Nanocomposite Electrolytes with Fumed Silica and Hectorite Clay Networks: Passive versus Active Fillers

Abstract

The use of nanocomposites constitutes a versatile and robust approach in the development of novel electrolytes with tailored electrochemical and mechanical characteristics. In this study, we examine the morphology, rheology, and ion‐transport properties of two types of nanocomposite electrolyte gels, one consisting of branched silica nanoparticles and the other composed of hectorite clay. In the first system with hydrophobic (fumed) silica, oligomers of poly(ethylene oxide) (PEO), and lithium salt, the silica acts as a passive filler and does not participate in ion transport. The electrochemical properties are controlled by the salt–PEO electrolyte, allowing for ionic conductivities greater than 10–3 S cm–1 at ambient temperature. At sufficiently high concentrations, the silica forms an elastic gel possessing a large open network structure that provides for unimpeded ion mobility. In the second system composed of lithium‐exchanged hectorite filler, the nanoscale platelets serve as the anion. This active filler yields ionic conductivities in excess of 10–4 S cm–1 and lithium transference numbers approaching unity. Similar to fumed silica, the hectorite clay also forms an elastic gel network. However, the morphologies of the two systems are distinctively different both in terms of network structure and characteristic length scale. These morphological differences manifest themselves in different rheological responses with regard to gel modulus and yield stress.

Application of a composite polymer electrolyte based on montmorillonite in dye-sensitized solar cells

“…The addition of inorganic particles such as hectorite, 27,28 smectite, 29 fumed silica, 30,31 and montmorillonite clay (MMT) [32][33][34] provides both an increase in the ionic conductivity and an improvement in the mechanical properties. Electrolytes containing silica nanoparticles have also been used to assemble dye-sensitized solar cells, leading to remarkable performances.…”

Nanoporous hybrid electrolytes

“…In pursuit of such materials, several classes of electrolytes have been studied as replacements for conventional liquid electrolytes: polymers, [7][8][9][10][11] polymer composites, [12][13][14][15] hybrids, 16-18 gels, 19,20 ionic liquids, 21 and ceramics.…”

“…In pursuit of such materials, several classes of electrolytes have been studied as replacements for conventional liquid electrolytes: polymers, [7][8][9][10][11] polymer composites, [12][13][14][15] hybrids, [16][17][18] gels, 19,20 ionic liquids, 21 and ceramics. 22 In many cases, mechanical integrity of the electrolyte comes at a cost: namely, a large loss in ionic conductivity, which places undesirable limits on the charge/discharge rate of the cell.…”

“…Liquid and particulate plasticizers have been used with some success in circumventing this constraint in composite and gel polymer electrolytes. 4,15,19,23 With a mechanically strong framework in place such as a polymer or ceramic, the liquid plasticizer serves as a freely diffusing ionic conduction medium that provides ionic conductivities near that of a pure liquid electrolyte. If a liquid plasticizer with good thermal and electrochemical properties is utilized, safety concerns are reduced.…”

Electrolytes for high-energy lithium batteries

“…Ionic liquid-based gel polymer electrolytes are now widely studied as a possible solution to some of these issues (Rupp et al 2008;Fuller et al 1998;Nakagawa et al 2003;Cheng et al 2007;Liao et al 2010); PEO-based gel polymer electrolytes have also been explored, by swelling a high molecular weight PEO matrix with PEG oligomers (Borghini et al 1996). Ceramic-liquid electrolytes ''Soggy sand'' electrolytes are created by doping a liquid electrolyte with ceramic nanoparticles (Bhattacharyya et al 2004;Bhattacharyya 2009, 2010;Walls et al 2003). At a given particle volume fraction a onset ( 0.01, a percolating particle network forms in the system (Fig.…”