Search

Lithium–sulfur batteries (LSBs) are widely regarded as promising next‐generation batteries due to their high theoretical specific capacity and low material cost. However, the practical applications of LSBs are limited by the shuttle effect of lithium polysulfides (LiPSs), electronic insulation of charge and discharge products, and slow LiPSs conversion reaction kinetics. Accordingly, the introduction of catalysts into LSBs is one of the effective strategy to solve the issues of the sluggished LiPS conversion. Because of their nearly 100% atom utilization and high electrocatalytic activity, single‐atom catalysts (SACs) have been widely used as reaction mediators for LSBs' reactions. Excitingly, the SACs with asymmetric coordination structures have exhibited intriguing electronic structures and superior catalytic activities when compared to the traditional M–N4 active sites. In this review, we systematically describe the recent advancements in the installation of asymmetrically coordinated single‐atom structure as reactions catalysts in LSBs, including asymmetrically nitrogen coordinated SACs, heteroatom coordinated SACs, support effective asymmetrically coordinated SACs, and bimetallic coordinated SACs. Particularly noteworthy is the discussion of the catalytic conversion mechanism of LiPSs spanning asymmetrically coordinated SACs. Finally, a perspective on the future developments of asymmetrically coordinated SACs in LSB applications is provided. [ABSTRACT FROM AUTHOR]

Zinc-based aqueous dual-ion batteries (ADIBs) with halogen-graphite intercalation compound positive electrodes are among the most competitive candidates for next-generation electrochemical energy storage systems. However, most of the electrolytes employed have been gel-like electrolytes; hence, a fundamental understanding of the halogen storage process using fluid hydrates will be essential for constructing efficient Zn-based ADIBs. Herein, the halogen storage mechanism on a graphite electrode from fluid ZnCl2/ZnBr2 hydrates is studied by experimental and computational methods. The results indicate that the halogen storage mechanism is a competition between conversion and intercalation. Moreover, the macroscopic electrode reaction is determined by both the ion-pair solvation state at the graphite–electrolyte interface and the subsequent reactant supply is influenced by the electrode reaction rate. [ABSTRACT FROM AUTHOR]

Tin diselenide, a promising anode material for sodium ion batteries (SIBs), still faces sluggish Na+ diffusion kinetics and severe volume change, resulting in undesirable cycling stability and rate capability. Heterostructure construction is an effective strategy for boosting Na+ storage of SnSe2. Herein, an appealing yolk‐shell nanostructure of SnSe2/NiSe2 heterointerface with rich Se vacancies embedded into N‐doped carbon (SnSe2/NiSe2@NC) is precisely designed through a facile hydrothermal process followed by a selenization strategy. The experimental studies coupled with theoretical calculations results verify that the heterostructure interfaces and Se vacancies accelerate the charge and Na+ transfer efficiency, improve Na+ adsorption energy and supply ample active sites. The yolk‐shell nanostructure and N‐doped carbon buffer the volume variation and improve the structural stability of the electrode material during sodium storage processes. The SnSe2/NiSe2@NC delivers ultra‐long term cycling stability (322.7 mAh g−1 after 7500 cycles at 3 A g−1) and exceptional rate capability (314.6 mAh g−1 at 10 A g−1). The Na‐ion storage mechanism of SnSe2/NiSe2@NC is explored through in situ X‐ray diffraction and ex situ high‐resolution transmission electron microscopy analysis. The present work provides an effective avenue to the rational design of heterostructure anode materials for high efficiency SIBs. [ABSTRACT FROM AUTHOR]

With the rapid development of new energy sources, proton-exchange membrane fuel cells (PEMFCs) have been increasingly recognized and promoted. There are many device-level and infrastructure-related challenges that need to be overcome before widespread commercialization can be achieved, one of the most critical being increasing the power density of PEMFCs. In this review, the technical development direction of the next generation of high power density PEMFCs is proposed. We present the latest progress related to the design of PEMFCs with high specific power density, focusing on catalysts, proton exchange membranes, gas diffusion layers, and bipolar plates. The challenges and future development trends associated with high-specific-power-density PEMFCs are also presented, providing insight for further improving the power density of PEMFCs. [ABSTRACT FROM AUTHOR]