Zinc tin sulfide enhanced by graphene nanosheets and carbon nanotubes for high-performance sodium storage

ZnSnS₃ features abundant redox reactions and remarkable theoretical capacity, rendering it a promising negative electrode material for SIBs. However, it faces challenges associated with significant volume expansion and poor electrical conductivity. In our work, using a straightforward two-step method, we designed ZSS@GC, a composite that combines ZnSnS₃ with a carbon framework composed of graphene nanosheets (GNs) and carbon nanotubes (CNTs). The ZSS@GC electrode can deliver an exceptional reversible specific capacity of 642.0 mAh·g⁻¹ at 0.5 A·g⁻¹, as well as an excellent rate performance of 434.4 mAh·g⁻¹ at 5.0 A·g⁻¹. Additionally, it exhibits a noteworthy long-term cycle stability of 500 cycles at 10 A·g⁻¹. Electrochemical kinetic studies reveal that the introduction of GC significantly enhances the pseudocapacitive contribution, a key factor responsible for the excellent rate performance of ZSS@GC. Moreover, GC reduces charge transfer impedance and increases the Na⁺ diffusion coefficient of ZSS, resulting in fast electron/ion transport. CV test and ex situ XRD analysis elucidate the “intercalation-conversion-alloying” sodium storage mechanism. Moreover, competitive performance is observed when assembled as a full cell with Na₃V₂(PO₄)₃/C, indicating that ZSS@GC holds considerable potential for application in practical energy storage. Our work offers valuable insights for the development of high-performance conversion-type SIBs negative electrode materials.