Bimetallic-ion co-intercalation to stabilize vanadium-oxygen bonds towards high-performance aqueous zinc-ion storage

Aqueous zinc-ion batteries (AZIBs) have received increasing attention in large-scale energy storage systems because of their appealing features with respect to safety, cost, and scalability. Although vanadium oxides with different compositions demonstrate promising potential as cathodes for AZIBs, the narrow interlayer spacing, inferior electronic conductivity, and high dissolution in electrolyte seriously restrict their practical applications. Here we design an ingenious bimetallic-ion (Mg2+ and Al3+) co-intercalation strategy to boost the performance of AZIBs using V6O13<middle dot>1.31H2O (VOH). The bimetallic-ion intercalation expands the interlayer spacing, increases electronic conductivity, and more importantly stabilizes the vanadium-oxygen bond in VOH, thus promoting ion/electron transport kinetics and restraining vanadium oxide dissolution. As expected, MgAl-VOH cathodes deliver ultrahigh specific capacities of 524.9 and 275.6 mA h g-1 at current densities of 0.1 and 5 A g-1, respectively, comparable to the highest value reported for vanadium oxides. The underlying zinc-ion storage mechanism is unambiguously clarified with the aid of density functional theory calculations and in situ structural characterization. This work opens up a new avenue for boosting the performance of AZIBs by designing bimetallic-ion co-intercalated cathodes.