NOVELTY - A cathode active material comprises 1st cathode material consisting of layered rocksalt-type lithium metal oxide and layered rocksalt-type containing lithium and metal other than lithium in which metal is nickel (Ni) or Ni and cobalt (Co), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), aluminum (Al), chromium (Cr), vanadium (V), titanium (Ti), magnesium (Mg), and/or zirconium (Zr). A site occupancy of metal ions other than lithium at a 3a site obtained by Rietveld analysis of powder X-ray diffraction pattern of the 1st cathode material in a cathode at a discharged state is less than or equal to 5%.    USE - A cathode active material for cathode of battery used for battery pack, electronic apparatus, electric vehicle, electric storage apparatus, and electric power system (all claimed).    ADVANTAGE - Increase in resistance is suppressed, and cycle characteristics are improved.    DETAILED DESCRIPTION - A cathode active material comprises 1st cathode material consisting of layered rocksalt-type lithium metal oxide and layered rocksalt-type containing lithium and metal other than lithium in which metal is nickel (Ni) or Ni and cobalt (Co), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), aluminum (Al), chromium (Cr), vanadium (V), titanium (Ti), magnesium (Mg), and/or zirconium (Zr). A site occupancy of metal ions other than lithium at a 3a site obtained by Rietveld analysis of powder X-ray diffraction pattern of the 1st cathode material in a cathode at a discharged state is less than or equal to 5%, and a site occupancy of metal ions other than the metal occupying a part of a 3b site at the 3b site is greater than or equal to 1%. The cathode active material is covered with a coating film, and an exposed number of the cathode active material exposed from the coating film is 0.05-8% both inclusive. INDEPENDENT CLAIMS are included for:    (1) battery comprising cathode (21), anode (22), and electrolyte in which cathode contains cathode active material;    (2) battery pack comprising battery and package containing the battery;    (3) electric vehicle comprising battery, converter receiving electric power from battery and converting electric power into driving force for vehicle, and controller performing information processing relating to vehicle control based on information on the battery;    (4) electric storage apparatus comprising battery in which the apparatus supplies electric power to electronic apparatus connected to the battery; and    (5) electric power system which receives electric power from battery or supplies electric power from generator or electric power network to the battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional diagram of a non-aqueous electrolyte battery.    Battery can (11)    Insulating plates (12, 13)    Battery cover (14)    Cathode (21)    Anode (22)