Effects of mechanical grinding on the phase behavior and anhydrous proton conductivity of imidazolium hydrogen succinate

Anhydrous organic proton conductors have attracted considerable attention as potential candidates for next-generation solid electrolytes in fuel cells. For further material development, a clear understanding of the conduction mechanism is essential, which can be accessed using crystalline materials as model systems. Recently, it has been reported that single-crystalline imidazolium hydrogen succinate (Im-Suc) exhibits a structural transition with the orientational disordering of imidazolium, which promotes proton conduction. In this study, we investigated the effects of mechanical grinding on the phase behavior and anhydrous proton conductivity of Im-Suc by comparing single-crystalline and mechanically crushed powder samples to understand the connection between ideal single crystals and highly disordered polymer systems. Thermal and structural analyses showed that grinding suppressed the structural transition through the introduction of structural disorder and mechanical stress. Moreover, the anhydrous proton conductivity was drastically enhanced with a significant decrease in activation energy in the low-temperature regime. Infrared spectroscopy indicated that the imidazolium dynamics was modulated by mechanical grinding. These findings reveal the possibility of improving the performance of anhydrous organic proton conductors and modulating their molecular dynamics properties and conduction mechanisms by simple mechanical grinding. [Display omitted] •Mechanical grinding effects were investigated for the single crystals (1c) and powder (1p) of imidazolium hydrogen succinate.•The high-temperature phase partially precipitated, while the bulk structural transition observed for 1c was suppressed in 1p.•1p showed drastically higher proton conductivity with lower activation energy than 1c at a lower temperature.•IR spectroscopy indicated that the imidazolium dynamics was modulated by mechanical grinding.