A less-vanadium bimetallic-substituted polyanion cathode, Na₄VMn₀.₇Ni₀.₃(PO₄)₃@C (NVMNP@C), is developed for sodium-ion batteries (SIBs). This cathode exhibits excellent electrochemical performance at 25°C, delivering a rate capacity of 67 mA h g⁻¹ at 3 A g⁻¹ and maintaining 74.6% capacity after 4800 cycles at 2 A g⁻¹. It also demonstrates outstanding low-temperature performance, with a discharge capacity of 82 mA h g⁻¹ at 20 mA g⁻¹ and 60 mA h g⁻¹ at 400 mA g⁻¹ at -40°C, along with 90.4% capacity retention after 230 cycles at 100 mA g⁻¹. Density functional theory (DFT) calculations show that bimetallic substitution reduces the bandgap, enhances metal properties, and accelerates Na⁺/e⁻ transfer, improving electronic conductivity and kinetics. The NVMNP@C cathode also shows high reversibility and stability, with a 90.4% capacity retention after 230 cycles at 100 mA g⁻¹. The bimetallic substitution strategy significantly enhances the rate capability, long-term cyclability, and low-temperature adaptability of the cathode. The study provides a feasible pathway for high-performance SIB cathodes at low temperatures.A less-vanadium bimetallic-substituted polyanion cathode, Na₄VMn₀.₇Ni₀.₃(PO₄)₃@C (NVMNP@C), is developed for sodium-ion batteries (SIBs). This cathode exhibits excellent electrochemical performance at 25°C, delivering a rate capacity of 67 mA h g⁻¹ at 3 A g⁻¹ and maintaining 74.6% capacity after 4800 cycles at 2 A g⁻¹. It also demonstrates outstanding low-temperature performance, with a discharge capacity of 82 mA h g⁻¹ at 20 mA g⁻¹ and 60 mA h g⁻¹ at 400 mA g⁻¹ at -40°C, along with 90.4% capacity retention after 230 cycles at 100 mA g⁻¹. Density functional theory (DFT) calculations show that bimetallic substitution reduces the bandgap, enhances metal properties, and accelerates Na⁺/e⁻ transfer, improving electronic conductivity and kinetics. The NVMNP@C cathode also shows high reversibility and stability, with a 90.4% capacity retention after 230 cycles at 100 mA g⁻¹. The bimetallic substitution strategy significantly enhances the rate capability, long-term cyclability, and low-temperature adaptability of the cathode. The study provides a feasible pathway for high-performance SIB cathodes at low temperatures.