Unraveling the Mechanism of Cooperative Redox Chemistry in High-Efficient Zn 2+ Storage of Vanadium Oxide Cathode.

The inferior capacity and cyclic durability of V 2 O 5 caused by inadequate active sites and sluggish kinetics are the main problems to encumber the widespread industrial applications of vanadium-zinc batteries (VZBs). Herein, a cooperative redox chemistry (CRC) as "electron carrier" is proposed to facilitate the electron-transfer by capturing/providing electrons for the redox of V 2 O 5 . The increased oxygen vacancies in V 2 O 5 provoked in situ by CRC offers numerous Zn 2+ storage sites and ion-diffusion paths and reduces the electrostatic interactions between vanadium-based cathode and intercalated Zn 2+ , which enhance Zn 2+ storage capability and structural stability. The feasibility of this strategy is fully verified by some CRCs. Noticeably, VZB with [Fe(CN) 6 ] 3- /[Fe(CN) 6 ] 4- as CRC displays conspicuous specific capacity (433.3 mAh g -1 ), ≈100% coulombic efficiency and superb cyclability (≈3500 cycles without capacity attenuation). Also, the mechanism and selection criteria of CRC are specifically unraveled in this work, which provides insightful perspectives for the development of high-efficiency energy-storage devices.