This paper reviews the electrolytes in view of their charge-discharge characteristics, electrochemical and physical properties for the applications to secondary lithium batteries in about past decade. Also this paper mainly encompasses on the lithium organoborates and fluorinated organic solvents for electrolytes of lithium batteries.
Ionic liquids, having reasonably low volatility, flame retardancy, and high ionic conductivity, have great potential to be safe alternatives to electrolyte solutions. Most attractive point of these ionic liquids, is variety of structural design, implying unlimited variation of properties and functions of the salts. Their basic properties and recent developments for electrochemistry are reviewed.
This review paper describes the device performance and light-emission mechanism for phosphorescent organic light-emitting devices (OLEDs), as well as energy transfer processes in phosphorescent host-guest systems. The characteristics of a green phosphorescent OLED, with representative guest and host materials, are presented and its working mechanism is discussed. To improve the emission efficiency, the confinement of triplet energy in the guest molecules is demonstrated for a blue phosphorescent OLED. Photoluminescence phenomena in phosphorescent host-guest systems are presented, and the energy transfers between the host and guest molecules are also discussed.
One of the main causes of the deterioration of lead-acid batteries has been confirmed as the sulfation of the negative the electrodes. The recovery of lead acid batteries from sulfation has been demonstrated by using several additives proposed by the authors et al. From electrochemical investigation, it was found that one of the main effects of additives is increasing the hydrogen overvoltage on the negative electrodes of the batteries. Several kinds of additives have been tested for commercially available lead-acid batteries. The increase in the internal resistance of the lead-acid battery during charge-discharge cycles coincided with a decrease in the discharge capacity of the tested battery, so the internal resistance can be a good index of deterioration of the battery. The colloidal solution of electrolyzed fine-carbon particles, Nanoca, was the most promising to reactivate the deteriorated lead-acid batteries, when it was used together with a suitable amount of organic polymers, such as PVA. The other recent proposals on increasing the performance of lead-acid batteries are also introduced, e.g. a hybrid type lead-acid battery combined a lead-acid battery with a super capacitor.
Tetraethylammonium tetrafluoroborate (TEABF4), which is commonly used as the electrolyte for electric double-layer capacitors (EDLCs), has poor solubility in chain carbonates such as dimethyl, ethyl methyl, and diethyl carbonates (DMC, EMC, and DEC, respectively). Triethylmethoxymethylammonium bis(oxalato)borate (TEMMABOB) is a novel quaternary ammonium salt based on a halogen-free chelatoborate anion. TEMMABOB has good solubility in the chain carbonates as well as in propylene carbonate (PC). Electric conductivities of PC-chain carbonate binary solutions of TEMMABOB were slightly lower than that of a PC single solution of TEABF4. However, double-layer capacitances for three-electrode measurement cells using TEMMABOB were comparable to those obtained for TEABF4.
We investigated the electrochemical behavior of the triazinedithiol derivative (TAD), 6-anilino-1,3,5-triazine-2,4-dithiol monosodium (ATDS), on a Au(111) electrode surface in 0.05 M HClO4 using electrochemical measurements and scanning tunneling microscopy (STM). The oxidation of Au was significantly suppressed by modifying Au with ATDS. It was found that each ATDS molecule formed an agglomerate recognized as a set of three bright spots on the Au(111). The agglomerate was also in part linearly ordered along the √3 direction, and no definite phase transition was seen, which was supported by the fact that the CV curve was degenerated by ATDS molecules adsorbed on the electrode in the double-layer region. This result differed from previously reported results of the CV and ECSTM measurements for the 6-octylthio-1,3,5-triazine-2,4-dithiol monosodium (OTDS)-modified Au(111) electrode. The ATDS molecule formed significantly stable adlayer structures on the Au(111). This might contribute to the relatively high corrosion inhibition ability of the ATDS molecule.
A long-life medium-power three-volt lithium-ion battery consisting of Li[Ni1/2Mn3/2]O4 (P4332) and the zero-strain lithium insertion material of lithium titanium oxide (LTO; Li[Li1/3Ti5/3]O4) was described with emphasis on the processing method to prepare Li[Ni1/2Mn3/2]O4 for long-life applications. The preparation conditions were re-examined by thermogravimetric analysis, scanning electron microscopy, FT-IR, powder X-ray diffraction, and electrochemical methods. Well-defined crystals having the (111) facets of octahedra are essential for long-life application, which can be made by heating a reaction mixture at a temperature higher than 900°C in air for 12 h, and characteristic absorption bands of the superlattice structure in IR spectra were also needed for both a high rechargeable capacity more than 135 mAh g−1 with a flat operating voltage and long cycle life, which can be made by heating the well-defined crystals at 700°C in air for at least 12 h, i.e., two-step solid-state reaction. To demonstrate the long-life medium-power three-volt lithium-ion battery, the 2000-cycle test of the cell under a positive-electrode-limited capacity was performed at 3.33 mA cm−2 or 259 mA g−1 based on the Li[Ni1/2Mn3/2]O4 weight from 1.0 to 3.5 V at room temperature. Based on the results, no noticeable increase in polarization was observed even after 2000 cycles although the capacity faded ca. 15%. The unexpected capacity fading is described in terms of an imbalance in the coulombic efficiencies associated with the complex chemistry at positive and negative electrodes by the electrolyte.
A nanocomposite electrode of enzyme, mediator, and carbon nanotube was fabricated for the application to an enzyme electrode in biofuel cells. The nanocomposite for the anode consisted of polyion complex matrix where glucose oxidase, tetrathiafulvalene as a mediator, and carbon nanotube as an electron transport enhancer were immobilized on the glassy carbon electrode. From electrochemical measurements, the enzyme electrode possessed an ability of electro-oxidizing glucose by utilizing the enzyme activity of glucose oxidase via the redox of tetrathiafulvalene in a buffer solution (pH=7.0) at 37°C. This nanocomposite anode demonstrated a higher current density of 500 µA cm−2 in a glucose solution at 250 mV vs. Ag/AgCl for the application of glucose/oxygen biofuel cells.