1 Answer
Secondary cells can be recharged because they use a reversible chemical reaction to generate and store electrical energy. When a secondary cell discharges (when it's powering a device), a chemical reaction occurs that produces electrical energy. When it is recharged, the chemical reaction is reversed by applying an external electrical current, which forces the chemicals back into their original state, restoring the battery’s ability to store energy.
For example, in a lead-acid battery (like those used in cars), during discharge, the lead dioxide (PbO₂) at the positive plate and the sponge lead (Pb) at the negative plate react with sulfuric acid to form lead sulfate (PbSO₄) and water. When recharging, the electrical current causes the lead sulfate to break down and return the lead dioxide and sponge lead back to their original forms.
The key to recharging is that the reactions inside these cells can be reversed, unlike primary cells (like regular disposable batteries), where the reactions are not reversible, meaning once they discharge, they can't be used again.
For example, in a lead-acid battery (like those used in cars), during discharge, the lead dioxide (PbO₂) at the positive plate and the sponge lead (Pb) at the negative plate react with sulfuric acid to form lead sulfate (PbSO₄) and water. When recharging, the electrical current causes the lead sulfate to break down and return the lead dioxide and sponge lead back to their original forms.
The key to recharging is that the reactions inside these cells can be reversed, unlike primary cells (like regular disposable batteries), where the reactions are not reversible, meaning once they discharge, they can't be used again.