Stabilizing NH4V4O10 by Al-doping: boosting kinetics and ammonium retention for practical zinc-ion batteries

Abstract

Layered ammonium vanadate (NH₄V₄O₁₀) cathodes demonstrate high capacity and rapid ion transport due to their low molecular weight and open framework structure. However, practical application is hindered by strong electrostatic interactions between Zn²⁺ and V–O bonds, as well as structural instability arising from weak N–H⋯O bonding. To overcome these limitations, an Al³⁺ doping NH₄V₄O₁₀ (Al-NVO) cathode has been designed to stabilize the layered framework and achieve high-performance aqueous zinc-ion batteries (AZIBs). The incorporation of Al³⁺ ions and structural water molecules synergistically enhances Zn²⁺–V–O binding strength while constructing additional ion diffusion channels. Pre-intercalated Al³⁺ not only acts as pillars to enhance the stability of the layered structure but also suppresses irreversible deammoniation during cycling, thereby achieving exceptional long-term stability. Density functional theory (DFT) calculations reveal that Al-NVO optimizes the electron distribution and provides a low-energy-barrier pathway for Zn²⁺ migration (0.82 eV vs. 1.98 eV in NH₄V₄O₁₀). Benefiting from these merits, the Al-NVO cathode delivers a high specific capacity of 460 mAh g⁻¹ at 0.2 A g⁻¹ and 94.6% capacity retention after 2000 cycles at 5 A g⁻¹. Moreover, the Al-NVO-based pouch cell exhibits a capacity of 167 mAh g⁻¹ with 250-cycle stability, while a 0.6 Ah prototype battery sustains >300 h operation under deep cycling conditions, demonstrating practical feasibility for aqueous zinc-ion storage systems.