The NH₄V₄O₁₀(NVO) cathode for aqueous zinc-ion batteries exhibits a high specific capacity due to its large interlayer spacing, but poor structural stability during charge and discharge processes leads to rapid capacity decay during cycling. Herein, K⁺-doped NH₄V₄O₁₀(KNVO) cathode materials with 3D flower-like micromorphology are synthesized via a facile one-step hydrothermal method. The 3D flower-like micromorphology facilitates the electrolyte infiltration and Zn²⁺ diffusion. K⁺ doping partially replaces $NH4+$, alleviating irreversible ammonium loss during the first cycle, thus enhancing material cyclic stability. Furthermore, the oxygen defects introduced by K⁺ doping facilitate electron and ion transfer, which enhances the rate performance of materials. The optimized K⁺ doping level of KNVO-2.5 cathode exhibits a high specific capacity (462.4 mAh·g^-1 at 0.5 A·g^-1), long cyclic life (with a specific capacity of 200.8 mAh·g^-1 and a capacity retention of 65.1% after 10 000 cycles at 15 A·g^-1), and impressive rate ability (156.6 mAh·g^-1 at 30 A·g^-1).