Polyantimonides as anode materials in battery applications

Antimony containing compounds have drawn interest as anode materials in Li batteries due to their high Li packing density and the resulting volumetric charge density. Reasonable specific capacities outperforming graphite by a factor of 2 have been reported for antimonides and polyantimonides. Together with good cycling stabilities, rate capabilities and a high potential level against Li metal, both classes of materials are discussed as potential candidates to substitute carbonaceous hosts. Unfortunately, severe volume expansion during the reaction with lithium takes place which has to be taken into account during optimization of the systems. This feature demands size tailoring and electrode optimization to push the electrochemical performance and the lifetime of half cells and full batteries in applicable dimensions. While antimonides are more or less intermetallic compounds, performing a conversion reaction to electrochemical active (in most cases Sb) and non-active species, polyantimonides can offer a greater flexibility due to their anisotropic structural features. Polyantimonides, containing simple dumbbells up to layered arrangements of covalently bonded antimony, can provide voids or interstitials for insertion and intercalation of lithium. The chance to preserve such favourable structural features during this process is in principle higher than for antimonides where conversion reactions to other species take place.