Electrochemical performance of lithium ion batteries is associated with structural and chemical stability of electrode materials. Lithium transition-metal oxides has been considered as promising cathode materials for Li ion batteries. [1] LiNi x Co y Mn z O 2 (NCM) is one candidate for next outstanding cathode materials due to its high capacity and cost effectiveness compared with LiCoO 2 . However, as the fraction of nickel rises to enhance the charge/discharge capacity, especially LiNi 0.6 Co

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... 0.2 Mn 0.2 O 2 , cation mixing, which results from the migration of transition metal ions into vacant lithium sites, is accelerated owing to similar ionic radii between nickel and lithium. [2] It leads to lattice distortion and collapse of layered structure and results in capacity fading and poor cycleability and has a difficulty in commercialization despite of its high capacity. However, the inevitable lattice distortions and chemical evolution have not been investigated intensely. 1336