Phenylacetonitrile (C6H5CH2CN) Ionic Liquid Blends as Alternative Electrolytes for Safe and High-Performance Supercapacitors

Abstract

The increasing need in the development of storage devices is calling for the formulation of alternative electrolytes, electrochemically stable and safe over a wide range of conditions. To achieve this goal, electrolyte chemistry must be explored to propose alternative solvents and salts to the current acetonitrile (ACN) and tetraethylammonium tetrafluoroborate (Et4NBF4) benchmarks, respectively. Herein, phenylacetonitrile (Ph-ACN) has been proposed as a novel alternative solvent to ACN in supercapacitors. To establish the main advantages and drawbacks of such a substitution, Ph-ACN + Et4NBF4 blends were formulated and characterized prior to being compared with the benchmark electrolyte and another alternative electrolyte based on adiponitrile (ADN). While promising results were obtained, the low Et4NBF4 solubility in Ph-ACN seems to be the main limiting factor. To solve such an issue, an ionic liquid (IL), namely 1-ethyl-3-methylimidazolium bis [(trifluoromethyl)sulfonyl] imide (EmimTFSI), was proposed to replace Et4NBF4. Unsurprisingly, the Ph-ACN + EmimTFSI blend was found to be fully miscible over the whole range of composition giving thus the flexibility to optimize the electrolyte formulation over a large range of IL concentrations up to 4.0 M. The electrolyte containing 2.7 M of EmimTFSI in Ph-ACN was identified as the optimized blend thanks to its interesting transport properties. Furthermore, this blend possesses also the prerequisites of a safe electrolyte, with an operating liquid range from at least −60 °C to +130 °C, and operating window of 3.0 V and more importantly, a flash point of 125 °C. Finally, excellent electrochemical performances were observed by using this electrolyte in a symmetric supercapacitor configuration, showing another advantage of mixing an ionic liquid with Ph-ACN. We also supported key structural descriptors by density functional theory (DFT) and COnductor-like Screening Model for Real Solvents (COSMO-RS) calculations, which can be associated to physical and electrochemical properties of the resultant electrolytes.

Engineering the Interlayer Spacing by Pre‐Intercalation for High Performance Supercapacitor MXene Electrodes in Room Temperature Ionic Liquid

“…This, in part, can be related to the higher viscosity of neat EMIMTFSI than of 1 m EMIMTFSI in ACN, causing slower ion transport. [ 32 ] With lower scan rates, there is more time for ion transport throughout the volume of the electrode. The largest specific capacitance of 257 F g −1 (1428 mF cm −2 and 492 F cm −3 ) can be obtained at 1 mV s −1 , which is much larger than those of previous reports of MXenes and carbon‐based materials using ionic liquid electrolytes (details see Table S3, Supporting Information).…”

Poly(ethyl methacrylate) Composite Coatings Containing Halogen-Free Inorganic Additives with Flame-Retardant Properties

“…Halogen-based FRMs are usually introduced into the polymer chain by copolymerisation. However, halogenated FRMs are toxic and bioaccumulative [19][20][21][22][23][24][25][26].…”

Application of Octanohydroxamic Acid for Salting out Liquid–Liquid Extraction of Materials for Energy Storage in Supercapacitors

“…Supercapacitors are currently under development for various energy storage applications [ 1 , 2 ]. Investigations in this research area are focused on the synthesis of advanced electrode materials by different fabrication methods [ 3 , 4 , 5 , 6 , 7 , 8 ], optimization of electrolytes [ 9 ], design of nanocomposites [ 10 , 11 , 12 , 13 ], and modeling [ 14 ]. The synthesis of non-agglomerated particles of controlled shape and composition is of particular importance for supercapacitor technology [ 15 , 16 , 17 ].…”