A New In Situ and Operando Measurement Method to Determine the Electrical Conductivity of the Negative Active Material in Lead-Acid Batteries during Operation

The electrical conductivity of the negative active material in lead-acid batteries has been found to significantly influence the properties of the electrode. Though several publications have addressed this subject, essential information on the conductivity evolution during cycling as well as the influence of additives could yet not be elucidated, even though specific knowledge could support the enhancement of existing lead-acid battery technology. In this study, a novel measurement setup is presented which enables the in-situ and operando measurement of the electrical resistance of bulk electrodes during operation based on the implementation of a four-point probe setup into a laboratory electrode. A comprehensive evaluation of the measurement setup is conducted using the negative electrode of a lead-acid battery as a test material. The experimental results are supported by numerical simulations in order to reflect and include all relevant geometrical and electrical influences from the measurement setup. A direct correlation between active material resistance and conductivity can be established, including the influence of the vertical position of the four-point probes. Finally, the evolution of the discharge capacity, electrical resistance and electrical conductivity of the negative electrode is studied over ten C5 cycles and correlated to well-known structural developments within the active material.