High-entropy materials (HEMs), a new type of materials, have attracted significant attention in the field of electrocatalytic reactions, batteries and energy-storage materials over the past few years owing to their unique structure, controllable elementary composition, and adjustable properties. These excellent characteristics result from four major factors: high entropy, sluggish-diffusion, severe lattice distortion, and cocktail effect, and are used widely in energy-energy applications. This review aims to summarize the recent progress of HEMs in electrochemical energy-storage. We begin with the concept, structure, and four core effects of HEMs that provide the basic information on HEMs. Next, we discuss the major properties of HEMs and analyze the relationship between their structures and properties. Furthermore, we highlight the outstanding performance of HEMs in hydrogen storage, electrode materials of batteries, catalysis, and supercapacitors, and briefly explain the mechanisms of these materials that are crucial in energy storage and conversion. This review will assist in understanding the excellent energy-storage properties, intricacies of the phase structures, elemental interactions, and reaction mechanisms associated with HEMs. Moreover, challenges and future development prospects are summarized. This work will provide insight into the factors that are crucial for designing HEMs with energy storage properties.