Unveiling the transport properties of protic ionic liquids: Lithium ion dynamics modulated by the anion fluorine reservoir

• Autores: de Araujo Lima e Souza, Giselle; Di Pietro, Maria Enrica; Castiglione, Franca; Fazzio Martins Martinez, Patricia; Middendorf, Maleen; Schönhoff, Monika; Fraenza, Carla Cecilia; Stallworth, Phillip; Greenbaum, Steven; Triolo, Alessandro; Appetecchi, Giovanni Battista; Mele, Andrea
• Año de publicación: 2024
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: ELECTROLYTES; PROTIC IONIC LIQUIDS; NMR RELAXATION; DIFFUSIVITY; FLUORINATED DOMAINS; IONICITY
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Protic ionic liquids (PILs) show great potential as electrolyte components for energy storage devices. A comprehensive understanding of their transport properties must be achieved to optimize the design of safer and efficient electrolytes. This study focuses on a series of PILs based on the DBUH+ cation (protonated 1,8-diazabicyclo[5,4,0]‑undec-7-ene superbase) and three anions derived from strong acids: TFO- (triflate), IM14-(perfluorobutyl-trifluoromethylsulfonylimide) and TFSI- (bis(trifluoromethylsulfonyl)imide). Neat PILs and PILs doped with LiTFO, LiIM14, and LiTFSI were studied using temperature-dependent NMR diffusion and relaxation techniques. The ionicity of these systems was also evaluated. Results revealed that the dynamic behaviour of lithium ions, as well as ionicity, strongly depend on the structural features of the anions, particularly in the caseof IM14 , whose main feature is the uneven distribution of the fluorinated sidegroups. The 19F relaxation rates in IM14- provide insights into the rotational reorientation of that anion. DBUH-IM14 exhibited diffusion coefficients lower than the expected ones on the basis of its viscosity, likely due to fluorophilic intermolecular interactions involving the fluorinated terminal groups. The presence of Li+ in the DBUH-IM14 electrolyte led to unexpected and relatively faster translational mobility of Li+ ions, resulting in a higher lithium apparent transference number. However, the trends observed in ionicity indicate a more complex interplay between intermolecular interactions and ion correlations. While DBUH-TFSI showed minimal effect of Li+ addition, DBUH-TFO and DBUH-IM14 exhibited a significant decrease in ionicity, possibly attributed to strong interactions between ions.
Fil: de Araujo Lima e Souza, Giselle. Politecnico di Milano; Italia
Fil: Di Pietro, Maria Enrica. Politecnico di Milano; Italia
Fil: Castiglione, Franca. Politecnico di Milano; Italia
Fil: Fazzio Martins Martinez, Patricia. Universidade Estadual de Campinas; Brasil
Fil: Middendorf, Maleen. Universidad de Muenster; Alemania
Fil: Schönhoff, Monika. Universidad de Muenster; Alemania
Fil: Fraenza, Carla Cecilia. City University Of New York. Hunter College; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina
Fil: Stallworth, Phillip. City University Of New York. Hunter College; Estados Unidos
Fil: Greenbaum, Steven. City University Of New York. Hunter College; Estados Unidos
Fil: Triolo, Alessandro. Consiglio Nazionale delle Ricerche; Italia
Fil: Appetecchi, Giovanni Battista. No especifíca;
Fil: Mele, Andrea. Politecnico di Milano; Italia