Effects of aluminum content on thermoelectric performance of AlxCoCrFeNi high-entropy alloys

•Lattice thermal conductivities can be effectively reduced due to large mass mismatch.•Phonon-phonon scattering is not as dominant as scattering by random configurations.•Electron contribution to the ktotal is dominant over phonon at high temperatures.•Higher peak of the density of states is found in the BCC HEAs near the Fermi level.•Thermoelectric efficiency is found larger in the BCC than FCC structures.