It
is a significant challenge to design a dense high-sulfur-loaded
cathode and meanwhile to acquire fast sulfur redox kinetics and suppress
the heavy shuttling in the lean electrolyte, thus to acquire a high
volumetric energy density without sacrificing gravimetric performance
for realistic Li–S batteries (LSBs). Herein, we develop a cation-doping
strategy to tailor the electronic structure and catalytic activity
of MoSe2 that in situ hybridized with
conductive Ti3C2T
x
MXene, thus obtaining a Co-MoSe2/MXene bifunctional catalyst
as a high-efficient sulfur host. Combining a smart design of the dense
sulfur structure, the as-fabricated highly dense S/Co-MoSe2/MXene monolith cathode (density: 1.88 g cm–3,
conductivity: 230 S m–1) achieves a high reversible
specific capacity of 1454 mAh g–1 and an ultrahigh
volumetric energy density of 3659 Wh L–1 at a routine
electrolyte and a high areal capacity of ∼8.0 mAh cm–2 under an extremely lean electrolyte of 3.5 μL mgs
–1 at 0.1 C. Experimental and DFT theoretical results
uncover that introducing Co element into the MoSe2 plane
can form a shorter Co–Se bond, impel the Mo 3d band to approach
the Fermi level, and provide strong interactions between polysulfides
and Co-MoSe2, thereby enhancing its intrinsic electronic
conductivity and catalytic activity for fast redox kinetics and uniform
Li2S nucleation in a dense high-sulfur-loaded cathode.
This deep work provides a good strategy for constructing high-volumetric-energy-density,
high-areal-capacity LSBs with lean electrolytes.
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