Structural Design of Electrocatalyst-Decorated MXenes on Sulfur Spheres for Lithium-Sulfur Batteries

Lithium-sulfurbatteries (LSBs) are known to be potentialnext-generation energy storage devices. Recently, our group reportedan LSB cathode made using sulfur spheres that has been sphericallytemplated by MXene nanosheets decorated with CoSe2 nanoparticles,forming a "loose-templating" configuration. It was postulatedthat the minimal restacking of the outer nanoparticle-decorated MXenelayer helps to enable facile ionic transport. However, as the nanosheetsdo not adhere conformally to the internal sphere's surface,such a configuration can be controversial, thus requiring a more systematicunderstanding. In this work, we report and quantify for the firsttime the independent and dependent variables involved in this morphology,allowing us to identify that having smaller nanoparticles resultedin better Li+ ion transport and enhanced electrochemicalperformances. The optimized cathode structure exhibited an initialspecific capacity of 1274 mAh/g and a 0.06% decay rate per cycle at0.5 C over 1000 cycles in LSBs.