LiNi0.5Mn0.4M0.1O2 (M =Li, Mg, Al, Co) compound was prepared by a solid-state reaction, and its structural, morphological and electrochemical properties were characterized by XRD, SEM, charge-discharge tests and EIS. The impacts of alien ion introduction on the structural, morphological and electrochemical properties of LiNi0.5Mn0.5O2 depend on the dopants. The substitution of Li, Mg, and Co for Mn can enlarge the particle size and improve the crystallinity. LiNi0.5Mn0.4Li0.1O2 and LiNi0.5Mn0.4Co0.1O2 show increased reversible capacities as well as upgraded rate capabilities. LiNi0.5Mn0.4Li0.1O2 exhibits a retentive capacity of about 200 mAh g(-1) at 50 degrees C. (c) 2005 Elsevier B.V. All rights reserved.