Electrochemical characterisation of a lithium-ion battery electrolyte based on mixtures of carbonates with a ferrocene-functionalised imidazolium electroactive ionic liquid

Abstract

Electrolytic solutions of lithium-ion batteries can be modified with additives to improve their stability and safety. Electroactive molecules can be used as such additives to act as an electron (redox) shuttle between the two electrodes to prevent overcharging. The electroactive ionic liquid, 1-ferrocenylmethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (TFSI), was synthesised and its electrochemical properties were investigated when diluted with ethylene carbonate-diethyl carbonate solvent at various concentrations. Cyclic voltammetry data were gathered to determine the redox potential, diffusion coefficient and heterogeneous rate constants of the electroactive imidazolium TFSI ionic liquid in the carbonate solution. The properties of this molecule as an additive in lithium battery electrolytes were studied in standard coin cells with a metallic Li anode and a Li4Ti5O12 cathode.

Synthesis and characterization of an electroactive ionic liquid based on the ferrocenylsulfonyl(trifluoromethylsulfonyl)imide anion

“…The formation of a zwitterion upon oxidation of FcNTf can also decrease the rate constant because of an energetic cost due to an intern reorganization following the Marcus model framework. A reduction in the k 0 was also reported for a Fc unit linked on one of the alkyl chain of the methylimidazolium cation[13,28].…”

“…In addition, the current library of RILs almost exclusively contains structures based on the modification of alkylimidazoliums, with some exceptions from reports on ferrocene-functionalized phosphonium IL [14,25] and metallocenium ILs [26,27]. Our group reported on the development of RIL as redox additive in electrolytes for lithium-ion batteries to protect the cathode against overcharging [28,29]. Cathode overcharging can lead to electrode and electrolyte degradation and thermal runaway which is aggravated by the use of solvents with a high vapor pressure [30][31][32].…”

Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

“…Neat ionic liquids (ILs) have been studied extensively since they are promising candidates for different applications,1 e. g. in the fields of catalysis,2, 3, 4 fuel cells,5,6 lithium ion batteries,7, 8, 9 solvents,10,11 lubricants,12,13 sensors,14,15 and gas separation technologies,15, 16, 17 to name only a few. In many of these applications, the surface of the IL plays a decisive role, because it is its interface to the environment.…”

Task-Specific Ionic Liquids for Electrochemical Applications

“…These ferrocenated phosphonium ILs show similar electron transport properties as those redox ILs based on the combinations of redox groupings with imidazolium and with short-chain polyether functionalities. Forgie et al [ 131 ] prepared a ferrocenylsubstituted imidazolium IL (Scheme 8.15 ). In its neat form, this IL has a high viscosity and low conductivity.…”