Ionic conduction in the solid state

Abstract

Solid state ionic conductors are important from an industrial viewpoint. A variety of such conductors have been found. In order to understand the reasons for high ionic conductivity in these solids, there have been a number of experimental, theoretical and computational studies in the literature. We provide here a survey of these investigations with focus on what is known and elaborate on issues that still remain unresolved. Conductivity depends on a number of factors such as presence of interstitial sites, ion size, temperature, crystal structure etc. We discuss the recent results from atomistic computer simulations on the dependence of conductivity in NASICONs as a function of composition, temperature, phase change and cation among others. A new potential for modelling of NASICON structure that has been proposed is also discussed.

Elaboration of Amorphous-Clay Hybrid: (Al<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>·1/2Li<sub>2</sub>O) Designed as a Single Ion Conducting Solid Electrolyte for Li-Ion Batteries

“…According to these experimental results, we deduce that the disordered hybrid bears easier motion than the ordered one. We conclude that contribution of disorder and defects in the hybrid framework are responsible for the motion of charge carriers; this result is in agreement with the previous publication of Kumar & Yashonath [2].…”

“…Applying the simple logic that "smaller ions diffuse faster" and since cations have smaller ionic radii than anions, the majority of superionic solids discovered are cation conductors [2]. Another factor that influences the diffusivity of ion is the magnitude of charge it carries.…”

“…Another factor that influences the diffusivity of ion is the magnitude of charge it carries. When the charge of an ion is large, it is likely to be confined to its site by stronger Coulombic attraction of its neighboring ions (which are of opposite charge) [2]. That is why the predominant current conducting species in known superionic solids are monovalent cations [2].…”

“…Besides, H + and OH − ions of the intercalated water molecules are eliminated due to the dehydration starting from 373 K as demonstrated by TG analysis [15]. Furthermore, Li + is known as an excellent current carrying ion in superionic solids motivated by its small ionic radius of 0.076 nm, lower weight and ease of motion [2] but Cl − anion appears to be rather less mobile than the cation due to its great ionic radius equals to 0.181 nm [2]. To conclude, Li + is the predominant current carrier in Li-hybrid conductor at low temperatures.…”

“…Their advantages include longer life, high energy density and no possibility of leak, etc. They are suitable in compact power batteries used in pace-makers, mobile telephones and laptops [2].…”