Laboratory development of active material for lead-acid batteries. part i: kinetic study of the discharge of negative active material of lead-acid batteries produced from paste containing tribasic lead sulphate

This work presents a kinetic study of the discharge process of a laboratory-made negative plate for lead-acid batteries using cyclic voltammetry. Negative plates were prepared from a precursor paste based on tribasic lead sulfate (3BS), followed by curing and electrochemical formation. Voltammetric measurements were performed at scan rates ranging from 5 to 100 µV s⁻1 in 4.6 mol L⁻1 H₂SO₄, in triplicate. Results were interpreted through the Ohmic model for the growth of a continuous, ultrathin PbSO₄ film on the porous negative active material (NAM). The analysis, performed with specific quantities (per gram of NAM), revealed a stationary-state film growth and allowed to determine the average specific ionic resistance of the film (Rf = 1.88 ± 0.18 Ω g⁻1), the average Flade potential (EF = − 0.9429 ± 0.0040 V), the average transfer coefficient (αm/f = 1.03 ± 0.05), and the average exchange specific current (Ip,a0 = 65.06 ± 9.17 mA g⁻1). The porous nature of the 3BS-based plate and its consequences for local acid concentration and reaction-zone propagation are explicitly discussed. The average voltammetric specific charges reached stationary values of qp,a = 69.0 C g⁻1 and qa = 109 C g⁻1, corresponding to utilization coefficients of approximately 7.4% and 11.7%, respectively, relative to the theoretical specific charge of the Pb → PbSO₄ conversion. The average exchange current density, recalculated per unit BET area, falls in the range of 6.50–13.01 µA cm⁻2, consistent with the reaction-zone mechanism operating on a fraction of the total porous surface. The results validate the transposition of the Ohmic solid-state model from flat Pb electrodes to real porous negative plates.