Synthesis of nanostructured fibers consisting of carbon coated Mn3O4 nanoparticles and their application in electrochemical capacitors.

Nanostructured composite fibers consisting of carbon coated Mn3O4 nanoparticles (Mn3O4@C) were prepared from thermal decomposition of manganese alginate fibers produced by wet-spinning technique, and investigated with SEM, TEM, XRD, nitrogen adsorption-desorption isotherms, and electrochemical tests toward energy storage. It is found that the as-obtained Mn304@C fibers consist of plenty of nano-sized Mn3O4 crystals with even diameter of 10-15 nm and carbon coating layer with a thickness of 1-2 nm. The composite fibers exhibit also a porous structure consisting of both micropores and mesopores. The electrochemical performances of Mn3O4@C fibers were examined by cyclic voltammetry and galvanostatic charge-discharge techniques. The results indicate that Mn3O4@C fibers possess a higher specific capacitance and superior rate capability when used as electrode materials for supercapacitor compared with commercial Mn3O@4. The improved performances of Mn3O4C fibers can be attributed to the nano-dimension of Mn3O4 particles, the thin carbon coating layer and the nanopores existing among Mn304@C nanoparticles.

Preparation and li storage properties of hierarchical porous carbon fibers derived from alginic acid.

One-dimensional (1D) hierarchical porous carbon fibers (HPCFs) have been prepared by controlled carbonization of alginic acid fibers and investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nitrogen adsorption-desorption isotherms, and electrochemical tests toward lithium storage. The as-obtained HPCFs consist of a 3D network of nanosized carbon particles with diameters less than 10 nm and exhibit a hierarchical porous architecture composed of both micropores and mesopores. Electrochemical measurements show that HPCFs exhibit excellent rate capability and capacity retention compared with commercial graphite when employed as anode materials for lithium-ion batteries. At the discharge/charge rate of 45 C, the reversible capacity of HPCFs is still as high as 80 mA h g(-1) even after 1500 cycles, which is about five times larger than that of commercial graphite anode. The much improved electrochemical performances could be attributed to the nanosized building blocks, the hierarchical porous structure, and the 1D morphology of HPCFs.