Electrochemical Investigations of Polyethylene Glycol‐Based “Soggy Sand” Electrolytes – From the Local Mechanism to the Overall Conduction

Abstract

Using the example of SiO 2 dispersions in LiClO 4 /polyethylene glycol electrolytes, the conduction mechanism of "soggy sand" electrolytes is discussed. The study is essentially based on zeta potential, impedance and transference number measurements as well as on modeling. All the results can be explained by anion adsorption by the oxide particles and increased concentration of free Li + in the double layer. The initially colloidal dispersion quickly forms fractal networks by cluster-cluster aggregation. Once they percolate, an interfacially dominated Li + conductance is observed. The subsequent coarsening of the network is self-decelerating leading to a steady state conductivity that is, for low volume fractions, enhanced compared to SiO 2 free electrolytes. At higher values, blocking and inhomogeneity effects (e.g., salt trapping) lead to decreased values of the overall conductivity.

Soggy-sand effects in liquid composite electrolytes with mesoporous materials as fillers

“…Interestingly, the conductivity is slightly higher for the cooling cycle. As opposed to previous observations in other composite electrolytes, 27,43 coarsening caused by particle surface diffusion and reversible bonding of cluster parts 43 does not play an important role in these systems. This might be caused by a hindered particle "sliding" along the surface due to their porosity and the resulting interparticle contact area.…”

Smart Multifunctional Fluids for Lithium Ion Batteries: Enhanced Rate Performance and Intrinsic Mechanical Protection

“…The composite conductivity exhibits typical percolation behaviour, which is expected for a composite with enhanced interfacial conductivity41, i.e., low conductivity at low oxide content, which increases to a marked maximum, before decreasing at higher weight fractions. Similar phenomena have been reported by Maier's group2942. The conductivity enhancment generated by the addition of fumed silica is likely to be attributable to an adsorption of the anion (PF 6 ) by the acidic oxide and the subsequent break-up of the ion pair, thereby increasing the Li + concentration in the space charge layer surrounding the oxide particles.…”

Shear Thickening Electrolytes for High Impact Resistant Batteries

“…This decrease in ionic conductivity is consistent with dilution of the electrolyte by an inert agent and would not affect cell performance for high-capacity batteries operated at low charge/discharge rates. Furthermore, conductivity could be increased with the addition of functional polymers, different anions, and the exploitation of “soggy-sand”-type effects. , …”