Irreversible additive contained in positive electrode material for secondary battery, positive electrode material comprising same, and secondary battery comprising positive electrode material

An embodiment of the present invention relates to an irreversible additive included in a positive electrode material for a secondary battery, the irreversible additive being an oxide represented by the following Chemical Formula 1, where the oxide has a trigonal crystal structure, Li2 + aNi1-bTibO2 + c (1) In the formula,-0.2 < = a < = 0.2, 0lt; b < = 0.2, and 0 < = c < = 0.2. 本发明的实施方式涉及一种包含在二次电池用正极材料中的不可逆添加剂，所述不可逆添加剂是下述化学式1表示的氧化物，其中所述氧化物具有三方晶系晶体结构，Li2+aNi1-bTibO2+c(1)在上式中，-0.2≤a≤0.2，0