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The ever-increasing demand for flexible and portable electronics has stimulated research and development in building advanced electrochemical energy devices which are lightweight, ultrathin, small in size, bendable, foldable, knittable, wearable, and/or stretchable. In such flexible and portable devices, semi-solid/solid electrolytes besides anodes and cathodes are the necessary components determining the energy/power performances. By serving as the ion transport channels, such semi-solid/solid electrolytes may be beneficial to resolving the issues of leakage, electrode corrosion, and metal electrode dendrite growth. In this paper, the fundamentals of semi-solid/solid electrolytes (e.g., chemical composition, ionic conductivity, electrochemical window, mechanical strength, thermal stability, and other attractive features), the electrode-electrolyte interfacial properties, and their relationships with the performance of various energy devices (e.g., supercapacitors, secondary ion batteries, metal-sulfur batteries, and metal-air batteries) are comprehensively reviewed in terms of materials synthesis and/or characterization, functional mechanisms, and device assembling for performance validation. The most recent advancements in improving the performance of electrochemical energy devices are summarized with focuses on analyzing the existing technical challenges (e.g., solid electrolyte interphase formation, metal electrode dendrite growth, polysulfide shuttle issue, electrolyte instability in half-open battery structure) and the strategies for overcoming these challenges through modification of semi-solid/solid electrolyte materials. Several possible directions for future research and development are proposed for going beyond existing technological bottlenecks and achieving desirable flexible and portable electrochemical energy devices to fulfill their practical applications. It is expected that this review may provide the readers with a comprehensive cross-technology understanding of the semi-solid/solid electrolytes for facilitating their current and future researches on the flexible and portable electrochemical energy devices.

Ion exchange membranes (IEMs) play important roles in energy generation and storage field, such as fuel cell, flow battery, however, a major barrier in the way of large-scale application is the high cost of membranes (e.g., Nafion membranes price generally exceeds USD$ 200 m -2 ). The membrane-less technology is one of the promising approaches to solve the problem and thus has attracted much attention and been explored in a variety of research paths. This review introduces one of the representative membrane-less battery types, Biphasic membrane-less redox batteries that eliminate the IEMs according to the principle of solvent immiscibility and realizes the phase splitting in a thermodynamically stable state. It is systematically classified and summarizes their performances as well as the problems they are suffering from, and then several effective solutions are proposed based on the modification of electrodes and electrolytes. Finally, special attention is given to the challenges and prospects of Biphasic membrane-less redox batteries, which could contribute to the development of membrane-less batteries., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The catalyst‐reconstruction makes it challenging to clarify the practical active sites and unveil the actual reaction mechanism during the CO2 electroreduction reaction (CO2RR). However, currently the impact of the electrolyte microenvironment in which the electrolyte is in contact with the catalyst is overlooked and might induce a chemical evolution, thus confusing the reconstruction process and mechanism. In this work, the carbonate adsorption properties of metal oxides were investigated, and the mechanism of how the electrolyte carbonate affect the chemical evolution of catalysts were discussed. Notably, Bi2O3 with weak carbonate adsorption underwent a chemical reconstruction to form the Bi2O2CO3/Bi2O3 heterostructure. Furthermore, in situ and ex situ characterizations unveiled the formation mechanism of the heterostructure. The in situ formed Bi2O2CO3/Bi2O3 heterostructure with strong electron interaction served as the highly active structure for CO2RR, achieving a formate Faradaic efficiency of 98.1 % at −0.8 Vvs RHE. Theoretical calculations demonstrate that the significantly tuned p‐orbit electrons of the Bi sites in Bi2O2CO3/Bi2O3 optimized the adsorption of the intermediate and lowered the energy barrier for the formation of *OCHO. This work elucidates the mechanism of electrolyte microenvironment for affecting catalyst reconstruction, which contributes to the understanding of reconstruction process and clarification of the actual catalytic structure. [ABSTRACT FROM AUTHOR]

The development of flexible zinc–air battery (ZAB) is highly desirable in achieving superior and stable electrochemical/mechanical properties. Herein, we developed a Zn‐coated foam anode with three‐dimensional (3D) architecture, obtained by electroplating Zn on Cu foam substrate. The compact outer surface and sufficient amount of metallic Zn could be controlled accurately by selecting appropriate porous substrate and electroplating time on Cu foam. Moreover, adding tetraethylammonium hydroxide (TEAOH) to conventional polyvinyl alcohol (PVA)–KOH hydrogel electrolyte effectively improved the water retention of the semi‐solid electrolyte with stable ionic conductivity. The electrolyte precursor fluid was poured on the uneven outer surface of Zn‐coated foam anode and then frozen crosslinked to increase contact between the 3D anode and the electrolyte. A flexible semi‐solid‐state ZAB based on the 3D Zn‐coated foam anode and the hydrogel electrolyte was assembled and exhibited good discharge performance, high energy density (586.5 Wh kgZn−1) and long cycling life. Benefiting from the flexibility of all components, the resultant ZAB performed stable charge and discharge under bending conditions, indicating its promising potential application for flexible and portable energy storage devices. [ABSTRACT FROM AUTHOR]

Electrolytes have been identified as some of the most influential components in the performance of electrochemical supercapacitors (ESs), which include: electrical double-layer capacitors, pseudocapacitors and hybrid supercapacitors. This paper reviews recent progress in the research and development of ES electrolytes. The electrolytes are classified into several categories, including: aqueous, organic, ionic liquids, solid-state or quasi-solid-state, as well as redox-active electrolytes. Effects of electrolyte properties on ES performance are discussed in detail. The principles and methods of designing and optimizing electrolytes for ES performance and application are highlighted through a comprehensive analysis of the literature. Interaction among the electrolytes, electro-active materials and inactive components (current collectors, binders, and separators) is discussed. The challenges in producing high-performing electrolytes are analyzed. Several possible research directions to overcome these challenges are proposed for future efforts, with the main aim of improving ESs' energy density without sacrificing existing advantages (e.g., a high power density and a long cycle-life) (507 references). [ABSTRACT FROM AUTHOR]

Keywords: characterization methods; electrolytes; in situ; lithium-ion batteries; silicon-based anodes The development of characterization methods is anticipated to greatly promote the upgrade of high-performance lithium-ion batteries (LIB) based on silicon (Si)-based anodes. Characterization methods, electrolytes, in situ, lithium-ion batteries, silicon-based anodes. [Extracted from the article]

With the remarkably large theoretical specific capacity of silicon (Si), Si‐based rechargeable lithium‐ion batteries (LIBs) have attracted great interest, as they are expected to meet the growing demand for large‐scale energy storage devices, electric vehicles, and portable electronic devices with high energy density. However, the Si‐based LIB faces great challenges due to the cyclic volume changes induced by Si, which lead to considerable capacity fading. To facilitate the use of high‐performance LIBs enabled by Si‐based anodes, understanding the fading mechanism is necessary. In this regard, various advanced characterization methods have been developed to reveal the fading mechanism and to develop a modification strategy associated with compositional and structural evolution. In this review, the general understanding of the fading mechanism and the technical specifications of Si‐based LIBs are discussed. The recent progress in advanced characterization methods for Si‐based LIBs is summarized with respect to the achievements in compositional and structural interpretation. Several possible future research directions for Si‐based LIBs and the expected development trends in relevant characterization methods are also discussed. [ABSTRACT FROM AUTHOR]

Review: 507 refs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pre-adsorption of Cl− on Fe site of dual-atom Fe/Se-NC (Fe/Se-NC-Cl) would enhance the oxygenophilic property of the catalysts. • The Fe/Se-NC-Cl displays high Cl−-corrosion resistance and ORR activity in seawater electrolyte. • Fe/Se-NC-Cl display outstanding ORR on-set and half-wave potentials of 0.88 and 0.75 V, respectively. • Fe/Se-NC-Cl-based seawater battery shows a recorded peak power density of 94 mW cm−2. Seawater batteries (SWBs) are promising energy conversion systems that directly utilize seawater as an electrolyte for converting chemical energy into electricity. The oxygen reduction reaction (ORR) occurs by consuming dissolved oxygen on the cathode electrocatalysts for discharging. However, chloride ions (Cl−) poison the surface catalytic sites of electrocatalysts, and the low dissolved oxygen concentration critically limits the ORR reaction kinetics, reducing the discharging power density and working life. In this work, we designed and synthesized the Fe/Se-NC electrocatalyst using a facile solution chemical process. Theoretical calculation and experimental results suggest that the incorporation of Se in Fe/Se-NC can significantly enhance the adsorption energy of Cl− on one side of the Fe site (designated as Fe/Se-NC-Cl) and result in the enhanced oxygenophilic property of Fe/Se-NC on another side of the Fe site. This simultaneously enhances Cl-corrosion resistance and ORR activity. The Fe/Se-NC-Cl electrocatalysts display outstanding ORR onset and half-wave potentials of 0.88 and 0.75 V, respectively, which rank at the top among ORR electrocatalysts in natural seawater electrolyte. The SWBs using Fe/Se-NC-Cl as cathodes show a high peak power density of 94 mW cm−2, stability of more than 450 h, and discharge capacity of 583 Wh kg−1 at a current density of 5 mA cm−2 in natural seawater electrolyte. The developed SWB package can efficiently power household appliances with a rated power of up to 50 W. [ABSTRACT FROM AUTHOR]

Abstract: Submicron-sized cuprous oxide crystallites was prepared by electrodeposition, and polyethylene glycol (PEG) was introduced to improve the dispersity of crystallites. Transmission electron microscopy (TEM) and scanning electronic microscopy (SEM) were applied to characterize its crystal structure and morphology. Based on the analysis, it was found that PEG can affect the growth mode of cuprous oxide crystallites, which improves of the dispersity of the crystallites. The growth of cuprous oxide crystallites without PEG presents obvious aggregation dominant, while diffusion becomes the dominant mechanism when PEG is introduced into the electrolyte. The photo transmission character of cuprous oxide crystallites was measured by UV–vis spectrophotometer, and the calculated band gap energy of which is approximately 2.17eV. The photoelectrochemical property of the crystallites was also characterized with the current–potential responses to a linear potentiodynamic scan under chopped illumination, and it is found that the photocurrent of the cuprous oxide crystallites electrodeposited with PEG is obviously larger than the one without PEG. [Copyright &y& Elsevier]