Meanwhile, the surface chemistry of the cycled LiCoO2 electrodes was probed via the X-ray photoelectron spectroscopy (XPS) measurement. As seen from the fitted O 1s XPS spectra in Figure , compared with the bare LiCoO2 electrode, lattice oxygen at 529.8 eV (shaded area) shows a flatter peak in the cycled LiCoO2 electrodes (50 cycles). The signals (C-O and C=O) from the CEI components overwhelm the lattice oxygen peak, implying the electrolyte decomposition on the LiCoO2 surface. However, the inorganic signals, especially for the LiF species (56.0 eV in Li 1s and 684.8 eV in F 1s, Figures and), are not particularly noticeable. This surface can only be identified as an organic-inorganic hybrid surface, which is distinct from the inorganic-dominated surface observed in the salt-concentrated ether electrolytes for high-voltage LMBs. To further confirm the stability of this surface, the LiCoO2 electrodes pre-polarized in the NO3 --containing ether electrolyte were carefully reassembled in the NO3 --free ether electrolyte for sequential cycling (Figure ).