Rheological and Ionic Transport Properties of Nanocomposite Electrolytes Based on Protic Ionic Liquids and Silica Nanoparticles

Insight into the inhibitory mechanism of soluble ionic liquids on the transport of TiO2 nanoparticles in saturated porous media: Roles of alkyl chain lengths and counteranion types

Column experiments were carried out to investigate the transport of TiO₂ nanoparticles (nTiO₂) in water-saturated porous media in the presence of various imidazolium-based ionic liquids (ILs) with different alkyl chain lengths and counteranions. The results indicated that the effects of ILs on nTiO₂ transport were considerably dependent upon IL species. In general, the transport-inhibition effects increased with the increasing length of branched alkyl chain on the ILs (i.e., [C₆mim]Cl > [C₄mim]Cl > [C₂mim]Cl). The trend was dominated by the hydrophobicity effects of ILs. Meanwhile, the inhibitory effects of ILs were strongly related to the counteranions and followed the order of [C₄mim]Cl > [C₄mim][TOS] > [C₄mim][PF₆], mainly due to different electrostatic repulsion force between nanoparticles and porous media in the presence of various ILs. Furthermore, the inhibitory role of [C₄mim][TOS] in nTiO₂ transport under acidic conditions (i.e., pH 6.5) was greater than that under alkaline conditions (i.e., pH 8.0). The dominant mechanism was that the differences in the extent of electrostatic repulsion between sand grains and nTiO₂ with or without ILs at pH 6.5 were larger than that at pH 8.0. Moreover, two-site kinetic retention model and DLVO theory provided good descriptions for the transport behaviors of nTiO₂ with different ILs.

Unveiling the Relationship between the Surface Chemistry of Nanoparticles and Ion Transport Properties of the Resulting Composite Electrolytes

Fundamental understanding of the transport properties within nanoparticle composite electrolytes is necessary for the development of next-generation electrochemical devices. Herein, the effect of surface-modified silica nanoparticles with aminophenyl, amide, and sulfonate functional groups (AP-SiO₂, AM-SiO₂, and SU-SiO₂) on the ion transport properties of composite electrolytes is systematically investigated. The competition between surface repulsive and attractive interactions of nanoparticles is reflected in the nature of the morphology and particle network in electrolytes, further affecting the ionic conductivity of electrolytes and diffusion coefficient of ions. The obvious decrease is observed in the AP-SiO₂-based system because of the severe agglomeration of nanoparticles. By contrast, the AM-SiO₂ and SU-SiO₂ form the regular particle network structure and accelerate the salt dissociation in electrolytes, thereby providing an effective ion transport pathway and more mobile ions for conduction, respectively. Consequently, the composite systems with AM-SiO₂ and SU-SiO₂ deliver remarkable enhancement in the ion transport properties.

Gelation, Liquid Crystalline Behavior, and Ionic Conductivity of Nanocomposite Ionogel Electrolytes Based On Attapulgite Nanorods

Anisotropic nanoparticles and their dispersions have attracted much attention because of their distinguished characteristics and promising applications. In this study, the novel liquid crystalline nanocomposite ionogel electrolyte materials based on anisotropic nanoparticles of attapulgite (ATP) have been prepared. The gelation, liquid crystalline (LC) behavior, thermal stability, and ionic conductivity were systematically investigated. Rheological, polarized optical microscopy (POM), and small-angle X-ray scattering (SAXS) measurements demonstrated that these liquid crystalline ionogels showed a two-step mechanism consisting of gelation and subsequent reorganization of the gel. Interestingly, the obtained ionogel electrolytes were very stable and LC gel structures were not destroyed even though the temperature was as high as 200 °C. Furthermore, these ionogels possessed outstanding thermal stability and the decomposition temperature exceeded 400 °C. Remarkably, the LC nanocomposite ionogel electrolytes exhibited high room temperature ionic conductivity and the value still exceeded 1.0 × 10^-3 S/cm even when the ATP concentration up to 30 wt %. These novel findings are very useful for the fabrication of high temperature resistant electrochemical devices and liquid crystalline nanocomposite materials.