CATHODE ACTIVE MATERIAL, CATHODE COMPRISING SAME, AND SECONDARY BATTERY

Provided are a cathode active material, a cathode comprising same, and a secondary battery. The cathode active material contains crystal water and a manganese-based metal oxide and has a first crystal phase having a two-dimensional crystal structure and a second crystal phase having a three-dimensional crystal structure, wherein the three-dimensional crystal structure is formed by the combination of manganese in the manganese-based metal oxide and oxygen in the crystal water.