Electrochemical impedance spectroscopy: Understanding the role of the reference electrode

Bismuth based alloys with different lithium content have been synthesized by in situ electrochemical lithiation. The stability of potential of the alloys with time has been studied, showing stable potential during a period of at least 3 weeks. The alloy with higher lithium content is the less polarizable, with exchange current density over 20 times higher than Li. The LixBi alloys have been implemented as reference electrode (RE) for three-electrode electrochemical impedance spectroscopy (EIS) in lithium-ion batteries and compared to Li. These alloys are proposed here as alternative to Li due to their stability and potentials positive to the solid electrolyte interphase (SEI) formation. The reaction overpotential of the RE material has been found to be a key parameter to take into account when measuring EIS with three-electrode setup. (C) 2013 Elsevier B.V. All rights reserved.