The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes

Abstract

Understanding 'electro-chemo-mechanics' in oxygen ion conducting membranes represents a foundational step towards new energy devices such as micro fuel cells and oxygen or fuel separation membranes. For ionic transport in macro crystalline electrolytes, doping is conventionally used to affect oxygen ionic association/migration energies. Recently, tuning ionic transport in films through lattice strain conveyed by substrates or heterostructures has generated much interest. However, reliable manipulation of strain states to twist the ionic conduction in real micro energy devices remains intractable. Here, we demonstrate that the oxygen ionic conductivity clearly correlates with the compressive strain energy acting on the near order of the electrolyte lattices by comparing thin-film ceria-based membrane devices against substrate-supported flat structures. It is possible to capitalize on this phenomenon with a smart choice of strain patterns achieved through microelectrode design. We highlight the importance of electro-chemo-mechanics in the electrolyte material for the next generation of solid-state energy conversion microdevices.

When two become one: An insight into 2D conductive oxide interfaces

“…In one case, it was reported a 7 orders of ionic conductivity enhancement in YSZ and it has been widely proved to be induced by combination of electronic and ionic conductivity [103]. On the other hand, theoretical calculation and simulations suggest that interfacial tensile strain is beneficial and can improve the oxygen ionic conductivity through changes in the hopping sites and frequencies, due to a substantial variation of the enthalpies of oxygen-vacancy migration and association [104]. The key factors for enabling fast oxygen transport in strained lattice have been thus discussed in a growing number of publications describing the combined electro-chemo-mechanic effects on oxygen ion conductivity both on biaxial and isotropic strain [104,105].…”

“…On the other hand, theoretical calculation and simulations suggest that interfacial tensile strain is beneficial and can improve the oxygen ionic conductivity through changes in the hopping sites and frequencies, due to a substantial variation of the enthalpies of oxygen-vacancy migration and association [104]. The key factors for enabling fast oxygen transport in strained lattice have been thus discussed in a growing number of publications describing the combined electro-chemo-mechanic effects on oxygen ion conductivity both on biaxial and isotropic strain [104,105]. Particularly, Sousa et al have employed static lattice simulations to examine the effect of isotropic and biaxial strain on the migration thermodynamics of oxygen vacancies in fluorite-structured ceria.…”

An Interdisciplinary View of Interfaces: Perspectives Regarding Emergent Phase Formation

“…This type of strain is typically encountered in thin films specimens constrained by a substrate. Experimental works have verified the impact of strain on the ionic conductivity of ceria and zirconia based thin films [24,25].…”

Microstructure design for fast oxygen conduction

“…Other recent strategies, such as free standing buckled membranes that have been recently shown to decrease oxygen migration barriers, are promising engineering methods to gain control over oxygen conductivity. 137 Gaining control over the oxygen vacancy concentration and distribution is also important for the overall design of layered oxide materials. Such strain-controlled thermodynamics coupled with kinetics of oxygen vacancies would be particularly beneficial for fast ion conductors, as both activation and formation energies would be manipulated.…”