Preparation of 0.4Li(2)MnO(3)center dot 0.6LiNi(1/3)Co(1/3)Mn(1/3)O(2) with tunable morphologies via polyacrylonitrile as a template and applications in lithium-ion batteries

摘要

Samples of 0.4Li(2)MnO(3)center dot 0.6LiNi(1/3)Co(1/3)Mn(1/3)O(2) (LMO) with tunable morphologies were synthesized via polyacrylonitrile (PAN) as a template. The starting PAN/N, N-dimethylformamide (DMF) ratios, including 1:9, 1:10, 1:12, and 1:14, were optimized for the fiber morphologies and electrochemical performance. Through electrospinning, metal salts were well dispersed in the PAN fibers. The crystal structure and morphologies of the PAN/LMO fibers were characterized by X-ray diffraction, scanning electron microscopy, and thermal analysis. Along with the decrease in the concentration of PAN in the precursor, the diameters of the PAN/LMO fibers decreased. On the other hand, at the highest and lowest concentrations, 1:9 and 1:14, of PAN with DMF, micrometer PAN fibers were electrospun, whereas ratios of PAN to DMF of 1:10 and 1:12 resulted in the electrospinning of millimeter-long fibers of PAN. In the interface of PAN and metal salts, LMOs were grown and accompanied the decomposition of PAN, and the crystal morphologies of LMO quite depended on the diameter and length of the PAN/LMO nanofibers. During heat treatment, the morphologies of the PAN fibers controlled the removal of small molecules and the crystal morphologies of LMOs. The charge/discharge results indicate that LMO with a tubular structure delivered a capacity of 262.3 mAh/g at a cutoff voltage of 2.5-4.8 V at a 0.1 C rate. Benefitting from a unique hollow and nanocrystalline architecture, it also exhibited good rate and cycling performances. (C) 2015 Wiley Periodicals, Inc.