Li diffusion in LiNi 0.5Mn 0.5O 2 thin film electrodes prepared by pulsed laser deposition

Abstract

Kinetic and transport parameters of Li ion during its extraction/insertion into thin film LiNi 0.5Mn 0.5O 2 free of binder and conductive additive were provided in this work. LiNi 0.5Mn 0.5O 2 thin film electrodes were grown on Au substrates by pulsed laser deposition (PLD) and post-annealed. The annealed films exhibit a pure layered phase with a high degree of crystallinity. Surface morphology and thin film thickness were investigated by field emission scanning electron microscopy (FESEM). The charge/discharge behavior and rate capability of the thin film electrodes were investigated on Li/LiNi 0.5Mn 0.5O 2 cells at different current densities. The kinetics of Li diffusion in these thin film electrodes were investigated by cyclic voltammetry (CV) and galvanostatic intermittent titration technique (GITT). CV was measured between 2.5 and 4.5 V at different scan rates from 0.1 to 2 mV/s. The apparent chemical diffusion coefficients of Li in the thin film electrode were calculated to be 3.13 × 10 −13 cm 2/s for Li intercalation and 7.44 × 10 −14 cm 2/s for Li deintercalation. The chemical diffusion coefficients of Li in the thin film electrode were determined to be in the range of 10 −12–10 −16 cm 2/s at different cell potentials by GITT. It is found that the Li diffusivity is highly dependent on the cell potential.