Chemisorption and electrocatalytic effect from CoxSny alloy for high performance lithium sulfur batteries

Lithium-sulfur (Li-S) batteries have attracted considerable attention as a promising candidate for next-generation energy storage systems due to their high theoretical specific capacity and specific energy. However, the polysulfide shuttle, huge volume change of sulfur and kinetics sluggishness limit their practical applications. Here, we synthesize a hollow CoxSny modified N-doped carbon (denoted as E-CoxSny/NC) as host material of Li-S batteries through a stepwise coating-etching approach. The introduction of tetraethyl orthosilicate (TEOS) and the pyrogenation of polydopamine (PDA) induce the formation of CoxSny alloy at high temperature. The novel metal-N-carbon-based composite possesses strong chemisorption and electrocatalytic conversion activity for lithium polysulfides (LiPSs), which can accelerate the redox reaction kinetics and minimize the polysulfides loss. Therefore, the prepared E-CoxSny/NC/S cathode shows high specific capacity of 1006 mAh g(-1) after 100 cycles at 0.2C, good long-term cycling stability with a capacity retention of 81.2% after 500 cycles at 1.0C, and superior rate capacity (similar to 778mA h g(-1) at 2.0C). Moreover, the E-CoxSny/NC/S composite displays low polarization and fast redox reaction kinetics, especially at high current density, due to the catalysis effect of CoxSny alloy for LiPSs conversion during cycling, demonstrating its great potential as advanced cathode for high performance Li-S batteries.