Synergistic Adsorption-Electrocatalysis of Mo–MoB Heterostructures for Lithium–Sulfur Batteries

Because of the high theoretical capacity of lithium–sulfur (Li–S) batteries and the relatively low cost of sulfur, these batteries have been regarded as one of the most promising types of energy storage systems. The severe shuttle effect of the polysulfide deteriorates the cycle stability, and the inferior conductivity of the sulfur and polysulfide also lead to sluggish electrochemical kinetics. Herein, we use a facile molten salt method to synthesize the heterostructure Mo–MoB, which is coated on a commercial PP separator for the Li–S batteries. Experimental analysis and theoretical calculation results show that the heterostructure Mo–MoB can serve as a physical barrier and chemical absorbent to hinder the shuttle effect, as well as be a bidirectional catalyst to simultaneously accelerate the conversion of polysulfides into Li2S and decomposition of Li2S with the synergistically catalytic effect of Mo and MoB. Consequently, the cell with the heterostructure Mo–MoB-modified separator demonstrates superior cycle performance (capacity fading rate of ∼0.07% per cycle during 300 cycles at 0.5 C) as well as increased rate capability (670 mAh g–1 at 2 C). This work indicates that heterostructure metal borides could be adsorption-catalysis material to functionalize the separator, which can be a new strategy to design the high-performance Li–S batteries.