Co(acac)2-Mediated Regulation of Li2O2 Gradient Growth in Lithium–Oxygen Batteries

In Li-O₂ batteries, Li₂O₂ serves as the primary cathodic material but its wide band gap imparts insulating properties. Regulating the composition and morphology of Li₂O₂ enables the construction of a novel cathodic structure with exceptional electrochemical performance. Herein, we introduce an organic salt containing cobalt ions, cobalt acetylacetonate (Co(acac)₂), into the cathodic electrolyte. We exploit its cation migration characteristics under an electric field to facilitate the generation and decomposition of Co-doped Li₂O₂, achieving gradient control and optimized growth of Li₂O₂. Moreover, the Co(acac)₂ molecule stabilizes the properties of LiO_x species and mitigates side reaction. In situ UV-vis and XANES spectra reveal direct interactions between Co(acac)₂ and O₂^-/LiO₂, highlighting the superior reversibility of Co(acac)₂ enhanced Li-O₂ batteries. Both experimental and theoretical results indicate that this novel Li-O₂ battery system exhibits rapid reaction kinetics, with a reduced overpotential of 520 mV and extended cyclability, surpassing 400 cycles with lower polarization.