Provided is a layer for preventing a short circuit between a positive electrode and a negative electrode in a solid battery using a layer containing a solid electrolyte. As the solid electrolyte between the positive electrode and the negative electrode, a layer containing a graphene compound is used. Lithium ions can pass through the layer containing the graphene compound. Lithium ions are added in advance in the layer containing the graphene compound. Specifically, a modifier is used, and a graphene compound chemically modified with a functional group such as ether and ester with an increasedinterlayer distance is used.