Should not connect any non-lipo batteries to the battery terminals.
In short: the XIAO BLE has a lipo-charger circuit. When it detects a lipo connected and the lipo level is at least (about) 50-150mV below the charging voltage (4.2V) it will start charging with around 4.2V.
Turning pin 22 to OUTPUT and LOW in the code will increase charging from about 30-50mA to 80-100mA. Make sure you battery is rated at that. Most run of the mill lipo batteries are chargeable at 1C only. But safer at 0.5C. The C is the factory ampere rating of the battery. So a 200mA lipo can be safely charged at 200mA.