Structural and electrical properties of LiCoO2 thin-film cathodes deposited on planar and trench structures by liquid-delivery metalorganic chemical vapour deposition

The electrochemical properties of annealed-LiCoO2 cathodes deposited on planar and trench structures by liquid-delivery metalorganic chemical vapor deposition are investigated for various deposition temperatures and input Li:Co mole ratios. With the planar structure, the best crystallinity of the films is obtained at a deposition temperature of 450 °C and an input Li:Co mole ratio of 1.0. The deposition window for optimum initial discharge capacity and capacity retention is a deposition temperature of 450–500 °C and an input Li:Co mole ratio of 1.0, and an input Li:Co mole ratio of 1.0–1.2 at a deposition temperature of 450 °C. The initial discharge capacity and capacity retention of LiCoO2 thin films deposited with an input Li:Co mole ratio of 1.2 at 450 °C are approximately 25 μAh/cm2 μm and 77%, respectively. The initial discharge capacity of films deposited on a trench structure shows an increase of approximately 130% compared with that of films deposited on a planar structure with an input Li:Co mole ratio of 1.2. The rechargeabilities of films deposited in a trench structure are inferior to those in a planar structure because conformal growth in the trench structure is poor. Thus, a trench structure can improve the initial discharge capacity and capacity retention of lithium microbatteries.