Sn doped lithium nickel cobalt manganese composite oxide of LiNi3/8Co2/8Mn3/8−x Sn x O2 (0≤ x ≤0.10) was synthesized by stannum substitute of manganese to enhance its rate capability at first time. Its structure and electrochemical properties were characterized by X-ray diffraction (XRD), SEM, cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) and charge/discharge tests. LiNi3/8Co2/8Mn3/8−x Sn x O2 had stable layered structure with α-NaFeO2 type as x up to 0.05, meanwhile, its chemical diffusion coefficient D Li of Li-ion was enhanced by almost one order of magnitude, leading to notable improvement of the rate capability of LiNi3/8Co2/8Mn3/8O2. The compound of x =0.10 showed the best rate capability among Sn doped samples, but its discharge capacity reduced markedly due to secondary phase Li2SnO3 and increase of cation-disorder. The compound with x =0.05 showed high rate capability with initial discharge capacity in excess of 156mAhg−1. It is a promising alternative cathode material for EV application of Li-ion batteries.