Unfolding the Network Structure of [Pyr14Cl/(BCl3)0.25]/(δ-MgCl2)x Ionic Liquid Using the BCl4− Probe

Magnesium batteries are emerging as a cutting-edge energy storage solution poised to revolutionize the battery industry. In this context, electrolytes play a pivotal role in the development of reliable and efficient devices. A family of new ionic liquid-based electrolytes is proposed for potential application in magnesium batteries. These electrolytes are synthesized through the reaction of 1-butyl-1-methylpyrrolidinium chloride (Pyr14Cl), boron trichloride, and varying amounts of δ-MgCl2. The thermal, structural, and coordination properties of the proposed electrolytes are studied using density functional theory calculations, high resolution thermogravimetry, modulated differential scanning calorimetry, and Fourier transform infrared investigations. For the first time, the structure and nature of interactions characterizing the anionic and cationic domains of ionic liquid electrolytes, as a function of δ-MgCl2 doping, are examined using BCl4− as a spectroscopic “ion probe”. These results are combined with features of electric response, as well as structural and local relaxation events investigated through broadband electrical spectroscopy and nuclear magnetic resonance studies, respectively, to elucidate the unique characteristics and conductivity mechanisms of the proposed materials. Finally, the reasonably high ionic conductivity of these electrolytes at room temperature makes these materials very promising for application in magnesium battery prototypes.