Quicker and More Zn²⁺ Storage Predominantly from the Interface

TLDR

Aqueous zinc‑ion batteries are highly desirable for large‑scale energy storage due to low cost and high safety, yet achieving simultaneously high energy and power densities remains challenging. The authors construct a VOx sub‑nanometer cluster/reduced graphene oxide cathode featuring interfacial V–O–C bonds. They reveal that Zn²⁺ ions are stored predominantly at the VOx/rGO interface, causing anomalous valence changes and enabling decoupled electron/Zn²⁺ transport, while reversible interface reconstruction allows more ion storage than the bulk. This interface‑dominated storage delivers ultrahigh rate capability (174.4 mAh g⁻¹ at 100 A g⁻¹) and high capacity (443 mAh g⁻¹ at 100 mA g⁻¹), surpassing theoretical limits of each component, and offers a promising route to high‑energy and high‑power devices.

Abstract

Abstract Aqueous zinc‐ion batteries are highly desirable for large‐scale energy storage because of their low cost and high‐level safety. However, achieving high energy and high power densities simultaneously is challenging. Herein, a VO x sub‐nanometer cluster/reduced graphene oxide (rGO) cathode material composed of interfacial VOC bonds is artificially constructed. Therein, a new mechanism is revealed, where Zn 2+ ions are predominantly stored at the interface between VO x and rGO, which causes anomalous valence changes compared to conventional mechanisms and exploits the storage ability of non‐energy‐storing active yet highly conductive rGO. Further, this interface‐dominated storage triggers decoupled transport of electrons/Zn 2+ ions, and the reversible destruction/reconstruction allows the interface to store more ions than the bulk. Finally, an ultrahigh rate capability (174.4 mAh g −1 at 100 A g −1 , i.e., capacity retention of 39.4% for a 1000‐fold increase in current density) and a high capacity (443 mAh g −1 at 100 mA g −1 , exceeding the theoretical capacities of each interfacial component) are achieved. Such interface‐dominated storage is an exciting way to build high‐energy‐ and high‐power‐density devices.