Wan Lin Wang

Electrochemical Performance of Lithium Iron Phosphate by Adding Graphite Nanofiber for Lithium Ion Batteries

Olivine type LiFePO4 cathode material was synthesized by solid-state reaction method including one-step heat treatment. To improve the electrochemical characteristics, graphite nanofiber (GNF) was added into LiFePO 4 cathode material. The structure and morphological performance of LiFePO4 were investigated by X-ray diffraction (XRD); and a field emission-scanning electron microscope (FE-SEM). The synthesized LiFePO 4 has an olivine structure with no impurity, and the average particle size of LiFePO4 is about 200~300 nm. With graphite nanofiber added, the discharge capacity increased from 113.43 mAh/g to 155.63 mAh/g at a current density of 0.1 mA/cm 2 . The resistance was also significantly decreased by the added graphite nanofiber.

Increases in solar conversion efficiencies of the ZrO2 nanofiber-doped TiO2 photoelectrode for dye-sensitized solar cells

In this paper, in order to improve the efficiency of dye-sensitized solar cells, we introduced zirconia [ZrO2] nanofibers into a mesoporous titania [TiO2] photoelectrode. The photoelectrode consists of a few weight percent of ZrO2 nanofibers and a mesoporous TiO2 powder. The mixed ZrO2 nanofibers and the mesoporous TiO2 powder possessed a larger surface area than the corresponding mesoporous TiO2 powder. The optimum ratio of the ZrO2 nanofiber was 5 wt.%. The 5 wt.% ZrO2-mixed device could get a short-circuit photocurrent density of 15.9 mA/cm2, an open-circuit photovoltage of 0.69 V, a fill factor of 0.60, and a light-to-electricity conversion efficiency of 6.5% under irradiation of AM 1.5 (100 mW/cm2).

Enhanced Reaction Kinetic of Fe 3 O 4 -graphite Nanofiber Composite Electrode for Lithium Ion Batteries

A -graphite nanofiber composite for use as an anode material was successfully synthesized by calcining and graphite nanofiber (GNF) together in a atmosphere. Using this -GNF composite in a lithium ion battery resulted in a higher lithium storage capacity than that obtained using -graphite (-G). The -GNF (10 wt%) electrode exhibited a higher lithium ion diffusion coefficient () than did the -G (10%) (). At a current density of , the -GNF (10 wt%) anode showed a higher reversible capacity () than did the -G (10%) anode (). Moreover, the electrodes showed good cycling performance without the addition of a conductive material.

COATING THE CONDUCTIVITY MATERIALS TO IMPROVING THE ELECTROCHEMICAL PROPERTIES OF LiFePO4

LiFePO4 cathode materials were prepared by a solid-state method followed by one-step heat treatment. To improve the electrochemical properties of the LiFePO4, acetylene black (AB), citric acid (CA), and pyrene are added as carbon source, respectively. The cyclic voltammetry (CV), AC impedance and galvanostatic charge/discharge testing results showed that using the LiFePO4-C composite such as the AB carbon source exhibits higher discharge capacity and stability than the other composite. Synthesized LiFePO4-C/Li cells (with AB) showed that initial discharge capacity was 140.65 mA h g-1 and at the 2nd cycle were 145.87 mA h g-1, respectively. Morphology and electrochemical performance of the LiFePO4 cathode materials were investigated. Furthermore, the cell was subjected to current density studies (0.1 mA cm-2) that suggested excellent capacity retention of the cell at 25°C.