It is required in a home automation project to restore the settings of all gadgets / devices to the same level as they were before power failure. How do I keep the program running in NodeMCU during 5 volt supply failure with a Lithium button cell of 3 volt? There are some commercial sets available with this feature.
I don’t think it is possible to power the ESP8266 properly using a button cell of 3V.
You need at least 3.3V for the ESP8266 to operate properly.