FeVO4⋅nH2O@rGO nanocomposite as high performance cathode materials for aqueous Zn-ion batteries

Aqueous zinc ion batteries (ZIBs) have recently attracted an increasing attention as an environmental friendliness, low cost and highly potential novel energy storage system. Although vanadium-based materials serve as a capable of arousing and holding the attention cathode materials for ZIBs, whereas low conductivity and confusing zinc ion storage mechanisms remain an obstacle. Herein, FeVO4⋅nH2O@rGO composite is employed to evaluate zinc ion storage capability as a cathode for the first time in 2 M Zn(TFSI)2 electrolyte. Benefiting from the large lattice spacing, dual electrochemical activity and fast electron transfer, the composite delivers excellent rate performance and long life cycle (the capacity retained ∼100 mAh g−1 at 1.0 A g−1 after 1000 cycle). In addition, the electrochemical performance of graphene-modified FeVO4⋅nH2O is superior to other precursors for comparison. Furthermore, the intercalated/de-intercalated mechanism of zinc ion is distinct from the traditional conversion reaction, which is confirmed by in-situ X-ray diffraction and various ex-situ techniques.