CATHODE OPTIMIZED FOR IMPROVING HIGH-TEMPERATURE LIFESPAN CHARACTERISTICS, AND SECONDARY BATTERY COMPRISING SAME

The present disclosure provides a positive electrode in which a positive electrode mixture containing a positive electrode active material is formed on a positive electrode current collector, wherein the positive electrode active material includes a lithium transition metal oxide powder represented by the following chemical formula 1, LiNiCoMOA (1) wherein, M is at least one selected from the group consisting of Mn, Ti, Mg, Al, Zr, Mn and Ni, A is an oxygen-substituted halogen, and 1.00≤a≤1.05, 0.1≤x≤0.8, 0.1≤y≤0.8, 0.01≤z≤0.4, and 0≤w≤0.001, wherein the lithium transition metal oxide powder is composed of: large particles in which secondary particles are formed by aggregating primary particles, and an average particle diameter (D50) of the secondary particles is 7 µm to 17 µm, and small particles in which single particles are formed and having average particle diameter (D50) of 2 µm to 7 µm, wherein a mixing ratio of the large particles and the small particles is 5:5 to 9:1 based on the weight, and wherein the positive electrode mixture has a porosity of 22% to 35%.