Abstract: Recently, ammonium vanadate (NH₄V₄O₁₀) has attracted much interest as an anode material for supercapacitors. However, ammonium vanadate-based anodes still face the problems of irreversible deamination and structural collapse during cycling in practical applications. Metal ions with electronegativity lower than vanadium can form stronger chemical bonds with oxygen, and such strong bonding can mitigate structural distortion, thus metal cation doping is beneficial for structural stabilization. In this study, potassium-doped ammonium vanadate (KNVO) nanowire arrays were grown on titanium wafers, and the morphology of NH₄V₄O₁₀ was modulated by varying the doping concentration of K⁺ to reduce the layer spacing and increase the oxygen vacancies to compensate for the decrease in the specific capacity due to the doping of metal ions. The prepared KNVO electrode exerted a high specific capacity of 756 F/g at 1 A/g current density and still had a high specific capacitance retention of 94.2% after 8000 Charge/Discharge cycles at 10 A/g among three electrode reaction system. In addition, DFT calculations showed that K-ion doping also led to an increase in oxygen vacancies, optimization of the electronic structure, and enhancement of Na⁺ mobility, and these vacancies not only provided additional electronic states and improved electron transport, but also enhanced the diffusion pathway of Na⁺, thus improving ionic conductivity. Therefore, the KNVO nanowires proved to be an ideal candidate for supercapacitor energy storage devices.