  Growth of the solid electrolyte interphase (SEI) is a primary driver of
capacity fade in lithium-ion batteries. Despite its importance to this device
and intense research interest, the fundamental mechanisms underpinning SEI
growth remain unclear. In Part I of this work, we present an electroanalytical
method to measure the dependence of SEI growth on potential, current magnitude,
and current direction during galvanostatic cycling of carbon black/Li half
cells. We find that SEI growth strongly depends on all three parameters; most
notably, we find SEI growth rates increase with nominal C rate and are
significantly higher on lithiation than on delithiation. We observe this
directional effect in both galvanostatic and potentiostatic experiments and
discuss hypotheses that could explain this observation. This work identifies a
strong coupling between SEI growth and charge storage (e.g., intercalation and
capacitance) in carbon negative electrodes.
