Analogous Confinement Effect Enables High Stability and High Capacity Ammonium Storage in Polyaniline@Poly(o‐fluoroaniline)@Carbon Layer

Abstract Rechargeable aqueous ammonium ion (NH 4 + ) batteries have attracted much attention due to the unique properties of NH 4 + . Polyaniline (PA) with outstanding conductivity is a potential cathode material, but it can be oxidized to pernigraniline (PG) rapidly, resulting in its poor stability. In this study, polyaniline@poly( o ‐fluoroaniline)@carbon layer (PA@POFA@C) is prepared for excellent and durable NH 4 + storage. PA@POFA@C exhibits a high capacity of 208 mAh g −1 at 0.2 A g −1 and maintains 126 mAh g −1 at 10 A g −1 . More importantly, an excellent capacity retention rate of 88.24% is achieved after 2000 cycles with ≈100% coulombic efficiency. Spectroscopy studies suggest analogous confinement effect can effectively limit the escape of hydrogen in imine group, and form the hydrogen‐restricted region between the PA and POFA layer which can provide H + for the complete reduction of PG. Meanwhile, the hydrophobic effect of POFA effectively restrains the hydrolysis of PG. Interestingly, the introduction of C layer improves the hydrophilicity of electrode and shortens the activation process, serving as the outermost protective layer of the electrode. Finally, PA@POFA@C achieves desirable electrochemical performances with analogous confinement effect. This research provides ideas for the preparation of advanced polymer electrodes for aqueous NH 4 + batteries.