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1. A Non‐aqueous H ₃ PO ₄ Electrolyte Enables Stable Cycling of Proton Electrodes

   https://doi.org/10.1002/anie.202010554  

   Xu, Yunkai; Wu, Xianyong; Jiang, Heng; Tang, Longteng; Koga, Kenneth Y.; Fang, Chong; Lu, Jun; Ji, Xiulei (September 2020, Angewandte Chemie International Edition)

   Abstract A non‐aqueous proton electrolyte is devised by dissolving H₃PO₄into 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. 

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2. Chaotropic Salt‐Aided “Water‐In‐Organic” Electrolyte for Highly Reversible Zinc‐Ion Batteries Across a Wide Temperature Range

   https://doi.org/10.1002/adfm.202311271  

   Wang, Ziqing; Diao, Jiefeng; Burrow, James_N; Brotherton, Zachary_W; Lynd, Nathaniel_A; Henkelman, Graeme; Mullins, Charles_Buddie (November 2023, Advanced Functional Materials)

   Abstract Aqueous zinc‐ion batteries are promising alternatives to lithium‐ion batteries due to their cost‐effectiveness and improved safety. However, several challenges, including corrosion, dendrites, and water decomposition at the Zn anode, hinder their performance. Herein, an approach is proposed, that deviates from the conventional design by adding water into a propylene carbonate‐based organic electrolyte to prepare a non‐flammable “water‐in‐organic” electrolyte. The chaotropic salt Zn(ClO₄)₂exploits the Hofmeister effect to promote the miscibility of immiscible liquid phases. Interactions between propylene carbonate and water restrict water activity and mitigate unfavorable reactions. This electrolyte facilitates preferential Zn (002) deposition and the formation of solid electrolyte interphase. Consequently, the “water‐in‐organic” electrolyte achieves a 99.5% Coulombic efficiency at 1 mA cm⁻²over 1000 cycles in Zn/Cu cells, and constant cycling over 1000 h in Zn/Zn symmetric cells. A Na_0.33V₂O₅/Zn battery exhibits impressive cycling stability with a capacity of 175 mAh g⁻¹for 800 cycles at 2 A g⁻¹. Additionally, this electrolyte enables sustainable cycling across a wide temperature range from −20 to 50 °C. The design of a “water‐in‐organic” electrolyte employing a chaotropic salt presents a potential strategy for high‐performance electrolytes in zinc‐ion batteries with a large stability window and a wide temperature range. 

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3. Enhanced Reversibility of Iron Metal Anode with a Solid Electrolyte Interphase in Concentrated Chloride Electrolytes

   https://doi.org/10.1002/adma.202419664  

   Jung, Min_Soo; Yang, Sungjin; Chen, Cheng; Jagadeesan, Sathya_Narayanan; Chen, Weiyin; Feng, Guangxia; Sui, Yiming; Jiang, Ziang; Musa, Emmanuel_N; Chiu, Nan‐Chieh; et al (March 2025, Advanced Materials)

   Abstract Iron is a promising candidate for a cost‐effective anode for large‐scale energy storage systems due to its natural abundance and well‐established mass production. Recently, Fe‐ion batteries (FeIBs) that use ferrous ions as the charge carrier have emerged as a potential storage solution. The electrolytes in FeIBs are necessarily acidic to render the ferrous ions more anodically stable, allowing a wide operation voltage window. However, the iron anode suffers severe hydrogen evolution reaction with a low Coulombic efficiency (CE) in an acidic environment, shortening the battery cycle life. Herein, a hybrid aqueous electrolyte that forms a solid‐electrolyte interphase (SEI) layer on the Fe anode surface is introduced. The electrolyte mainly comprises FeCl₂and ZnCl₂as cosalts, where the Zn‐Cl anionic complex species of the concentrated ZnCl₂allows dimethyl carbonate (DMC) to be miscible with the aqueous ferrous electrolyte. SEI derived from DMC's decomposition passivates the iron surface, which leads to an average CE of 98.3% and much‐improved cycling stability. This advancement shows the promise of efficient and durable FeIBs. 

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4. Fluorination promotes lithium salt dissolution in borate esters for lithium metal batteries

   https://doi.org/10.1039/D3TA06228G  

   Ma, Peiyuan; Kumar, Ritesh; Vu, Minh Canh; Wang, Ke-Hsin; Mirmira, Priyadarshini; Amanchukwu, Chibueze V. (January 2024, Journal of Materials Chemistry A)

   Lithium metal batteries promise higher energy densities than current lithium-ion batteries but require novel electrolytes to extend their cycle life. Fluorinated solvents help stabilize the solid electrolyte interphase (SEI) with lithium metal, but are believed to have weaker solvation ability compared to their nonfluorinated counterparts and are deemed ‘poorer electrolytes’. In this work, we synthesize tris(2-fluoroethyl) borate (TFEB) as a new fluorinated borate ester solvent and show that TFEB unexpectedly has higher lithium salt solubility than its nonfluorinated counterpart (triethyl borate). Through experiments and simulations, we show that the partially fluorinated –CH2F group acts as the primary coordination site that promotes lithium salt dissolution. TFEB electrolyte has a higher lithium transference number and better rate capability compared to methoxy polyethyleneglycol borate esters reported in the literature. In addition, TFEB supports compact lithium deposition morphology, high lithium metal Coulombic efficiency, and stable cycling of lithium metal/LiFePO4 cells. This work ushers in a new electrolyte design paradigm where partially fluorinated moieties enable salt dissolution and can serve as primary ion coordination sites for next-generation electrolytes. 

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5. Coupling of 3D Porous Hosts for Li Metal Battery Anodes with Viscous Polymer Electrolytes

   https://doi.org/10.1149/1945-7111/ac47ea  

   Park, Bumjun; Oh, Christiana; Yu, Sooyoun; Yang, Bingxin; Myung, Nosang Vincent; Bohn, Paul W.; Schaefer, Jennifer L (January 2022, Journal of The Electrochemical Society)

   As the energy storage markets demand increased capacity of rechargeable batteries, Li metal anodes have regained major attention due to their high theoretical specific capacity. However, Li anodes tend to have dendritic growth and constant electrolyte consumption upon cycling, which lead to safety concerns, low Coulombic efficiency, and short cycle life of the battery. In this work, both conductive and non-conductive 3D porous hosts were coupled with a viscous (melt) polymer electrolyte. The cross-section of the hosts showed good contact between porous hosts and the melt polymer electrolyte before and after extensive cycling, indicating that the viscous electrolyte successfully refilled the space upon Li stripping. Upon deep Li deposition/stripping cycling (5 mAh cm-2), the non-conductive host with the viscous electrolyte successfully cycled, while conductive host allowed rapid short circuiting. Post-mortem cross-sectional imaging showed that the Li deposition was confined to the top layers of the host. COMSOL simulations indicated that current density was higher and more restricted to the top of the conductive host with the polymer electrolyte than the liquid electrolyte. This resulted in quicker short circuiting of the polymer electrolyte cell during deep cycling. Thus, the non-conductive 3D host is preferred for coupling with the melt polymer electrolyte. 

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