Facile synthesis of Fe3C nano-particles/porous biochar cathode materials for lithium sulfur battery

Abstract Reasonable design of porous biochar materials with good conductivity, excellent sulfur dispersion, strong adsorption ability to polysulfides (LiPSs), low cost and comprehensive performance is proper way for solving the problem of ‘shuttle effect’ of lithium sulfur battery (Li-S battery). Herein, a novel facile strategy, utilizing potassium ferrate (K2FeO4), to fulfill the synchronous carbonization and iron carbide (Fe3C) doping of folium cycas to prepare Fe3C nano-particles/porous biochar (Fe3C/PB) composite materials is proposed. The as-prepared Fe3C/PB samples possess a porous structure with a large specific surface area (2732.3 m2 g-1) and a cumulative pore volume of 1.6 cm3 g-1, in which Fe3C plays a key role in electronic transmission, LiPSs adsorption and conversion in Li-S battery. After sulfur infusion, the Fe3C/PB@S composite with 69.6 wt% sulfur loading exhibits the highest initial discharge capacity of 1347.7 mA h g-1 at the rate of 1 C. It is stable at 837.6 mA h g-1 after 5 cycles, and is capable to maintain at 555.3 mA h g-1 even after 250 cycles. The rational design of porous structural biochar materials with Fe3C doping is of great significance to achieve low-cost, green and large-scale production to improve the electrochemical performance of Li-S battery and promote the industrial applications.