Na Ions Doped Fe₂VO₄ Cathode for High Performance Aqueous Zinc-ion Batteries

Aqueous zinc ion batteries are thought to be a new generation of secondary batteries that will replace lithium-ion batteries due to their great safety and inexpensive cost. In the cathode materials of aqueous zinc ion batteries with long life and high capacity, abundant active sites and crystal structure stability play an important role. In the present work, the strategy of Na⁺ intercalation of Fe₂VO₄ (FVO) is proposed, aiming at the insertion of Na⁺, which not only enriches the active sites, but also sodium and iron ions act as guest species with the negatively charged VOx lattice to provide strong electrostatic attraction to stabilize the lamellar structure. In terms of electrochemical performance, the discharge specific capacity is 370 mAh g^-1 at a current density of 0.1 A g^-1, and when the current density is arising 5 A g^-1, the specific capacity also reaches 200 mAh g^-1 after cycling 2000 with a capacity retention of 99 %, which is better than the electrochemical performance of Fe₂VO₄ (FVO) alone at 50 mAh g^-1. The superior electrochemical performance proves that FVO-Na is an ideal cathode material for zinc ion batteries.