Co‐Substitution Engineering Boosting the Kinetics and Stablity of VO₂ for Zn Ion Batteries

Abstract VO₂ is considered as one of the most likely cathode materials to be commercialized for large‐scale application in AZIBs and is at the forefront of aqueous batteries, but its lower electrical conductivity, slower Zn²⁺ mobility, as well as voltage degradation and structural collapse due to vanadium solubilization have limited its further development. Herein, a Co‐substitution engineering strategy is proposed, which is introducing heteroatom Co²⁺ doping substitution and oxygen vacancy substitution to stabilize structure and promote ionic/electronic conductivity, leading an enhanced Zn ion storage behavior. The Co‐substituted VO₂ (Co_0.03V_0.97O_2‐x, denote as O_v‐CoVO) is reported in this paper, Co‐substitution inhibits vanadium dissolution of VO₂ in AZIBs, even in the acetionitrile system. DFT calculations show that O_v‐CoVO has a more stable structure as well as a faster electronic/ionic conductivity. Consequently, the O_v‐CoVO||ZnOTF||Zn battery (aqueous) can deliver a remarkable capacity of 475 mAh g⁻¹ at 0.2 A g⁻¹ with 99.1% capacity retention after 200 cycles, still maintains excellent cycling stability in O_v‐CoVO||ZnTFSI||Zn (acetionitrile electrolyte) at 0.1 A g⁻¹. In addition, compared to VO₂, the charge transfer resistance and Zn²⁺ iffusion coefficient of O_v‐CoVO are significantly enhanced. This work broadens the scope for research cathode materials for high performance ZIBs.