Nanographene-constructed carbon nanofibers grown on graphene sheets by chemical vapor deposition: high-performance anode materials for lithium ion batteries.

We report on the fabrication of 3D carbonaceous material composed of 1D carbon nanofibers (CNF) grown on 2D graphene sheets (GNS) via a CVD approach in a fluidized bed reactor. Nanographene-constructed carbon nanofibers contain many cavities, open tips, and graphene platelets with edges exposed, providing more extra space for Li(+) storage. More interestingly, nanochannels consisting of graphene platelets arrange almost perpendicularly to the fiber axis, which is favorable for lithium ion diffusion from different orientations. In addition, 3D interconnected architectures facilitate the collection and transport of electrons during the cycling process. As a result, the CNF/GNS hybrid material shows high reversible capacity (667 mAh/g), high-rate performance, and cycling stability, which is superior to those of pure graphene, natural graphite, and carbon nanotubes. The simple CVD approach offers a new pathway for large-scale production of novel hybrid carbon materials for energy storage.

Electrochemical formation of Mg-Li-Ca alloys by codeposition of Mg, Li and Ca from LiCl-KCl-MgCl2-CaCl2 melts.

This work presents electrochemical formation of Mg-Li-Ca alloys via codeposition of Mg, Li and Ca on a molybdenum electrode in KCl-LiCl-MgCl(2)-CaCl(2) melts at 943 K. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of calcium on pre-deposited magnesium leads to the formation of a liquid Mg-Ca alloy, and the succeeding underpotential deposition of lithium on pre-deposited Mg-Ca alloy leads to the formation of a liquid Mg-Li-Ca solution. Chronopotentiometric measurements indicated that the codepositon of Mg, Li and Ca occurs at current densities more negative than -0.31 A cm(-2) in LiCl-KCl-MgCl(2) (5 wt%) melts containing 1 wt% CaCl(2). Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li and Ca is -2.200 V, and the codeposition of Mg, Li and Ca is formed when the applied potentials are more negative than -2.200 V. X-Ray diffraction (XRD) indicated that Mg-Li-Ca alloys with different phases were formed via galvanostatic electrolysis. The microstructures of typical alpha and beta phases of Mg-Li-Ca alloys were characterized by optical microscope (OM) and scanning electron microscopy (SEM). The analysis of energy dispersive spectrometry (EDS) showed that the element Ca mainly distributes along grain boundary in Mg-Li-Ca alloys. The results of inductively coupled plasma analysis determined that the chemical compositions of Mg-Li-Ca alloys correspond with the phase structures of XRD patterns, and the lithium and calcium contents of Mg-Li-Ca alloys depend on the concentrations of MgCl(2) and CaCl(2).