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

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 degrees C for 4 h with a heating rate of 2 degrees C min(-1) and then carbonized in argon at 800 degrees C for 14 h with a heating rate of 2 degrees 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 degrees 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. (C) 2014 Elsevier B.V. All rights reserved.