Electrocatalytic selenium hosts toward high-voltage nonaqueous zinc-selenium batteries

Abstract

The narrow electrochemical stability window (ESW), gaseous by-products, and interfacial issues in aqueous electrolytes have long hindered the advancement of Zn-ion batteries. Herein, we report the first application of a zinc trifluoromethylsulfonate/1-ethyl-3-methylimidazolium trifluoromethylsulfonate (Zn(TfO)2/[EMIm]TfO) ionic liquid electrolyte with wide ESW exceeding 3 V in nonaqueous zinc-selenium (Zn-Se) batteries. To further enhance the reaction kinetics, the Co single atoms anchored onto N-doped ordered mesoporous carbon (Co-N/C) with Co-N4 sites is designed as a Se host (Se@Co-N/C). Significantly, the Se@Co-N/C composite demonstrates an improved electrochemical performance, delivering a high discharge voltage of 1.5 V and a capacity of 410.6 mAh g−1. Comprehensive mechanistic studies reveal that the Co-N4 structure in the Co-N/C host acts as dual-function catalytic sites, lowering the energy barrier for both Zn(TfO)42− dissociation and Se(TfO)4 formation, thereby accelerating the conversion kinetics. This finding provides novel insights into designing stable Zn-Se batteries in nonaqueous ionic liquid electrolytes.