Local Structure and Dynamics in Solvent-Free Molten Salt Ca2+-Electrolytes

C Cruz and P Johansson, CHEMPHYSCHEM, 26, e202500090 (2025).

DOI: 10.1002/cphc.202500090

Calcium batteries (CaBs) fundamentally offer a promise of sustainable high energy density storage. However, the development of functional CaB electrolytes remains a key challenge. Here, molecular simulations are used to investigate structural and dynamic properties of solvent-free molten salt electrolytes (MSEs) containing Ca2+ and alkali cations (Li+, Na+, K+, paired with either FSI or TFSI anions. Two equimolar MSEs, Li, Na, K, CaFSI and Li, Na, K, Ca TFSI, are examined across a range of temperatures to better understand cation-anion interactions, coordination and local structure, and ion mobility, in particular with respect to Ca2+. The interplay between cation charge density, anion structure, and thermal effects provides valuable insights into the MSEs' macroscopic behavior. These insights inform the design of advanced electrolytes that enhance Ca2+ mobility, supporting the development of next-generation CaBs.

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