Effect of calcination temperature on the microstructure and electrochemical performance of NaFePO4/C cathode materials for sodium-ion battery

Abstract

Among the various types of cathode materials for sodium-ion batteries, NaFePO₄ has attracted much attention due to its high theoretical capacity (155 mAh g⁻¹), low cost, and high structural stability. However, the thermodynamically stable maricite form of NaFePO₄ is regarded as electrochemically inactive because of its closed framework, which lacks pathways for Na⁺ diffusion. While numerous modification techniques exist, many require substantial energy input. In this study, the NaFePO₄/C cathode materials with amorphous and maricite phases were in situ constructed through an extremely simple sol–gel method at different calcination temperatures without incorporating other complicated technology. All of the microstructure, phase components, particle size, and specific surface of NaFePO₄/C cathode materials were well controlled by this one-step method. Among them, the NaFePO₄/C with amorphous and maricite phases calcined at 450 °C had an excellent electrochemical performance, the discharge specific capacity maintained at 123.6 mAh g⁻¹ after 10 cycles and becomes stable, and the capacity decay rate was only 4.00% after 100 cycles at 0.1 C at room temperature, Na⁺ diffusion coefficient of 1.026 × 10^–17 cm² s⁻¹, and charge transfer resistance of 998.6 Ω.