Energy conversion and storage with high efficiency are among the most important subjects for achieving a carbon-neutral society from the perspectives of environmental conservation and energy security. In this review, solid oxide cells using LaGaO₃-based perovskite oxides as electrolytes are described, together with their reversible operation in electrolysis and fuel-cell modes. Since tight gas sealing is essential for achieving high efficiency, a tubular cell design was adopted, in which a LaGaO₃-based oxide film prepared by dip coating and co-sintering was used as the electrolyte. Despite the tubular design, the prepared cell exhibited high performance in both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes, with high reversibility between the two operating modes. The CO₂ electrolysis performance of this tubular-type cell is also described. In addition, the application of a highly concentrated ion-conducting aqueous electrolyte combined with tetraglyme, referred to as a hybrid aqueous electrolyte, is introduced, together with its application to a dual-ion battery.

Porosity in anodic aluminum oxide (AAO) is one of the key structural features in the research and development of AAO-based nanostructured devices. Although surface image analysis (SIA) using scanning electron microscopy is commonly used to measure porosity, it tends to underestimate this value because of inherent systematic errors and transient surface structures. In addition, the tendency of pores to adopt a tapered shape during high-throughput, high-temperature anodization requires accurate structural measurements. In this study, we derived a theoretical formula for calculating the effective surface porosity P_top. We assessed its consistency by quantitatively comparing the apparent surface porosity from SIA and the pore-bottom porosity P_bottom measured using the pore-filling method. The formula proposed in this study enables a direct comparison of P_top and P_bottom on a unified scale. This achievement contributes to the efficient fabrication of samples through high-temperature anodization and improves the structural design of AAO-based research and application devices.

Rheo-impedance is the joint use of a rheological measurement and an electrical, electrochemical, or dielectric measurement to follow how a soft material or complex fluid reorganizes as it is processed or as it changes state. The two answer different questions about the same sample: rheology reports how the material flows and how stiff or elastic it is, while impedance, conductivity, and dielectric data report how well charge moves through it and what is happening at its interfaces. Because the mechanical and the electrical responses often depend on different parts of the microstructure, and need not change at the same moment, measuring both can separate states that look identical to either method alone. In this review, “rheo-impedance” is used as an organizing term rather than the name of a single standardized technique. The literature is grouped into three configurations—simultaneous, separate-but-linked, and correlation-based—and five material classes: carbon-black and conductive-colloid suspensions, lithium-ion battery slurries, polymer-electrolyte fuel-cell catalyst inks, gelation and stimuli-responsive systems, and drying, curing, and sintering. Four observations recur across these systems: the mechanical and electrical changes may be linked to the same process yet appear at different stages; a stiffer structure does not necessarily carry charge better; the structure present under flow is not always the one retained after processing; and both agreement and disagreement between the two responses can be informative. Throughout, we try to separate what has been shown experimentally from what is still system-dependent interpretation or future prospect. The main open problems are the ambiguity of equivalent-circuit interpretation, the limited transfer of descriptors between the flowing and the finished state, and the absence of standard geometries, frequency windows, and reporting conventions.

The transition from laboratory-scale experiments to industrial-scale production frequently exposes fundamental challenges related to process similarity. In the context of silicon porosification, achieving consistent results during scale-up requires maintaining thermal, kinematic, geometric, and electrochemical (current/potential) similarities. On the example of two stages of upscaling, this work aims to elucidate the principal scaling effects that arise during the electrochemical porosification of silicon and to outline strategies for mitigating them. Through a series of representative examples, the paper highlights how process parameters, reactor geometry, and operating modes influence the resulting pore architecture and uniformity. A novel inline etching tool is presented where the wafers pass over tanks of alternating polarity. This approach has the great benefit that it does not need a backside contact; however, the alternating tank coverage leads to current density fluctuations under potentiostatic operation. A simple COMSOL simulation (Finite Element Method) of the series resistance network of the system is able to explain the fluctuations qualitatively as well as quantitatively. On this basis, design rules for the next-generation inline etching tool are suggested that would reduce the current density fluctuations from about 50 % to less than 10 %.

Sodium-ion batteries (SIBs) are promising next-generation energy-storage systems, yet their low energy density remains a major challenge. An effective strategy to utilizing low-potential anodes is tuning their electrode potentials with respective to an electrolyte potential window. Herein we propose a molecular framework design of electrolyte solvents to rationally tune sodium electrode potential (E_Na). Extending the alkyl chains of phosphate ester solvents upshifted E_Na by up to 0.32 V (tripropyl phosphate vs. trimethyl phosphate) despite similar donor numbers, indicating a dominant steric effect to weaken the Na⁺ solvation. In contrast, cyclic crown ether 15-crown-5 downshifted E_Na by 0.16 V compared to its linear counterpart (tetraglyme) via the formation of a more stable chelate coordination. Furthermore, the magnitude of these steric/structural effects depended strongly on the cation species, leading to large variations in the Na-Li electrode potential difference (ΔE_Na–Li), from 0.53 V in tripropyl phosphate to 0.10 V in 18-crown-6. Machine-learning-based molecular dynamics simulations revealed that the changes in the cation solvation structure, induced by the solvent molecular framework engineering, are responsible for the observed potential shifts. These findings establish solvent molecular framework engineering as a versatile strategy to tune electrode potentials in battery electrolytes.