High-Capacity and High-Rate Discharging of a Coenzyme Q(10)-Catalyzed Li-O-2 Battery

Discharging of the aprotic Li-O-2 battery relies on O-2 reduction to insulating solid Li2O2, which can either deposit as thin films on the cathode surface or precipitate as large particles in the electrolyte solution. Toward realizing Li-O-2 batteries with high capacity and high rate capability, it is crucially important to discharge Li2O2 in the electrolyte solution rather than on the cathode surface. Here, a soluble electrocatalyst of coenzyme Q(10) (CoQ(10)) that can efficaciously drive solution phase formation of Li2O2 in current benchmark ether-based Li-O-2 batteries is reported, which would otherwise lead to Li2O2 surface-film growth and premature cell death. In the range of current densities of 0.1-0.5 mA cm(areal)(-2), the CoQ(10)-catalyzed Li-O-2 battery can deliver a discharge capacity that is approximate to 40-100 times what the pristine Li-O-2 battery could achieve. The drastically enhanced electrochemical performance is attributed to the CoQ(10) that not only efficiently mediates the electron transfer from the cathode to dissolve O-2 but also strongly interacts with the newly formed Li2O2 in solution retarding its precipitation on the cathode surface. The mediated oxygen reduction reaction and the bonding mechanism between CoQ(10) and Li2O2 are understood with density functional theory calculations.