Synthesis of LiCoPO4/C nanocomposite fiber mats as free-standing cathode materials for lithium-ion batteries with improved electrochemical properties

Abstract

LiCoPO4/C nanocomposite fiber mats were successfully synthesized by electrospinning with a two-step heat treatment using nanostructured LiCoPO4 microparticles prepared by spray pyrolysis. The effects of the pre-oxidation temperature on the physical properties of the synthesized materials were studied. The fiber mats pre-oxidized at 425 °C and subsequently annealed at 700 °C in a N2 atmosphere contained 7 wt.% carbon and the small agglomerates of LiCoPO4 nanoparticle were evenly incorporated in carbon fibers with a few hundred nanometers. This fiber mat had a high specific surface area of 338 m2 g–1 and a large meso‑macropore volume of 0.71 cm3 g−1. It was directly used as a free-standing electrode without a binder and a current collector for lithium batteries. The cell exhibited an initial discharge capacity of 115 mAh g–1 at 0.1 C. The effects of SiO2 coating on the electrochemical properties of LiCoPO4/C nanocomposite fiber mats were further studied. Finally, the SiO2-coated LiCoPO4/C (15 wt.%) nanocomposite fiber mat with 2 wt.% SiO2 demonstrated superior capacity retention to uncoated ones, and the initial discharge capacities reached 126 mAh g–1 at 0.05 C and 100 mAh g–1 at 1 C, respectively.