Effect of thermal treatment on the properties of electrospun LiFePO₄–carbon nanofiber composite cathode materials for lithium-ion batteries

Graphical abstract: The composites prepared with the thermal treatment process of stabilization at 280 °C for 4 h with a heating rate of 2 °C min⁻¹ in air followed by carbonization at 800 °C for 14 h with a heating rate of 2 °C min⁻¹ in argon exhibit the optimal electrochemical properties. - Highlights: • Binder-free LiFePO₄–CNF composite cathode materials are prepared. • The conductive carbon and LiFePO₄ formation take place simultaneously during thermal treatment. • The reaction behavior of the LiFePO₄ precursors during thermal treatment are investigated. • Different thermal treatment processes would generate different electrochemical performance. • Cycling performance and rate capability are improved with a suitable thermal treatment condition. - Abstract: Binder-free LiFePO₄–carbon nanofiber (LiFePO₄–CNF) composites as lithium-ion battery cathode materials are fabricated by electrospinning and subsequent thermal treatments. The thermal decomposition behavior of the electrospun LiFePO₄ precursor–polyacrylonitrile (LiFePO₄ precursor–PAN) nanofiber composites and the reaction of the LiFePO₄ precursors during thermal treatment are investigated. The effects of thermal treatment parameters such as heating rate, temperature, and duration for stabilization and carbonization on the microstructure, morphology, carbon content, crystal structure of the composites, and electrochemical performance of the resultant half-cell are also studied. When the electrospun LiFePO₄ precursor–PAN nanofiber composites are first stabilized in air at 280 °C for 4 h with a heating rate of 2 °C min⁻¹ and then carbonized in argon at 800 °C for 14 h with a heating rate of 2 °C min⁻¹, the obtained LiFePO₄–CNF composites exhibit optimal electrochemical properties in terms of a higher initial discharge capacity, more stable charge–discharge cycle behavior, and better rate performance. The initial discharge capacity of the composites is 146.3 mA h g⁻¹ at a rate of 0.5 C, while exhibiting a stable cycle performance up to 100 cycles. The results demonstrated that the LiFePO₄–CNF composite cathode materials could be a promising candidate for next-generation lithium-ion batteries and the thermal treatment process is a critical step to prepare LiFePO₄–CNF composites with optimal performances