Can add a power module for P3541 A02?

For example battery?

Please refer to below RTC info in Nano module datasheet in DLC.

The following backup cells may be attached to the PMIC_BBAT pin:
 Super Capacitor (gold cap, double layer electrolytic)
 Standard capacitors (tantalum)
 Rechargeable Lithium Manganese cells
The backup cells MUST provide a voltage in the range 2.5V to 3.5V. These is charged with a constant current (CC), constant
voltage (CV) charger that can be configured between 2.5V and 3.5V CV output and 50μA to 800μA CC.