In order to ascertain the relative stabilities of the various components of the SEI, cells at 100 reactive cycle intervals were extracted (i.e. the structures shown in Fig. of the main text) and non-reactive molecular dynamics (of length 5 ns) were run on them. Fig. shows the mass density profiles for the cells extracted after reactive cycles 100, 500, 900 and 1300, before (i.e. at 0 ns) and after (i.e. at 5 ns) the MD simulation, with the profile for S-6