Table of Content

20 June 2022, Volume 5 Issue 2

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Electrospun Materials for Batteries Moving Beyond Lithium-Ion Technologies

Jie Wang, Zhenzhu Wang, Jiangfeng Ni, Liang Li

2022, 5(2):  211-241.  doi:10.1007/s41918-021-00103-9

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Innovation and optimization have shifted battery technologies beyond the use of lithium ions and fostered the demand for enhanced materials, which are vital factors determining the energy, power, durability, and safety of systems. Current battery materials vary in their sizes, shapes, and morphology, and these have yet to meet the performance standards necessary to prevent deterioration in regard to the efficiency and reliability of beyond-lithium technologies. As a versatile and feasible technique for producing ultrathin fibers, electrospinning has been extensively developed to fabricate and engineer nanofibers of functional materials for battery applications. In this review, the basic concepts and characteristics of beyond-lithium batteries are expounded, and the fundamentals of electrospinning are reviewed. The aim is to provide a guide to researchers going into this field. Focuses are placed on how electrospinning can address some of the key technical challenges facing beyond-lithium technologies. We hope the knowledge presented in this work will stimulate the design of electrospun materials for future battery applications.



Prussian Blue Analogues as Electrodes for Aqueous Monovalent Ion Batteries

Shen Qiu, Yunkai Xu, Xianyong Wu, Xiulei Ji

2022, 5(2):  242-262.  doi:10.1007/s41918-020-00088-x

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Aqueous batteries have engendered increasing attention as promising solutions for stationary energy storage due to their potentially low cost and innate safety. In various aqueous battery systems, Prussian blue analogues (PBAs) represent a class of promising electrode materials with fascinating electrochemical performance, owing to their large open frameworks, abundant ion insertion sites, and facile preparation. To date, PBAs have shown substantial progress towards storage of alkali metal ions (Li⁺, Na⁺, and K⁺), H⁺, and NH⁴⁺ in aqueous electrolytes, which, however, has yet not been specifically summarized. This review selects some representative research to introduce the progress of PBAs in these battery systems and aims to discuss the crucial role of ionic charge carrier in affecting the overall electrode performance. Besides, some critical knowledge gaps and challenges of PBA materials have been pointed out for future development.



Perovskite Cathode Materials for Low-Temperature Solid Oxide Fuel Cells: Fundamentals to Optimization

Zhiheng Li, Mengran Li, Zhonghua Zhu

2022, 5(2):  263-311.  doi:10.1007/s41918-021-00098-3

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Acceleration of the oxygen reduction reaction at the cathode is paramount in the development of low-temperature solid oxide fuel cells. At low operating temperatures between 450 and 600℃, the interactions between the surface and the bulk of the cathode materials greatly impact the electrode kinetics and consequently determine the overall efficacy and long-term stability of the fuel cells. This review will provide an overview of the recent progress in the understanding of surface-bulk interactions in perovskite oxides as well as their impact on cathode reactivity and stability. This review will also summarize current strategies in the development of cathode materials through bulk doping and surface functionalization. In addition, this review will highlight the roles of surface segregation in the mediation of surface and bulk interactions, which have profound impacts on the properties of cathode surfaces and the bulk and therefore overall cathode performance. Although trade-offs between reactivity and stability commonly exist in terms of catalyst design, opportunities also exist in attaining optimal cathode performance through the modulation of both cathode surfaces and bulk using combined strategies. This review will conclude with future research directions involving investigations into the role of oxygen vacancy and mobility in catalysis, the rational modulation of surface-bulk interactions and the use of advanced fabrication techniques, all of which can lead to optimized cathode performance.



Metal–Organic Frameworks and Their Derivatives as Cathodes for Lithium-Ion Battery Applications: A Review

R. Chenna Krishna Reddy, Xiaoming Lin, Akif Zeb, Cheng-Yong Su

2022, 5(2):  312-347.  doi:10.1007/s41918-021-00101-x

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The development of energy storage technology is important for resolving the issues and challenges of utilizing sustainable green energy in modern-day society. As an emerging technology, lithium-ion batteries (LIBs) are a common source of power for a wide variety of electronic devices, and major advances require the development and exploitation of new electrode materials; thus, fundamental knowledge of their atomic and nanoscale properties is necessary. By moving beyond conventional cathode candidates, metal-organic frameworks (MOFs) chemistry provides an excellent direction for designing and developing promising high-performance cathode materials for use in LIBs. Here, we carry out an overarching discussion on the development and application of MOFs and their derivatives as cathodes for lithium-ion battery applications. A timely overview of the exciting progress of MOFs as well as MOF-derived metallic components is highlighted. The unique characteristics of MOFs, such as their large surface area, high tunable porosity with uniform pore size, unique structural and morphological features, controllable framework composition and low densities, combine together to provide good interfacial charge transport properties and short diffusion lengths for electrons and/or ions that adequately support electrochemical redox reactions. The progress of MOFs and their derived composites as cathode candidates for LIBs is emphasized based on their electrochemical results, while also discussing the remaining issues and potential upcoming research directions.



Toward alkaline-stable anion exchange membranes in fuel cells: cycloaliphatic quaternary ammonium-based anion conductors

Jiandang Xue, Junfeng Zhang, Xin Liu, Tong Huang, Haifei Jiang, Yan Yin, Yanzhou Qin, Michael D. Guiver

2022, 5(2):  348-400.  doi:10.1007/s41918-021-00105-7

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Anion exchange membrane (AEM) stability has been a long-standing challenge that limited the widespread development and adoption of AEM fuel cells (AEMFCs). The past five years have been a period of exceptional progress in the development of several alkaline-stable AEMs with remarkable both ex situ and in situ AEMFC stability. Certain cycloaliphatic quaternary ammonium (cQA) (mainly five- and six-membered) based AEMs appear to be among those having the most promising overall performance. In this review, we categorize cQAs as cage-like (such as quaternized 1,4-diazabicyclo[2.2.2]octane, (QDABCO) and quinuclidinium), non-cage-like (such as pyrrolidinium and piperidinium) and N-spirocyclic (such as 6-azonia-spiro[5.5]undecane (ASU)). The degradation mechanisms of categorized cQAs are first elucidated. Through an understanding of how the cations are attacked by strongly nucleophilic OH-, improved structural design of incorporating alkaline-stable cations into AEMs is facilitated. Before a detailed description and comparison of the alkaline stability of cQAs and their respective AEMs, current protocols for the assessment of alkaline stability are discussed in detail. Furthermore, the initial AEMFC performance and fuel cell performance stability based on cQA AEMs are also examined. The main focus and highlight of this review are recent advances (2015-2020) of cQA-based AEMs, which exhibit both excellent cation and membrane alkaline stability. We aim to shed light on the development of alkaline-stable cQA-type AEMs, which are trending in the AEM community, and to provide insights into possible solutions for designing long-lived AEM materials.



Effects of Crystallinity and Defects of Layered Carbon Materials on Potassium Storage: A Review and Prediction

Xiaoxu Liu, Tianyi Ji, Hai Guo, Hui Wang, Junqi Li, Hui Liu, Zexiang Shen

2022, 5(2):  401-433.  doi:10.1007/s41918-021-00114-6

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Layered carbon materials (LCMs) are composed of basic carbon layer units, such as graphite, soft carbon, hard carbon, and graphene. While they have been widely applied in the anode of potassium-ion batteries, the potassium storage mechanisms and performances of various LCMs are isolated and difficult to relate to each other. More importantly, there is a lack of a systematic understanding of the correlation between the basic microstructural unit (crystallinity and defects) and the potassium storage behavior. In this review, we explored the key structural factors affecting the potassium storage in LCMs, namely, the crystallinity and defects of carbon layers, and the key parameters (La, Lc, d002, ID/IG) that characterize the crystallinity and defects of different carbon materials were extracted from various databases and literature sources. A structure-property database of LCMs was thus built, and the effects of these key structural parameters on the potassium storage properties, including the capacity, the rate and the working voltage plateau, were systematically analyzed. Based on the structure-property database analysis and the guidance of thermodynamics and kinetics, a relationship between various LCMs and potassium storage properties was established. Finally, with the help of machine learning, the key structural parameters of layered carbon anodes were used for the first time to predict the potassium storage performance so that the large amount of research data in the database could more effectively guide the scientific research and engineering application of LCMs in the future.