Copper-Ion-Mediated Selenium Electrochemistry Enables 3.5 V Selenium Batteries

Abstract

Selenium (Se) is an attractive cathode candidate for rechargeable batteries owing to its high theoretical capacity and favorable electronic conductivity. However, conventional Se batteries relying on alkali metal-ion charge carriers are plagued by low operating voltages (<2.1 V), sluggish kinetics, and polyselenide shuttling. In this study, we extend copper-ion-mediated selenium electrochemistry from aqueous systems to nonaqueous electrolytes by identifying a Cu(ClO4)2/carbonate electrolyte that enables reversible Cu-mediated Se conversion. The copper-ion mediation mechanism produces insoluble and highly conductive CuxSe intermediates, which effectively suppress polyselenide dissolution and shuttling while enabling rapid reaction kinetics, as reflected by the low polarization of ∼0.1 V. Moreover, this approach elevates the selenium redox potential from below −0.5 V to +0.5 V vs SHE, enabling a hybrid lithium–selenium battery with a 3.5 V discharge voltage, compared to ∼2.0 V in conventional alkali metal-Se systems. This work demonstrates the feasibility of implementing Cu-mediated selenium electrochemistry in nonaqueous media and achieves a high-voltage Se-based battery.