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 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.