Synergistic internal and external modification of TiNb₂O₇ through ion doping and interfacial engineering for high-performance lithium-ion batteries

TNO has attracted much attention due to its high theoretical capacity, but the poor electronic conductivity hinders its application in high-rate/low-temperature devices. In this study, unique porous morphology and V³⁺-doped TiNb₂O₇ microspheres with excellent low-temperature electrochemical properties are successfully synthesized by a simple solvothermal method. The porous morphology of the TiNb₂O₇ microspheres increases their contact area with the electrolyte. The V³⁺ doping increases the number of oxygen vacancies inside and reduces the energy gap. The partial coating of the nitrogen containing carbon layer constructs the conductive skeleton, which improves the electrical conductivity and electrochemical performances from the internal and external levels of the particles. The specific capacities of the material reach 276.85 mAh g⁻¹ at 0.5C and 193.15 mAh g⁻¹ at 15C, respectively. In addition, after 2000 cycles at 5C and 10C, the capacity remains 200.92 mAh g⁻¹ and 176.86 mAh g⁻¹, respectively. The assembled LFP//3V-TNO@NC full cell exhibits168.96mAh g-¹ at 5C after 2000 cycles, and at −20 °C, it still shows 230.6 mAh g⁻¹ after 200 cycles at 0.5C. In conclusion, our study provides a simple method for synergistic internal and external improvement of the electrical conductivity and low-temperature properties of transition metal oxides and helps to promote the application and development of energy storage.