Kinetically Accelerated Lithium Storage in High-Entropy (LiMgCoNiCuZn)O Enabled By Oxygen Vacancies

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.

Intergrating Hollow Multishelled Structure and High Entropy Engineering toward Enhanced Mechano-Electrochemical Properties in Lithium Battery

Hollow multishelled structures (HoMSs) are attracting great interest in lithium-ion batteries as the conversion anodes, owing to their superior buffering effect and mechanical stability. Given the synthetic challenges, especially elemental diffusion barrier in the multimetal combinations, this complex structure design has been realized in low- and medium-entropy compounds so far. It means that poor reaction reversibility and low intrinsic conductivity remain largely unresolved. Here, a hollow multishelled (LiFeZnNiCoMn)3O4 high entropy oxide (HEO) is developed through integrating molecule and microstructure engineering. As expected, the HoMS design exhibits significant targeting functionality, yielding satisfactory structure and cycling stability. Meanwhile, the abundant oxygen defects and optimized electronic structure of HEO accelerate the lithiation kinetics, while the retention of the parent lattice matrix enables reversible lithium storage, which is validated by rigorous in situ tests and theoretical simulations. Benefiting from these combined properties, such hollow multishelled HEO anode can deliver a specific capacity of 967 mAh g-1 (89% capacity retention) after 500 cycles at 0.5 A g-1. The synergistic lattice and volume stability showcased in this work holds great promise in guiding the material innovations for the next-generation energy storage devices.

High-Entropy Oxides for Rechargeable Batteries

High-entropy oxides (HEOs) have garnered significant attention within the realm of rechargeable batteries owing to their distinctive advantages, which encompass diverse structural attributes, customizable compositions, entropy-driven stabilization effects, and remarkable superionic conductivity. Despite the brilliance of HEOs in energy conversion and storage applications, there is still lacking a comprehensive review for both entry-level and experienced researchers, which succinctly encapsulates the present status and the challenges inherent to HEOs, spanning structural features, intrinsic properties, prevalent synthetic methodologies, and diversified applications in rechargeable batteries. Within this review, the endeavor is to distill the structural characteristics, ionic conductivity, and entropy stabilization effects, explore the practical applications of HEOs in the realm of rechargeable batteries (lithium-ion, sodium-ion, and lithium-sulfur batteries), including anode and cathode materials, electrolytes, and electrocatalysts. The review seeks to furnish an overview of the evolving landscape of HEOs-based cell component materials, shedding light on the progress made and the hurdles encountered, as well as serving as the guidance for HEOs compositions design and optimization strategy to enhance the reversible structural stability, electrical properties, and electrochemical performance of rechargeable batteries in the realm of energy storage and conversion.

Porous High-Entropy Oxide Anode Materials for Li-Ion Batteries: Preparation, Characterization, and Applications

High-entropy oxides (HEOs), as a new type of single-phase solid solution with a multi-component design, have shown great potential when they are used as anodes in lithium-ion batteries due to four kinds of effects (thermodynamic high-entropy effect, the structural lattice distortion effect, the kinetic slow diffusion effect, and the electrochemical "cocktail effect"), leading to excellent cycling stability. Although the number of articles on the study of HEO materials has increased significantly, the latest research progress in porous HEO materials in the lithium-ion battery field has not been systematically summarized. This review outlines the progress made in recent years in the design, synthesis, and characterization of porous HEOs and focuses on phase transitions during the cycling process, the role of individual elements, and the lithium storage mechanisms disclosed through some advanced characterization techniques. Finally, the future outlook of HEOs in the energy storage field is presented, providing some guidance for researchers to further improve the design of porous HEOs.

Engineering Oxygen Vacancies in (FeCrCoMnZn)3O4-δ High Entropy Spinel Oxides Through Altering Fabrication Atmosphere for High-Performance Rechargeable Zinc-Air Batteries

High entropy oxides (HEOs) offer great potential as catalysts for oxygen electrocatalytic reactions in alkaline environments. Herein, a novel synthesis approach to prepare (FeCrCoMnZn)3O4-δ high entropy spinel oxide in a vacuum atmosphere, with the primary objective of introducing oxygen vacancies into the crystal structure, is presented. As compared to the air-synthesized counterpart, the (FeCrCoMnZn)3O4-δ with abundant oxygen vacancies demonstrates a low (better) bifunctional (BI) index of 0.89 V in alkaline media, indicating enhanced electrocatalytic oxygen catalytic activity. Importantly, (FeCrCoMnZn)3O4-δ demonstrates outstanding long-term electrochemical and structural stability. When utilized as electrocatalysts in the air cathode of Zn-air batteries, the vacuum atmosphere synthesized (FeCrCoMnZn)3O4-δ catalysts outperform the samples treated in an air atmosphere, displaying superior peak power density, specific capacity, and cycling stability. These findings provide compelling evidence that manipulating the synthesis atmosphere of multi-component oxides can serve as a novel approach to tailor their electrochemical performance.

Cycling Reconstructed Hierarchical Nanoporous High-Entropy Oxides with Continuously Increasing Capacity for Li Storage

High-entropy oxides (HEOs) have been showing great promise in a wide range of applications. There remains a lack of clarity regarding the influence of nanostructure and composition on their Li storage performance. Herein, a dealloying technique to synthesize hierarchical nanoporous HEOs with tunable compositions is employed. Building upon the extensively studied quinary AlFeNiCrMnOx , an additional element (Co, V, Ti, or Cu) is introduced to create senary HEOs, allowing for investigation of the impact of the added component on Li storage performance. With higher specific surface areas and oxygen vacancy concentrations, all their HEOs exhibit high Li storage performances. Remarkably, the senary HEO with the addition of V (AlNiFeCrMnVOx ) achieves an impressive capacity of 730.2 mAh g-1 at 2.0 A g-1 , which surpasses all reported performance of HEOs. This result demonstrates the synergistic interaction of the six elements in one HEO nanostructure. Additionally, the battery cycling-induced reconstruction and cation diffusion in the HEOs is uncovered, which results in an initial capacity decrease followed by a subsequent continuous capacity increase and enhanced Li ion diffusion. The results highlight the crucial roles played by both nanoporous structure design and composition optimization in enhancing Li storage of HEOs.

The elemental pegging effect in locally ordered nanocrystallites of high-entropy oxide enables superior lithium storage

High-entropy oxides (HEOs) can be well suited for lithium-ion battery anodes because of their multi-principal synergistic effect and good stability. The appropriate selection and combination of elements play a crucial role in designing conversion-type anode materials with outstanding electrochemical performance. In this study, we have successfully built a single-phase spinel-structured HEO material of (Mn0.23Fe0.23Co0.22Cr0.19Zn0.13)3O4 (HEO-MFCCZ). When the HEO-MFCCZ materials transform into a coexisting state of amorphous and nanocrystalline structures during the cycling process, the inert Zn element can initiate a pegging effect, causing enhanced stability. The transition also introduces many defect sites, effectively reducing the potential barrier for ion transport and accelerating ion transport. The increased electronic and ionic conductivities and pseudocapacitive contribution significantly enhance the rate performance. As a result, a unique and practical approach is provided for developing anode materials for lithium-ion batteries.

High-entropy oxides: an emerging anode material for lithium-ion batteries

High entropy oxides (HEOs) have gained significant attention in multiple research fields, particularly in reversible energy storage. HEOs with rock-salt and spinel structures have shown excellent reversible capacity and longer cycle spans compared to traditional conversion-type anodes. However, research on HEOs and their electrochemical performance remains at an early stage. In this highlight, we review recent progress on HEO materials in the field of lithium-ion batteries (LIBs). Firstly, we introduce the synthesis methods of HEOs and some factors that affect the morphology and electrochemical properties of the synthesized materials. We then elaborate on the structural evolution of HEOs with rock-salt and spinel structures in lithium energy storage and summarize the relationship between morphology, pseudocapacitance effect, oxygen vacancy, and electrochemical performance. In the end, we give the challenges of HEO anodes for LIBs and present our opinions on how to guide the further development of HEOs for advanced anodes.

Understanding the Configurational Entropy Evolution in Metal-Phosphorus Solid Solution for Highly Reversible Li-Ion Batteries

The high-entropy materials (HEM) have attracted increasing attention in catalysis and energy storage due to their large configurational entropy and multiunique properties. However, it is failed in alloying-type anode due to their Li-inactive transition-metal compositions. Herein, inspired by high-entropy concept, the Li-active elements instead of transition-metal ones are introduced for metal-phosphorus synthesis. Interestingly, a new Zn_x Ge_y Cu_z Si_w P₂ solid solution is successfully synthesized as proof of concept, which is first verified to cubic system in F-43m. More specially, such Zn_x Ge_y Cu_z Si_w P₂ possesses wide-range tunable region from 9911 to 4466, in which the Zn_0.5 Ge_0.5 Cu_0.5 Si_0.5 P₂ accounts for the highest configurational entropy. When served as anode, Zn_x Ge_y Cu_z Si_w P₂ delivers large capacity (>1500 mAh g^-1 ) and suitable plateau (≈0.5 V) for energy storage, breaking the conventional view that HEM is helpless for alloying anode due to its transition-metal compositions. Among them, the Zn_0.5 Ge_0.5 Cu_0.5 Si_0.5 P₂ exhibits the highest initial coulombic efficiency (ICE) (93%), Li-diffusivity (1.11 × 10^-10 ), lowest volume-expansion (34.5%), and best rate performances (551 mAh g^-1 at 6400 mA g^-1 ) owing to its largest configurational entropy. Possible mechanism reveals the high entropy stabilization enables good accommodation of volume change and fast electronic transportation, thus supporting superior cyclability and rate performances. This large configurational entropy strategy in metal-phosphorus solid solution may open new avenues to develop other high-entropy materials for advanced energy storage.