Polyaniline-coated NH4+ pre-intercalated MoO3 nanobelts for high performance aqueous zinc ion batteries

Abstract

Zn anodes often suffer from drawbacks like limited cycling steadiness and terrible rate capability in rechargeable aqueous zinc-ion batteries (AZIBs), primarily linked to the formation of zinc dendrites, inefficient stripping/plating behavior, and gas generation during cycling. To overcome these limitations, we introduce a novel tactic of “rocking-chair” type AZIBs utilizing α-MoO₃ as a non-zinc anode material. However, the practical application of α-MoO₃ is hindered by poor electronic conductivity, sluggish Zn²⁺ diffusion kinetics, and structural instability during cycling, leading to rapid capacity degradation. In this regard, MoO₃ nanobelts intercalated with NH₄⁺ ions and coated with polyaniline (referred to as PANI@(NH₄)_xMoO₃) are adopted as the intercalation-type anode in AZIBs in this work. The integration of NH₄⁺ serves to widen the interlayer distance and stabilize the structure, effectively relieving lattice stress and promoting Zn²⁺ mobility. Meanwhile, the PANI coating enhances the electrical behavior of MoO₃ and inhibits molybdenum dissolution. Computational analysis leveraging density functional theory confirms that NH₄⁺ incorporation and PANI wrapping narrows the band gap and adjusts the electronic configuration of MoO₃, highly boosting electrochemical dynamics. As expected, the optimized 0.6-PANI@(NH₄)_xMoO₃ achieves a high reversible capacity of 342.1 mAh g⁻¹ after 100 cycles at 0.4 A g⁻¹ and showcases a satisfied energy density of 133.9 Wh kg⁻¹ when assembled as anode for a full cell.