Architecting a Stable High-Energy Aqueous Al-Ion Battery

An artificial aluminum-tin alloy layer on aluminum metal anodes for ultra-stable rechargeable aluminum-ion batteries

Rechargeable aluminum ion batteries (RAIBs) exhibit great potential for next-generation energy storage systems owing to the abundant resources, high theoretical volumetric capacity and light weight of the Al metal anode. However, the development of RAIBs based on Al metal anodes faces challenges such as dendrite formation, self-corrosion, and volume expansion at the anode/electrolyte interface, which needs the rational design of an aluminum anode for high-performance RAIBs. This work proposes a novel and low-cost strategy by utilizing an alloy electrodeposition method in a low-temperature molten salt system to fabricate an aluminum-tin (AlSn) alloy coating layer on copper foil as the anode for RAIBs, which successfully addresses the issues of dendrite formation and corrosion at the anode/electrolyte interface. The artificial AlSn alloy layer could enhance the active sites for metal Al homogeneous deposition and effectively retard the dendrite formation, which was verified by an in situ optical microscopy study. The symmetric AlSn@Cu cell demonstrates a low average overpotential of ∼38 mV at a current density of 0.5 mA cm-2 and a long-term lifespan of over 1100 h. Moreover, the AlSn@Cu//Mo6S8 full cells deliver a high capacity of 114.9 mA h g-1 at a current density of 100 mA g-1 and maintain ultra-stable cycling stability even over 1400 cycles with a ∼100% coulombic efficiency (CE) during the long-term charge/discharge processes. This facile alloy electrodeposition approach for designing high-performance Al-based anodes provides insights into the understanding of artificial interface chemistry on Al-based anodes and potentially accelerates the design of high-performance RAIBs.

Recent progress in aqueous aluminum-ion batteries

Aqueous aluminum-ion batteries have many advantages such as their safety, environmental friendliness, low cost, high reserves and the high theoretical specific capacity of aluminum. So aqueous aluminum-ion batteries are potential substitute for lithium-ion batteries. In this paper, the current research status and development trends of cathode and anode materials and electrolytes for aqueous aluminum-ion batteries are described. Aiming at the problem of passivation, corrosion and hydrogen evolution reaction of aluminum anode and dissolution and irreversible change of cathode after cycling in aqueous aluminum-ion batteries. Solutions of different research routes such as ASEI (artificial solid electrolyte interphase), alloying, amorphization, elemental doping, electrolyte regulation, etc and different transformation mechanisms of anode and cathode materials during cycling have been summarized. Moreover, it looks forward to the possible research directions of aqueous aluminum-ion batteries in the future. We hope that this review can provide some insights and support for the design of more suitable electrode materials and electrolytes for aqueous aluminum-ion batteries.

Unlocking the Potential of 2D MoS2 Cathodes for High-Performance Aqueous Al-Ion Batteries: Deciphering the Intercalation Mechanisms

In recent years, there have been significant advancements in Al-ion battery development, resulting in high voltage and capacity. Traditionally, only carbon-based materials with layered structures and strong bonding capabilities can deliver superior performance. However, most other materials exhibited low discharge voltages of 1.4 V, especially in aqueous Al-ion battery systems lacking anion intercalation. Thus, the development of high-voltage cathode materials has become crucial. This study introduces 2D MoS2 as a high-performance cathode for aqueous Al-ion batteries. The material's interlayer structure enables the intercalation of AlCl4 - anions, resulting in high-voltage intercalation. The resulting battery achieved a high voltage of 1.8 V with a capacity of 750 mAh g-1, contributing to a high energy density of 890 Wh kg-1 and an impressive retention rate of ≈100% after 200 cycles. This research not only sheds light on the high-voltage anion-intercalation mechanism of MoS2 but also paves the way for the further development of advanced cathode materials in the field of Al-ion batteries. By demonstrating the potential of using 2D MoS2 as a cathode material, this finding can lead to the development of more efficient and innovative energy storage technologies, ultimately contributing to a sustainable and green energy future.

Benzoquinone-Lubricated Intercalation in Manganese Oxide for High-Capacity and High-Rate Aqueous Aluminum-Ion Battery

Aqueous aluminum-ion batteries are attractive post-lithium battery technologies for large-scale energy storage in virtue of abundant and low-cost Al metal anode offering ultrahigh capacity via a three-electron redox reaction. However, state-of-the-art cathode materials are of low practical capacity, poor rate capability, and inadequate cycle life, substantially impeding their practical use. Here layered manganese oxide that is pre-intercalated with benzoquinone-coordinated aluminum ions (BQ-AlxMnO2) as a high-performance cathode material of rechargeable aqueous aluminum-ion batteries is reported. The coordination of benzoquinone with aluminum ions not only extends interlayer spacing of layered MnO2 framework but reduces the effective charge of trivalent aluminum ions to diminish their electrostatic interactions, substantially boosting intercalation/deintercalation kinetics of guest aluminum ions and improving structural reversibility and stability. When coupled with Zn50Al50 alloy anode in 2 m Al(OTf)3 aqueous electrolyte, the BQ-AlxMnO2 exhibits superior rate capability and cycling stability. At 1 A g-1, the specific capacity of BQ-AlxMnO2 reaches ≈300 mAh g-1 and retains ≈90% of the initial value for more than 800 cycles, along with the Coulombic efficiency of as high as ≈99%, outperforming the AlxMnO2 without BQ co-incorporation.

Interface Engineering for Aqueous Aluminum Metal Batteries: Current Progresses and Future Prospects

Aqueous aluminum metal batteries (AMBs) have attracted numerous attention because of the abundant reserves, low cost, high theoretical capacity, and high safety. Nevertheless, the poor thermodynamics stability of metallic Al anode in aqueous solution, which is caused by the self-corrosion, surface passivation, or hydrogen evolution reaction, dramatically limits the electrochemical performance and hampers the further development of AMBs. In this comprehensive review, the key scientific challenges of Al anode/electrolyte interface (AEI) are highlighted. A systematic overview is also provided about the recent progress on the rational interface engineering principles toward a relatively stable AEI. Finally, suggestions and perspectives for future research are offered on the optimization of Al anode and aqueous electrolytes to enable a stable and durable AEI, which may pave the way for developing high-performance AMBs.

Anode-Free Aqueous Aluminum Ion Batteries

Aqueous aluminum ion batteries (AAIBs) possess the advantages of high safety, cost-effectiveness, eco-friendliness and high theoretical capacity. However, the Al2O3 film on the Al anode surface, a natural physical barrier to the plating of hydrated aluminum ions, is a key factor in the decomposition of the aqueous electrolyte and the severe hydrogen precipitation reaction. To circumvent the obnoxious Al anode, a proof-of-concept of an anode-free AAIB is first proposed, in which Al2TiO5, as a cathode pre-aluminum additive (Al source), can replenish Al loss by over cycling. The Al-Cu alloy layer, formed by plating Al on the Cu foil surface during the charge process, possesses a reversible electrochemical property and is paired with a polyaniline (cathode) to stimulate the battery to exhibit high initial discharge capacity (175 mAh g-1), high power density (≈410 Wh L-1) and ultra-long cycle life (4000 cycles) with the capacity retention of ≈60% after 1000 cycles. This work will act as a primer to ignite the enormous prospective researches on the anode-free aqueous Al ion batteries.

General Fabrication of Robust Alloyed Metal Anodes for High-Performance Metal Batteries

Revitalizing metal anodes for rechargeable batteries confronts challenges such as dendrite formation, limited cyclicity, and suboptimal energy density. Despite various efforts, a practical fabrication method for dendrite-free metal anodes remains unavailable. Herein, focusing on Li as exemplar, a general strategy is reported to enhance reversibility of the metal anodes by forming alloyed metals, which is achieved by induction heating of 3D substrate, lithiophilic metals, and Li within tens of seconds. It is demonstrated that preferred alloying interactions between substrates and lithiophilic metals created a lithiophilic metal-rich region adjacent to the substrate, serving as ultrastable lithiophilic host to guide dendrite-free deposition, particularly during prolonged high-capacity cycling. Simultaneously, an alloying between lithiophilic metals and Li creates a Li-rich region adjacent to electrolyte that reduces nucleation overpotential and constitutes favorable electrolyte-Li interface. The resultant composite Li anodes paired with high areal loading LiNi0.8Co0.1Mn0.1O2 cathodes achieve superior cycling stability and remarkable energy density above 1200 Wh L-1 (excluding packaging). Furthermore, this approach shows broader applicability to other metal anodes plagued by dendrite-related challenges, such as Na and Zn. Overall, this work paves the way for development of commercially viable metal-based batteries that offer a combination of safety, high energy density, and durability.

High-Entropy Prussian Blue Analogues Enable Lattice Respiration for Ultrastable Aqueous Aluminum-Ion Batteries

Aqueous aluminum ion batteries (AAIBs) hold significant potential for grid-scale energy storage owing to their intrinsic safety, high theoretical capacity, and abundance of aluminum. However, the strong electrostatic interactions and delayed charge compensation between high-charge-density aluminum ions and the fixed lattice in conventional cathodes impede the development of high-performance AAIBs. To address this issue, this work introduces, for the first time, high-entropy Prussian blue analogs (HEPBAs) as cathodes in AAIBs with unique lattice tolerance and efficient multipath electron transfer. Benefiting from the intrinsic long-range disorder and robust lattice strain field, HEPBAs enable the manifestation of the lattice respiration effect and minimize lattice volume changes, thereby achieving one of the best long-term stabilities (91.2% capacity retention after 10 000 cycles at 5.0 A g-1) in AAIBs. Additionally, the interaction between the diverse metal atoms generates a broadened d-band and reduced degeneracy compared with conventional Prussian blue and its analogs (PBAs), which enhances the electron transfer efficiency with one of the best rate performance (79.2 mAh g-1 at 5.0 A g-1) in AAIBs. Furthermore, exceptional element selectivity in HEPBAs with unique cocktail effect can facile tune electrochemical behavior. Overall, the newly developed HEPBAs with a high-entropy effect exhibit promising solutions for advancing AAIBs and multivalent-ion batteries.

Challenges and Strategies of Aluminum Anodes for High-Performance Aluminum-Air Batteries

Aluminum-air battery (AAB) is a promising candidate for next-generation energy storage/conversion systems due to its cost-effectiveness and impressive theoretical energy density of 8100 Wh kg-1, surpassing that of lithium-ion batteries. Nonetheless, the practical applicability of AABs is hampered by the occurrence of serious self-corrosion side reactions and substantial capacity loss, resulting in suboptimal anode utilization. Consequently, improving the anode utilization to facilitate the construction of high-performance AABs have attracted widespread attention. Herein, the fundamentals and strategies to enhance aluminum anode utilization are reviewed from modifications of aluminum anodes and electrolytes. This comprehensive review may provide a scientific tool for the development of novel AABs in the future.

α-MnO2 Cathode with Oxygen Vacancies Accelerated Affinity Electrolyte for Dual-Ion Co-Encapsulated Aqueous Aluminum Ion Batteries

Aluminum batteries (ABs) are identified as one of the most promising candidates for the next generation of large-scale energy storage elements because of their efficient three-electron reaction. Compared to ionic electrolytes, aqueous aluminum-ion batteries (AAIBs) are considered safer, less costly, and more environmentally friendly. However, considerable cycling performance is a key issue limiting the development of AAIBs. Stable, efficient, and electrolyte-friendly cathodes are most desirable for AAIBs. Herein, a rod-shaped defect-rich α-MnO2 is designed as a cathode, which is capable to deliver high performance with stable cycling for 180 cycles at 500 mA g-1 and maintains a discharge specific capacity of ≈100 mAh g-1. In addition, the infiltrability simulation is effectively utilized to corroborate the rapid electrochemical reaction brought about by the defective mechanism. With the formation of oxygen vacancies, the dual embedding of protons and metal ions is activated. This work provides a brand-new design for the development and characterization of cathodes for AAIBs.

Reversible Insertion of [AlCl4 ]- Superhalides in Graphite

Graphite-based dual-ion batteries are with potential higher energy density, making them a unique candidate in energy storage systems. However, anion insertion into graphite in aqueous environment remains a significant challenge. Herein, we report that the reversible insertion of Al-Cl superhalide into expanded graphite (EG) delivers an ultrahigh specific capacity of ~171 mAh g-1 from an aqueous deep eutectic solvent (DES) gel electrolyte of 50 m ChCl+5 m AlCl3 . High-resolution transmission electron microscopy (HRTEM), Raman spectra and X-ray diffraction (XRD) show that the EG generates turbostratic structure during Al-Cl superhalide (de)insertion instead of presenting typical graphite intercalation compounds (GIC), thus attributing to the high capacity during Al-Cl superhalide insertion.

Dual-Salt Mixed Electrolyte for High Performance Aqueous Aluminum Batteries

A dual-salt electrolyte with 5 M Al(OTF)3 and 0.5 M LiOTF is proposed for aqueous aluminum batteries, which can effectively prevent the corrosion caused by the hydrogen evolution reaction. With the addition of LiOTF in the electrolyte, the solvation phenomenon has changed with the coordination mode of Al3+ conversion from an all octahedral structure to a mixed octahedral and tetrahedral structure. This change can reduce the hydrogen bond between water molecules, which will minimize the occurrence of hydrogen evolution reactions. Moreover, the new electrolyte improves the cycle life of the battery. With MnO as the cathode, 2.1 V high charging platform and 1.5 V high discharge platform can be obtained. The electrochemical stability window (ESW) has been improved to 3.8 V. The first cycle capacity is up to 437 mAh g-1, which can be maintained at 103 mAh g-1 after 100 cycles. This work provides solutions for the future development of electrolyte for aqueous aluminum batteries.

Unexpected Energy Applications of Ionic Liquids

Ionic liquids and their various analogues are without doubt the scientific sensation of the last few decades, paving the way to a more sustainable society. Their versatile suite of properties, originating from an almost inconceivably large number of possible cation and anion combinations, allows tuning of the structure to serve a desired purpose. Ionic liquids hence offer a myriad of useful applications from solvents to catalysts, through to lubricants, gas absorbers, and azeotrope breakers. The purpose of this review is to explore the more unexpected of these applications, particularly in the energy space. It guides the reader through the application of ionic liquids and their analogues as i) phase change materials for thermal energy storage, ii) organic ionic plastic crystals, which have been studied as battery electrolytes and in gas separation, iii) key components in the nitrogen reduction reaction for sustainable ammonia generation, iv) as electrolytes in aluminum-ion batteries, and v) in other emerging technologies. It is concluded that there is tremendous scope for further optimizing and tuning of the ionic liquid in its task, subject to sustainability imperatives in line with current global priorities, assisted by artificial intelligence.

Solvation Structure Regulation for Highly Reversible Aqueous Al Metal Batteries

Metallic Al has been deemed an ideal electrode material for aqueous batteries by virtue of its abundance and high theoretical capacity (8056 mAh cm-3). However, the development of aqueous Al metal batteries has been hindered by several side reactions, including water decomposition, Al corrosion, and passivation, which arise from the solvation reaction of Al and H2O in conventional aqueous electrolytes. In this work, we report that water activity in electrolyte can be suppressed by optimizing the Al3+ solvation structure through intercalation of polar pyridine-3-carboxylic acid in an aluminum trifluoromethanesulfonate aqueous environment. Furthermore, the pyridine-3-carboxylic acid molecules are inclined to alter the surface energy of Al, thus suppressing the random deposition of Al. As a result, the Al corrosion in the hybrid electrolyte is restrained, and the long-term electrochemical stability of the electrolyte is tremendously improved. These merits bring remarkable reversibility to aqueous Al batteries using Al-preintercalated MnO2 cathodes, delivering a retaining energy density of >250 Wh kg-1 at 0.2 A g-1 after 600 cycles.

Copper tetrathiovanadate (Cu3VS4): a newly emerging electrode for rechargeable aqueous aluminum-ion batteries

We report the electrochemistry of Al3+ ion storage in copper tetrathiovanadate (Cu3VS4) in an aqueous electrolyte for the first time. It is found that Cu3VS4 could deliver an initial discharge capacity of 111 mA h g-1 at a current rate of 0.5 A g-1 and 77 mA h g-1 up to the 300th cycle at 2 A g-1 along with an excellent rate capability. The better electrochemical performance may be attributed to the high theoretical capacity of sulfur and the superior conductivity of copper which allows facile Al3+ ion diffusion in Cu3VS4. The electrochemical mechanism of Al3+ ion storage is also illustrated.

Engineering High Voltage Aqueous Aluminum-Ion Batteries

The energy transition to renewables necessitates innovative storage solutions beyond the capacities of lithium-ion batteries. Aluminum-ion batteries (AIBs), particularly their aqueous variants (AAIBs), have emerged as potential successors due to their abundant resources, electrochemical advantages, and eco-friendliness. However, they grapple with achieving their theoretical voltage potential, often yielding less than expected. This perspective article provides a comprehensive examination of the voltage challenges faced by AAIBs, attributing gaps to factors such as the aluminum reduction potential, hydrogen evolution reaction, and aluminum's inherent passivation. Through a critical exploration of methodologies, strategies, such as underpotential deposition, alloying, interface enhancements, tailored electrolyte compositions, and advanced cathode design, are proposed. This piece seeks to guide researchers in harnessing the full potential of AAIBs in the global energy storage landscape.

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.

Vanadium Hexacyanoferrate Prussian Blue Analogs for Aqueous Proton Storage: Excellent Electrochemical Properties and Mechanism Insights

The significant attraction toward aqueous proton batteries (APBs) is attributable to their expedited kinetics, elevated safety profile, and economical feasibility. Nevertheless, their practical implement is significantly blocked by the unsatisfactory energy density due to the limited cathode materials. Herein, vanadium hexacyanoferrate Prussian blue analog (VOHCF) is introduced as a potentially favorable cathode material for APBs. The findings demonstrate that this VOHCF electrode exhibits a notable reversible capacity of 102.7 mAh g-1 and exceptional cycling stability, with 95.4% capacity retention over 10 000 cycles at 10 A g-1 . It is noteworthy that this is the detailed instance of VOHCF being proposed as a cathode for APBs. Combining the in situ characterization techniques and theoretical simulations, the origins of excellent proton storage performance are revealed as the multiple redox mechanisms with double active centers of ─C≡N group and V═O bond in VOHCF as well as the robust structure stability. A proton full cell with excellent performance is further achieved by coupling the VOHCF cathode and diquinoxalino[2,3-a:2',3'-c] phenazine (HATN) anode, demonstrating the great potential of VOHCF in practical applications. This work could provide fundamental understanding to the development of feasible cathode materials for proton storage device.

MXene-Integrated Perylene Anode with Ultra-Stable and Fast Ammonium-Ion Storage for Aqueous Micro Batteries

The aqueous micro batteries (AMBs) are expected to be one of the most promising micro energy storage devices for its safe operation and cost-effectiveness. However, the performance of the AMBs is not satisfactory, which is attributed to strong interaction between metal ions and the electrode materials. Here, the first AMBs are developed with NH4 + as charge carrier. More importantly, to solve the low conductivity and the dissolution during the NH4 + intercalation/extraction problem of perylene material represented by perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), the Ti3 C2 Tx MXene with high conductivity and polar surface terminals is introduced as a conductive skeleton (PTCDA/Ti3 C2 Tx MXene). Benefitting from this, the PTCDA/Ti3 C2 Tx MXene electrodes exhibit ultra-high cycle life and rate capability (74.31% after 10 000 galvanostatic chargedischarge (GCD) cycles, and 91.67 mAh g-1 at 15.0 A g-1 , i.e., capacity retention of 45.2% for a 30-fold increase in current density). More significantly, the AMBs with NH4 + as charge carrier and PTCDA/Ti3 C2 Tx MXene anode provide excellent energy density and power density, cycle life, and flexibility. This work will provide strategy for the development of NH4 + storage materials and the design of AMBs.

Oxygen Vacancies Boosted Proton Intercalation Kinetics for Aqueous Aluminum-Manganese Batteries

Aluminum-ion batteries have garnered an extensive amount of attention due to their superior electrochemical performance, low cost, and high safety. To address the limitation of battery performance, exploring new cathode materials and understanding the reaction mechanism for these batteries are of great significance. Among numerous candidates, multiple structures and valence states make manganese-based oxides the best choice for aqueous aluminum-ion batteries (AAIBs). In this work, a new cathode consists of γ-MnO2 with abundant oxygen vacancies. As a result, the electrode shows a high discharge capacity of 481.9 mAh g-1 at 0.2 A g-1 and a sustained reversible capacity of 128.6 mAh g-1 after 200 cycles at 0.4 A g-1. In particular, through density functional theory calculation and experimental comparison, the role of oxygen vacancies in accelerating the reaction kinetics of H+ has been verified. This study provides insights into the application of manganese dioxide materials in aqueous AAIBs.

MXene-Based Mixed Conductor Interphase for Dendrite-Free Flexible Al Organic Battery

Al batteries are promising post-Li battery technologies for large-scale energy storage applications owing to their low cost and high theoretical capacity. However, one of the challenges that hinder their development is the unsatisfactory plating/stripping of the Al metal anode. To circumvent this issue, an ultrathin MXene layer is constructed on the surface of Al by in situ chemical reactions at room temperature. The as-prepared flexible MXene film acts like armor to protect the Al-metal by its high ionic conductivity and high mechanical flexibility. The MXene endow the Al anode with a long cyclic life of more than 5000 h at ultrahigh current density of 50 mA cm-2 for Al//Al batteries and a retention of 100% over 200 cycles for 355 Wh kg-1 PTO//Al batteries. This work provides fresh insights into the formation and regulation of stable electrode-electrolyte interfaces as well as effective strategies for improving Al metal batteries.

Modulating Aluminum Solvation with Ionic Liquids for Improved Aqueous-Based Aluminum-Ion Batteries

Aqueous-based Al-ion batteries are attractive alternatives to Li-ion batteries due to their safety, high volumetric energy density, abundance, and recyclability. Although aluminum-ion batteries are attractive, there are major challenges to overcome, which include understanding the nature of the passive layer of aluminum oxide on the aluminum anode, the narrow electrochemical window of aqueous electrolytes, and lack of suitable cathodes. Here, we report using experiments in conjunction with DFT simulations to clarify the role of ionic liquids (ILs) in altering the Al solvation dynamics, which in turn affects the aluminum electrochemistry and aqueous-based battery performance significantly. DFT calculations showed that the addition of 1-ethyl-3-methylimidazolium trifluoromethylsulfonate (EMIMTfO) changes the aluminum solvation structure in the aqueous (Al(TfO)3) electrolyte to lower coordinated solvation shells, thereby influencing and improving Al deposition/stripping on the Zn/Al alloy anode. Furthermore, the addition of an IL reduces the strain in manganese oxide during intercalation/deintercalation, thereby improving the Zn/Al-MnOx battery performance. By optimizing the electrolyte composition, a battery potential of >1.7 V was achieved for the Zn/Al-MnOx system.

Promoting Homogeneous Zinc-Ion Transfer Through Preferential Ion Coordination Effect in Gel Electrolyte for Stable Zinc Metal Batteries

Aqueous zinc metal batteries (AZMBs) are emerging energy storage systems that are poised to replace conventional lithium-ion batteries owing to their intrinsic safety, facile manufacturing process, economic benefits, and superior ionic conductivity. However, the issues of inferior anode reversibility and dendritic plating during operation remain challenging for the practical use of AZMBs. Herein, a gel electrolyte based on zwitterionic poly(sulfobetaine methacrylate) (poly(SBMA)) dissolved with different concentrations of ZnSO4 is proposed. Two-dimensional correlation spectroscopy based on Raman analysis reveals an enhanced interaction priority between the polar groups in SBMA and the dissolved ions as electrolyte concentration increases, which establishes a robust interaction and renders homogeneous ion distribution. Attributable to the modified coordination, zwitterionic gel polymer electrolyte with 5 mol kg-1 of ZnSO4 (ZGPE-5) facilitates stable zinc deposition and improves anode reversibility. By taking advantage of preferential coordination, a symmetrical cell evaluation employing ZGPE-5 demonstrates a cycle life over 3600 h, where ZGPE-5 also exerts a beneficial effect on the full cell cycling when assembled with Zn0.25 V2 O5 cathode. This study elucidates changes in the internal ion behavior that are dependent on electrolyte concentrations and pave the way for durable AZMBs.

A Comprehensive Evaluation of Battery Technologies for High-Energy Aqueous Batteries

Aqueous batteries have garnered significant attention in recent years as a viable alternative to lithium-ion batteries for energy storage, owing to their inherent safety, cost-effectiveness, and environmental sustainability. This study offers a comprehensive review of recent advancements, persistent challenges, and the prospects of aqueous batteries, with a primary focus on energy density compensation of various battery engineering technologies. Additionally, cutting-edge high-energy aqueous battery designs are emphasized as a reference for future endeavors in the pursuit of high-energy storage solutions. Finally, a dual-compatibility battery configuration perspective aimed at concurrently optimizing cycle stability, redox potential, capacity utilization for both anode and cathode materials, as well as the selection of potential electrode candidates, is proposed with the ultimate goal of achieving cell-level energy densities exceeding 400 Wh kg-1 .

Optimization of an Artificial Solid Electrolyte Interphase Formed on an Aluminum Anode and Its Application in Rechargeable Aqueous Aluminum Batteries

Electrochemical cells that incorporate aluminum (Al) as the active material have become increasingly popular due to the advantages of high energy density, cost-effectiveness, and superior safety features. Despite the progress made by research groups in developing rechargeable Al//MxOy (M = Mn, V, etc.) cells using an aqueous Al trifluoromethanesulfonate-based electrolyte, the reactions occurring at the Al anode are still not fully understood. In this study, we explore the artificial solid electrolyte interphase (ASEI) on the Al anode by soaking it in AlCl3/urea ionic liquid. Surprisingly, our findings reveal that the ASEI actually promotes the corrosion of Al by providing chloride anions rather than facilitating the transport of Al3+ ions during charge/discharge cycles. Importantly, the ASEI significantly enhances the cycling stability and activity of Al cells. The primary reactions occurring at the Al anode during the charge/discharge cycle were determined to be irreversible oxidation and gas evolution. Furthermore, we demonstrate the successful realization of urea-treated Al (UTAl)//AlxMnO2 cells (discharge operating voltage of ∼1.45 V and specific capacity of 280 mAh/g), providing a platform to investigate the underlying mechanisms of these cells further. Overall, our work highlights the importance of ASEI in controlling the corrosion of Al in aqueous electrolytes, emphasizing the need for the further development of electrolytic materials that facilitate the transport of Al3+ ions in rechargeable Al batteries.

A V2O5 cathode for aqueous rechargeable Pb-ion batteries

Aqueous rechargeable metal batteries (AMBs) have attracted great attention and have been regarded as a next-generation promising energy storage system. However, the high-activity metal anodes usually face side reactions, passivation, and hydrogen evolution reactions, which impede the development of high-performance AMBs. Here, we designed and assembled a Pb metal battery based on a highly reversible Pb metal anode and layered V2O5 cathode, which showed good electrochemical performance. This new-type battery will encourage more investigations for high-performance AMBs and open up an innovation pathway for traditional lead-acid batteries.

Redox Electrolytes-Assisting Aqueous Zn-Based Batteries by Pseudocapacitive Multiple Perovskite Fluorides Cathode and Charge Storage Mechanisms

Aqueous Zn-based batteries (AZBs) have attracted intensive attention. However, to explore advanced cathode materials with in-depth elucidation of their charge storage mechanisms, improve energy storage capacity, and construct novel cell systems remain a great challenge. Herein, a new pseudocapacitive multiple perovskite fluorides (ABF3 ) cathode is designed, represented by KMF-(IV, V, and VI; M = NiCoMnZn/-Mg/-MgFe), and constructed Zn//KMF-(IV, V, and VI) AZBs and their flexible devices. Ex situ tests have revealed a typical bulk phase conversion mechanism of KMF-VI electrode for charge storage in alkaline media dominated by redox-active Ni/Co/Mn species, with transformation of ABF3 nanocrystals into amorphous metal oxide/(oxy)hydroxide nanosheets. By employing single or bipolar redox electrolyte strategies of 20 mm [Fe(CN)6 ]3- or/and 10 mm SO3 2- /Cu[(NH3 )4 ]2+ acting on KMF-(IV, V, and VI) cathode and Zn anode, the AZBs show an improved energy storage owing to additional capacity contribution of redox electrolytes. The as-designed Zn//polyvinyl alcohol (PVA)-KOH-K3 [Fe(CN)6 ]//KMF-(IV, V, and VI) redox gel electrolytes-assisting flexible AZBs (RGE-FAZBs) exhibit remarkable performance under different bending angles because of slight dissolution corrosion of zinc anode compared with liquid electrolytes. Overall, the work demonstrates the novel idea of conversion-type multiple ABF3 cathode for redox electrolytes-assisting AZBs (RE-AZBs) and their flexible systems, showing great significance on electrochemical energy storage.

Highly Stable Al Metal Anode Enabled by Surface Chemical Passivation for Long-Life Aqueous Al Metal Batteries

Aqueous aluminum (Al) metal batteries (AMBs) have received much attention due to their high volumetric energy density, low cost, and high safety. However, the practical application of aqueous AMBs is limited by the electrochemical reversibility of the Al anode, which is often deteriorated by corrosion. Herein, we developed a dense passivation layer based on Mn/Ti/Zr compounds on the Al metal anode by a rapid surface passivation strategy. The passivation layer can effectively uniform Al deposition, increase corrosion resistance, and significantly enhance the cycling stability of Al anodes in both symmetric and full cells. Symmetric cells assembled with the treated Al electrodes exhibit stable cycling for over 300 cycles at 0.1 mA cm^-2 and 0.05 mA h cm^-2, and a 600-cycle life is achieved for a prototype full cell. This work provides a versatile remedy for the limited cycle life of Al metal anodes for rechargeable aqueous batteries.

An asymmetric electrolyte to simultaneously meet contradictory requirements of anode and cathode

One of the major obstacles hindering the application of zinc metal batteries is the contradictory demands from the Zn metal anode and cathodes. At the anode side, water induces serious corrosion and dendrite growth, remarkably suppressing the reversibility of Zn plating/stripping. At the cathode side, water is essential because many cathode materials require both H⁺ and Zn²⁺ insertion/extraction to achieve a high capacity and long lifespan. Herein, an asymmetric design of inorganic solid-state electrolyte combined with hydrogel electrolyte is presented to simultaneously meet the as-mentioned contrary requirements. The inorganic solid-state electrolyte is toward the Zn anode to realize a dendrite-free and corrosion-free highly reversible Zn plating/stripping, and the hydrogel electrolyte enables consequent H⁺ and Zn²⁺ insertion/extraction at the cathode side for high performance. Therefore, there is no hydrogen and dendrite growth detected in cells with a super high-areal-capacity up to 10 mAh·cm^-2 (Zn//Zn), ~5.5 mAh·cm^-2 (Zn//MnO₂) and ~7.2 mAh·cm^-2 (Zn//V₂O₅). These Zn//MnO₂ and Zn//V₂O₅ batteries show remarkable cycling stability over 1000 cycles with 92.4% and over 400 cycles with 90.5% initial capacity retained, respectively.

Investigation of reversible metal ion (Li+, Na+, Mg2+, Al3+) insertion in MoTe2 for rechargeable aqueous batteries

In this work, we report the electrochemical reactivity of MoTe₂ for various metal ions with special emphasis on Al³⁺ ion storage in aqueous electrolytes for the first time. A stable discharge capacity of 100 mA h g^-1 over 250 cycles at a current density of 1 Ag^-1 could be obtained for the Al³⁺ ion, whereas inferior storage capacities were shown for other metal ions.

High-Energy Sn-Ni and Sn-Air Aqueous Batteries via Stannite-Ion Electrochemistry

Tin is promising for aqueous batteries (ABs) due to its multiple electrons' reactions, high corrosion resistance, large hydrogen overpotential, and excellent environmental compatibility. However, restricted to the high thermodynamic barrier and the poor electrochemical kinetics, efficient alkaline Sn plating/stripping at facile conditions has not yet been realized. Here, for the first time, we demonstrate a highly reversible stannite-ion electrochemistry and construct a novel paradigm of high-energy Sn-based ABs. Combined spectroscopic characterization, electrochemical evaluation, and theoretical computation reveal the thermodynamic merits with a low reaction energy barrier and feasible H₂O participation in Sn-ion reduction as well as the kinetic merits with fastened surface charge transfer and SnO₂^2- diffusion. The resultant alkaline Sn anode delivers a low potential of -1.07 V vs Hg/HgO, a specific capacity of 450 mA h g^-1, a Coulombic efficiency of near 100%, superb rate capability at 45.5 A g^-1, and excellent cycling durability without dendrite and dead Sn. As a proof of concept, we developed new high-energy Sn-based ABs, including 1.45 V Sn-Ni with 314 W h kg^-1 (58 kW kg^-1 and over 15,000 cycles) and 1.0 V Sn-air with 420 W h kg^-1 (lifespan over 1900 h), on the basis of masses from cathode and anode active materials. The findings prove the feasibility of the alkaline Sn metal anode, and the new suite of high-energy Sn-based ABs may be of immediate benefit toward safe, reliable, and affordable energy storage.

Zinc-Contained Alloy as a Robustly Adhered Interfacial Lattice Locking Layer for Planar and Stable Zinc Electrodeposition

Stable zinc (Zn)/electrolyte interface is critical for developing rechargeable aqueous Zn-metal batteries with long-term stability, which requires the dense and stable Zn electrodeposition. Herein, an interfacial lattice locking (ILL) layer is constructed via the electro-codeposition of Zn and Cu onto the Zn electrodes. The ILL layer shows a low lattice misfit (δ = 0.036) with Zn(002) plane and selectively locks the lattice orientation of Zn deposits, enabling the epitaxial growth of Zn deposits layer by layer. Benefiting from the unique orientation-guiding and robustly adhered properties, the ILL layer enables the symmetric Zn||Zn cells to achieve an ultralong life span of >6000 h at 1 mA cm^-2 and 1 mAh cm^-2 , a low overpotential (65 mV) at 10 mAh cm^-2 , and a stable Zn plating/stripping for >90 h at an ultrahigh Zn depth of discharge (≈85%). Even with a limited Zn supply and a high current density (8.58 mA cm^-2 ), the ILL@Zn||Ni-doped MnO₂ cells can still survive for >2300 cycles.

A Covalent Organic Framework as a Long-life and High-Rate Anode Suitable for Both Aqueous Acidic and Alkaline Batteries

Aqueous rechargeable batteries are prospective candidates for large-scale grid energy storage. However, traditional anode materials applied lack acid-alkali co-tolerance. Herein, we report a covalent organic framework containing pyrazine (C=N) and phenylimino (-NH-) groups (HPP-COF) as a long-cycle and high-rate anode for both acidic and alkaline batteries. The HPP-COF's robust covalent linkage and the hydrogen bond network between -NH- and water molecules collectively improve the acid-alkaline co-tolerance. More importantly, the hydrogen bond network promotes the rapid transport of H⁺ /OH^- by the Grotthuss mechanism. As a result, the HPP-COF delivers a superior capacity and cycle stability (66.6 mAh g^-1 @ 30 A g^-1 , over 40000 cycles in 1 M H₂ SO₄ electrolyte; 91.7 mAh g^-1 @ 100 A g^-1 , over 30000 cycles @ 30 A g^-1 in 1 M NaOH electrolyte). The work opens a new direction for the structural design and application of COF materials in acidic and alkaline batteries.

Reversible, Dendrite-Free, High-Capacity Aluminum Metal Anode Enabled by Aluminophilic Interface Layer

Aluminum (Al) metal is an attractive anode material for next-generation rechargeable batteries, because of its low cost and high capacities. However, it brings some fundamental issues such as dendrites, low Coulombic efficiency (CE), and low utilization. Here, we propose a strategy for constructing an ultrathin aluminophilic interface layer (AIL) to regulate the Al nucleation and growth behaviors, which enables highly reversible and dendrite-free Al plating/stripping under high areal capacity. Metallic Al can maintain stable plating/stripping on the Pt-AIL@Ti for over 2000 h at 10 mAh cm^-2 with an average CE of 99.9%. The Pt-AIL also enables reversible Al plating/stripping at a record high areal capacity of 50 mAh cm^-2, which is 1-2 orders of magnitude higher than the previous studies. This work provides a valuable direction for further construction of high-performance rechargeable Al metal batteries.

A Multifunctional Interphase Layer Enabling Superior Sodium-Metal Batteries under Ambient Temperature and -40 °C

The sodium (Na)-metal anode with high theoretical capacity and low cost is promising for construction of high-energy-density metal batteries. However, the unsatisfactory interface between Na and the liquid electrolyte induces tardy ion transfer kinetics and dendritic Na growth, especially at ultralow temperature (-40 °C). Herein, an artificial heterogeneous interphase consisting of disodium selenide (Na₂ Se) and metal vanadium (V) is produced on the surface of Na (Na@Na₂ Se/V) via an in situ spontaneous chemical reaction. Such interphase layer possesses high sodiophilicity, excellent ionic conductivity, and high Young's modulus, which can promote Na-ion adsorption and transport, realizing homogenous Na deposition without dendrites. The symmetric Na@Na₂ Se/V cell exhibits outstanding cycling life span of over 1790 h (0.5 mA cm^-2 /1 mAh cm^-2 ) in carbonate-based electrolyte. More remarkably, ab initio molecular dynamics simulations reveal that the artificial Na₂ Se/V hybrid interphase can accelerate the desolvation of solvated Na⁺ at -40 °C. The Na@Na₂ Se/V electrode thus exhibits exceptional electrochemical performance in symmetric cell (over 1500 h at 0.5 mA cm^-2 /0.5 mAh cm^-2 ) and full cell (over 700 cycles at 0.5 C) at -40 °C. This work provides an avenue to design artificial heterogeneous interphase layers for superior high-energy-density metal batteries at ambient and ultralow temperatures.

Tungsten-oxygen bond pre-introduced VO2(B) nanoribbons enable fast and stable zinc ion storage ability

The tunnel structure of the bronze phase vanadium dioxide (VO2(B)) can be used as the zinc ion storage active sites. However, the intense charge repulsion of divalent Zn2+ causes a sluggish reaction kinetics in the tunnel VO2(B). Here, a tungsten-oxygen bond pre-introduced (TOBI) approach is proposed to modulate the tunnel structure of VO2(B). The VO2(B) cathodes with TOBI of 0.5 at% to 3.0 at% have been controllably synthesized by a simple hydrothermal method. The results from structural analysis uncover that the pre-introduced W6+ replaces the V4+ in VO2(B) to form WO6 octahedra. Benefiting from the rapid diffusion kinetics, enhanced structural stability and improved conductivity enabled by the TOBI, the optimal VO2(B) nanoribbons with 1.5 at% shows a high reversible capacity of 265 mAh g-1, a high rate-performance of up-to 10 A g-1 and a long cycling stability of 2000 cycles. Moreover, a pseudo-capacitive dominated Zn2+ intercalation/de-intercalation behavior is solidly determined by the electrochemical kinetics testing and structural characterizations. This TOBI method is referential for developing other multivalent ion battery cathodes with outstanding performances.

Aqueous Rechargeable Zn/ZnO Battery Based on Deposition/Dissolution Chemistry

Recently, a novel electrochemical regulation associated with a deposition/dissolution reaction on an electrode surface has been proven to show superiority in large-scale energy storage systems (ESSs). Hence, in the search for high-performance electrodes showcasing these novel regulations, we utilized a low-cost ZnO microsphere electrode to construct aqueous rechargeable batteries (ARBs) that supplied a harvestable and storable charge through electrochemical deposition/dissolution via a reversible manganese oxidation reaction (MOR)/manganese reduction reaction (MRR), respectively, induced by the inherent formation/dissolution of zinc basic sulfate in a mild aqueous electrolyte solution containing 2 M ZnSO₄ and 0.2 M MnSO₄.

High Performance and Long-cycle Life Rechargeable Aluminum Ion Battery: Recent Progress, Perspectives and Challenges

The rising energy crisis and environmental concerns caused by fossil fuels have accelerated the deployment of renewable and sustainable energy sources and storage systems. As a result of immense progress in the field, cost-effective, high-performance, and long-life rechargeable batteries are imperative to meet the current and future demands for sustainable energy sources. Currently, lithium-ion batteries are widely used, but limited lithium (Li) resources have caused price spikes, threatening progress toward cleaner energy sources. Therefore, post-Li, batteries that utilize highly abundant materials leading to cost-effective energy storage solutions while offering desirable performance characteristics are urgently needed. Aluminum-ion battery (AIB) is an attractive concept that uses highly abundant aluminum while offering a high theoretical gravimetric and volumetric capacity of 2980 mAh g^-1 and 8046 mAh cm^-3 , respectively. As a result, intensified efforts have been made in recent years to utilize numerous electrolytes, anodes, and cathode materials to improve the electrochemical performance of AIBs, and potentially create high-performance, low-cost, and safe energy storage devices. Herein, recent progress in the electrolyte, anode, and cathode active materials and their utilization in AIBs and their related characteristics are summarized. Finally, the main challenges facing AIBs along with future directions are highlighted.

Bimetallic Rechargeable Al/Zn Hybrid Aqueous Batteries Based on Al-Zn Alloys with Composite Electrolytes

Aluminum is abundant and exhibits a high theoretical capacity and volumetric energy density. Additionally, the high safety of aqueous aluminum-ion batteries makes them strong candidates for large-scale energystorage systems. However, the frequent collapse of the cathode material and passive oxide film results in the difficult development of aqueous aluminum-ion batteries. This work provides a novel battery system, namely, Al-Zn/Al(OTF)₃ +HOTF+Zn(OTF)₂ /Al_x Zn_y MnO₂ ·nH₂ O, with a mixed electrolyte. The cathode applies MnO topology transformation to ensure that the cathode forms Al_x MnO₂ ·nH₂ O. Topology transformation alters the structure of the cathode material so that Zn²⁺ can be intercalated into the Al_x MnO₂ ·nH₂ O spinel structure to provide support for the material structure. Regarding the anode, Zn²⁺ in the electrolyte is deposited onto Al of the anode to produce a regional Al-Zn alloy. Zn²⁺ is reduced to Zn metal during discharging, which adds a platform for secondary discharge beneficial for battery capacity enhancement. This system can provide a 1.6 V discharge platform, while the first cycle discharge can reach 554 mAh g^-1 , thereby maintaining a high capacity of 313 mAh g^-1 after 100 cycles. This study provides a new idea for the further development of aqueous aluminum-ion batteries (AAIBs).

Rechargeable Aqueous Aluminum-Ion Battery: Progress and Outlook

The high cost and scarcity of lithium resources have prompted researchers to seek alternatives to lithium-ion batteries. Among emerging "Beyond Lithium" batteries, rechargeable aluminum-ion batteries (AIBs) are yet another attractive electrochemical storage device due to their high specific capacity and the abundance of aluminum. Although the current electrochemical performance of nonaqueous AIBs is better than aqueous AIBs (AAIBs), AAIBs have recently gained attention due to their low cost and enhanced safety. Extensive efforts are devoted to developing AAIBs in the last few years. Yet, it is still challenging to achieve stable electrodes with good electrochemical performance and electrolytes without side reactions. This review summarizes the recent progress in the exploration of anode and cathode materials and the selection of electrolytes of AAIBs. Lastly, the main challenges and future research outlook of high-performance AAIBs are also presented.

Arrayed Heterostructures of MoS2 Nanosheets Anchored TiN Nanowires as Efficient Pseudocapacitive Anodes for Fiber-Shaped Ammonium-Ion Asymmetric Supercapacitors

Nonmetallic ammonium ions that feature high safety, low molar mass, and small hydrated radius properties have shown great advantages in wearable aqueous supercapacitors. The construction of high-energy-density flexible ammonium-ion asymmetric supercapacitors (AASCs) is promising but still challenging due to the lack of high-capacitance pseudocapacitive anodes. Herein, freestanding core-shell heterostructures supported on carbon nanotube fibers were designed by anchoring MoS₂ nanosheets on nanowires (MoS₂@TiN/CNTF) as anodes for AASCs. With contributions of abundant active sites and conspicuous synergistic effects of multiple components for arrayed heterostructure engineering, the developed MoS₂@TiN/CNTF anodes exhibit a specific capacitance of 1102.5 mF cm^-2 at 2 mA cm^-2. Theoretical calculations confirm the dramatic enhancement of the binding strength of ammonium ions on the MoS₂ shell layer at the heterostructure, where a built-in electric field exists to accelerate the charge transfer. By utilizing a MnO₂/CNTF cathode and NH₄Cl/poly(vinyl alcohol) (PVA) as a gel electrolyte, quasi-solid-state fiber-shaped AASCs were successfully constructed, achieving a specific capacitance of 351.2 mF cm^-2 and an energy density of 195.1 μWh cm^-2, outperforming most recently reported fiber-shaped supercapacitors. This work provides a promising strategy to rationally design heterostructure engineering of MoS₂@TiN nanoarrays toward advanced anodes for application in next-generation AASCs.

Simply Prepared Magnesium Vanadium Oxides as Cathode Materials for Rechargeable Aqueous Magnesium Ion Batteries

Vanadium-oxide-based materials exist with various vanadium oxidation states having rich chemistry and ability to form layered structures. These properties make them suitable for different applications, including energy conversion and storage. Magnesium vanadium oxide materials obtained using simple preparation route were studied as potential cathodes for rechargeable aqueous magnesium ion batteries. Structural characterization of the synthesized materials was performed using XRD and vibrational spectroscopy techniques (FTIR and Raman spectroscopy). Electrochemical behavior of the materials, observed by cyclic voltammetry, was further explained by BVS calculations. Sluggish Mg²⁺ ion kinetics in MgV₂O₆ was shown as a result of poor electronic and ionic wiring. Complex redox behavior of the studied materials is dependent on phase composition and metal ion inserted/deinserted into/from the material. Among the studied magnesium vanadium oxides, the multiphase oxide systems exhibited better Mg²⁺ insertion/deinsertion performances than the single-phase ones. Carbon addition was found to be an effective dual strategy for enhancing the charge storage behavior of MgV₂O₆.

Vanadium Tetrasulfide for Next-Generation Rechargeable Batteries: Advances and Challenges

Alkali metal-ion batteries (SIBs and PIBs) and multivalent metal-ion batteries (ZIBs, MIBs, and AIBs), among the next-generation rechargeable batteries, are deemed appealing alternatives to lithium-ion batteries (LIBs) because of their cost competitiveness. Improving the electrochemical properties of electrode materials can greatly accelerate the pace of development in battery systems to cover the increasing demands of realistic applications. Vanadium tetrasulfide (VS₄ ) is known as a prospective electrode material due to its unique one-dimensional atomic chain structure with a large chain spacing, weak interactions between adjacent chains, and high sulfur content. This review summarizes the synthetic strategies and recent advances of VS₄ as cathodes/anodes for rechargeable batteries. Meanwhile, we describe the structural characteristics and electrochemical properties of VS₄ . And we describe in detail its specific applications in batteries such as SIBs, PIBs, ZIBs, MIBs, and AIBs as well as modification strategies. Finally, the opportunities and challenges of VS₄ in the domain of energy research are described.

Reversible Al Metal Anodes Enabled by Amorphization for Aqueous Aluminum Batteries

Aqueous aluminum metal batteries (AMBs) are regarded as one of the most sustainable energy storage systems among post-lithium-ion candidates, which is attributable to their highest theoretical volumetric capacity, inherent safe operation, and low cost. Yet, the development of aqueous AMBs is plagued by the incapable aluminum plating in an aqueous solution and severe parasitic reactions, which results in the limited discharge voltage, thus making the development of aqueous AMBs unsuccessful so far. Here, we demonstrate that amorphization is an effective strategy to tackle these critical issues of a metallic Al anode by shifting the reduction potential for Al deposition. The amorphous aluminum (a-Al) interfacial layer is triggered by an in situ lithium-ion alloying/dealloying process on a metallic Al substrate with low strength. Unveiled by experimental and theoretical investigations, the amorphous structure greatly lowers the Al nucleation energy barrier, which forces the Al deposition competitive to the electron-stealing hydrogen evolution reaction (HER). Simultaneously, the inhibited HER mitigates the passivation, promoting interfacial ion transfer kinetics and enabling steady aluminum plating/stripping for 800 h in the symmetric cell. The resultant multiple full cells using Al@a-Al anodes deliver approximately a 0.6 V increase in the discharge voltage plateau compared to that of bare Al-based cells, which far outperform all reported aqueous AMBs. In both symmetric cells and full cells, the excellent electrochemical performances are achieved in a noncorrosive, low-cost, and fluorine-free Al₂(SO₄)₃ electrolyte, which is ecofriendly and can be easily adapted for sustainable large-scale applications. This work brings an intriguing picture of the design of metallic anodes for reversible and high-voltage AMBs.

Optimization of Electrolytes for High-Performance Aqueous Aluminum-Ion Batteries

Aqueous rechargeable batteries based on aluminum chemistry have become the focus of immense research interest owing to their earth abundance, low cost, and the higher theoretical volumetric energy density of this element compared to lithium-ion batteries. Efforts to harness this huge potential have been hindered by the narrow potential window of water and by passivating effects of the high-electrical band-gap aluminum oxide film. Herein, we report a high-performing aqueous aluminum-ion battery (AIB), which is constructed using a Zn-supported Al alloy, an aluminum bis(trifluoromethanesulfonyl)imide (Al[TFSI]₃) electrolyte, and a MnO₂ cathode. The use of Al[TFSI]₃ significantly extends the voltage window of the electrolyte and enables the cell to access Al³⁺/Al electrochemistry, while the use of Zn-Al alloy mitigates the issue of surface passivation. The Zn-Al alloy, which is produced by in situ electrochemical deposition, obtained from Al[TFSI]₃ showed excellent long-term reversibility for Al electrochemistry and displays the highest performance in AIB when compared to the response obtained in Al₂(SO₄)₃ or aluminum trifluoromethanesulfonate electrolyte. AIB cells constructed using the Zn-Al|Al[TFSI]₃|MnO₂ combination achieved a record discharge voltage plateau of 1.75 V and a specific capacity of 450 mAh g^-1 without significant capacity fade after 400 cycles. These findings will promote the development of energy-dense aqueous AIBs.

H2 -Inhibited Organic Anodes for Fast and Long-Life Aqueous Aluminum Ion Batteries with a 3.5-Month Calendar Life

Aqueous aluminum ion batteries are rarely constructed due to the unworkable Al metal and the preferential H₂ evolution. Herein, organic anode with H₂ -inhibition is optimized through tuning the polymerization degree and displays a high-rate and reversible storage of Al ions based on an enolation between Al ions and the carbonyl double bonds on the conjugated structures. The superiority of the optimal sample is researched, which is attributed to the raised state of lowest unoccupied molecule orbital (LUMO) with the doner N-N bridge and relatively small steric hindrance of the dimmer. When paired with active carbon, a high cycling life of 5000 cycles with a retention of 99.2% is obtained. A full battery constructed by this dimer and δ-MnO₂ cathode delivers an average voltage of 1.0 V, high capacity of 263.8 mAh g^-1 based on the mass of δ-MnO₂ , and high-capacity retention of 88.8% after cycling for 300 cycles. More importantly, with a fully eliminated corrosion and passivation in AlCl₃ and Al₂ (SO₄ )₃ electrolytes, a long calendar stability of 104 days is achieved.

Rational Design Strategy of Novel Energy Storage Systems: Toward High-Performance Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMBs) are promising candidates to replace currently commercialized lithium-ion batteries (LIBs) in large-scale energy storage applications owing to their merits of abundant resources, low cost, high theoretical volumetric capacity, etc. However, the development of RMBs is still facing great challenges including the incompatibility of the electrolyte and the lack of suitable cathode materials with high reversible capacity and fast kinetics of Mg²⁺ . While tremendous efforts have been made to explore compatible electrolytes and appropriate electrode materials, the rational design of unconventional Mg-based battery systems is another effective strategy for achieving high electrochemical performance. This review specifically discusses the recent research progress of various Mg-based battery systems. First, the optimization of electrolyte and electrode materials for conventional RMBs is briefly discussed. Furthermore, various Mg-based battery systems, including Mg-chalcogen (S, Se, Te) batteries, Mg-halogen (Br₂ , I₂ ) batteries, hybrid-ion batteries, and Mg-based dual-ion batteries are systematically summarized. This review aims to provide a comprehensive understanding of different Mg-based battery systems, which can inspire latecomers to explore new strategies for the development of high-performance and practically available RMBs.