What are the type of battery used in the cellphones worldwide for eg I have Lithium ion battery in mine?

Lithium ion is used almost exclusively for phone batteries and similar portable equipment because it has a high energy density, i.e. it can store a lot of energy in a small size and weight. At present no other battery technology comes close to the same density. However, lithium ion batteries also decay over a period of time, accelerated by high temperatures. It is possible for a lithium ion battery to be only 50% effective by the time it reaches a year old, hence the reduced battery life we all experience as our phones get older.