Influence of basic carbon additives on the electrochemical performance of lead-carbon batteries

Abstract

Enhancement of the dynamic charge acceptance (DCA) of advanced lead-acid batteries for micro- and mild-hybrid cars is essential to improve the fuel consumption and CO2 emissions by recuperation of the braking energy. In this work, the effect of carbon surface basicity on the electrochemical activity and the DCA of lead-carbon electrodes is revealed. Five different activated carbons (AC) with different pH values ranging from 9.5 to 11.1 were prepared by ammonia and hydrogen gas treatments. These ACs were used as additives in the negative electrodes of 2 V lead-acid cells. The cyclic voltammetry of the pure carbon as well as lead-carbon (negative) electrodes demonstrates that the hydrogen evolution reaction (HER) activity is increased via higher surface basicity of the ACs. A correlation between the surface basicity of carbon and the DCA can be established in the electrochemical performance. A remarkable impact of carbon pH on the charge currents after the charge history (Ic) as well as final DCA (IDCA) is observed. In case of the charge currents after the discharge history (Id) and during simulated Stop/Start microcycles (Ir), the carbon content in the negative electrodes affects the charge currents. This work demonstrates that the DCA of advanced lead-carbon batteries can be improved by using carbon additives with higher pH in the negative electrodes.