Study on Li+-ion diffusion in nano-crystalline LiMn2O4 thin film cathode grown by pulsed laser deposition using CV, EIS and PITT techniques

In the present work, LiMn2O4 thin films have been prepared by pulsed laser deposition on stainless steel substrates. The films deposited at 400 °C and 200 mTorr of oxygen were mainly composed of nano-crystals less than 100 nm and their agglomerates. Three different electrochemical methods including CV, EIS and PITT were applied to measure the overall Li+-ion diffusion coefficients and charge-transfer resistances at various potentials from 3.85 to 4.5 V. The Li+ diffusion coefficients were in the range of 10−12 to 10−10 cm2 s−1, depending on the potentials. It was found that the charge-transfer resistances decreased with the increase of potentials. Especially, relatively high diffusion coefficients and low charge-transfer resistances were observed above 4.2 V.