ALL-SOLID LITHIUM BATTERY - Patent - all-solid lithium secondary battery has excellent reliability including safety An all-solid lithium secondary battery has excellent reliability including safety. However, in general, its energy density or output density is lower than that achieved by liquid electrolyte systems. The all-solid lithium battery includes a lithium ion-conducting solid electrolyte as an electrolyte. The lithium ion-conducting solid electrolyte is mainly composed of a sulfide, and the surface of a positive electrode active material is coated with a lithium ion-conducting oxide. The advantages of the present invention are particularly significant when the positive electrode active material exhibits a potential of 3 V or more during operation of the all-solid lithium battery, i.e., when redox reaction occurs at a potential of 3 V or more.According to the present invention, the surface of the positive electrode active material is coated with a lithium ion-conducting oxide so that the lithium ion-conducting oxide is interposed between the positive electrode active material and the solid electrolyte mainly composed of a sulfide to suppress formation of the high-resistance layer. Examples of the method for forming a structure including a positive electrode active material, a solid electrolyte mainly composed of a sulfide, and a lithium-ion conducting oxide between the positive electrode active material and the solid electrolyte include a method in which the surfaces of the positive electrode active material particles are coated with a lithium ion-conducting oxide and the positive electrode active material particles are mixed with a solid electrolyte powder mainly composed of the sulfide to form an electrode and a method in which the positive electrode active material thin film surface is coated with a lithium ion-conducting oxide and brought into contact with the solid electrolyte mainly composed of a sulfide.
