Promoting Polysulfide Conversion via a Lithium-Ion Reservoir Based on La-Doped MoO3 Nanorods for Li-S Batteries

The practical application of Li-S batteries is seriously plagued by the severe shuttle effect and sluggish conversion kinetics of polysulfides. To circumvent these obstacles, we herein construct La-doped MoO3 nanorods (La-MoO3) as a functional lithium-ion reservoir for sulfur hosts. By virtue of its enhanced lithium intercalation kinetics, the La-MoO3 actively accumulates Li+ ions during electrochemical cycling, which may promote the chemical conversion of soluble long-chain polysulfides to short-chain species. This behavior helps restrain the shuttle effect and expedite the sulfur redox process via a probable lithium-reservoir-related catalytic effect. The La-MoO3/S cathode achieves a high reversible capacity of 1376 mAh g−1 at 0.1 C, along with excellent long-term cyclability featuring a low decay of 0.08% per cycle over 160 cycles at 0.5 C. Even at a high rate of 1 C, it retains remarkable durability with an ultralow fading rate of 0.068% per cycle over 450 cycles. This work demonstrates the potential of La-doping to build an efficient lithium-ion reservoir and provides insight into the correlation between lithium-ion storage and accelerated polysulfide conversion, which may guide the development of high-performance Li-S cathodes.