PLATE-SHAPED PARTICLES FOR POSITIVE ELECTRODE ACTIVE MATERIAL OF LITHIUM SECONDARY BATTERIES, AND LITHIUM SECONDARY BATTERIES

By exposing the crystal plane (a plane other than the (003) plane: e.g., the (101) plane and (104) plane) through which lithium ions are favorably intercalated and deintercalated, more to an electrolyte, characteristics such as cell capacity is improved. The present invention relates a plate-like particle for a lithium secondary battery cathode active material. The particle has a layered rock salt structure. The (003) plane is oriented in a direction intersecting a particle plate surface. The porosity is 10% or less. The ratio of an observed surface area (²) determined from a measured value of a BET specific surface area to a virtual surface area (±) of the particle which is defined by the planar shape and thickness of the particle on the assumption that the plate surface is smooth, ²/± is 3 or more and 10 or less