Ultra-high mass-loading V5+-VO2@PPy cathode for aqueous zinc-ion battery

The aqueous Zn-ion batteries (ZIBs) have attracted extensive attention for large-scale energy storage duo to the high safety and low cost of zinc anodes. However, most reported cathodes for aqueous ZIBs exhibit ordinary rate capability and are usually performed at a low mass-loading (<3 mg cm−2). Herein, we designed a one-step hydrothermal method that simultaneously realized conductive polypyrrole (PPy) coating and V5+/V4+ mixed valence state to synergistically improve the electronic conductivity of VO2 and guarantee its outstanding rate capability. Therefore, the Zn//V5+-VO2@PPy-180 battery demonstrates a promising rate performance by maintaining a high capacity of 345.5 mAh g−1 at 10 A g−1 current density, which is 83.6% of that at 0.2 A g−1. Remarkably, this battery also delivers excellent electrochemical properties with high mass-loading, which exhibits a long cycle life up to 1000 cycles at 2 A g−1 with 5 mg cm−2 mass-loading. And even when the mass-loading increase up to 20 mg cm−2, this battery can still deliver discharge capacity of 159.6 mAh g−1 for over 500 cycles with no obvious capacity fade. This work sheds light on the development of advanced cathode materials for ZIBs.