Balanced capture and catalytic ability toward polysulfides by designing MoO₂–Co₂Mo₃O₈ heterostructures for lithium–sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries, as the next generation of energy storage systems, are currently limited by insufficient capture ability and sluggish catalytic reaction kinetics, thus leading to serve the shuttle effect of lithium polysulfides (LiPSs). Realizing the accelerated conversion of polysulfides in the cathode host of Li-S batteries is an effective way to improve its coulombic efficiency. The essence of fast conversion relies on enhanced oxidation reaction kinetics by virtue of the metal catalyst, but the generation of various intermediates exacerbate the complexity of the system and perplex the perfect operation of batteries relying on only one catalyst. In this work, the <i>x</i>MoO₂:<i>y</i>Co₂Mo₃O₈ heterostructures were designed, in which controlling the content of cobalt could balance the capture capability towards LiPSs by MoO₂ and catalytic ability of liquid-solid conversion by Co₂Mo₃O₈ catalytic sites. Therefore, utilizing synergy effect of MoO₂-Co₂Mo₃O₈ heterostructure enhances capture and catalytic ability toward polysulfides in Li-S batteries. As a result, the 9MoO₂:2Co₂Mo₃O₈-based cathode delivers excellent reversibility of 880 mA h g^-1 after 100 cycles at 0.2C and 509 mA h g^-1 after 1000 cycles at 1C with 0.056% capacity decay each cycle. This work provides a new method for synthesizing heterostructures by doping metals. Moreover, it promotes the understanding of balancing and promoting the capture capacity and catalytic conversion ability toward LiPSs.