Growth and characterization of tetravalent doped LiCoO₂thin film cathodes

Abstract

Titanium-doped LiCoO₂thin films are grown by pulsed laser deposition technique on silicon substrates. Structure, AFM, FTIR and Raman are studied with respect to their deposition parameters, i.e., substrate temperature (<i style="">T</i>_s) and oxygen partial pressure (pO₂) in the deposition chamber. The films deposited in pO₂ = 100 mTorr showed good crystallinity on silicon substrates maintained at <i style="">T</i>_s = 700°C. It is found that such a film crystallizes in the layered <img src='/image/spc_char/alpha.gif'>-NaFeO₂ structure. The influence of titaniumdoping on particle size and morphologies has been clearly studied. FTIR spectra displayed the characteristic IR dominant bands at 246 and 550 cm^–1for titanium doped LiCoO₂thin films. The Raman peaks observed for the films at 594 cm^-1 and 485 cm^-1 are ascribed to Raman active modes A_1g and E_g respectively. The electrochemical measurements were carried out on Li//LiTi_yCo_1-yO₂ cells. The Li//LiTi_yCo_1-yO₂ cell delivered a specific capacity of 225 mC/<img src='/image/spc_char/micro.gif'>m cm². The influence of titaniumdoping on the structural and electrochemical properties has been systematically studied.