Highly effective solid electrolyte interface on SnO2@C enabling stable potassium storage performance

Abstract

The property of solid electrolyte interface (SEI), which is related to the nature of electrolyte, directly affects the electrochemical performance of electrode materials in potassium ion battery. In this work, the potassium storage performance of a composite SnO2@C was studied in two different electrolytes of 0.8 M KPF6/EC + DEC (KPF-ED) and 3 M KFSI/DME (KFSI-DME), and its correlation with the generation and properties of SEI film was explored and analyzed based on physicochemical characterizations and density functional theory (DFT) calculations. It was revealed that the superior potassium storage performance of SnO2@C when coupled with KFSI-DME electrolyte was originated from the thin inorganic-rich SEI film generated mainly from decomposition of KFSI salt, which could diminish internal resistance, promote charge transfer and improve electrolyte stability in PIB. While the thick organic SEI film formed in KPF-ED electrolyte was derived mainly from decomposition of the solvents, its continuous generation led to increasing electrolyte consumption and difficult charge transfer, resulting in poor potassium storage performance of SnO2/C as anode material. This work offers a valuable guidance to the construction of robust and stable SEI film by optimizing the electrolyte composition to boost potassium storage performance of electrode materials.