Mechanistic Insights and Electrochemical Performance of Microwave-Synthesized SnS for K-Ion Batteries

Abstract

K-ion batteries (KIBs) emerge as a promising alternative to Li-ion batteries. However, identifying suitable anodes for K-ion storage remains a challenge. SnS stands out due to its layered structure and advantageous conversion and alloying reaction mechanism. This work explores the microwave-assisted hydrothermal synthesis of SnS at different reaction times. As the synthesis time decreases, morphology evolves from platelets (2 h) to granular agglomerates (1 min), producing a centered superstructure in the 1 min material. To evaluate SnS as KIBs electrode, composites were prepared by adding different amounts of C65 and few-layer graphene into SnS synthesized at 1 min and 2 h. The best performance was achieved for SnS synthesized in 1 min with 24% C65 and 1% few-layer graphene, delivering a reversible capacity of 285 mAh/g at C/20. An operando powder X-ray diffraction (XRD) study revealed the possible formation of Sn with Im3̅m space group, predicted to form under high-pressure conditions. Ex situ XRD shown the presence of crystalline α-Sn and SnS, with additional reflections that are consistent with Im3̅m Sn. These findings provide strong evidence for the conversion reaction mechanism, supported by ex situ 119Sn Mössbauer spectroscopy, offering deeper insights into the electrochemical properties of SnS-based materials in KIBs.