Reliable reference electrodes for lithium-ion batteries

• Metallic lithium is polarizable and shows a stochastic behavior at high current rates.
• The potential of metallic lithium is dependent on the surface treatment.
• Li4Ti5O12 and LiFePO4 electrodes have reliable, reproducible, and stable potential.

Despite the high attention drawn to the lithium-ion batteries by the scientific and industrial community, most of the electrochemical characterization is carried out using poor reference electrodes or even no reference electrode. In this case, the performances of the active material are inaccurate, especially at high current densities. In this work we show the error committed in neglecting the polarizability of lithium counter electrodes, and we propose two reference electrodes to use in organic electrolytes based on lithium salts, namely Li4Ti5O12 and LiFePO4. In particular, it was observed that, the polarizability of the metallic lithium counter electrode has a relevant stochastic component, which renders measurements at high current densities (above 1 mA·cm− 2) in two electrode cells non reproducible.