Two lithium iron oxides have been synthesized at low temperatures by the conventional solid-state method. Orthorhombic LiFeO2 has been synthesized using LiOH and γ-FeOOH at 150°C was composed of orthorhombic LiFeO2 and small amount of spinel LiFe5O8 phases. A Li/LiFeO2 cell showed not only a fairly high initial discharge capacity of over 150 mAh g−1 but also a good cycle retention rate at room temperature. It was found that the orthorhombic phase of the LiFeO2 underwent a structural change to the LiFe5O8 spinel phase in the first cycle. Especially, it showed a severe structural change during the first discharge process, which might be the main reason for the capacity loss of the Li/LiFeO2 system. An amorphous-like LixFeyOz has been synthesized using LiOH and α-FeOOH at 200°C consisted of three kinds of structures, LiFe5O8, Li5FeO4, and a trace of cubic α-LiFeO2 A Li/LixFeyOz cell showed a very high initial discharge capacity (215 mAh g−l) as well as an excellent cycle retention rate (95%) from the 11th to the 50th cycle. It was found that LixFeyOz material was transformed into the spinel LiFe5O8 and tetragonal β-LiFeO2 phases after long-term cycling.
This report describes that the influence of the gas supply on the decrease of impurities and surface morphology of δ-Bi2O3 thin film by means of chemical vapor deposition under atmospheric pressure using BiI3 and O2 gas as starting materials. X-ray photoelectron spectroscopy and Energy dispersive X-ray spectrometer analyses revealed the remarkable decrease of impurities from the deposited film when put close to 60 mm against the O2 gas line. By changing growth position, the incorporation of the iodine was completely suppressed. Obtained iodine-free δ-Bi2O3 thin film was not flat than that of the previous report, but also had a rather irregular shape and the average grain size was a few micrometers.
Photovoltaic performance of dye-sensitized solar cells (DSSCs) based on a nanocrystalline TiO2 electrode have been measured in terms of I-V characteristics under standard AM 1.5 G irradiation and spectral response (incident photon to current conversion efficiency, IPCE) of the cells. The performance of DSSCs depended remarkably on the measurement conditions. It has been observed that the conventional characterization conditions for photovoltaic performance of crystalline and amorphus silicon solar cells are not suitable for characterization of DSSCs. In this paper, we suggest suitable characterization conditions, which are to be standard measurement conditions in the near future, for the photovoltaic performance of DSSCs.
We have succeeded in producing a V-Sn alloy thin film as an anode material for lithium-ion batteries using sputtering method. The V-Sn alloy target was prepared by thermic process. The obtained V-Sn alloy targets are mainly composed of V2Sn3 phase containing tin impurity, but these alloy thin films are composed of V-Sn amorphous phase and Sn phase. The half-cell tests revealed that the cycle performance of the V-Sn thin film electrode was significantly improved by the annealing the target. The V-Sn thin film electrode showed an initial rechargeable capacity of 700 Ah /kg, which was reduced to 558 Ah /kg even after 300 cycles.
Electric double layer capacitors were prepared using acetylene black and ketjen black as electrode materials with different types of pore structures. From the results of cyclic voltammetry, it is clear that EDLC based on ketjen black has better capacitive behavior. The specific capacitance of about 55.8 F/g using the polarizable electrodes with ketjen black was obtained. Moreover, space charge distributions of EDLC based on polarizable electrodes were investigated by a pulsed electro acoustic method. The polarizable electrode with ketjen black has higher charge density. It can be found that ketjen black plays an essential role in the improvement of capacitance in EDLC.