Cation‐Assisted Lithium‐Ion Transport for High‐Performance PEO‐based Ternary Solid Polymer Electrolytes

Abstract

N-alkyl-N-alkyl pyrrolidinium-based ionic liquids (ILs) are promising candidates as non-flammable plasticizers for lowering the operation temperature of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs), but they present limitations in terms of lithium-ion transport, such as am uchl ower lithium transference number.T hus,apyrrolidinium cation was prepared with an oligo(ethylene oxide) substituent with seven repeating units.Weshow, by acombination of experimental characterizations and simulations,that the cationssolvating properties allow faster lithium-ion transport than alkyl-substituted analogues when incorporated in SPEs. This proceeds not only by accelerating the conduction modes of PEO,but also by enabling new conduction modes linked to the solvation of lithium by as ingle IL cation. This,c ombined with favorable interfacial properties versus lithium metal, leads to significantly improved performance on lithium-metal polymer batteries.

Ether‐Functionalized Pyrrolidinium‐Based Room Temperature Ionic Liquids: Physicochemical Properties, Molecular Dynamics, and the Lithium Ion Coordination Environment

“…RTILs containing ether oxygen atoms have been investigated for use as electrolytes in energy storage devices due to their relatively high ionic conductivities. Furthermore, it has been reported that the interaction of the cation with the ether oxygen atom can change the solvation state of the metal ion, thereby promoting electrochemical reactions [19,24–26] . When a Li ion is dissolved in TFSA‐based RTILs without a heteroatom in the side chain, a [Li(TFSA) 2 ] − complex is formed in the mixture [27–29] .…”

“…When a Li ion is dissolved in TFSA‐based RTILs without a heteroatom in the side chain, a [Li(TFSA) 2 ] − complex is formed in the mixture [27–29] . On the other hand, in RTILs that contain ether oxygen atoms, it has been reported that the nucleophilicity of the ether oxygen atom affects the coordination environment of the Li ion [24–26] . The interaction of the cation side chain with the metal ion and the application of such species in electrochemical reactions has also been investigated using Na + , Zn 2+ , Mg 2+ , and Ca 2+ ions, among others [30–33] .…”

Functional additives for solid polymer electrolytes in flexible and high‐energy‐density solid‐state lithium‐ion batteries

“…For example, an N-methyl-N-oligo(ethylene oxide) pyrrolidinium TFSI with a median oligo(ethylene oxide) chain length of seven repeating units was designed to facilitate fast Li-ion transport by accelerating the PEO segmental mobility and the solvation of Li ions by a single IL cation (Figure 7A). 119 Such a strategy can be further applied to design other types of ILs.…”

Regulation of SEI Formation by Anion Receptors to Achieve Ultra‐Stable Lithium‐Metal Batteries

“…For instance, the electrolyte consisting of fluoroethylene carbonate (FEC) with a small amount of LiNO 3 dissolved in ether solvent has been found to effectively prevent the growth of Li dendrite, thus improving the Coulombic efficiency of LMBs [27, 28] . Recently, polymer electrolyte (such as the octaphenyl polyoxyethylene (OP‐10)‐based sol electrolyte [29, 30] ) has also been proposed as a promising solution to prevent lithium dendrite growth [29–33] . Besides, the choice of electrolyte can largely determine the chemical composition and structures of the solid electrolyte interphase (SEI) layers on Li‐metal surface [34–36] .…”