Patent ID: 8647772

Claim:
A cathode active material mixture comprising: a lithium composite oxide which contains the highest proportion of nickel among constituent metal elements except lithium; and a phosphorus compound which is contained near a surface of the lithium composite oxide, wherein a peak of a fragment of at least one secondary ion selected from the group consisting of positive secondary ions of Li 4 PO 4 , C 3 F 5 , C 5 F 9 , C 7 F 13 , negative secondary ions of PO 2 , PO 3 , LiP 2 O 4 , LiP 2 O 5 , LiP 2 O 6 , LiPO 2 F, LiPO 3 F, POF 2 , PO 2 F 2 , and LiPO 3 H based on a surface analysis by TOF-SIMS is observed near the surface, and wherein a concentration of carbonate and bicarbonate in the cathode active material is greater than 0 and not more than 0.30% by weight.