Synthesis and Electrochemical Properties of Nanostructured LiCoO2 Fibers as Cathode Materials for Lithium-Ion Batteries

Abstract

Nanostructured LiCoO₂ fibers were prepared by the sol−gel related electrospinning technique using metal acetate and citric acid as starting materials. The transformation from the xerogel fibers to the LiCoO₂ fibers and the nanostructure of LiCoO₂ fibers have been investigated in detail. The LiCoO₂ fibers with 500 nm to 2 μm in diameter were composed of polycrystalline nanoparticles in sizes of 20−35 nm. Cyclic voltammetry and charge−discharge experiments were applied to characterize the electrochemical properties of the fibers as cathode materials for lithium-ion batteries. The cyclic voltammogram curves indicated faster diffusion and migration of Li⁺ cations in the nanostructured LiCoO₂ fiber electrode. In the first charge−discharge process, the LiCoO₂ fibers showed the initial charge and discharge capacities of 216 and 182 (mA·h)/g, respectively. After the 20th cycle, the discharge capacity decreased to 123 (mA·h)/g. The X-ray diffraction and high-resolution transmission electron microscopy analyses indicated that the large loss of capacity of fiber electrode during the charge−discharge process might mainly result from the dissolution of cobalt and lithium cations escaping from LiCoO₂ to form the crystalline Li₂CO₃ and CoF₂ impurities.