The electrolysis of saturated salt water is the conversion of electrical energy into chemical energy.
The process of electrolysis of saturated salt water requires electricity, and electrical energy is converted into the internal energy of chemical substances through chemical reactions.
After electrolysis of saturated salt water, the chloride (NaCl) and water (H2O) contained in the salt water are ionized, generating hydrogen (H2) and chlorine (Cl2) at the cathode and anode respectively, and the remaining hydrogen and oxygen root ions combine with the sodium ions to form sodium hydroxide (NaOH). In industry, sodium hydroxide is usually produced by electrolysis of salt water. Contact between chlorine ions or chlorine gas and sodium hydroxide solution will produce sodium chloride and sodium hypochlorite. (NaClO).
In fact, it is not possible to produce electricity.
What you added only increased the electrolyte, which means the internal resistance of the battery is reduced and the conductivity is increased. This old battery seems to have power again when used, as you feel that little light. The light bulb lights up or the little toy can move again.
The principle of the battery is actually a redox reaction. Electrons are transferred through the graphite rod in the middle (general dry cell), so there is electricity. Salt water and urea do not undergo redox reactions and therefore cannot produce electricity on their own.
For larger batteries, like car batteries, you sometimes go to a service shop to add water or something like that. Actually, it's not water, but sulfuric acid or something.