High-Capacity and High-Rate Discharging of a Coenzyme Q10-Catalyzed Li–O2 Battery

Abstract

Discharging of the aprotic Li–O₂ battery relies on O₂ 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–O₂ 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 Q₁₀ (CoQ₁₀) that can efficaciously drive solution phase formation of Li₂O₂ in current benchmark ether-based Li–O₂ 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⁻²_areal, the CoQ₁₀-catalyzed Li–O₂ battery can deliver a discharge capacity that is ≈40–100 times what the pristine Li–O₂ battery could achieve. The drastically enhanced electrochemical performance is attributed to the CoQ₁₀ that not only efficiently mediates the electron transfer from the cathode to dissolve O₂ 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 CoQ₁₀ and Li₂O₂ are understood with density functional theory calculations.

The capacity and rate capability of current Li–O₂ batteries are drastically enhanced with a biomolecular redox mediator of coenzyme Q₁₀, which not only effectively mediates the electron transfer from the cathode to dissolved O₂ but also strongly interacts with the newly formed Li₂O₂ in electrolyte solution retarding its precipitation on the cathode surface.

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