Growth of HT-LiCoO2 thin films on Pt-metalized silicon substrates

Layered LiCoO₂ (HT-LiCoO₂) films were grown on Pt-metalized silicon (PMS) substrates and polished bulk nickel (PBN) substrates by pulsed laser deposition. The effects of substrate temperature, oxygen pressure, and substrate surface roughness on the microstructure of LiCoO₂ films were investigated. It has been found that a higher substrate temperature and a higher oxygen pressure favor the formation of better crystallized and less lithium-deficient HT-LiCoO₂ films. The HT-LiCoO₂ film deposited on PBN substrates consists of large randomly orientated equiaxial grains, whereas on PMS substrate, it is made up of loosely packed highly [00l] preferential orientated triangular shaped grains with the average grain size less than 100 nm. Electrochemical measurements show that the highly [00l] preferentially orientated nanostructured HT-LiCoO₂ thin film grown on PMS substrate has good structural stability upon lithium insertion/extraction and can deliver an initial discharge capacity of approximately 45 μA·h·cm⁻²·μm⁻¹ with a cycling efficiency of above 99% at the charge/discharge rate of 0.5 C.