Electrochemical Performance of Ti- and Zr-Doped LiCoO 2 Film Cathodes Prepared By Rf-Magnetron Sputtering for Lithium Microbatteries

In an attempt to enhance the microstructural and electrochemical (EC) properties, LiCoO 2 thin films were doped with titanium or zirconium. RF magnetron sputtering technique has been employed for the deposition of films on Au/Ti/SiO 2 /Si substrates from lithium-rich LiCoO 2 target with mosaic configuration. The as-deposited and Ti- and Zr-doped LiCoO 2 thin films at lower doping concentration exhibited the α-NaFeO 2 structure with R-3 m symmetry as confirm from X-ray diffraction and Raman studies. The cyclic voltammogram of micro-electrodes in aqueous electrolyte exhibited perfect redox peaks with good reversibility. The chronopotentiometry studies revealed that the discharge capacity of pure LiCoO 2 was 64 µAh cm -2 µm -1 , while 2% Ti- and Zr-doped films showed enhanced capacities 69 and 68 µAh cm -2 µm -1 (248 mC cm -2 µm -1 , 245 mC cm -2 µm -1 ) respectively. The Zr-doped films exhibited good structural stability even after 25 cycles with the capacity retention of 95%. The kinetics of lithium ions in pure and Ti/Zr-doped LiCoO 2 thin film cathodes and their cycleability are studied using both aqueous Pt//LiCoO 2 and and non-aqueous Li//LiCoO 2 cells and the results will be presented.