Layered titanium disilicide stabilized by oxide coating for highly reversible lithium insertion and extraction

摘要

The discovery of new materials has played an important role in battery technology development. Among the newly discovered materials, those with layered structures are of ten of particular interest because many have been found to permit highly repeatable ionic insertion and extraction. Examples include graphite and LiCoO _2 as anode and cathode materials, respectively. Here we report C49 titanium disilicide (TiSi _2) as a new layered anode material, within which lithium ions can react with the Si-only layers. This result is enabled by the strategy of coating a thin (<5 nm) layer of oxide on the surface of TiSi _2. This coating helped us rule out the possibility that the measured capacity is due to surface reactions. It also stabilizes TiSi _2 to allow for the direct observation of TiSi _2 in its lithiated and delithiated states. In addition, this stabilization significantly improved the charge and discharge performance of TiSi _2. The confirmation that the lithium-ion storage capacity of TiSi _2 is a result of its layered structure is expected to have major fundamental and practical implications.