State-independent ionic conductivity.

Liquids lend themselves to high ionic conductivities because of their molecular-level positional and orientational disorder, which enables the free movement of ions. However, there is an unavoidable steep drop in ionic conductivity upon phase transition from a fluid state to the more ordered solid state. Here, we describe organic salts that maintain the same ionic conductivity mechanism across transitions between three states of matter, from an initial isotropic liquid to a liquid crystalline state and then to a crystalline solid. We achieved this property by minimizing the ion-pairing interactions between mobile ions and highly diffuse counterions that assemble in a stepwise manner to preserve conformational flexibility across phase transitions. This state-independent ionic conductivity opens up opportunities to exploit liquid-like ionic conductivity in organic solids. Editor's summary: The transition from a liquid to a solid state generally introduces a discontinuity in ionic conductivity. In the liquid phase, the ionic conductivity follows the Arrhenius relation. However, a sharp phase change such as freezing will cause a drop in ionic conductivity at the transition temperature because the ions are much less mobile in a solid than in a liquid. Barclay et al. designed an organic electrolyte based on cyclopropenium salts that does not show a sharp drop in the ionic conductivity at the liquid-to-solid phase change boundary. This attribute is achieved by bridging the liquid and solid phase regions by a liquid crystal phase region. Key aspects are the weak cation-anion interactions and considerable structural freedom. —Marc S. Lavine [ABSTRACT FROM AUTHOR]