Amorphous vanadium oxide/carbon composite (V2O5/C) was first applied to the positive electrode active material for rechargeable aluminum batteries. Electrochemical properties of V2O5/C were investigated by cyclic voltammetry and charge-discharge tests. Reversible reduction/oxidation peaks were observed for the V2O5/C electrode and the rechargeable aluminum cell showed the maximum discharge capacity over 200 mAh g(-1) in the first discharging. The XPS analyses after discharging and the following charging exhibited that the redox of vanadium ion in the V2O5/C active material occurred during discharging and charging, and the average valence of V changed between 4.14 and 4.85.

Aluminum bis(trifluoromethanesulfonyl)imide (Al(TFSI) 3 ) was synthesized by a simple substitution reaction and investigated as the Al 3+ source for the electrolyte of a rechargeable Al battery. The electrochemical window was extended to 3.6 V with the electrolyte containing Al(TFSI) 3 in AN, whereas it was ∼2.5 V with the conventional electrolyte for the Al rechargeable battery. A reversible electrochemical Al deposition/dissolution reaction was observed on a Mo plate electrode with small overpotential less than 0.5 V. NMR and Raman spectra identified the main Al species in the electrolyte as Al(TFSI − ) x (AN) 6-x 3-x (x = 1 ∼ 6).

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Charge transfer kinetics at the Li metal electrode/electrolyte interface for three inorganic solid electrolytes and an organic liquid electrolyte were elucidated with two parameters, exchange current density (i 0 ) for Li/Li + couple reactions and ionic conductivity in electrolyte. The former was evaluated by potential step method with a microelectrode, while the latter was done by electrochemical impedance spectroscopy. Both i 0 and ionic conductivity showed Arrhenius type dependence, and activation energies (E a ) for the charge transfer reactions and ionic conduction were evaluated. In the case of the organic liquid electrolyte, E a for the Li/Li + couple reactions was higher than that for ionic conduction because of the solvation/desolvation of Li + ion. However, for the Li 2 S-P 2 S 5 solid solid electrolytes, the E a for the Li/Li + couple reactions was quite close to that for ionic conduction due to the lack of the solvation/desolvation.