In recent years, the concept of entropy stabilization of crystal structures in oxide systems has led to an increased research activity in the field of “high entropy oxides”. These compounds comprise the incorporation of multiple metal cations into single-phase crystal structures and interactions among the various metal cations leading to interesting novel and unexpected properties. Here, we report on the reversible lithium storage properties of the high entropy oxides, the underlying mechanisms governing these properties, and the influence of entropy stabilization on the electrochemical behavior. It is found that the stabilization effect of entropy brings significant benefits for the storage capacity retention of high entropy oxides and greatly improves the cycling stability. Additionally, it is observed that the electrochemical behavior of the high entropy oxides depends on each of the metal cations present, thus providing the opportunity to tailor the electrochemical properties by simply changing the elemental composition.

High‐entropy materials, especially high‐entropy alloys and oxides, have gained significant interest over the years due to their unique structural characteristics and correlated possibilities for tailoring of functional properties. The developments in the area of high‐entropy oxides are highlighted here, with emphasis placed on their fundamental understanding, including entropy‐dominated phase‐stabilization effects and prospective applications, e.g., in the field of electrochemical energy storage. Critical comments on the different classes of high‐entropy oxides are made and the underlying principles for the observed properties are summarized. The diversity of materials design, provided by the entropy‐mediated phase‐stabilization concept, allows engineering of new oxide candidates for practical applications, warranting further studies in this emerging field of materials science.

An overview of high-entropy materials for energy applications, including H₂ catalysis and storage, CO₂ conversion, O₂ catalysis and electrochemical energy storage, is given and the challenges and opportunities within this field are discussed.

In the present work, a new class of high entropy materials for energy storage applications is introduced. Multi-anionic and -cationic compounds are prepared by facile mechanochemistry using a recently designed multi-cationic transition-metal-based high entropy oxide as the precursor and LiF or NaCl as the reactant, leading to formation of lithiated or sodiated materials. Notably, the Li-containing entropy-stabilized oxyfluoride described herein (Li_x(Co_0.2Cu_0.2Mg_0.2Ni_0.2Zn_0.2)OF_x) exhibits a working potential of 3.4 V vs. Li⁺/Li, enabling its use as a cathode active material. Unlike conventional (non-entropy-stabilized) oxyfluorides, this new material shows enhanced Li storage properties due to entropy stabilization, which, in general, facilitates tailoring the cycling performance by varying the constituent elements in yet unprecedented ways. In addition, we demonstrate that the concept of entropy stabilization is also applicable to Na-containing oxychlorides with a rock-salt structure, thus paving the way toward development of (next-generation) post-Li battery technologies.