A lead accumulator consists of an electrochemical cell in which the substances that act as active materials are:
• Lead dioxide (PbO2) on the positive electrode
• Spongy lead (Pb) to the negative electrode
• Electrolyte consisting of a solution of sulfuric acid (H2SO4) in water
During the construction of the cell both plates are covered with a layer of Lead, with different additives for the two plates, in the form of a very fine pulverized mixture. These appear as two rigid metal structures. When they are then immersed in the solution, they “soften”.
The electrolyte is made up of water which is used only to dilute the sulfuric acid. An acid is defined as any substance that contains one or more hydrogen atoms which can be replaced by metal atoms. If the acid contains oxygen it is called oxyacid and if it contains more than two hydrogen atoms it is polyvalent acid. H2SO4 sulfuric acid is a polyvalent oxyacid which replaces hydrogen with lead during the chemical reaction.
When a lead accumulator is to be formed, two lead plates are immersed in the solution which, having been exposed to the air, are covered with lead oxide, PbO. One plate is connected to the positive pole and the other plate to the negative pole of an electrical generator. Thus begins the phase of first charge: the positive plate is covered with lead dioxide and acquires a brown red color, while the negative plate is reduced to gray metallic lead.
The overall cell reaction is a redox or redox reaction. A reaction is called a reduction reaction when oxygen is removed from a substance, due to the effect of reducing substances that bind to oxygen. If, on the other hand, oxygen is released, we speak of oxidation, and the substances that release oxygen are called oxidants. Redox reactions in which ions are present (ionic reactions) are characterized by the passage of electrons from the reducing agent to the oxidant. The dissolution of a substance with an ionic structure (electrolyte) in a solvent such as water, whose molecules are dipoles, decreases the electrostatic forces of attraction that unite the ions. Anions and cations are obtained in the solution whose concentration is limited according to a chemical equilibrium between the dissociated molecules and the ions; the presence of these ions is crucial for electrolysis.
NB: The density measurement must be conducted after a rest period of the battery after the restoration of the electrolyte uniformity and at reference ambient temperatures. www.tcechargers.com