Synergistic deficiency and heterojunction engineering boosted VO2 redox kinetics for aqueous zinc-ion batteries with superior comprehensive performance

Aqueous zinc-ion batteries (ZIBs) are promising for cost-efficient and safe energy storage but are still hindered by the limiting comprehensive performance of cathode materials. Deficiency and heterojunction engineering are both highly accredited strategies for boosting the intrinsic ion/electron kinetics and structural stability of these materials, however, neither of above-mentioned strategies could achieve a satisfied effect due to their own limitations. Obviously, the fine combination of the advantages of deficiency and heterojunction engineering should be an effective way towards further improvement. As a proof of concept, here, we take VO2 as an example to construct a spongy three-dimensional (3D) VO2 composite with enriched oxygen vacancies and graphene-modified heterointerfaces (O-d-VO2-rG). The density functional theory (DFT) calculations confirm that oxygen vacancies could effectively modulate the Zn2+ adsorption energy resulting in reversible Zn2+ adsorption/desorption. Meanwhile, the graphene-modified heterointerface enables the rapid electron transfer. Impressively, O-d-VO2-rG delivers superior comprehensive performance with high capacity (376 mAh g(-1) at 0.1 A g(-1)), impressive rate capability (116 mAh g(-1) at 20 A g(-1)) and satisfactory cycling stability (88.6% capacity retention after 5000 cycles). This rational design by combining deficiency and heterojunction engineering opens up a method towards advanced electrode materials for superior comprehensive performance.