“…[31] As shown in Figure S4e (Supporting Information), the binding energies at 284.6, 285.2, and 288.5 eV are attributed to the carbon coating of NVPF/C, which appear as the signals of C = C, C-C, and O-C = O bonds in the C 1s spectrum. [32] The Na, Mn, O, Ti, N, and P elements are included in the full survey spectrum of NMTP/C/NC. Figure 1e displays the four peaks of Ti 3+ and Ti 4+ ions in the Ti 2p spectrum, in which the peaks at 464.3 and 465.7 eV are assigned to 2p 1/2 and 2p 3/2 states of Ti 3+ ions, two peaks at 458.6 and 460.0 eV prove the existence of Ti 4+ ions.…”