Prior studies showed that lithium-doped high-entropy oxides (Li-HEO) are promising electrode materials for Li-ion batteries. Usually, Li-batteries work at atmospheric pressure and in a mild temperature range of ~20 ‒ 60 °C. However, in some cases such as for explorations of outer space and the deep sea, the batteries may encounter extreme conditions such as low temperature, high temperature and/or high pressure. Thus, it is necessary to study the influences of temperature and pressure on the electronic and ionic conductance of Li_x-HEO for developing new generations of Li-batteries that can function in extreme conditions. In this work, we synthesized four Li_x-HEO compounds (x = 0, 0.065, 0.117 and 0.200), and studied their electrical conductivities in a wide range of temperatures (79 ‒ 773 K) and/or under high pressures (up to ~50 GPa). Experimental results show that the electronic and ionic conductivities of the Li_x-HEO compounds are significantly enhanced with the increase of the lithium doping content, and that temperature has a great effect on the electronic conductivities of the four Li_x-HEO compounds (their electrical resistivities are reduced by 7, 6, 5, and 3 orders of magnitude from ~ 300 to 773 K for the four Li contents). By comparison, pressure has a minor effect on the electronic conductivities of Li-doped HEO (with a change of only about 1 order of magnitude from 0 to ~ 50 GPa), yet it has a large effect on the ionic conductance (which is greatly suppressed at a pressure of ~10 GPa). These findings provide us a basic understanding of the electrical conduction of Li-HEO at extreme conditions, which would be indispensable to their applications in new technical areas.
 

High-entropy oxide, Li-doping, p-type semiconductor, electrical conductivity, electrical conduction mechanism, mixed electronic and ionic conduction, high pressure, extreme condition