Selective S/Li<sub>2</sub>S Conversion <i>via</i> in-Built Crystal Facet Self-Mediation: Toward High Volumetric Energy Density Lithium-Sulfur Batteries.

Wu, Tianli; Qi, Jing; Xu, Mengyao; Zhou, Dan; Xiao, Zhubing · ACS Nano · 2020

basic_science · Level V

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Abstract

The gravimetric, areal, and volumetric capacities pose important influences on market penetration for secondary batteries. Carbonaceous materials take a leading stand for the improvement of gravimetric and areal capacity in lithium-sulfur batteries; however, they exhibit some intrinsic deficiencies, including insufficient fixation on lithium polysulfides (LiPS) and low tap density, incurring poor volumetric performance and inferior cycling behavior. Here, we report a sulfur cathode based on highly conductive ZrB<sub>2</sub> nanoflakes with only 2 wt % conductive carbon. The resultant closely packed ZrB<sub>2</sub>-S electrode delivers a high areal capacity of 8.5 mAh cm<sup>-2</sup> and cell-level volumetric energy density of 533 Wh L<sup>-1</sup> with a high sulfur loading of 7.8 mg cm<sup>-2</sup> and an ultralow electrolyte dosage. With combined spectroscopic studies and theoretical calculation results, it was confirmed that an in-built Janus crystal facet self-mediation is on-site constructed by the exposed B and Zr atoms for an effective bonding and selective conversion on LiPS upon charge-discharge processes.