The paper presents a novel bimetallic-substituted polyanion cathode material, Na4VMo0.7Ni0.3(PO4)3@C (NVMNP@C), designed for sodium-ion batteries (SIBs). This material is an improvement over traditional vanadium-based polyanions, which have limited electronic conductivity and high raw material costs. The NVMNP@C cathode exhibits excellent electrochemical performance at 25°C, with a rate capacity of 67 mA g−1 at 3 A g−1 and long-term cyclability of 74.6% after 4800 cycles at 2 A g−1. Additionally, it demonstrates superior low-temperature adaptability, achieving a high discharge capacity of 82 mA g−1 at 20 mA g−1 and a rate capacity of 60 mA g−1 at 400 mA g−1, with 90.4% capacity retention after 230 cycles at 100 mA g−1 at −40°C. The enhanced performance is attributed to the bimetallic substitution, which reduces the bandgap, improves metal properties, and accelerates Na+/e− transfer, leading to a more robust structure. Density functional theory (DFT) calculations support these findings, confirming the effectiveness of the bimetallic substitution in improving the cathode's performance. This work provides a feasible pathway for high-performance SIB cathodes at low temperatures.The paper presents a novel bimetallic-substituted polyanion cathode material, Na4VMo0.7Ni0.3(PO4)3@C (NVMNP@C), designed for sodium-ion batteries (SIBs). This material is an improvement over traditional vanadium-based polyanions, which have limited electronic conductivity and high raw material costs. The NVMNP@C cathode exhibits excellent electrochemical performance at 25°C, with a rate capacity of 67 mA g−1 at 3 A g−1 and long-term cyclability of 74.6% after 4800 cycles at 2 A g−1. Additionally, it demonstrates superior low-temperature adaptability, achieving a high discharge capacity of 82 mA g−1 at 20 mA g−1 and a rate capacity of 60 mA g−1 at 400 mA g−1, with 90.4% capacity retention after 230 cycles at 100 mA g−1 at −40°C. The enhanced performance is attributed to the bimetallic substitution, which reduces the bandgap, improves metal properties, and accelerates Na+/e− transfer, leading to a more robust structure. Density functional theory (DFT) calculations support these findings, confirming the effectiveness of the bimetallic substitution in improving the cathode's performance. This work provides a feasible pathway for high-performance SIB cathodes at low temperatures.