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Abstract: Li-air battery using ionic liquids, N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) amide (DEME-TFSA) and N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)amide (PP13-TFSA), as the solvents for electrolyte have been studied. A significant improvement of discharge capacity has been observed for DEME-TFSA (4315 mAh g−1-electrode at current density of 0.1 mA cm−2), compared with PP13-TFSA. As a discharged product, aggregates reaching 4 μm diameter in size are formed on the surface of cathode, almost 80% of the products are decomposed after charge. By using Raman spectroscopy, two typical peaks attributed to Li2O2 were detected from the discharged aggregates. From the cross sectional SEM images, vacancy occupation ratios of discharged and charged electrodes are estimated, and they are in good agreement with the theoretical calculations. The discharged products formed inside of the cathode are not decomposed completely by charge. [Copyright &y& Elsevier]

The oxygen reduction reaction in an ionic liquid (IL) consisting of N , N -diethyl- N -methyl- N -(2-methoxyethyl)ammonium (DEME) cation and the bis(trifluoromethanesulfonyl)imide (TFSI) anion was investigated in the anhydrous and water saturated conditions respectively. The IL was demonstrated to be stable in the operating range of a lithium air cell in both the anhydrous and water saturated conditions. The addition of water was found to lower the overpotential for the oxygen reduction reaction by 40 mV. Finally, the reaction rate constant was found to increase by an order of magnitude with the addition of water hence demonstrating the tendency of water to promote/catalyze the oxygen electrochemistry in non-aqueous systems. [ABSTRACT FROM AUTHOR]

Abstract: Ionic liquids composed of N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium (DEME), N-methyl-N-methoxyethylpiperidinium (PP1.1o2) cations functionalized with ethers, N-methyl-N-propylpiperidinium (PP13), and N-butyl-N-methylpyrrolidinium (P14) cations and the bis(trifluoromethanesulfonyl)amide (TFSA) anion are investigated for application as electrolytes in non-aqueous lithium–oxygen (Li–O2) batteries. The PP13–TFSA, P14–TFSA and DEME–TFSA ionic liquids have high oxygen radical stability. A comparison of the lithium supply capacity measured using pulse-gradient spin-echo NMR for 7Li nuclei and the oxygen supply capacity measured using electrochemical methods indicates that the oxygen supply is the rate-limiting step for the generation of lithium–oxygen compounds (LiO x ) in these ionic liquids with supporting electrolytes. The DEME–TFSA system has the highest LiO x generation activity among the ionic liquid systems examined. We demonstrate the improved performance (output power, discharge–charge capacity and coulombic efficiency) of a Li–O2 battery using the DEME–TFSA system compared with that using the PP13–TFSA system. The improvements observed for the DEME–TFSA system are attributed to the high LiO x generation properties and lithium ion supply. [Copyright &y& Elsevier]

Mg(BH4)(NH2) (I) is prepared by ball milling of a 1:1 molar mixture of Mg(BH4)2 (II) and Mg(NH2)2 followed by annealing. [ABSTRACT FROM AUTHOR]