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Polymer-Ionic Liquid Gel Electrolytes for Lithium-Ion Batteries
Published in Prasanth Raghavan, Fatima M. J. Jabeen, Polymer Electrolytes for Energy Storage Devices, 2021
Lithium bis (trifluoromethane sulfonyl)imide (LiTFSI) is a hydrophilic salt with the chemical formula LiC2F6NO4S2. It is a widely accepted Li+-ion source in commercially available LIBs. After the introduction of LiTFSI, lithium hexafluorophosphate became less attractive because of its poorer performance when compared with LiTFSI. Free-standing PILGEs, consisting of a PIL, poly[diallyldimethylammonium] bis-trifluoromethane sulfonimide] (PDAD-MATFSI), an IL, 1-ethyl-3-methylimidazolium bis-trifluoromethane sulfonimide and a Li salt for LIB application, was developed by Safa et al. [17]. In a typical procedure, the pyrrolidinium-based PIL, PDAD-MATFSI, was synthesized by a simple anion-exchange reaction between the chlorinated polymer and LiTFSI. The as-synthesized PIL was insoluble in water but readily soluble in acetone. Furthermore, the IL, 1-ethyl-3-methyl imidazolium bis (trifluoromethane sulfonyl)imide (EMIM-TFSI), was synthesized by reacting [EMIM][Cl] and LiTFSI in de-ionized water. The as-synthesized IL was colorless, odorless, and a fluid, which was dried at 60°C in a vacuum oven for two hours and immediately stored in an oxygen-free and humidity-free glove-box until later use. Furthermore, the GPE was synthesized in a procedure consisting of mixing an already prepared 1 M LiTFSI in [EMIM][TFSI] with 20 wt.% of PIL (final composition 80:20 electrolyte: PIL by weight). This mixture was dissolved in acetone and stirred (or sonicated) until completely dissolved. The final solution was drop-cast on a 0.0127 m circular polydimethylsiloxane (PDMS) template and enough time was given to evaporate the acetone from it, before it was vacuum dried at 90°C for 72 hours. The PILGE film developed in this way was transparent and free-standing. The PILGE film was thermally stable and contained IL and salt contents of up to 80 wt.%. This high concentration was found to enhance the ionic conductivity of the electrolyte films. A high ionic conductivity of 3.35X10−3 S cm−1 was obtained for the electrolyte films. Combining PIL with the salt component has allowed the LIB to exhibit a wide electrochemical stability window of −0.1 to 4.9 V. An increased Li+-ion-transference number was also achieved. In addition, the PILGEs were found to suppress the formation of Li dendrites when compared with the pure IL component without the polymer.
The effect of short alkane bridges in stability of bisbenzimidazole-2-ylidene silver(I) complexes: synthesis, crystal structure and antibacterial activity
Published in Journal of Coordination Chemistry, 2019
Yen L. Loh, Umie F. M. Haziz, Rosenani A. Haque, A. A. Amirul, O. Noor Aidda, Mohd. R. Razali
The initial precursor, n-benzylbenzimidazole, was synthesized and characterized according to the reported procedure with minor modifications [22]. Bisbenzimidazolium dibromo salts 1a–3a were synthesized by refluxing two molars of n-benzylbenzimidazole with one molar of 1,2/3/4-dibromoethane/propane/butane (scheme 1). Bromide salts 1a–3a were converted to their respective dihexafluorophosphate salts 1b–3b for characterization and purification purposes. Hexafluorophosphate salts are soluble in common organic solvents such as dichloromethane, DMSO, DMF, acetone and acetonitrile compared to their corresponding bromide salts that are partially dissolved.