Lithiation and Delithiation Reactions of Binary Silicide Electrodes in an Ionic Liquid Electrolyte as Novel Anodes for Lithium‐Ion Batteries

We investigated the lithiation and delithiation properties of pure binary silicide electrodes in an ionic liquid electrolyte as novel anodes for lithium‐ion batteries. Some electrodes maintain a high reversible capacity in the electrolyte, whereas they show a poor cycling performance in an organic electrolyte. The superior performance results from the high affinity for the transition metal that composes the silicide with Li. Based on reaction behavior analysis, the crystal structure of silicide is maintained during the cycling, and phase separation does not occur. The ionic liquid electrolyte suppresses the formation of cracks and exfoliation of the silicide layer from a substrate. In addition, a surface film formed on the silicide electrode through the reductive decomposition of the electrolyte has different components than that on a Si electrode, even in the same ionic liquid electrolyte. Soft X‐ray emission spectroscopy demonstrates that the pure silicide itself reacts with Li. The obtained results will provide significant insights into novel alloy‐based anode materials for lithium‐ion batteries.