Reacquainting the Sudden-Death and Reaction Routes of Li-O₂ Batteries by Ex Situ Observation of Li₂O₂ Distribution Inside a Highly Ordered Air Electrode.

Abstract

The unclear Li₂O₂ distribution inside an air electrode stems from the difficulty of conducting observation techniques inside a porous electrode. In this work, an integrated air electrode is prepared with highly ordered channels. The morphological composition and distribution of Li₂O₂ inside the real air electrode are clearly observed for the first time. The results show that the toroidal Li₂O₂ is constrained by the channel size and exhibits a larger diameter on the separator side at high currents. In contrast to the reported single-factor experiments, the coupling effects of charge transfer impedance and concentration polarization on sudden death are analyzed in-depth at low and high currents. The growth model suggests that toroidal Li₂O₂ exhibits a high dependence on the electrode surface structure. A new route is proposed in which the Li₂O₂/electrode interface of a toroid is controlled partially by the second single-electron reduction.