A synergistic effect between layer surface configurations and K ions of potassium vanadate nanowires for enhanced energy storage performance

Abstract

Layered metal vanadates, especially alkali metal vanadates, have been extensively studied in energy storage. Generally, vanadates exhibit more stable electrochemical performance than pristine vanadium oxides, and different vanadates also vary in the performance. However, the detailed mechanisms of the variation in the performance of vanadates and vanadium oxides are poorly explored. Here we choose and construct three typical layered vanadium-based nanowires (V₂O₅, KV₃O₈ and K_0.25V₂O₅), and investigate the origin of the enhanced electrochemical performance of the potassium vanadates compared to V₂O₅, based on crystal structure analysis, electrochemical tests, ex situ ICP measurements and in situ XRD detections. We demonstrate a synergistic effect between layer surface configurations and K ions of potassium vanadate nanowires, which leads to the great improvement in electrochemical stability of K_0.25V₂O₅. The layer surface configuration of K_0.25V₂O₅ only consists of single-connected oxygen atoms, which provides strong interaction with the K ions. And the stabilized K ions act as “pillars” between interlayers to protect the layered structures from collapse in the charge/discharge process. This work provides a further insight into alkali metal vanadates, and benefits the design of ideal electrode materials in the energy storage field.