Enhanced reversible reaction of hexagonal SnS2@rGO as anode materials for lithium-ion batteries: Analysis of the morphological change mechanism
Hyerin Yoo, Joon Ha Moon, Honggyu Seong, Youngho Jin, Geongil Kim, Taejung Jung, Jin Bae Lee, Seung‐Ryong Kwon, Min Yang, Jaewon Choi
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 SnS 2 reaction mechanism is also sometimes considered irreversible. To address these challenges, this study synthesized layered hexagonal 2D structure-type SnS 2 using the oleylamine as surfactant through a wet chemical process. Subsequently, SnS 2 @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 SnS 2 and SnS 2 @rGO during the charging and discharging processes was revealed that pulverization occurred more slowly in SnS 2 @rGO compared to SnS 2 . We quantified the volume expansion rates of SnS 2 and SnS 2 @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 SnS 2 @rGO enhanced Li + storage characteristics compared to SnS 2 , resulting in more reversible chemical changes. rGO and bare SnS 2 show poor capacities 307.23 mAh/g and 87.17 mAh/g after 120 cycles, respectively. However bare SnS 2 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. SnS 2 @rGO showed enhanced cycling stability and discharge capacity as shown in the electrochemical testing. • Hexagonal 2D structure-type of SnS 2 were synthesized composite with rGO. • The morphology changes of SnS 2 and SnS 2 @rGO are described in detail. • The Li + storage mechanism of SnS 2 and SnS 2 @rGO was analyzed. • The SnS 2 @rGO showed a higher discharge capacity than SnS 2 .