To enhance the rate capability and cycling stability of the high-voltage cathode material LiNi_0.5Mn_1.5O₄ (LNMO), a V-Y co-doped LNMO cathode material was synthesized via the polymer soft-template method. The effects of V-Y co-doping on crystal structure, interfacial properties, and electrochemical performance were systematically investigated. The material was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) among other techniques, and the electrochemical properties were analyzed via galvanostatic charge-discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results indicate that V-Y co-doping induces the formation of disordered Fd3m phase by effectively regulating LNMO, facilitates the morphology evolution of spinel from regular octahedron to truncated octahedron, and constructs a coherent interface, which significantly enhances the lithium-ion diffusion rate and electronic conductivity. Moreover, V-Y co-doping reduces the Mn³⁺ content, suppresses Jahn-Teller effect and side reactions at the electrode/electrolyte interface, thereby enhancing the interfacial electrochemical stability. The 0.03V-Y sample (LiV_0.03Ni_0.47Y_0.01Mn_1.49O₄) delivers an initial discharge capacity of 132 mAh/g at a 0.1C rate, retaining 94.7% of its capacity after 200 cycles. It also exhibits superior rate capability at a high rate of 5C. This study provides a novel approach for constructing a coherent interface and synergistically optimizing the electrochemical performance of LNMO via dual-element doping.