Rethinking the Design of Ionic Conductors Using Meyer–Neldel–Conductivity Plot
Yirong Gao, Nana Li, Yifan Wu, Wenge Yang, Shou‐Hang Bo
Abstract
Abstract From the discovery of the first fast ionic conductor silver iodide in the early 20th century to the recent discovery of lithium fast ionic conductors with ionic conductivities surpassing those of liquid electrolytes, high ionic conductivity σ has often been associated with low activation energy E a following the Arrhenius equation. However, the Meyer–Neldel rule (MNR) indicates that the E a and prefactor σ 0 are correlated, suggesting the relation between the E a and σ is, in fact, complex. In this perspective, the use of the Meyer–Neldel–conductivity plot and a critical descriptor, Meyer–Neldel energy Δ 0 , to guide the search for fast ionic conductors is proposed. Reported lithium, sodium, and magnesium ionic conductors are categorized into three types, depending on the relative magnitude between the Δ 0 and thermal energy ( k B T ) at the application temperature. The process by which σ can be optimized by tuning E a for these types of ionic conductors is elaborated. This principle can be widely applied to all ionic conductors that obey the MNR at any application temperature. Furthermore, a pressure‐tuning approach to measure the Δ 0 rapidly is developed. These findings establish a previously missing step for designing new ionic conductors with improved ionic conductivity.