Chemomechanics of ionically conductive ceramics for electrical energy conversion and storage

Abstract

Functional materials for energy conversion and storage exhibit strong coupling between electrochemistry and mechanics. For example, ceramics developed as electrodes for both solid oxide fuel cells and batteries exhibit cyclic volumetric expansion upon reversible ion transport. Such chemomechanical coupling is typically far from thermodynamic equilibrium, and thus is challenging to quantify experimentally and computationally. In situ measurements and atomistic simulations are under rapid development to explore how this coupling can be used to potentially improve both device performance and durability. Here, we review the commonalities of coupling between electrochemical and mechanical states in fuel cell and battery materials, illustrating with specific cases the progress in materials processing, in situ characterization, and computational modeling and simulation. We also highlight outstanding questions and opportunities in these applications -both to better understand the limiting mechanisms within the materials and to significantly advance the durability and predictability of device performance required for renewable energy conversion and storage.

Electro‐chemomechanical Contribution to Mechanical Actuation in Gd‐Doped Ceria Membranes

“…On this basis, we note that actuation is most likely achieved via an electrochemically driven phase transformation, rather than because of the change in stoichiometry of a single phase . This can be distinguished from the chemical expansion of ion‐conducting ceramics, or of polymers …”

“…Therefore, electrochemical oxygen exchange reactions at the interface with a titanium electrode is possible even at room temperature. These electrochemical reactions may induce electro‐chemomechanical (ECM) response, i.e., mechanical deformation induced by electrochemically driven changes in composition . Therefore, ECM and electrostrictive responses may superimpose.…”

Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries

“…24,26,27,33 Acoustic emission from electrochemical shock has also been directly recorded during charging and discharging. [28][29][30][31][32][34][35][36] Here, TXM was used to non-destructively generate 3D tomographs of the single particles at different states of charge, which we correlate with the electrochemical measurements. Individual NMC333 and NCA single particles having B10 mm diameter were charged at C/3 rate to 3.9 V, 4.1 V, and 4.5 V, respectively.…”

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

“…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.…”