Toward Full Utilization and Stable Cycling of Polyaniline Cathode for Nonaqueous Rechargeable Batteries

Polyaniline is the most famous conducting polymer and also a promising organic cathode material for rechargeable batteries, however, it has demonstrated poor utilization of its theoretical capacity (294 mAh g−1) and inferior cycling stability in previous studies. Herein, for the first time, its fully reduced form, i.e., leucoemeraldine base (LB), is studied as an alternative to the commonly used emeraldine salt and base (ES and EB). For the three different forms, the precise structures are carefully determined, and the electrochemical performance are systematically investigated. Within 2.0−4.3 V, LB realizes almost full capacity utilization (92%) that is much superior to those of ES and EB. Within 2.0−4.2 V, it shows both high reversible capacity (277 mAh g−1) and cycling stability (84% capacity retention after 1000 cycles). The combination of electrochemical analysis, density functional theory calculation, and ex situ characterization reveals that the capacity utilization is positively associated with the pristine proportion of ─NH─ groups, and the capacity fading is caused by the irreversible electrochemical deprotonation at high charge potential. This work promotes both the electrochemical performance and mechanistic understanding of polyaniline to a new stage, towards practical application in energy storage devices as a low‐cost, high‐performance, sustainable, and green cathode material.