All-solid-state battery and method for manufacturing the same

Abstract

The purpose of this disclosure is to provide an all-solid-state battery with good cycle characteristics. This purpose is achieved by an all-solid-state battery characterized in that it has: a positive electrode including a positive electrode layer, a negative electrode including a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein at least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer includes a particulate first binder and a non-particulate second binder.

Description

Technical Field

[0001] This disclosure relates to an all-solid-state battery and a method for manufacturing the same. Background Technology

[0002] With the rapid proliferation of information-related and communication devices such as computers, cameras, and mobile phones in recent years, the development of batteries, which are used as their power source, has gained attention. Furthermore, in the automotive industry and elsewhere, the development of high-output, high-capacity batteries for electric vehicles or hybrid vehicles is also underway.

[0003] Among all-solid-state batteries, all-solid-state lithium-ion batteries have attracted attention for the following aspects: utilizing battery reactions accompanied by lithium-ion movement, thus resulting in high energy density; in addition, using a solid electrolyte instead of an electrolyte containing organic solvents as the electrolyte sandwiched between the positive and negative electrodes.

[0004] Patent Document 1 describes a binder containing a polymer with an average particle size of 0.1 μm to 1 μm as a constituent material of a solid electrolyte layer.

[0005] Patent document 2 states that the coefficient of thermal expansion of the polymer adhesive is greater than the coefficient of thermal expansion of the peripheral components disposed around the periphery of the all-solid-state battery.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2016 / 152262

[0009] Patent Document 2: Japanese Patent Application Publication No. 2016-081635 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] Patent Document 1 describes how using a polymer with a specific particle size as a binder can increase the number of contact points and the contact area between solid electrolyte particles, thus producing an all-solid-state secondary battery with low internal resistance. Furthermore, Patent Document 1 also describes how reducing internal resistance can suppress the degradation of active materials and binders, thereby improving the cycle characteristics of the all-solid-state battery.

[0012] However, according to the research of the inventors, if the particulate polymer described in Patent Document 1 is used as an adhesive, although the ionic conductivity is improved and the internal resistance is reduced, the cycling characteristics are not improved to the expected level.

[0013] In view of the above-mentioned circumstances, the purpose of this disclosure is to provide an all-solid-state battery with good cycle characteristics and a method for manufacturing the same.

[0014] Technical solution

[0015] This disclosure provides an all-solid-state battery, characterized by having:

[0016] A positive electrode comprising a positive electrode layer, a negative electrode comprising a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer.

[0017] Wherein, at least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises a particle-like first binder and a non-particle-like second binder.

[0018] This disclosure provides a method for manufacturing an all-solid-state battery, characterized in that the method comprises manufacturing an all-solid-state battery having a positive electrode including a positive electrode layer, a negative electrode including a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The method for manufacturing the all-solid-state battery includes the following steps:

[0019] A process of preparing at least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, using at least a dispersion of the first binder and a solution of the second binder.

[0020] Invention Effects

[0021] This disclosure provides an all-solid-state battery with good cycle characteristics. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating an example of the state of active material particles when a non-particulate second binder is used.

[0023] Figure 2 This is a schematic diagram illustrating an example of the state of active material particles when a particulate first binder is used.

[0024] Figure 3 This is a schematic cross-sectional view illustrating an example of the all-solid-state battery of this disclosure. Detailed Implementation

[0025] 1. All-solid-state battery

[0026] This disclosure provides an all-solid-state battery, characterized by having:

[0027] A positive electrode comprising a positive electrode layer, a negative electrode comprising a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer.

[0028] Wherein, at least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises a particle-like first binder and a non-particle-like second binder.

[0029] Conventional all-solid-state batteries have used solvent-based binders that are completely dissolved in organic solvents during battery manufacturing. However, in all-solid-state batteries using these conventional binders, the polymer used as the binder is positioned at the interface between the solid electrolyte and the active material in order to evenly cover the surfaces of both. As a result, the binder hinders ionic conductivity, leading to increased resistance and reduced cycle performance in the all-solid-state battery.

[0030] Figure 1 This is a schematic diagram illustrating an example of the state of active material particles when a non-particulate second binder is used. It should be noted that, for ease of illustration and understanding, the scale and aspect ratios in the accompanying drawings have been appropriately altered and exaggerated based on these actual objects.

[0031] like Figure 1 As shown, the non-particle-like second binder 2 covers the active material particles 1 to the same extent as the slanted portion, thereby hindering the ionic conductivity between the active material and the solid electrolyte, making the all-solid-state battery high-resistance.

[0032] The researchers found that, as a binder for all-solid-state batteries, using a specified amount of a particulate first binder (dispersion-type binder) dispersed in a solvent (which should be noted as a dispersion medium, but referred to as solvent in this specification for ease of explanation) and a specified amount of a non-particulate second binder (solution-type binder) together results in good cycle characteristics for all-solid-state batteries.

[0033] It can be argued that this is because by using a combination of a particulate first adhesive and a non-particulate second adhesive, it becomes easier to form point bonds with active material particles, solid electrolyte particles, etc. Figure 2 This is a schematic diagram illustrating an example of the state of active material particles when a particulate first binder is used. (Example) Figure 2As shown, the particulate first binder readily covers the surfaces of the solid electrolyte particles and the active material particles partially rather than entirely. Therefore, at the interface between the solid electrolyte particles and the active material particles, an area is created where the un-binder-covered portions of their surfaces come into contact. Through this area, the ionic conductivity between the solid electrolyte particles and the active material particles is increased, thus making the all-solid-state battery low-resistance. Therefore, it can be considered that an all-solid-state battery can be manufactured that balances improved adhesion between the solid electrolyte particles and the active material particles with improved cycle performance.

[0034] On the other hand, if only a particulate first binder is used, the active material particles, solid electrolyte particles, etc., are not easily dispersed uniformly in the slurry used for layer formation, and the distribution of active material particles, solid electrolyte particles, etc., in the formed layer easily becomes uneven. Furthermore, it can be considered that if the distribution of active material particles, solid electrolyte particles, etc., in the layer is uneven, regions with excessive ionic conductivity and regions with poor ionic conductivity will be formed in the all-solid-state battery. As a result, the balance of the all-solid-state battery is disrupted, and the cycle characteristics are easily reduced. In contrast, it can be considered that by using a second binder dissolved during layer formation, the first binder can be more easily dispersed more uniformly in the slurry, resulting in a more uniform distribution of the first binder in the formed layer, thus enabling the all-solid-state battery to have good cycle characteristics.

[0035] It should be noted that, when only a non-particulate second binder (solubilizing binder) is used, reducing the amount of binder can also prevent the active material particles and solid electrolyte particles from being covered by the binder to an equal degree, thereby improving the ionic conductivity between the solid electrolyte particles and the active material particles. However, according to the present inventors, while using only a small amount of non-particulate second binder does improve the ionic conductivity of the all-solid-state battery, the cycle characteristics do not improve to the desired level. This can be attributed to the fact that, if only a small amount of second binder is used, the binder component tends to be more concentrated on the surface of the electrodes, separator layers, or near the current collector in the positive electrode layer, negative electrode layer, and solid electrolyte layer. Furthermore, this can also be attributed to the fact that, in order to improve the adhesion between the active material particles and the solid electrolyte particles, a certain amount of second binder must be used, thus the second binder blocks the pores of the active material on the electrode surface, increasing the resistance near the current collector. Based on these main reasons, it can be argued that even if the surfaces of the active material particles and solid electrolyte particles are covered to varying degrees, the balance of the all-solid-state battery will be disrupted and the cycle characteristics will be reduced when only a second adhesive is used in an amount sufficient to ensure the adhesion between the active material particles and the solid electrolyte particles.

[0036] Thus, by using both a particulate first binder and a non-particulate second binder, the first binder improves the adhesion between the solid electrolyte particles and the active material particles, and also enhances the ionic conductivity between them, resulting in good cycle characteristics of the all-solid-state battery. Furthermore, the second binder makes the distribution of active material particles, solid electrolyte particles, etc., in the layer more uniform, maintaining the balance of the all-solid-state battery and suppressing a decrease in cycle characteristics. It can be further considered that it can also suppress the presence of bias in the second binder, thereby further improving cycle characteristics.

[0037] [Adhesive]

[0038] Examples of adhesives include particulate first adhesives (dispersion adhesives) and non-particulate second adhesives (solution adhesives) that form layers by dissolving resin in a solvent.

[0039] In this disclosure, at least one particulate first binder (dispersible binder) and a non-particulate second binder (solvent binder) are included in the same layer. During layer formation, the stability of the slurry for layer formation is improved by using a solvent binder in addition to the dispersible binder, resulting in improved layer uniformity.

[0040] The adhesive may be included in at least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer and the solid electrolyte layer described below, preferably in the positive electrode layer and the negative electrode layer, and more preferably in the positive electrode layer, the negative electrode layer and the solid electrolyte layer.

[0041] In addition to the solid electrolyte, the positive and negative electrode layers also contain active materials, conductive materials, and other additives. Therefore, ensuring good contact between the active materials and the solid electrolyte is crucial from the perspective of ensuring the ion conductivity path in the positive and negative electrode layers.

[0042] When only a solvent-based binder is used, the binder covers the interface between the active material particles and the solid electrolyte particles to an equal extent. Therefore, the binder hinders ionic conductivity, resulting in higher resistance in the all-solid-state battery and deterioration of battery characteristics.

[0043] On the other hand, by using particulate dispersion binders and non-particulate dissolution binders, the interface between active material particles and solid electrolyte particles can be easily covered partially rather than entirely, thus ensuring the desired ionic conductivity path, reducing the resistance of the all-solid-state battery, and improving battery characteristics.

[0044] Furthermore, since active materials are present in both the positive and negative electrode layers, when comparing the expansion and contraction of these active materials during the charge and discharge of the all-solid-state battery with the same addition amount, the dispersion binder results in better cycle characteristics for the all-solid-state battery. This can be attributed to the low resistance at the interface between the active material particles and the solid electrolyte particles, and the increased adhesion between them. After expansion and contraction, the active material easily maintains the same structural integrity as before the expansion and contraction. It should be noted that in this disclosure, the improved cycle characteristics are demonstrated regardless of the type of active material.

[0045] The content of the particulate first binder in each of the positive electrode layer, negative electrode layer, and solid electrolyte layer is not particularly limited. From the viewpoint of improving the adhesion effect of the particulate first binder and thus improving cycle characteristics, when the total mass of the layers is set to 100% by mass, the content in the layers can be at least 0.01% by mass, particularly at least 0.1% by mass, particularly at least 0.2% by mass, further at least 1.0% by mass, and even further at least 3.0% by mass. Furthermore, from the viewpoint of improving the resistance reduction effect of the all-solid-state battery, the content can be at least 10.0% by mass, particularly at least 8.0% by mass, particularly at least 7.0% by mass, and further at least 5.0% by mass. From the viewpoint of achieving a balance, it is sufficient to determine an appropriate content of the particulate first binder. For example, the content of the particulate first adhesive in the layer can be set to 0.01% or more and 10.0% or less when the total mass of the layer is set to 100% by mass, preferably 0.1% or more and 8.0% or less by mass, more preferably 0.2% or more and 7.0% or less by mass, further preferably 1.0% or more and 7.0% or less by mass, and particularly preferably 3.0% or more and 5.0% or less by mass.

[0046] The particulate first adhesive is not particularly limited and can be at least one resin selected from the group consisting of fluorinated resins, polyolefin resins, and (meth)acrylic resins. By using at least one resin selected from fluorinated resins, polyolefin resins, and (meth)acrylic resins, the voltage resistance of the adhesive can be ensured, and good adhesion is guaranteed. It should be noted that (meth)acrylic acid refers to acrylic acid or methacrylic acid. From the viewpoint of further improving the oxidation resistance of the resin in the positive electrode layer, fluorinated resins and polyolefin resins are preferred, and fluorinated resins are more preferred. Furthermore, from the viewpoint of improving the adhesion of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer, it is preferable that each layer of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains the same type of resin as the first adhesive. Specifically, it is preferable that each layer of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains a fluorinated resin as the first adhesive, or that all layers contain a polyolefin resin as the first adhesive, and more preferably, that all layers contain a fluorinated resin as the first adhesive.

[0047] Fluorine-based resins include: polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), perfluoroalkoxyalkane (PFA), etc.

[0048] Examples of polyolefin resins include: styrene-butadiene rubber (SBR), polypropylene (PP), and polyethylene (PE).

[0049] Examples of (meth)acrylic resins include: polymethyl methacrylate (PMMA), polymethyl acrylate, polybutyl acrylate (PBA), and polyacrylonitrile (PAN).

[0050] The average particle size of the particulate first binder in each of the positive electrode layer, negative electrode layer, and solid electrolyte layer is not particularly limited, but the lower limit can be 0.01 μm or more, particularly 0.03 μm or more, further 0.1 μm or more, even more 0.5 μm or more, and even more 1.2 μm or more, and the upper limit can be 170.0 μm or less, particularly 130.0 μm or less, further 80.0 μm or less, and even more 60.00 μm or less. For example, the average particle size of the particulate first binder can be set to 0.01 μm or more and 170.0 μm or less, preferably 0.03 μm or more and 120.0 μm or less, more preferably 0.1 μm or more and 130.0 μm or less, even more preferably 0.1 μm or more and 80.0 μm or less, particularly preferably 0.5 μm or more and 60.0 μm or less, and particularly preferably 1.2 μm or more and 60.0 μm or less.

[0051] By further increasing the particle size of the first particulate binder, it is easier to partially cover the surfaces of the active material particles and solid electrolyte particles, thereby further reducing the resistance of the all-solid-state battery. On the other hand, by reducing the particle size, the number of adhesion points between the particulate first binder and the surfaces of the active material particles and solid electrolyte particles can be increased, improving the adhesion between the active material particles and solid electrolyte particles, making it easier to maintain the structure of the all-solid-state battery and improving cycle characteristics. From the viewpoint of achieving a balance between these two aspects, it is sufficient to determine an appropriate particle size for the first particulate binder.

[0052] The first adhesive in particulate form exists in the layer in particulate form, but it can also be used when the layer is formed, either by dispersing the first adhesive in a solvent or by using an adhesive that has polymerized into particulate form in a solvent.

[0053] As a solvent used to disperse the particulate first binder, there is no particular limitation as long as it is a solvent that can stably disperse the particulate first binder. Examples include toluene and methyl ethyl ketone (MEK), or a mixture thereof.

[0054] The shape of the second binder (solution-type binder) present in each of the positive electrode layer, negative electrode layer and solid electrolyte layer is not particularly limited as long as it is non-particulate.

[0055] In this disclosure, "non-particle" means not being particles. Specifically, it means that even when observed at tens of thousands of times magnification using SEM (scanning electron microscopy) or TEM (transmission electron microscopy), no particle state can be identified. Typically, the second adhesive can be considered as a film that partially covers the surface of the active material particles or solid electrolyte particles.

[0056] It should be noted that, in this disclosure, if the shape of the second adhesive present in the formed layer is non-particulate, the shape of the material of the second adhesive used in the formation of the layer before it is dissolved in the solvent can also be particulate.

[0057] Resins used as non-particulate second adhesives (solubilizing adhesives) include: epoxy resins, (meth)acrylic resins, polyolefin resins, silicone resins, alkylated derivatives of cellulose, and polyoxyethylene resins. Specific resins, considering high solubility in organic solvents, include ethyl cellulose (EC) and polyethylene oxide (PEO). It should be noted that a material used as a particulate first adhesive can also be used, and a non-particulate second adhesive can be prepared by dissolving the material in a solvent capable of dissolving it.

[0058] The solvent for dissolving resin can be appropriately selected according to the type of resin. For example, when the resin is ethyl cellulose (EC), solvents such as N-methylpyrrolidone (NMP), toluene, and methyl ethyl ketone (MEK) can be used. Furthermore, when the resin is PVDF, solvents such as N-methylpyrrolidone (NMP) can be used.

[0059] The content of the non-particulate second binder in each of the positive electrode layer, negative electrode layer, and solid electrolyte layer is not particularly limited. When the total mass of the layers is set to 100% by mass, the binder may contain more than 0% by mass and less than 1.0% by mass, or more than 0% by mass and less than 0.7% by mass. Increasing the content of the second binder improves the dispersibility of particles such as active material particles and solid electrolyte particles present in the layers. Reducing the content of the second binder suppresses the high resistance of the all-solid-state battery caused by excessive coverage of the surface of active material particles and solid electrolyte particles by the second binder. From the viewpoint of achieving a balance, it is sufficient to determine an appropriate content of the non-particulate second binder.

[0060] [All-solid-state battery]

[0061] Figure 3 This is a schematic cross-sectional view illustrating an example of the all-solid-state battery of this disclosure.

[0062] like Figure 3 As shown, the all-solid-state battery 100 includes: a positive electrode 16, comprising a positive electrode layer 12 and a positive electrode current collector 14; a negative electrode 17, comprising a negative electrode layer 13 and a negative electrode current collector 15; and a solid electrolyte layer 11 disposed between the positive electrode 16 and the negative electrode 17.

[0063] [positive electrode]

[0064] The positive electrode has at least a positive electrode layer and, if necessary, a positive electrode current collector.

[0065] The positive electrode layer contains positive electrode active material, and may also contain solid electrolyte, conductive material and binder as any component.

[0066] There are no particular restrictions on the types of positive electrode active materials; for example, the general formula Li can be listed. x M y O z(M is a transition metal element, x = 0.02–2.2, y = 1–2, z = 1.4–4) represents the positive electrode active material. In the above general formula, M can be at least one selected from the group consisting of Co, Mn, Ni, V, Fe, and Si, or at least one selected from the group consisting of Co, Ni, and Mn. Specifically, examples of such positive electrode active materials include: LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMn2O4, Li(Ni) 0.5 Mn 1.5 O4, Li2FeSiO4, Li2MnSiO4, etc.

[0067] Furthermore, as the above general formula Li x M y O z Other positive electrode active materials include: lithium titanate (e.g., Li4Ti5O) 12 Lithium metal phosphate (LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4), transition metal oxides (V2O5, MoO3), TiS2, LiCoN, Si, SiO2, Li2SiO3, Li4SiO4, and lithium storage intermetallic compounds (e.g., Mg2Sn, Mg2Ge, Mg2Sb, Cu3Sb).

[0068] There are no particular limitations on the shape of the positive electrode active material. For example, it can be in the form of particles or thin films. From the point of view of good operability, it can also be in the form of particles.

[0069] When the positive electrode active material is a particle, the average particle size (D50) of the particle is preferably 1 nm or more and 100 μm or less, more preferably 10 nm or more and 30 μm or less.

[0070] A coating containing Li-ion conductive oxides can also be formed on the surface of the positive electrode active material. This is because it can inhibit the reaction between the positive electrode active material and the solid electrolyte.

[0071] Examples of Li-ion-conducting oxides include, for example, LiNbO3 and Li4Ti5O. 12 Including Li3PO4, etc. The lower limit of the coating thickness can be, for example, 0.1 nm or more, or 1 nm or more. On the other hand, the upper limit of the coating thickness can be, for example, 100 nm or less, or 20 nm or less.

[0072] There is no particular limitation on the content of positive electrode active material in the positive electrode layer. For example, when the total mass of the positive electrode layer is set to 100% by mass, it can be in the range of 10% to 98.2% by mass.

[0073] The solid electrolytes used for the positive electrode layer are the same as those used for the solid electrolyte layer described later.

[0074] There is no particular limitation on the content of solid electrolyte in the positive electrode layer. For example, when the total mass of the positive electrode layer is set to 100% by mass, it can be in the range of 1% to 80% by mass.

[0075] As a conductive material, known conductive materials can be used, such as carbon materials and metal particles. Examples of carbon materials include at least one selected from the group consisting of acetylene black, furnace black, carbon black, carbon nanotubes, and carbon nanofibers. From the viewpoint of electronic conductivity, at least one selected from the group consisting of carbon nanotubes and carbon nanofibers is preferred. The carbon nanotubes and carbon nanofibers can also be VGCF (vapor-phase carbon fiber). Examples of metal particles include particles such as Ni, Cu, Fe, and SUS.

[0076] There is no particular limit to the amount of conductive material in the positive electrode layer.

[0077] As adhesives used for the positive electrode layer, examples include the aforementioned particulate first adhesive and the non-particulate second adhesive.

[0078] The thickness of the positive electrode layer is not particularly limited; for example, it can be 10–250 μm, or even 20–200 μm.

[0079] The positive electrode layer can be formed using methods that are known in the past.

[0080] For example, a slurry for a positive electrode layer is prepared by adding a positive electrode active material and a binder to a solvent and stirring. The slurry is then coated onto one side of a substrate such as a positive electrode current collector and dried to obtain a positive electrode layer.

[0081] Solvents include, for example, toluene and methyl ethyl ketone (MEK).

[0082] There is no particular limitation on the method of coating a positive electrode layer paste on one side of a substrate such as a positive current collector. Examples include: doctor blade method, metal mask printing method, electrostatic coating method, dip coating method, spraying method, roller coating method, gravure printing method, and screen printing method.

[0083] In addition, as another method for forming the positive electrode layer, the positive electrode layer can also be formed by pressing a powder containing a positive electrode active material and other components as needed into a positive electrode mixture.

[0084] As the positive electrode current collector, a known metal that can be used as a current collector in an all-solid-state battery can be used. Examples of such metals include metallic materials containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In.

[0085] There are no particular limitations on the shape of the positive current collector; it can be made into various shapes such as foil or mesh.

[0086] The overall shape of the positive electrode is not particularly limited and can also be sheet-like.

[0087] In this case, the overall thickness of the positive electrode is not particularly limited and can be determined appropriately according to the target performance.

[0088] [negative electrode]

[0089] The negative electrode has at least a negative electrode layer and, if necessary, a negative electrode current collector.

[0090] The negative electrode layer contains negative electrode active material, and may also contain solid electrolyte, conductive material and binder as any component.

[0091] As the negative electrode active material, conventionally known materials can be used, such as: elemental Li, lithium alloys, carbon, elemental Si, Si alloys, and Li₄Ti₅O. 12 (LTO), etc.

[0092] Examples of lithium alloys include: LiSn, LiSi, LiAl, LiGe, LiSb, LiP, and LiIn.

[0093] Examples of Si alloys include alloys with metals such as Li, and alloys with at least one metal selected from the group consisting of Sn, Ge, and Al.

[0094] There are no particular limitations on the shape of the negative electrode active material. For example, it can be in the form of particles or thin films. From the point of view of good operability, it can also be in the form of particles.

[0095] When the negative electrode active material is a particle, the average particle size (D50) of the particle is preferably 1 nm or more and 100 μm or less, more preferably 10 nm or more and 30 μm or less.

[0096] The conductive materials, binders, and solid electrolytes contained in the negative electrode layer can be listed as the same substances contained in the positive electrode layer.

[0097] The content of the particulate first binder and the non-particulate second binder in the negative electrode layer can be the same as that in the positive electrode layer.

[0098] There is no particular limitation on the method for forming the negative electrode layer. Examples include pressing a powder containing a negative electrode active material and other components such as conductive materials and binders as needed into a negative electrode mixture. Other examples of methods for forming the negative electrode layer include preparing a negative electrode layer slurry containing a negative electrode active material, a solvent, and other components such as conductive materials and binders as needed; coating the negative electrode layer slurry onto one side of a negative electrode current collector or a solid electrolyte layer; and drying the negative electrode layer slurry. The solvent used for the negative electrode layer slurry can be the same as the solvent used for the positive electrode layer slurry. The method for coating the negative electrode layer slurry onto one side of the negative electrode current collector or solid electrolyte layer can be the same as the method for coating the positive electrode layer slurry.

[0099] As the negative current collector, the same metal used as the aforementioned positive current collector can be used.

[0100] The shape of the negative current collector is not particularly limited and can be set to the same shape as the positive current collector mentioned above.

[0101] The overall shape of the negative electrode is not particularly limited and can also be sheet-like.

[0102] In this case, the overall thickness of the negative electrode is not particularly limited and can be determined appropriately according to the target performance.

[0103] [Solid electrolyte layer]

[0104] The solid electrolyte layer contains at least a solid electrolyte.

[0105] Solid electrolytes can be categorized into sulfide-based solid electrolytes and oxide-based solid electrolytes, among others.

[0106] Examples of sulfide-based solid electrolytes include, for example, Li₂S-P₂S₅, Li₂S-SiS₂, LiX-Li₂S-SiS₂, LiX-Li₂S-P₂S₅, LiX-Li₂O-Li₂S-P₂S₅, LiX-Li₂S-P₂O₅, LiX-Li₃PO₄-P₂S₅, and Li₃PS₄. It should be noted that the description of "Li₂S-P₂S₅" refers to a material made using a raw material composition containing Li₂S and P₂S₅, and the same applies to other descriptions. Furthermore, 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.

[0107] The molar ratio of each element in a sulfide-based solid electrolyte can be controlled by adjusting the content of each element in the raw materials. Furthermore, the molar ratio and composition of each element in a sulfide-based solid electrolyte can be determined, for example, by ICP-based luminescence analysis.

[0108] Sulfide-based solid electrolytes can be glass, crystalline materials, or crystalline glass-ceramics.

[0109] The crystalline state of sulfide-based solid electrolytes can be confirmed, for example, by powder X-ray diffraction using CuKα rays.

[0110] Glass can be obtained by amorphous treatment of a raw material composition (e.g., a mixture of Li2S and P2S5). Examples of amorphous treatment include mechanical polishing. Mechanical polishing can be dry or wet, but the latter is preferred. This is because it prevents the raw material composition from adhering to the walls of containers, etc.

[0111] Glass ceramics can be obtained, for example, by heat treating glass.

[0112] In addition, crystalline materials can be obtained, for example, by heat treatment of glass or by solid-state reaction treatment of raw material compositions.

[0113] Examples of oxide-based solid electrolytes include, for example, Li. 6.25 La3Zr2Al 0.25 O 12 Li3PO4, Li 3+x PO 4- x N x (LiPON), etc.

[0114] From the viewpoint of good operability, the shape of solid electrolytes is preferably particulate.

[0115] Furthermore, there is no particular limitation on the average particle size (D50) of the solid electrolyte particles; its lower limit can be above 0.5 μm and its upper limit can be below 2 μm.

[0116] Solid electrolytes can be used alone or in combination with two or more. Furthermore, when using two or more solid electrolytes, they can be mixed.

[0117] In this disclosure, unless otherwise specified, the average particle size is the value of the median particle size (D50) of the volume reference determined by laser diffraction / scattering particle size distribution measurement. Furthermore, in this disclosure, the median particle size (D50) refers to the diameter (volume-average diameter) at which the cumulative volume of particles, arranged sequentially from the smallest particle size, is half (50%) of the total volume.

[0118] There is no particular limitation on the proportion of solid electrolyte in the solid electrolyte layer. When the total mass of the solid electrolyte layer is set to 100% by mass, the lower limit is, for example, 50.0% by mass or more, preferably 60.0% by mass or more, and the upper limit is preferably 99.2% by mass or less.

[0119] In the solid electrolyte layer, from the viewpoint of exhibiting plasticity, an adhesive that binds the solid electrolyte particles together may be included. Examples of such adhesives include the aforementioned particulate first adhesive and non-particulate second adhesive. From the viewpoint of improving the bonding effect of the first adhesive to enhance cycle characteristics and improving the resistance reduction effect of the all-solid-state battery, when the total mass of the solid electrolyte layer is set to 100% by mass, the particulate first adhesive may contain at least 0.01% by mass, particularly 0.1% by mass, particularly 0.2% by mass, further 1.0% by mass, and even further 3.0% by mass, and may contain at most 8.0% by mass or less, particularly 7.0% by mass or less, and further 5.0% by mass or less. Specifically, the content of the particulate first binder in the solid electrolyte layer, when the total mass of the solid electrolyte layer is set to 100% by mass, can be set to 0.01% by mass or more and 10.0% by mass or less, preferably 0.1% by mass or more and 8.0% by mass or less, more preferably 0.2% by mass or more and 7.0% by mass or less, further preferably 1.0% by mass or more and 7.0% by mass or less, and particularly preferably 3.0% by mass or more and 5.0% by mass or less. Furthermore, in order to easily achieve high battery output, and from the viewpoint of preventing excessive aggregation of solid electrolyte particles and forming a solid electrolyte layer with uniformly dispersed solid electrolyte particles, the non-particulate second binder in the solid electrolyte layer, when the total mass of the solid electrolyte layer is set to 100% by mass, can be included in a quantity greater than 0% by mass and less than 1.0% by mass, or greater than 0% by mass and less than 0.7% by mass.

[0120] The thickness of the solid electrolyte layer is adjusted appropriately according to the battery structure and is not particularly limited, but is usually above 0.1μm and below 1mm.

[0121] Regarding the method of forming a solid electrolyte layer, for example, the solid electrolyte layer can be formed by pressing a powder of a material containing a solid electrolyte and other components as needed into a solid electrolyte layer. Alternatively, the solid electrolyte layer can be formed by coating a slurry containing an adhesive onto a support, drying the slurry, and then peeling off the support.

[0122] All-solid-state batteries require the following: an outer casing that houses the positive electrode, negative electrode, and solid electrolyte layer.

[0123] There are no particular limitations on the shape of the outer casing; examples include laminated types.

[0124] There are no particular restrictions on the material of the outer casing as long as it is a material that is stable to the electrolyte. Examples include polypropylene, polyethylene, and acrylic resins.

[0125] Examples of all-solid-state batteries include: all-solid-state lithium batteries that utilize the deposition-dissolution reaction of metallic lithium as the negative electrode; all-solid-state lithium-ion batteries that allow lithium ions to move between the positive and negative electrodes; all-solid-state sodium batteries; all-solid-state magnesium batteries; and all-solid-state calcium batteries, etc. Furthermore, all-solid-state batteries can be either primary or secondary batteries.

[0126] Examples of solid-state battery shapes include coin-shaped, laminated, cylindrical, and square.

[0127] 2. All-solid-state battery

[0128] This disclosure provides a method for manufacturing an all-solid-state battery, characterized in that the method comprises manufacturing an all-solid-state battery having a positive electrode including a positive electrode layer, a negative electrode including a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The method for manufacturing the all-solid-state battery includes the following steps:

[0129] A process of preparing at least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, using at least a dispersion of the first binder and a solution of the second binder.

[0130] The information regarding the positive electrode, negative electrode, and solid electrolyte layer is the same as described in section 1. All-solid-state battery above, so it is omitted here.

[0131] As a method for manufacturing the all-solid-state battery disclosed herein, for example, firstly, a slurry for a solid electrolyte layer comprising at least a dispersion of a first binder, a solution of a second binder, and a solid electrolyte is coated onto a support. The solid electrolyte layer slurry is then dried, and the support is peeled off, thereby forming a solid electrolyte layer. Next, a slurry for a positive electrode layer comprising at least a dispersion of the first binder, a solution of the second binder, and a positive electrode active material is coated onto one side of the positive electrode current collector. The positive electrode layer slurry is then dried, thereby obtaining a positive electrode comprising a positive electrode layer. Then, a slurry for a negative electrode layer comprising at least a dispersion of the first binder, a solution of the second binder, and a negative electrode active material is coated onto one side of the negative electrode current collector. The negative electrode layer slurry is then dried, thereby obtaining a negative electrode comprising a negative electrode layer. Finally, the solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer in the order of positive electrode current collector, positive electrode layer, solid electrolyte layer, negative electrode layer, and negative electrode current collector, thereby obtaining an all-solid-state battery.

[0132] Regarding the first binder and solvent contained in the dispersion used in the preparation process, and the second binder and solvent contained in the dissolution, the same substances as those listed in 1. All-solid-state batteries above can be used. It should be noted that the first and second binders are mixed to form a slurry, which is then dried to form the positive electrode layer, the solid electrolyte layer, and the negative electrode layer. In order to maintain the dispersion of the first binder and the dissolution of the second binder even in this slurry state, the solvents for the first and second binders are ideally solvents that disperse the first binder and dissolve the second binder.

[0133] The method of dispersing the first adhesive is not particularly limited. For example, methods such as using an ultrasonic homogenizer to disperse the first adhesive in a solvent can be listed.

[0134] In the preparation process, when preparing at least one layer selected from the group consisting of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, a dispersion of the first adhesive and a solution of the second adhesive can be used. When preparing all layers of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, a dispersion of the first adhesive and a solution of the second adhesive can also be used.

[0135] The amount of the particulate first binder used in the preparation process is not particularly limited. When the total mass (amount of solid components in the slurry) of any of the obtained positive electrode layer, negative electrode layer, or solid electrolyte layer is set to 100% by mass, the lower limit of the content of the first binder can be 0.01% by mass or more, particularly 0.1% by mass or more, particularly 0.2% by mass or more, further 1.0% by mass or more, and even more 3.0% by mass or more, and the upper limit can be 8.0% by mass or less, particularly 7.0% by mass or less, and further 5.0% by mass or less. Specifically, when the amount of solid components in the slurry used to make the layer is set to 100% by mass, the amount of the first binder can be 0.01% by mass or more and 10.0% by mass or less, preferably 0.1% by mass or more and 8.0% by mass or less, more preferably 0.2% by mass or more and 7.0% by mass or less, further preferably 1.0% by mass or more and 7.0% by mass or less, and particularly preferably 3.0% by mass or more and 5.0% by mass or less.

[0136] The amount of the second binder used in the preparation process is not particularly limited. When the total mass of any layer among the obtained positive electrode layer, negative electrode layer or solid electrolyte layer (the amount of solid components in the slurry) is set to 100% by mass, the content of the second binder can be more than 0% by mass and less than 1.0% by mass, or more than 0% by mass and less than 0.7% by mass.

[0137] It is best to manufacture all-solid-state batteries in a state where moisture in the system is removed as much as possible. For example, it can be considered effective to reduce the pressure in the system or to replace the moisture in the system with gases that are essentially free of moisture, such as inert gases, during each manufacturing process.

[0138] Example (Example 1)

[0139] • Preparation of the first adhesive dispersion in particulate form

[0140] Dehydrated toluene, used as a solvent, and PVDF powder (particle size 1.5 μm), used as a particulate first binder, were mixed at a mass ratio of 90:10. The dehydrated toluene was kept at a liquid temperature below 30°C, and the PVDF powder was added while stirring. The mixture was stirred using a magnetic stirrer for at least 1 hour to prepare a first binder dispersion in which the particles were dispersed in the solvent.

[0141] • Production of the positive electrode

[0142] With positive electrode active material (Li(NiMnCo)) 1 / 3 The mixture of positive electrode active material (O2) and sulfide-based solid electrolyte (LiI-LiO2-Li2S-P2S5, a synthetic product of our company) in a mass ratio of 75:25 is weighed such that the positive electrode layer contains 93.5% by mass when the total mass of the positive electrode layer is set to 100% by mass.

[0143] Next, a PVDF binder dispersion (PVDF powder: particle size 1.5 μm) was weighed in the positive electrode layer such that it contained 3.0% by weight of solids when the total mass of the positive electrode layer was set to 100% by weight, and a conductive material (vapor-grown carbon fiber, manufactured by Showa Denko Corporation) was weighed in the positive electrode layer such that it contained 3.0% by weight when the total mass of the positive electrode layer was set to 100% by weight.

[0144] Furthermore, toluene (dehydration grade) was added as a solvent, and the mixture was kneaded for 1 minute using an ultrasonic homogenizer (manufactured by SMT Corporation, UH-50).

[0145] Finally, a second binder solution, prepared by dissolving ethyl cellulose (EC, produced by Nacalai tesque) in toluene, was added to the positive electrode layer, with 0.5% EC in the positive electrode layer when the total mass of the positive electrode layer was set to 100% by mass, to obtain a positive electrode mixture. Toluene was added to the positive electrode mixture to make the solid content 60% by mass, and the mixture was kneaded for 1 minute using an ultrasonic homogenizer, thereby producing a slurry for the positive electrode layer.

[0146] Then, using an applicator, a slurry for the positive electrode layer is applied to the surface of aluminum foil (manufactured by Showa Denko Corporation). After allowing it to dry naturally for 5 minutes, it is heated and dried at 100°C for 30 minutes to form the positive electrode layer, thus creating a positive electrode with a positive current collector and a positive electrode layer.

[0147] • Negative electrode production

[0148] The mixture was prepared by mixing the negative electrode active material (natural graphite, particle size 15.0 μm) and the sulfide-based solid electrolyte (LiI-LiO2-Li2S-P2S5, a synthetic product of our company) in a mass ratio of 60:40, and weighing the mixture so that when the total mass of the negative electrode layer is set to 100% by mass, the negative electrode layer contains 96.5% by mass.

[0149] In addition, a first binder dispersion containing PVDF (particle size 1.5 μm) was weighed in such a way that the total mass of the negative electrode layer was set to 100% by mass and the negative electrode layer contained 3.0% by mass of PVDF in terms of solids.

[0150] Furthermore, toluene (dehydration grade) was added as a solvent, and the mixture was kneaded for 1 minute using an ultrasonic homogenizer (manufactured by SMT Corporation, UH-50).

[0151] Finally, a second binder solution, prepared by dissolving ethyl cellulose (EC, produced by Nacalai tesque) in toluene, was added to the negative electrode layer, with 0.5% EC in the negative electrode layer when the total mass of the negative electrode layer was set to 100% by mass, to obtain a negative electrode mixture. Then, toluene was added to the negative electrode mixture to make the solid content of the negative electrode mixture 55% by mass, and the mixture was kneaded for 1 minute using an ultrasonic homogenizer, thereby producing a slurry for the negative electrode layer.

[0152] Then, a negative electrode layer slurry is applied to the surface of the negative electrode current collector (copper foil) using a coater. After allowing it to dry naturally for 5 minutes, it is heated and dried at 100°C for 30 minutes to form a negative electrode layer, thus creating a negative electrode with a negative electrode current collector and a negative electrode layer.

[0153] • Fabrication of solid electrolyte layer

[0154] In an inert gas atmosphere, a first binder dispersion containing PVDF (particle size 1.5 μm) was added to 96.5 parts by mass of a sulfide-based solid electrolyte material, with 3.0 parts by mass of PVDF as solids and a second binder solution containing ethyl cellulose (EC, produced by Nacalai tesque) dissolved in toluene as solids, and 0.5 parts by mass of EC, to obtain a mixture.

[0155] Then, toluene is added as a solvent, and the solution, which is added in a manner where the solid content is 35% by mass, is mixed using an ultrasonic homogenizer (UH-50 manufactured by SMT Corporation), thereby obtaining a slurry for a solid electrolyte layer.

[0156] A slurry for applying a solid electrolyte layer is coated onto aluminum foil using a coater and then dried to obtain the solid electrolyte layer.

[0157] • Fabrication of all-solid-state batteries

[0158] The aluminum foil and solid electrolyte layer were punched to a 1cm diameter. 2 The aluminum foil is peeled off, and a solid electrolyte layer is sandwiched between the positive electrode layer of the positive electrode and the negative electrode layer of the negative electrode and overlapped. Then it is pressed with 4.3 tons to obtain an all-solid-state battery.

[0159] (Example 2)

[0160] The particle size of the PVDF powder was changed to 0.1 μm, and otherwise all-solid-state batteries were fabricated in the same manner as in Example 1.

[0161] (Example 3)

[0162] The particle size of the PVDF powder was changed to 90.0 μm, and otherwise, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0163] (Example 4)

[0164] The particle size of the PVDF powder was changed to 0.6 μm, and otherwise all solid-state batteries were fabricated in the same manner as in Example 1.

[0165] (Example 5)

[0166] The particle size of the PVDF powder was changed to 15.3 μm, and otherwise all-solid-state batteries were fabricated in the same manner as in Example 1.

[0167] (Example 6)

[0168] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0169] The first binder, which was in particulate form, was changed to SBR. The particle size of the SBR powder was 0.1 μm.

[0170] In addition, the solvent was changed from toluene to dehydrated methyl ethyl ketone (MEK).

[0171] (Example 7)

[0172] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0173] The first binder, which was in particulate form, was changed to SBR. The particle size of the SBR powder was 1.0 μm.

[0174] In addition, the solvent was changed from toluene to dehydrated methyl ethyl ketone (MEK).

[0175] (Example 8)

[0176] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0177] The first binder, which was in particulate form, was changed to SBR, and the SBR powder had a particle size of 94.2 μm.

[0178] In addition, the solvent was changed from toluene to dehydrated methyl ethyl ketone (MEK).

[0179] (Example 9)

[0180] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0181] The content of PVDF powder was changed to 0.3% by mass. For the positive electrode layer, the content of the mixture of positive electrode active material and solid electrolyte was changed to 96.2% by mass. For the negative electrode layer, the content of the mixture of negative electrode active material and solid electrolyte was changed to 99.2% by mass. For the solid electrolyte layer, the content of solid electrolyte was changed to 99.2% by mass.

[0182] (Example 10)

[0183] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0184] The content of PVDF powder was changed to 5.0% by mass. For the positive electrode layer, the content of the mixture of positive electrode active material and solid electrolyte was changed to 91.5% by mass. For the negative electrode layer, the content of the mixture of negative electrode active material and solid electrolyte was changed to 94.5% by mass. For the solid electrolyte layer, the content of solid electrolyte was changed to 94.5% by mass.

[0185] (Example 11)

[0186] The particle size of the PVDF powder was changed to 0.06 μm, and otherwise all-solid-state batteries were fabricated in the same manner as in Example 1.

[0187] (Example 12)

[0188] The particle size of the PVDF powder was changed to 136.8 μm, and otherwise, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0189] (Example 13)

[0190] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0191] The first binder, which was in particulate form, was changed to SBR. The particle size of the SBR powder was 0.03 μm.

[0192] In addition, the solvent was changed from toluene to dehydrated methyl ethyl ketone (MEK).

[0193] (Example 14)

[0194] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0195] The first binder, which was in particulate form, was changed to SBR. The particle size of the SBR powder was 154.5 μm.

[0196] In addition, the solvent was changed from toluene to dehydrated methyl ethyl ketone (MEK).

[0197] (Comparative Example 1)

[0198] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0199] PVDF (particle size 1.5 μm) was dissolved using dehydrated N-methylpyrrolidone (NMP) as a solvent to prepare a second binder solution containing PVDF. This solution was then used in conjunction with a second binder solution prepared by dissolving ethyl cellulose (EC, produced by Nacalai Tesque) in toluene, thus changing the solvent used to prepare the slurry to dehydrated N-methylpyrrolidone (NMP). In Comparative Example 1, an all-solid-state battery without particulate first binder was fabricated.

[0200] (Comparative Example 2)

[0201] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0202] Without adding the second binder solution using EC, the content ratio of the mixture of positive electrode active material and solid electrolyte in the positive electrode layer was changed to 94.0% by mass, the content ratio of the mixture of negative electrode active material and solid electrolyte in the negative electrode layer was changed to 97.0% by mass, and the content ratio of solid electrolyte in the solid electrolyte layer was changed to 97.0% by mass. That is, in Comparative Example 2, an all-solid-state battery without non-particulate second binder was produced.

[0203] (Example 15)

[0204] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0205] The content of PVDF powder was changed to 0.1% by mass. For the positive electrode layer, the content of the mixture of positive electrode active material and solid electrolyte was changed to 96.4% by mass. For the negative electrode layer, the content of the mixture of negative electrode active material and solid electrolyte was changed to 99.4% by mass. For the solid electrolyte layer, the content of solid electrolyte was changed to 99.4% by mass.

[0206] (Example 16)

[0207] Except for the following, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0208] The content of PVDF powder was changed to 8.0% by mass. For the positive electrode layer, the content of the mixture of positive electrode active material and solid electrolyte was changed to 88.5% by mass. For the negative electrode layer, the content of the mixture of negative electrode active material and solid electrolyte was changed to 91.5% by mass. For the solid electrolyte layer, the content of solid electrolyte was changed to 91.5% by mass.

[0209] Peel strength test

[0210] The peel strength of each electrode layer of the positive and negative electrode layers used in the embodiments and comparative examples was measured. It should be noted that in this embodiment, the peel strength was measured by the following method, but the peel strength measurement in the implementation of the present invention is not limited to the following method, and other methods can also be used to measure the peel strength.

[0211] One side of the double-sided tape was attached to the surface of the electrode layer, and the other side was attached to the metal plate. The metal plate was fixed in place, and the portion of the metal plate other than the area bonded to the electrode layer via the double-sided tape was connected to the load cell. The metal plate was then moved vertically at a speed of 50 mm / min. The peel strength of the electrode layer was calculated by dividing the average load applied to the load cell by the width of the electrode layer (2 cm). The results are shown in Tables 1 and 2. In Tables 1 and 2, Li(NiMnCo)... 1 / 3 O2 is denoted as NMC111.

[0212] • Li ionic conductivity (ion conductivity) measurement

[0213] For each all-solid-state battery obtained in the examples and comparative examples, the Li-ion conductivity at room temperature was measured using AC impedance spectroscopy. A Solartron 1260 was used, and the measurement conditions were set to an applied voltage of 10 mV and a measurement frequency range of 0.01 MHz to 1 MHz. The results are shown in Tables 1 and 2.

[0214] It should be noted that the test cells of the all-solid-state batteries obtained in the examples and comparative examples were fabricated using the following methods.

[0215] First, the all-solid-state batteries were charged at a constant current of 0.1C at 25℃±4℃ until the terminal voltage of each battery reached the set voltage. Then, they were charged for 1 hour using a constant current and constant voltage charging method to maintain the set voltage. After the initial charge, they were discharged at a constant current and constant voltage of 0.2C for 10 hours until they reached 3.0V.

[0216] Then, it was charged to 4.0V at a constant current of 0.2C at an environment of 25℃±4℃.

[0217] Thus, a test cell for measuring the conductivity of Li ions was created.

[0218] Cyclic test

[0219] For the test cells of the all-solid-state battery, under an environment of 40°C, a cycle was defined as constant current and constant voltage charging at 1C for 2.5 hours to 4.5V and constant current discharging at 1C to 3.0V. This cycle was performed for 300 cycles. Then, the discharge capacity A of the 300th cycle was divided by the discharge capacity B of the 5th cycle and multiplied by 100 to calculate the cycle characteristics (capacity retention rate (%)).

[0220] It should be noted that for each capacity retention rate (%) of the examples and comparative examples, three test cells of each all-solid-state battery of the examples and comparative examples were made, and the average value of the cycle test results of the three test cells was used.

[0221]

[0222]

[0223] Based on the results of Examples 1 to 16 and Comparative Examples 1 to 2, it can be seen that by using both a particulate first adhesive and a non-particulate second adhesive, the cycle characteristics of the all-solid-state battery can be improved compared with the case of using only one of them.

[0224] Regarding the average particle size of the particulate first binder, a comparison between Examples 1-5 and Example 12, and between Examples 6-8 and Example 14, shows that when the average particle size of the particulate first binder is less than 130.0 μm, the peel strength of the electrode layer is improved. As a result, it is easier to maintain the electrode structure as the electrode layer expands and contracts during charging and discharging, thus improving the cycle characteristics of the all-solid-state battery.

[0225] Furthermore, based on the comparison between Examples 1-5 and Example 11, and between Examples 6-8 and Example 13, when a first adhesive with an average particle size exceeding 0.1 μm is used, the adhesion between the active material particles and the solid electrolyte particles (peel strength of the electrode layer) decreases slightly, but the adhesive becomes easier to partially rather than completely cover the interface between the active material particles and the solid electrolyte particles, thus improving the ionic conductivity of the all-solid-state battery.

[0226] Furthermore, it is known that if the average particle size of the first adhesive particles is in the range of 0.1 to 80.0 μm, the bonding effect of the first adhesive particles and the resistance reduction effect of the all-solid-state battery are well balanced, which can further improve the cycle characteristics of the all-solid-state battery.

[0227] Regarding the amount of particulate first binder added (Examples 9, 10, 15, 16), it is known that if a large amount of particulate first binder is added, the adhesion is improved; if a small amount of particulate first binder is added, the opposite phenomenon occurs. By using both particulate first binder and non-particulate second binder, the cycle characteristics of the all-solid-state battery are improved by including 0.1 to 8.0% by mass of particulate first binder in the layer. By including 0.2 to 7.0% by mass, the cycle characteristics of the all-solid-state battery are further improved.

[0228] This application is a patent application that claims priority to Japanese Patent Application No. 2019-099704, filed on May 28, 2019, and the contents set forth in the description, claims and drawings of that application are incorporated herein by reference.

[0229] Industrial availability

[0230] According to the present invention, the cycle characteristics of all-solid-state batteries can be improved. Therefore, according to the present invention, it is expected to promote the further popularization of all-solid-state batteries.

[0231] Symbol Explanation

[0232] 1. Active substance particles

[0233] 2. Non-particulate second adhesive

[0234] 3. Particle-like first adhesive

[0235] 11 Solid electrolyte layer

[0236] 12 Positive Electrode Layer

[0237] 13 Negative Electrode Layer

[0238] 14 Positive current collector

[0239] 15 Negative current collector

[0240] 16 Positive electrode

[0241] 17 Negative electrode

[0242] 100 All-Solid-State Battery

Claims

1. An all-solid-state battery, said all-solid-state battery having: A positive electrode comprising a positive electrode layer, a negative electrode comprising a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. At least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises a particulate first binder and a non-particulate second binder. The first adhesive is a fluorinated resin with an average particle size of 0.5 μm or more and 130 μm or less. The second adhesive is an alkylated derivative of cellulose.

2. The all-solid-state battery according to claim 1, wherein, When the total mass of the layer containing the first adhesive and the second adhesive is set to 100% by mass, the layer contains 0.2 to 7.0% by mass of the first adhesive.

3. The all-solid-state battery according to claim 1 or 2, wherein, When the total mass of the layer containing the first adhesive and the second adhesive is set to 100% by mass, the layer contains more than 0% by mass and less than 1.0% by mass of the second adhesive.

4. A method for manufacturing an all-solid-state battery, the method comprising manufacturing an all-solid-state battery having a positive electrode including a positive electrode layer, a negative electrode including a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, the method comprising the following steps: A process for preparing at least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, using a dispersion of the first binder and a solution of the second binder. The first adhesive is a fluorinated resin with an average particle size of 0.5 μm or more and 130 μm or less. Furthermore, the second adhesive is an alkylated derivative of cellulose.

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