Synergistic zinc-ion storage enabled by Cu ion in anthraquinone-preinserted vanadate: structural integrity and H+-promoted reversible phase conversion

Abstract

The reasonable modification of layered cathode materials and simple modulation of aqueous electrolytes have both been identified as effective strategies to expedite reaction kinetics, improve zinc storage capacity and maintain structural stability. Herein, (2-M-AQ)-VO nanobelts, formulated as (2-M-AQ)_0.1V₂O₅·0.4H₂O (2-M-AQ = 2-methylanthraquinone) with rich oxygen vacancies were obtained via a facile one-step solvothermal technique. Rietveld refinement demonstrated the successful intercalation of 2-M-AQ in the layered V₂O₅ with a large interlayer spacing of ∼13.5 Å. (2-M-AQ)-VO showed a good electrochemical performance in 3 M Zn(CF₃SO₃)₂ electrolyte. More importantly, in the electrolyte with Cu²⁺ additive, it exhibited a superior rate capability and remarkably enhanced long-term cyclability with a capacity retention exceeding 100% over 1000 cycles at 1 A g⁻¹. This is associated with the synergistic effect of cathode modification and anode protection induced by electrolyte modulation. Cu²⁺ in the electrolyte can enter the interlayer channel of the (2-M-AQ)-VO cathode to act as an auxiliary pillar to maintain its structural integrity and can also promote the insertion of H⁺ in (2-M-AQ)-VO, leading to a reversible phase conversion on the cathode side and in situ formation of a protective layer on the Zn anode side, as evidenced by density functional theory (DFT) calculations.