For lead‒acid batteries, the phenomena and structural changes leading to discharge capacity fading of the positive active-mass (PAM) during partial state-of-charge (PSoC) operation are but scarcely studied. PAM has a complex structure and charge‒discharge reactions proceed through many elementary processes and phenomena that involve several electrochemically active species and intermediates. The present study has evaluated these structural changes during PSoC operation of automotive lead‒acid batteries. In order to improve the cycling performance of the PAM, the effect of adding (i) an inorganic phosphorous-containing substance as to the sulfuric acid electrolyte solution and (ii) a clay mineral substance to the positive plate paste. The studied materials are natural inorganic substances that are environmentally friendly and widely available at low cost. PSoC cycling of flooded-type 2 V, 4 Ah test cells at 17.5% DoD provokes considerable changes in degree of crystallinity of the beta-PbO2 phase, the content of the alpha-PbO2 phase, the PAM pore volume and surface area, as well as the size and shape of individual PbO2 particles. The two additives are able to suppress and delay the processes that cause deterioration of the PAM discharge performance. The test cells with the studied additives sustained more than 2 000 cycles. This performance corresponds to a notable 2-fold improvement in cycle-life compared with the control cells. Moreover, it compares favourably with the 2022 Key Performance Indicator target for the PSoC endurance of automotive lead‒acid batteries set in the Roadmap of the Consortium for Battery Innovation.
Dr Plamen Nikolov –
Plamen Nikolov is the Head of the Electrochemical Power Sources Department at the Bulgarian Academy of Sciences. His recent scientific and technical activities are concentrated on the problems of positive plates in lead‒acid batteries. Nikolov is co-author of numerous technical papers published in international scientific journals and conference proceedings and has delivered several presentations at prestigious lead‒acid battery forums.