Integrated Network Cathodes by In Situ Phase Transition Break Diffusion Limitation for Zinc Ion Battery

The cathode materials set the limitation of aqueous zinc ion batteries (AZIBs) in capacity and restrict their development. Vanadium-based materials show unsatisfactory conductivity and strong interactions with Zn²⁺ as well as a narrow voltage window. Herein, an integrated network structure is obtained by modulating the voltage window to phase transition from VO₂ to H_XV₂O₅. This has multiple advantages: low crystallinity and abundant active sites; good electrolyte wetting; and two-electron transfer for high specific capacity. The AZIBs exhibit impressive rate performance (545 mAh g^-1 at 0.1 A g^-1 and 185 mAh g^-1 at 20 A g^-1) and cycling performance (179 mAh g^-1 after 15 000 cycles at 20 A g^-1), stable operation even at -20 °C (391 mAh g^-1 at 1 A g^-1, 97 mAh g^-1 at 10 A g^-1). AZIBs have high power density and high energy density based on the mass of cathode material (405 Wh kg^-1 at 74 W kg^-1 and 102 Wh kg^-1 at 11 127 W kg^-1). The pouch-type cell can run for over 500 h, has a maximum energy density of 45.5 Wh kg^-1. The phase transition mechanism and energy storage mechanism are identified, which is conducive to promoting the development of cathodes for AZIBs.