2026 Roadmap on compositionally complex and high entropy materials for energy applications

Hydrogen energy has drawn considerable attention in recent years, among which the efficient production of hydrogen energy from water electrolysis has become a hot research topic in this field. The oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in water electrolysis are the core of the catalytic efficiency. High entropy materials have excellent combinatorial properties due to their "cocktail effect", high entropy effect, slow diffusion effect, and lattice distortion effect. They have outstanding catalytic effect in the process of water electrolysis, and thus become a hot research topic in recent years. This review combines the two hot topics by introducing the up-to-date research progress of high entropy materials in catalyzing water electrolysis. First, evaluation indexes of electrocatalytic performance are explained. Second, this review demonstrates specific materials from the classification of high entropy alloys, high entropy oxides and nitrided high entropy materials, which includes the structure of the materials and their specific catalytic performance. Finally, it summarizes the research progress of high entropy materials in water electrolysis catalysis as well as gives an outlook on the future design direction of the materials.

Machine-learning and high-throughput studies for high-entropy materials

High entropy materials for catalysis: A critical review of fundamental concepts and applications

Multicomponent phase space is enormous and contains a vast number of complex new materials. Despite intensive investigation in the last decade and a half however, we are only slowly making progress towards understanding these new materials. This paper attempts to summarise some of the fundamental discoveries we have made about the geography of multicomponent phase space and the wide range of complex new materials that we have found within it. This paper discusses briefly the following topics: the size and shape of multicomponent phase space and the range of single- and multiple-phase fields that it contains; the (initially) surprising presence of many large near-ideal single-phase solid-solution phases, stabilised by a high configurational entropy of mixing; the extensive and wide-ranging variation of local nanostructure and associated mechanical and electronic lattice strain that permeates throughout high-entropy solid-solution phases; and some of the unusual, exciting and valuable properties that are then produced within multicomponent and high-entropy materials. Many of the results discussed have been obtained from the fcc Cantor alloys (based on the original Cantor alloy, equiatomic fcc CrMnFeCoNi) and the bcc Senkov alloys (based on the original Senkov alloy, equiatomic VNbMoTaW), two groups of multicomponent high-entropy single-phase materials that have been particularly widely studied. Similar behaviour is also found in other multicomponent high-entropy single-phase materials, though these have not been studied so intensively. In comparison with multicomponent high-entropy single-phase materials, rather little is known about multicomponent multiphase materials that have also not been studied so intensively.

Machine learning and computational methods can accelerate materials discovery by accurately predicting material properties at low cost. Nevertheless, input data to algorithms and structure model parameters remains a key obstacle. The limitations of conventional battery materials could be overcome by high-entropy materials, a unique class of special valuable materials. The knowledge of designing the crystal structure of high-entropy materials is advancing the design and fabrication of new materials for batteries and supercapacitors, even before chemical synthesis, through the use of learning algorithms and quantum computing. In this review, we first focus on quantum computing and the structure of high-entropy materials, especially high-entropy MXenes. We then discuss how to encode and decode the crystal structure of materials, which is a key factor in creating a database for high-entropy materials. We also discuss how to utilize deep learning algorithms for material discovery prior to synthesis, as well as how to employ these algorithms to identify high-entropy materials suitable for batteries and supercapacitors. Finally, we discuss the potential of new quantum computing and artificial intelligence approaches for determining the structure of high-entropy materials in the energy fields.

High entropy energy storage materials: Synthesis and application

High-entropy materials (HEMs), including alloys, ceramics and other entropy-stabilized compounds, have attracted considerable attention in different application fields. This is due to their intrinsically unique concept and properties, such as innovative chemical composition, structural characteristics, and correspondingly improved functional properties. By establishing an environment with different chemical compositions, HEMs as novel materials possessing superior attributes present unparalleled prospects when compared with their conventional counterparts. Notably, great attention has been paid to investigating HEMs such as thermoelectrics (TE), especially for application in energy-related fields. In this review, we started with the basic definitions of TE fundamentals, the existing thermoelectric materials (TEMs), and the strategies adopted for their improvement. Moreover, we introduced HEMs, summarized the core effects of high-entropy (HE), and emphasized how HE will open up new avenues for designing high-entropy thermoelectric materials (HETEMs) with promising performance and high reliability. Through selecting and analyzing recent scientific publications, this review outlines recent scientific breakthroughs and the associated challenges in the field of HEMs for TE applications. Finally, we classified the different types of HETEMs based on their structure and properties and discussed recent advances in the literature.

A critical mission need exists to develop new materials that can withstand extreme environments and multiple sequential threats. High entropy materials, those containing 5 or more metals, exhibit many exciting properties which would potentially be useful in such situations. However, a particularly hard challenge in developing new high entropy materials is determining a priori which compositions will form the desired single phase material. The project outlined here combined several modeling and experimental techniques to explore several structure-property-relationships of high entropy ceramics in an effort to better understand the connection between their compositional components, their observed properties, and stability. We have developed novel machine learning algorithms which rapidly predict stable high entropy ceramic compositions, identified the stability interplay between configurational entropy and cation defects, and tested the mechanical stability of high entropy oxides using the unique capabilities at the Dynamic Compression Sector facility and the Saturn accelerator.

High-entropy materials: Excellent energy-storage and conversion materials in the field of electrochemistry

Alloys, the greatest gift of humans, have affected the material world to the greatest extent. The alloy world has evolved from very simple binary solid solution to complex one, consisting of 5 or more components. The beginning of the current century saw a paradigm shift in the alloy design principal leading to discovery high entropy materials (HEMs). Brian Cantor and Jien-Wei Yeh have independently reported the discovery of quinary equiatomic CoCrFeMnNi FCC alloy to start the research activity in HEMs. These are believed to be stabilized by higher entropy of mixing. The properties of HEMs are also significantly affected by enthalpy of mixing, atomic size differences of the components, and valence electron concentration, permitting only suitable alloying elements to increase the strength, ductility, and other physical properties of these alloys. Interestingly, the HEMs can be bought under the broad category of complex concentrated alloys which do not necessarily lead to formation of complex phase and microstructure. Recently, the discovery of entropy-stabilized ceramics has expanded the scope of this novel concept, leading to development of novel multicomponent ceramics.KeywordsMulticomponent alloysHigh entropy alloys (HEMs)High entropy materials (HEMs)Core effects

High entropy materials are a relatively young new class of materials discovered in 2003. It possesses four kinds of special core effects as a result of its strong mixing nature such as (i) High entropy effect, (ii) Severe lattice distortion effect, (iii) Sluggish diffusion effect, and (iv) Cocktail effect. High Entropy Ceramics (HECs) are defined as the solid solutions of inorganic compounds (five or more cations sublattices) with one or more Wykoff sites shared by equal or nearly equal atomic ratios of multi-principal elements. HECs have gained the attention of researchers due to their fascinating properties. In this report, an A-site disordered high entropy perovskite (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3 ceramic was prepared via a solid-state reaction route. The XRD pattern and FESEM-EDS confirmed the formation of a single-phase solid solution with a tetragonal structure. A detailed study of the dielectric behavior of the sample was done. Modified Curie-Weiss law was fitted to the relative permittivity to analyze the relaxor behavior of the sample. HECs are highly tolerant to ions and their properties can be tailored by composition and according to the application purposes.

An ultrastable heterostructured oxide catalyst based on high-entropy materials: A new strategy toward catalyst stabilization via synergistic interfacial interaction

Sodium‐ion batteries (SIBs) have emerged as a cost‐effective alternative to lithium‐ion batteries due to the natural abundance and wide geographic distribution of sodium resources, which mitigate concerns over the scarcity and price volatility of lithium. However, the larger ionic radius of Na + (1.02 Å) compared to Li + (0.76 Å) produces inferior diffusion kinetics and structural stability. Therefore, layered transitional metal oxide cathode materials have extensively utilized high entropy doping to suppress undesirable phase transitions, improve kinetic performance, and enhance cationic and oxygen redox reversibility. Although the compositional tunability of high entropy doping offers considerable potential, it also introduces significant structural and chemical complexity. This necessitates the precise selection and optimization of dopant elements to target specific limitations observed in conventional low entropy systems. Accordingly, this review comprehensively evaluates the impact of dopant strategies and configurational entropy on the performance of compositionally proximate high entropy materials. It offers a systematic guide for rationally tailoring high entropy techniques to overcome interconnected performance‐limiting obstacles across diverse undoped systems. The review clarifies the definitional controversy surrounding the term “high entropy” and elucidates the theoretical limitations that hinder the accurate prediction of high entropy materials before concluding with an outline of prospective research directions.

Doping effects of alkaline earth element on oxygen reduction property of high-entropy perovskite cathode for solid oxide fuel cells

High-entropy materials, which consist of multiple elements occupying a single sublattice in a disordered manner, have emerged as innovative material systems with various promising applications. Many macroscopic physical properties, such as electrical transport and thermal transport, are closely related to the periodic distribution of atoms. In high-entropy compounds, the long-range periodic arrangement of atoms is broken down by the disordered distribution of various elements, which would lead to changes in physical properties. Therefore, the high-entropy idea will open new avenues for designing these functional materials with promising performance and high reliability. This perspective focuses on the high-entropy strategies of thermoelectric materials, discussing how high entropy will alter their properties. The possible routes of designing high-entropy high-performance thermoelectric materials are prospected, which can also provide enlightenment for the development of high-entropy systems in other research fields.