An advanced SRR catalyst based on hollow polyhedral carbon skeleton modified by Tri-metal (Zn, Co, Fe) for Li-S batteries

Li-S batteries have gained a lot of attention owing to their theoretical specific capacity and energy density. Nevertheless, the shuttle of lithium polysulfides (LiPSs) and other flaws prevent their further application. In order to solve the problems such as shuttle effect of LiPSs and slow REDOX reaction kinetics, metal–organic framework (MOF) derivatives have attracted considerable interest as the novel sulfur hosts for Li-S batteries. In this work, a novel MOFs-based sulfur host that contains Zn, Co, Fe and N-doped hollow polyhedral graphite carbon (ZnCoFe-NC) is deliberately designed and synthesized. Its special hollow polyhedron structure provides the physical trapping ability and chemisorption space for LiPSs. Zn, Co, Fe and N doping not only have excellent chemisorption ability, but also have high electrocatalytic activity in their synergistic catalytic effect, which can accelerate the transformation of LiPSs and indirectly reduce the dissolution of LiPSs. The confinement and efficient conversion of LiPSs are successfully achieved, thus significantly improving the performance of Li-S batteries. The assembled battery based on the ZnCoFe-NC/S cathode exhibits a high specific discharge capacity of 1452 mAh/g at 0.1C (1C = 1675 mA g−1). With the high current density of 1C, it still shows a high capacity of 1061 mAh/g and maintains a capacity of 751 mAh/g even after 400 cycles with a capacity degradation rate of only 0.073% each cycle. In particular, the ZnCoFe-NC/S cathode can be stabilized for 200 cycles under the sulfur loading of up to 6 mg cm−2. Thus, this work provides a valuable approach for the proper scheme of cathode catalysts and develops a way of thinking for Li-S batteries with high-performance.