Coupling High Rate Capability and High Capacity in an Intercalation-Type Sodium-Ion Hybrid Capacitor Anode Material of Hydrated Vanadate via Interlayer-Cation Engineering.

Abstract

Layered metal vanadates with intercalation pseudocapacitive behaviors show great promise for applications in sodium-ion hybrid capacitor anode materials due to their large interlayer distances, which benefit the fast Na+ solid-state diffusion. However, their charge storage capacity is significantly constrained by the limited available sites that allow the intercalation of Na+ ions. In this work, by engineering the interlayer cations, Ni0.12Zn0.2V2O5·1.07H2O is designed as a high-performance anode material in sodium-ion hybrid capacitors. The Ni/Zn codoping in the layered vanadate leads to the integration of high rate capability and high specific capacity. Specifically, the spacious interlayer spacing and the pillaring effects of Zn ions together lead to the high rate performance and decent cycling stability, while the redox reactions of the interlayer Ni ions efficiently upgrade the charge storage capacity of this layered material. Accordingly, this work offers a promising avenue to further optimizing the Na+ storage performance of layered vanadates via interlayer-cation engineering.