A path to form bi-dioxolylidene is shown in Figure . This network pathway has the 3rd lowest cost for simulations with CO 2 was present as a starting species at 0.0V vs. Li/Li + . In the pathway, CO 2 reduces twice and coordinates with Li + , forming Li + CO 2 2-. This Li + CO 2 2-species reacts with EC to form Li + CO 3 2-and the 1,3-dioxolylidene carbene, which we abbreviate as dioxolylidene. Two of these carbenes can then combine to form the dimer bi-dioxolylidene. The identified elementary mechanism follows the same general steps as the network pathway -coordinate and reduce, form dioxolylidene, and then dimerize two carbenes -but differs in two main ways. First, it is more favorable to reduce EC than CO 2 , which changes the initial steps of the mechanism. Second, we found that the carbene formation actually occurs via an addition-elimination mechanism with two elementary steps. The addition, which results in an EC-CO 2 adduct, has a barrier ∆G ‡ = 0.20 eV, and the elimination to produce Li + CO 3 2-and dioxolylidene has a barrier ∆G ‡ = 0.01 eV.