Improving confinement and redox kinetics of polysufides through hollow NC@CeO2 nanospheres for high-performance lithium-sulfur batteries

Abstract

Lithium-sulfur batteries are regarded as next generation energy storage systems because of their high theoretical specific capacity and low cost. However, the polysulfide shuttle effect, low electronic conductivity of sulfur/lithium sulfides and slow redox kinetics of polysulfide conversion still limit their practical application. Herein, we design a hollow nanosphere structure with CeO2 shell/ultrathin nitrogen-doped carbon shell as highly efficient sulfur host for lithium-sulfur batteries. The unique structure not only offers physical entrapment for sulfur species by CeO2/carbon shells, but also provides strong chemical adsorption and activation sites for chemical adsorption and catalytic conversion of polysulfides through CeO2 nanoparticles. Moreover, the unique hollow structure offers enough space for volume variations of sulfur during charge/discharge process and facilitates fast electron/ion transport to continuously activate active material, therefore improving the electrochemical performances of lithium-sulfur batteries. By combining these advantages, the obtained NC@H-CeO2/S cathodes exhibit high reversible capacity (1348 mAh g−1 at 0.2 C), excellent rate capability (548 mAh g−1 at 5 C) and superior cycle stability (632 and 458 mAh g−1 at 2 and 5 C after 500 cycles, respectively). Moreover, the cathodes with high sulfur loading of 3.5 mg cm−2 remain excellent rate capability and cycling stability. This work provides a new strategy to the design of advanced cathode materials for high-performance lithium-sulfur batteries.