Intermolecular Interaction Mediated Potassium Ion Intercalation Chemistry in Ether‐Based Electrolyte for Potassium‐Ion Batteries

Designing electrolytes that are compatible with graphite anodes and possess flame‐retardant features is strongly demanded in potassium‐ion batteries (PIBs) to inhibit solvent co‐insertion and graphite exfoliation, and also stabilize the highly active potassium‐based species (e.g., KC8). Herein, a nonflammable electrolyte is designed by introducing the fluoroethers to stabilize graphite anodes, particularly at an ultralow concentration (<0.43 m) that is rarely reported before. It is discovered that intermolecular interactions can form between the 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether (i.e., HFE) diluent and trimethyl phosphate (TMP) flame‐retardant by electronegative fluorine (δ−F) and electropositive hydrogen (δ+H). The intermolecular interactions can change the potassium ion (K+) solvation structure (e.g., weakening the K+‐TMP interaction), and then determine the properties of the K+‐solvent‐anion complex at the electrode interface. a molecular interfacial model is presented with a new coordination mechanism involving the diluent to elucidate the relationship between the intermolecular interactions and electrode performance (i.e., K+‐solvent co‐insertion, or reversible K+ (de)intercalation) at the molecular scale, facilitating the design of high safety and high energy density potassium‐ion sulfur batteries. This study sheds light on the importance of intermolecular interactions to tune electrolyte properties and also opens new avenues for designing electrolytes for safe and practical PIBs.

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Moderately Solvating Electrolyte with Fluorinated Cosolvents for Lean‐Electrolyte Li–S Batteries

Kim,

Cho

et al. 2024

Advanced Energy Materials

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To surpass the energy density limit of current Li–S batteries, attaining a long lifespan under lean‐electrolyte conditions is imperative. The persistent challenge involves suppressing electrolyte decomposition while facilitating sulfur electrode reaction. In this study, the solvating power of 1dimethoxy ethane is fine‐tuned, the main solvent, using fluorinated ether cosolvents via H–F interactions. As the fluorination degree of the cosolvent increases, the coordination of anions around the Li‐ion increases, and the solubilities of Li polysulfides decrease. By systematically varying the solvating power, moderately solvating electrolytes are prepared that can effectively suppress the dissolution of Li polysulfides without hindering the redox kinetics. The moderately solvating electrolytes induce uniform Li deposition and reduce electrolyte decomposition owing to the formation of anion‐derived solid electrolyte interphase. An assembled pouch‐type Li–S battery containing an electrolyte with an optimized solvation power delivers 405 Wh kg−1 at an E/S ratio of 2.0 µL mgs−1 with a lifespan of over 80 cycles. This study suggests a strategy to finely tune the Li+ solvation structure for achieving well‐balanced performances of sulfur cathodes and Li‐metal anodes under lean‐electrolyte conditions.

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Intermolecular Interaction Mediated Potassium Ion Intercalation Chemistry in Ether‐Based Electrolyte for Potassium‐Ion Batteries

Cited by 11 publications

References 56 publications

Trace ethylene carbonate-mediated low-concentration ether-based electrolytes for high-voltage lithium metal batteries

Trace ethylene carbonate-mediated low-concentration ether-based electrolytes for high-voltage lithium metal batteries

Ultralow Concentration Nonflammable Electrolytes Mediated by Intermolecular Interactions for Safer Potassium‐Ion Sulfur Batteries

Moderately Solvating Electrolyte with Fluorinated Cosolvents for Lean‐Electrolyte Li–S Batteries

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