Novel Polymer/Barium Intercalated Vanadium Pentoxide with Expanded Interlayer Spacing as High-Rate and Durable Cathode for Aqueous Zinc-Ion Batteries.

Rechargeable aqueous zinc-ion batteries (AZIBs) exhibit great potential in large-scale energy storage systems. However, limited reaction kinetics and poor long-cycle stability restrict the application of vanadium oxide cathode materials. Herein, we designed and successfully synthesized a novel composite material with polyethylene glycol (PEG) and barium cation (Ba2+) preintercalated between the layers of vanadium pentoxide, denoted as PEG-Ba0.38V2O5·nH2O (PEG-BVO), as a cathode material of AZIBs. The optimized PEG-BVO material shows a uniform nanobelt-like structure with the expanded interlayer spacing of 1.07 nm, significantly promoting the transport kinetics of zinc ions. The theoretical calculation results unravel that an interlayer spacing of 1.07 nm may be at the most stable state for this layered composite structure, ensuring a robust architecture for rapid reversible (de)intercalation of zinc ions. As a result, the PEG-BVO electrode (with a large mass loading of 4 mg cm-2) exhibits an outstanding electrochemical performance including a high specific capacity (345 mAh g-1 at 0.1 A g-1), decent rate capability (up to 175 mAh g-1 at 10 A g-1), and long-term cycling stability (98.8% capacity retention upon 4000 cycles at 6 A g-1). Our discovery provides a new guest preinsertion strategy to construct a robust layered vanadium-based electrode with the expanded interlayer spacing, and the as-prepared PEG-Ba0.38V2O5·nH2O shows great potential as a high-rate positive electrode for AZIBs.