Ultra-fast activated NH4+-intercalated vanadium oxide cathode for high-performance aqueous zinc-ion batteries

Abstract

Vanadium-based oxides hold immense promise as cathode materials for aqueous zinc-ion batteries (AZIBs); however, their practical implementation faces a significant hurdle: a prolonged activation period is typically required to achieve peak performance. This activation process, which often requires hundreds of cycles, arises from the complex behavior of mixed-valence vanadium systems. In this paper, we propose a solution based on an elegant and simple electrical activation strategy. By applying a carefully designed precycling charging protocol to NH₄⁺-intercalated vanadium oxide (VON), we achieved activation speeds, reaching peak capacity within just several to 25 cycles—even under high current densities. The electrochemically activated material (E-VON) demonstrates performance metrics: delivering a high specific capacity of 359.1 mAh g⁻¹ at 0.1 A g⁻¹, maintaining a rate capability of 155.5 mAh g⁻¹ at 10 A g⁻¹, and showing cycling stability. The electrical activation process enhances ion transport within the VON structure and triggers a Zn²⁺/H⁺ coinsertion mechanism during cycling. This mechanism is intricately linked to the reversible formation and dissolution of a basic zinc sulfonate by-product, offering new insights into charge storage processes within vanadium-based AZIB cathodes. Our comprehensive characterization revealed how this activation strategy fundamentally transforms the structure and electrochemical behavior of materials, providing a practical pathway to overcome the longstanding limitations of traditional vanadium oxide cathodes. This study focuses on rapidly activating cathode materials, advancing the development of high-performance AZIBs.