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Although "water-in-salt" electrolytes have opened a new pathway to expand the electrochemical stability window of aqueous electrolytes, the electrode instability and irreversible proton co-insertion caused by aqueous media still hinder the practical application, even when using exotic fluorinated salts. In this study, an accessible hybrid electrolyte class based on common sodium salts is proposed, and crucially an ethanol-rich media is introduced to achieve highly stable Na-ion electrochemistry. Here, ethanol exerts a strong hydrogen-bonding effect on water, simultaneously expanding the electrochemical stability window of the hybridized electrolyte to 2.5 V, restricting degradation activities, reducing transition metal dissolution from the cathode material, and improving electrolyte-electrode wettability. The binary ethanol-water solvent enables the impressive cycling of sodium-ion batteries based on perchlorate, chloride, and acetate electrolyte salts. Notably, a Na0.44MnO2 electrode exhibits both high capacity (81 mAh g-1) and a remarkably long cycle life >1000 cycles at 100 mA g-1 (a capacity decay rate per cycle of 0.024%) in a 1 M sodium acetate system. The Na0.44MnO2/Zn full cells also show excellent cycling stability and rate capability in a wide temperature range. The gained understanding of the hydrogen-bonding interactions in the hybridized electrolyte can provide new battery chemistry guidelines in designing promising candidates for developing low-cost and long-lifespan batteries based on other (Li+, K+, Zn2+, Mg2+, and Al3+) systems.

High-voltage Li metal solid-state batteries are in the spotlight as high energy and power density devices for the next generation of batteries. However, the lack of robust solid-electrolyte interfaces (SEIs) and the propagation of Li dendrites still need to be addressed for practical application with extended cyclability. In the present work, high-voltage Li metal cells with LiNi0.6Mn0.2Co0.2O2 active material were assembled with a polyethylene(oxide) based electrolyte mixed with lithium bis(fluorosulfonyl)imide (LiFSI) salt. The addition of Li7La3Zr2O12 garnet to form a composite electrolyte demonstrated a beneficial effect for cell cycling stability. Inspired by the improved interface of ceramic Li7La3Zr2O12 garnet and Li metal, as well as by previous knowledge of favorable SEI forming species, various additive candidates were selected to optimize its electrolyte composition. Among them, lithium hydroxide (LiOH) is a key favorable species that shows a relevant improvement in the cyclability of the cells. X-ray photoelectron spectroscopy showed that the SEI layer is composed mainly of chemical species arising from the reduction of the Li salt, with lithium fluoride (LiF) being the main product. In addition, solid-state nuclear magnetic resonance proved that LiOH induces the cleavage of the labile S–F bond, increasing the concentration of LiF. Herein, we highlight that SEI-forming additives need to be considered for the interfacial engineering design of stable SEIs to expand the performance boundary of SSBs. [ABSTRACT FROM AUTHOR]

Efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are required for metal air batteries, to replace costly metals, such as Pt and Ir/Ru based compounds, which are typically used as benchmarks for ORR and OER, respectively. Isolated single atomic sites coordinated with nitrogen on carbon supports (M‐N‐C) have promising performance for replacement of precious metal catalysts. However, most of monometallic M‐N‐C catalysts demonstrate unsatisfactory bifunctional performance. Herein, a facile way of preparing bimetallic Fe and Co sites entrapped in nitrogen‐doped hollow carbon nanospheres (Fe,Co‐SA/CS) is explored, drawing on the unique structure and pore characteristics of Zeolitic imidazole frameworks and molecular size of Ferrocene, an Fe containing species. Fe,Co‐SA/CS showed an ORR onset potential and half wave potential of 0.96 and 0.86 V, respectively. For OER, (Fe,Co)‐SA/CS attained its anodic current density of 10 mA cm–2 at an overpotential of 360 mV. Interestingly, the oxygen electrode activity (ΔE) for (Fe,Co)‐SA/CS and commercial Pt/C‐RuO2 is calculated to be 0.73 V, exhibiting the bifunctional catalytic activity of (Fe,Co)‐SA/CS. (Fe,Co)‐SA/CS evidenced desirable specific capacity and cyclic stability than Pt/C‐RuO2 mixture when utilized as an air cathode in a homemade Zinc‐air battery. [ABSTRACT FROM AUTHOR]

Battery cathode materials operating on multivalent‐ion intercalation are prone to short operational lifetimes, traditionally explained to be due to poor solid‐state diffusion. Here, we overcome this problem by using a conversion‐type cathode material and demonstrate the benefits in a FeVO4 host structure. The rechargeable Zn‐ion battery exhibits stability for an unprecedented operational lifetime of 57 days with a high capacity of 272 mAh g−1 (60 mA g−1) over 140 cycles. We use a combination of synchrotron‐based XAS, SRXTM, Raman, XRD and HRTEM techniques to elucidate the cathode material evolution at multilength‐scale for understanding the Zn‐ion storage mechanism. We further highlight the benefits of using a low‐salt concentration electrolyte and pH‐consideration analysis in aqueous battery development, the optimization of which leads to a 4‐fold increase in battery performance as compared to conventional high‐salt concentration electrolyte formulations. [ABSTRACT FROM AUTHOR]

Multivalent‐ion batteries built on water‐based electrolytes represent energy storage at suitable price points, competitive performance, and enhanced safety. However, to comply with modern energy‐density requirements, the battery must be reversible within an operating voltage window greater than 1.23 V or the electrochemical stability limits of free water. Taking advantage of its powerful solvation and catalytic activities, adding water to electrolyte preparations can unlock a wider gamut of liquid mixtures compared with strictly nonaqueous systems. However, a point‐by‐point sweep of all potential formulations is arduous and ineffective without some form of systematic rationalization. The present Review consolidates recent progress, pitfalls, limits, and insights critical to expediting aqueous electrolyte designs to boost multivalent‐ion battery outputs. Revisiting water world: The structure of H2O seems simple, but its presence commonly dictates what reaction routes and products proceed through matter–matter interactions. Molecular H2O is reviewed from an electrochemical perspective and its various influences on the feasibility of multivalent‐ion batteries are evaluated. [ABSTRACT FROM AUTHOR]

Ga-substitutedLa3Zr2Li7O12garnet isshown to be a promising Li-ion conducting electrolyte material. Thestrategy adopted in this study is the substitution of Li by Ga, therebycreating Li vacancies and enhancing the Li conductivity. Solid StateMagic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) measurementshave been used to identify the location of the substituted Ga in thestructure and its effect on the Li distribution and mobility. In additionMAS NMR was used to follow the effect of protonation due to atmosphericmoisture on the sintering behavior of these materials. In particular,it is shown that the Ga atoms are located in tetrahedral positionspromoting the random distribution of lithium over the available sites,hence promoting an increase in the conductivity. Control of the sinteringconditions by using a dry O2atmosphere leads to the formationof dense ceramic materials and avoids the degradation process dueto the exchange of Li+by H+from atmosphericmoisture. Electrochemical Impedance Spectroscopy data show total conductivitiesas high as 1.3 and 2.2 mS cm–1at 24 and 42 °C,respectively, which are among the highest Li ion conductivities reportedfor garnet-structured materials to date. [ABSTRACT FROM AUTHOR]