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1. A Non-aqueous H3PO4 Electrolyte Enables Stable Cycling of Proton Electrodes

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

   Xu, Y.; Wu, X.; Jiang, H.; Tang, L.; Koga, K. Y.; Fang, C.; Lu, J.; Ji, X. (August 2020, Angewandte Chemie)

   null (Ed.)

   A non-aqueous proton electrolyte is devised by dissolving H3PO4 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. 

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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. A Highly Efficient All‐Solid‐State Lithium/Electrolyte Interface Induced by an Energetic Reaction

   https://doi.org/10.1002/anie.202004477  

   Zhong, Yiren; Xie, Yujun; Hwang, Sooyeon; Wang, Qian; Cha, Judy J.; Su, Dong; Wang, Hailiang (June 2020, Angewandte Chemie International Edition)

   Abstract The energetic chemical reaction between Zn(NO₃)₂and Li is used to create a solid‐state interface between Li metal and Li_6.4La₃Zr_1.4Ta_0.6O₁₂(LLZTO) electrolyte. This interlayer, composed of Zn, ZnLi_xalloy, Li₃N, Li₂O, and other species, possesses strong affinities with both Li metal and LLZTO and affords highly efficient conductive pathways for Li⁺transport through the interface. The unique structure and properties of the interlayer lead to Li metal anodes with longer cycle life, higher efficiency, and better safety compared to the current best Li metal electrodes operating in liquid electrolytes while retaining comparable capacity, rate, and overpotential. All‐solid‐state Li||Li cells can operate at very demanding current–capacity conditions of 4 mA cm⁻²–8 mAh cm⁻². Thousands of hours of continuous cycling are achieved at Coulombic efficiency >99.5 % without dendrite formation or side reactions with the electrolyte. 

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4. 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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5. Vanillin: An Effective Additive to Improve the Longevity of Zn Metal Anode in a 30 m ZnCl ₂ Electrolyte

   https://doi.org/10.1002/aenm.202301712  

   Hoang, David; Li, Yaqiong; Jung, Min_Soo; Sandstrom, Sean_K; Scida, Alexis_M; Jiang, Heng; Gallagher, Trenton_C; Pollard, Brenden_A; Jensen, Rachel; Chiu, Nan‐Chieh; et al (September 2023, Advanced Energy Materials)

   Abstract It remains a challenge to design aqueous electrolytes to secure the complete reversibility of zinc metal anodes. The concentrated water‐in‐salt electrolytes, e.g., 30 m ZnCl₂, are promising candidates to address the challenges of the Zn metal anode. However, the pure 30 m ZnCl₂electrolyte fails to deliver a smooth surface morphology and a practically relevant Coulombic efficiency. Herein, it is reported that a small concentration of vanillin, 5 mg mL_water⁻¹, added to 30 m ZnCl₂transforms the reversibility of Zn metal anode by eliminating dendrites, lowering the Hammett acidity, and forming an effective solid electrolyte interphase. The presence of vanillin in the electrolyte enables the Zn metal anode to exhibit a high Coulombic efficiency of 99.34% at a low current density of 0.2 mA cm⁻², at which the impacts of the hydrogen evolution reaction are allowed to play out. Using this new electrolyte, a full cell Zn metal battery with an anode/cathode capacity (N/P) ratio of 2:1 demonstrates no capacity fading over 800 cycles. 

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