Unfolding the potassium storage mechanism of tin selenides

Tin selenides have attracted great attention as anode materials for alkali metal ion batteries in recent years because of the high theoretical capacity. However, there is currently few literatures on the application of tin selenides in potassium ion battery, and the comparative research on the actual potassium storage mechanism of different tin selenides is rarely reported. Herein, tin selenides including SnSe2@C and SnSe@C are synthesized by regulating the selenization temperature, and their potassium storage performance and the mechanism have been comparatively investigated with various physicochemical techniques as well as operando synchrotron X-ray diffraction (SXRD) and density functional theory (DFT) calculations. It is revealed that the better potassium storage performance of SnSe2@C is mainly due to the generation of highly conductive Se during the first depotassiation process, which not only participates in the subsequent potassiation/depotassiation process, but also improves the conductivity of electrode and facilitates the kinetics of K+. While the sluggish kinetics and partial irreversible decomposition of KxSe lead to the inferior potassium storage performance of SnSe@C.