Characterization of LiCoO2 thin film cathodes deposited by liquid-delivery metallorganic chemical vapor deposition for rechargeable lithium batteries

LiCoO2 thin film cathodes were successfully deposited onto Pt/Ti/SiO2/Si substrates by liquid-delivery metallorganic chemical vapor deposition. LiCoO2 thin films were crystallized even at temperatures as low as 270degreesC, and the deposition reaction was controlled by gas-phase mass transfer and chemical kinetics above and below 300degreesC, respectively. The electrochemical properties of LiCoO2 films are greatly dependent on the deposition temperature and Li/Co mole ratio. The films as-deposited at 400degreesC showed the moderate initial discharge capacities for various Li/Co input mole ratios. However, rechargeabilities are completely lost after cyclic tests of 60 cycles regardless of Li/Co mole ratios. Thin films as-deposited at 450degreesC with Li/Co = 0.8 showed a maximum discharge capacity of 34 mu Ah/cm(2) mm and capacity retention of 64% after a cyclic test of 100 cycles. The samples annealed at 700degreesC for 30 min in an oxygen ambient showed a capacity retention of approximately 75%, compared with samples as-deposited at 450degreesC. (C) 2002 The Electrochemical Society.