Pyrrolidinium‐based ionic liquids as electrolytes for lithium batteries: A Computational Study

Abstract

Electrochemical windows (ECWs) of the cyclic ammonium based ionic liquids formed by the combination of two common pyrrolidinium cations—N,N‐butylmethyl pyrrolidinum(Pyr14) and N,N‐hexylmethyl pyrrolidinium(Pyr16) and five anions—dicyanamide, trifluoroacetate, fluoromethane sulfonate, bis((trifluoromethylsulfonyl)imide, and bis(fluorosulfonyl)imide were investigated. The ECW of each ionic liquid was obtained from the oxidation and reduction potentials of these ionic liquids with respect to a Li+/Li reference electrode by using thermodynamic cycle method. The work reveals that the ECWs of these ionic liquids are solely decided by the HOMO energy of pairing anions. The ECWs were also computed using HOMO‐LUMO method employing Møller‐Plesset perturbation theory to the second order and M06L methods with a basis set of 6‐31 + G(d, p). The ECW computed using M06L functional with an extended basis set of 6‐311++G(d, p) showed better agreement with experimental values suggesting accurate computation of ECW is possible at lower computational cost.

Ionic Additives to Increase Electrochemical Utilization of Sulfur Cathode for Li-S Batteries

“…Because the usual operating potential of the Li-S cell is in the range of 1.5-3.0 V (vs. Li/Li + ), a fivemembered cyclic ammonium (pyrrolidium) is selected as a cation candidate rather than the commonly used imidazolium to avoid an electrochemical decomposition reaction ( Fig. 2a) [28,29]. Their counter anion part is derivatized by variation in the halogen elements.…”

Application of Ionic Liquids for Batteries and Supercapacitors

“…N-butyl-N-methylpyrrolidine(trifluoromethyl sulfonyl)imide (Pyr 14 TFSI) hydrophobic ionic salt has drawn a lot of research interest for ESS applications owing to its excellent thermal and electrochemical stability (up to 5.5 V) at high temperatures (up to 300 • C) [51,52]. Yang, B. et al examined the physicochemical properties of pyrrolidinum-based ILs, such as N-propyl-N-methylpyrrolidiniumbis (trifluoromethanesulfonyl)imide (Pyr 13 TFSI) electrolyte with organic additives and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) for high-safety Li-ion batteries [53]. This mixed electrolyte results in high thermal stability, non-flammability, low viscosity with a wide potential window of 4.8 V. This ILs-based electrolyte also offers low bulk resistance and the lowest interface resistance to Li-anode [54].…”

Pyrrolidinium Containing Ionic Liquid Electrolytes for Li-Based Batteries

“…Similarly to C3mpyr-based ILs, there has been extensive characterization of 1-butyl-1methylpyrrolidinium (C4mpyr)-based ILs [147], for example, Fernández-Miguez et al [115] Al 2 O 3 has been investigated as a protective agent for Li metal and has mainly been studied from the perspective of surface coating and plating technologies. Wen et al [174] utilized a leaf-like Al 2 O 3 skeleton to form a quasi-solid-state electrolyte comprising of 1 M LiTFSI, and C 3 mpyrTFSI.…”

“…Characterization of N -propyl- N -methylpyrrolidinium (C 3 mpyr)-based ILs have been carried out by many research groups to determine the physiochemical properties of the IL with various anions [ 147 , 148 ]. The biodegradability and solubility of C 3 mpyr-based ILs, and other pyrrolidinium-based ILs have also been investigated [ 149 ].…”

“…Similarly to C 3 mpyr-based ILs, there has been extensive characterization of 1-butyl-1-methylpyrrolidinium (C 4 mpyr)-based ILs [ 147 ], for example, Fernández-Miguez et al [ 115 ] investigated high (1.5 M) and low (0.1 M) LiTFSI salt concentrations within C 4 mpyrTFSI ILs. It was determined that LiTFSI salt addition leads to higher densities than that of the pure IL, but it decreased linearly with increasing temperature.…”