Novel high-entropy oxides for energy storage and conversion: From fundamentals to practical applications

High-entropy oxides (HEOs) are gaining prominence in the field of electrochemistry due to their distinctive structural characteristics, which give rise to their advanced stable and modifiable functional properties. This review presents fundamental preparations, incidental characterizations, and typical structures of HEOs. The prospective applications of HEOs in various electrochemical aspects of electrocatalysis and energy conversion-storage are also summarized, including recent developments and the general trend of HEO structure design in the catalysis containing oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), supercapacitors (SC), lithium-ion batteries (LIBs), solid oxide fuel cells (SOFCs), and so forth. Moreover, this review notes some apparent challenges and multiple opportunities for the use of HEOs in the wide field of energy to further guide the development of practical applications. The influence of entropy is significant, and high-entropy oxides are expected to drive the improvement of energy science and technology in the near future.