LITHIUM COMPOSITE OXIDE SINTERED PLATE AND ALL-SOLID-STATE SECONDARY BATTERY

There is provided a lithium composite oxide which is composed of a lithium composite oxide having a layered rock salt structure containing Li, Ni, Co and Mn. The lithium composite oxide sintered plate has a porosity of 20 to 40%, a mean pore diameter of 3.5 μm or larger and an interfacial length per 1 μmof unit cross-sectional area of 0.45 μm or shorter.