High-performance Li–S battery cathode with catalyst-like carbon nanotube-MoP promoting polysulfide redox

Abstract

Despite promising characteristics such as high specific energy and low cost, current Li–S batteries fall short in cycle life. Improving the cycling stability of S cathodes requires immobilizing the lithium polysulfide (LPS) intermediates as well as accelerating their redox kinetics. Although many materials have been explored for trapping LPS, the ability to promote LPS redox has attracted much less attention. Here, we report for the first time on transition metal phosphides as effective host materials to enhance both LPS adsorption and redox. Integrating MoP-nanoparticle-decorated carbon nanotubes with S deposited on graphene oxide, we enable Li–S battery cathodes with substantially improved cycling stability and rate capability. Capacity decay rates as low as 0.017% per cycle over 1,000 cycles can be realized. Stable and high areal capacity (>3 mAh·cm⁻²) can be achieved under high mass loading conditions. Comparable electrochemical performance can also be achieved with analogous material structures based on CoP, demonstrating the potential of metal phosphides for long-cycle Li–S batteries.