LAUSR

Lithium‐air batteries based on CO2 reactant (Li–CO2) have recently been of interest because it has been found that reversible Li/CO2 electrochemistry is feasible. In this study, a new medium‐entropy cathode catalyst, (NbTa)0.5BiS3, that enables the reversible electrochemistry to operate at high rates is presented. This medium entropy cathode catalyst is combined with an ionic liquid‐based electrolyte blend to give a Li–CO2 battery that operates at high current density of 5000 mA g−1 and capacity of 5000 mAh g−1 for up to 125 cycles, far exceeding reported values in the literature for this type of battery. The higher rate performance is believed to be due to the greater stability of the multi‐element (NbTa)0.5BiS3 catalyst because of its higher entropy compared to previously used catalysts with a smaller number of elements with lower entropies. Evidence for this comes from computational studies giving very low surface energies (high surface stability) for (NbTa)0.5BiS3 and transmission electron microscopystudies showing the structure being retained after cycling. In addition, the calculations indicate that Nb‐terminated surface promotes Li–CO2 electrochemistry resulting in Li2CO3 and carbon formation, consistent with the products found in the cell. These results open new direction to design and develop high‐performance Li–CO2 batteries.