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Networks of inorganic particles (here SiO 2 ) formed within organic liquids play an important role in science. Recently they have been considered as 'soggy sand' electrolytes for Li-based batteries with a fascinating combination of mechanical and electrical properties. In this communication we model formation and stability of the networks by Cluster-Cluster Aggregation followed by coarsening on a different time scale. The comparison of computer simulations based on our model with experimental results obtained for LiClO 4 containing polyethylene glycol reveals (i) that the percolation threshold for interfacial conductivity is very small, (ii) that the networks once formed coarsen with a time constant that is roughly independent of volume fraction and size-to a denser aggregate which then stays stable under operating condition. (iii) Trapping of the conducting solvent at high packing is also revealed.Coherent networks of solids in liquids play an important role in colloid chemistry and physics and have a broad range of technological applications. Perhaps the most popular examples are dispersion paints that consist of inorganic particles dispersed in appropriate liquids. When a shear stress is applied, the network of the particles breaks up, and as a result the overall viscosity decreases. This thixotropy is beneficial for the process of painting. Brushing exerts shear stress and the resulting thinning facilitates applying the paint. Other examples are gels in which-unlike sols-colloidal particles form percolating networks.Here we will focus on the recently discovered ''soggy sand'' electrolytes in which by admixing fine insulating particles to salt containing liquids the overall ionic conductivity is pronouncedly increased.

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.

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