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Aqueous sodium-ion batteries are practically promising for large-scale energy storage, however energy density and lifespan are limited by water decomposition. Current methods to boost water stability include, expensive fluorine-containing salts to create a solid electrolyte interface and addition of potentially-flammable co-solvents to the electrolyte to reduce water activity. However, these methods significantly increase costs and safety risks. Shifting electrolytes from near neutrality to alkalinity can suppress hydrogen evolution while also initiating oxygen evolution and cathode dissolution. Here, we present an alkaline-type aqueous sodium-ion batteries with Mn-based Prussian blue analogue cathode that exhibits a lifespan of 13,000 cycles at 10 C and high energy density of 88.9 Wh kg−1 at 0.5 C. This is achieved by building a nickel/carbon layer to induce a H3O+-rich local environment near the cathode surface, thereby suppressing oxygen evolution. Concurrently Ni atoms are in-situ embedded into the cathode to boost the durability of batteries. Aqueous sodium-ion batteries show promise for large-scale energy storage, yet face challenges due to water decomposition, limiting their energy density and lifespan. Here, the authors report a cathode surface coating strategy in an alkaline electrolyte to enhance the stability of both electrolyte and battery. [ABSTRACT FROM AUTHOR]

Rechargeable halide-ion batteries (HIBs) are good candidates for large-scale due to their appealing energy density, low cost, and dendrite-free features. However, state-of-the-art electrolytes limit the HIBs' performance and cycle life. Here, via experimental measurements and modelling approach, we demonstrate that the dissolutions in the electrolyte of transition metal and elemental halogen from the positive electrode and discharge products from the negative electrode cause the HIBs failure. To circumvent these issues, we propose the combination of fluorinated low-polarity solvents with a gelation treatment to prevent dissolutions at the interphase, thus, improving the HIBs' performance. Using this approach, we develop a quasi-solid-state Cl-ion-conducting gel polymer electrolyte. This electrolyte is tested in a single-layer pouch cell configuration with an iron oxychloride-based positive electrode and a lithium metal negative electrode at 25 °C and 125 mA g–1. The pouch delivers an initial discharge capacity of 210 mAh g–1 and a discharge capacity retention of almost 80% after 100 cycles. We also report assembly and testing of fluoride-ion and bromide-ion cells using quasi-solid-state halide-ion-conducting gel polymer electrolyte. State-of-the-art electrolytes limit the cycle life of halide-ion batteries. Here, the authors report a fluorinated low-polar gel polymer electrolyte capable of improving the stability of the electrolyte and electrode interphases to boost battery performance. [ABSTRACT FROM AUTHOR]

The instability of carbonate electrolyte with metallic Li greatly limits its application in high‐voltage Li metal batteries. Here, a "salt‐in‐salt" strategy is applied to boost the LiNO3 solubility in the carbonate electrolyte with Mg(TFSI)2 carrier, which enables the inorganic‐rich solid electrolyte interphase (SEI) for excellent Li metal anode performance and also maintains the cathode stability. In the designed electrolyte, both NO3− and PF6− anions participate in the Li+‐solvent complexes, thus promoting the formation of inorganic‐rich SEI. Our designed electrolyte has achieved a superior Li CE of 99.7 %, enabling the high‐loading NCM811||Li (4.5 mAh cm−2) full cell with N/P ratio of 1.92 to achieve 84.6 % capacity retention after 200 cycles. The enhancement of LiNO3 solubility by divalent salts is universal, which will also inspire the electrolyte design for other metal batteries. [ABSTRACT FROM AUTHOR]

Rechargeable Zn‐ion batteries (ZIBs) are widely regarded as promising candidates for large‐scale energy storage applications. Like most multivalent battery systems (based on Zn, Mg, Ca, etc.), further progress in ZIB development relies on the discovery and design of novel cathode hosts capable of reversible Zn2+ (de)intercalation. Herein, this work employs VPO4F as a ZIB cathode and explores ensuing intercalation mechanisms along with interfacial dynamics during cycling to quantify the water dynamics in concentrated electrolytes and/or hybrid aqueous‐non aqueous (HANEs) electrolyte(s). Like most oxide‐based cathode materials, proton (H+) intercalation dominates electrochemical activity during discharge of ZnxHyVPO4F in aqueous media due to the hydroxylated nature of the interface. Such H+ electrochemistry diminishes low‐rate and/or long‐term electrochemical performance of ZIBs which inhibits implementation for practical applications. Thus, quantification of the water dynamics in various electrolytes is demonstrated for the first time. Detailed investigations of water mobility in various concentrated electrolytes and HANEs systems enable the design of an electrolyte that enhances aqueous anodic stability and suppresses water/proton activity during discharge. Tuning Zn2+/H+ intercalation kinetics simultaneously allows for a high voltage (1.9 V) and long‐lasting aqueous zinc‐ion battery: Zn|Zn(OTf)2·nH2O‐PC|ZnxHyVPO4F. [ABSTRACT FROM AUTHOR]

Water‐in‐salt electrolytes (WISE) have largely widened the electrochemical stability window (ESW) of aqueous electrolytes by formation of passivating solid electrolyte interphase (SEI) on anode and also absorption of the hydrophobic anion‐rich double layer on cathode. However, the cathodic limiting potential of WISE is still too high for most high‐capacity anodes in aqueous sodium‐ion batteries (ASIBs), and the cost of WISE is also too high for practical application. Herein, a low‐cost 19 m (m: mol kg−1) bi‐salts WISE with a wide ESW of 2.8 V was designed, where the low‐cost 17 m NaClO4 extends the anodic limiting potential to 4.4 V, while the fluorine‐containing salt (2 m NaOTF) extends the cathodic limiting potential to 1.6 V by forming the NaF–Na2O–NaOH SEI on anode. The 19 m NaClO4–NaOTF–H2O electrolyte enables a 1.75 V Na3V2(PO4)3∥Na3V2(PO4)3 full cell to deliver an appreciable energy density of 70 Wh kg−1 at 1 C with a capacity retention of 87.5 % after 100 cycles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The lack of high‐power and stable cathodes prohibits the development of rechargeable metal (Na, Mg, Al) batteries. Herein, poly(hexaazatrinaphthalene) (PHATN), an environmentally benign, abundant and sustainable polymer, is employed as a universal cathode material for these batteries. In Na‐ion batteries (NIBs), PHATN delivers a reversible capacity of 220 mAh g−1 at 50 mA g−1, corresponding to the energy density of 440 Wh kg−1, and still retains 100 mAh g−1 at 10 Ag−1 after 50 000 cycles, which is among the best performances in NIBs. Such an exceptional performance is also observed in more challenging Mg and Al batteries. PHATN retains reversible capacities of 110 mAh g−1 after 200 cycles in Mg batteries and 92 mAh g−1 after 100 cycles in Al batteries. DFT calculations, X‐ray photoelectron spectroscopy, Raman, and FTIR show that the electron‐deficient pyrazine sites in PHATN are the redox centers to reversibly react with metal ions. [ABSTRACT FROM AUTHOR]

Abstract: Low‐cost multivalent battery chemistries (Mg2+, Al3+) have been extensively investigated for large‐scale energy storage applications. However, their commercialization is plagued by the poor power density and cycle life of cathodes. A universal polyimides@CNT (PI@CNT) cathode is now presented that can reversibly store various cations with different valences (Li+, Mg2+, Al3+) at an extremely fast rate. The ion‐coordination charge storage mechanism of PI@CNT is systemically investigated. Full cells using PI@CNT cathodes and corresponding metal anodes exhibit long cycle life (>10000 cycles), fast kinetics (>20 C), and wide operating temperature range (−40 to 50 °C), making the low‐cost industrial polyimides universal cathodes for different multivalent metal batteries. The stable ion‐coordinated mechanism opens a new foundation for the development of high‐energy and high‐power multivalent batteries. [ABSTRACT FROM AUTHOR]

Abstract: Sustainable sodium‐ion batteries (SSIBs) using renewable organic electrodes are promising alternatives to lithium‐ion batteries for the large‐scale renewable energy storage. However, the lack of high‐performance anode material impedes the development of SSIBs. Herein, we report a new type of organic anode material based on azo group for SSIBs. Azobenzene‐4,4′‐dicarboxylic acid sodium salt is used as a model to investigate the electrochemical behaviors and reaction mechanism of azo compound. It exhibits a reversible capacity of 170 mAh g−1 at 0.2C. When current density is increased to 20C, the reversible capacities of 98 mAh g−1 can be retained for 2000 cycles, demonstrating excellent cycling stability and high rate capability. The detailed characterizations reveal that azo group acts as an electrochemical active site to reversibly bond with Na+. The reversible redox chemistry between azo compound and Na ions offer opportunities for developing long‐cycle‐life and high‐rate SSIBs. [ABSTRACT FROM AUTHOR]

Narrow electrochemical stability window (1.23 V) of aqueous electrolytes is always considered the key obstacle preventing aqueous sodium-ion chemistry of practical energy density and cycle life. The sodium-ion water-in-salt electrolyte (NaWiSE) eliminates this barrier by offering a 2.5 V window through suppressing hydrogen evolution on anode with the formation of a Na+-conducting solid-electrolyte interphase (SEI) and reducing the overall electrochemical activity of water on cathode. A full aqueous Na-ion battery constructed on Na0.66[Mn0.66Ti0.34]O2 as cathode and NaTi2(PO4)3 as anode exhibits superior performance at both low and high rates, as exemplified by extraordinarily high Coulombic efficiency (>99.2%) at a low rate (0.2 C) for >350 cycles, and excellent cycling stability with negligible capacity losses (0.006% per cycle) at a high rate (1 C) for >1200 cycles. Molecular modeling reveals some key differences between Li-ion and Na-ion WiSE, and identifies a more pronounced ion aggregation with frequent contacts between the sodium cation and fluorine of anion in the latter as one main factor responsible for the formation of a dense SEI at lower salt concentration than its Li cousin. [ABSTRACT FROM AUTHOR]

The redox chemistry of magnesium and its application in rechargeable Mg batteries has received increasing attention owing to the unique benefits of Mg metal electrodes, namely high reversibility without dendrite formation, low reduction potentials, and high specific capacities. The Mg/S couple is of particular interest owing to its high energy density and low cost. Previous reports have confirmed the feasibility of a rechargeable Mg/S battery; however, only limited cycling stability was achieved, and the complicated procedure for the preparation of the electrolytes has significantly compromised the benefits of Mg/S chemistry and hindered the development of Mg/S batteries. Herein, we report the development of the first rechargeable Mg/S battery with a MgTFSI2/MgCl2/DME electrolyte (DME=1,2-dimethoxyethane, TFSI=bis(trifluoromethanesulfonyl)imide) and realize the best cycling stability among all reported Mg/S batteries by suppressing polysulfide dissolution. Mechanistic studies show that the battery works via S0/MgS x redox processes and that the large voltage hysteresis is mainly due to the Mg anode overpotential. [ABSTRACT FROM AUTHOR]

Aluminum metal is a promising anode material for next generation rechargeable batteries owing to its abundance, potentially dendrite-free deposition, and high capacity. The rechargeable aluminum/sulfur (Al/S) battery is of great interest owing to its high energy density (1340 Wh kg−1) and low cost. However, Al/S chemistry suffers poor reversibility owing to the difficulty of oxidizing AlS x. Herein, we demonstrate the first reversible Al/S battery in ionic-liquid electrolyte with an activated carbon cloth/sulfur composite cathode. Electrochemical, spectroscopic, and microscopic results suggest that sulfur undergoes a solid-state conversion reaction in the electrolyte. Kinetics analysis identifies that the slow solid-state sulfur conversion reaction causes large voltage hysteresis and limits the energy efficiency of the system. [ABSTRACT FROM AUTHOR]

A SnP3 anode material with a theoretical volumetric capacity of 6890 mAh cm−3 is investigated for Na‐ion batteries. The SnP3/C can deliver a reversible capacity of 810 mAh g−1 at a current density of 150 mA g−1 for 150 cycles. The superior performance is attributed to the strong bonding interaction of P and Sn after desodiation. [ABSTRACT FROM AUTHOR]

High-aspect-ratio cobalt-oxide-coated Tobacco mosaic virus (TMV-) assembled polytetrafluoroethylene (PTFE) nonstick surfaces were integrated with a solvent-free polymer electrolyte to create an anode-electrolyte interface for use in lithium-ion batteries. The virus-assembled PTFE surfaces consisted primarily of cobalt oxide and were readily intercalated with a low-molecular-weight poly (ethylene oxide) (PEO) based diblock copolymer electrolyte to produce a solid anode-electrolyte system. The resulting polymercoated virus-based system was then peeled from the PTFE backing to produce a flexible electrode-electrolyte component. Electrochemical studies indicated the virus-structured metal-oxide PEO-based interface was stable and displayed robust charge transfer kinetics. Combined, these studies demonstrate the development of a novel solid-state electrode architecture with a unique peelable and flexible processing attribute. [ABSTRACT FROM AUTHOR]

Abstract: The increase in energy density and power density requirements for lithium-ion secondary cells for commercial applications has led to a search for higher capacity electrode materials than those available today. Silicon would seem to be a possible alternative for the graphite or carbon anode because its intercalation capacity is the highest known. However, the large capacity fade observed during initial cycling has prevented the silicon anode from being commercialized. Here we present a review of methodologies adopted for reducing the capacity fade observed in silicon-based anodes, discuss the challenges that remain in using silicon and silicon-based anodes, and propose possible approaches for overcoming them. [Copyright &y& Elsevier]

Abstract: LiFe0.9Mg0.1PO4 material was prepared by mechanical milling method, followed by heat treatment. The equilibrium potential-composition isotherm of LiFe0.9Mg0.1PO4 and charge–discharge kinetics of LiFe0.9Mg0.1PO4 were measured using galvanostatic intermittent titration technique (GITT), potential-step chronoamperometry (PSCA), and electrochemical impedance spectroscopy (EIS). The rate performance of the cathode is controlled by the charge-transfer kinetics, electronic conductivity, Li-ion diffusion capability, and phase transformation rate. Since LiFe0.9Mg0.1PO4 has a fast charge-transfer reaction and high electronic and ionic diffusivity, the phase transformation between LiFe0.9Mg0.1PO4 and Li0.1Fe0.9Mg0.1PO4 begins to play a more important role in the charge–discharge process, as is evident by an inductive loop induced by the phase transformation in the low frequency region of EIS. The phase purity and morphology of LiFe0.9Mg0.1PO4 were also observed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). [Copyright &y& Elsevier]

Rechargeable Li–S batteries are regarded as one of the most promising next‐generation energy‐storage systems. However, the inevitable formation of Li dendrites and the shuttle effect of lithium polysulfides significantly weakens electrochemical performance, preventing its practical application. Herein, a new class of localized high‐concentration electrolyte (LHCE) enabled by adding inert fluoroalkyl ether of 1H,1H,5H‐octafluoropentyl‐1,1,2,2‐tetrafluoroethyl ether into highly‐concentrated electrolytes (HCE) lithium bis(fluorosulfonyl) imide/dimethoxyether (DME) system is reported to suppress Li dendrite formation and minimize the solubility of the high‐order polysulfides in electrolytes, thus reducing the amount of electrolyte in cells. Such a unique LHCE can achieve a high coulombic efficiency of Li plating/stripping up to 99.3% and completely suppressing the shuttling effect, thus maintaining a S cathode capacity of 775 mAh g−1 for 150 cycles with a lean electrolyte of 4.56 g A−1 h−1. The LHCE reduces the solubility of lithium polysulfides, allowing the Li/S cell to achieve super performance in a lean electrolyte. This conception of using inert diluents in a highly concentrated electrolyte can accelerate commercialization of Li–S battery technology. [ABSTRACT FROM AUTHOR]

The wide applications of rechargeable batteries require state‐of‐the‐art batteries that are sustainable (abundant resource), tolerant to high‐temperature operations, and excellent in delivering high capacity and long‐term cycling life. Due to the scarcity and uneven distribution of lithium, it is urgent to develop alternative rechargeable batteries. Herein, an organic compound, azobenzene‐4,4′‐dicarboxylic acid potassium salts (ADAPTS) is developed, with an azo group as the redox center for high performance potassium‐ion batteries (KIBs). The extended π‐conjugated structure in ADAPTS and surface reactions between ADAPTS and K‐ions enable the stable charge/discharge of K‐ion batteries even at high temperatures up to 60 °C. When operated at 50 °C, ADAPTS anode delivers a reversible capacity of 109 mAh g−1 at 1C for 400 cycles. A reversible capacity of 77 mAh g−1 is retained at 2C for 1000 cycles. At 60 °C, the ADAPTS‐based KIBs deliver a high capacity of 113 mAh g−1 with 81% capacity retention at 2C after 80 cycles. The exceptional electrochemical performance demonstrates that ADAPTS is a promising electrode material for high‐temperature KIBs. An organic anode based on an azo group as the redox center is designed and synthesized for high temperature potassium‐ion batteries. The surface reaction‐controlled mechanism between the azo compound and K‐ions enables superior electrochemical performance of K‐ion batteries with an operating temperature up to 60 °C. [ABSTRACT FROM AUTHOR]

Rechargeable magnesium and calcium metal batteries (RMBs and RCBs) are promising alternatives to lithium-ion batteries because of the high crustal abundance and capacity of magnesium and calcium. Yet, they are plagued by sluggish kinetics and parasitic reactions. We found a family of methoxyethyl-amine chelants that greatly promote interfacial charge transfer kinetics and suppress side reactions on both the cathode and metal anode through solvation sheath reorganization, thus enabling stable and highly reversible cycling of the RMB and RCB full cells with energy densities of 412 and 471 watt-hours per kilogram, respectively. This work provides a versatile electrolyte design strategy for divalent metal batteries. [ABSTRACT FROM AUTHOR]

Rechargeable alkaline zinc-air batteries promise high energy density and safety but suffer from the sluggish 4 electron (e−)/oxygen (O2) chemistry that requires participation of water and from the electrochemical irreversibility originating from parasitic reactions caused by caustic electrolytes and atmospheric carbon dioxide. Here, we report a zinc-O2/zinc peroxide (ZnO2) chemistry that proceeds through a 2e−/O2 process in nonalkaline aqueous electrolytes, which enables highly reversible redox reactions in zinc-air batteries. This ZnO2 chemistry was made possible by a water-poor and zinc ion (Zn2+)–rich inner Helmholtz layer on the air cathode caused by the hydrophobic trifluoromethanesulfonate anions. The nonalkaline zinc-air battery thus constructed not only tolerates stable operations in ambient air but also exhibits substantially better reversibility than its alkaline counterpart. [ABSTRACT FROM AUTHOR]

We demonstrate for the first time that by simply substituting ether-based electrolyte (1.0 M NaCF 3 SO 3 in diglyme) for the commonly used carbonate-based electrolyte, the cyclability of FeS 2 towards sodium storage can be significantly improved. A sodiation capacity over 600 mAh/g and a discharge energy density higher than 750 Wh/kg are obtained for FeS 2 at 20 mA/g. When tested at 60 mA/g, FeS 2 presents a sodiation capacity of 530 mAh/g and retains 450 mAh/g after 100 cycles, much better than the cycling performance of Na/FeS 2 tested in carbonate-based electrolyte. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) are promising candidatesfor the applicationsof large-scale energy storage due to their cost-effective and environmental-friendlycharacteristics. Nevertheless, it remains a practical challenge tofind a cathode material of SIBs showing ideal performance (capacity,reversibility, etc.). We report here a nanocomposite material of amorphous,porous FePO4nanoparticles electrically wired by single-wallcarbon nanotubes as a potential cathode material for SIBs. The hydrothermallysynthesized nanocomposite shows excellent cell performance with unprecedentedcycling stability and reversibility. The discharge capacity of ashigh as 120 mAh/g is delivered at a 0.1 C rate (10 mA/g). The capacityretentions are about 70 mAh/g, 60 mAh/g, and 55 mAh/g at higher currentsof 20 mA/g, 40 mA/g, and 60 mA/g, respectively. Even at a 1 C rate(100 mA/g), a capacity of about 50 mAh/g is still retained after 300cycles. With a simple synthetic procedure, cost-effective chemicals,and desirable cell performance, this method offers a highly promisingcandidate for commercialized cathode materials of SIBs. [ABSTRACT FROM AUTHOR]