Hi @neelam, welcome to the forum!
The dimmer example should work. If you want to use only the esp8266 with wifi (no nrf/rfm or other radio), you'll also need to add gateway settings from https://www.mysensors.org/build/esp8266_gateway
Hi all,
Should anyone face the same problem, I found the root cause: brownout threshold. I burned a new bootloader (Optiboot 8.0) without such trigger and the node has been working with used batteries (~2.7V) since May.
Hope this helps.