Quantum‐Sized Co Nanoparticles with Rich Vacancies Enabled the Uniform Deposition of Lithium Metal and Fast Polysulfide Conversion

Abstract

AbstractThe notorious polysulfide shuttling and uncontrollable Li‐dendrite growth are the main obstacles to the marketization of Li‐S batteries. Herein, a dual‐functional material consisting of vacancy‐rich quantum‐sized Co nanodots anchored on a mesoporous carbon layer (v‐Co/meso‐C) is proposed. This material exposes more active sites to improve its reaction performance and simultaneously realizes excellent lithiophilicity and sulfiphilicity characteristics in Li‐S electrochemistry. As Li metal deposition hosts, v‐Co/meso‐C shows small nucleation overpotential, low polarization, and ultra‐long cycling stability in both half and symmetric cells, as confirmed by experimental studies. On the S cathode side, experimental and theoretical calculations demonstrate that v‐Co/meso‐C enhances the adsorption of polysulfides and boosts their catalytic conversion rate. This, in turn, suppresses the shuttle effect of polysulfides and improves sulfur utilization efficiency. Finally, a shuttle‐free and dendrite‐free v‐Co/meso‐C@Li//v‐Co/meso‐C@S full cell is fabricated, exhibiting excellent rate performance (739 mAh g−1 at 5.0 C) and good cyclability (capacity decay rate is 0.033% and 0.035% per cycle at 2.0 and 5.0 C, respectively). Even a pouch cell with high sulfur loading (5.5 mg cm−2) and lean electrolyte/sulfur (4.8 µL mg−1) can still work 50 cycles with 80% capacity retention rate. This study shows far‐reaching implications in the design of dendrite‐free, shuttle‐free Li‐S batteries.