Electrochemical investigation of LiNi0.5Mn1.5O4 thin film intercalation electrodes

This work provides kinetic and transport parameters of Li-ion during its extraction/insertion into thin film LiNi0.5Mn1.5O4 free of binder and conductive additive. Thin films of LiNi0.5Mn1.5O4 (0.2 mum thick) were prepared on electronically conductive gold substrate utilizing the electrostatic spray deposition technique. High purity LiNi0.5Mn1.5O4 thin film electrodes were observed with cyclic voltammetry, to exhibit very sharp peaks, high reversibility, and absence of the 4 V signal related to the Mn3+/Mn4+ redox couple. The electrode subjected to 100 CV cycles of charge/discharge delivered a capacity of 155 mAh g(-1) on the first cycle and sustained a good cycling behavior while retaining 91% of the initial capacity after 50 cycles. Kinetics and mass-transport of Li-ion extraction at LiNi0.5Mn1.5O4 thin film electrode were investigated by means of electrochemical impedance spectroscopy. The apparent chemical diffusion coefficient (D-app) value determined from EIS measurements changed depending on the electrode potential in the range of 10(-10)-10(-12) cm(2) s(-1). The D-app profile shows two minimums at the potential values close to the peak potentials of the corresponding cyclic voltammogram. (C) 2002 Elsevier Science Ltd. All rights reserved.