3D conductive molecular framework derived MnO2/N, P co-doped carbon as sulfur hosts for high-performance lithium‑sulfur batteries

Abstract

The practical application of lithium-sulfur (LiS) batteries is impeded by the shuttle effect and slow redox reaction kinetics, resulting in rapid capacity decay and low Coulombic efficiency. Three dimensional (3D) carbon-based network structure is used as sulfur host due to its special properties, such as high porosity and high conductivity. In this work, 3D MnO2/N, P co-doped carbon (3D MnO2/NPC) composites were achieved via freeze-drying MnO2/polyaniline composite aerogel followed by carbonizing process. The strongly polar MnO2 skeleton can provide sufficient adsorption capacity to anchor polysulfide and the heteroatom-doped carbon can compensate for the poor conductivity of MnO2 to guarantee the participation of rapid electrochemical reactions. As a result, the MnO2/NPC/S cathode demonstrates an initial specific discharge capacity of 1189 mAh g−1 at 0.2 C and a high rate capability of 569.2 mAh g−1 at 5 C, as well as excellent long-term cycling performance with the capacity decay rate of 0.033 % per cycle for 1000 cycles at 1 C. Moreover, the cathode exhibits excellent cycling stability even at a high sulfur loading of 6 mg cm−2.