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

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 LixSn. 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.