Lithium Ion Battery Charger and Power Path Management IC
The main parameter is the charge rate, or 1C, to determine the maximum current delivered while the battery is being charged. It is important to meet this specification to ensure the battery is not damaged, and to prevent overheating or catastrophic failure. It is equally important to not exceed the maximum charge voltage of 4.2V, nor to discharge below 2.8 to 3.0V. Your design should include protection for the battery to prevent this condition.

Here's a good tutorial about Li-ion batteries. https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries