The practical application of lithium–sulfur
batteries
(LSBs)
is hampered by the slow lithium polysulfide (LIPS) conversion kinetics
and the uncontrollable anode-metal lithium dendrites. Herein, a three-dimensional
cation dual-active-site eggshell structure compound (3DCS-FMO@C) was
synthesized by soft template, ion exchange, and pyrolysis to modify
the commercial separator. Experimental and theoretical analysis results
showed that Mn2+ and Fe2+ sites in 3DCS-FMO@C
can synergistically adsorb LIPSs, effectively regulate the bidirectional
conversion dynamics of intermediate liquid-phase LIPSs and solid-phase
lithium sulfide, and reduce the energy barrier of the reaction. The
3DCS-FMO@C-modified separator with high mechanical stability and no
reduction in ion diffusion also had a lithiophilic central core that
can homogenize the lithium-ion flow, thereby inhibiting the dendrite
growth of lithium. Based on the above advantages, 3DCS-FMO@C-modified
separator LSBs had better electrochemical performance, including an
initial capacity of 1530 mAh g–1 at 0.1C and an
ultralow decay rate of 0.029% for 1000 cycles at 0.5C. A high area
capacity of 8.7 mAh cm–2 was achieved even with
high sulfur loading and poor electrolyte. This work provided a basis
for understanding the bidirectional catalysis for practical application
in LSBs and simultaneously solved the problem of lithium dendrites.