Improving the performance of a SnS2 cathode with interspace layer engineering using a Na+ insertion/extraction method for aqueous zinc ion batteries

Abstract

Layered materials are promising as cathodes for aqueous zinc-ion batteries (AZIBs) due to the reduced complexity of 2D Zn²⁺ transport channels. Nevertheless, their weak cycle stability or limited capacity restricts their practical usage. We attempted to evolve a SnS₂ cathode synthesized by a simple hydrothermal procedure for 0.86 nm-spaced ZIBs for the first time. We precisely monitored the Na ion insertion and extraction in a layered structure of SnS₂ dominated by van der Waals interactions, leading to considerably high interspace layers SnS₂ (SnS₂-HIL) from 0.86 to 1.10 nm. It enables higher Zn²⁺ storage capacity in SnS₂-HIL cathodes. The SnS₂-HIL has an exceptionally high-rate performance and stable cycling over time, with 359 mA h g⁻¹ at 0.1 A g⁻¹ and 174 mA h g⁻¹ at 10 A g⁻¹, along with 83.7% of capacity maintained after 1000 cycles. Electrochemical investigations indicated improved Zn²⁺ migration kinetics and excellent pseudocapacitive behaviors. An ex situ study showed that a reversible phase change between Sn²⁺ and Sn⁴⁺ occurred after an energy-storing mechanism brought about by Zn ion insertion/extraction. This study opens up an exciting new opportunity for developing and optimizing 2D materials as high-performance cathodes for AZIBs.