Symbiotic reactions over a high-entropy alloy catalyst enable ultrahigh-voltage Li–CO2 batteries†

Abstract

Metal–CO₂ rechargeable batteries have immense application potential owing to their high theoretical energy densities and CO₂ capture capabilities. However, batteries relying on carbonate production typically offer low output voltages (<2.6 V) and energy efficiencies. Herein, the six-element high-entropy alloy PtRuZnCoNiCu (PRZCNC-HEA) was employed as a cathode catalyst in metal–CO₂ batteries. The multiple reaction sites on the PRZCNC-HEA surface offered a symbiotic reaction pathway for oxalate product generation with a high discharge voltage and a low bandgap. The metal–oxalate coordination mode and metal–oxalate–carbonate coupling mechanism stabilized the oxalate product. Li–CO₂ batteries with PRZCNC-HEA as the cathode catalyst achieved a high discharge voltage (3.06 V) and low overpotential (0.32 V), representing the best-reported performance to date. Theoretical calculations combined with experimental characterization confirmed the stabilization mechanism. This work can advance the design and modulation of conversion reactions in metal–CO₂ batteries.