of a sulfide solid electrolyte as a solid electrolyte, and 0.3 g of a 5 wt% diisobutyl ketone solution of PVDF-HFP as an adhesive are added, and ultrasonic dispersion is carried out for 10 minutes. The obtained positive electrode slurry is applied to an Al foil as a positive electrode current collector using a doctor blade with a gap of 100 μm to fabricate a positive electrode having a positive electrode layer and a positive electrode current collector.

[0112] [Fabrication of the battery]

[0113] The solid electrolyte layer is overlapped on the negative electrode layer, and roll-pressed at a linear pressure of 3 ton / cm at room temperature to obtain a negative electrode side laminate. The solid electrolyte layer is overlapped on the positive electrode layer, and roll-pressed at a linear pressure of 5 ton / cm at 170 °C to obtain a positive electrode side laminate.

[0114] Each of the negative electrode side laminate and the positive electrode side laminate is blanked at 1 cm 2 and the solid electrolyte layers are overlapped and joined to fabricate a battery.

[0115] (Comparative Examples 1 to 5)

[0116] The second layer was not fabricated. In the [fabrication of the first layer], Ni foil was used instead of Al foil, and in the [fabrication of the negative electrode], a negative electrode having a single-layer structure and a Ni foil as the negative electrode current collector was fabricated. Except for this, the battery was fabricated in the same manner as in Example 1. The volume % of the solid electrolyte and the volume % of the Si-based active material, SE / AM, and thickness in each of the first layers of Comparative Examples 1 to 5 are shown in Table 1.

[0117] Table 1

[0118] - Negative electrode layer Layer 1 Layer 1 Layer 1 Layer 2 Layer 2 Layer 2 Layer 1 Layer 2 Negative electrode - Constitute SE / AM SE ratio AM ratio SE / AM SE ratio AM ratio Thickness Thickness Total thickness - (vol%) (vol%) - (vol%) (vol%) (μm) (μm) (μm) Comparative Example 1 Single layer 0.820 31.4 38.3 - - - 40 0 40 Comparative Example 2 Single layer 1.000 35.3 35.3 - - - 43 0 43 Comparative Example 3 Single layer 1.224 39.3 32.1 - - - 48 0 48 Comparative Example 4 Single layer 1.498 43.3 28.9 - - - 54 0 54 Comparative Example 5 Single layer 1.855 47.5 25.6 - - - 70 0 70 Comparative Example 6 Two layers 0.820 31.4 38.3 0.820 31.4 38.3 13 27 40 Example 1 Two layers 1.000 35.3 35.3 0.820 31.4 38.3 13 28 41 Example 2 Two layers 1.224 39.3 32.1 0.820 31.4 38.3 13 29 42 Example 3 Two layers 1.498 43.3 28.9 0.820 31.4 38.3 13 30 43 Example 4 Two layers 1.855 47.5 25.6 0.820 31.4 38.3 13 32 45 Comparative Example 7 Two layers 3.005 56.2 18.7 0.820 31.4 38.3 13 34 47 Comparative Example 8 Two layers 8.987 70.1 7.8 0.820 31.4 38.3 13 37 50 Example 5 Two layers 1.224 39.3 32.1 0.820 31.4 38.3 7 34 41 Example 6 Two layers 1.224 39.3 32.1 0.820 31.4 38.3 20 24 44 Example 7 Two layers 1.224 39.3 32.1 0.820 31.4 38.3 25 20 45 Example 8 Two layers 1.498 43.3 28.9 0.820 31.4 38.3 7 34 41 Example 9 Two layers 1.498 43.3 28.9 0.820 31.4 38.3 20 25 45 Example 10 Two layers 1.498 43.3 28.9 0.820 31.4 38.3 25 22 47

[0119] [Ion conductivity measurement]

[0120] The ion conductivity of each of the first layers fabricated in Examples 1 to 10 and Comparative Examples 1 to 8 under specified conditions was calculated. The results are shown in Table 2.

[0121] The ion conductivity of each of the second layers fabricated in Examples 1 to 10 and Comparative Examples 6 to 8 under specified conditions was calculated. The results are shown in Table 2.

[0122] [Battery resistance measurement]

[0123] According to Ohm's law, the resistance of each of the batteries fabricated in Examples 1 to 10 and Comparative Examples 1 to 8 under specified conditions was calculated. The results are shown in Table 2.

[0124] [Number of charge-discharge cycles until the capacity becomes less than 80%]

[0125] For each of the batteries fabricated in Examples 1 to 10 and Comparative Examples 1 to 8, charge and discharge were repeatedly performed under specified conditions. When the initial capacity of the battery was set to 100%, the number of charge-discharge cycles from the first charge-discharge until the capacity of the battery became less than 80% was measured. The results are shown in Table 2.

[0126] [Improvement in cycle / Thickness increment relative to Comparative Example 1]

[0127] The thickness increment of the negative electrode layers of Examples 1 to 10 and Comparative Examples 2 to 8 relative to the thickness of the negative electrode layer of Comparative Example 1 was calculated.

[0128] The cycle increase amount (cycle improvement amount) of the number of charge-discharge cycles until the capacity becomes less than 80% of Examples 1 to 10 and Comparative Examples 2 to 8 relative to the number of charge-discharge cycles until the capacity becomes less than 80% of Comparative Example 1 was calculated.

[0129] Then, the improvement in cycle / thickness increment (cycle / μm) relative to Comparative Example 1 was calculated. The results are shown in Table 2.

[0130] Table 2

[0131] Layer 1 Layer 2 Layer 1 - Layer 2 Unit resistance Capacity becomes less than 80% Relative to Comparative Example 1 Ionic conductivity Ionic conductivity Ionic conductivity difference Number of charge - discharge cycles Cycle improvement amount / thickness increment (mS / cm) (mS / cm) (mS / cm) <![CDATA[(ohm·cm 2 )]]> (cycles / μm) Comparative Example 1 0.24 16.7 8 Comparative Example 2 0.32 - - 15.4 16 2.7 Comparative Example 3 0.46 - - 14.8 45 4.6 Comparative Example 4 0.67 - - 14.3 108 7.1 Comparative Example 5 0.9 - - 13.9 216 6.9 Comparative Example 6 0.24 0.24 0 23.8 8 - Example 1 0.32 0.24 0.08 20.6 14 6 Example 2 0.46 0.24 0.22 18.7 35 13.5 Example 3 0.67 0.24 0.43 19.9 79 23.7 Example 4 0.9 0.24 0.66 20.1 205 39.4 Comparative Example 7 1.25 0.24 1.01 20.5 7 -0.1 Comparative Example 8 1.4 0.24 1.16 19.5 5 .0.3 Example 5 0.32 0.24 0.08 22.3 32 24 Example 6 0.32 0.24 0.08 19 40 8 Example 7 0.32 0.24 0.08 20.4 43 7 Example 8 0.67 0.24 0.43 19.1 65 57 Example 9 0.67 0.24 0.43 20.5 195 37.4 Example 10 0.67 0.24 0.43 19.6 234 32.3

[0132] As can be seen from Table 2, in Comparative Example 1 and Comparative Example 6, the structures of the negative electrode layer are one layer and two layers respectively, which are different. However, since the total thickness of the negative electrode layer is the same, no improvement in the cycle characteristics of the battery is observed, and the resistance increases in the case of the two-layer structure.

[0133] It can be seen that when comparing Example 1 with Comparative Example 2, Example 2 with Comparative Example 3, Example 3 with Comparative Example 4, and Example 4 with Comparative Example 5, the thickness of the negative electrode layer can be reduced respectively and the cycle characteristics of the battery can be improved.

[0134] Comparing Examples 1 to 4 with Comparative Examples 6 to 8, it can be seen that when the value obtained by subtracting the ionic conductivity of the second layer from the ionic conductivity of the first layer is 0.08 mS / cm or more and the solid electrolyte ratio in the first layer is 47.5 vol% or less, the cycle characteristics of the battery can be improved.

[0135] Comparing Examples 2, 5 to 7 and comparing Examples 3, 8 to 10, it can be seen that when the thickness of the first layer is small, the cycle characteristics of the battery can be improved.

Claims

1. A battery, which sequentially includes a positive electrode current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer, and a negative electrode current collector, wherein the negative electrode layer has a first layer disposed on the electrolyte layer side in the thickness direction and a second layer disposed on the negative electrode current collector side in the thickness direction relative to the first layer, the first layer and the second layer each contain a Si-based active material as a negative electrode active material and a solid electrolyte, a value obtained by subtracting the ionic conductivity of the second layer from the ionic conductivity of the first layer is 0.08 mS / cm or more, the solid electrolyte ratio in the first layer is 47.5 vol% or less.

2. The battery according to claim 1, the solid electrolyte ratio in the first layer is 35.3 vol% or more.

3. The battery according to claim 1, the Si-based active material is porous.

4. The battery according to claim 1, a volume ratio (SE / AM) of the solid electrolyte to the negative electrode active material in the first layer is greater than a volume ratio (SE / AM) of the solid electrolyte to the negative electrode active material in the second layer.

5. The battery according to claim 1, the thickness of the first layer is 7 to 25 μm, the thickness of the negative electrode layer is 40 μm or more.

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