LITHIUM SECONDARY BATTERY

Provided is a lithium secondary battery that is of the integrated sintered plate type in which a positive electrode layer, a ceramic separator, and a negative electrode layer are bonded together and that can achieve both high yield and excellent battery performance. The lithium secondary battery includes a positive electrode layer composed of a lithium complex oxide sintered body, a negative electrode layer composed of a titanium-containing sintered body, a ceramic separator, an electrolytic solution, and an exterior body including a closed space, the closed space accommodating the positive electrode layer, the negative electrode layer, the ceramic separator, and the electrolytic solution, wherein the positive electrode layer, the ceramic separator, and the negative electrode layer are bonded together, the ceramic separator is composed of MgO and glass, and when a cross section at the interface between the negative electrode layer and the ceramic separator is observed, a ratio of a region occupied by glass grains having a length of 1 µm or more in a direction parallel to the interface with respect to a region occupied by glass grains constituting the interface is 3 to 80%.