Battery

Abstract

To provide a battery capable of improving an energy density and a capacity retention.SOLUTION: A battery includes: a positive electrode collector; a positive electrode layer; an electrolyte layer; a negative electrode layer; and a negative electrode collector in this order, in which the negative electrode layer includes: a first layer disposed on the electrolyte layer side in a thickness direction and a second layer disposed on the negative electrode current collector side in the thickness direction from the first layer. Each of the first layer and the second layer includes a Si-based active material and a solid electrolyte as a negative electrode active material, a value obtained by subtracting an ionic conductivity of the second layer from the ionic conductivity of the first layer is 0.08 mS / cm or more, and a ratio of the solid electrolyte in the first layer is 47.5% by volume or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a battery.

Background Art

[0002] Various technologies have been proposed regarding batteries such as those disclosed in Patent Documents 1 to 4.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional battery using an electrode containing a solid electrolyte, there is room for improvement regarding the capacity retention rate (cycle characteristics) in the charge-discharge cycle. When increasing the content of the solid electrolyte in the electrode to improve the capacity retention rate, there is a problem that the energy density of the battery decreases.

[0005] The present disclosure has been made in view of the above circumstances, and the main object is to provide a battery capable of improving the energy density and the capacity retention rate.

Means for Solving the Problems

[0006] That is, the present disclosure includes the following aspects. <1> A battery comprising 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 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 an Si-based active material and a solid electrolyte as the negative electrode active material. 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. A battery, wherein the solid electrolyte ratio in the first layer is 47.5% by volume or less.

[0007] <2> The battery according to <1>, wherein the solid electrolyte ratio in the first layer is 35.3% by volume or more.

[0008] <3> The battery according to <1> or <2>, wherein the Si-based active material is porous.

[0009] <4> The battery according to any one of <1> to <3>, wherein the volume ratio of the solid electrolyte to the negative electrode active material (SE / AM) in the first layer is larger than the volume ratio of the solid electrolyte to the negative electrode active material (SE / AM) in the second layer.

[0010] <5> The thickness of the first layer is 7 to 25 μm. The battery according to any one of <1> to <4>, wherein the thickness of the negative electrode layer is 40 μm or more.

Advantages of the Invention

[0011] According to the present disclosure, it is possible to provide a battery capable of improving the energy density and the capacity retention rate.

Brief Description of the Drawings

[0012]

Figure 1

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments according to the present disclosure will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present disclosure (for example, batteries that do not characterize the present disclosure) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field. In the present disclosure, unless otherwise specified, the average particle size of the particles is the value of the median diameter (D50), which is the particle diameter at the integrated value of 50% in the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement.

[0014] In the present disclosure, a battery 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, 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 an Si-based active material and a solid electrolyte as negative electrode active materials, 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% by volume or less, and a battery is provided.

[0015] In the present disclosure, by laminating the negative electrode layer and increasing the ionic conductivity of the negative electrode layer on the electrolyte layer side rather than the negative electrode current collector side, while suppressing a decrease in the amount of negative electrode active material in the negative electrode layer, the entire negative electrode layer is uniformly charged, swelling near the interface between the negative electrode layer and the electrolyte layer is suppressed, and cycle characteristics can be improved.

[0016] 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.

[0017] [Positive Electrode] The positive electrode includes a positive electrode layer and a positive electrode current collector.

[0018] [Positive Electrode Layer] The positive electrode layer contains a positive electrode active material, and may contain a solid electrolyte, a conductive material, a binder, etc. as required.

[0019] 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, lithium metal phosphate, LiCoN, Li2SiO3, Li4SiO4, etc. can be mentioned. Examples of the hetero-element substituted Li-Mn spinel include 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. Lithium titanate is, for example, Li4Ti5O 12 etc. Lithium metal phosphates are, for example, LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4, etc. The shape of the positive electrode active material is not particularly limited, but it may be particulate (positive electrode active material particles). The average particle size of the positive electrode active material particles is not particularly limited and may be 1 nm to 100 μm. A coating layer containing a Li ion conductive oxide may be formed on the surface of the positive electrode active material. This is because it can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of the Li ion conductive oxide include LiNbO3, Li4Ti5O 12、and Li3PO4, etc. may be mentioned. The thickness of the coating layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, and may be 20 nm or less. The coverage rate of the coating layer on the surface of the positive electrode active material is, for example, 70% or more, and may be 90% or more.

[0020] As the conductive material, known ones can be used, and examples include carbon materials and metal particles. Examples of the carbon material include acetylene black (AB), furnace black, VGCF, carbon nanotubes, multi-walled carbon nanotubes (MWCNT), and carbon nanofibers. Among them, from the viewpoint of electron conductivity, it may be at least one selected from the group consisting of VGCF, carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers. Examples of the metal particles include particles such as Ni, Cu, Fe, and SUS. The content of the conductive material in the positive electrode layer is not particularly limited.

[0021] As the solid electrolyte, solid electrolytes that can be contained in the electrolyte layer can be exemplified. The content of the solid electrolyte in the positive electrode layer is not particularly limited, but when the total mass of the positive electrode layer is 100% by mass, it may be, for example, in the range of 1% by mass to 80% by mass.

[0022] Examples of the binder include rubber-based binders and fluoride-based binders. Examples of the rubber-based binder 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. Examples of the fluoride-based binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, and fluororubber. The content of the binder in the positive electrode layer is not particularly limited.

[0023] The thickness of the positive electrode layer is not particularly limited.

[0024] The positive electrode layer can be formed by a conventionally known method. For example, a positive electrode active material and, if necessary, other components are put into a solvent and stirred to prepare a positive electrode slurry. The positive electrode layer is obtained by applying the positive electrode slurry onto one surface of a support such as a positive electrode current collector and drying it. Examples of the solvent include butyl acetate, butyl butyrate, heptane, and N-methyl-2-pyrrolidone. The method of applying the positive electrode slurry onto one surface of a support such as a positive electrode current collector is not particularly limited, and examples include the doctor blade method, the metal mask printing method, the electrostatic coating method, the dip coating method, the spray coating method, the roll coating method, the gravure coating method, and the screen printing method. As the support, a self-supporting one can be appropriately selected and used, and it is not particularly limited. For example, metal foils such as Cu and Al can be used.

[0025] [Positive Electrode Current Collector] 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 the group consisting of 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. The form of the positive electrode current collector is not particularly limited and can be in various forms such as foil and mesh.

[0026] [Negative Electrode] The negative electrode includes a negative electrode layer and a negative electrode current collector.

[0027] [Negative Electrode Layer] 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 an Si-based active material and a solid electrolyte as the negative electrode active material, and may contain at least one of a conductive material and a binder as necessary. 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. 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. The volume ratio (SE / AM) of the solid electrolyte (SE) to the negative electrode active material (AM) in the first layer may be larger than the volume ratio of the solid electrolyte to the negative electrode active material in the second layer. The volume ratio (SE / AM) of the solid electrolyte to the negative electrode active material in the first layer may be 1 or more and 1.855 or less. The thickness of the first layer may be 7 to 25 μm. The thickness of the second layer may be 15 μm or more. The thickness of the negative electrode layer may be 40 μm or more and 1000 μm or less. Examples of the negative electrode active material include Si-based active materials. Examples of the Si-based active material include, for example, elemental Si, Si alloys, and silicon oxide. The Si-based active material may be porous Si. The Si-based active material may be diamond-type crystalline Si, clathrate Si, amorphous Si, etc., or porous clathrate Si. The clathrate Si may be clathrate type I or clathrate type II. The negative electrode active material may be negative electrode active material particles. The average particle diameter of the negative electrode active material particles is not particularly limited and may be 1 nm to 100 μm. The conductive material, solid electrolyte, and binder used for the negative electrode layer may be the same as those exemplified as the conductive material, solid electrolyte, and binder that can be contained in the positive electrode layer.

[0028] [Negative electrode current collector] The material of the negative electrode current collector may be a material that does not alloy with Li, and examples thereof include SUS, copper, nickel, etc. As the form of the negative electrode current collector, for example, foil shape, plate shape, etc. can be mentioned. The planar shape of the negative electrode current collector is not particularly limited, and examples thereof include circular shape, elliptical shape, rectangular shape, and any polygonal shape, etc. Also, the thickness of the negative electrode current collector varies depending on the shape, but for example, it may be within the range of 1 μm to 50 μm, or may be within the range of 5 μm to 20 μm.

[0029] [Electrolyte layer] The electrolyte layer may be a liquid-based electrolyte layer containing an electrolytic solution as the electrolyte, or may be a solid electrolyte layer containing a solid electrolyte as the electrolyte. The electrolyte layer may hold the electrolytic solution and may have a separator or the like for preventing contact between the positive electrode layer and the negative electrode layer. The thickness of the electrolyte layer is not particularly limited, and 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. Examples of the separator include those made of resins such as polyethylene (PE), polypropylene (PP), polyester, and polyamide. The separator may have a single-layer structure or a multi-layer structure. Examples of the multi-layer structure separator include a 2-layer structure separator of PE / PP, or a 3-layer structure separator of PP / PE / PP or PE / PP / PE. The separator may be 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.

[0030] 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 may be used as the solid electrolyte. Only one type of solid electrolyte may be used alone, or two or more types may be used in combination. Further, when two or more types of solid electrolytes are used, two or more types of solid electrolytes may be mixed, or layers of two or more types of solid electrolytes may be formed respectively to form a multilayer structure. The proportion of the solid electrolyte in the solid electrolyte layer is not particularly limited, but may be, for example, 50% by mass or more and 99% by mass or less.

[0031] 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 further contain at least one of O element and halogen element. Examples of the halogen element (X) include F element, Cl element, Br element, and I element. The sulfide solid electrolyte may be glass (amorphous), may be glass ceramics, or may be crystalline. When the sulfide solid electrolyte is crystalline, the sulfide solid electrolyte has a crystal phase. Examples of the crystal phase include Thio-LISICON type crystal phase, LGPS type crystal phase, and argyrodite type crystal phase. Examples of the sulfide solid electrolyte include Li2S-P2S5, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, and Li2S-P2S5-GeS2. Note that the description of "Li2S-P2S5" 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. Also, the molar ratio and composition of each element in the sulfide solid electrolyte can be measured, for example, by ICP emission spectrometry.

[0032] 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. Examples of the oxide solid electrolyte include 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 PO4-x N x It may be (1 ≦ x ≦ 3) or the like. The hydride solid electrolyte has, for example, Li and a complex anion containing hydrogen. Examples of the complex anion include (BH4) - , (NH2) - , (AlH4) - , and (AlH6) 3- and the like. Examples of the halogenated solid electrolyte include LiF, LiCl, LiBr, LiI, and LiI - Al2O3 and the like. Examples of the nitrided solid electrolyte include Li3N and the like.

[0033] Examples of the binder can be those that can be contained in the above-described positive electrode layer. When the solid electrolyte layer contains a binder, the content of the binder may be 0 parts by mass to 3 parts by mass with respect to the total amount of the solid electrolyte layer.

[0034] The solid electrolyte may be solid electrolyte particles. The average particle diameter (D50) of the solid electrolyte particles is not particularly limited, but from the viewpoint of reducing battery resistance, it may be 0.1 μm or more, it may be 0.5 μm or more, it may be 100 μm or less, or it may be 10 μm or less.

[0035] The solid electrolyte layer can be formed, for example, by the following method. A solid electrolyte slurry containing a solid electrolyte, a binder, and a solvent may be prepared, and the solid electrolyte layer may be formed by applying the solid electrolyte slurry onto a release film. Examples of the solvent can be those that can be used for preparing the above-described positive electrode slurry.

[0036] The battery may include an exterior body that houses a positive electrode layer, a negative electrode layer, a solid electrolyte layer, etc., as necessary. The material of the outer package is not particularly limited as long as it is stable in the electrolyte, and examples thereof include resins such as aluminum, polypropylene, polyethylene, and acrylic resin.

[0037] Examples of the shape of the battery include coin type, laminate type, cylindrical type, and square type.

[0038] The battery of the present disclosure may be a liquid battery or a solid battery. In the present disclosure, the solid battery means a battery including a solid electrolyte. The solid battery may be a semi-solid battery including a solid electrolyte and a liquid-based material, or may be an all-solid battery including no liquid-based material. When 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 one power generation unit or may have two or more power generation units. When the battery has two or more power generation units, those power generation units may be connected in series or in parallel. The battery may be a primary battery or a secondary battery. Examples of the use of the battery include power sources for vehicles such as hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), electric vehicles (BEV), gasoline vehicles, and diesel vehicles. Among them, it may be used as a driving power source for a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), or an electric vehicle (BEV). Further, the battery may be used as a power source for a moving body other than a vehicle (for example, a railway, a ship, and an aircraft), or may be used as a power source for an electric product such as an information processing device.

[0039] FIG. 1 is a cross-sectional schematic view showing an example of the battery of the present disclosure. The battery 100 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 in this order.

Examples

[0040] (Examples 1 to 10, Comparative Examples 6 to 8) [Preparation of Anode Slurry] A porous Si-based active material as the anode active material, a sulfide solid electrolyte as the solid electrolyte, a conductive material (0.4 mg), SBR (20 mg) as the binder, and diisobutyl ketone (1765 mg) as the solvent were mixed and dispersed for 10 minutes with ultrasonic waves having an amplitude of 40 μm and a frequency of 20 kHz to prepare an anode slurry. [Preparation of the First Layer] The slurry prepared above was coated on an Al foil and dried on a hot plate to prepare the first layer. The volume percentages of the solid electrolyte and 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. [Preparation of the Second Layer] The slurry prepared above was coated on a roughened Ni foil and dried on a hot plate to prepare the second layer. The volume percentages of the solid electrolyte and 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. [Preparation of Anode] The first layer on the Al foil and the second layer on the Ni foil were faced each other and roll-pressed at a linear pressure of 0.25 t / cm to transfer the first layer to the second layer on the Ni foil side and peel off the Al foil, thereby preparing an anode having a two-layer structure negative electrode layer and a Ni foil as the anode current collector. [Preparation of Solid Electrolyte Layer] To heptane (0.8 g) as the solvent, a sulfide solid electrolyte (0.4 g) as the solid electrolyte and an ABR 5 wt% heptane solution (0.05 g) as the binder were added and dispersed with ultrasonic waves for 10 minutes. The obtained solid electrolyte slurry was coated on a stainless steel foil using a blade with a gap of 50 μm to prepare a solid electrolyte layer. [Preparation of Cathode] To diisobutyl ketone (1 g) as the solvent, NCA (2 g) as the cathode active material, multi-walled carbon nanotubes (MWCNT) (0.03 g) as the conductive material, a sulfide solid electrolyte (0.3 g) as the solid electrolyte, and a PVDF-HFP 5 wt% diisobutyl ketone solution (0.3 g) as the binder were added and dispersed with ultrasonic waves for 10 minutes. The obtained cathode slurry was coated on an Al foil as the cathode current collector using a blade with a gap of 100 μm to prepare a cathode having a cathode layer and a cathode current collector. [Preparation of Battery] A solid electrolyte layer was laminated on the negative electrode layer, and roll-pressed at a linear pressure of 3 t / cm at room temperature to obtain a negative electrode side laminate. A solid electrolyte layer was laminated on the positive electrode layer, and roll-pressed at a linear pressure of 5 t / cm at 170 °C to obtain a positive electrode side laminate. Each of the negative electrode side laminate and the positive electrode side laminate was punched out with a 1 cm 2 and the solid electrolyte layers were overlapped and joined to fabricate a battery.

[0041] (Comparative Examples 1 to 5) Without fabricating the second layer, in [Fabrication of the first layer], a battery was fabricated in the same manner as in Example 1 except that a Ni foil was used instead of the Al foil, and in [Fabrication of the negative electrode], a negative electrode having a one-layer negative electrode layer and a Ni foil as a negative electrode current collector was fabricated. The volume % of the solid electrolyte and the volume % of the Si-based active material, SE / AM, and thickness in each first layer of Comparative Examples 1 to 5 are shown in Table 1.

[0042]

Table 1

[0043] [Ionic conductivity measurement] The ionic conductivity under the specified conditions of each first layer fabricated in Examples 1 to 10 and Comparative Examples 1 to 8 was calculated. The results are shown in Table 2. The ionic conductivity under the specified conditions of each second layer fabricated in Examples 1 to 10 and Comparative Examples 6 to 8 was calculated. The results are shown in Table 2.

[0044] [Battery resistance measurement] The resistance under the specified conditions of each battery fabricated in Examples 1 to 10 and Comparative Examples 1 to 8 was calculated according to Ohm's law. The results are shown in Table 2.

[0045] [Number of charge / discharge cycles until the capacity is less than 80%] For each battery 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 until the capacity of the battery became less than 80% from the first charge / discharge was measured. The results are shown in Table 2.

[0046] [Improvement in cycles per increase in thickness compared to Comparative Example 1] The increase in the thickness of the negative electrode layers of Examples 1 to 10 and Comparative Examples 2 to 8 with respect to the thickness of the negative electrode layer of Comparative Example 1 was calculated. The increase in the number of charge-discharge cycles (improvement in cycles) of the charge-discharge cycles less than 80% of the capacity of Examples 1 to 10 and Comparative Examples 2 to 8 with respect to the number of charge-discharge cycles less than 80% of the capacity of Comparative Example 1 was calculated. Then, the improvement in cycles per increase in thickness (cycles / μm) with respect to Comparative Example 1 was calculated. The results are shown in Table 2.

[0047]

Table 2

[0048] As shown in Table 2, in Comparative Example 1 and Comparative Example 6, although the configurations of the negative electrode layers are different, one layer and two layers, respectively, and the total thicknesses of the negative electrode layers are the same, no improvement in the cycle characteristics of the battery was observed, and it can be seen that the resistance increases in the two-layer configuration. It can be seen that in Example 1 compared to Comparative Example 2, in Example 2 compared to Comparative Example 3, in Example 3 compared to Comparative Example 4, and in Example 4 compared to Comparative Example 5, the thickness of the negative electrode layer can be reduced and the cycle characteristics of the battery can be improved, respectively. When comparing Examples 1 to 4 with Comparative Examples 6 to 8, it can be seen that 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 cycle characteristics of the battery can be improved by the solid electrolyte ratio in the first layer being 47.5% by volume or less. When comparing Example 2, Examples 5 to 7, and comparing Example 3, Examples 8 to 10, it can be seen that the cycle characteristics of the battery can be improved when the thickness of the first layer is smaller.

Description of reference numerals

[0049] 10. Positive current collector 20. Positive electrode layer 30. Electrolyte layer 40. First layer of negative electrode layer 50. Second layer of negative electrode layer 60. Negative current collector 100. Battery

Claims

1. A battery comprising 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, 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 and a solid electrolyte as negative electrode active materials, 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% by volume or less.

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

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

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

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

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