A liquid organic electrolyte system for lithium ion batteries with graphite anode containing acetate group compounds as electrolyte additives has been studied. The decomposition of electrolyte on the graphite electrode could be remarkably suppressed by the addition of the amounts of additives (phenyl acetate, iso-propenyl acetate, l-acetoxy methoxy ethane and acetic anhydride). Molecular orbital calculations have been used as a screening tool for the selection of the additives. The correlation between the lowest unoccupied molecular orbital (LUMO) energy and the reduction potential of the additives is roughly linear.
Potentiometric gas sensors using a Ni reference electrode closed in a Na+ conducting Na2O-Al2O3-4SiO2 glass were investigated for detection of CO2 and Cl2 sensing. An electric potential for the reference electrode was fixed by utilization of the Ni reference electrode. For the CO2 sensor using the Na2CO3 auxiliary phase and Ni reference electrode, the EMF responded to changes in the CO2 gas concentration between 10 ppm and 10000 ppm. The EMF of the CO2 sensor using the Ni reference electrode also responded to a decrease in the O2 gas concentration. However, the EMF was not fixed when the Pt reference electrode was utilized instead of Ni. The O2 gas concentration for the reference electrode would be equilibrated by the Ni, NiO, and oxygen diffused from the solid electrolyte. For the Cl2 gas sensor using the NaCl auxiliary phase, the EMF responded even to low Cl2 gas concentrations below 10 ppm and also a ppb- level gas under humid conditions.
Electrochemical reduction of substituted (alkylamino) phosphonium salts was carried out to confirm the generations of iminophosphoranes and phosphorus ylide, and compared with the results of the base method. The Wittig and AzaWittig reaction under the presence of benzaldehyde confirmed the generations of iminophosphoranes and phosphorus ylides. We found that it is possible to synthesize selectively both the iminophosphoranes and the phosphorus ylides from a single (alkylamino) phosphonium salt by the electrochemical reduction or by the base method under mild conditions. As a method of dehydrogenation reaction, the electrochemical reduction can play a similar role as strong bases such as sodium amide, sodium methoxide, sodium phenoxide, and DBU.
The electrodeposition of CdS was conducted in aqueous solution containing CdSO4 and Na2S2O3 as sources supplying cadmium and sulfur, respectively. The roles of several additives, comprising (NH4)2SO4, NaCl and glycerol were investigated by cyclic voltammetry. The proposed mechanism of the electrodeposition of CdS consists of an adsorption process coupled with a chemical reaction: Cd2++S2−→CdS and/or an adsorption process coupled with an electron transfer reaction: Cd2++S+2e−→CdS. The presence of all such additives enables the adsorption processes and the electron transfer reaction to take place at the potentials positive of −0.8V, thereby promoting the formation of CdS; in addition, the undesired electrodeposition of Cd was suppressed.
A 5-cyano cyclic indole trimer(5-cyanoCIT) and a 5-carboxy cyclic indole trimer(5-carboxyCIT) have been investigated for their electrochemistry and redox capacitor properties. These material electrodes showed electrochemical redox system at higher formal potential of 1.08 V vs. Ag/AgCl compared to a non-substituted cyclic indole trimer (CIT, 0.94 V vs. Ag/ AgCl). Specific capacities obtained for the 5-cyanoCIT and 5-carboxyCIT electrodes were 88 Ah kg－1 (264 F g－1) and 86 Ah kg－1(258 F g－1), respectively. After potential cycling (100,000 cycles), the 5-cyanoCIT electrode maintained 80% (70 Ah kg－1) of initial capacity, while the 5-carboxyCIT electrode showed only 43% (37 Ah kg－1) with formation of electro-inactive structure. Cyclability could be improved up to 64% (52 Ah kg－1) by adding conducting nano-carbon (Ketjen black, KB) to form 5-carboxyCIT/KB nanocomposite.
We investigated the relationship between 'the thermodynamic stability and Li content in the crystal structure of the orthorhombic LiMn1－xMxO2(M = Mn, Al, Cu). The enthalpy change for mol of atoms for the reaction, ΔHR, were calculated from the heat of dissolution. ΔHR increased with the decreasing Li content except for the two-phase region and significantly increased the two-phase region for each sample. For the same Li content, the LixMnO2 sample obtained by reflux heating was more thermodynamically stable than the other samples. Furthermore, the LixMn0.95Al0.05O2 sample was unstable, and the LixMn0.95Cu0.05O2 sample was more stable than that of LixMnO2, which was obtained by the same method. The crystal structure of LixMn1－yMyO2(M=Mn, Al) was analyzed by the neutron powder diffraction method. The Madelung energy and bond lengths of each sample were calculated using the Rietveld analysis. The Madelung energy of the spinel phase was low, and the spinel phase was more stable than the orthorhombic phase. The distributions of the nuclear density and electron density were calculated by MEM in order to determine the bonding state. The nuclear density decreased with the decreasing Li content. In o-LiMn0.95M0.05O2 (M=Al, Cu), the Li localization and strong covalence of (Mn, M)-O were estimated from the distribution of the electron densities.
Manganese dioxides were prepared from the solutions of permanganate. salts and manganese sulfate at 80℃ for 1 h. The formation of γ-MnO2 phase was confirmed by X-ray diffraction. The particle size and specific surface area of the product were 0.3-0.4μm and 218-226 m2 g－1, respectively. After heating at 375℃ for 5h in air, the formation of β-MnO2 phase was observed. When the product was used as the cathode material of lithium/manganese oxide cell, the discharge capacity at 0.88 mA cm－2 was 239-256 mAh g－1, which were higher than that of the cell using electrolytic manganese dioxide (188 mAh g－1). It was found that the manganese dioxide prepared using this process is hopeful as a cathode material for lithium/manganese dioxide battery.