Transformation of a new polyoxometalate into multi-metal active sites on ZIF-derived carbon nanotubes as bifunctional cathode catalyst and dendrite-free anode coating for Zn-air batteries

•A new POM with multi-metal active sites is designed as a calcination precursor.•The POM is calcined on ZIF-derived Co-NCNTs to form Zn/Mo2C@ Co-NCNTs.•Multi-metal active sites from POM enhance ORR/OER and inhibit dendrite growth.•The POM is verified to be superior to Zn/Mo mixed salt as the calcination precursor.•The coin cell with Zn/Mo2C@Co-NCNTs shows high power density and stability.