In situ carbon encapsulation of vertical MoS2 arrays with SnO2 for durable high rate lithium storage: dominant pseudocapacitive behavior

Abstract

Improving the conductivity and charge transfer kinetics is favourable for innovation of sustainable energy devices such as metal oxide/sulfide-based electrodes. Herein, with an intercalation pseudocapacitance effect, an in situ polymerization–carbonization process for novel carbon-sealed vertical MoS₂–SnO₂ anchored on graphene aerogel (C@MoS₂–SnO₂@Gr) has enabled excellent rate performance and durability of the anode of lithium ion batteries to be achieved. The integrated carbon layer and graphene matrix provide a bicontinuous conductive network for efficient electron/ion diffusion pathways. The charge transfer kinetics could be enhanced by the synergistic effects between vertical MoS₂ nanosheets and well-dispersed SnO₂ particles. Based on the crystal surface matching, the ameliorated electric contact between MoS₂ and SnO₂ can promote the extraction of Li⁺ from Li₂O and restrain the serious aggregation of Li_xSn. As a result, the improved reversibility leads to a higher initial coulombic efficiency (ICE) of 80% (0.1 A g⁻¹ current density) compared to that of other materials. In particular, with the dominating surface capacitive process, the C@MoS₂–SnO₂@Gr electrode delivers a stable capacity of 680 mA h g⁻¹ at 2.5 A g⁻¹ for 2000 cycles. Quantitative insight into the origin of the boosted kinetics demonstrated the high pseudocapacitance contribution (above 90%) which leads to the durable high rate Li ion storage.