Why do electrons leave a battery from the negative terminal?

Electrons leave a battery from the negative terminal due to the difference in electric potential between the terminals. The negative terminal has an excess of electrons, creating a higher concentration of negative charge. When a circuit is completed, this excess of electrons is driven towards the positive terminal, where there is a deficiency of electrons, facilitating the flow of electric current. This movement occurs because electrons are repelled by the negative terminal and attracted to the positive terminal.