A freestanding NiSx porous film as a binder-free electrode for Mg-ion batteries.

An ultrathin, freestanding NiSx nanoporous thin-film was developed by facile electrochemical deposition, etching, anodization and chemical vapor treatments. The NiSx nanoporous thin-film shows excellent reversible insertion/extraction of Mg ions and long-term cycling performance, which is an ideal energy storage device for small/micro-size electronic and medical devices.