Analogous Confinement Effect Enables High Stability and High Capacity Ammonium Storage in...

Rechargeable aqueous ammonium ion (NH₄ ⁺) batteries have attracted much attention due to the unique properties of NH₄ ⁺. 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 NH₄ ⁺ 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 NH₄ ⁺ batteries.