Synthesis and characterization of LiFePO4-carbon nanofiber-carbon nanotube composites prepared by electrospinning and thermal treatment as a cathode material for lithium-ion batteries

Binder-free LiFePO4-carbon nanofiber (CNF)-multiwalled carbon nanotube (MWCNT) composites were prepared by electrospinning and thermal treatment to form a freestanding conductive web that could be used directly as a battery cathode without addition of a conductive material and polymer binder. The thermal decomposition behavior of the electrospun LiFePO4 precursor-polyacrylonitrile (PAN) and LiFePO4 precursor-PAN-MWCNT composites before and after stabilization were studied with thermogravimetric analysis (TGA)/differential scanning calorimetry and TGA/differential thermal analysis, respectively. The structure, morphology, and carbon content of the LiFePO4-CNF and LiFePO4-CNF-MWCNT composites were determined by X-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy, scanning electron microscopy, and elemental analysis. The electrochemical properties of the LiFePO4-CNF and LiFePO4-CNF-MWCNT composite cathodes were measured by charge-discharge tests and electrochemical impedance spectroscopy. The synthesized composites with MWCNTs exhibited better rate performances and more stable cycle performances than the LiFePO4-CNF composites; this was due to the increase in electron transfer and lithium-ion diffusion within the composites loaded with MWCNTs. The composites containing 0.15 wt % MWCNTs delivered a proper initial discharge capacity of 156.7 mA h g(-1) at 0.5 C rate and a stable cycle ability on the basis of the weight of the active material, LiFePO4. (C) 2015 Wiley Periodicals, Inc.