Space-confined manganese oxides nanosheets for efficient catalytic decomposition of ozone

Ground-level ozone has long posed a substantial menace to human well-being and the ecological milieu. The widely reported manganese-based catalysts for ozone decomposition still facing the persisting issues encompass inefficiency and instability. To surmount these challenges, we developed a mesoporous silica thin films with perpendicular nanochannels (SBA(⊥)) confined Mn3O4 catalyst (Mn3O4@SBA(⊥)). Under a weight hourly space velocity (WHSV) of 500,000 mL g-1 h-1, the Mn3O4@SBA(⊥) catalyst exhibited 100% ozone decomposition efficiency in 5 h and stability across a wide humidity range, which exceed the performance of bulk Mn3O4 and Mn3O4 confine in commonly reported SBA-15. Rapidly decompose 20 ppm O3 to a safety level below 100 μg m-3 in the presence of dust in smog chamber (60 × 60 × 60 cm) was also realized. This prominent catalytic performance can be attributed to the unique confined structure engenders the highly exposed active sites, facilitate the reactant-active sites contact and impeded the water accumulation on the active sites. This work offers new insights into the design of confined structure catalysts for air purification.

Shielding Mn3+ Disproportionation with Graphitic Carbon-Interlayered Manganese Oxide Cathodes for Enhanced Aqueous Energy Storage System

Manganese dioxide (MnO2) materials have recently garnered attention as prospective high-capacity cathodes, owing to their theoretical two-electron redox reaction in charge storage processes. However, their practical application in aqueous energy storage systems faces a formidable challenge: the disproportionation of Mn3+ ions, leading to a significant reduction in their capacity. To address this limitation, the study presents a novel graphitic carbon interlayer-engineered manganese oxide (CI-MnOx) characterized by an open structure and abundant defects. This innovative material serves several essential functions for efficient aqueous energy storage. First, a graphitic carbon layer coats the MnOx molecular interlayer, effectively inhibiting Mn3+ disproportionation and substantially enhancing electrode conductivity. Second, the phase variation within MnOx generates numerous crystal defects, vacancies, and active sites, optimizing electron-transfer capability. Third, the flexible carbon layer acts as a buffer, mitigating the volume expansion of MnOx during extended cycling. The synergistic effects of these features result in the CI-MnOx exhibiting an impressive high capacity of 272 mAh g-1 (1224 F g-1) at 0.25 A g-1. Notably, the CI-MnOx demonstrates zero capacity loss after 90 000 cycles (≈3011 h), an uncommon longevity for manganese oxide materials. Spectral characterizations reveal reversible cation intercalation and conversion reactions with multielectron transfer in a LiCl electrolyte.

Multi-Ion Engineering Strategies toward High Performance Aqueous Zinc-Based Batteries

As alternatives to batteries with organic electrolytes, aqueous zinc-based batteries (AZBs) have been intensively studied. However, the sluggish kinetics, side reactions, structural collapse, and dissolution of the cathode severely compromise the commercialization of AZBs. Among various strategies to accelerate their practical applications, multi-ion engineering shows great feasibility to maintain the original structure of the cathode and provide sufficient energy density for high-performance AZBs. Though multi-ion engineering strategies could solve most of the problems encountered by AZBs and show great potential in achieving practical AZBs, the comprehensive summaries of the batteries undergo electrochemical reactions involving more than one charge carrier is still in deficiency. The ambiguous nomenclature and classification are becoming the fountainhead of confusion and chaos. In this circumstance, this review overviews all the battery configurations and the corresponding reaction mechanisms are investigated in the multi-ion engineering of aqueous zinc-based batteries. By combing through all the reported works, this is the first to nomenclate the different configurations according to the reaction mechanisms of the additional ions, laying the foundation for future unified discussions. The performance enhancement, fundamental challenges, and future developing direction of multi-ion strategies are accordingly proposed, aiming to further accelerate the pace to achieve the commercialization of AZBs with high performance.

Application-Based Prospects for Dual-Ion Batteries

Dual-ion batteries (DIBs) exhibit a distinct set of performance advantages and disadvantages due to their unique storage mechanism. However, the current cyclability/energy density tradeoffs of anion storage paired with the intrinsic required electrolyte loadings of conventional DIBs preclude their widespread adoption as an alternative to lithium-ion batteries (LIBs). Despite this, their reduced desolvation penalty and low-cost electrode materials may warrant their employment for low-temperature and/or grid storage applications. To expand beyond these applications, this Perspective reviews the prospects of solid salt storage and halogen intercalation-conversion as viable methods to increase DIB energy densities to a level on-par with LIBs. Fundamental limitations of conventional DIBs are examined, technology spaces are proposed where they can make meaningful impact over LIBs, and potential strategies are outlined to improve cell-level energy densities necessary for the widespread adoption of DIBs.

Charge Carriers for Aqueous Dual-Ion Batteries

Environmental and safety concerns of energy storage systems call for application of aqueous battery systems which have advantages of low cost, environmental benignity, safety, and easy assembling. Among the aqueous battery systems, aqueous dual-ion batteries (ADIBs) provide high possibility for achieving excellent battery performance. Compared with the "rocking chair" batteries with only one type of carrier involved in the charging and discharging, ADIBs with both cations and anions as charge carriers possess diverse selections of electrodes and electrolytes. Charge carriers are the basis of the configuration of ADIBs. In this Review, cations and anions that could be applied in ADIBs are demonstrated with corresponding electrode materials and favorable electrolytes. Some insertion mechanisms are emphasized to provide insights for the possibilities to enhance the practical performances of ADIBs.

Spreading the Landscape of Dual Ion Batteries: from Electrode to Electrolyte

The working mechanism of a dual-ion battery (DIB) differs from that of a lithium-ion battery (LIB) in that the anions in the electrolyte of the former can be intercalated as well. Researchers have been paying close attention to this device because of its high voltage, low price, and environmental friendliness. However, DIBs are still in their early research stages, and numerous issues need to be addressed and investigated further. Initially, this Review explains how DIBs work in principle and discusses the progress of electrode materials for cathode and anode. Furthermore, since the electrolytes used as the active material, as well as anion, solvent, and additives, have a significant impact on the DIB's capacity and voltage, the current status is also presented in terms of electrolytes, followed by an outlook on confronting the challenges. A comprehensive summary from electrode to electrolyte will guide the development of next-generation DIBs.

Co-Intercalation of Dual Charge Carriers in Metal-Ion-Confining Layered Vanadium Oxide Nanobelts for Aqueous Zinc-Ion Batteries

Vanadium-based oxides with high theoretical specific capacities and open crystal structures are promising cathodes for aqueous zinc-ion batteries (AZIBs). In this work, the confined synthesis can insert metal ions into the interlayer spacing of layered vanadium oxide nanobelts without changing the original morphology. Furthermore, we obtain a series of nanomaterials based on metal-confined nanobelts, and describe the effect of interlayer spacing on the electrochemical performance. The electrochemical properties of the obtained Al_2.65 V₆ O₁₃  ⋅ 2.07H₂ O as cathodes for AZIBs are remarkably improved with a high initial capacity of 571.7 mAh ⋅ g^-1 at 1.0 A g^-1 . Even at a high current density of 5.0 A g^-1 , the initial capacity can still reach 205.7 mAh g^-1 , with a high capacity retention of 89.2 % after 2000 cycles. This study demonstrates that nanobelts confined with metal ions can significantly improve energy storage applications, revealing new avenues for enhancing the electrochemical performance of AZIBs.

Boosting the Cycling Stability of Aqueous Zinc-Ion Batteries through Nanofibrous Coating of a Bead-like MnOx Cathode

Rechargeable aqueous zinc-ion batteries (AZIBs) are close complements to lithium-ion batteries for next-generation grid-scale applications owing to their high specific capacity, low cost, and intrinsic safety. Nevertheless, the viable cathode materials (especially manganese oxides) of AZIBs suffer from poor conductivity and inferior structural stability upon cycling, thereby impeding their practical applications. Herein, a facile synthetic strategy of bead-like manganese oxide coated with carbon nanofibers (MnO_x-CNFs) based on electrospinning is reported, which can effectively improve the electron/ion diffusion kinetics and provide robust structural stability. These benefits of MnO_x-CNFs are evident in the electrochemical performance metrics, with a long cycling durability (i.e., a capacity retention of 90.6% after 2000 cycles and 71% after 5000 cycles) and an excellent rate capability. Furthermore, the simultaneous insertion of H⁺/Zn²⁺ and the Mn redox process at the surface and in the bulk of MnO_x-CNFs are clarified in detail. Our present study not only provides a simple avenue for synthesizing high-performance Mn-based cathode materials but also offers unique knowledge on understanding the corresponding electrochemical reaction mechanism for AZIBs.

Magneto-Electrodeposition of 3D Cross-Linked NiCo-LDH for Flexible High-Performance Supercapacitors

Layered double hydroxides (LDHs) with outstanding redox activity on flexible current collectors can serve as ideal cathode materials for flexible hybrid supercapacitors in wearable energy storage devices. Electrodeposition is a facile, time-saving, and economical technique to fabricate LDHs. The limited loading mass induced by insufficient mass transport and finite exposure of active sites, however, greatly hinders the improvement of areal capacity. Herein, magneto-electrodeposition (MED) under high magnetic fields up to 9 T is developed to fabricate NiCo-LDH on flexible carbon cloth (CC) as well as Ti₃ C₂ T_x functionalized CC. Owing to the magneto-hydrodynamic effect induced by magnetic-electric field coupling, the loading mass and exposure of active sites are significantly increased. Moreover, a 3D cross-linked nest-like microstructure is constructed. The MED-derived NiCo-LDH delivers an ultrahigh areal capacity of 3.12 C cm^-2 at 1 mA cm^-2 and as-fabricated flexible hybrid supercapacitors show an excellent energy density with an outstanding cycling stability. This work provides a novel route to improve electrochemical performances of layered materials through MED technique.

Ultra-High-Capacity and Dendrite-Free Zinc-Sulfur Conversion Batteries Based on a Low-Cost Deep Eutectic Solvent

Traditional cathodes for aqueous Zn-ion batteries are afflicted by a limited specific capacity and fearful Zn dendrites. Herein, these troubles are disposed of with a conversion-type Zn-S battery and low-cost deep eutectic solvent (DES). By utilizing the optimized electrolyte, the symmetrical Zn battery can stably cycle over 3920 h, which also confers on the Zn-S battery an ultrahigh specific capacity of ∼846 mA h g_S^-1 and energy density of 259 W h kg^-1 at 0.5 A g^-1. Importantly, the conversion chemistry of S and ZnS is responsible for the superior anti-self-discharge behavior (capacity retention: 94.58 and 68.58% after standing for 72 and 288 h versus Zn//VO₂ battery: 76.82 and 47.80% after resting for 24 and 72 h versus Zn//MnO₂ battery: 95.96 and 91.57% after resting for 24 and 72 h, respectively). This work is the first authentication of Zn-S batteries based on a newly developed low-cost DES-based electrolyte, which meanwhile settles the deep-rooted low specific capacity and infamous Zn dendrite issues in conventional (de)intercalation Zn-ion batteries.

Reversible electrochemical conversion from selenium to cuprous selenide

Using elemental selenium as an electrode, the redox-active Cu²⁺/Cu⁺ ion is reversibly hosted via the sequential conversion reactions of Se → CuSe → Cu₃Se₂ → Cu₂Se. The four-electron redox process from Se to Cu₂Se produces a high initial specific capacity of 1233 mA h g^-1 based on the mass of selenium alone or 472 mA h g^-1 based on the mass of Cu₂Se, the fully discharged product.

Molecular Coupling and Self-Assembly Strategy toward WSe2 /Carbon Micro-Nano Hierarchical Structure for Elevated Sodium-Ion Storage

Sodium (Na) ion-based dual-ion batteries (Na-DIBs) have attracted great attention, owing to their benefits of low cost, high working voltage, and environmental friendliness. However, the limited capacity and low tap density of currently reported anode materials restrict the further improvement of Na-DIBs. Herein, a micro-nano structure with vertically aligned WSe₂ nanoflakes anchored tightly on a micron-sized carbon sphere (WSe₂ /CS) is successfully constructed via combining the molecular coupling and self-assembly strategy. Within this hierarchical structure, the WSe₂ nanoflakes can shorten the diffusion path for Na⁺ ions and alleviate structural deformation during the charge/discharge process; meanwhile, the micron-sized carbon core provides conductive support and helps improve the total tap density of the anode electrode. As a result, this micron-sized WSe₂ /CS displays a high specific capacity of ≈252.8 mAh g^-1 and good cycling performance with ≈92% capacity retention after 1200 cycles. Moreover, by pairing this WSe₂ /CS anode with environmental friendly graphite as cathode, a proof-of-concept Na-DIB shows 85.6% capacity retention after 1000 cycles, which is among the best performances of previously reported Na-DIBs.

High-Capacity Aqueous Storage in Vanadate Cathodes Promoted by the Zn-Ion and Proton Intercalation and Conversion-Intercalation of Vanadyl Ions

Aqueous Zn-ion batteries (AZIBs) are promising alternatives to lithium-ion batteries in stationary storage. However, limited storage capacity and cyclic life impede their large-scale implementation. We report reversible electrochemical insertion of multi-ions into sodium vanadate (NaV₃O₈) cathode materials for AZIBs, achieving a maximum storage capacity of 450 mAh g^-1 at 0.05 A g^-1 and a capacity retention of 82% after 500 cycles at 0.4 A g^-1. In addition to Zn²⁺ and H⁺ insertion, in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) collectively provide explicit evidence on vanadyl ions (VO²⁺) conversion-intercalation at the NaV₃O₈ cathode, showing the deintercalation of VO²⁺ from NaV₃O₈ and the consequent conversion of VO²⁺ into V₂O₅ on charging, and vice versa on discharging. Our study is the first to report on the cation conversion-intercalation mechanism in AZIBs. This reversible multi-ion storage mechanism provides a design principle for developing high-capacity aqueous electrode materials by engaging both the intercalation and conversion of charge carriers.

Manipulating anion intercalation enables a high-voltage aqueous dual ion battery

Aqueous graphite-based dual ion batteries have unique superiorities in stationary energy storage systems due to their non-transition metal configuration and safety properties. However, there is an absence of thorough study of the interactions between anions and water molecules and between anions and electrode materials, which is essential to achieve high output voltage. Here we reveal the four-stage intercalation process and energy conversion in a graphite cathode of anions with different configurations. The difference between the intercalation energy and hydration energy of bis(trifluoromethane)sulfonimide makes the best use of the electrochemical stability window of its electrolyte and delivers a high intercalation potential, while BF₄⁻ and CF₃SO₃⁻ do not exhibit a satisfactory potential because the graphite intercalation potential of BF₄⁻ is inferior and the graphite intercalation potential of CF₃SO₃⁻ exceeds the voltage window of its electrolyte. An aqueous dual ion battery based on the intercalation behaviors of bis(trifluoromethane)sulfonimide anions into a graphite cathode exhibits a high voltage of 2.2 V together with a specific energy of 242.74 Wh kg⁻¹. This work provides clear guidance for the voltage plateau manipulation of anion intercalation into two-dimensional materials.

The interactions between water molecules, electrode materials and anions are essential yet challenging for aqueous dual ion batteries. Here, the authors demonstrate the voltage manipulation of dual ion batteries through matching intercalation energy and solvation energy of different anions.

A universal strategy towards high-energy aqueous multivalent-ion batteries

Rechargeable multivalent metal (e.g., Ca, Mg or, Al) batteries are ideal candidates for large–scale electrochemical energy storage due to their intrinsic low cost. However, their practical application is hampered by the low electrochemical reversibility, dendrite growth at the metal anodes, sluggish multivalent–ion kinetics in metal oxide cathodes and, poor electrode compatibility with non–aqueous organic–based electrolytes. To circumvent these issues, here we report various aqueous multivalent–ion batteries comprising of concentrated aqueous gel electrolytes, sulfur–containing anodes and, high-voltage metal oxide cathodes as alternative systems to the non–aqueous multivalent metal batteries. This rationally designed aqueous battery chemistry enables satisfactory specific energy, favorable reversibility and improved safety. As a demonstration model, we report a room–temperature calcium-ion/sulfur| |metal oxide full cell with a specific energy of 110 Wh kg^–1 and remarkable cycling stability. Molecular dynamics modeling and experimental investigations reveal that the side reactions could be significantly restrained through the suppressed water activity and formation of a protective inorganic solid electrolyte interphase. The unique redox chemistry of the multivalent–ion system is also demonstrated for aqueous magnesium–ion/sulfur||metal oxide and aluminum–ion/sulfur||metal oxide full cells.

Rechargeable multivalent-ion batteries are promising candidates for future energy storage technologies. Here, the authors develop various aqueous multivalent-ion cells using concentrated aqueous gel electrolytes, sulfur-containing anodes, and high-voltage metal oxide cathodes.

Emerging trends in anion storage materials for the capacitive and hybrid energy storage and beyond

Electrochemical capacitors charge and discharge more rapidly than batteries over longer cycles, but their practical applications remain limited due to their significantly lower energy densities. Pseudocapacitors and hybrid capacitors have been developed to extend Ragone plots to higher energy density values, but they are also limited by the insufficient breadth of options for electrode materials, which require materials that store alkali metal cations such as Li⁺ and Na⁺. Herein, we report a comprehensive and systematic review of emerging anion storage materials for performance- and functionality-oriented applications in electrochemical and battery-capacitor hybrid devices. The operating principles and types of dual-ion and whole-anion storage in electrochemical and hybrid capacitors are addressed along with the classification, thermodynamic and kinetic aspects, and associated interfaces of anion storage materials in various aqueous and non-aqueous electrolytes. The charge storage mechanism, structure-property correlation, and electrochemical features of anion storage materials are comprehensively discussed. The recent progress in emerging anion storage materials is also discussed, focusing on high-performance applications, such as dual-ion- and whole-anion-storing electrochemical capacitors in a symmetric or hybrid manner, and functional applications including micro- and flexible capacitors, desalination, and salinity cells. Finally, we present our perspective on the current impediments and future directions in this field.

Ferrocene-Based Mixed-Valence Metal-Organic Framework as an Efficient and Stable Cathode for Lithium-Ion-Based Dual-Ion Battery

Organic anion-hosting cathodes are remarkably attractive platform candidates for lithium-ion-based dual-ion batteries (LDIBs) due to their various advantages such as variety, designable, and adjustable. Here, a new organic anion-hosting mixed-valence metal-organic framework cathode (Co₂^IICo^III(DFc)₂(OH)₃·H₂O, abbreviated as Co(DFc)x) is first employed in LDIBs. With the redox reactions happening in the couples of Fe²⁺/Fe³⁺ and Co²⁺/Co³⁺, PF₆^- anions can be incorporated into the cathode and reversibly released into the LiPF₆-based electrolyte. Meanwhile, benefiting from its unique structure and insolubility, Co(DFc)x shows a high energy density of 632 Wh kg^-1 (vs lithium anode), a high operating potential of 3.63 V (vs Li⁺/Li), a high reversible (discharge) capacity of 170 mAh g^-1 at 50 mA g^-1 (the third cycle), an excellent rate performance (up to 2000 mA g^-1, 5 min for one cycle), and extraordinary cycling stability (an average capacity of 74.9 mAh g^-1 for 8000 cycles at 2000 mA g^-1).

Roadmap for advanced aqueous batteries: From design of materials to applications

Safety concerns about organic media-based batteries are the key public arguments against their widespread usage. Aqueous batteries (ABs), based on water which is environmentally benign, provide a promising alternative for safe, cost-effective, and scalable energy storage, with high power density and tolerance against mishandling. Research interests and achievements in ABs have surged globally in the past 5 years. However, their large-scale application is plagued by the limited output voltage and inadequate energy density. We present the challenges in AB fundamental research, focusing on the design of advanced materials and practical applications of whole devices. Potential interactions of the challenges in different AB systems are established. A critical appraisal of recent advances in ABs is presented for addressing the key issues, with special emphasis on the connection between advanced materials and emerging electrochemistry. Last, we provide a roadmap starting with material design and ending with the commercialization of next-generation reliable ABs.

Stable Interface between a NaCl-AlCl3 Melt and a Liquid Ga Negative Electrode for a Long-Life Stationary Al-Ion Energy Storage Battery

Intermediate temperature NaCl-AlCl₃-based Al-ion batteries are considered as a promising stationary energy storage system due to their low cost, high safety, etc. However, such a cheap electrolyte has a critical feature, i.e., strong corrosion, which results in the short cycle life of the conventional Al-metal anode and also limits the development of the NaCl-AlCl₃-based Al-ion batteries. A noncorrosive electrolyte may be a good choice for addressing the above challenge, while it is difficult to obtain the electrolyte that has advantages of both noncorrosion and low cost. Therefore, here, we report a Ga-metal anode in the affordable NaCl-AlCl₃ electrolyte for constructing a long-life stationary Al-ion energy storage system. This featured liquid metal anode shows good alloying and dealloying processes between metallic Ga and Al, as well as renders superior stability of the interface between the electrolyte and the anode (e.g., smoothly running for over 580 h at 2 mA cm^-2). No-corrosion and no-pulverization problems appear in this novel liquid/liquid interface. Those advantages demonstrate that the liquid Ga-metal anode has a great promise for the improvement of the NaCl-AlCl₃-based Al-ion batteries for large-scale stationary energy storage applications.