Fig. 4: Redox reaction mechanism of H₂TEPP.

a Ex-situ Raman spectra of H₂TEPP at different charge/discharge states. b In situ FTIR spectra of H₂TEPP during the second cycle. c–e Ex situ XPS spectra of (c) N 1 s, (d) Al 2p, (e) Cl 2p. f The proposed 12-electron bipolar-redox reaction mechanism of H₂TEPP.