Li(Ni1/4Mn1/2Co1/3)O-2 thin-film electrodes have been successfully fabricated by magnetron sputtering. The electrochemical behaviors of thin-film electrodes have been investigated in liquid and solid electrolytes. The reversible capacity of Li(Ni1/4Mn1/2Co1/3)O-2 is found to be above 30 mu Ah/cm(2) mu m in all-solid-state thin-film batteries cycled between 5.0 and 3.0 V. The diffusion constants of Li ion are calculated to be 1.62 x 10(-13) and 1.78 x 10(-13) cm(2)/s for deinsertion and insertion at ambient temperature, respectively. Our results demonstrated that the Li(Ni1/4Mn1/2Co1/3)O-2 film electrode could be selected as one of the promising candidates for all-solid-state thin-film rechargeable lithium batteries. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3432254] All rights reserved.