Boosting polysulfide redox conversion of Li-S batteries by one-step-synthesized Co-Mo bimetallic nitride

摘要

Lithium-sulfur(Li-S)batteries are considered as one of the most promising next generation energy storage systems due to the high theoretical specific capacity,low cost,and environmental benignity.However,the notorious shuttle effect of polysulfides hinders the practical application of Li-S batteries.Herein,we have rationally designed and synthesized sea urchin-like Co-Mo bimetallic nitride(Co_(3) MO_(3) N)in the absence of additional nitrogen sources with only one step,which was applied as the sulfur host materials for Li-S batteries.The results indicate that Co_(3) Mo_(3) N can efficiently anchor and catalyze the conversion of polysulfides,thus accelerating the electrochemical reaction kinetics and enabling prominent electrochemical properties.As a consequence,the S@Co_(3) Mo_(3) N cathode exhibits a high rate performance of 705 mAh g^(-1) at 3 C rate and an excellent cycling stability with a low capacity fading rate of 0.08%per cycle at 1 C over 600 cycles.Even at a high sulfur loading of 5.4 cmg cm^(-2),it delivers a high initial areal capacity of 4.50 mAh cm^(-2) which is still retained at 3.64 mAh cm^(-2) after 120 cycles.Furthermore,the catalytic mechanism and structural stability of Co_(3) Mo_(3) N during cycling were elucidated by a combination of X-ray photoelectron spectroscopy and X-ray absorption fine structure.This work highlights the strategy of structure-catalysis engineering of bimetallic nitride,which is expected to have a wide application in Li-S batteries.