If we categorize types of batteries as based on the nature of reversal of chemical reaction in it, it can be categorized into two basic categories:
- Primary cell, and
- Secondary cell.
In a primary cell, the chemical reaction eats away one of the electrodes, usually the negative electrode. When this happens, the electrode must be replaced or the cell must be discarded.
In a galvanic-type cell, the zinc electrode and the liquid electrolyte are usually replaced. However, It is usually cheaper to buy a new dry cell than to repair it. The simplest form of a primary cell is the Dry Cell, which consists of a cylindrical zinc container, which forms the negative electrode. The electrolyte is in the form of a paste of ammonium chloride. A carbon rod surrounded by a paste of manganese dioxide act as the positive electrode. The batteries that we use today are identical to the dry cell described above.
- Positive terminal (Metal cap)
- Negative terminal (Zinc container)
- Carbon rod
- Ammonium chloride paste
- Core of powered manganese dioxide and carbon
- Pitch seal
In a secondary cell, the electrodes and electrolyte are altered by the chemical action. This action takes place when the cell delivers current. A secondary cell may be restored to its original condition by forcing an electric current through it in the direction opposite to that of discharge.
The Inverter battery is a common example of a secondary cell. The Secondary cell has one major advantage over Primary cell. As in the primary cell, when the chemical reaction between the electrode and the electrolyte goes on, the chemicals used in the cell are slowly spent until the cell can is no longer able to produce a current. We then have to discard these cells as they are no longer chemically active. Whereas Secondary cells can be recharged and reused many times. Secondary cells are sometimes known as wet cells.
The various types of secondary cells in use are:
- Lead acid cell
- Nickel cadmium cell
- Nickel iron cell
- Silver zinc cell
- Lithium / Chlorine cell
- Lithium / Sulphur cell
- Lithium-Aluminium / iron sulphide cell
- Sodium/ Sulphur cell