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

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.