To increase the reversible capacity of layered lithium nickel-cobalt-manganese oxide, a Li Ni0.8Co0.06Mn0.14O-2 positive electrode with a two-sloped full concentration gradient (TSFCG) was successfully synthesized via co-precipitation. The TSFCG maximizes the Ni concentration in the particle core and the Mn concentration on the particle surface. The TSFCG LiNi0.8Co0.06Mn0.14O-2 positive electrode showed improved overall electrochemical properties (i.e., reversible capacity, cycle life, and rate capability) and thermal stability compared to a conventional positive electrode (CC) Li Ni0.8Co0.06Mn0.14O-2 without a concentration gradient. Electrochemical impedance spectroscopy showed that the high stability of the outer surface composition of LiNi0.64Co0.06Mn0.30O-2 is responsible for reduction in surface resistance and charge transfer resistance by decreasing the parasitic reaction with the electrolyte. These reduced resistances explain the superior rate capability of TSFCG positive electrodes.
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