Self-Stacking Nano-Hexagonal Starfish-like V–W Bimetallic Oxide Film for Zn ²⁺ -Triggered Electrochromic Energy Storage

Electrochromic energy-storage devices are gaining popularity due to their visualized energy-storage level. However, the capacities are much lower than those of traditional energy-storage devices due to the characteristics and structural design of electrochromic materials for pursuing large optical modulation with small charge injection. Herein, a V-W bimetallic oxide film with a self-stacked hexagonal starfish-like structure is designed for Zn²⁺-triggered electrochromic energy storage. This unique structure holds the advantages of both a large active surface area and better structural stability. Therefore, a high areal capacity of 89.9 mAh·m^-2 at 0.2 mA·cm^-2 and good cycle stability (retaining 95.1% of its discharge capacity after 500 cycles) are achieved. Additionally, a self-operation mode electrochromic energy-storage platform is also presented by integrating the V-W bimetallic oxide film with a Zn anode, where it can be self-colored or bleached by connecting or disconnecting the two electrodes. The results demonstrate a promising application of V-W bimetallic oxide for a visual electrochromic energy-storage device with a self-operation mode.