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

Abstract

In Li–O 2 batteries, Li 2 O 2 serves as the primary cathodic material but its wide band gap imparts insulating properties. Regulating the composition and morphology of Li 2 O 2 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 Li 2 O 2, achieving gradient control and optimized growth of Li 2 O 2 . 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 O 2 – /LiO 2, highlighting the superior reversibility of Co(acac) 2 enhanced Li–O 2 batteries. Both experimental and theoretical results indicate that this novel Li–O 2 battery system exhibits rapid reaction kinetics, with a reduced overpotential of 520 mV and extended cyclability, surpassing 400 cycles with lower polarization.