LAUSR

Lithium‐ion batteries (LIBs) are a widely used battery technology. During the initial LIB cycle, a passivation layer, called the solid electrolyte interphase (SEI), forms on the anode surface, which plays a crucial role in the performance and long‐term cyclability of LIBs. The overall mesoscale mechanisms of SEI formation and its composition remain elusive both in experimental and computational approaches. Here a multiscale approach to comprehensively characterize the growth and composition of the SEI based on a chemistry‐specific reaction network is presented. Generating an ensemble of over 50 000 simulations representing different reaction conditions, it is found that the organic SEI forms and grows in a solution‐mediated pathway by aggregation of SEI precursors far away from the surface via a nucleation process. The subsequent rapid growth of these nuclei leads to the formation of a porous layer that eventually covers the surface. This finding offers a solution to the paradoxical situation that SEI constituents can form only near the surface, where electrons are available, but does not stop growing when this narrow region is covered. The study is able to identify the key reaction parameters that determine SEI thickness, which pave the way to optimize battery performance and lifetime.