Batteries

Technology Description

Batteries are electrochemical devices that convert chemical energy into electrical energy during battery discharge and, during battery charge, convert the electrical energy back into chemical energy for long-term storage. The fundamental building block of a battery is a single electrochemical cell. Cells are connected together in variety of configurations to provide the necessary voltage, energy, and power for the application.

The chemical reactions that occur in an electrochemical cell and that are responsible for storing the electrical energy are called electrochemical reactions. These reactions involve the release or uptake of an electron or electrons by one chemical species to form another. Every cell has two separate chemical reactions occurring—one involving the release of the electron(s) during battery discharge (at the negative electrode material, or anode) and one involving the take-up of the electron(s) during battery discharge (at the positive electrode material, or cathode). When the cell is charged the electrochemical reactions occur in the reverse directions, taking electrons out of the material at the positive electrode and putting them back into the negative electrode material. The names of the different types of batteries generally refer to the chemical specie(s) responsible for energy storage in that cell type.

The other critical element in a cell is the electrolyte (salt solution), which is essential for charge to flow because it allows balancing of the negatively charged electron that is moving from one electrode to the other. In most cells the electrolyte solutions and active materials (positive and negative electrode materials) are completely sealed inside a single container and isolated from the outside. In flow batteries the materials (electrolyte, positive and negative electrode materials) are housed in a separate container and are actively pumped into the container where the electrochemical reactions occur.

Updated April 2010