A solid-state battery that includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer, where the negative electrode layer includes a conductive additive containing a metal material having an elongated shape in a section view at 7% to 28% in area ratio with respect to the negative electrode layer.

There is provided an electrode composition containing a sulfide-based inorganic solid electrolyte, a polymer binder, an active material having a specific surface area of 10 m.sup.2/g or more, and a dispersion medium, in which a polymer that forms the polymer binder has a constitutional component derived from a (meth)acrylic monomer or vinyl monomer, which has an SP value of 19.0 MPa.sup.1/2 or more. There also provided an electrode sheet for all-solid state secondary battery and an all-solid state secondary battery, and manufacturing methods for an electrode sheet for an all-solid state secondary battery and an all-solid state secondary battery, in which the electrode composition is used.

There is provided an electrode composition containing a sulfide-based inorganic solid electrolyte, a polymer binder, an active material having a specific surface area of 10 m.sup.2/g or more, and a dispersion medium, in which a polymer that forms the polymer binder has a constitutional component derived from a (meth)acrylic monomer or vinyl monomer, which has an SP value of 19.0 MPa.sup.1/2 or more. There also provided an electrode sheet for all-solid state secondary battery and an all-solid state secondary battery, and manufacturing methods for an electrode sheet for an all-solid state secondary battery and an all-solid state secondary battery, in which the electrode composition is used.

A positive-electrode material according to the present disclosure includes a positive-electrode active material and a coating layer covering the positive-electrode active material, wherein the coating layer contains lithium and carbon, the positive-electrode active material and the coating layer constitute a coated active material, and the ratio C/Li of the carbon content to the lithium content in a surface layer portion of the coated active material is 3.27 or more based on the atomic ratio.

A positive-electrode material according to the present disclosure includes a positive-electrode active material and a coating layer covering the positive-electrode active material, wherein the coating layer contains lithium and carbon, the positive-electrode active material and the coating layer constitute a coated active material, and the ratio C/Li of the carbon content to the lithium content in a surface layer portion of the coated active material is 3.27 or more based on the atomic ratio.

A positive-electrode material according to the present disclosure includes a positive-electrode active material and a coating layer covering the positive-electrode active material, wherein the coating layer contains oxygen and lithium, the positive-electrode active material and the coating layer constitute a coated active material, and the ratio Li/O of the lithium content to the oxygen content in a surface layer portion of the coated active material is 0.26 or less based on the atomic ratio.

A positive-electrode material according to the present disclosure includes a positive-electrode active material and a coating layer covering the positive-electrode active material, wherein the coating layer contains oxygen and lithium, the positive-electrode active material and the coating layer constitute a coated active material, and the ratio Li/O of the lithium content to the oxygen content in a surface layer portion of the coated active material is 0.26 or less based on the atomic ratio.

A covered positive electrode active material includes a particulate positive electrode active material and a solid electrolyte that covers a surface of the positive electrode active material. The solid electrolyte forms a covering layer. The covering layer is formed such that recessed portions of the surface of the positive electrode active material are filled with the solid electrolyte. Protruding portions of the surface of the positive electrode active material are exposed on a surface of the covered positive electrode active material. A degree of unevenness of a group of particles of the positive electrode active material is defined as ζ.sub.1, a degree of unevenness of a group of particles of the covered positive electrode active material is defined as ζ.sub.2, and a degree of change in unevenness R defined by formula (2) below is greater than or equal to 1.1.

R=ζ.sub.2/ζ.sub.1   (2)

A covered positive electrode active material includes a particulate positive electrode active material and a solid electrolyte that covers a surface of the positive electrode active material. The solid electrolyte forms a covering layer. The covering layer is formed such that recessed portions of the surface of the positive electrode active material are filled with the solid electrolyte. Protruding portions of the surface of the positive electrode active material are exposed on a surface of the covered positive electrode active material. A degree of unevenness of a group of particles of the positive electrode active material is defined as ζ.sub.1, a degree of unevenness of a group of particles of the covered positive electrode active material is defined as ζ.sub.2, and a degree of change in unevenness R defined by formula (2) below is greater than or equal to 1.1.

R=ζ.sub.2/ζ.sub.1   (2)

The production method of the present disclosure includes: heat-treating a material mixture containing LiA, YB.sub.3, GdC.sub.3, and CaD.sub.2 in an inert gas atmosphere. A, B, C, and D are each independently at least one selected from the group consisting of F, Cl, Br, and I. In the heat-treating, the material mixture is heat-treated at higher than or equal to 200° C. and lower than or equal to 700° C.