Effect of Pore Filling on Properties of Nanocomposites LiClO(4)–MIL–101(Cr) with High Ionic Conductivity

Experimental data on nitrogen adsorption, pellets density and ionic conductivity of nanocomposite solid electrolytes (1−x)LiClO(4)–xMIL-101(Cr) were interpreted in frames of the model of the composite in which the lithium salt fills the pores of a metal-organic framework MIL-101(Cr). According to the model, the concentration of lithium salt located in the pores reaches a maximum at the concentration x = x(max) which is defined by a ratio of the molar volume of LiClO(4) and the total volume of accessible pores in the MIL-101(Cr) framework. The model allows one to describe the dependences of pore volume and pellet density on the concentration of MIL-101(Cr). Conductivity of the composites were successfully described by two separate mixing equations for concentration ranges x < x(max) and x > x(max). In the first concentration region x < x(max), the composite may be regarded as a mixture of LiClO(4) and MIL-101(Cr) with completely filled pores accessible for LiClO(4). At x > x(max), the total amount of lithium perchlorate is located in the pores of MIL-101(Cr) and occupies only part of the volume of the accessible pores. It was found that x(max) value determined from the concentration dependence of conductivity (x(max) = 0.06) is noticeably lower than the corresponding value estimated from adsorption data (x(max) = 0.085) indicating a practically complete filling the pores of MIL-101(Cr) in the composite pellets heated before conductivity measurements.