Boosting cyclability performance of GeP anode via in-situ generation of free expansion volume

Among the germanium-based composites, germanium phosphide (GeP) is a promising anode material for lithium-ion batteries (LiBs) because of its good electronic conductivity, low binding energy and high theoretical energy density. Nevertheless, the severe volume variation and sluggish reaction kinetics hindered its applications. To solve the above issues, this work come up with a killer idea that inspired by the free volume theory of polymers, which was mainly involved creation of free volume into GeP matrix. Specifically, structural design that elaborately deals with severe aggregation while helps alleviating volume expansion and contraction of GeP have being made by a facile ball milling-assisted in-situ generation of free expansion volume. Compared with pristine GeP and direct ball milled GeP, the addition of NaCl as grinding agent plays a very positive role on generating free volume space in flake-like GeP particles, which was assembled by numerous amorphous GeP granules. In this way, the as obtained GeP particles exhibited enhanced reversible capacity, improved cyclability and rate performance (883 mAh g−1 at 0.2 C after 100th cycle, and 680 mAh g−1 at 2 C) when served as anode material in LiBs. This study highlights a highly efficient and cost effective approach in advancing the high performance GeP towards practical applications for energy storage.