Cobalt-ion-doped vanadium-based cathodes with multiphase coexistence for high-performance aqueous zinc-ion batteries

This paper proposes a strategy of oxalic acid-regulated cobalt ion doping to construct a multi-phase coexisting vanadium-based cathode material (CoVO) through a one-step hydrothermal method, and systematically studies its influence on the electrochemical performance of aqueous zinc-ion batteries. The study systematically investigates the effects of oxalic acid concentration on the phase composition, valence state distribution of vanadium, and oxygen defect concentration of CoVO, revealing the enhancement mechanism of electrochemical performance by the synergistic effect of multiphase, oxygen deficiency and Co ions. The experimental results show that the optimized CoVO-3 sample achieves a high specific capacity of 317 mAh g −1 at a current density of 0.1 A g −1 and maintains a capacity retention rate of 89.71 % after 2000 cycles at 5 A g −1 . The rational design in multi-phase interface, enhancement of electronic conductivity due to Co 2+ doping and pseudocapacitive energy storage dominating mechanism are responsible for the superior activity of CoVO-3 sample. Besides, the kinetic results prove that multi - phase interface and oxygen defects will enhance rapidly insertion/extraction kinetics of Zn 2+ from the synergistic effect. In this paper, we present an alternative design strategy to create high-performance and long-cycle-stable cathode materials for aqueous zinc ion batteries.