Unraveling the stabilization mechanism of solid electrolyte interface on ZnSe by rGO in sodium ion battery

Abstract Transition metal selenides have been widely studied as anode materials of sodium ion batteries (SIBs), however, the investigation of solid-electrolyte-interface (SEI) on these materials, which is critical to the electrochemical performance of SIBs, remains at its infancy. Here in this paper, ZnSe@C nanoparticles were prepared from ZIF-8 and the SEI layers on these electrodes with and without reduced graphene oxide (rGO) layers were examined in details by X-ray photoelectron spectroscopies at varied charged/discharged states. It is observed that fast and complicated electrolyte decomposition reactions on ZnSe@C leads to quite thick SEI film and intercalation of solvated sodium ions through such thick SEI film results in slow ion diffusion kinetics and unstable electrode structure. However, the presence of rGO could efficiently suppress the decomposition of electrolyte, thus thin and stable SEI film was formed. ZnSe@C electrodes wrapped by rGO demonstrates enhanced interfacial charge transfer kinetics and high electrochemical performance, a capacity retention of 96.4%, after 1000 cycles at 5 A/g. This study might offer a simple avenue for the designing high performance anode materials through manipulation of SEI film.