Fundamental research into the Li-O₂ battery system has gone into high gear, gaining momentum due its very high theoretical specific energy. The electrochemical processes that drive this battery are represented by the total chemical reaction:. We report for the first time the technique of operando micro beam X-ray diffraction applied to monitor the decomposition of individual grains of Li₂O₂ in a working non-aqueous Li-O₂ battery. Due to the extremely small beam size and bright X-rays, the diffraction rings break up into spots, each spot representing a grain of Li₂O₂ having nanometer dimensions. We have studied two kinds of Li₂O₂; the first, electrochemically generated toroids of Li₂O₂ comprising of Li₂O₂ platelets formed at a low discharge current density of (E-Li₂O₂) and the second, chemically prepared Li₂O₂ incorporated into a carbon electrode (C-Li­₂O₂). The most obvious difference the two is the shape and size of the primary crystallites. Using this technique, we have time-resolved information on the individual transformation of a number of grains of both E-Li₂O₂ and C-Li₂O₂, following their complete decomposition.

Figure 1 Voltage curve corresponding to the Oxygen Evolution Reaction (OER) using a current density of 100 mA/cm², and the corresponding evolution of a 2D (100) reflection of Li₂O₂ following its decomposition.