The T-Zigbee unit contains a AP5054B Lipo charing chip that is powered from the USB port.

This can be used to charge a 3.7V Lipo battery connected to the device using a USB cable connected to the USB-C port. The battery is connected via the power cable included in the box:

From the battery there are two linear regulators supplying power to the ESP32 and the Zigbee radio module.

The chip powering the Zigbee module has its enable pin connected to the ESP32, so the ESP32 can power the Zigbee module on/off.

The maximum input voltage for the regulators is 5.5V, so take care not to attach batteries of a higher voltage.