Li-Ion Battery Protection Circuit: Do I tie BAT-- to Ground?
This is a common way to integrate a battery protection IC. The protection IC controls the two mosfets in Q1. If the battery is overdischarged, it turns off the right mosfet, preventing current from flowing from ground to the negative battery terminal (i.e. prevents the battery from discharging). If the battery is overcharged, it turns off the left mosfet, preventing current from flowing from the negative battery terminal to ground (i.e. prevents the battery from charging). In each of these cases, it allows current flow the other way (OD mode allows charging, OC mode allows discharging).
This IC also has other functions, like detecting overcurrent and short circuit, so it can also disconnect the battery if it sees those. It's also common to integrate a temperature sensor (although this IC doesn't allow it) to monitor the battery too.
Edit: to answer the actual question - No, do not tie the battery directly to ground, since that would make the protection IC useless and give you an unprotected li-ion battery, which is always bad.