The problem of mobile over charging comes when the battery is left on after charging for several hours. In this case, excess lithium ions reach the anode from the cathode.
Scientist Dan Stengart at Princeton University says in an interview that mobile batteries can be understood by the example of a rubber band. Charging the battery is similar to pulling the rubber band and when the battery is in use it is like the rubber band coming back to its position. The way the rubber breaks when it is over-stretched, similarly overcharging can also cause the battery to explode due to the excess lithium ions collected on one side.
However, Dan also says that most mobile batteries also have the facility to protect them from over-charging, in which the battery automatically stops charging when full charged. But, in recent times, problems have also been found in this system. For this reason, many experts also advise never to charge the battery hundred percent.