Boosting Zn²⁺ Storage Kinetics by K-Doping of Sodium Vanadate for Zinc-Ion Batteries

Na₅V₁₂O₃₂ is an attractive cathode candidate for aqueous zinc-ion batteries (AZIBs) by virtue of its low-cost and high specific capacity (>300 mAh g^-1). However, its intrinsically inferior electronic conductivity and structural instability result in an unfavorable rate performance and cyclability. Herein, K-doped Na₅V₁₂O₃₂ (KNVO) was developed to promote its ionic/electronic migration, and thus enhance the Zn²⁺ storage capability. The as-produced KNVO displays a superior capacity of 353.5 mAh g^-1 at 0.1 A g^-1 and an excellent retentive capacity of 231.8 mAh g^-1 after 1000 cycles at 5 A g^-1. Even under a high mass of 5.3 mg cm^-2, the KNVO cathode can still maintain a capacity of 220.5 mAh g^-1 at 0.1 A g^-1 and outstanding cyclability without apparent capacity decay after 2000 cycles. In addition, the Zn²⁺ storage kinetics of the KNVO cathode is investigated through multiple analyses.