Development of reliable lithium microreference electrodes for long-term in situ studies of lithium-based battery systems

An in situ method to prepare lithium microreference electrodes has been developed. The microreference electrodes are made by electrochemical deposition of metallic lithium from both the positive and negative electrodes onto a copper wire positioned in-between the two Li-based battery electrodes. The stability of these microreference electrodes was found to be dependent on the deposition current density and the thickness of the metallic lithium layer. A current density of 0.2 mA/cm(2) and a lithium layer thickness of 4 mum were shown to be the most favorable deposition condition. When the potential of the electrodes eventually starts to degrade due to consumption'' of the deposit, the microreference electrodes can advantageously be recovered by lithium redeposition. The redeposited electrodes were verified to be as stable as the freshly prepared electrodes. The validity of the microreference electrode was confirmed by electrochemical impedance spectroscopy. The microreference electrodes were employed to monitor the electrode potentials during prolonged cycling. The as-obtained potential plots of both the positive and negative electrodes are present in this paper. (C) 2004 The Electrochemical Society.