MoN Supported on Graphene as a Bifunctional Interlayer for Advanced Li-S Batteries

Rational design of effective polysulfide barriers is highly important for high-performance lithium-sulfur (Li-S) batteries. A variety of adsorbents have been applied as interlayers to alleviate the shuttle effect. Nevertheless, the unsuccessful oxidation of Li₂S on interlayers leads to loss of active materials and blocks Li ion transport. In this work, a MoN-based interlayer sandwiched between the C-S cathode and the separator is developed. Such an interlayer not only strongly binds lithium polysulfides via Mo-S bonding but also efficiently accelerates the decomposition of Li₂S. The acceleration mechanism toward Li₂S decomposition is determined to be a combination of contributions of catalytic cleavage of Li-S bond in Li₂S based on the proposed covalence-activation mechanism and rapid migration of the produced Li ions. As a result, the C–S cathodes with the as-developed interlayer manifest a negligible charging potential barrier and outstanding cycling stability with a very low capacity fading rate of 0.023% per cycle during 1500 cycles at 1 C. High areal capacity of 6.02 mAh cm⁻² is achieved for high sulfur loading of 7.0 mg cm⁻² after cycling at 0.1 C. The material and strategy demonstrated in this work can open the door toward developing shuttle suppression interlayers without impairing cathode performance.