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

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.