Fig. 3. Characterization and electrochemical analysis of oxygen cathode.

(A) Full charge-discharge cycle of a Li||O₂ cell using ionomer-enriched 1 M LiNO₃-DMA electrolyte operated at a current density of 31.25 μA/cm². The different points on the voltage profile indicate various stages at which the same-type cells were stopped for ex situ analysis. The images below the voltage profile show the surface of a carbon cathode at the D1, D2, and D3 discharge phases. The size of the Li₂O₂ is seen to be increasing over the course of discharge. C1 and C2 show the stages of recharge; it is seen in C1 that the cathode is absent of Li₂O₂ particles. (B) XRD analysis showing various characteristic peaks for a fully discharged and a recharged Li||O₂ battery. Here, diamonds denote Li₂O₂ peak and circles represent carbon. The red lines refer to the control electrolyte (1 M LiNO₃-DMA), whereas black lines show the result for the same electrolyte with the ionomer additive. (C) The diameter of Li₂O₂ particles obtained by fully discharging a Li||O₂ cell is plotted as a function of current density. Here, black indicates the electrolyte (1 M LiNO₃-DMA) with the ionomer additive, whereas red represents data from Lau and Archer’s paper that used the electrolyte 1 M LiTF in TEGDME. *From Lau and Archer (10).