SiO2@MoS2 core–shell nanocomposite layers with high lithium ion diffusion as a triple polysulfide shield for high performance lithium–sulfur batteries

Abstract

This study introduces an improved design of interlayers to achieve a balance between high Li⁺ diffusion and polysulfide inhibition in lithium–sulfur batteries. The design involves encapsulating mesoporous SiO₂ nanospheres in few-layer MoS₂ nanosheets via a facile one-step self-assembly to form a core–shell nanocomposite (SiO₂@MoS₂). The SiO₂@MoS₂ layer overlaid on a sulfur cathode simultaneously intercepts polysulfides and ensures rapid Li⁺ diffusion. Few-layer MoS₂ as the shell is capable of breaking up polysulfides by a catalytic reaction, while mesoporous SiO₂ as the core allows for physiochemical adsorption of such species; moreover, the densely packed hermetic SiO₂@MoS₂ nanocomposite layer provides an additional physical shield against polysulfide diffusion, realizing the full protection of the whole cathode. At the same time, the high Li⁺ density in the nanolayered MoS₂ shell and the additional Li⁺ pathways created by the mesoporous SiO₂ core allow for fast Li⁺ diffusion. Thus, a pristine sulfur cathode battery with a SiO₂@MoS₂ interlayer exhibits an outstanding electrochemical performance with a negligible capacity decay of 0.028% per cycle over 2500 cycles. The core–shell design suggested in this study could be extended to other nanomaterials for the optimization of Li–S battery interlayers.