Battery and method for manufacturing the battery

Abstract

A cell 1 according to the present disclosure comprises a positive electrode 10, a negative electrode 20, and a solid electrolyte layer 30. The solid electrolyte layer 30 is positioned between the positive electrode 10 and the negative electrode 20. The solid electrolyte layer 30 contains a solid electrolyte having lithium ion conductance. The negative electrode 20 has a negative electrode collector 21, and a negative-electrode active material layer 22 positioned between the negative electrode collector 21 and the solid electrolyte layer 30. The negative-electrode active material layer 22 has a plurality of columnar particles and does not substantially include electrolyte. The columnar particles contain silicon as a main component.

Description

[Technical Field]

[0001] The present disclosure relates to batteries and methods for manufacturing batteries. [Background technology]

[0002] In recent years, batteries using solid electrolytes have been attracting attention.

[0003] Patent Document 1 describes a negative electrode having a negative electrode active material, a first binder that is bound to a solid electrolyte and is inactive with respect to the solid electrolyte, and a second binder that has better binding properties to a negative electrode current collector than the first binder. The second binder contains a highly elastic resin such as polyimide. Patent Document 1 also describes a solid-state battery using this negative electrode.

[0004] Patent Document 2 describes a method for producing an electrode member for an all-solid-state battery, which includes a powder of simple Si as the negative electrode active material and has a negative electrode material portion that does not include a binder or a solid electrolyte.

[0005] Patent Document 3 describes a battery in which a layer containing one or more elements selected from the group consisting of Cr, Ti, W, C, Ta, Au, Pt, Mn, and Mo is disposed between a current collector and an electrode layer.

[0006] Patent Document 4 describes a lithium battery that uses amorphous silicon as the active material and has a non-aqueous electrolyte.

[0007] Non-Patent Document 1 describes an all-solid-state lithium battery having a negative electrode active material layer containing silicon nanoparticles.

[0008] Non-Patent Document 2 describes an all-solid-state lithium battery having a porous silicon membrane. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-116154 [Patent Document 2] Japanese Patent Application Publication No. 2018-120841 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-49023 [Patent Document 4] International Publication No. 2001 / 029912 [Non-patent literature]

[0010] [Non-Patent Document 1] ACS Applied Energy Materials,(US),2019,Vol.2,p.7005-7008 [Non-patent document 2] Communications Chemistry, (Eng), 2018, Vol. 1, No. 24, pp. 1-9 Summary of the Invention [Problem to be solved by the invention]

[0011] In the prior art, a battery that has both high energy density and excellent cycle characteristics is desired. [Means for solving the problem]

[0012] The present disclosure provides: A positive electrode and a negative electrode; a solid electrolyte layer located between the positive electrode and the negative electrode; Equipped with the solid electrolyte layer contains a solid electrolyte having lithium ion conductivity, the negative electrode has a negative electrode current collector and a negative electrode active material layer located between the negative electrode current collector and the solid electrolyte layer, the negative electrode active material layer has a plurality of columnar particles and is substantially free of an electrolyte, The columnar particles contain silicon as a main component. Provide the battery. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to provide a battery that has both high energy density and excellent cycle characteristics. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of a battery according to this embodiment. [Figure 2] FIG. 2 is an image of a cross section of the negative electrode of Sample No. 4 observed with a scanning electron microscope (SEM). [Figure 3] FIG. 3 is a photograph of the surface of the negative electrode of Sample No. 6. [Figure 4] FIG. 4 is a graph showing the relationship between the thickness of the negative electrode active material layer and the initial discharge capacity in the batteries according to Samples No. 1 to No. 3 and Sample No. 5. [Figure 5] FIG. 5 is a graph showing the relationship between the thickness of the negative electrode active material layer and the initial discharge capacity per unit mass in the batteries according to the respective samples. [Figure 6] FIG. 6 is a graph showing the relationship between the thickness of the negative electrode active material layer and the initial discharge capacity per unit area in the batteries according to the respective samples. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Findings that formed the basis of this disclosure) Solid-state batteries generally use separators made of solid electrolytes. In addition, the positive or negative electrode of a solid-state battery contains a solid electrolyte, for example, to improve ionic conductivity. Sulfide solid electrolytes are well known as solid electrolytes. Sulfide solid electrolytes have been used for 10 -3It has high lithium ion conductivity of more than 1000 S / cm. When a sulfide solid electrolyte is used, electrodes and solid electrolyte layers can be easily fabricated by press molding or by rolling after coating. Therefore, batteries can be easily fabricated using a sulfide solid electrolyte. For this reason, solid-state batteries using sulfide solid electrolytes have been attracting attention in recent years.

[0016] If the positive electrode or negative electrode does not contain a solid electrolyte, the capacity of the solid-state battery cannot be fully utilized. It is believed that a large amount of solid electrolyte must be contained in the positive electrode or negative electrode to fully utilize the capacity of the solid-state battery. In this case, the content of the active material in the positive electrode or negative electrode decreases. As a result, the capacity of the solid-state battery decreases.

[0017] The sulfide solid electrolyte reacts with the negative electrode current collector, such as copper or nickel, to form sulfides. The formation of sulfides increases the resistance of the battery. As a result, the charge-discharge cycle characteristics of batteries containing a sulfide solid electrolyte in the negative electrode deteriorate.

[0018] Patent Document 3 describes that a reaction between sulfur and the current collector is suppressed by disposing a reaction suppression layer between the current collector and the electrode body. However, the battery described in Patent Document 3 increases manufacturing costs.

[0019] Patent Document 1 describes a solid-state battery that uses a silicon-containing compound as the negative electrode active material. However, silicon is generally considered to have poor ion conductivity. Therefore, the rate characteristics of the solid-state battery described in Patent Document 1 are considered to be poor.

[0020] Patent Document 2 describes a method for manufacturing a battery in which particles of silicon material contained in the negative electrode are bonded to each other by applying a confining pressure of 100 MPa or more to the assembly. However, the discharge capacity of this battery is thought to be small.

[0021] Non-Patent Document 1 describes an anode in which a thin film of silicon is formed on a stainless steel substrate. However, since the adhesion between the stainless steel substrate and the silicon is low, it is difficult to increase the thickness of the silicon thin film. As a result, it is thought that the discharge capacity of a battery using this anode is small.

[0022] Patent Document 4 describes a lithium-ion secondary battery that uses a negative electrode having a thin silicon film on a copper foil and a non-aqueous electrolyte. Batteries that use a non-aqueous electrolyte have problems such as the silicon contained in the negative electrode active material reacting with the non-aqueous electrolyte during charging and discharging, causing the negative electrode active material to become deactivated.

[0023] Additionally, in batteries using a nonaqueous electrolyte, the nonaqueous electrolyte penetrates into the negative electrode active material layer, forming ion conduction paths throughout the negative electrode active material layer. Therefore, batteries using a nonaqueous electrolyte exhibit excellent initial discharge capacity. However, in batteries using a solid electrolyte, ion conduction paths can only be formed at the interface between the negative electrode active material layer and the solid electrolyte layer. Therefore, it is believed that the thicker the negative electrode active material layer, the lower the initial discharge capacity of the battery. This is a problem unique to solid-state batteries.

[0024] As a result of extensive research, the present inventors have found that even when a compound containing silicon is used as the negative electrode active material for the solid electrolyte, a battery having both high energy density and excellent cycle characteristics can be obtained, and have completed the present disclosure.

[0025] (Summary of one aspect of the present disclosure) The battery according to the first aspect of the present disclosure comprises: A positive electrode and a negative electrode; a solid electrolyte layer located between the positive electrode and the negative electrode; Equipped with the solid electrolyte layer contains a solid electrolyte having lithium ion conductivity, the negative electrode has a negative electrode current collector and a negative electrode active material layer located between the negative electrode current collector and the solid electrolyte layer, the negative electrode active material layer has a plurality of columnar particles and is substantially free of an electrolyte, The columnar particles contain silicon as a main component.

[0026] According to the first aspect, a battery having both high energy density and excellent cycle characteristics can be obtained.

[0027] In a second aspect of the present disclosure, for example, in the battery according to the first aspect, the negative electrode active material layer may have a structure in which the plurality of columnar particles are arranged along the surface of the negative electrode current collector to cover the surface. With this configuration, a battery having a high energy density can be more reliably obtained.

[0028] In the third aspect of the present disclosure, for example, in the battery according to the first or second aspect, the thickness of the negative electrode active material layer may be 4 μm or more and 20 μm or less. With this configuration, the initial discharge capacity of the battery is less likely to decrease.

[0029] In a fourth aspect of the present disclosure, for example, in the battery according to any one of the first to third aspects, the silicon content in the negative electrode active material layer may be 95 mass % or more, which can improve the initial discharge capacity of the battery.

[0030] In a fifth aspect of the present disclosure, for example, in the battery according to any one of the first to fourth aspects, the solid electrolyte may contain a sulfide, and this configuration can provide a battery having excellent lithium ion conductivity.

[0031] In a sixth aspect of the present disclosure, for example, in the battery according to any one of the first to fifth aspects, the negative electrode current collector may contain copper or nickel as a main component.

[0032] In a seventh aspect of the present disclosure, for example, in the battery according to the sixth aspect, the negative electrode current collector may contain copper as a main component.

[0033] According to the sixth and seventh aspects, a battery having a high energy density can be obtained more reliably.

[0034] In an eighth aspect of the present disclosure, for example, in the battery according to any one of the first to seventh aspects, the negative electrode active material layer may contain copper, which can more reliably improve the electronic conductivity of the negative electrode active material layer.

[0035] In a ninth aspect of the present disclosure, for example, in the battery according to any one of the first to eighth aspects, when the battery is charged at a constant current of 0.05 C to −0.62 V and then discharged at a constant current of 0.05 C to 1.4 V using the negative electrode and a LiIn counter electrode, the discharge capacity of the battery is 2500 mAh / g or more and 3 mAh / cm 2 It may be more than that.

[0036] In a tenth aspect of the present disclosure, for example, in the battery according to the ninth aspect, the discharge capacity of the battery in the constant current discharge is 3000 mAh / g or more and 4 mAh / cm 2 It may be more than that.

[0037] In an eleventh aspect of the present disclosure, for example, in the battery according to the tenth aspect, the discharge capacity of the battery in the constant current discharge is 3000 mAh / g or more and 5 mAh / cm 2 It may be more than that.

[0038] The battery according to any one of the ninth to eleventh aspects can more reliably have a high discharge capacity.

[0039] A method for producing a battery according to a twelfth aspect of the present disclosure includes: A method for manufacturing a battery according to any one of the first to eleventh aspects, comprising: depositing the silicon on the negative electrode current collector by sputtering.

[0040] With this configuration, a thin film of silicon can be formed on the negative electrode current collector.

[0041] In a thirteenth aspect of the present disclosure, for example, the method for producing a battery according to the twelfth aspect may include, after the sputtering, heat-treating the silicon at 300° C. or less, thereby improving the electronic conductivity of the battery.

[0042] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0043] (Embodiment) FIG. 1 is a cross-sectional view showing a schematic configuration of a battery according to this embodiment. As shown in FIG. 1, the all-solid-state battery 1 according to this embodiment includes a positive electrode 10, a negative electrode 20, and a solid electrolyte layer 30. The negative electrode 20 includes a negative electrode current collector 21 and a negative electrode active material layer 22. The negative electrode active material layer 22 is located between the negative electrode current collector 21 and the solid electrolyte layer 30. The solid electrolyte layer 30 is located between the positive electrode 10 and the negative electrode 20. The solid electrolyte layer 30 includes a solid electrolyte having lithium ion conductivity. The negative electrode active material layer 22 includes a plurality of columnar particles. The negative electrode active material layer 22 is substantially free of an electrolyte. The columnar particles contain silicon as a main component. In this specification, the term "substantially free of an electrolyte" means that a trace amount of the electrolyte is allowed to be mixed in, and the amount of the electrolyte mixed in relative to the total mass of the negative electrode active material layer 22 is, for example, 5 mass% or less. In this specification, the term "electrolyte" includes solid electrolytes and non-aqueous electrolytes.

[0044] In this embodiment, for example, the surface of the negative electrode current collector 21 is provided with projections and recesses. That is, the negative electrode current collector 21 has a plurality of projections on its surface. The plurality of projections may be arranged irregularly or regularly.

[0045] The columnar particles are, for example, particles extending in the thickness direction of the negative electrode current collector 21 from irregularities on the surface of the negative electrode current collector 21. The columnar particles may be formed in the protruding regions of the negative electrode current collector 21. However, the columnar particles are not necessarily limited to particles extending in the thickness direction of the negative electrode current collector 21 from the protruding portions of the negative electrode current collector 21 or particles formed in the protruding regions of the negative electrode current collector 21. The columnar particles also include, for example, columnar particles extending in the thickness direction of the negative electrode current collector 21 from the protruding portions of the negative electrode current collector 21 or particles stacked on particles formed in the protruding regions of the negative electrode current collector 21. The columnar particles are not limited to a specific shape. The columnar particles do not necessarily have a columnar shape. In some cases, the columnar particles may be spherical, acicular, or elliptical. The size of the columnar particles is not limited to a specific size.

[0046] Columnar particles containing anode active material are formed starting from each of the multiple protrusions. The columnar particles extend in the thickness direction of the anode current collector 21. The multiple columnar particles may be formed in the same or different directions. Each columnar particle is supported by a protrusion of the anode current collector 21. Adjacent columnar particles may have gaps between them. When the anode active material layer is separated into multiple parts by either gaps or gaps, each of the separated parts is referred to as a "columnar particle." In other words, the anode active material layer 22 is composed of a group of columnar particles that completely fill the surface of the anode current collector 21. This configuration more reliably produces an all-solid-state battery 1 with high energy density. In addition, this configuration ensures that the surface of the anode current collector 21 is substantially free of electrolyte. Therefore, charge / discharge cycles are less likely to produce substances that could cause resistance to ion conduction. As a result, this configuration more reliably produces an all-solid-state battery 1 with excellent cycle characteristics.

[0047] Non-Patent Document 1 describes an anode active material layer containing silicon nanoparticles. In contrast, in the all-solid-state battery 1 according to this embodiment, the anode active material layer 22 contains columnar silicon particles, making it difficult for the solid electrolyte to penetrate into the anode active material layer 22. Therefore, the solid electrolyte is less likely to come into contact with the surface of the anode current collector 21. As a result, materials that could become resistance are less likely to be generated at the contact surface between the anode current collector 21 and the anode active material layer 22 during charge and discharge. As a result, an all-solid-state battery 1 with excellent cycle characteristics can be more reliably obtained. Additionally, the anode active material layer 22 of the all-solid-state battery 1 according to this embodiment has a smaller surface area of ​​the anode active material than the anode active material layer of the battery described in Non-Patent Document 1. That is, the anode active material layer 22 of the all-solid-state battery 1 according to this embodiment is dense. As a result, in this embodiment, Li ions are more likely to conduct inside the anode active material layer 22, making it possible to obtain an all-solid-state battery 1 that can more sufficiently improve discharge capacity and has a high energy density.

[0048] As described above, the negative electrode active material layer 22 contains silicon as a main component. Specifically, the columnar particles contain silicon as a main component. From the viewpoint of energy density, the silicon content in the negative electrode active material layer 22 may be 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more. Specifically, the silicon content in the columnar particles may be 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more. Such a configuration can improve the initial discharge capacity of the battery. The silicon content can be determined, for example, by inductively coupled plasma (ICP) atomic emission spectrometry. In this specification, the term "main component" refers to the component that is contained in the largest amount by mass.

[0049] The negative electrode active material layer 22 may further contain unavoidable impurities, or starting materials, by-products, and decomposition products used in forming the negative electrode active material layer 22. The negative electrode active material layer 22 may also contain, for example, oxygen, carbon, or a different metal.

[0050] The negative electrode active material layer 22 may contain substantially only silicon. The phrase "contains substantially only silicon" means that the inclusion of a small amount of unavoidable impurities is permitted. The negative electrode active material layer 22 may contain only silicon. The columnar particles may contain substantially only silicon. The columnar particles may contain only silicon.

[0051] In the all-solid-state battery 1 according to this embodiment, the anode active material layer 22 has a structure in which, for example, a plurality of columnar particles are arranged along the surface of the anode current collector 21 to cover the surface. In other words, the anode active material layer 22 is formed by an aggregate of a plurality of columnar particles covering the surface of the anode current collector 21. The anode active material layer 22 can be formed as a single layer of a plurality of columnar particles. This makes it difficult for the solid electrolyte layer 30 and the anode current collector 21 to come into contact with each other, so that an all-solid-state battery 1 having a high energy density can be more reliably obtained.

[0052] For example, silicon forms a continuous phase in the columnar particles of the negative electrode active material layer 22. As a result, a conduction path for Li ions can be formed in the continuous phase of silicon, and the Li ions can be easily conducted inside the negative electrode active material layer 22.

[0053] The all-solid-state battery 1 may contain a portion of the solid electrolyte in the anode active material layer 22 as the battery is charged and discharged. However, immediately after fabrication of the all-solid-state battery 1 and before the first charge and discharge, the anode active material layer 22 may not substantially contain a solid electrolyte. This configuration can increase the silicon content in the anode active material layer 22, thereby providing an all-solid-state battery 1 with a high energy density. In addition, this configuration can reduce contact between the metal of the anode current collector and the sulfide solid electrolyte, since the anode active material layer 22 does not substantially contain a solid electrolyte such as a sulfide solid electrolyte. As a result, generation of sulfides during charge and discharge of the all-solid-state battery 1 can be suppressed, thereby providing an all-solid-state battery 1 that maintains its rate characteristics and cycle characteristics over a long period of time.

[0054] The average thickness of the negative electrode active material layer 22 is, for example, 4 μm or more. The upper limit of the thickness of the negative electrode active material layer 22 may be 20 μm or 10 μm. With such a configuration, it is possible to obtain an all-solid-state battery 1 in which the initial discharge capacity is less likely to decrease. Specifically, the thickness of the negative electrode active material layer 22 can be determined by observing the cross section of the all-solid-state battery 1 with a scanning electron microscope (SEM) and averaging the measured values ​​at any 50 points.

[0055] In the negative electrode active material layer 22, the average width of the columnar particles is, for example, 3 μm or more and 30 μm or less. The width of the columnar particles refers to the length of the columnar particles in a direction intersecting the direction in which the negative electrode current collector 21 and the negative electrode active material layer 22 are stacked. The width of the columnar particles can be determined, for example, by observing the cross section of the all-solid-state battery 1 with an SEM. Specifically, 50 columnar particles are arbitrarily selected from the columnar particles observed in the SEM image of the negative electrode active material layer 22. The maximum width of one columnar particle is defined as the width of the columnar particle. The average width of the columnar particles can be determined from the measured maximum widths of any 50 columnar particles.

[0056] Examples of the negative electrode current collector 21 include copper, nickel, stainless steel, and alloy foils containing these elements as the main component. The negative electrode current collector 21 may contain copper or nickel as the main component. Alternatively, the negative electrode current collector 21 may contain copper as the main component. With such a configuration, an all-solid-state battery 1 having a high energy density can be more reliably obtained.

[0057] From the viewpoints of electronic conductivity and cost, the negative electrode current collector 21 may be copper or a copper alloy. Copper reacts with, for example, a sulfide solid electrolyte to form copper sulfide. Copper sulfide is generally a substance that can cause resistance in ion conduction. In the all-solid-state battery 1 according to this embodiment, the negative electrode active material layer 22 does not substantially contain an electrolyte such as a solid electrolyte. In addition, in the all-solid-state battery 1 according to this embodiment, the surface of the negative electrode current collector 21 does not substantially contain an electrolyte. Because the metal component contained in the negative electrode current collector 21 does not readily react with the solid electrolyte, for example, copper sulfide is not readily produced even when the all-solid-state battery 1 is charged and discharged. Therefore, the all-solid-state battery 1 according to this embodiment can use copper for the negative electrode current collector 21.

[0058] Copper foil may be used as the negative electrode current collector 21. An example of the copper foil is electrolytic copper foil. Electrolytic copper foil can be obtained, for example, as follows: First, a metal drum is immersed in an electrolyte solution in which copper ions are dissolved. Copper is deposited on the surface of the drum by passing a current through the drum while rotating it. Electrolytic copper foil is obtained by peeling off the deposited copper. One or both sides of the electrolytic copper foil may be subjected to a roughening treatment or a surface treatment.

[0059] The surface of the negative electrode current collector 21 may be roughened. Such a configuration allows silicon particles to be formed in a columnar shape on the negative electrode current collector 21, and improves the adhesion between the columnar particles and the negative electrode current collector 21. As a method for roughening the surface of the negative electrode current collector 21, a method of depositing a metal by electrolysis and roughening the surface of the metal can be given.

[0060] The arithmetic mean roughness Ra of the surface of the negative electrode current collector 21 is, for example, 0.001 μm or more. The arithmetic mean roughness Ra of the surface of the negative electrode current collector 21 may be 0.01 μm or more and 1 μm or less, or 0.1 μm or more and 0.5 μm or less. By adjusting the arithmetic mean roughness Ra of the negative electrode current collector 21, the contact area between the negative electrode current collector 21 and the negative electrode active material layer 22 can be increased. This makes it difficult for the negative electrode active material layer 22 to peel off from the negative electrode current collector 21. As a result, the all-solid-state battery 1 can more reliably have high cycle characteristics. The arithmetic mean roughness Ra is a value defined in Japanese Industrial Standards (JIS) B 0601:2013 and can be measured, for example, using a laser microscope.

[0061] The thickness of the negative electrode current collector 21 is not limited to a particular value and may be 5 μm or more and 50 μm or less, or 8 μm or more and 25 μm or less.

[0062] The method for depositing silicon on the negative electrode current collector 21 is not limited to a specific method. Examples of the method include chemical vapor deposition (CVD), sputtering, evaporation, thermal spraying, and plating. By using these methods, a thin film of silicon can be formed on the negative electrode current collector.

[0063] After forming the columnar silicon particles on the anode current collector 21 by the above method, the anode 20 is, for example, heated. Copper is known to be an element that easily diffuses in silicon. Therefore, when copper is used for the anode current collector 21, the anode active material layer 22 may contain copper as the all-solid-state battery 1 is charged and discharged. Copper is malleable. By including copper in the anode active material layer 22, voids or cracks are less likely to occur in the anode active material layer 22 even if the volume of the anode active material changes due to charging and discharging. In addition, poor contact between the anode active material layer 22 and the anode current collector 21 is less likely to occur even if the volume of the anode active material changes due to charging and discharging, thereby improving the adhesion between the anode current collector 21 and the columnar silicon particles. This allows the all-solid-state battery 1 to more reliably have high cycle characteristics.

[0064] The temperature to which the negative electrode 20 is heated is, for example, 300°C or lower. At such a temperature, the silicon and copper contained in the negative electrode active material layer 22 are unlikely to form an intermetallic compound. As a result, the all-solid-state battery 1 can more reliably improve the electronic conductivity. The lower limit of the temperature to which the negative electrode 20 is heated is not limited to a specific value. The lower limit of the temperature may be 150°C or 250°C.

[0065] The solid electrolyte layer 30 includes a solid electrolyte having lithium ion conductivity. Examples of solid electrolytes used in the solid electrolyte layer 30 include sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, complex hydride solid electrolytes, and polymer solid electrolytes. The solid electrolyte includes, for example, a sulfide. This configuration allows for the production of an all-solid-state battery 1 that can have characteristics such as high energy density, high rate characteristics, and high cycle characteristics.

[0066] Examples of sulfide solid electrolytes are Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 These solid electrolytes include LiX, Li2O, MO p , or Li q MO r may be added. X includes at least one selected from the group consisting of F, Cl, Br, and I. M is at least one selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. p, q, and r are natural numbers.

[0067] The inclusion of a sulfide solid electrolyte in the solid electrolyte layer 30 can improve the adhesion between the solid electrolyte layer 30 and the negative electrode active material layer 22. As a result, the ionic conductivity can be improved at the contact surface between the solid electrolyte layer 30 and the negative electrode active material layer 22. In addition, with this configuration, an all-solid-state battery 1 having high rate characteristics can be obtained.

[0068] Examples of oxide solid electrolytes include Na Super Ionic Conductor (NASICON)-type solid electrolytes, such as LiTi2(PO4)3 and its elemental substitutions, perovskite-type solid electrolytes including (LaLi)TiO3, and Li 14 ZnGeO 16 , Li4SiO4, LiGeO4 and their element-substituted Li Super Ionic Conductor (LISICON) type solid electrolytes, Li7La3Zr2O 12 These include garnet-type solid electrolytes, such as those containing Li3N and its elemental substitution products, Li3PO4 and its H-substituted products, LiBO2, Li3BO3, and other Li-BO compounds, with the addition of Li2SO4, Li2CO3, etc.

[0069] An example of a halide solid electrolyte is Li α M β X γ The material is represented by the formula: where α, β, and γ are values ​​greater than 0. M includes at least one metal element other than Li and a metalloid element. X is one or more elements selected from the group consisting of F, Cl, Br, and I. Here, the metalloid elements are B, Si, Ge, As, Sb, and Te. The metal elements are all elements in Groups 1 to 12 of the periodic table excluding hydrogen, and all elements in Groups 13 to 16 of the periodic table excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, metalloid elements or metal elements are a group of elements that can become cations when forming inorganic compounds with halogen compounds.

[0070] Specific examples of halide solid electrolytes are Li3YX6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, and Li3(Al, Ga, In)X6. "(Al, Ga, In)" represents at least one element selected from the group consisting of the elements in parentheses. In other words, "(Al, Ga, In)" is synonymous with "at least one selected from the group consisting of Al, Ga, and In." The same applies to other elements.

[0071] Examples of complex hydride solid electrolytes are LiBH4-LiI and LiBH4-P2S5.

[0072] An example of a polymer solid electrolyte is a compound of a polymer compound and a lithium salt. The polymer compound may have an ethylene oxide structure. By having an ethylene oxide structure, a large amount of lithium salt can be contained, and ionic conductivity can be further increased. Examples of lithium salts are LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. At least one lithium salt selected from the group consisting of the above lithium salts can be used alone as the lithium salt. Alternatively, a mixture of two or more lithium salts selected from the group consisting of the above lithium salts can be used as the lithium salt.

[0073] The shape of the solid electrolyte is, for example, needle-like, particulate, spherical, or oval-spherical. When the solid electrolyte is particulate or spherical, the average particle size is, for example, 0.1 μm or more and 50 μm or less.

[0074] The positive electrode 10 has a positive electrode current collector 11 and a positive electrode active material layer 12. The positive electrode active material layer 12 is located between the positive electrode current collector 11 and the solid electrolyte layer 30.

[0075] The material of the positive electrode current collector 11 is not limited to a specific material, and materials commonly used in batteries can be used. Examples of materials for the positive electrode current collector 11 include copper, copper alloy, aluminum, aluminum alloy, stainless steel, nickel, titanium, carbon, lithium, indium, and conductive resin. The shape of the positive electrode current collector 11 is also not limited to a specific shape. Examples of shapes include foil, film, and sheet. The surface of the positive electrode current collector 11 may be uneven.

[0076] The positive electrode active material layer 12 includes, for example, a positive electrode active material. The positive electrode active material includes, for example, a material capable of absorbing and releasing metal ions, such as lithium ions. The positive electrode active material may be, for example, a material containing at least one selected from the group consisting of cobalt, nickel, manganese, and aluminum, lithium, and oxygen. Examples of the positive electrode active material include lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(Ni, Co, Al)O2, Li(Ni, Co, Mn)O2, and LiCoO2. In particular, using a lithium-containing transition metal oxide as the positive electrode active material can reduce manufacturing costs and increase the average discharge voltage. To increase the energy density of the battery, the positive electrode active material may be lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide. The positive electrode active material may be LiCoO2, Li(Ni, Co, Mn)O2, or Li(Ni, Co, Al)O2. The positive electrode active material layer 12 may further contain at least one selected from the group consisting of a solid electrolyte, a conductive material, and a binder, as necessary. The positive electrode active material layer 12 may contain a mixed material of positive electrode active material particles and solid electrolyte particles.

[0077] The positive electrode active material is, for example, in the form of particles. When the positive electrode active material is in the form of particles, the average particle size of the positive electrode active material is, for example, 100 nm or more and 50 μm or less.

[0078] The average charge / discharge potential of the positive electrode active material is 3.7V vs Li / Li, relative to the redox potential of Li metal. + or more. The average charge / discharge potential of the positive electrode active material can be determined, for example, from the average voltage when Li is desorbed from and inserted into the positive electrode active material using Li metal as the counter electrode. When a material other than Li metal is used as the counter electrode, the average potential may be determined by adding the potential of the material used for the counter electrode relative to Li metal to the charge / discharge curve. When a material other than Li metal is used as the counter electrode, the all-solid-state battery may be charged / discharged at a relatively low current value, taking ohmic loss into consideration.

[0079] At least one selected from the group consisting of the positive electrode 10, the solid electrolyte layer 30, and the negative electrode 20 may contain a binder to improve adhesion between particles. The binder is used, for example, to improve the binding properties of the materials constituting the electrode. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose. The binder may be a copolymer of two or more materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Alternatively, a mixture of two or more materials selected from these may be used as the binder.

[0080] At least one of the positive electrode 10 and the negative electrode 20 may contain a conductive additive to improve electronic conductivity. Examples of the conductive additive include graphites, carbon blacks, conductive fibers, metal powders, conductive whiskers, conductive metal oxides, and conductive polymers. Examples of graphites include natural graphite and artificial graphite. Examples of carbon blacks include acetylene black and ketjen black. Examples of conductive fibers include carbon fiber and metal fiber. Examples of metal powders include carbon fluoride and aluminum. Examples of conductive whiskers include zinc oxide and potassium titanate. An example of a conductive metal oxide is titanium oxide. Examples of conductive polymer compounds include polyaniline, polypyrrole, and polythiophene. Using a conductive additive containing carbon can reduce costs.

[0081] Examples of the shape of the all-solid-state battery 1 include a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, and a laminate type.

[0082] The operating temperature of the all-solid-state battery 1 is not limited to a specific temperature. An example of the temperature is -50°C or higher and 100°C or lower. The higher the operating temperature of the all-solid-state battery 1, the more the ionic conductivity can be improved, and therefore the all-solid-state battery 1 can operate at a higher output.

[0083] The all-solid-state battery 1 according to this embodiment is charged at a constant current of 0.05 C to −0.62 V using, for example, the negative electrode 20 and the LiIn counter electrode. Thereafter, the all-solid-state battery 1 is discharged at a constant current of 0.05 C to 1.4 V. At this time, the discharge capacity of the all-solid-state battery 1 is 2500 mAh / g or more and 3 mAh / cm 2 By including the above-described negative electrode in the all-solid-state battery 1, it is possible to provide an all-solid-state battery 1 that can more reliably have a high discharge capacity.

[0084] In the charge / discharge test, the discharge capacity of the all-solid-state battery 1 was 3000 mAh / g or more and 4 mAh / cm 2In the charge-discharge test, the discharge capacity of the all-solid-state battery 1 is 3000 mAh / g or more and 5 mAh / cm 2 By including the above-described negative electrode in the all-solid-state battery 1, it is possible to provide an all-solid-state battery 1 that can more reliably have a high discharge capacity. [Example]

[0085] The present disclosure will be described in detail below, but the present invention is not limited to the following examples.

[0086] <Sample No. 1> [Preparation of negative electrode] The negative electrode current collector used was an electrolytic copper foil whose surface was roughened by electrolytically depositing copper. A silicon thin film was formed on the negative electrode current collector using an RF sputtering device, producing a negative electrode according to Sample No. 1. The conditions for forming the silicon thin film are shown in Table 1. In Table 1, the thickness of the silicon thin film was calculated by calculating the areal density of silicon using inductively coupled plasma (ICP) emission spectroscopy, and then multiplying this areal density value by the true density of silicon (2.33 g / cm). 3 The silicon content in the negative electrode active material layer of Sample No. 1 was 95 mass % or more.

[0087] [Preparation of sulfide solid electrolyte materials] In a glove box with an argon atmosphere and a dew point of -60°C or less, Li2S and P2S5 were weighed into a mortar so that the molar ratio of Li2S:P2S5 was 75:25. These were pulverized and mixed in the mortar to obtain a mixture. The obtained mixture was placed in a Fritsch planetary ball mill P-7 and milled at 510 revolutions per minute (rpm) for 10 hours to obtain a glassy solid electrolyte. The glassy solid electrolyte was heat-treated at 270°C for 2 hours in an inert gas atmosphere. This yielded a glass-ceramic solid electrolyte, Li2S-P2S5.

[0088] [Battery construction] 80 mg of the solid electrolyte was weighed and placed in an electrically insulating cylinder, to which the negative electrode of Sample No. 1, punched to a diameter of 9.4 mm, was added, and the cylinder was press-molded at 370 MPa to produce a laminate consisting of the negative electrode and the solid electrolyte layer.

[0089] Next, a 200 μm thick layer of metallic indium, a 300 μm thick layer of metallic lithium, and a 200 μm thick layer of metallic indium were placed in that order on the solid electrolyte layer of this laminate to produce a three-layer laminate consisting of an anode, a solid electrolyte layer, and an indium-lithium-indium layer.The three-layer laminate was then pressure-molded at 80 MPa to produce a two-electrode electrochemical cell consisting of an anode, a solid electrolyte layer, and a counter electrode.

[0090] Next, current collectors containing stainless steel were placed on the top and bottom of the two-electrode electrochemical cell, and then current collecting leads were attached to the current collectors.

[0091] Next, an electrically insulating ferrule was used to isolate and seal the inside of the electrically insulating outer cylinder from the outside atmosphere.

[0092] A two-electrode electrochemical cell was sandwiched between four bolts from above and below, and a pressure of 150 MPa was applied to the laminate to obtain a battery according to Sample No. 1, which had a negative electrode, a solid electrolyte layer, and a counter electrode. The battery according to Sample No. 1 had a negative electrode as the working electrode.

[0093] [Charge / discharge test] A charge / discharge test of the battery according to Sample No. 1 was carried out under the following conditions.

[0094] The battery was placed in a thermostatic chamber at 25°C.

[0095] The theoretical capacity of the silicon negative electrode active material is 4200 mAh / g. The battery of Sample No. 1 was charged at a constant current of 0.05 C for 20 hours to a capacity of 3000 mAh / g, which corresponds to approximately 70% of this value. Charging was terminated when the potential of the working electrode relative to the counter electrode reached −0.62 V. The battery was then discharged at a current of 0.05 C, and discharge was terminated at a voltage of 1.4 V. The initial discharge capacity was converted to a value per unit mass and per unit area of ​​silicon. The results are shown in Table 2 and Figure 4. The conditions for the charge-discharge test of Sample No. 1 were the same as those for the charge-discharge test, in which the battery was charged to 0 V and then discharged to 2.02 V relative to the potential of metallic lithium.

[0096] <Samples No. 2 to No. 6> Batteries according to Samples No. 2 to No. 5 were obtained in the same manner as Sample No. 1, except that the thickness of the electrolytic copper foil and the conditions for forming the silicon thin film were adjusted to the conditions shown in Table 1. A battery according to Sample No. 6 was produced in the same manner as Sample No. 1, except that the conditions for forming the silicon thin film were changed to the conditions shown in Table 1 and that a stainless steel foil whose surface had been roughened with #2000 sandpaper was used as the negative electrode current collector. Additionally, charge-discharge tests were conducted on the batteries according to Samples No. 2 to No. 5 in the same manner as Sample No. 1. The results are shown in Table 2 and FIG. 4. The silicon content in the negative electrode active material layer according to Samples No. 2 to No. 5 was 95 mass% or more.

[0097] <Sample No. 7> [Preparation of negative electrode material] The sulfide solid electrolyte material and silicon powder were weighed and added to an agate mortar so that the ratio of the mass of silicon to the total mass of the sulfide solid electrolyte material and silicon powder was 70 mass%. The silicon powder had an average particle size of 2.5 μm. This produced a negative electrode material according to Sample No. 7.

[0098] [Battery construction] A mixture was obtained by stacking 80 mg of Li2S-P2S5, 1.64 mg of the negative electrode material of Sample No. 7, and a 10 μm-thick electrolytic copper foil in this order in an electrically insulating cylinder. This mixture was press-molded at a pressure of 370 MPa to produce a laminate consisting of a negative electrode and a solid electrolyte layer. A battery of Sample No. 7 was obtained in the same manner as Sample No. 1, except for using this laminate.

[0099] <Samples No. 3-1 to No. 5-4> Batteries according to samples No. 3-1 to No. 5-4 were obtained in the same manner as sample No. 1, except that the negative electrodes according to samples No. 3 to No. 5 were heat-treated under the conditions shown in Table 3.

[0100] <Sample No. 1-5> [Preparation of positive electrode] A 300 μm thick piece of metallic lithium was punched out to a diameter of 17 mm. This metallic lithium was attached to the inner surface of a stainless steel (SUS) sealing plate to prepare the positive electrode of Sample No. 1-5. At this time, no current collector was placed between the metallic lithium and the sealing plate.

[0101] [Preparation of non-aqueous electrolyte] A separator was placed on the metallic lithium. A microporous polyethylene film (thickness: 17.6 μm) manufactured by Asahi Kasei Chemicals Corporation was used as the separator. A negative electrode according to Sample No. 1-5, punched into a circular shape with a diameter of 9.4 mm, was placed on the separator. A nonaqueous electrolyte solution was then added dropwise. The nonaqueous electrolyte solution was prepared by dissolving LiPF6 at a concentration of 1.5 mol / L in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 3:5:2.

[0102] [Battery construction] The positive electrode material, nonaqueous electrolyte, and negative electrode of Sample No. 1-5 were placed in the battery case. Next, to adjust the thickness of the electrode plate assembly, a disc spring was placed on the negative electrode current collector, and a stainless steel battery case was placed on top of that. Using a crimping machine, the open end of the battery case was crimped via an electrically insulating polypropylene packing, thereby producing a coin-type battery of Sample No. 1-5.

[0103] <Samples No. 3-5 to No. 5-7> Coin-type batteries according to Samples Nos. 3-5 to 5-7 were obtained in the same manner as Samples Nos. 1-5, except for changing the negative electrode and heat treatment conditions as shown in Table 4. Note that "-" in the heat treatment conditions column in Table 4 indicates that heat treatment was not performed.

[0104] [Charge / discharge test] Charge-discharge tests were conducted on the batteries of Sample No. 7 and Nos. 3-1 to 5-4 using the same method as Sample No. 1. The coin-type batteries of Samples 3-5 to 5-7 used metallic lithium as the counter electrode. Therefore, the coin-type batteries of Samples 3-5 to 5-7 were charged at a constant current to 0 V relative to the potential of the metallic lithium, and then discharged to 2 V. The results are shown in Tables 3 to 5 and Figures 5 and 6.

[0105] [Evaluation of initial charge / discharge capacity characteristics] The theoretical capacity of the negative electrode active material, silicon, is 4200mAh / g. A constant current charge of 3000mAh / g, equivalent to approximately 70% of this value, was performed at a rate of 0.05C. Charging was terminated when the potential of the working electrode relative to the LiIn counter electrode reached -0.62V. Next, the battery was discharged at a current of 0.05C, and discharge was terminated at a voltage of 1.4V. This allowed the initial charge / discharge capacity characteristics to be evaluated.

[0106] The obtained initial charge capacity and initial discharge capacity were converted into those per unit mass and unit area of ​​silicon.

[0107] [Evaluation of charge / discharge cycle characteristics] The charge-discharge cycle characteristics of the battery evaluated for the initial charge-discharge capacity were evaluated. The battery was charged at a constant current of 0.3 C for a capacity of 3000 mAh / g. Charging was terminated when the potential of the working electrode relative to the LiIn counter electrode reached -0.62 V.

[0108] Next, the battery was charged at a constant voltage of -0.62 V until the current decayed to 0.05 C. It was then discharged at a current value corresponding to a 0.3 C rate, and discharge was terminated at a voltage of 1.4 V. This charge-discharge cycle was repeated. The discharge capacity after a given cycle relative to the initial discharge capacity was defined as the capacity retention rate. The results are shown in Tables 3 to 5.

[0109] Figure 3 is a photograph of the surface of the negative electrode of Sample No. 6. As shown in Figure 3, when a thin silicon film was formed on the stainless steel foil of Sample No. 6, the thin silicon film peeled off from the stainless steel foil. Therefore, a battery of Sample No. 6 could not be fabricated, and a charge-discharge test could not be performed. In Sample No. 6, the thickness of the thin silicon film was approximately 6 μm.

[0110] On the other hand, in the negative electrodes of Samples 1 to 5, the silicon thin film formed on the copper foil did not peel off. Figure 2 is an image of the cross section of the negative electrode of Sample 4 observed with a scanning electron microscope (SEM). As shown in Figure 2, in Sample 4, a silicon thin film was formed on the copper foil. Since the negative electrode current collector used was an electrolytic copper foil whose surface was roughened by electrolytically depositing copper, unevenness was formed on the surface of the copper foil. This is thought to have improved the adhesion between the copper foil and the silicon thin film. In addition, the use of methods such as sputtering to form the silicon thin film generates heat. This can cause the copper contained in the copper foil to diffuse into the silicon thin film. As a result, it is thought to have more sufficiently improved the adhesion between the copper foil and the silicon thin film.

[0111] In Sample No. 5, the thickness of the silicon thin film formed on the copper foil was 7.80 μm. Therefore, by using copper foil as the negative electrode current collector, it was possible to increase the thickness of the silicon thin film.

[0112] 4 is a graph showing the relationship between the thickness of the negative electrode active material layer and the initial discharge capacity in the batteries according to Samples No. 1 to No. 3 and Sample No. 5. In FIG. 4, the horizontal axis represents the thickness of the silicon thin film, and the vertical axis represents the initial discharge capacity per unit mass (mAh / g) or the initial discharge capacity per unit area (mAh / cm 2 4 and Table 2, the batteries according to Samples No. 1 to No. 3 and Sample No. 5 had high initial discharge capacities.

[0113] FIG. 5 is a graph showing the relationship between the thickness of the negative electrode active material layer and the initial discharge capacity per unit mass in the battery according to each sample. In FIG. 5, the horizontal axis shows the thickness of the silicon thin film, and the vertical axis shows the initial discharge capacity per unit mass (mAh / g). FIG. 6 is a graph showing the relationship between the thickness of the negative electrode active material layer and the initial discharge capacity per unit area in the battery according to each sample. In FIG. 6, the horizontal axis shows the thickness of the silicon thin film, and the vertical axis shows the initial discharge capacity per unit area (mAh / cm 2 As shown in Table 3, the batteries of Samples No. 3-1 to No. 5-4 had a capacity of 3000 mAh / g or more and 4 mAh / cm 2 The batteries according to Samples No. 3-1 to No. 5-4 had an initial discharge capacity of at least 100 mAh. The negative electrodes of the batteries according to Samples No. 3-1 to No. 5-4 were heat-treated. Because copper easily diffuses into silicon, the heat treatment is thought to cause the copper contained in the current collector to diffuse into the silicon contained in the negative electrode active material layer. This is thought to have improved the electronic conductivity of the negative electrode active material layer. The all-solid-state battery according to this embodiment may have an ion conduction path only at the contact surface between the solid electrolyte layer and the negative electrode active material layer. However, the provision of ion and electron conduction paths in the negative electrode active material layer is thought to have contributed to the increase in the initial charge / discharge capacity. Additionally, due to this configuration, the batteries according to Samples No. 3-1 to No. 5-4 are thought to have excellent cycle characteristics.

[0114] As shown in Table 3, the batteries of Samples 3-1 to 5-4 had a capacity retention rate of 80% or more after 50 cycles. In the batteries of Samples 3-1 to 5-4, the sulfide solid electrolyte was not substantially contained within the negative electrode active material layer. That is, in the batteries of Samples 3-1 to 5-4, the sulfide solid electrolyte was in contact only with the negative electrode active material layer. Therefore, in the batteries of Samples 3-1 to 5-4, contact between the copper foil of the negative electrode current collector and the sulfide solid electrolyte was suppressed. This is thought to be because the generation of copper sulfide, which could become a resistive layer, was suppressed in the negative electrode layer of the batteries of Samples 3-1 to 5-4. This is thought to be why the batteries of Samples 3-1 to 5-4 had high cycle characteristics.

[0115] As shown in Table 4, the batteries of Samples 3-5 to 5-7 had initial discharge capacities of 3000 mAh / g or more. Furthermore, it was found that the initial discharge capacities of Samples 3-5 to 5-7 were not significantly reduced even when the thickness of the negative electrode active material layer was increased. In batteries using a nonaqueous electrolyte, the nonaqueous electrolyte easily penetrates the negative electrode active material layer, allowing ion conduction paths to be formed throughout the negative electrode active material layer. This is believed to be why the batteries using a nonaqueous electrolyte exhibited excellent initial discharge capacities. On the other hand, the batteries of Samples 3-6 and 5-7 exhibited lower capacity retention rates than the batteries using a solid electrolyte layer. Sample 3-6 had a capacity retention rate of 40% after 40 cycles. Sample 5-7 had a capacity retention rate of 26% after 35 cycles. In batteries using a nonaqueous electrolyte, the entire negative electrode active material may react with the nonaqueous electrolyte during charge and discharge. This is believed to have deactivated the silicon contained in the negative electrode active material. From the above results, it is considered that it is difficult for a battery using a non-aqueous electrolyte to have both a high energy density and excellent cycle characteristics.

[0116] As shown in Table 5, the battery according to Sample No. 7 contained a sulfide solid electrolyte in the negative electrode active material layer, and therefore had an initial discharge capacity of 3000 mAh / g or more. However, repeated charge / discharge cycles in the battery according to Sample No. 7 could cause a reaction between the copper foil of the negative electrode current collector and the sulfide solid electrolyte contained within the negative electrode active material, resulting in the formation of copper sulfide. Copper sulfide could increase the resistance at the interface between the negative electrode current collector and the negative electrode active material layer. As a result, the battery according to Sample No. 7 likely had a lower capacity retention rate than batteries using a solid electrolyte layer.

[0117] [Table 1]

[0118] [Table 2]

[0119] [Table 3]

[0120] [Table 4]

[0121] [Table 5] [Industrial Applicability]

[0122] The battery of the present disclosure can be used, for example, as an all-solid-state lithium-ion secondary battery.

Claims

1. A positive electrode and a negative electrode; a solid electrolyte layer containing a sulfide and located between the positive electrode and the negative electrode; Equipped with the solid electrolyte layer contains a solid electrolyte having lithium ion conductivity, the negative electrode has a negative electrode current collector containing copper as a main component, and a negative electrode active material layer located between the negative electrode current collector and the solid electrolyte layer, the negative electrode active material layer has a plurality of columnar particles, and the content of an electrolyte in the negative electrode active material layer is 5 mass % or less; the columnar particles contain silicon as a main component, the negative electrode active material layer is formed as a single layer of the plurality of columnar particles, The arithmetic mean roughness Ra of the surface of the negative electrode current collector is 0.01 μm or more and 1 μm or less. battery.

2. The negative electrode active material layer has the plurality of columnar particles arranged along the surface of the negative electrode current collector. having a structure covering the surface, The battery of claim 1 .

3. The thickness of the negative electrode active material layer is 4 μm or more and 20 μm or less. The battery according to claim 1 or 2.

4. The content of the silicon in the negative electrode active material layer is 95% by mass or more. The battery according to any one of claims 1 to 3.

5. The negative electrode active material layer contains copper. The battery of any one of claims 1 to 4.

6. Using the negative electrode and LiIn counter electrode, the voltage was increased to −0.62 V at a current value of 0.05 C. After constant current charging, when the battery was discharged at a constant current of 0.05C to 1.4V, the voltage The discharge capacity of the battery is 2500 mAh / g or more and 3 mAh / cm 2 That's all. The battery of any one of claims 1 to 5.

7. The discharge capacity of the battery in the constant current discharge is 3000 mAh / g or more, and , 4 mAh / cm 2 That's all. The battery of claim 6.

8. The discharge capacity of the battery in the constant current discharge is 3000 mAh / g or more, and , 5 mAh / cm 2 That's all. The battery of claim 7.

9. A method for manufacturing the battery according to any one of claims 1 to 8, comprising: depositing the silicon on the negative electrode current collector by sputtering. 、 How batteries are manufactured.

10. After the sputtering, heat treating the silicon at 300°C or less. The method for manufacturing the battery according to claim 9 .

Images