a, Schematical illustration of the lithium storage processes. Owing to the complexity of conducting polymer resonance and lithium-ion storage mechanisms, coupled with the uncertainty regarding the positions of counter-ions, only a schematic representation of one possible resonance pathway was provided here. The pristine PBFDO, with an n-doping level of around 90%, was first discharged to 1.5 V by lithium-ion uptake. During the subsequent charge process, lithium ions were extracted, while approximately half of protons were also removed, leaving the remaining protons preserved within PBFDO, which also contributed to PBFDO maintaining its n-doped state. Afterward, PBFDO experienced reversible electrochemical reactions, with some protonated carbonyl groups persisting, leading to a reversible capacity of 230.4 mAh g−1. b, XPS spectra of the PBFDO cathode at different charge/discharge states. c, Voltage profiles of the PBFDO cathode at 50 mA g−1 with marked voltages for the FTIR tests. d, FTIR spectra of the PBFDO cathode at different charge/discharge states as indicated in c. e, In situ Raman spectra of the PBFDO cathodes during charge/discharge processes.