A Conductive Molecular Framework Derived Li2S/N, P-Codoped Carbon Cathode for Advanced Lithium-Sulfur Batteries

摘要

Li2S is one of the most promising cathode materials for Li-ion batteries because of its high theoretical capacity and compatibility with Li-metal-free anode materials. However, the poor conductivity and electrochemical reactivity lead to low initial capacity and severe capacity decay. In this communication, a nitrogen and phosphorus codoped carbon (N,P-C) framework derived from phytic acid doped polyaniline hydrogel is designed to support Li2S nanoparticles as a binder-free cathode for Li-S battery. The porous 3D architecture of N and P codoped carbon provides continuous electron pathways and hierarchically porous channels for Li ion transport. Phosphorus doping can also suppress the shuttle effect through strong interaction between sulfur and the carbon framework, resulting in high Coulombic efficiency. Meanwhile, P doping in the carbon framework plays an important role in improving the reaction kinetics, as it may help catalyze the redox reactions of sulfur species to reduce electrochemical polarization, and enhance the ionic conductivity of Li2S. As a result, the Li2S/N, P-C composite electrode delivers a stable capacity of 700 mA h g(-1) with average Coulombic efficiency of 99.4% over 100 cycles at 0.1C and an areal capacity as high as 2 mA h cm(-2) at 0.5C.