Ultra-stable zinc-ion batteries by suppressing vanadium dissolution via multiple ion-bonded vanadate cathodes

Layered vanadate cathodes hold promise for aqueous zinc-ion batteries (AZIBs) owing to their multiple redox reactions as well as large interlayer space for Zn2+ storage. However, they are limited by vanadium dissolution during cycling, in association with severe capacity fade and unsatisfactory cyclic life. To address this challenge, we herein report a pre-inserted dual-cation vanadate (NaxZnyV3O8·nH2O) cathode, which combines the Zn2+-reinforced cathode structure with the Na+-enlarged lattice distance for fast and stable Zn2+ migration. Multiple ex situ analysis found that electrochemically active Zn3(OH)2V2O7·2H2O was generated after discharging, and this corresponds to the efficient suppression of vanadium dissolution by strong ionic bonding. As a result, a certain NaxZnyV3O8·nH2O cathode having a Na+ to Zn2+ ratio of 2:1 retains 99.6% of capacity after 418 cycles at 0.1 A g−1, 90.5% after 6000 cycles at 1.0 A g−1, and 96.7% after 9499 cycles at 10.0 A g−1. Our method paves a way for researchers to develop robust cathode materials for ultra-stable AZIBs.