Synthesis of polyhedral MoS2@C hollow cages using a sacrificial template approach for improved reversible lithium storage

Abstract

Hierarchical polyhedral MoS₂@C (HP-MoS₂@C) hollow cages are controllably constructed using the K₂NaMoO₃F₃ precursors as self-sacrificed templates. As an anode for lithium-ion batteries, HP-MoS₂@C cages deliver a reversible capacity of 1092.9 mA h g⁻¹ at 2 A g⁻¹ after 1000 cycles. The excellent performance of HP-MoS₂@C can be mainly attributed to its hierarchical structure and the synergistic effect between MoS₂ and carbon. Beneficially, the robust carbon framework in MoS₂@C composites not only facilitates electron transfer among MoS₂ particles but also alleviates the large volume expansion of MoS₂ during the charging and discharging processes. Due to the difference in work function, a built-in electric field forms at the MoS₂/C interface, which facilitates Li-ion transfer across the heterojunction interface. Density functional theory calculations reveal that the expanded interlayer space of MoS₂, due to carbon insertion, reduces the energy barrier and is consequently beneficial for the insertion and removal of Li-ions during the electrode reaction. The local defects in the MoS₂ lattice due to carbon doping could also facilitate electron migration and Li-ion diffusion in the MoS₂ layer based on bound polarons theory. Moreover, HP-MoS₂@C‖LiCoO₂ Li-ion pouch cells are successfully assembled and deliver good lithium storage capacity, indicating promising applications in high energy-density Li-ion batteries.