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

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 Im 3̅ m 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 Im 3̅ m Sn. These findings provide strong evidence for the conversion reaction mechanism, supported by ex situ 119 Sn Mössbauer spectroscopy, offering deeper insights into the electrochemical properties of SnS-based materials in KIBs.