Abstract
The compound LiCoBO3 is an appealing candidate for next generation Li-ion
batteries based on its high theoretical specific capacity of 215 mAh/g and high expected
discharge voltage (more than 4 V vs. Li+/Li). However, this level of performance has not yet
been realized in experimental cells, even with nanosized particles. Reactive magnetron
sputtering was therefore used to prepare thin films of LiCoBO3, allowing the influence of
particle thickness on electrochemical performance to be explicitly tested. Even when ultra-thin
films (~15 nm) were prepared, there was a negligible electrochemical response from LiCoBO3.
Impedance spectroscopy measurements suggest that the conductivity of LiCoBO3 is many orders
of magnitude worse than that of LiFeBO3, and may be severely limiting performance. The band
gap and unusual blue color of LiCoBO3 were investigated by spectroscopic techniques, which
allowed the determination of an optical gap of 4.2 eV and the assignment of the visible light
absorption to a symmetry-allowed eā ā aā transition that occurs within the context of a
particularly simple electronic configuration.
