Abstract: To obtain a lithium ion secondary battery having excellent charge and discharge characteristics in which electric connection between active material layers and a separator can be maintained without requiring a strong armor metal case, so that it can be made into thin forms having large energy density. Convex parts and concave parts are formed on at least two surfaces among surfaces of a positive electrode active material layer 7 and a negative electrode active material layer 9 both adjacent to a separator 4 and surfaces of the separator 4 facing both of the active material layers 7, 9, and these three means are bonded and closely adhered by an adhesive resin layer 11 and electrically connected by keeping a lithium ion-containing electrolytic solution in the separator 4 and voids 12 formed by a bonded surface 11a of the convex parts and the concave parts.

Abstract: A dielectric ceramic material essentially consists of a complex perovskite compound mainly composed of Ba(Mg.sub.1/3 Ta.sub.2/3)O.sub.3 phase and 0.005 to 1.0% by weight of phosphorus with reference to the complex perovskite compound.As one of the dielectric properties, the unloaded Q value reaches 37000 at a measuring frequency of 10 GHz and the temperature coefficient of the resonant frequency is about 4 ppm/.degree.C.