Lithium secondary battery and cathode active material for use in lithium secondary battery

A lithium secondary battery comprising:

• a cathode including material that can be doped/undoped with lithium ions as an active material;
• an anode including a lithium metal, a lithium alloy, or a material that can be doped/undoped with lithium ions as an active material;
• and
• a liquid or solid electrolyte,
• wherein lithiated nickel dioxide containing tin is used as the cathode active material, and said lithiated nickel dioxide is produced by firing a mixture of a lithium compound, a nickel compound and tin or a tin compound at a temperature of from 350° C. to 800° C., has a peak near 2θ=34.4° and does not have a peak at 2θ=22.5° in the X-ray diffraction pattern by CuK α rays, or the intensity ratio of the peak at 2θ=22.5° to a peak assigned to the diffraction line (200) of lithium stannate (Li2SnO3) is 1.2 or less, wherein the X-ray diffraction pattern is measured under the conditions of:
• X-ray:
• CuK α;
• Voltage-Current:
• 40 kV-30mA;
• Range of measured angle:
• 2θ=15 to 90°;
• Slit:
• DS-1°, RS-0.3 mm, SS-1°;
• Step:
• 0.02°;
• and
• Counting time:
• 1 second.