We carried out combustion elemental analysis and inductively coupled plasma-optical emission spectroscopy (ICP-OES) on both PTI derivatives to rule out carbonization and presence of residual ions in PTI-IF, and we find the results to be in good agreement with the theoretical chemical formulae (Table ). As observed previously in PTI-LiCl, the Li-ion loading in PTI-LiBr is too high to be explained just by intercalation of LiBr. Excess lithium isoelectronically replaces some of the hydrogen atoms at the imide bonds. Overall, we obtain a composition of [(C3.0N3.0)2(N1.0H1-xLix)3•Li1.2Br1.2, x=0.2] for PTI-LiBr (theoretical C6H3N9LiBr). Electron energy loss spectra (EELS) confirm the presence of carbon, nitrogen, lithium, and bromine in PTI-LiBr. K-edges of additional elements are not observed confirming the high purity of the product on microscopic scale (Figure ).