Energy Storage Mechanism,Challenge and Design Strategies of Metal Sulfides for Rechargeable Sodium/Potassium-Ion Batteries

Rechargeable sodium/potassium-ion batteries (SIBs/PIBs) with abundant reserves of Na/K and low cost have been a promising substitution to commercial lithium-ion batteries. As for pivotal anode materials, metal sulfides (MSx) exhibit an inspiring potential due to the multitudinous redox storage mechanisms for SIBs/PIBs applications. Nevertheless, they still confront several bottlenecks, such as the low electrical conductivity, poor ionic diffusivity, sluggish interfacial/surface reaction kinetics, and severe volume expansion, which distinctly restrain the battery performance. Meanwhile, the systematic insights into the design strategies of MSx for SIBs/PIBs have been seldom elaborated. In this review, the energy storage mechanism, challenge, and design strategies of MSx for SIBs/PIBs are expounded to address the above predicaments. In particular, design strategies of MSx are highlighted from the aspects of morphology modifications involving 1D/2D/3D configurations, atomic-level engineering containing heteroatom doping, vacancy creation, and interlayer spacing expansion, and MSx composites with other MSx, metal oxides, carbonaceous, and graphite materials to boost the comprehensive electrochemical performance of SIBs/PIBs. Furthermore, prospects are presented for the further advance of MSx to surmount imminent challenges, hoping to forecast feasible future orientations in this field.     

Recent Advances in Mn-Rich Layered Materials for Sodium-Ion Batteries

Branded with low cost and a high degree of safety, with an ambitious aim of substituting lithium-ion batteries in many fields, sodium-ion batteries have received fervid attention in recent years after being dormant for decades. Layered materials are a major focus of study owing to the extensive experience already gained in lithium-ion batteries, and the pursuit of a Mn-rich composition is critical to reduce the cost while retaining the performance. This review provides a timely update of the recent progress of Mn-rich layered materials for sodium-ion batteries based on the understandings of the phase forming principles, structure transformation upon cycling and charge compensation mechanisms and discusses potential ambiguities in the pursuit of high-performance materials.     

Electrocatalysis of Fe-N-C Bonds Driving Reliable Interphase and Fast Kinetics for Phosphorus Anode in Sodium-Ion Batteries

Phosphorus exhibits high capacity and low redox potential, making it a promising anode material for future sodium-ion batteries. However, its practical applications are confined by poor durability and sluggish kinetics. Herein, an innovative in-situ electrochemically self-driven strategy is presented to embed phosphorus nanocrystal (≈10 nm) into a Fe-N-C-rich 3D carbon framework (P/Fe-N-C). This strategy enables rapid and high-capacity sodium ion storage. Through a combination of experimental assistance and theoretical calculations, a novel synergistic catalytic mechanism of Fe-N-C is reasonably proposed. In detail, the electrochemical formation of Fe-N-C catalytic sites facilitates the release of fluorine in ester-based electrolyte, inducing Na⁺-conducting-enhanced solid-electrolyte interphase. Furthermore, it also effectively induces the dissociation energy of the P-P bond and promotes the reaction kinetics of P anode. As a result, the unconventional P/Fe-N-C anode demonstrates outstanding rate-capability (267 mAh g⁻¹ at 100 A g⁻¹) and cycling stability (72%, 10 000 cycles). Notably, the assembled pouch cell achieves high-energy density of 220 Wh kg⁻¹.     

General Synthesis of Dual Carbon‐Confined Metal Sulfides Quantum Dots Toward High‐Performance Anodes for Sodium‐Ion Batteries

Sponge‐like composites assembled by cobalt sulfides quantum dots (Co₉S₈ QD), mesoporous hollow carbon polyhedral (HCP) matrix, and a reduced graphene oxide (rGO) wrapping sheets are synthesized by a simultaneous thermal reduction, carbonization, and sulfidation of zeolitic imidazolate frameworks@GO precursors. Specifically, Co₉S₈ QD with size less than 4 nm are homogenously embedded within HCP matrix, which is encapsulated in macroporous rGO, thereby leading to the double carbon‐confined hierarchical composites with strong coupling effect. Experimental data combined with density functional theory calculations reveal that the presence of coupled rGO not only prevents the aggregation and excessive growth of particles, but also expands the lattice parameters of Co₉S₈ crystals, enhancing the reactivity for sodium storage. Benefiting from the hierarchical porosity, conductive network, structural integrity, and a synergistic effect of the components, the sponge‐like composites used as binder‐free anodes manifest outstanding sodium‐storage performance in terms of excellent stable capacity (628 mAh g^?1 after 500 cycles at 300 mA g^?1) and exceptional rate capability (529, 448, and 330 mAh g^?1 at 1600, 3200, and 6400 mA g^?1). More importantly, the synthetic method is very versatile and can be easily extended to fabricate other transition‐metal‐sulfides‐based sponge‐like composites with excellent electrochemical performances.     

Metal Catalyst to Construct Carbon Nanotubes Networks on Metal Oxide Microparticles towards Designing High-Performance Electrode for High-Voltage Lithium-Ion Batteries

Designing carbon nanotubes (CNTs)-based materials are attracting great attention due to their fantastic properties and greater performance. Herein, a new CNTs network triggered by metal catalysts (e.g., Co, Ni, or Cu) is constructed on metal oxide (e.g., MnO) microparticles, giving rise to a high-performance Co-MnO@C-CNTs anode in lithium-ion batteries (LIBs). An extremely high capacity of 1050 mAh g⁻¹, extraordinary rate capacities over 10 A g⁻¹, and a long lifespan over 500 cycles are demonstrated. The great features of Co-MnO@C-CNTs anode are further confirmed in LIBs when the nickel-rich cathode (e.g., LiNi_0.8Co_0.1Mn_0.1O₂) is used and charged at a high voltage over 4.5 V. A high-capacity retention of 71.5% can be maintained at 1 C over 150 cycles. The superior performance relates to the CNTs network, which not only acts as an “expressway network” for fast ion/electron transportation but also buffers structural variation. Moreover, the metal nanoparticles can also enhance the electrical conductivity and catalyze the (de-)lithiation of metal oxide, resulting in higher reversibility and long-term cyclability. This study opens a new avenue to prepare CNTs-based functional materials and also explores the potential applications of metal oxide-based anode for high-performance batteries.     

Recent Progress in MOF-Derived Porous Materials as Electrodes for High-Performance Lithium-Ion Batteries

In recent years, metal-organic frameworks, especially MOF-based derivatives, have been regarded as one of the best candidate electrode materials for the next generation of advanced materials, due to high porosity, large surface area, modifiable functional groups as well as controllable chemical composition. This review presents the corresponding synthesis methods, structural design, and electrochemical performance of MOF-derived materials, including metal oxides, metal sulfides, metal phosphides, and carbon materials, in high-performance lithium-ion batteries. Subsequently, the problems that exist in the current application of MOF-based derivatives as electrodes in lithium-ion batteries are discussed along with possible and feasible solutions. At last, some reasonable pathways and strategies for the design of MOF derivatives are also suggested.     

Low-Cost Zinc Substitution of Iron-Based Prussian Blue Analogs as Long Lifespan Cathode Materials for Fast Charging Sodium-Ion Batteries

Iron-based Prussian blue analogs (Fe-PBAs) are extensively studied as promising cathode materials for rechargeable sodium-ion batteries owing to their high theoretical capacity, low-cost and facile synthesis method. However, Fe-PBAs suffer poor cycle stability and low specific capacity due to the low crystallinity and irreversible phase transition during excess sodium-ion storage. Herein, a modified co-precipitation method to prepare highly crystallized PBAs is reported. By introducing an electrochemical inert element (Zn) to substitute the high-spin Fe in the Fe-PBAs (ZnFeHCF-2), the depth of charge/discharge is rationally controlled to form a highly reversible phase transition process for sustainable sodium-ion storage. Minor lattice distortion and highly reversible phase transition process of ZnFeHCF-2 during the sodium-ions insertion and extraction are proved by in-situ tests, which have significantly impacted the cycling stability. The ZnFeHCF-2 shows a remarkably enhanced cycling performance with capacity retention of 58.5% over 2000 cycles at 150 mA g⁻¹ as well as superior rate performance up to 6000 mA g⁻¹ (fast kinetics). Furthermore, the successful fabrication of the full cell on the as-prepared cathode and commercial hard carbon anode demonstrates their potential as high-performance electrode materials for large-scale energy storage systems.     

Recent Advances in Rational Electrode Designs for High‐Performance Alkaline Rechargeable Batteries

In recent years, noticeable progress is achieved regarding alkaline rechargeable batteries (ARBs). Due to their merits of safety and low cost, ARBs are considered promising energy storage sources for large‐scale grid energy storage, electric vehicles, and hybrid electric vehicles, as well as wearable and portable devices. While previous reviews have focused on specific topics associated with ARBs, providing a comprehensive review on rechargeable alkaline batteries is both timely and worthwhile. In this review, the recent progress in ARBs is summarized and the strategies underlying rational electrode designs for cathodes and anodes are highlighted, as well as their applications in full cells including flexible batteries. This review may pave the way for further designs of high‐performance alkaline batteries.     

Voltage Hysteresis in Transition Metal Oxide Cathodes for Li/Na-Ion Batteries

The pursuit of rechargeable batteries with high energy density has triggered enormous efforts in developing cathode materials for lithium/sodium (Li/Na)-ion batteries considering their extremely high specific capacity. Many materials are being researched for battery applications, and transition metal oxide materials with remarkable electrochemical performance stand out among numerous cathode candidates for next-generation battery. Notwithstanding the merits, daunting challenges persist in the quest for further battery developments targeting lower cost, longer lifespan, improved energy density and enhanced safety. This is, in part, because the voltage hysteresis between the charge and discharge cycles, is historically avoided in intercalation electrodes because of its association with structural disorder and electrochemical irreversibility. Given the great potential of these materials for next-generation batteries, a review of the recent understanding of voltage hysteresis is timely. This review presents the origin of their undesirable behaviors and materials design criteria to mitigate them by integrating various schools of thought. A large amount of progressive characterization techniques related to voltage hysteresis are summarized from the literature, along with the corresponding measurable range used in their determination. Finally, promising design trends with eliminated voltage hysteresis are tentatively proposed to revive these important cathode materials toward practical applications.     

Unveiling the Anionic Redox Chemistry in Phosphate Cathodes for Sodium-Ion Batteries

Anionic redox chemistry has aroused increasing attention in sodium-ion batteries (SIBs) by virtue of the appealing additional capacity. However, up to now, anionic redox reaction has not been reported in the mainstream phosphate cathodes for SIBs. Herein, the ultrathin VOPO₄ nanosheets are fabricated as promising cathodes for SIBs, where the oxygen redox reaction is first activated accompanied by reversible ClO₄⁻ (from the electrolyte) insertion/extraction. As a result, the VOPO₄ cathode harvests a record-high capacity (168 mAh g⁻¹ at 0.1 C) among its counterparts ever reported. Moreover, the ClO₄⁻ insertion efficiently expands the interlayer spacing of VOPO₄ and accelerates the ion diffusion, enabling an unprecedentedly high rate performance (69 mAh g⁻¹ at 30 C). Via systematic ex situ characterizations and theoretical computations, the anionic redox chemistry and charge storage mechanism upon cycling are thoroughly elucidated. This study opens up a new avenue toward high-energy phosphate cathodes for SIBs by triggering anionic redox reactions.     

Fast-Charging and Ultrahigh-Capacity Zinc Metal Anode for High-Performance Aqueous Zinc-Ion Batteries

Although some strategies have been triggered to address the intrinsic drawbacks of zinc (Zn) anodes in aqueous Zn-ion batteries (ZIBs), the larger issue of Zn anodes unable to cycle at a high current density with large areal capacity is neglected. Herein, the zinc phosphorus solid solution alloy (ZnP) coated on Zn foil (Zn@ZnP) prepared via a high-efficiency electrodeposition method as a novel strategy is proposed. The phosphorus (P) atoms in the coating layer are beneficial to fast ion transfer and reducing the electrochemical activation energy during Zn stripping/plating processes. Besides, a lower energy barrier of Zn²⁺ transferring into the coating can be attained due to the additional P. The results show that the as-prepared Zn@ZnP anode in the symmetric cell can be cycled at a current density of 15 mA cm⁻² with an areal capacity of 48 mAh cm⁻² (depth of discharge, DOD ≈ 82%) and even at an ultrahigh current density of 20 mA cm⁻² and DOD ≈ 51%. Importantly, a discharge capacity of 154.4 mAh g⁻¹ in the Zn/MnO₂ full cell can be attained after 1000 cycles at 1 A g⁻¹. The remarkable effect achieved by the developed strategy confirms its prospect in the large-scale application of ZIBs for high-power devices.     

Sn Alloying to Inhibit Hydrogen Evolution of Zn Metal Anode in Rechargeable Aqueous Batteries

The detrimental hydrogen evolution side reaction is one of the major issues hindering the commercialization of Zn metal anode in high-safety and low-cost rechargeable aqueous batteries. Herein, the authors present a Sn alloying approach to effectively inhibit the hydrogen evolution and dendrite growth of the Zn metal anode. Through in situ monitoring of the hydrogen production during repeated plating/stripping tests, it is quantitatively demonstrated that the hydrogen evolution of alloy electrode with appropriate Sn amount is only half of that of pure Zn electrode. Furthermore, the Sn alloying allows for favorable Zn nucleation sites, lowering the Zn nucleation energy barrier and promoting more uniform Zn deposition. The Zn-Sn alloy electrode offers much-improved plating/stripping cycling, that is, over 240 h at 5 mA cm^?2 and 35.2% depth of discharge. This work provides a practically viable strategy to stabilize Zn metal electrode in rechargeable aqueous batteries.     

Recent Advances in Transition Metal Nitride-Based Materials for Photocatalytic Applications

Photocatalysis is a promising and convenient strategy to convert solar energy into chemical energy for various fields. However, photocatalysis still suffers from low solar energy conversion efficiency. Developing state of the art photocatalysts with high efficiency and low cost is a huge challenge. Transition metal nitrides (TMNs) as a class of metallic interstitial compounds have attracted significant attention in photocatalytic applications. In fact, TMNs exhibit multifunctional properties in various photocatalytic systems. This review is the first attempt that summarizes recent research on TMNs-based materials in various photocatalytic applications. Different roles of TMNs materials in photocatalytic systems including semiconductor active components, co-catalysts, inter-band excitation, and surface plasmon resonance components are systematically discussed and summarized. The fundamentals, latest progress, and emerging opportunities for further improving the performances of TMNs-based materials for photocatalysis are also discussed. Finally, some challenges facing TMNs, and perspectives on their future that are relevant for furthering research in the area of photocatalysis are also proposed.     

Application of 2D MXene in Organic Electrode Materials for Rechargeable Batteries: Recent Progress and Perspectives

Organic electrode materials (OEMs) are emerging green power because of the promising advantages such as environmental friendliness, abundant sources, easy recycling, and structural diversity. However, several inherent issues, including low electronic conductivity, dissolution of active materials, and particle pulverization restrict their practical application. MXene, as a novel 2D material has exhibited enormous potential to solve the issues of OEMs due to its high conductivity, unique structure, exceptional mechanical property, and abundant surface groups. Up to now, various effective strategies have been presented and achieved positive effects, such as constructing heterojunction structures, in situ assembly, dip-coating, preparing free-standing MXene paper, etc. Nonetheless, comprehensive review of the progress and status is rare. Herein, an overview of the application of MXene in organic electrode materials for rechargeable batteries is systematically put forward. Meanwhile, recent progress and future development directions are presented. This review can serve as a guide for future research.     

Critical Review of Fluorinated Electrolytes for High-Performance Lithium Metal Batteries

Lithium metal batteries (LMBs), due to their ultra-high energy density, are attracting tremendous attentions. However, their commercial application is severely impeded by poor safety and unsatisfactory cycling stability, which are induced by lithium dendrites, side reactions, and inferior anodic stability. Electrolytes, as the indispensable and necessary components in lithium metal batteries, play a crucial role in regulating the electrochemical performance of LMBs. Recently, the fluorinated electrolytes are widely investigated in high-performance LMBs. Thus, the design strategies of fluorinated electrolytes are thoroughly summarized, including fluorinated salts, fluorinated solvents, and fluorinated additives in LMBs, and insights of the fluorinated components in suppressing lithium dendrites, improving anodic stability and cycling stability. Finally, an outlook with several design strategies and challenges will be proposed for novel fluorinated electrolytes.     

Recent Advances and Optimization Strategies on the Electrolytes for Hard Carbon and P-Based Sodium-Ion Batteries

Hard carbons (HCs) and P-based materials (including red phosphorus, black phosphorus, and metal phosphides) represent the most promising anodes for the commercialization of sodium ion batteries. The electrochemical performance of SIBs is determined not only by the structure of electrode materials, but it is also highly dependent on the matched electrolyte. In this review, the optimization, the matching strategies and the advanced characterization techniques of the electrolytes system for HCs and P-based anodes are discussed based on the recent advance. The effective optimization strategies are summarized from three aspects: sodium salts, solvents, and additives. The challenges and perspectives are also discussed in this review.     

Unleashing the Potential of Sodium-Ion Batteries: Current State and Future Directions for Sustainable Energy Storage

Rechargeable sodium-ion batteries (SIBs) are emerging as a viable alternative to lithium-ion battery (LIB) technology, as their raw materials are economical, geographically abundant (unlike lithium), and less toxic. The matured LIB technology contributes significantly to digital civilization, from mobile electronic devices to zero electric-vehicle emissions. However, with the increasing reliance on renewable energy sources and the anticipated integration of high-energy-density batteries into the grid, concerns have arisen regarding the sustainability of lithium due to its limited availability and consequent price escalations. In this context, SIBs have gained attention as a potential energy storage alternative, benefiting from the abundance of sodium and sharing electrochemical characteristics similar to LIBs. Furthermore, high-entropy chemistry has emerged as a new paradigm, promising to enhance energy density and accelerate advancements in battery technology to meet the growing energy demands. This review uncovers the fundamentals, current progress, and the views on the future of SIB technologies, with a discussion focused on the design of novel materials. The crucial factors, such as morphology, crystal defects, and doping, that can tune electrochemistry, which should inspire young researchers in battery technology to identify and work on challenging research problems, are also reviewed.     

Highly Symmetrical Six-Transition Metal Ring Units Promising High Air-Stability of Layered Oxide Cathodes for Sodium-Ion Batteries

Layered oxides are the most prevalent cathodes for sodium-ion batteries (SIBs), but their poor air stability significantly limits their practical application owing to the rapid performance degradation of aged materials and the cost increase for material storage and transportation. Here, an effective strategy of constructing stable transition metal (TM) layers with a highly symmetrical six-TM ring is suggested to enhance structure stability, thus hindering ambient air corrosion. The density functional theory calculations reveal that the higher symmetry ensures a higher thermodynamic energy for H₂O insertion into Na layer. The combined analyses of selected area electron diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and chemical titration indicate that the six-TM ring structure can effectively suppress the series of aging processes including water insertion, the spontaneous loss of lattice sodium, TM valence increment and residual alkali formation. Benefiting from the overall suppression of aging process, the strategy results in an excellent improvement in capacity retention after air exposure from 13.57% to 95.59%, and exhibits a good universality for both P2- and O3-cathodes, which are the two most common structures of Na-based layered oxides with different aging mechanism. These findings provide new insight to design high-performance cathodes for SIBs.     

Reactivating the Dead Lithium by Redox Shuttle to Promote the Efficient Utilization of Lithium for Anode Free Lithium Metal Batteries

Anode free lithium metal batteries (AFLMBs), as a kind of novel battery configuration with zero excess lithium, can improve the energy density to the limit compared with lithium metal batteries and effectively ensure the safety. However, the lifespan of AFLMBs is a tricky problem because there is no extra lithium source to compensate for the irreversible loss of active lithium, which is mainly caused by the continuous decomposition of electrolyte and the formation of dead lithium. Herein, a redox shuttle additive, which can be oxidized in the cathode and reduced in the electrolyte reversibly, is introduced to improve the lithium utilization and lifespan of AFLMBs by reactivating the dead lithium. During the charging process, the redox shuttle additive can be oxidized on the cathode surface and serve as electron acceptor toward dead lithium. The electrically isolated dead lithium in the electrolyte can be re-activated into active lithium ions when captured by oxidized redox shuttle additive.As a result, electrolyte with redox shuttle achieves average higher coulombic efficiency of 99.13% than electrolyte without redox shuttle (97.71%). In addition, the AFLMB with redox shuttle exhibits improved cycling performance with extended lifespan.     

Crumpling Carbon-Pillared Atomic-Thin Dichalcogenides and CNTs into Elastic Balls as Superior Anodes for Sodium/Potassium-Ion Batteries

With abundant electroactive sites and rapid ion diffusion paths, ultrathin dichalcogenides such as MoS₂ demonstrate enormous potential as anodes for sodium/potassium-ion batteries (SIBs/PIBs). However, ultrahigh-aspect-ratio nanosheets are very easy to aggregate and re-stack, drastically weakening their intrinsic merits. Here a sustainable dichalcogenide anode is designed via crumpling carbon-pillared atomic-thin MoS₂ nanosheets with CNTs into an elastic ball structure (C-p-MoS₂/CNTs). In this architecture, the glucose-derived carbon pillars atomic-thin MoS₂ nanosheets and broadens interlayer spacing, ensuring fast Na⁺/K⁺ diffusion; CNTs act as 3D scaffolds to impede re-stacking of MoS₂ while providing high-speed pathways for electrons; the integration of flexible atomic-thin sheets and high-toughness CNTs further endows the balls with great elasticity to release the cycling stress. Consequently, the C-p-MoS₂/CNTs material delivers high reversible capacities, outstanding cycling stability, and superior rate performance as anodes for both SIBs and PIBs. Pairing with Na₃V₂(PO₄)₂F₃ cathode, the sodium-ion coin-cell could operate at a rate up to 50 C at high mass loading of 9.4 mg cm⁻² and manifest ultrastable cycling stability at 40 C over 600 cycles. Impressively, the assembled pouch cell can be cycled stably with a high energy density of 188 Wh kg⁻¹. This study is anticipated to provide inspiration for designing innovative metal dichalcogenides as battery anodes.