The electrochemically stable and relatively high conductive room temperature molten salts (RTMS) have been obtained with the use of small ammonium cations such as methoxymethyltrimethylammonium and bis(trifluoromethylsulfonyl)imide. The RTMS showed high conductivity (4.7 mS cm−1 at 25 °C) which is the highest value of all the ammonium based RTMS reported so far.

The electrical conductivities of the molten binary salt mixtures Li 2 CO 3 -X 2 CO 3 ͑X: Na, K, Rb, and Cs͒ and Na 2 CO 3 -Z 2 CO 3 ͑Z: K, Rb, and Cs͒ were measured using an ac two-probe technique and electrochemical impedance spectroscopy. The electrical conductivities of the eutectic compositions of ͑Li 0.52 Na 0.48 ͒ 2 CO 3 and ͑Li 0.62 K 0.38 ͒ 2 CO 3 at 923 K were 2.06 and 1.31 S cm −1 , respectively. The conductivity of molten Li 2 CO 3 -X 2 CO 3 ͑X: Na, K, Rb, and Cs͒ and Na 2 CO 3 -Z 2 CO 3 ͑Z: K, Rb, and Cs͒ decreases with an increase in the ionic radius of X or Z. We have succeeded in correlating the equivalent conductivity of a binary carbonate mixture ⌳, with the composition ͑x A and x B ͒, the equivalent conductivities of the pure components A and B ͑⌳ A and ⌳ B ͒, and two parameters ͑ A and B ͒ asThe pair of interaction parameters ͑ A and B ͒ can be estimated for a binary system of molten carbonates using the relationship between the cationic radii and the equivalent conductivities of the pure carbonates.

The density, surface tension, and electrical conductivity of the ternary molten salt mixtures of Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 system have been measured. The molar volumes of the ternary mixtures agreed well with those estimated by additivity arguments within 0.7%. It was found that the surface tension of a ternary carbonate mixture can be predicted from known surface tension of binary carbonates, and the mixing of two molten carbonate mixtures of the same surface tension makes a mixture of almost equal surface tension before mixing in this ternary system. We have succeeded in predicting the equivalent conductivity of the ternary carbonate mixtures using the cationic radii and the equivalent conductivities of the pure carbonates.The physical properties of ionic liquids such as molten salts and room-temperature molten salts are essential items of knowledge not only for the industrial use of these compounds, but also for a fundamental understanding of their nature. As a kind of ionic liquid, molten carbonates attract widespread research activity because they are likely to be used as catalysts, 1-3 as material processing solvents, 4-6 and as the electrolytes of molten carbonate fuel cells ͑MCFCs͒. 7 The latter is an excellent type of power conversion technology with a high efficiency and a low impact on the environment. Some frequently used compositions of MCFC electrolyte materials are Li 2 CO 3 -Na 2 CO 3 and Li 2 CO 3 -K 2 CO 3 . The physical properties such as density, surface tension, and conductivity of these binary molten carbonates have been thoroughly investigated. 8-15 Density ͑molar volume͒ is necessary to know the optimum loading of electrolyte for MCFCs. Surface tension is needed to estimate electrolyte distribution in MCFCs. 16 Conductivity directly affects the output of the MCFC. These physical properties are not only essential for practical use but also provide us an insight into the melt structure, the forces operating among ions, and the ionic movement in molten carbonate.The ternary molten salt mixtures of the Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 system show a large variation of physical properties, over a wide temperature range from 671 to about 1300 K, and therefore offer a wide choice of compositions and properties. Mohamedi et al. investigated oxygen solubility and Warburg impedance in this system for MCFC. 17 Kim et al. reported a phase diagram for Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 and vapor pressures of chemical species through thermodynamic calculations. 18 But, the data on density, surface tension, and conductivity of this system are quite restricted. 14,15 In addition, there are few reports of relationships between the physical properties and composition for ternary molten salt compositions.In this work, we present data on the density, the molar volume, the surface tension, and the electrical conductivity of molten Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 . In addition, methods to predict the physical properties of this system are reported. ExperimentalReagent grade chemicals, Li 2 CO 3 ͑99%͒, Na 2 CO 3 ͑9...

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Iron-containing lithium-rich layered manganese oxides are promising as cathode active materials for fabricating high energy density and low-cost lithium-ion batteries. We synthesized Li 1.26 Mn 0.52 Fe 0.22 O 2 (or 0.7Li 2 MnO 3 • 0.3LiFeO 2 ) by using the co-precipitatehydrothermal-calcination method. We then tested a graphite/Li 1.26 Mn 0.52 Fe 0.22 O 2 cell after a stepwise pre-cycling treatment. The pre-cycling treatment drastically increased the specific capacity of the Li 1.26 Mn 0.52 Fe 0.22 O 2 from 167 to 236 mAh g −1 at a current rate of 5 mA g −1 . Other cell performances, such as operation voltage, discharge rate capability, and cyclability, also improved with this treatment. An analytical study using gas chromatography revealed that these improvements were derived from the suppression of oxygen release from the oxide lattice. X-ray absorption spectroscopy and X-ray photoelectron spectroscopy analyzes indicated that the main charge compensation mechanism of pre-cycling treatment was not the redox reaction of transition metals, such as Mn 3+ /Mn 4+ and Fe 3+ /Fe 4+ , but the redox reaction of O 2− accompanying O 2 2− formation in the oxide lattice.

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