A π-Conjugated Polymer Anode With Railway-Like NH4 + Pathways for High-Rate Aqueous Ammonium-Ion Batteries.

Abstract

Aqueous ammonium-ion batteries (AAIBs) are promising energy storage systems, while the relatively large size and tetrahedral geometry of NH₄ ⁺ present challenges for its transport within electrodes. Herein, poly(5,8-diaza-1,4-naphthoquinone) (PANQ) has been synthesized to facilitate NH₄ ⁺ transport in AAIBs. The π-conjugated PANQ possesses a rigid, linear molecular structure. The straight intermolecular slits with uniformly distributed carbonyl sites form railway-like NH₄ ⁺ pathways, enabling rapid ion transport through the dynamic formation and disruption of hydrogen bonds. The PANQ electrode delivers a high capacity of 286.8 mAh g^-1 at 1 A g^-1 in a 2 mol L^-1 ammonium acetate electrolyte. Thanks to the rapid NH₄ ⁺ transport pathways, the electrode displays an excellent rate capability, retaining 161.7 mAh g^-1 at 80 A g^-1. Moreover, it displays exceptional cycling stability over 10 000 cycles at 20 A g^-1. The PANQ electrode was employed as the anode in a PANQ//NiCo-LDH AAIB (NiCo-LDH represents the Ni-Co layered double hydroxide cathode), retaining an energy density of 25.2 Wh kg^-1 even at an ultrahigh power density of 23 320.2 W kg^-1. This study provides a high-performance electrode candidate for AAIBs and a strategy for constructing rapid ion-transport pathways to enable efficient NH₄ ⁺ storage and superior electrochemical kinetics.