A Layered Zn_0.4VOPO₄·0.8H₂O Cathode for Robust and Stable Zn Ion Storage

Rechargeable aqueous zinc-ion batteries (ZIBs) have shown extraordinary potential in recent years due to their prominent superiority including resource sustainability, nontoxicity, excellent energy density of the zinc anode, and better safety. Nevertheless, the development of ZIBs is still hindered by the lack of suitable cathode materials possessing a high discharge voltage, sufficient specific energy density, and long-term cycle life. Herein, our work reported a layered phosphate, Zn0.4VOPO4·0.8H2O, by topochemical incorporation of zinc ions into the VOPO4·2H2O framework. The incorporation of zinc ions makes no change in the in-plane atomic arrangement and coordination environment. The resulting Zn0.4VOPO4·0.8H2O depicted a specific capacity of 161.4 mAh·g–1, a discharge plateau of 1.45 V, and excellent cycling stability over 1000 cycles. The energy density of our Zn//Zn0.4VOPO4·0.8H2O battery was as high as 219.8 Wh·kg–1 at a power density of 136.2 W·kg–1. A typical zinc ion intercalation/deintercalation mechanism has been revealed in this layered cathode. This work provides a layered hydrated phosphate as a robust cathode for ZIBs and also sheds light on modulation of multivalent-ion storage performance by a topochemical strategy in layered materials.