LiPo and LiIon batteries are very picky about charging and discharging rules. Also, for instance excessive overcharging not only destroys the battery, but it can lead to catastrophic failure (in other words, an explosion or fire). Similar risk is in case of large over-current (or outright short circuit) Therefore a good battery has a protection circuit limiting voltages and currents.
In addition to the protection circuit, the normal charging and discharging have to be controlled properly, or the battery's life time will be seriously shortened. An excellent explanation and instruction is on page
The charging control is easiest to implement with a specialized IC because the current and voltage control rules are non-trivial, and even a minor over-charge or over-discharge will damage the battery, or at least tend to shorten its life. There are also rules regarding temperature: Charging should not be done in too cold or too warm. As a rule-of thumb, don't charge below 0 Celsius, or over 45 Celsius. Discharging temperature limits are typically -20 to +60.