You want to build an IC? Surely that's not right.
If you want the specs on a particular IC, you can probably just google it.
Googling "lithium ion charger IC" will get you links to many different ICs, MAX1555, ISL6291, LM3621, MCP738xx, ...
Charging Lithium cells is relatively easy, as long as you follow the rules. The issues are to ensure that you neither over charge nor over discharge them -- the consequences vary, but can be between serious and explosive. Where you have a battery, the main issue is to ensure that no single cell is over discharged or over charged. As such, it is almost universal for each cell to be independently monitored.