Solid-state battery and method for manufacturing solid-state battery

Abstract

The object of the present disclosure is to provide a solid-state battery in which a decrease in capacity maintenance rate is suppressed. The solid-state battery has a negative electrode layer containing a negative electrode active material, a positive electrode layer containing a positive electrode active material, and a solid electrolyte layer containing a solid electrolyte, which is positioned between the negative electrode layer and the positive electrode layer, the negative electrode layer further containing an interface-forming agent, the interface-forming agent containing at least one selected from a metal element and a metalloid element, the metal element and the metalloid element being capable of becoming a cation that conducts a solid electrolyte in the solid electrolyte layer, the cation not participating in an electrode reaction and having an ionic radius of 0.1 to 0.5 A, and an ion conductivity lower than that of an ion participating in an electrode reaction, at least one of an interface of the solid electrolyte layer with the positive electrode layer and an interface of the solid electrolyte layer with the negative electrode layer having a dendritic structure.

Description

Technical Field

[0001] This disclosure relates to solid-state batteries and methods for manufacturing solid-state batteries. Background Technology

[0002] In recent years, with the rapid popularization of information-related and communication devices such as personal computers, cameras, and mobile phones, the development of batteries as their power source has received increasing attention. Furthermore, in the automotive industry and other sectors, the development of high-output, high-capacity batteries for electric vehicles or hybrid vehicles is underway.

[0003] Lithium-ion batteries, among which lithium batteries are used as negative electrodes, have attracted attention because they use lithium, which has the highest ionization tendency among metals, and thus can achieve high output voltage due to the large potential difference between the negative electrode and the positive electrode.

[0004] In addition, solid-state batteries have attracted attention for using solid electrolytes instead of electrolytes containing organic solvents as the electrolyte between the positive and negative electrodes.

[0005] Patent Document 1 discloses an all-solid-state battery in which the side peripheral surface of the positive electrode layer is covered by an insulating layer. Patent Document 1 describes that by providing such an insulating layer, short circuits can be suppressed, and by making the insulating layer contain insulating fillers and forming fine irregularities on the surface of the insulating layer, the solid electrolyte layer is less likely to peel off from the insulating layer.

[0006] Patent Document 2 discloses an all-solid-state battery having a solid electrolyte layer containing hollow particles. Patent Document 2 describes how, during initial charging, when expansion stress is generated in the horizontal direction of the electrode body due to the expansion of the active material, the hollow particles yield and collapse, thereby buffering the expansion stress and preventing the formation of severe gaps and cracks in the solid electrolyte layer that could affect battery performance.

[0007] Existing technical documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-039876

[0009] Patent Document 2: Japanese Patent Application Publication No. 2019-192563 Summary of the Invention

[0010] However, as one of the challenges in conventional solid-state batteries, the following problem exists: the interface between the solid electrolyte layer and the negative or positive electrode layer peels off due to the expansion and contraction of the active material during charging and discharging, resulting in a decrease in capacity retention. Even with techniques such as those described in Patent Document 1, which use fillers to create unevenness at the interface, or those described in Patent Document 2, which use hollow particles to buffer expansion stress, it is difficult to sufficiently suppress the peeling off of the solid electrolyte layer from the negative or positive electrode layer after charging and discharging. This is especially true in solid-state batteries using Si-based or Sn-based negative electrode active materials, which have a relatively large degree of expansion and contraction during charging and discharging, making it prone to peeling off the solid electrolyte layer from the negative or positive electrode layer after charging and discharging, thus easily leading to a decrease in capacity retention.

[0011] This disclosure was made in view of the above circumstances, and its main objective is to provide a solid-state battery that suppresses the decline in capacity retention and a method for manufacturing the solid-state battery.

[0012] The solid-state battery disclosed herein comprises: a negative electrode layer containing a negative electrode active material, a positive electrode layer containing a positive electrode active material, and a solid electrolyte layer located between the negative electrode layer and the positive electrode layer and containing a solid electrolyte, characterized in that...

[0013] The negative electrode layer further contains an interface forming agent, which contains at least one selected from metallic elements and metalloid elements. The metallic elements and metalloid elements can be converted into cations that conduct the solid electrolyte in the solid electrolyte layer. These cations do not participate in the electrode reaction and have a lower ionic conductivity than the ions that participate in the electrode reaction. The ionic radius of the cation is [missing information]. the following,

[0014] The solid electrolyte layer has a dendritic structure at at least one of its interfaces with the positive electrode layer and with the negative electrode layer.

[0015] In the solid-state battery of this disclosure, the solid electrolyte layer may contain a sulfide-based solid electrolyte.

[0016] In the solid-state battery of this disclosure, the interface forming agent may also contain at least one selected from Ca, Al, Mg, Na and B as the metallic element or the metalloid element.

[0017] In the solid-state battery disclosed herein, the interface forming agent may also be an amorphous glass material containing an oxide of the metal element or an oxide of the quasi-metal element.

[0018] In the solid-state battery of this disclosure, the content of the interface forming agent may be more than 1 part by mass and less than 5 parts by mass relative to 100 parts by mass of the negative electrode active material.

[0019] In the solid-state battery disclosed herein, the negative electrode layer may also contain an active material with Si or Sn as the constituent elements as the negative electrode active material.

[0020] The present disclosure discloses a method for manufacturing a solid-state battery, the solid-state battery comprising: a negative electrode layer containing a negative electrode active material, a positive electrode layer containing a positive electrode active material, and a solid electrolyte layer located between the negative electrode layer and the positive electrode layer and containing a solid electrolyte, the manufacturing method being characterized in that it includes:

[0021] The process of forming a solid electrolyte layer with two flat sides;

[0022] The process of forming the negative electrode layer on one side of the solid electrolyte layer; and

[0023] The process of forming the positive electrode layer on the other side of the solid electrolyte layer.

[0024] The negative electrode layer further contains an interface forming agent, which contains at least one selected from metallic elements and metalloid elements. The metallic elements and metalloid elements can be converted into cations that conduct the solid electrolyte in the solid electrolyte layer. These cations do not participate in the electrode reaction and have a lower ionic conductivity than the ions that participate in the electrode reaction. The ionic radius of the cation is [missing information]. the following,

[0025] The manufacturing method further includes the following steps:

[0026] Within a voltage range where neither the decomposition of the positive electrode active material nor the metal deposition on the negative electrode active material occurs, a charge-discharge cycle is performed on a laminate having the negative electrode layer, the solid electrolyte layer, and the positive electrode layer sequentially at a current value of less than 0.364 mAh for one or more cycles, thereby making at least one of the interfaces between the solid electrolyte layer and the positive electrode layer and between the solid electrolyte layer and the negative electrode layer a dendritic structure.

[0027] According to this disclosure, a solid-state battery that suppresses the decline in capacity retention can be provided. Attached Figure Description

[0028] Figure 1 This is a cross-sectional schematic diagram showing an example of a solid-state battery according to the present disclosure.

[0029] Figure 2 This is an image of the Ca element mapping analysis of the cross-section of the solid battery obtained in Example 2.

[0030] Figure 3 This is a graph showing the capacity retention of the solid-state batteries obtained in Examples 1, 2 and Comparative Example 1.

[0031] Explanation of reference numerals in the attached figures

[0032] 11. Negative electrode active material layer

[0033] 12 Negative current collector

[0034] 13 Negative Electrode Layer

[0035] 14 Positive electrode active material layer

[0036] 15 Positive current collector

[0037] 16 Positive electrode layer

[0038] 17 Solid electrolyte layer

[0039] 100 Solid-state batteries Detailed Implementation

[0040] In this disclosure, the "~" in the numerical range refers to the numerical values ​​recorded before and after it as the lower limit and upper limit.

[0041] 1. Solid-state battery

[0042] The solid-state battery disclosed herein comprises: a negative electrode layer containing a negative electrode active material, a positive electrode layer containing a positive electrode active material, and a solid electrolyte layer located between the negative electrode layer and the positive electrode layer and containing a solid electrolyte, characterized in that...

[0043] The negative electrode layer further contains an interface forming agent, which contains at least one selected from metallic elements and metalloid elements. The metallic elements and metalloid elements can be converted into cations that conduct the solid electrolyte in the solid electrolyte layer. These cations do not participate in the electrode reaction and have a lower ionic conductivity than the ions that participate in the electrode reaction. The ionic radius of the cation is [missing information]. the following,

[0044] The solid electrolyte layer has a dendritic structure at at least one of its interfaces with the positive electrode layer and with the negative electrode layer.

[0045] Figure 1 This is a cross-sectional schematic diagram illustrating an example of a solid-state battery according to the present disclosure. For example... Figure 1 As shown, the solid-state battery 100 includes: a negative electrode layer 13 comprising a negative electrode active material layer 11 and a negative electrode current collector 12, a positive electrode layer 16 comprising a positive electrode active material layer 14 and a positive electrode current collector 15, and a solid electrolyte layer 17 located between the negative electrode layer 13 and the positive electrode layer 16. The solid electrolyte layer 17 has a dendritic structure at both its interface with the negative electrode layer 13 and its interface with the positive electrode layer 16.

[0046] In conventional solid-state batteries, if the active material expands or contracts during charging and discharging, delamination occurs at the interface between the solid electrolyte layer and the negative electrode layer, or between the solid electrolyte layer and the positive electrode layer, resulting in a decrease in capacity retention. In contrast, in the solid-state battery of this disclosure, at least one of the interfaces between the solid electrolyte layer and the positive electrode layer, and the interface between the solid electrolyte layer and the negative electrode layer, has a dendritic structure. Interfaces with dendritic structures exhibit a high anchoring effect, therefore, even if the active material expands or contracts, the interface is less prone to delamination, thus suppressing the decrease in capacity retention caused by interface delamination.

[0047] Furthermore, in this disclosure, an interface having a dendritic structure is sometimes simply referred to as a dendritic interface.

[0048] In conventional solid-state batteries, the interface of the solid electrolyte layer is mostly flat. On the other hand, in the solid-state battery of this disclosure, by containing an interface forming agent in the negative electrode layer, at least one of the interfaces between the solid electrolyte layer and the positive electrode layer, and the interface between the solid electrolyte and the negative electrode layer, becomes an interface with a dendritic structure.

[0049] The interface forming agent used in the solid-state battery disclosed herein contains at least one selected from metallic and metalloid elements. These metallic and metalloid elements can be converted into cations that conduct the solid electrolyte in the solid electrolyte layer. These cations do not participate in the electrode reaction and have a lower ionic conductivity than the ions that participate in the electrode reaction. The ionic radius of the cations is [missing information]. The following describes the process of low-rate charge-discharge of a laminate containing a negative electrode layer, a solid electrolyte layer, and a positive electrode layer, in sequence, with the aforementioned metal or near-metal element in the interface forming agent of the negative electrode layer undergoing cationization via an electrochemical reaction. The generated cations are then conducted from the negative electrode layer to the solid electrolyte layer, where they remain and are retained. Since the ionic radius of the aforementioned cations is... Therefore, although it can move within the battery, its ionic conductivity is lower than that of ions participating in the electrode reaction. Consequently, it does not reach the positive electrode layer but remains in the solid electrolyte layer. When the concentration of the aforementioned cations in the solid electrolyte layer increases, the portion with the high cation concentration extends in a dendritic pattern towards at least one side of the positive and negative electrode layers. Furthermore, the aforementioned cations undergo compositional changes by remaining within the solid electrolyte, forming an interface with a dendritic structure. It is believed that the dendritic portion of the interface of the solid electrolyte layer contains the solid electrolyte whose composition has changed due to the aforementioned cations, thus becoming an interface with a higher anchoring effect and exhibiting a stripping inhibition effect.

[0050] Furthermore, lithium dendrites, which often cause problems in conventional lithium-ion batteries, are formed by the deposition of metallic lithium. The dendritic interface of the solid-state battery disclosed herein can be distinguished from the interface formed by lithium dendrites in that the solid electrolyte exhibits a dendritic structure due to the compositional change caused by cations generated by the interface forming agent.

[0051] Furthermore, in this disclosure, ions that do not participate in the electrode reaction are those that undergo irreversible reactions with the active material or do not react and therefore do not participate in the extraction of electrical energy to the external circuitry of the battery. Ions that participate in the electrode reaction change the potential of the active material through reversible insertion and removal, generating energy for extracting electrical energy to the external circuitry of the battery. For example, in the case of a lithium-ion battery, the ions participating in the electrode reaction are lithium ions, and the ions that do not participate in the electrode reaction are ions of metal elements or near-metallic elements other than lithium ions.

[0052] In this disclosure, the term "dendritic structure" refers to a patterned structure with branches, like a tree branch. Examples include structures with a trunk and multiple branches branching from the trunk, structures with multiple trunks extending from one point, and structures formed by combining these trunks. Furthermore, in this disclosure, the trunk may or may not have branches branching from it.

[0053] This dendritic structure can be observed when viewing a cross-section obtained by cutting a solid electrolyte layer along its thickness direction at a magnification of 500 to 1000 times.

[0054] Furthermore, in the cross-section obtained by cutting the solid electrolyte layer along its thickness direction, the number of main branches extending from the solid electrolyte layer at the dendritic interface of the solid electrolyte layer is preferably 5 or more, more preferably 7 or more, and even more preferably 10 or more within a 100 μm range. On the other hand, the number of the aforementioned main branches is preferably 40 or less, more preferably 25 or less, and even more preferably 20 or less. Dendritic structures with the number of main branches within the above-mentioned range are particularly effective in suppressing interfacial delamination of the solid electrolyte layer.

[0055] In addition, the dendritic interface of the solid electrolyte layer preferably has a dendritic structure throughout the entire interface.

[0056] The materials of the negative electrode layer, positive electrode layer and solid electrolyte layer constituting the solid-state battery of this disclosure will be described in detail below.

[0057] [Negative electrode layer]

[0058] The solid-state battery disclosed herein has a negative electrode layer containing at least a negative electrode active material and an interface forming agent. It can be a single layer or multiple layers, but the layer that forms the interface with the solid electrolyte is preferably a layer containing an interface forming agent.

[0059] The solid-state battery disclosed herein has a negative electrode layer that typically comprises: a negative electrode active material layer containing at least a negative electrode active material and an interface forming agent, and a negative electrode current collector, wherein the negative electrode active material layer forms an interface with a solid electrolyte layer. The negative electrode layer comprising the negative electrode active material layer and the negative electrode current collector will be described in detail below.

[0060] [Negative electrode active material layer]

[0061] The negative electrode active material layer contains at least a negative electrode active material and an interface forming agent, and may also contain solid electrolyte, conductive material and adhesive as needed.

[0062] Examples of anode active materials include carbon-based, Si-based, and Sn-based anode active materials. From the viewpoint that a large degree of expansion and contraction during charging and discharging can effectively exert the effects of this disclosure, active materials with Si or Sn as constituent elements are preferred. From the viewpoint of high energy density, Si-based anode active materials are more preferred.

[0063] Examples of active anode materials based on Si include elemental Si, Si alloys, silicon oxides, silicon carbides, and silicon nitrides. Elements other than Si contained in Si alloys include Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti.

[0064] Examples of Sn-based anode active materials include elemental Sn, Sn alloys, tin oxides, and tin nitrides. Examples of elements other than Sn contained in Sn alloys include Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, Si, and Mg.

[0065] The shape of the negative electrode active material is not particularly limited; it can be granular.

[0066] The average particle size (D50) of the negative electrode active material is not particularly limited; for example, it can be 0.1–10 μm or 0.5–5 μm.

[0067] Furthermore, in this disclosure, unless otherwise specified, the average particle size is the median diameter (D50) obtained by laser diffraction / scattering particle size distribution measurement based on volume. The median diameter (D50) is the diameter (volume-average diameter) at which the cumulative volume of particles arranged sequentially from the smallest particle reaches half (50%) of the total volume.

[0068] The content of negative electrode active material in the negative electrode active material layer is not particularly limited. For example, when the total mass of the negative electrode active material layer is 100% by mass, it can be 20-90% by mass or 30-60% by mass.

[0069] The interface forming agent contained in the negative electrode active material layer is a reagent used to form a dendritic structure at the interface between the solid electrolyte layer and the negative electrode layer or the positive electrode layer.

[0070] The interface forming agent contains at least one element selected from metallic and metalloid elements. These metallic and metalloid elements can be converted into cations that conduct the solid electrolyte in the solid electrolyte layer. These cations do not participate in the electrode reaction and have a lower ionic conductivity than the ions that participate in the electrode reaction. The ionic radius of the cations is [missing information]. The following describes the role of the metal or metalloid element contained in the interface forming agent in forming a dendritic structure at the interface between the solid electrolyte layer and the negative or positive electrode layer, as described above. Furthermore, the interface forming agent may also contain other metal or metalloid elements that do not participate in the electrode reaction and cannot participate in the formation of the dendritic interface.

[0071] From the perspective of ionic conductivity, the ionic radius of the above cations is That's all.

[0072] Furthermore, in this disclosure, the ionic radius is the Shannon ionic radius. For example, Shannon et al.'s "Revised Effective Ionic Radii and Systematic Studies of Interatomie Distances in Halides and Chaleogenides", Acta Cryst. A32, (1976) 751, describes Shannon's ionic radius.

[0073] Furthermore, when the negative electrode layer or positive electrode layer contains a solid electrolyte, it is preferable that the aforementioned cations are ions that conduct the solid electrolyte in the negative electrode layer or positive electrode layer.

[0074] In this disclosure, the solid electrolyte layer contains a sulfide-based solid electrolyte, and the cation selected from at least one of the aforementioned metal elements and metalloid elements in the surfactant is preferably conducted within the sulfide-based solid electrolyte. In this case, during the low-rate charge-discharge reaction process used to form the dendritic interface, the aforementioned cation electrochemically conducts the aforementioned sulfide-based solid electrolyte, and by remaining within the sulfide-based solid electrolyte layer, a compositional change occurs, thereby enabling the dendritic interface of the solid electrolyte layer to form an interface with a higher anchoring effect. Furthermore, in this disclosure, it is preferable that the solid electrolyte contained throughout the solid-state battery is a sulfide-based solid electrolyte.

[0075] In the case of lithium-ion batteries, the ions participating in the electrode reaction are lithium ions. As a conductive sulfide-based solid electrolyte, it does not participate in the electrode reaction of lithium-ion batteries, has a lower ionic conductivity than lithium ions, and its ionic radius is... The following are examples of cations of metallic or metalloid elements, such as Ca. 2+ Al 3+ Mg 2+ Na + B 3+ Etc. Among them, from the viewpoint of easily forming dendritic interfaces with high anchoring effect, Ca is preferred. 2+ .

[0076] Therefore, the interface forming agent used in this disclosure contains at least one metallic or near-metallic element selected from Ca, Al, Mg, Na, and B as a metal element or near-metallic element that can participate in the formation of a dendritic interface. Preferably, it contains a metallic element that can participate in the formation of a dendritic interface; more preferably, it contains at least one selected from Ca and Al; and particularly preferably, it contains at least Ca.

[0077] Furthermore, in the interface forming agent, the metallic or near-metallic elements that can participate in the formation of dendritic interfaces are preferably contained in oxide form. Specifically, the interface forming agent preferably contains an oxide of at least one metallic or near-metallic element selected from Ca, Al, Mg, Na, and B. The interface forming agent preferably contains a metal oxide that can participate in the formation of dendritic interfaces, more preferably contains at least one selected from CaO and Al₂O₃, and particularly preferably contains at least CaO.

[0078] Furthermore, from the viewpoint of easily forming dendritic interfaces with high anchoring effects, the interface forming agent is preferably a glass material, and more preferably an amorphous glass material such as glass powder or glass fiber. Additionally, it is desirable to use glass with a relatively large surface area, such as pulverized glass, as the interface forming agent.

[0079] The interface forming agent used in this disclosure may be, for example, a glass material containing at least Ca, preferably CaO, and further may contain elements such as Al, Mg, Na, and B.

[0080] The shape of the interface forming agent is not particularly limited; for example, it can be granular or fibrous. The average particle size (D50) of the granular interface forming agent is not particularly limited, but from the viewpoints of easily achieving a suitable specific surface area, easily forming dendritic interfaces, and easily ensuring electron conduction paths, it is preferably 1 to 20 μm, more preferably 5 to 15 μm.

[0081] Commercially available glass materials containing the aforementioned metallic or near-metallic elements that can participate in the formation of dendritic interfaces can be used as interface forming agents. Examples of commercially available products that can be used as interface forming agents include VCAS-140 (product name, manufactured by Vitro Minerals). VCAS-140 is an amorphous glassy calcium aluminosilicate powder, containing CaO and Al₂O₃, as well as Mg, Na, and B.

[0082] The content of the interface forming agent is not particularly limited, but it is preferably 1 part by mass and 5 parts by mass or less relative to 100 parts by mass of the negative electrode active material. If the content of the interface forming agent is above the lower limit, it is easy to form a dendritic interface with a high anchoring effect, while if it is below the upper limit, it is easy to ensure the electron conduction path, thus suppressing the increase in resistance.

[0083] Furthermore, the metal and near-metal elements in the interface forming agent are ionized during the low-rate charging and discharging used to form the dendritic interface and can move within the solid-state battery. Therefore, the content of the interface forming agent is the content of the interface forming agent components contained in the entire solid-state battery, which is the content calculated based on the amount of material added when forming the negative electrode layer.

[0084] In addition, even after low-rate charge-discharge cycles used to form dendritic interfaces, a portion of the interface forming agent retains the metallic or near-metallic elements that can participate in the formation of dendritic interfaces, remaining in the negative electrode layer.

[0085] The solid electrolyte that can be contained in the negative electrode active material layer can be, for example, the same solid electrolyte contained in the solid electrolyte layer described later. Among these, from the viewpoint that the interface between the solid electrolyte layer and the negative electrode layer is prone to becoming a dendritic structure with a high anchoring effect, a sulfide-based solid electrolyte is preferred.

[0086] Furthermore, the average particle size (D50) of the solid electrolyte used in the negative electrode active material layer is not particularly limited, but from the viewpoint of further increasing the contact area between the active material and the solid electrolyte, it is preferably 0.1 to 1.0 μm, and more preferably 0.3 to 0.8 μm.

[0087] The content of solid electrolyte in the negative electrode active material layer is not particularly limited. For example, when the total mass of the negative electrode is 100% by mass, it can be 20-70% by mass or 30-50% by mass.

[0088] The conductive material that can be contained in the negative electrode active material layer can be a known material, such as carbon materials and metal particles. Examples of carbon materials include at least one selected from acetylene black, furnace black, VGCF, carbon nanotubes, and carbon nanofibers. From the viewpoint of electronic conductivity, at least one selected from VGCF, carbon nanotubes, and carbon nanofibers is suitable. Examples of metal particles include particles of Ni, Cu, Fe, and SUS.

[0089] As the adhesive that can be contained in the negative electrode active material layer, known adhesives can be used, such as acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), etc.

[0090] [Negative current collector]

[0091] As the negative current collector, any known current collector can be used, without particular limitation. The material of the negative current collector can be a material that is not alloyed with Li, such as SUS, copper, and nickel.

[0092] There are no particular limitations on the shape of the negative electrode current collector; for example, it can be in various shapes such as foil, plate, or mesh.

[0093] The thickness of the negative current collector can be adjusted appropriately according to the material and shape, without any particular limitation. For example, it can be in the range of 1 to 50 μm or in the range of 5 to 20 μm.

[0094] [Positive electrode layer]

[0095] The solid-state battery disclosed herein has a positive electrode layer containing at least a positive electrode active material, which can be a single layer or multiple layers. Typically, it includes a positive electrode active material layer containing the positive electrode active material and a positive electrode current collector, with the positive electrode active material layer forming an interface with the solid electrolyte layer. The positive electrode layer comprising the positive electrode active material layer and the positive electrode current collector will be described in detail below.

[0096] [Positive electrode active material layer]

[0097] The positive electrode active material layer contains at least a positive electrode active material, and may also contain solid electrolyte, conductive material and binder as needed.

[0098] There are no particular restrictions on the type of positive electrode active material; any material suitable for use as a positive electrode active material in solid-state batteries can be used. Specifically, examples include metallic lithium (Li), lithium alloys, LiCoO2, and LiNi. x Co 1-x O2(0 <x<1)、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2, LiMnO2, Li-Mn spinel substituted with other elements, lithium titanate, lithium metal phosphate, LiCoN, Li2SiO3 and Li4SiO4, transition metal oxides, TiS2, Si, SiO2 and lithium-storing intermetallic compounds, etc.

[0099] Li-Mn spinel with foreign element substitution, such as 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, for example, is Li4Ti5O. 12 Examples of lithium metal phosphates include LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4. Transition metal oxides include V2O5 and MoO3. Lithium-storing intermetallic compounds include Mg2Sn, Mg2Ge, Mg2Sb, and Cu3Sb. Examples of lithium alloys include Li-Au, Li-Mg, Li-Sn, Li-Si, Li-Al, Li-B, Li-C, Li-Ca, Li-Ga, Li-Ge, Li-As, Li-Se, Li-Ru, Li-Rh, Li-Pd, Li-Ag, Li-Cd, Li-In, Li-Sb, Li-Ir, Li-Pt, Li-Hg, Li-Pb, Li-Bi, Li-Zn, Li-Tl, Li-Te, and Li-At.

[0100] A coating layer containing Li-ion-conducting oxides can be formed on the surface of the positive electrode active material. This coating layer helps to suppress the reaction between the positive electrode active material and the solid electrolyte.

[0101] Examples of Li ion-conducting oxides used as coating layers include LiNbO3 and Li4Ti5O. 12 And Li3PO4, etc. The thickness of the coating layer is, for example, 0.1 nm or more, or 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, or 20 nm or less. The coverage of the coating layer on the surface of the positive electrode active material is, for example, 70% or more, or 90% or more.

[0102] The shape of the positive electrode active material is not particularly limited; for example, it can be granular.

[0103] The average particle size (D50) of the positive electrode active material is not particularly limited; for example, it can be 1–20 μm or 5–15 μm.

[0104] The content of positive electrode active material in the positive electrode active material layer is not particularly limited. For example, when the total mass of the positive electrode active material layer is 100% by mass, it can be 50-95% by mass or 70-90% by mass.

[0105] The solid electrolyte that can be contained in the positive electrode active material layer can be, for example, the same solid electrolyte contained in the solid electrolyte layer described later. Among these, from the viewpoint that a dendritic structure with a high anchoring effect can easily be formed at the interface between the solid electrolyte layer and the positive electrode layer, a sulfide-based solid electrolyte is preferred.

[0106] Furthermore, the average particle size (D50) of the solid electrolyte contained in the positive electrode active material layer is not particularly limited, but from the viewpoint of further increasing the contact area between the active material and the solid electrolyte, it is preferably 0.1 to 1.0 μm, and more preferably 0.3 to 0.8 μm.

[0107] The content of solid electrolyte in the positive electrode active material layer is not particularly limited. For example, when the total mass of the positive electrode active material layer is 100% by mass, it can be 5-70% by mass or 30-50% by mass.

[0108] As conductive materials and adhesives that can be contained in the positive electrode active material layer, examples include the same conductive materials and adhesives that can be contained in the negative electrode active material layer.

[0109] [Positive current collector]

[0110] As the positive current collector, any known current collector can be used, without particular limitation. Examples of materials that can be used as the positive current collector include SUS, aluminum, nickel, iron, titanium, and carbon.

[0111] The shape and thickness of the positive current collector are the same as those of the negative current collector described above.

[0112] [Solid electrolyte layer]

[0113] As the solid electrolyte layer of the solid-state battery of this disclosure, a known solid electrolyte suitable for use in solid-state batteries can be appropriately used, such as oxide-based solid electrolytes and sulfide-based solid electrolytes. Among these, from the viewpoint of easily forming a dendritic interface with a high anchoring effect, a sulfide-based solid electrolyte is preferred.

[0114] Examples of sulfide-based solid electrolytes include Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-P₂S₅-GeS₂, LiX-Li₂S-SiS₂, LiX-Li₂S-P₂S₅, LiX-Li₂O-Li₂S-P₂S₅, LiX-Li₂S-P₂O₅, LiX-Li₃PO₄-P₂S₅, and Li₃PS₄. Furthermore, the description of "Li₂S-P₂S₅" refers to a material obtained using a raw material composition containing Li₂S and P₂S₅, and the same applies to other descriptions. Additionally, the "X" in LiX indicates a halogen element. The raw material composition containing LiX may contain one or more types of LiX. When containing two or more types of LiX, the mixing ratio of the two or more types is not particularly limited.

[0115] Examples of LiX-Li2S-SiS2, LiX-Li2S-P2S5, LiX-Li2O-Li2S-P2S5, LiX-Li2S-P2O5, or LiX-Li3PO4-P2S include LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiBr-LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, and LiI-Li3PO4-P2S5. More specifically, examples include 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) and 70(0.06Li2O·0.69Li2S·0.25P2S5)·30LiI.

[0116] Examples of oxide-based solid electrolytes include substances with a garnet-type crystal structure containing the elements Li, La, A (A being at least one of Zr, Nb, Ta, and Al), and O. For example, Li can be used as an oxide-based solid electrolyte. 3+x PO 4-x N x (1≤x≤3) etc.

[0117] In addition, the solid electrolyte can be any of the following: solid electrolyte crystal, amorphous solid electrolyte, and solid electrolyte glass ceramic.

[0118] The shape of solid electrolytes is not particularly limited; they can be granular, plate-like, etc. From a processability point of view, they can be granular.

[0119] Furthermore, the average particle size (D50) of the solid electrolyte is not particularly limited, but from the viewpoint of ionic conductivity, it is preferably 1.0 to 3.0 μm, and more preferably 1.5 to 2.5 μm.

[0120] Solid electrolytes can be used alone or in combination with two or more types. When using two or more solid electrolytes, they can be mixed together.

[0121] The content of solid electrolyte in the solid electrolyte layer is not particularly limited. When the total mass of the solid electrolyte layer is 100% by mass, it is typically 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more. The solid electrolyte layer can be a layer composed of solid electrolyte, but from the viewpoint of exhibiting plasticity, it may also contain materials different from the solid electrolyte, such as binders. When the solid electrolyte layer contains materials different from the solid electrolyte, the content of solid electrolyte may, for example, be 99.8% by mass or less, or 99.6% by mass or less.

[0122] As a binder that can be contained in the solid electrolyte layer, examples include the same binders that can be contained in the negative electrode active material layer.

[0123] When the solid electrolyte layer contains a binder, the binder content is not particularly limited. When the total mass of the solid electrolyte layer is 100% by mass, it can be 0.2% by mass or more, or 0.4% by mass or more. On the other hand, in order to easily achieve high output, from the viewpoint of preventing excessive aggregation of the solid electrolyte and forming a solid electrolyte layer with uniformly dispersed solid electrolyte, the binder content contained in the solid electrolyte layer is preferably 5% by mass or less.

[0124] The solid-state battery disclosed herein may have an external casing as needed.

[0125] There are no particular restrictions on the material of the outer casing as long as it is stable for the electrolyte; examples include polypropylene, polyethylene, and acrylic resins.

[0126] Furthermore, the solid-state battery disclosed herein can be either a primary battery or a secondary battery. Secondary batteries can be repeatedly charged and discharged, and are useful, for example, as automotive batteries. Additionally, the solid-state battery disclosed herein can be a solid-state lithium secondary battery.

[0127] The shape of the solid-state battery disclosed herein is not particularly limited, and examples include coin-shaped, laminated, cylindrical, and square types.

[0128] 2. Manufacturing methods for solid-state batteries

[0129] The method for manufacturing the solid-state battery disclosed above is not particularly limited. For example, the following method can be cited, which includes:

[0130] The process of forming a solid electrolyte layer with two flat sides;

[0131] The process of forming a negative electrode layer on one side of the solid electrolyte layer; and

[0132] The process of forming a positive electrode layer on the other side of the solid electrolyte layer.

[0133] The negative electrode layer further contains an interface forming agent, which contains at least one selected from metallic elements and metalloid elements. The metallic elements and metalloid elements can be converted into cations that conduct the solid electrolyte in the solid electrolyte layer. These cations do not participate in the electrode reaction and have a lower ionic conductivity than the ions that participate in the electrode reaction. The ionic radius of the cation is [missing information]. the following,

[0134] The manufacturing method further includes the following steps:

[0135] Within a voltage range where neither the decomposition of the positive electrode active material nor the metal deposition on the negative electrode active material occurs, a charge-discharge cycle of at least one cycle is performed on a laminate having the negative electrode layer, the solid electrolyte layer, and the positive electrode layer sequentially, at a current value of less than 0.364 mAh, thereby making at least one interface of the interface between the solid electrolyte layer and the positive electrode layer and the interface between the solid electrolyte layer and the negative electrode layer a dendritic structure.

[0136] As a method for forming a solid electrolyte layer with two flat sides, as well as a negative electrode layer and a positive electrode layer, conventionally known methods can be used, and there is no particular limitation. For example, methods that form the layers by pressing powdered materials constituting each layer into shape, and methods that disperse the materials constituting each layer in a solvent to make a slurry, coat the slurry onto a support, and dry it are examples.

[0137] Furthermore, a flat solid electrolyte layer simply means a solid electrolyte layer without a dendritic structure on its surface; it can have micro-undulations on its surface that differ from a dendritic structure. For example, when observing a cross-section obtained by cutting a solid electrolyte layer along its thickness direction at 1000x magnification, if no dendritic structure can be identified at the interface of the solid electrolyte layer, then the interface is flat.

[0138] The negative electrode layer formed on one side of the solid electrolyte layer is preferably formed in a manner where a layer containing a surfactant is in contact with the solid electrolyte layer. Similarly, the positive electrode layer formed on the other side of the solid electrolyte layer is preferably formed in a manner where a layer containing a positive electrode active material is in contact with the solid electrolyte layer. Therefore, when the negative electrode layer includes a negative electrode active material layer and a negative electrode current collector, it is preferable to form the negative electrode layer on one side of the solid electrolyte layer in a manner where the negative electrode active material layer is in contact with the solid electrolyte layer. Conversely, when the positive electrode layer includes a positive electrode active material layer and a positive electrode current collector, it is preferable to form the positive electrode layer on the other side of the solid electrolyte layer in a manner where the positive electrode active material layer is in contact with the solid electrolyte layer.

[0139] When the negative electrode layer includes a negative electrode active material layer and a negative electrode current collector, or when the positive electrode layer includes a positive electrode active material layer and a positive electrode current collector, a structure in which the active material layer is formed on the current collector can be prefabricated. By using such a structure, for example, a laminate having a negative electrode layer, a solid electrolyte layer with flat surfaces on both sides, and a positive electrode layer in sequence can be obtained by the following method.

[0140] First, a positive electrode structure with a positive active material layer formed on a positive current collector and a negative electrode structure with a negative active material layer formed on a negative current collector are fabricated, and a solid electrolyte layer is formed on a support. Next, the positive electrode structure is laminated onto the solid electrolyte layer formed on the support, with the solid electrolyte layer in contact with the positive active material layer. Then, the solid electrolyte layer is transferred onto the positive active material layer by peeling off the support from the solid electrolyte layer. Next, the negative electrode structure is laminated onto the solid electrolyte layer, with the exposed solid electrolyte layer in contact with the negative active material layer. Thus, a laminate having a negative current collector, a negative active material layer, a two-sided flat solid electrolyte layer, a positive active material layer, and a positive current collector in sequence can be fabricated.

[0141] Within a voltage range where neither the decomposition of the positive electrode active material nor the metal deposition on the negative electrode active material occurs, the above-mentioned laminate is subjected to one or more charge-discharge cycles at a current value of less than 0.364 mAh, thereby making at least one of the interfaces between the solid electrolyte layer and the positive electrode layer and between the solid electrolyte layer and the negative electrode layer a dendritic structure.

[0142] The effect of subjecting the above-mentioned laminate to low-rate charging and discharging at a current value of 0.364 mAh or less, so that at least one of the interfaces between the solid electrolyte layer and the positive electrode layer and the solid electrolyte layer and the negative electrode layer becomes an interface with a dendritic structure, is as described above.

[0143] The voltage range within which neither the decomposition of the positive electrode active material nor the metal deposition on the negative electrode active material occurs during the aforementioned low-rate charge-discharge can be appropriately adjusted according to the types of positive and negative electrode active materials, and is not particularly limited; for example, it can be in the range of 2 to 5V. A current value of 0.364mAh or less is acceptable, but from the viewpoint of easily forming a dendritic interface with a high anchoring effect, 0.300mAh or more is preferred.

[0144] In addition, it is sufficient to perform the low-rate charge and discharge cycle once or more, but from the viewpoint that it is easy to form a dendritic interface with a high anchoring effect, it is preferable to perform 2 to 5 cycles, and more preferably 2 to 3 cycles.

[0145] [Example]

[0146] [Example 1]

[0147] (1) Fabrication of the positive electrode structure

[0148] LiNi alloys coated with LiNbO3 using a rolling fluid granulation coating device were used as positive electrode active materials. 1 / 3 Co 1 / 3Mn 1 / 3 O2 (average particle size 10 μm), 10LiI·15LiBr·75 (0.75Li2S·0.25P2S5) (mol%, average particle size 0.5 μm) as a sulfide solid electrolyte, VGCF-H as a conductive material, and PVDF as a binder were weighed in a weight ratio of positive electrode active material: sulfide solid electrolyte: conductive material: binder = 85.4:12.7:1.3:0.6 and mixed with a dispersion medium (diisobutyl ketone). The mixture was dispersed using an ultrasonic homogenizer (model: UH-50, manufactured by SMT Co., Ltd.) to obtain a positive electrode slurry. The obtained positive electrode slurry was coated onto an Al foil (15 μm thick) as the positive electrode current collector using a doctor blade coating method, dried at 100°C for 30 minutes, and a layer of positive electrode active material was stacked on the positive electrode current collector and cut into 1 cm pieces. 2 The size is determined, thus obtaining a positive electrode structure with a positive active material layer and a positive current collector.

[0149] (2) Fabrication of the negative electrode structure

[0150] Si particles (average particle size 0.8 μm) as the negative electrode active material, 10LiI·15LiBr·75 (0.75Li2S·0.25P2S5) (mol%, average particle size 0.5 μm) as the sulfide solid electrolyte, VGCF-H as the conductive material, SBR as the binder, and VCAS-140 (product name, manufactured by Vitro Minerals, average particle size (D50) 12 μm) as the interface forming agent were weighed in the following weight ratios: negative electrode active material: sulfide solid electrolyte: conductive material: binder: VCAS-140 = 46.8: 44.4: 6.5: 1.4: 0.5, and mixed with a dispersion medium (diisobutyl ketone). The resulting mixture was dispersed using a thin-film cyclone high-speed mixer (Filmix 30-L type, manufactured by Primix Co., Ltd.) to obtain a negative electrode slurry. The obtained negative electrode slurry was coated onto a Ni foil (22 μm thick) serving as the negative electrode current collector using a doctor blade coating method. The foil was dried at 100°C for 30 minutes. A layer of negative electrode active material was then stacked on the negative electrode current collector and cut into 1 cm pieces. 2The size of the anode material layer and the anode current collector are thus obtained. Furthermore, the gap (gap) of the applicator during anode slurry coating, with a positive electrode active material capacity of 207 mAh / g and a negative electrode active material capacity of 3579 mAh / g, is [value missing] per 1 cm. 2 The weight of the negative electrode active material was adjusted to a ratio of positive electrode capacity to negative electrode capacity of 3.

[0151] (3) Fabrication of solid electrolyte layer

[0152] 10LiI·15LiBr·75 (0.75Li2S·0.25P2S5 (mol%, average particle size 2.0 μm)) as the sulfide solid electrolyte and SBR as the binder were weighed at a weight ratio of 99.6:0.4 and mixed with a dispersion medium (diisobutyl ketone). The mixture was dispersed using an ultrasonic homogenizer (model: UH-50, manufactured by SMT Co., Ltd.) to obtain a solid electrolyte slurry. The obtained solid electrolyte slurry was coated onto an Al foil (15 μm thick) using a doctor blade coating method with a coater, dried at 100°C for 30 minutes, and a solid electrolyte layer was stacked on the Al foil and cut into 1 cm pieces. 2 The size of the layer determines the solid electrolyte layer with Al foil.

[0153] (4) Solid-state battery manufacturing

[0154] The solid electrolyte layer with Al foil is placed opposite the positive electrode structure, and the solid electrolyte layer and the positive electrode active material layer are overlapped. The layers are then pressed using a roller pressing method at a linear pressure of 1.6 t / cm. The Al foil is then peeled off from the solid electrolyte layer, thereby transferring the solid electrolyte layer onto the positive electrode active material layer. The solid electrolyte layer transferred to the positive electrode active material layer is then placed opposite the negative electrode structure, and the solid electrolyte layer and the negative electrode active material layer are overlapped. The layers are then pressed using a uniaxial press at a linear pressure of 5.0 t / cm. 2 The surface pressure is then applied. Next, current collector tabs are placed on the positive and negative current collectors and laminated for sealing. Then, as a low-rate charge-discharge process, the battery is charged at a constant current of 0.364 mAh in a 25°C constant-temperature bath until 4.05 V is reached, followed by constant-voltage charging at 4.05 V until the current reaches 0.036 mAh, and then discharged at a constant current of 0.364 mAh until 2.5 V is reached, followed by constant-voltage discharge at 2.5 V until the current reaches 0.036 mAh. This process is repeated three times to obtain the solid-state battery of Example 1.

[0155] [Example 2]

[0156] In Example 1, in the above "(2) Fabrication of negative electrode structure", each material was weighed in the following manner: negative electrode active material: sulfide solid electrolyte: conductive material: binder: VCAS-140 = 45.9: 43.5: 6.4: 1.4: 2.3 by weight ratio. Otherwise, the solid battery of Example 2 was obtained in the same manner as in Example 1.

[0157] [Comparative Example 1]

[0158] In Example 1, VCAS-140 was not added in “(2) Fabrication of negative electrode structure”. The materials were weighed in the following manner: negative electrode active material: sulfide solid electrolyte: conductive material: binder = 47.0: 44.6: 6.6: 1.4 by weight. Otherwise, the solid battery of Comparative Example 1 was obtained in the same manner as in Example 1.

[0159] [Cross-section observation]

[0160] The cross-sections of the solid-state batteries fabricated in each embodiment and comparative example along the stacking direction were observed using SEM at a magnification of 1000x.

[0161] As a result, in the cross-section of the solid-state battery fabricated in each embodiment, such as Figure 1 As shown, the interfaces between the solid electrolyte layer and the negative electrode layer, as well as the interfaces between the solid electrolyte layer and the positive electrode layer, both exhibit a dendritic structure throughout the entire interface. More specifically, in the cross-section of the solid-state battery fabricated in Example 1, at the interface between the solid electrolyte layer and the negative electrode layer, the number of main stems extending from the solid electrolyte layer within a 100 μm region is 12–19, and at the interface between the solid electrolyte layer and the positive electrode layer, the number of main stems extending from the solid electrolyte layer within a 100 μm region is 7–17. In the cross-section of the solid-state battery fabricated in Example 2, at the interface between the solid electrolyte layer and the negative electrode layer, the number of main stems extending from the solid electrolyte layer within a 100 μm region is 17–21, and at the interface between the solid electrolyte layer and the positive electrode layer, the number of main stems extending from the solid electrolyte layer within a 100 μm region is 10–22.

[0162] On the other hand, in the cross-section of the solid battery fabricated in Comparative Example 1, the interface of the solid electrolyte layer is flat.

[0163] [Ca element mapping]

[0164] Ca elemental mapping analysis was performed on the cross-sections of the solid-state batteries fabricated in each embodiment. The results confirmed the presence of Ca in the solid electrolyte layer, at least at the interface on the negative electrode layer side, where Ca is distributed in a dendritic pattern. This indicates that Ca in the surfactant contained in the negative electrode active material layer is conducted to the solid electrolyte layer and further moves at the interface of the solid electrolyte layer in a dendritic structure.

[0165] As a specific example of Ca element mapping analysis image Figure 2 This image shows the Ca element mapping analysis at the cross-section of the solid-state battery fabricated in Example 2. Figure 2 In the image shown, the portion where Ca was detected is represented in gray. Furthermore, the Ca detection limit was set in a manner where the difference between the amount of Ca in the solid electrolyte layer and the amount of Ca in the negative electrode active material layer becomes definite, and the image was taken in a field of view where the interfacial forming agent in the negative electrode active material layer is not reflected. Therefore, in... Figure 2 In the image shown, it appears that almost no Ca is detected in the negative electrode active material layer, but Ca is actually present in the negative electrode active material layer.

[0166] [Charge / Discharge Evaluation]

[0167] The solid-state batteries fabricated in each embodiment and comparative example were charged at a constant current of 3.64 mAh in a 60°C constant-temperature bath until 4.05 V was reached, then charged at a constant voltage of 4.05 V until the current reached 1.21 mAh, discharged at a constant current of 3.64 mAh until 2.5 V was reached, and then discharged at a constant voltage of 2.5 V until the current reached 1.21 mAh was reached. This operation was repeated 50 times.

[0168] The discharge capacity during the first cycle is taken as the initial discharge capacity, and the discharge capacity of each subsequent cycle is taken as the discharge capacity after the cycle test. The capacity retention rate is calculated using the following formula.

[0169] Capacity retention (%) = (Discharge capacity after cycle test ÷ Initial discharge capacity) × 100

[0170] The capacity retention rates of the solid-state batteries fabricated in each embodiment and comparative example are shown in the figure. Figure 3 .

[0171] [Evaluation Results]

[0172] The solid-state battery in Comparative Example 1 is a solid-state battery manufactured without surfactants in the negative electrode layer. Therefore, it does not have dendritic structures at the interfaces between the solid electrolyte layer and the negative electrode layer, nor at the interfaces between the solid electrolyte layer and the positive electrode layer. Figure 3As shown, in the charge-discharge evaluation, the capacity retention rate of the solid-state battery in Comparative Example 1 began to decline sharply after 15 cycles. At 30 cycles, the capacity retention rate dropped to approximately 50%, and continued to decline thereafter, reaching approximately 40% at 50 cycles. It is believed that in the solid-state battery of Comparative Example 1, delamination occurred at the interface of the solid electrolyte layer around the 15th cycle, thus resulting in the capacity retention rate decline described above.

[0173] On the other hand, the solid-state batteries obtained in Examples 1 and 2 are solid-state batteries manufactured by stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer with an interface forming agent in the negative electrode layer and then charging and discharging at a low rate. Therefore, the interfaces between the solid electrolyte layer and the positive electrode layer, and between the solid electrolyte layer and the negative electrode layer, both have dendritic structures. Figure 3 As shown, the solid-state batteries of Examples 1 and 2 maintained a capacity retention of approximately 70% even after 50 cycles in the charge-discharge evaluation, suppressing the decline in capacity retention. Furthermore, no interfacial delamination of the solid electrolyte layer occurred in the solid-state batteries of Examples 1 and 2 after 50 cycles.

Claims

1. A solid-state battery, comprising: a negative electrode layer containing a negative electrode active material, a positive electrode layer containing a positive electrode active material, and a solid electrolyte layer located between the negative electrode layer and the positive electrode layer and containing a solid electrolyte. The solid electrolyte layer contains a sulfide-based solid electrolyte. The negative electrode layer also contains an interface forming agent, which is an amorphous glassy calcium aluminosilicate. The interface forming agent contains at least one element selected from metallic and metalloid elements. These metallic and metalloid elements can be converted into cations that conduct the solid electrolyte in the solid electrolyte layer. These cations do not participate in the electrode reaction and have a lower ionic conductivity than the ions that participate in the electrode reaction. The ionic radius of the cations is less than 1.34 Å. The solid electrolyte layer has a dendritic structure at at least one of its interfaces with the positive electrode layer and with the negative electrode layer.

2. The solid-state battery according to claim 1, wherein the interface forming agent contains at least one selected from Ca, Al, Mg, Na and B as the metallic element or the metalloid element.

3. The solid-state battery according to claim 1 or 2, wherein the amorphous glassy calcium aluminosilicate used as the interface forming agent contains CaO and Al2O3.

4. In the solid-state battery according to claim 1 or 2, the content of the interface forming agent is more than 1 part by mass and less than 5 parts by mass relative to 100 parts by mass of the negative electrode active material.

5. The solid-state battery according to claim 1 or 2, wherein the negative electrode layer contains an active material with Si or Sn as the constituent element as the negative electrode active material.

6. A method for manufacturing a solid-state battery, the solid-state battery comprising: a negative electrode layer containing a negative electrode active material, a positive electrode layer containing a positive electrode active material, and a solid electrolyte layer located between the negative electrode layer and the positive electrode layer and containing a solid electrolyte, the manufacturing method comprising: The process of forming a solid electrolyte layer with two flat sides; The process of forming the negative electrode layer on one side of the solid electrolyte layer; and The process of forming the positive electrode layer on the other side of the solid electrolyte layer. The solid electrolyte layer contains a sulfide-based solid electrolyte. The negative electrode layer also contains an interface forming agent, which is an amorphous glassy calcium aluminosilicate. The interface forming agent contains at least one element selected from metallic and metalloid elements. These metallic and metalloid elements can be converted into cations that conduct the solid electrolyte in the solid electrolyte layer. These cations do not participate in the electrode reaction and have a lower ionic conductivity than the ions that participate in the electrode reaction. The ionic radius of the cations is less than 1.34 Å. The manufacturing method further includes the following steps: Within a voltage range where neither the decomposition of the positive electrode active material nor the metal deposition on the negative electrode active material occurs, a charge-discharge cycle is performed on a laminate having the negative electrode layer, the solid electrolyte layer, and the positive electrode layer sequentially at a current value of less than 0.364 mAh for one or more cycles, thereby making at least one of the interfaces between the solid electrolyte layer and the positive electrode layer and between the solid electrolyte layer and the negative electrode layer a dendritic structure.

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