Network construction resulted in a CRN containing 5,193 filtered species and 86,001,275 filtered reactions. With this network, we conducted 100,000 stochastic trajectories under four conditions, with combinations of two different applied potentials (+0.0V vs. Li/Li + and +0.5V vs. Li/Li + ) and two different initial states (one consisting only of Li + and ethylene carbonate (EC) and the other consisting of Li + , EC, and CO 2 ). Average trajectories for each condition are shown in the Supplementary Information. We emphasize that our goal is not to compute and observe the dynamics of SEI formation, but rather to identify key species and reaction pathways. We further note that we do not consider the effect of the electrode surface in our simulations. However, since the SEI can grow to a thickness of ∼ 10 -100nm, the effect of the electrode on the SEI chemistry should be small after the first reactions occur. Moreover, the products of the SEI are in general insensitive to the identity of the anode. The utility of our approach is demonstrated through analysis of the 36 network products collected from the set of four conditions previously described (Figure ). We first note that our automated procedure recovers 16 species that include a majority of the experimentally observed products of SEI formation (Fig. solid dark green). These include gases (H 2 , C 2 H 4 , CO), inorganic species (lithium carbonate (Li 2 CO 3 ) and lithium oxalate (Li 2 C 2 O 4 )), and alkyl carbonates (including species closely related to LEDC and LEMC, as well as lithium methyl carbonate or LMC, lithium butylene dicarbonate or LBDC, and lithium vinyl carbonate). We emphasize that these species are recovered even though reaction kinetics are entirely ignored in network exploration.