Selective S/Li₂S Conversion via in-Built Crystal Facet Self-Mediation: Toward High Volumetric Energy Density...

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 ZrB₂ nanoflakes with only 2 wt % conductive carbon. The resultant closely packed ZrB₂-S electrode delivers a high areal capacity of 8.5 mAh cm^-2 and cell-level volumetric energy density of 533 Wh L^-1 with a high sulfur loading of 7.8 mg cm^-2 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.