Ashok Nagarkatti
Energy is important to all of us, for a variety of reasons. For lighting, for cooking, for transportation, for manufacturing, for computation, for communication, and almost everything we do on a daily basis. Energy has different forms, the primary forms being heat, electricity, sound, and light.
Of these, electricity is the most convenient form of energy to store, control and use. Because it can be tapped quickly from an electrical line and used for various applications such as to run a motor or to heat water or even to power the computer or the cell phone. But electricity as generated cannot be stored in the form of electrical energy. The most convenient form of storing electrical energy is the “battery”.
A battery is the commonly used term for an electrochemical cell. In an electrochemical cell, electricity is converted to chemical energy when it is charged by converting the chemicals to a state of higher energy through an electrochemical reaction. When the cell is discharged, reactions occur in the reverse direction yielding energy instantaneously as electrochemical energy. Thus,
A battery is a device that converts the chemical energy contained in its active materials into electrical energy by means of an electrochemical oxidation – reduction (redox) reaction. A single cell or a number of such cells connected in series is called a battery.
How does an electrochemical cell work?
An electrochemical cell consists of a positive electrode called the cathode and a negative electrode called the anode. When a cell is discharged by connecting a load or a resistance across the positive and negative electrodes to provide electrical energy, an oxidation reaction occurs at the negative electrode and a reduction reaction takes place at the positive. In this type of oxidation-reduction (redox) reaction, ions flow from one electrode to the other through a medium called electrolyte and electrons flow from the negative electrode to the positive in the external circuit. This process in a battery cell is called an electrochemical reaction. The energy available from an electrochemical cell is always in the form of DC or Direct Current.
The author is a Chemical Engineer from IIT, Mumbai, and retired from the board of HBL Power Systems Ltd in 2010. He can be reached at ashokn@hbl.in.