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Mixed ionic–electronic conductors are widely used as electroactive materials in energy applications. The contact of a mixed conductor with another phase plays a crucial role in charge storage and transport in energy devices. However, the interfacial chemistry at the heterojunctions comprising mixed conductors and its interplay with the bulk chemistry remains imperative yet inadequately understood. This study addresses the fundamentals of space charge effects by exploring the equilibrium situations for contacts consisting of mixed conductors. From the perspective of defect chemistry, and by unifying the bulk and interfacial conditions with the electrochemical potential, our treatment allows for predicting the built-in potential at heterojunctions, profiling the space charge distributions, and evaluating the resulting interfacial charge storage and transport. The treatment can be related to experimental characterization, including coulometric titration, conductivity, and capacitance measurements at electrochemical interfaces in all-solid-state batteries. Besides, our treatment also highlights the significance of size and doping effects in nanocrystalline electrodes. This work provides a comprehensive framework for understanding and engineering the heterojunctions in electrochemical devices. [ABSTRACT FROM AUTHOR]

Prediction from the dual-phase nature of superionic conductors-both solid and liquid-like-is that mobile ions in the material may experience reversible extraction-reinsertion by an external electric field. However, this type of pseudoelectroelasticity has not been confirmed in situ, and no details on the microscopic mechanism are known. Here, we in situ monitor the pseudoelectroelasticity of monocrystalline Cu2S nanowires (NWs) using transmission electron microscopy (TEM). Specifically, we reveal the atomic scale details including phase transformation, migration and redox reactions of Cu+ ions, nucleation, growth, as well as spontaneous shrinking of Cu protrusion. Caterpillar-diffusion-dominated deformation is confirmed by the high-resolution transmission electron microscopy (HRTEM) observation and  ab initio calculation, which can be driven by either an external electric field or chemical potential difference. The observed spring-like behavior was creatively adopted for electric nanoactuators. Our findings are crucial to elucidate the mechanism of pseudoelectroelasticity and could potentially stimulate in-depth research into electrochemical and nanoelectromechanical systems.

Mixed conductors--single phases that conduct electronically and ionically--enable stoichiometric variations in a material and, therefore, mass storage and redistribution, for example, in battery electrodes. We have considered how such properties may be achieved synergistically in solid two-phase systems, forming artificial mixed conductors. Previously investigated composites suffered from poor kinetics and did not allow for a clear determination of such stoichiometric variations. Here we show, using electrochemical and chemical methods, that a melt-processed composite of the 'super-ionic' conductor RbAg.sub.4I.sub.5 and the electronic conductor graphite exhibits both a remarkable silver excess and a silver deficiency, similar to those found in single-phase mixed conductors, even though such behaviour is not possible in the individual phases. Furthermore, the kinetics of silver uptake and release is very fast. Evaluating the upper limit of the relaxation time set by interfacial ambipolar diffusion reveals chemical diffusion coefficients that are even higher than those achieved for sodium chloride in bulk liquid water. These results could potentially stimulate systematic research into powerful, even mesoscopic, artificial mixed conductors. An artificial composite of the super-ionic conductor RbAg.sub.4I.sub.5 and the electronic conductor graphite exhibits extremely fast diffusion of silver ions at the interface between the two materials, generating both silver-excess and silver-deficient sites. Superfast ion diffusion in mixed conductors Materials that conduct both electrons and ions are important technologically for use in electrodes, permeation membranes, sensors and catalysts. They often consist of two or more components in a composite, with each mode of conduction catered for separately. This paper shows that a composite of the 'super-ionic' conductor rubidium silver iodide (RbAg.sub.4I.sub.5) and the electronic conductor graphite exhibits extremely fast diffusion of silver ions at the interface between the two materials, generating both a silver excess and a silver deficiency, analogous to single-phase mixed conductors, even though such behaviour is not possible in the individual phases., Author(s): Chia-Chin Chen [sup.1] , Lijun Fu [sup.1] , Joachim Maier [sup.1] Author Affiliations: (1) Max Planck Institute for Solid State Research, Heisenbergstraße 1, Stuttgart, Germany Main Mixed conductors form [...]

Composite cathodes consisting of a LiNi0.8Co0.1Mn0.1O2 (NCM) cathode and brittle Li3InCl6 (LIC) solid‐state electrolyte (SSE) are assessed for all‐solid‐state Li‐ion battery (ASSLIB) applications under a low stacking pressure (coin‐cell configuration: ≈2.0 MPa). Herein, an investigation is conducted to understand how the internal particle morphologies of the polycrystal (PC‐)/single‐crystal (SC‐) NCM cathode materials affect the internal cracking within the composite electrodes and thereby electrode performance. Extensive debonding between NCM and LIC takes place even at a very low current density (0.03C) with high voltage (4.4 V), but substantially narrower/shorter debonding gaps are observed for SC‐NCM as compared with PC‐NCM (wider/lengthier) due to their different particle sizes. High current rates (e.g., 0.1C) bring about greater strain rates in PC‐NCM particles, resulting in widespread microcracking along the grain boundaries between primary particles and consequently creating "dead zones" that are isolated from the ionic and electronic conduction pathways. Although SC‐NCM shows microcracking within the agglomerates, individual NCM crystals remain in close contact with the SSEs because of noticeably fewer grains in the agglomerations than in the PC‐NCM secondary particles. A low‐pressure SC‐NCM ASSLIB is demonstrated with good cycle stability comparable with that of a liquid‐electrolyte cell even under stressful currents. [ABSTRACT FROM AUTHOR]

Author(s): Chia-Chin Chen; Lijun Fu; Joachim Maier Nature 536, 159164 (2016); doi:10.1038/nature19078 In the Abstract of this Letter, upper limit of the relaxation time was, in the course of condensing [...]

The discrete model of space charge zones in solids reveals and remedies a variety of problems with the classic continuous Gouy–Chapman solution that occur for pronounced space charge potentials. Besides inherent problems of internal consistency, it is essentially the extremely steep profile close to the interface which makes this continuum approach questionable. Not only is quasi-1D discrete modeling a sensible approach for large space charge effects, it can also favorably be combined with the continuum description. A particularly useful application is the explicit implementation of crystallographic details and non-idealities close to the interface. This enables us to consider elastic, structural or saturation effects as well as permittivity variations in a simple but realistic way. We address details of the charge carrier profiles, but also overall properties such as space charge capacitance and space charge resistance. In the latter case the difference in the total charge (at identical concentration) is of importance, in the first case it is the inherent difference in the centroid of charge (at identical total charge) that is remarkable. The model is equally applicable for ionic charge carriers and small polarons. [ABSTRACT FROM AUTHOR]

The oxide formation on the surface of the molten metal jet was shown to have a drastic effect on the droplet formation process according to the description of some publication. Thus, the main objective of this research is to investigate the influence of oxygen concentration on the breakup and the monosized droplets generation of molten metal jet (Sn63 Pb37 alloy). The breakup phenomena of molten metal jet can be approximately divided into three regimes. They are 'breakup regime 'for oxygen concentration below [C.sub.1], 'transition regime' for oxygen concentration between [C.sub.1] and [C.sub.2], and 'breakup failing regime 'for oxygen concentration beyond [C.sub.2], respectively.