Cathode active material for lithium secondary battery
View Patent ↗Provided is a cathode active material which is lithium transition metal oxide having an α-NaFeO 2 layered crystal structure, wherein the transition metal is a blend of Ni and Mn, an average oxidation number of the transition metals except lithium is +3 or higher, and lithium transition metal oxide satisfies the Equation m(Ni)≧m(Mn) (in which m (Ni) and m (Mn) represent an molar number of manganese and nickel, respectively). The lithium transition metal oxide has a uniform and stable layered structure through control of oxidation number of transition metals to a level higher than +3, thus advantageously exerting improved overall electrochemical properties including electric capacity, in particular, superior high-rate charge/discharge characteristics.
1. A cathode active material for lithium secondary batteries,
wherein the cathode active material is lithium transition metal oxide having a layered crystal structure,
wherein the layered crystal structure is an α-NaFeO 2 layered crystal structure, and
wherein the transition metal is a blended transition metal of Ni and Mn, and an average oxidation number of transition metals except lithium is 3.03 to 3.3 and the lithium transition metal oxide satisfies Equation 1 below:
m (Ni)≧m(Mn) (1)
wherein m (Ni) and m (Mn) represent a molar number of nickel salt and manganese salt, respectively.
2. The cathode active material according to claim 1 , wherein the lithium transition metal oxide further comprises cobalt.
3. The cathode active material according to claim 1 , wherein the average oxidation number of transition metals except lithium is 3.1 to 3.3.
4. A cathode comprising the cathode active material according to claim 1 .
5. A lithium secondary battery comprising the cathode according to claim 4 .