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Abstract Aqueous electrolytes typically suffer from poor electrochemical stability; however, eutectic aqueous solutions—25 wt.% LiCl and 62 wt.% H3PO4—cooled to −78 °C exhibit a significantly widened stability window. Integrated experimental and simulation results reveal that, upon cooling, Li+ions become less hydrated and pair up with Cl−, ice‐like water clusters form, and H⋅⋅⋅Cl−bonding strengthens. Surprisingly, this low‐temperature solvation structure does not strengthen water molecules’ O−H bond, bucking the conventional wisdom that increasing water's stability requires stiffening the O−H covalent bond. We propose a more general mechanism for water's low temperature inertness in the electrolyte: less favorable solvation of OH−and H+, the byproducts of hydrogen and oxygen evolution reactions. To showcase this stability, we demonstrate an aqueous Li‐ion battery using LiMn2O4cathode and CuSe anode with a high energy density of 109 Wh/kg. These results highlight the potential of aqueous batteries for polar and extraterrestrial missions.
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This content will become publicly available on December 1, 2025
Impact of molecular symmetry on crystallization pathways in highly supersaturated KH2PO4 solutions
Abstract Solute structure and its evolution in supersaturated aqueous solutions are key clues to understand Ostwald’s step rule. Here, we measure the structural evolution of solute molecules in highly supersaturated solutions of KH2PO4(KDP) and NH4H2PO4(ADP) using a combination of electrostatic levitation and synchrotron X-ray scattering. The measurement reveals the existence of a solution-solution transition in KDP solution, caused by changing molecular symmetries and structural evolution of the solution with supersaturation. Moreover, we find that the molecular symmetry of H2PO4-impacts on phase selection. These findings manifest that molecular symmetry and its structural evolution can govern the crystallization pathways in aqueous solutions, explaining the microscopic origin of Ostwald’s step rule.
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- Award ID(s):
- 2132131
- PAR ID:
- 10601377
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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