Batteries and Battery Processes

The storage of electricity in small or large packages depends upon the existence of chemical reactions that occur when electrons are transferred from one chemical species to another. In batteries, electrons are stored in electron-rich substances (donors), and when the batteries are discharged, the electrons flow from the donor, through the external circuit where they give up much of their energy, and return to the battery to be stored as low-energy electrons in chemical substances that are electron acceptors. This process is sketched schematically in Fig. 1.1. Since a net negative charge cannot accumulate on the acceptor without stopping the further flow of electrons, the charge must be neutralized by an influx of positively charged species (ions) generated at the electron donor. This flow of ions completes the electrical circuit, and current continues to flow until there are no more electrons available from the donor or until the acceptor becomes saturated with electrons. The chemical process itself consists of the creation of charged chemical species at the electron donor and their incorporation into the structure of the electron acceptor.