p-π Conjugated quinone-amine polymer metal-free anode for high-performance reversible NH4+ charge storage

Abstract

Ammonium ion batteries (AIBs) have emerged as a promising technology for large-scale energy storage due to their low cost, high safety, and excellent electrochemical performance. However, the development of suitable anode materials has been a major challenge. In this study, we report a novel p-π conjugated cross-linked quinone-amine polymer (PQDAB) that exhibits remarkable capacity and cycling stability as an anode material for reversible storage of NH₄⁺. The p-π conjugated polymer framework creates an internal electric field at heteroatom sites, facilitating efficient electron transfer during charge and discharge processes, achieving a high capacity of 158.85mAh g⁻¹ at 0.5 A g⁻¹ and an excellent cycle stability of 77.1 % capacity retention over 16,000 cycles. Additionally, a “rocking-chair” AIB based on PQDAB//CuFe-PBA delivers a high capacity of 124.75mAh g⁻¹ at 0.5 A g⁻¹ and excellent cycle stability over 3,000 cycles at 3 A g⁻¹. Furthermore, we also explore the NH₄⁺ storage process through a novel reversibly carbonyl conversion reaction using in-situ/ex-situ characterization and theoretical simulation. Molecular Dynamics (MD) simulations reveal that the solvation layer structures of PQDAB in (NH₄)₂SO₄ electrolyte contribute to its superior stability. This work provides valuable insights for designing high-capacity and stable anode materials for AIBs.