Enhanced reversible reaction of hexagonal SnS2@rGO as anode materials for lithium-ion batteries: Analysis of the morphological change mechanism

Abstract

Tin-based materials have attracted attention as a promising anode material for lithium-ion batteries due to their high theoretical capacity and alloy metal characteristics. However, the structure tends to easily collapse with repetitive charging and discharging processes, leading to volume expansion. The conversion step in the SnS2 reaction mechanism is also sometimes considered irreversible. To address these challenges, this study synthesized layered hexagonal 2D structure-type SnS2 using the oleylamine as surfactant through a wet chemical process. Subsequently, SnS2@rGO was synthesized after compounding with reduced graphene oxide (rGO), utilizing a smaller amount of nanomaterials compared to rGO, showing optimal efficiency. The morphological changes in SnS2 and SnS2@rGO during the charging and discharging processes was revealed that pulverization occurred more slowly in SnS2@rGO compared to SnS2. We quantified the volume expansion rates of SnS2 and SnS2@rGO electrodes, demonstrating that rGO effectively reduces volume expansion. Additionally, an analysis of lithiation mechanism through a comprehensive analysis method using CV, ex-situ XRD, and ex-situ TEM demonstrated that SnS2@rGO enhanced Li+ storage characteristics compared to SnS2, resulting in more reversible chemical changes. rGO and bare SnS2 show poor capacities 307.23 mAh/g and 87.17 mAh/g after 120 cycles, respectively. However bare SnS2 anchored on the surface of rGO exhibits increased electrical conductivity and improved performance (711 mAh/g after 120 cycles), confirming that rGO plays an important role. SnS2@rGO showed enhanced cycling stability and discharge capacity as shown in the electrochemical testing. © 2024 The Authors