The electrochemical window and an availability of the (alpha + beta) Al-Li alloy electrode as a reference electrode were investigated at 523-673 K in a LiBr-KBr-CsBr eutectic melt. From differential scanning calorimetry and inductively coupled plasma atomic emission spectroscopy, it was confirmed that the cathodic limit of this melt is lithium metal deposition. The anodic limits of bromine gas evolution were 3.38 V (vs. Li+/Li) at 523 K and 3.22 V at 673 K, which determined the electrochemical window of this melt. The electrochemical formation of AlLi(beta) alloy phase was confirmed by X-ray diffraction analysis. The (alpha + beta) Al-Li alloy electrode was proved to have excellent characteristics as a reference electrode in terms of stability, reproducibility, and reversibility. The thermodynamic properties were estimated for the Al-Li alloy in the coexisting (alpha + beta) phase state at 523-673 K from the measured equilibrium potential. (C) 2004 The Electrochemical Society.