In general battery is a device in which chemical energy is directly converted to electrical energy. A battery is an electrochemical cell that can be charged electrically to provide a static potential for power or released electrical charge when needed. A battery generally consists of anode, cathode and electrolyte.
Battery is very important part in mobile to function and is said to be the heart of the mobile because without battery mobile does not function. It is a small rectangular shaped piece placed at the back of the mobile. Battery consists of four types:
Sealed Lead Acid battery: Can hold a charge for up to 3 years and is inexpensive
Nickel-Cadmium battery: It fastly discharges energy, inexpensive and is widely available.
Nickel-Metal Hydride battery: it is used in https://www.learn-basics.com/computers and cell phones. No memory effect, unused capacity remains useable.
Lithium Ion battery: it is same as Nickel-Metal Hydride battery and is twice the charge capacity of Nickel-Cadmium battery.