Pressure-Stabilized High-Entropy (FeCoNiCuRu)S2 Sulfide Anode toward Simultaneously Fast and Durable Lithium/Sodium Ion Storage

Recent developments in advanced anode materials for sodium-ion capacitors: a mini-review

The abundant availability of sodium resources has significantly promoted the development of sodium-ion storage devices. Among them, sodium-ion capacitors (SICs), composed of battery-type anodes and capacitor-type cathodes, have garnered increasing attention due to their ability to combine the advantages of both sodium-ion batteries and supercapacitors, offering high power density, high energy density, and long cycling stability. However, a major challenge for SICs lies in the mismatch between the slow electrochemical reaction kinetics of battery-type anodes and the fast kinetics of capacitor-type cathodes, which hinders their practical application. This review systematically discusses advanced battery-type anode materials with potential applications, primarily focusing on carbon materials, metal sulfides, and metal-organic frameworks. These materials exhibit notable advantages, including high reversible capacity, excellent rate performance, and good cycling stability. Furthermore, the sodium storage mechanisms of these materials, along with various modification strategies to enhance their performance also are delved into. Finally, the existing challenges in carbon materials, metal sulfides, and metal-organic frameworks are summarized, and potential future directions for their development are proposed.

High mixing entropy of MnFeCoNiCu-S to drive high performance sodium storage

Transition metal sulfides (TMSs) are often used as anode materials in sodium-ion batteries (SIBs). Nevertheless, the inevitable volume effect and low intrinsic conductivity cause rapid capacity fading of the TMS anode materials. In our work, a high-entropy metal sulfide (HEMS) MnFeCoNiCu-S anode material was obtained by vulcanization and pyrolysis of quinary MOF precursors. Mixing of multiple cations contributes to the diversity of material chemistry and structure. Strong synergies between Mn, Fe, Co, Ni, and Cu establish a steady electronic structure, and high configurational entropy gives the material excellent mechanical strength and excellent stability. Furthermore, the derived carbon matrix can also improve the conductivity and cycling stability of the HEMS. At a current density of 5 A g-1, the HEMS anode can still provide 326.4 mA h g-1 capacity after 7000 cycles, showing long-term sodium storage durability. The synergies of multiple metals and the transfer of multiple electrons ensure excellent sodium storage, which makes the HEMS a favorable candidate for SIB anode materials.

High-entropy sulfoselenide as negative electrodes with fast kinetics and high stability for sodium-ion batteries

Conversion electrodes offer higher reversible capacity and lower cost than conventional intercalation chemistry electrodes, but suffer from kinetic limitation and large volume expansion. Despite significant efforts, developing conversion electrodes with fast charging capability and extended lifespan remains challenging. Here, by leveraging the advantages of high-entropy doping and morphology tailoring, we develop a high-entropy hierarchical micro/nanostructured sulfoselenide Cu0.88Sn0.02Sb0.02Bi0.02Mn0.02S0.9Se0.1 electrode with entropy-driven fast-charging capability. When used as a negative electrode material for sodium-ion batteries, it achieves a stable cycle life of 10,000 cycles at 30 A g-1 and a high reversible capacity of 365.7 mAh g-1 under fast charging in 13 seconds at 100 A g-1. Moreover, high-entropy sulfoselenide also demonstrates stable cycling and good rate capability as a positive electrode material for lithium metal batteries, achieving a fast-charging capability of 37 seconds that is comparable with state-of-the-art layered cathodes. High-entropy sulfoselenide is characterized by its robust crystal structure, low ion diffusion barrier, and effective suppression of side reactions with electrolytes during cycling. Importantly, transmission X-ray microscopy affirms the chemical stability of HESSe, which underpins its fast-charging performance.

High-Entropy Metal Sulfide Nanocrystal Libraries for Highly Reversible Sodium Storage

Controlled synthesis of high-entropy materials offers a unique platform to explore unprecedented electrochemical properties. High-entropy metal sulfides (HEMSs) have recently emerged as promising electrodes in electrochemical energy storage applications. However, synthesizing HEMSs with a tunable number of components and composition is still challenging. Here, a HEMS library is built by using a general synthetic approach, enabling the synthesis of HEMS with arbitrary combinations of 5 to 12 out of 28 elements in the periodic table. The formation of a solid solution of HEMS is attributed to the two-step method that lowers the energy barrier and facilitates the sulfur diffusion during the synthesis. The hard soft acid base (HSAB) theory is used to precisely describe the conversion rates of the metal precursors during the synthesis. The HEMSs as cathodes in Na-ion batteries (SIBs) is investigated, where 7-component HEMS (7-HEMS) delivers a promising rate capability and an exceptional sodium storage performance with reversible a capacity of 230 mAh g-1 over 3000 cycles. This work paves the way for the multidisciplinary exploration of HEMSs and their potential in electrochemical energy storage.

High-Entropy Metal-Organic Frameworks and Their Derivatives: Advances in Design, Synthesis, and Applications for Catalysis and Energy Storage

As a nascent class of high-entropy materials (HEMs), high-entropy metal-organic frameworks (HE-MOFs) have garnered significant attention in the fields of catalysis and renewable energy technology owing to their intriguing features, including abundant active sites, stable framework structure, and adjustable chemical properties. This review offers a comprehensive summary of the latest developments in HE-MOFs, focusing on functional design, synthesis strategies, and practical applications. This work begins by presenting the design principles for the synthesis strategies of HE-MOFs, along with a detailed description of commonly employed methods based on existing reports. Subsequently, an elaborate discussion of recent advancements achieved by HE-MOFs in diverse catalytic systems and energy storage technologies is provided. Benefiting from the application of the high-entropy strategy, HE-MOFs, and their derivatives demonstrate exceptional catalytic activity and impressive electrochemical energy storage performance. Finally, this review identifies the prevailing challenges in current HE-MOFs research and proposes corresponding solutions to provide valuable guidance for the future design of advanced HE-MOFs with desired properties.

High-Entropy Electrode Materials: Synthesis, Properties and Outlook

High-entropy materials represent a new category of high-performance materials, first proposed in 2004 and extensively investigated by researchers over the past two decades. The definition of high-entropy materials has continuously evolved. In the last ten years, the discovery of an increasing number of high-entropy materials has led to significant advancements in their utilization in energy storage, electrocatalysis, and related domains, accompanied by a rise in techniques for fabricating high-entropy electrode materials. Recently, the research emphasis has shifted from solely improving the performance of high-entropy materials toward exploring their reaction mechanisms and adopting cleaner preparation approaches. However, the current definition of high-entropy materials remains relatively vague, and the preparation method of high-entropy materials is based on the preparation method of single metal/low- or medium-entropy materials. It should be noted that not all methods applicable to single metal/low- or medium-entropy materials can be directly applied to high-entropy materials. In this review, the definition and development of high-entropy materials are briefly reviewed. Subsequently, the classification of high-entropy electrode materials is presented, followed by a discussion of their applications in energy storage and catalysis from the perspective of synthesis methods. Finally, an evaluation of the advantages and disadvantages of various synthesis methods in the production process of different high-entropy materials is provided, along with a proposal for potential future development directions for high-entropy materials.

High-Pressure-Field Induced Synthesis of Ultrafine-Sized High-Entropy Compounds with Excellent Sodium-Ion Storage

Emerging high entropy compounds (HECs) have attracted huge attention in electrochemical energy-related applications. The features of ultrafine size and carbon incorporation show great potential to boost the ion-storage kinetics of HECs. However, they are rarely reported because high-temperature calcination tends to result in larger crystallites, phase separation, and carbon reduction. Herein, using the NaCl self-assembly template method, by introducing a high-pressure field in the calcination process, the atom diffusion and phase separation are inhibited for the general formation of HECs, and the HEC aggregation is inhibited for obtaining ultrafine size. The general preparation of ultrafine-sized (<10 nm) HECs (nitrides, oxides, sulfides, and phosphates) anchored on porous carbon composites is realized. They are demonstrated by combining advanced characterization technologies with theoretical computations. Ultrafine-sized high entropy sulfides-MnFeCoCuSnMo/porous carbon (HES-MnFeCoCuSnMo/PC) as representative anodes exhibit excellent sodium-ion storage kinetics and capacities (a high rating capacity of 278 mAh g-1 at 10 A g-1 for full cell and a high cycling capacity of 281 mAh g-1 at 20 A g-1 after 6000 cycles for half cell) due to the combining advantages of high entropy effect, ultrafine size, and PC incorporation. Our work provides a new opportunity for designing and fabricating ultrafine-sized HECs.

Recent advances and understanding of high-entropy materials for lithium-ion batteries

Lithium-ion batteries (LIBs) has extensively utilized in electric vehicles and portable electronics due to their high energy density and prolonged lifespan. However, the current commercial LIBs are plagued by relatively low energy density. High-entropy materials with multiple components have emerged as an efficient strategic approach for developing novel materials that effectively improve the overall performance of LIBs. This article provides a comprehensive review the recent advancements in rational design of innovative high-entropy materials for LIBs, as well as the exceptional lithium ion storage mechanism for high-entropy electrodes and considerable ionic conductivity for high-entropy electrolytes. This review also analyses the prominent effects of individual components on the high-entropy materials' exceptional capacity, considerable structural stability, rapid lithium ion diffusion, and excellent ionic conductivity. Furthermore, this review presents the synthesis methods and their influence on the morphology and properties of high-entropy materials. Ultimately, the remaining challenges and future research directions are outlined, aimed at developing more effective high-entropy materials and improving the overall electrochemical performance of LIBs.

Growth of Highly Oriented (VNbMoTaW)S2 Layers

Compositional tunability, an indispensable parameter for modifying the properties of materials, can open up new applications for van der Waals (vdW) layered materials such as transition-metal dichalcogenides (TMDCs). To date, multielement alloy TMDC layers are obtained via exfoliation from bulk polycrystalline powders. Here, we demonstrate direct deposition of high-entropy alloy disulfide, (VNbMoTaW)S2, layers with controllable thicknesses on free-standing graphene membranes and on bare and hBN-covered Al2O3(0001) substrates via ultra-high-vacuum reactive dc magnetron sputtering of the VNbMoTaW target in Kr and H2S gas mixtures. Using a combination of density functional theory calculations, Raman spectroscopy, X-ray diffraction, scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, we determine that the as-deposited layers are single-phase, 2H-structured, and 0001-oriented (V0.10Nb0.16Mo0.19Ta0.28W0.27)S2.44. Our synthesis route is general and applicable for heteroepitaxial growth of a wide variety of TMDC alloys and potentially other multielement alloy vdW compounds with the desired compositions.