Robust synthesis of a composite phase of copper vanadium oxide with enhanced performance for durable aqueous Zn-ion batteries

Abstract

Abstract Rechargeable aqueous Zn-ion batteries (AZIBs) have attracted much interest as next-generation power sources due to their economical, safe, and capacity superiorities. However, the cathodes used in AZIBs always suffer from sluggish kinetics, inducing inadequate rate performance and poor cycle ability. Pre-intercalating transition metal element in the cathode materials offers an effective strategy for improving diffusion kinetics of Zn2+ and thus the electrochemical activity. In this work, different proportions of Cu pre-intercalated V2O5 were synthesized to form a composite phase of Cu0.4V2O5 and VO2·nH2O nanosheets through the hydrothermal method. The reversible redox reaction of Cu2+ and Cu0, accompanied by the phase changes of copper vanadate and zinc vanadate, contributes to an excellent battery performance. When the molar ratio between Cu precursor and commercial V2O5 in the reaction solution is 1:2, the obtained material presents an outstanding electrochemical performance with the initial discharge capacity of 332 mAh g−1 at 0.2 A g−1. The enlarged lattice distance together with the high conductivity leads to a high Zn ions diffusion rate of 10−5 cm2 s−1. Even after 1,000 cycles at a current density of 2 A g−1, the capacity attenuation is only 0.035% per cycle, exhibiting distinctive activities toward AZIBs.