Sodium storage properties of Fe, Ni-bimetallic doped carbon-modified NaTi₂(PO₄)₃

NaTi₂(PO₄)₃ (NTP) is a material with a NASICON structure, a three-dimensional open type skeleton, and suitable negative voltage window, which is widely regarded as a magnetic anode material for aqueous sodium ion batteries (ASIBs). However, NTP’s intrinsically poor conductivity hampers their use in ASIBs. Herein, bimetallic doped carbon material was designed and combined with the sol–gel method to prepare NaTi₂(PO₄)₃–C–FeNi (NTP–C–FeNi) composite materials. This bimetallic doped carbon composite NTP material not only has a large specific surface area, but also effectively improves conductivity and promotes rapid migration of Na⁺. Following the rate performance test, NTP–C–FeNi retained a reversible capacity of 116.75 mAh·g⁻¹ at 0.1 A·g⁻¹, representing 95.9% of the first cycle capacity. After 500 cycles at 1.5 A·g⁻¹, the cycle fixity was 85.3%. The enhancement of electrochemical performance may owe to the widening of pathways and acceleration of Na⁺ insertion/extraction facilitated by FeNi–C doping, while the carbon coating effectively promotes electrode charge transfer. The results indicate that the bimetallic doped carbon composite NaTi₂(PO₄)₃ holds potential for practical applications in novel aqueous sodium ion battery systems.