To increase the reversible capacity of layered lithium nickel-cobalt-manganese oxide, a Li [Ni_0.8Co_0.06Mn_0.14]O₂ 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 Li[Ni_0.8Co_0.06Mn_0.14]O₂ 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 [Ni_0.8Co_0.06Mn_0.14]O₂ without a concentration gradient. Electrochemical impedance spectroscopy showed that the high stability of the outer surface composition of Li[Ni_0.64Co_0.06Mn_0.30]O₂ 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.