Electrochemical Properties of Nonstoichiometric LiNi[sub 0.5]Mn[sub 1.5]O[sub 4−δ] Thin-Film Electrodes Prepared by Pulsed Laser Deposition

Well-crystallized nonstoichiometric thin-film electrodes were prepared by pulsed laser deposition (PLD). The charge/discharge behavior of the nonstoichiometric thin film is consistent with the film having a disordered spinel structure with space group . These thin-film electrodes exhibit excellent cycle performance and rate capability. The measured Li diffusivity in the film is in the range of to , which is comparable to that of layered . First principles calculations on the stoichiometric (ordered) spinel find no intermediate ordered phases between and , leading us to speculate that voltage steps observed in experiments are caused by disorder, which facilitates Li/vacancy ordering. The presence of a smaller step in "ordered" than in disordered is consistent with the calculation and may indicate presence of partial disorder even in ordered material. Although a maximum was found for the chemical diffusion coefficient of Li in near , the self-diffusion coefficient exhibits a minimum at that composition.