I think OP is saying that if you applied (e.g.) 4.2V to a lithium battery that it would always look like the battery was sitting at that same 4.2V as you were charging it. The answer is that the charger either limits the amount of current flowing into the battery (when this is occurring the voltage to the battery will not be seen as a full 4.2V) or limits the voltage being fed to the battery (and measures the amount of current flow into the battery).
All chargers limit the rate of charge using one of the above methods. If this is not done then the battery is at risk of overheating and becoming damaged.