Search

Lithium–sulfur batteries (LSBs) have emerged as promising power sources for high‐performance devices such as electric vehicles. However, the poor energy density of LSBs owing to polysulfide shuttling and passivation has limited their further market penetration. To mitigate this challenge, two‐dimensional (2D) siloxene (2DSi), a Si‐based analog of graphene, is utilized as an additive for sulfur cathodes. The 2DSi is fabricated on a large scale by simple solvent extraction of calcium disilicide to form a thin‐layered structure of Si planes functionalized with vertically aligned hydroxyl groups in the 2DSi. The stoichiometric reaction of 2DSi with polysulfides generates a thiosulfate redox mediator, secures the intercalation pathway, and reveals Lewis acidic sites within the siloxene galleries. The 2DSi utilizes the corresponding in‐situ‐formed electrocatalyst, the 2D confinement effect of the layered structure, and the surface affinity based on Lewis acid–base interaction to improve the energy density of 2DSi‐based LSB cells. Combined with the commercial carbon‐based current collector, 2DSi‐based LSB cells achieve a volumetric energy density of 612 Wh Lcell−1 at 1 mA cm−2 with minor degradation of 0.17% per cycle, which rivals those of state‐of‐the‐art LSBs. This study presents a method for the industrial production of high‐energy‐dense LSBs.

This review discusses how halide ion species have been used as charge carriers in both anion rocking‐chair and dual‐ion battery (DIB) systems. The anion rocking‐chair batteries based on fluoride and chloride have emerged over the past decade and are garnering increased research interest due to their large theoretical energy density values and the natural abundance of halide‐containing materials. Moreover, DIBs that use halide species as their anionic charge carrier are seen as one of the promising next‐generation battery technologies due to their low cost and high working potentials. Although numerous polyatomic anions have been studied as charge carriers, the use of single halide ions (i.e., F− and Cl−) and metal‐based superhalides (e.g., [MgCl3]−) as anionic charge carriers in DIBs has been considerably less explored. Herein, we provide an overview of some of the key advances and recent progress that has been made with regard to halide ion charge carriers in electrochemical energy storage. We offer our perspectives on the current state of the field and provide a roadmap in hopes that it helps researchers toward making new advances in these promising and emerging areas.

Most reported cathodes of nonaqueous dual-ion batteries (DIBs) host anions via insertion reactions. It is necessary to explore new cathode chemistry to increase the battery energy density. To date, transition metals have yet to be investigated for nonaqueous DIBs, albeit they may offer high capacity in anodic conversion reactions. Here, we report that bulk copper powder exhibits a high reversible capacity of 762 mAh g

Fluoride is a promising charge carrier for batteries due to its high charge/mass ratio and small radius. Here, we report commercial copper powder exhibits a reversible capacity of up to 222 mA h g

A great challenge for all aqueous batteries, including Zn‐metal batteries, is the parasitic hydrogen evolution reaction on the low‐potential anode. Herein, we report the formula of a highly concentrated aqueous electrolyte that mitigates hydrogen evolution by transforming water molecules more inert. The electrolyte comprises primarily ZnCl2 and LiCl as an additive, both of which are inexpensive salts. The O–H covalent bonds in water get strengthened in a chemical environment that has fewer hydrogen bonding interactions and a greater number of Zn–Cl superhalides, as suggested by integrated characterization and simulation. As a result, the average Coulombic efficiency of zinc‐metal anode is raised to an unprecedented >99.7% at 1 mA cm−2. In the new electrolyte, the plating/stripping processes leave the zinc‐metal anode dendrite‐free, and the zinc‐metal anode delivers stable plating/stripping cycles for 4000 hours with an areal capacity of 4 mAh cm−2 at 2 mA cm−2. Furthermore, the high Coulombic efficiency of zinc‐metal anode in the ZnCl2‐LiCl mixture electrolyte is demonstrated in full cells with a limited anode. The V2O5·H2O||Zn full cell with an N/P mass ratio of 1.2 delivers a stable life of more than 2500 cycles, and the LiMn2O4||Zn hybrid cell with an N/P mass ratio of 0.6 exhibits 1500 cycles in its stable life.

Dual-ion batteries that use anions and cations as charge carriers represent a promising energy-storage technology. However, an uncharted area is to explore transition metals as electrodes to host carbonate in conversion reactions. Here we report the reversible conversion reaction from copper to Cu

Aqueous electrolytes are the leading candidate to meet the surging demand for safe and low-cost storage batteries. Aqueous electrolytes facilitate more sustainable battery technologies due to the attributes of being nonflammable, environmentally benign, and cost effective. Yet, water's narrow electrochemical stability window remains the primary bottleneck for the development of high-energy aqueous batteries with long cycle life and infallible safety. Water's electrolysis leads to either hydrogen evolution reaction (HER) or oxygen evolution reaction (OER), which causes a series of dire consequences, including poor Coulombic efficiency, short device longevity, and safety issues. These are often showstoppers of a new aqueous battery technology besides the low energy density. Prolific progress has been made in the understanding of HER and OER from both catalysis and battery fields. Unfortunately, a systematic review on these advances from a battery chemistry standpoint is lacking. This review provides in-depth discussions on the mechanisms of water electrolysis on electrodes, where we summarize the critical influencing factors applicable for a broad spectrum of aqueous battery systems. Recent progress and existing challenges on suppressing water electrolysis are discussed, and our perspectives on the future development of this field are provided.

Aqueous batteries have engendered increasing attention as promising solutions for stationary energy storage due to their potentially low cost and innate safety. In various aqueous battery systems, Prussian blue analogues (PBAs) represent a class of promising electrode materials with fascinating electrochemical performance, owing to their large open frameworks, abundant ion insertion sites, and facile preparation. To date, PBAs have shown substantial progress towards storage of alkali metal ions (Li+, Na+, and K+), H+, and NH4+ in aqueous electrolytes, which, however, has yet not been specifically summarized. This review selects some representative research to introduce the progress of PBAs in these battery systems and aims to discuss the crucial role of ionic charge carrier in affecting the overall electrode performance. Besides, some critical knowledge gaps and challenges of PBA materials have been pointed out for future development. This review introduces the recent progress of Prussian blue analogues for aqueous monovalent ion batteries, including metal ions of Li+, Na+, K+, and non-metal ions of H+ and NH4+.

Metal-organic frameworks (MOFs) constructed with mixed ligands have shown great promise in the generation of materials with improved sorption, optical, and electronic properties. With an experimental, spectroscopic, and computational approach, herein, we investigated how the incorporation of different functionalized ligands within the structure of MIL-125-NH2 affects its performance in photocatalytic water reduction. We found that multiligand incorporation within the MOF structure has an impact on the light absorption spectrum and the electronic structure. These combined modifications improve the photocatalytic performance of MIL-125-NH2, thereby increasing the rate of hydrogen evolution reaction. Of the four nanoparticle/MOF photocatalytic systems tested, we showed that the Pt/MIL-125-NH2/(OH)2 system (Pt nanoparticle plus MIL-125-NH2 with amino and dihydroxyl functionalized ligands) outperforms its counterpart Pt/MIL-125-NH2 system, attributed to the enhanced p-π conjugation between the lone pairs of O atoms and their aromatic ligands resulting in a red-shifted absorption spectrum and greater spatial distribution of electron density.

Anion storage in cathode of dual-ion batteries provides leeway for new battery chemistries. For high energy density and better safety, it is desirable but challenging to reversibly intercalate chlo...

Although the utilization of mildly acidic electrolyte can enhance the stability and reversibility of Zn anode, it is still challenging to achieve long cycling life for aqueous Zn batteries at low currents, due to the structural instability of cathode materials during the charge/discharge processes. Herein, we report a series of polypyrenes with different linking patterns and electronic structures as Cl−-hosting organic cathodes for aqueous Zn dual-ion batteries (AZDIBs). The comparative study demonstrates that the electronic structures are pivotal to the redox activity of the polypyrenes, which can be tuned by altering the linking patterns on the pyrene unit. Owing to the high surface area, the highly delocalized HOMO distribution, the high HOMO level and the narrow band gap, the polymer CLPy with 1,3,6,8-linking pattern delivers a much higher capacity of 180 mA h g−1 than the two linear counterparts (24 mA h g−1 for LPy-1 and 44 mA h g−1 for LPy-2). Impressively, CLPy exhibits ultra-stable cyclabilities with the capacity retentions of 97.4% after 800 cycles at 50 mA g−1 and 96.4% after 38 000 cycles at 3 A g−1. CLPy also shows a low self-discharge rate with around 90% capacity retention after resting for 28 days. The excellent electrochemical performance demonstrates that CLPy can be a promising cathode material for high-performance AZDIBs.

Practical lithium-sulfur batteries stipulate the use of a lean-electrolyte and a high Coulombic efficiency of the lithium metal anode. Herein, we employ 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether as a co-solvent in the electrolyte of Li-S batteries to meet the demands. The co-solvent fosters the formation of a LiF-rich solid electrolyte interphase on lithium metal anode, as revealed by Ab initio molecular dynamics and Femtosecond Stimulated Raman spectroscopy. The co-solvent results in an average Coulombic efficiency of 99.4% for lithium plating/stripping cycles. Full cells with a capacity ratio of 2 between lithium anode and the S@PAN cathode (3 mgs cm−2) exhibited a stable cycle life over 100 cycles at an electrolyte/sulfur ratio of 2 µL mg−1, validating the high Coulombic efficiency of the lithium anode and demonstrating the compatibility of the electrolyte with both electrodes. To enhance the energy density, we prepared a hybrid cathode composed of 45 wt.% VS2 mixed with ZnS-coated Li2S@graphene as the cathode. Based on the mass of both electrodes and the electrolyte, the full cell delivers an energy density of 483 Wh kg−1, which demonstrates viable Li-S batteries with the lean-electrolyte.

Proton conduction underlies many important electrochemical technologies. We report a series of new proton electrolytes: acid-in-clay electrolyte termed AiCE, prepared by integrating fast proton carriers in a natural phyllosilicate clay network, that can be made into thin-film (tens of microns) fluid-impervious membranes. The chosen example systems (sepiolite-phosphoric acid) rank top among the solid proton conductors in consideration of proton conductivities (15 mS cm−1 at 25 °C, 0.023 mS cm−1 at −82 °C), the stability window (3.35 V), and reduced chemical activity. A solid-state proton battery was assembled using AiCE as the electrolyte to demonstrate the performance of these electrolytes. Benefitting from the wider electrochemical stability window, reduced corrosivity, and excellent ionic selectivity of AiCE, the two main problems (gasification and cyclability) of proton batteries have been successfully solved. This work also draws the attention of elemental cross-over in proton batteries and illustrates a simple “acid-in-clay” approach to synthesize a series of solid proton electrolytes with a superfast proton permeability, outstanding selectivity, and improved stability for many potential applications associated with protons.

Charge carriers are fundamental components of batteries that determine battery chemistry and performance. Non-metallic charge carriers provide an alternative to metallic charge carriers in aqueous batteries, enabling fast kinetics, long cyclic lifetime and low manufacturing costs. Non-metallic charge carriers not only can be inserted into the electrode framework, where they establish covalent–ionic bonds, but can also serve as reversible redox centres for charge transfer, resulting in superior performance compared with metallic charge carrier-based devices. In this Review, we discuss cationic and anionic non-metallic charge carriers, their physicochemical properties, charge storage mechanisms and electrode interactions. We examine battery configurations of non-metallic charge carrier-based devices and analyse battery performance based on costs, capacity, working potential, rate capability and cycling stability. Finally, we highlight design strategies for aqueous batteries based on non-metallic charge carriers and future applications. This Review discusses non-metallic charge carriers for aqueous batteries, investigating fundamental mechanisms of charge storage and electrode interactions, as well as battery design and performance.

A non-aqueous proton electrolyte is devised by dissolving H3 PO4 into acetonitrile. The electrolyte exhibits unique vibrational signatures from stimulated Raman spectroscopy. Such an electrolyte exhibits unique characteristics compared to aqueous acidic electrolytes: 1) higher (de)protonation potential for a lower desolvation energy of protons, 2) better cycling stability by dissolution suppression, and 3) higher Coulombic efficiency owing to the lack of oxygen evolution reaction. Two non-aqueous proton full cells exhibit better cycling stability, higher Coulombic efficiency, and less self-discharge compared to the aqueous counterpart.

Oxidative anion insertion into graphite in an aqueous environment represents a significant challenge in the construction of aqueous dual-ion batteries. In dilute aqueous electrolytes, the oxygen evolution reaction (OER) dominates the anodic current before anions can be inserted into the graphite gallery. Herein, we report that the reversible insertion of Mg-Cl superhalides in graphite delivers a record-high reversible capacity of 150 mAh g-1 from an aqueous deep eutectic solvent comprising magnesium chloride and choline chloride. The insertion of Mg-Cl superhalides in graphite does not form staged graphite intercalation compounds; instead, the insertion of Mg-Cl superhalides makes the graphite partially turbostratic.

Magnesium oxide was found to have high‐phosphate‐affinity as an effective component to enhance the phosphate removal ability of common adsorbent materials. However, the currently prepared MgO‐based hybrid adsorbents by conventional methods still suffer from the limited low loading of MgO and inferior removal performances, much far away from practical application. In this study, an ingenious carbon coated MgO nanocomposite is designed by directly burning magnesium in CO2, a well‐known textbook reaction. X‐ray diffraction analysis, scanning electron microscope and aberration‐corrected high‐resolution transmission electron microscope demonstrate the sample is well prepared. Consequently, the high content of nanosized MgO combined with defect‐rich carbon layer brings unprecedented phosphate removal capacity of 1135.0 mg/g, removal rate of 99% and benign compatibility with coexisting anions and solution pH. Furthermore, the removal mechanism is also investigated in detail by characterizing the sample before and after adsorption.

Irreversible reductive insertion of Zn2+ transforms Mn3O4 such that the resulting Zn0.2Mn3O4 exhibits highly reversible storage properties of chloride ions, thus rendering Zn0.2Mn3O4 an excellent cathode of aqueous dual‐ion batteries. With Zn2+ trapped, Zn0.2Mn3O4 delivers the chloride‐storage capacity over 200 mAh/g at an average potential of 1.6 V vs Zn2+/Zn by reversibly forming a new ionic compound equivalent to Zn0.2Mn3O4Cl1.7. Electrochemical quartz crystal microbalance results suggest chloride as the primary charge carrier in the reversible oxidative anion insertion. The Mn3O4 anion‐hosting cathode couples with Zn metal anode in a full‐cell dual‐ion battery, demonstrating stable cycling in practical pouch cells with an energy density of 150 Wh/kg based on the mass of both electrodes.

The inability of current battery technologies to keep up with the performance requirements of industry is pushing forward developments in electrochemistry. Specifically, the battery’s negative electrode, the anode, presents many unique chemical, physical and engineering challenges. Lithium-based battery technologies have dominated the past decade, but concerns about the limited supply of lithium in the Earth’s crust have led researchers to look towards alternative metal-ion technologies. Various alkali metals (such as sodium and potassium) and alkali earth metals (such as magnesium and calcium) have attracted significant research interest. In this Review, we analyse these technologies in a coherent manner, addressing the problems of each type of anode, rather than those of specific types of metal-ion batteries. Covering direct metal plating and stripping, intercalation-based, alloy-based and conversion-reaction-based anode technologies, this analysis will offer the reader a comprehensive understanding of the behaviour of different metal-ion anodes and of what can be learned by transferring knowledge between these different systems. Increasing demand for energy-storage systems will inevitably stress the Earth’s lithium supply; thus, the research focus is shifting towards other alkali and alkali earth metals. This Review compares and connects strategies to enable different multivalent and monovalent metal-ion battery anodes, including metal anodes and intercalation-based, alloy-based and conversion-reaction-based anodes.

Energy storage will witness a leap of understanding of new battery chemistries. Considering the safety that cannot be compromised, new aqueous batteries may surface as the solutions to meet the immense market needs, where the growth of renewables is no longer limited by the lack of storage. Aqueous Zn-metal batteries are intriguing candidates to deliver the desirable properties and exhibit competitive levelized energy cost. However, the fact that most commercial Zn batteries are primary batteries states the difficulty of reversibility for the reactions of electrodes in such batteries. This article will highlight the practical needs that guide the development of storage batteries. The causes of irreversibility for both cathode and zinc metal anode are discussed, and the potential solutions for these challenges are summarized. Zn metal batteries may one day address the storage needs, and there exists a vast potential to further improve the properties of reactions in this battery.

A full cell chemistry of aqueous dual-ion battery (DIB) was reported, comprising the graphite cathode and 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) as the anode. This DIB employed a mixture aqueous electrolyte: 5 m tributylmethylammonium (TBMA) chloride plus 5 m MgCl

Potassium-ion batteries (KIBs) have attracted wide interests for energy storage because of the abundance of the electrode materials involved; however, their electrochemical performances are far behind what can be achieved from lithium-ion batteries (LIBs) or sodium-ion batteries (SIBs). This paper identifies key promising electrode and electrolyte materials for potassium-ion batteries, investigates the coupled electrochemical reactions in the cell, and demonstrates that the compatibility between different materials plays the most important role. K2 Mn[Fe(CN)6 ] cathode can deliver a high capacity of ∼125 mAh g-1 and exceptional cycling stability over 61,000 cycles (∼9 months) if the side reactions from the anode can be prevented. Graphite is a good anode material but is subjected to degradation in traditional carbonate electrolytes. New concentrated electrolytes are developed and evaluated. A stable KIB system is demonstrated by coupling a stable K2 Mn[Fe(CN)6 ] cathode, a pre-potassiated graphite anode with a concentrated electrolyte to achieve a high energy density of ∼260 Wh kg-1 (based on the active mass of cathode and anode) and good cycling of over 1000 cycles. This article is protected by copyright. All rights reserved.

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.

We demonstrate a disposable aqueous primary battery chemistry that comprises environmentally benign materials of the sulfur cathode and Zn anode in a 1 M ZnCl2 aqueous electrolyte. The Zn–S battery shows a high energy density of 1083.3 Wh kg−1 for sulphur with a flat discharge voltage plateau around 0.7 V. When operating at a high mass loading of 8.3 mg cm−2 for sulfur in the cathode, the battery exhibits a very high areal capacity of 11.4 mA h cm−2 and areal energy of 7.7 mW h cm−2.

Iron ion batteries using Fe

Summary As promising alternatives to lithium-ion batteries, rechargeable anion-shuttle batteries (ASBs) with anions as charge carriers stand out because of their low cost, long cyclic lifetime, and/or high energy density. In this review, we provide for the first time, comprehensive insights into the anion shuttling mechanisms of ASBs, including anion-based rocking-chair batteries (ARBs), dual-ion batteries (DIBs), including insertion-type, conversion-type, and conversion-insertion-type, and reverse dual-ion batteries (RDIBs). Thereafter, we review the latest progresses and challenges regarding electrode materials and electrolytes for ASBs. In addition, we summarize the existing dilemmas of ASBs and outline the perspective of ASB technology for future grid storage.

Chemical/electrochemical stability at the interfaces greatly affects the performance of solid-state batteries (SSBs). However, the interfacial behavior in SSBs remains elusive due to the subsurface nature of interfaces and the lack of proper characterization methods. Herein, ultrasonic imaging technology is employed to non-destructively investigate the interfacial stability in solid-state pouch cells. Benefiting from the high sensitivity of ultrasound to the gas/vacuum, in-situ ultrasonic imaging can effectively probe the inner gas release and interfacial degradation in pouch cells during long-term cycling. The safety issue of SSBs is highlighted by the flammable gas release detected in ultrasonic images. And the increased interfacial resistance either from contact loss or passivation layer growth is well distinguished. The gradual oxidation and gassing at the cathode interface are tracked by ultrasonic imaging, which leads to the capacity fading of SSBs. The ultrasonic imaging technology is demonstrated to be a powerful tool to evaluate the interfacial stability in SSBs, which can guide the rational design of interfaces and enhance the performance of SSBs.

Plating battery electrodes typically deliver higher specific capacity values than insertion or conversion electrodes because the ion charge carriers represent the sole electrode active mass, and a host electrode is unnecessary. However, reversible plating electrodes are rare for electronically insulating nonmetals. Now, a highly reversible iodine plating cathode is presented that operates on the redox couples of I2 /[ZnIx (OH2 )4-x ]2-x in a water-in-salt electrolyte. The iodine plating cathode with the theoretical capacity of 211 mAh g-1 plates on carbon fiber paper as the current collector, delivering a large areal capacity of 4 mAh cm-2 . Tunable femtosecond stimulated Raman spectroscopy coupled with DFT calculations elucidate a series of [ZnIx (OH2 )4-x ]2-x superhalide ions serving as iodide vehicles in the electrolyte, which eliminates most free iodide ions, thus preventing the consequent dissolution of the cathode-plated iodine as triiodides.

The elemental sulfur electrode with Cu2+ as the charge carrier gives a four-electron sulfur electrode reaction through the sequential conversion of S↔CuS↔Cu2 S. The Cu-S redox-ion electrode delivers a high specific capacity of 3044 mAh g-1 based on the sulfur mass or 609 mAh g-1 based on the mass of Cu2 S, the completely discharged product, and displays an unprecedently high potential of sulfur/metal sulfide reduction at 0.5 V vs. SHE. The Cu-S electrode also exhibits an extremely low extent of polarization of 0.05 V and an outstanding cycle number of 1200 cycles retaining 72 % of the initial capacity at 12.5 A g-1 . The remarkable utility of this Cu-S cathode is further demonstrated in a hybrid cell that employs an Zn metal anode and an anion-exchange membrane as the separator, which yields an average cell discharge voltage of 1.15 V, the half-cell specific energy of 547 Wh kg-1 based on the mass of the Cu2 S/carbon composite cathode, and stable cycling over 110 cycles.

The interactions between charge carriers and electrode structures represent one of the most important considerations in the search for new energy storage devices. Currently, ionic bonding dominates the battery chemistry. Here we report the reversible insertion of a large molecular dication, methyl viologen, into the crystal structure of an aromatic solid electrode, 3,4,9,10-perylenetetracarboxylic dianhydride. This is the largest insertion charge carrier when non-solvated ever reported for batteries; surprisingly, the kinetic properties of the (de)insertion of methyl viologen are excellent with 60% of capacity retained when the current rate is increased from 100 mA g−1 to 2000 mA g−1. Characterization reveals that the insertion of methyl viologen causes phase transformation of the organic host, and embodies guest-host chemical bonding. First-principles density functional theory calculations suggest strong guest-host interaction beyond the pure ionic bonding, where a large extent of covalency may exist. This study extends the boundary of battery chemistry to large molecular ions as charge carriers and also highlights the electrochemical assembly of a supramolecular system., Rechargeable batteries are governed by reversible intercalation reactions. Here the authors expand the intercalation chemistry to include methyl viologen as a large dicationic charge carrier in aqueous batteries. The bonding between guest and aromatic host is not pure ionic but shows strong covalent character.