Enhanced electrochemical performance of aqueous Zn-ion batteries based on Na2V6O16·2H2O cathodes: insights from DFT and synchrotron X-ray analysis

Abstract

Aqueous zinc-ion batteries (AZIBs) have attracted significant attention because of their advantages such as high volumetric energy density, cost-effectiveness, and outstanding safety using an aqueous electrolyte. However, the main challenge in AZIBs originates from structural degradation at the cathode during repetitive charge/discharge cycles, which results in poor electrochemical performance. In this study, we present a novel material strategy for enhancing the electrochemical performance of AZIBs using a reliable cathode material, Na2V6O16<middle dot>2H2O (NaVO), produced via the pre-intercalation of Na ions into V2O5 through one-step sonochemical synthesis. NaVO enhances the structural stability and electrochemical performance of AZIBs. Therefore, a NaVO cathode paired with a Zn anode (NaVO//Zn) exhibits a capacity of 126.3 mA h g-1 at a high current density of 10 A g-1 and maintains a capacity retention rate of 91.8% after 10 000 cycles, thereby demonstrating exceptional long-term cycling stability. Density functional theory calculations (DFT) combined with in situ synchrotron-based X-ray techniques provide scientific insights into the underlying mechanism of the enhanced electrochemical performance related to the structural stability of NaVO.