Hexagonal WO 3 /3D Porous Graphene as a Novel Zinc Intercalation Anode for Aqueous Zinc-Ion Batteries.

Aqueous Zn-ion batteries (ZIBs) have acquired great attention because of their high safety and environmentally friendly properties. However, the uncontrollable Zn dendrites and the irreversibility of electrodes seriously affect their practical application. Herein, hexagonal WO 3 /three-dimensional porous graphene (h-WO 3 /3DG) is investigated as an intercalation anode for ZIBs. As a result, the h-WO 3 /3DG//Zn half-battery shows excellent electrochemical performance with a high capacity of 115.6 mAh g -1 at 0.1 A g -1 and 89% capacity retention at 2.0 A g -1 after 10 000 cycles. The reason could be that the crystalline structure of WO 3 , which has hexagonal channels, with a diameter of 5.36 Å, much higher than the diameter of Zn 2+ (0.73 Å), accelerating the insertion/extraction of Zn ions. A zinc metal-free full battery using h-WO 3 /3DG as the anode and ZnMn 2 O 4 /carbon black (ZnMn 2 O 4 /CB) as the cathode is constructed, exhibiting an initial capacity of 66.8 mAh g -1 at 0.1 A g -1 corresponding to an energy density of 73.5 W h kg -1 (based on the total mass of anode and cathode-active materials) and a capacity retention of 76.6% after 1000 cycles at 0.5 A g -1 . This work demonstrates the high potential of hexagonal WO 3 as an advanced intercalation anode material for Zn metal-free batteries and may inspire new ideas for the development of other intercalation anode hosts for ZIBs.