Here is some data on charging a 220 mAh battery at a current of 100 mA using the nRF52840. During charging, the battery voltage reaches 4.2 V, but if the battery is worn out, the voltage drops to about 3.7 V immediately after it is removed from the nRF52840. Please compare the voltages during and after charging.
’ Charging characteristics of XIAO_nRF52840 and XIAO_ESP32C3 ’