Fig. 4: Investigation of positive electrode chemistry and CEI stability after 50 cycles in baseline and FHFP-modified electrolytes.

a–c The intensity depth profiles of TOF-SIMS for (a) \({{{{\rm{MnF}}}}}_{2}^{-}\), (b) \({{{{\rm{NiF}}}}}_{2}^{-}\), and (c) \({{{{\rm{CHO}}}}}_{2}^{-}\) fragments on the surface of the LNMO positive electrode after 50 cycles at 29.4 mA g⁻¹ between 3.5–4.9 V. The insets are the 3D views of corresponding secondary ions and corresponding scale bars. d, e F 1 s spectra of the CEI on LNMO after 50cycles in baseline (d) and FHFP-modified electrolyte (e) at 29.4 mA g⁻¹ between 3.5-4.9 V. f Atomic contents derived from the XPS spectra of the CEI on LNMO cycled in different electrolytes. g In situ EIS of Li | |LNMO cells cycled in different electrolytes during charge/discharge at a cutoff voltage of 4.9 V and 29.4 mA g⁻¹ (25 ^oC) after 50 cycles at 29.4 mA g⁻¹. h, i DRT curves obtained from in situ EIS results during the discharge process in baseline (h) and FHFP-modified electrolyte (i). j, k TEM images of LNMO after 50 cycles at 29.4 mA g⁻¹ between 3.5–4.9 V in the baseline (j) and FHFP-modified electrolyte (k).