(Digital) Ionic Conduction Mechanism and Design of Metal–Organic Framework Based Quasi-Solid-State Electrolytes

Recently, anionic metal–organic frameworks (MOFs) with superior ionic conductivity and Li + transference numbers have opened a new avenue in the development of quasi-solid-state electrolytes (QSSEs). Given the superior performance and the characterization challenges associated with transport property measurements, it is vitally important to understand the Li + transport and conduction mechanisms of this new prototype of QSSEs. In this presentation, we will discuss the theoretical and experimental investigation of two polyoxometalate (POM) -based MOFs, [(MnMo 6 ) 2 (TFPM)] imine and [(AlMo 6 ) 2 (TFPM)] imine , as QSSEs. Classical molecular dynamics coupled with quantum chemistry and grand canonical Monte Carlo are utilized to model the corresponding diffusion and ionic conduction in the two materials. Using different approximate levels of ion diffusion behavior, the primary ionic conduction mechanism was identified as solvent-assisted hopping (>77%), revealing the critical role of the solvent in MOF-based QSSEs. Detailed static and dynamic solvation structures were obtained to interpret Li + motion with high spatial and temporal resolution. We found that the local charge distribution on POM surface largely determines the interaction between Li + and the framework. Based on the prevalent mechanism of Li + motion, we propose a hypothesized MOF design with a non-interpenetrating structure that is expected to achieve 6–8 times better ionic conduction performance (1.6–1.7 mS cm −1 ) than the current state-of-the-art (0.19–0.35 mS cm −1 ), approaching the conductivity range of liquid electrolytes. Figure 1