Potassium-ion batteries using KFSI in monoglyme electrolytes: Implications of cation solvation on the K+-graphite (co-)intercalation mechanism - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Energy Storage Materials Année : 2022

Potassium-ion batteries using KFSI in monoglyme electrolytes: Implications of cation solvation on the K+-graphite (co-)intercalation mechanism

Résumé

Recently potassium-ion batteries have been proposed as a promising next generation battery technology owing to cost effectiveness and a wide range of electrode materials as well as electrolytes available. Potassium bis(fluorosulfonyl)imide (KFSI) in monoglyme (DME) is one potential electrolyte, wherein the K+ solvation heavily depends on the salt concentration and strongly affects the electrochemistry. Pure K+ intercalation occurs for highly concentrated electrolytes (HCEs), while co-intercalation is dominant for less concentrated electrolytes. The mechanisms are easily distinguished by their galvanostatic curves as well as by operando XRD. Here Raman spectroscopy coupled with computational chemistry is used to provide in-depth knowledge about the cation solvation for a wide concentration range, all the way up to 5 M KFSI in DME. Starting from pure DME experimental and computed Raman spectra provides a detailed conformational assignment enabling us to calculate solvation numbers (SNs) of K+ by DME as a function of salt concentration for all the electrolytes. For low to medium KFSI concentrations, the SN is approximately constant, ca. 2.7, and/as there is a surplus of DME solvent available, while for HCEs, with much less DME available, the SN is <2. This reduced SN results in a thermodynamically more favored desolvation at the graphite surface, leading to intercalation, as compared to the higher SN of conventional electrolytes leading to co-intercalation, as observed also by electrochemical cycling.
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hal-03468868 , version 1 (11-10-2022)

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Phuong Nam Le Pham, Vincent Gabaudan, Athmane Boulaoued, Gustav Åvall, Patrik Johansson, et al.. Potassium-ion batteries using KFSI in monoglyme electrolytes: Implications of cation solvation on the K+-graphite (co-)intercalation mechanism. Energy Storage Materials, 2022, 45, pp.291-300. ⟨10.1016/j.ensm.2021.11.046⟩. ⟨hal-03468868⟩
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