Fig. 5

opXPS determination of chemically resolved cell polarization/overpotential. XPS spectra showing chemically resolved BE shifts caused by applied current bias a before charging (LPS/Lifoil); and b–e after the charging half-cycle (Li/LPS/Lifoil). f Summarizes the current-bias-induced BE shifts extracted by peak fitting for each of the observed SEI phases. Individual overpotential losses associated with each phase can be determined from these shifts