Electronic structure of lithium borocarbide as a cathode material for a rechargeable Li-ion battery: First-principles calculation

Traditional cathode materials, such as transition-metal oxides, are heavy, expensive, and often not benign. Therefore, alternative materials without transition metal elements are highly desirable in order to design high-capacity Li-ion batteries of light weight and low price. Here we report on potential application of the LiBC compound as cathode materials, in which graphene-like BC sheets are intercalated by Li ions. The crystal structure and properties of LiBC were firstly reported by W\"{o}rle et al. in 1995. Importantly, it was found that the 75{\%} Li ions can be retrieved out of the compound without changing the layered structure. We have performed first-principles calculations based on density functional theory, as implemented in the Vienna Ab-initio Simulation Package. According to our calculation, the layered Li$_{x}$BC structure can be well preserved at x $>$ 0.5. The reversible electrochemical reaction, LiBC $\leftrightarrow $ Li$_{0.5}$BC + 0.5Li, gives an energy capacity of 609mAh/g and an open-circuit voltage of 2.42V. The volume change is only about 5{\%} during the charging and discharging process. All these results point to a potentially promising application of LiBC as a novel cathode material for high-capacity Li-ion batteries in replacement of the transition metal oxides.