Extended Data Fig. 2: The surface composition analysis of DPM in the redox process.

a. Cyclic voltammetry (CV) curve of DPM in 0.1 M LiClO₄ at a scan rate of 50 mV s⁻¹. The curve shows the reversibility of the redox process with an oxidization peak at 0.12 V and a reduction peak at − 0.39 V. b. The X-ray photoelectron spectroscopy (XPS) survey scans of DPM in different states, which prove the matrix surface composition changes in the redox process. c, d. High-resolution Li 1s XPS spectra of DPM in the reduction state (c) and the oxidation state (d), which show the Li⁺ ions doping and dedoping during the redox processes. e, f. High-resolution N 1s XPS spectra of DPM in the reduction state (e) and the oxidation state (f). Four types of nitrogen environments are present in DPM. The higher peaks at 401.4 eV and 402.9 eV can be assigned to the positively charged –HN⁺– and bipolarons moieties⁴⁸. The positively charged N moieties are higher in the oxidation state, which indicates that the redox reaction have occurred on the DPM.