Li diffusion in spinel LiNi0.5Mn1.5O4 thin films prepared by pulsed laser deposition

Spinel LiNi0.5Mn1.5O4 thin film electrodes of 0.5 mu m thickness were prepared on polished stainless steel (SS) substrates by pulsed laser deposition. Kinetics and mass-transport of Li intercalation/deintercalation were investigated by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and potentiostatic intermittent titration technique (PITT). The CV measurements indicate that there exists a small amount of Mn3+ in the film and Li transportation is controlled by diffusion at high scan rates. EIS measurements show a potential independent low charge-transfer resistance region between 4.1 and 4.7V and a stable surface layer resistance through the full potential range. The chemical diffusion coefficients of Li in the LiNi0.5Mn1.5O4 thin film obtained by EIS and PITT have been found to be in the range of 10(-12) - 10(-10) cm(2) s(-1) depending on the electrode potential. Two minima were found for (D) over tilde (Li) from PITT at potentials close to the peak potentials of the corresponding CV.