Lithium ion secondary battery and process for manufacturing the same

A lithium ion secondary battery, which is a multilayer all solid state battery including a laminate in which a positive electrode layer and a negative electrode layer are stacked alternately interposed by a solid electrolyte layer, said positive electrode layer and/or said negative electrode layer having a structure where active material is supported by conductive matrix composed of conductive material, wherein the area ratio of said active material to said conductive material ranges from 20:80 to 65:35 at the cross-sectional surface of said positive electrode layer and/or said negative electrode layer.

A manufacturing method of a lithium ion secondary battery comprising the steps of:

• dispersing solid electrolyte material in binder and solvent to form paste for solid electrolyte layer, coating and drying said paste for solid electrolyte layer to form green-sheet for solid electrolyte layer, mixing active material and conductive material to form mixture and dispersing said mixture in binder and solvent to form paste for positive electrode layer and/or negative electrode layer, coating and drying said paste for positive electrode layer and/or said paste for negative electrode layer to form green-sheet for positive electrode layer and/or green-sheet for negative electrode layer, stacking said green-sheet for positive electrode layer and said green-sheet for negative electrode layer alternately interposed by said green-sheet for solid electrolyte layer to form a laminate, and co-firing said laminate to form a sintered laminate, wherein volume mixing ratio of said active material, and said conductive material ranges from 20:80 to 65:35.