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    Revealing the Various Electrochemical Behaviors of Sn4P3 Binary Alloy Anodes in Alkali Metal Ion Batteries
    (Weinheim : Wiley-VCH, 2021) Zhou, Junhua; Lian, Xueyu; You, Yizhou; Shi, Qitao; Liu, Yu; Yang, Xiaoqin; Liu, Lijun; Wang, Dan; Choi, Jin-Ho; Sun, Jingyu; Yang, Ruizhi; Rummeli, Mark H.
    Sn4P3 binary alloy anode has attracted much attention, not only because of the synergistic effect of P and Sn, but also its universal popularity in alkali metal ion batteries (AIBs), including lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and potassium-ion batteries (PIBs). However, the alkali metal ion (A+) storage and capacity attenuation mechanism of Sn4P3 anodes in AIBs are not well understood. Herein, a combination of ex situ X-ray diffraction, transmission electron microscopy, and density functional theory calculations reveals that the Sn4P3 anode undergoes segregation of Sn and P, followed by the intercalation of A+ in P and then in Sn. In addition, differential electrochemical curves and ex situ XPS results demonstrate that the deep insertion of A+ in P and Sn, especially in P, contributes to the reduction in capacity of AIBs. Serious sodium metal dendrite growth causes further reduction in the capacity of SIBs, while in PIBs it is the unstable solid electrolyte interphase and sluggish dynamics that lead to capacity decay. Not only the failure mechanism, including structural deterioration, unstable SEI, dendrite growth, and sluggish kinetics, but also the modification strategy and systematic analysis method provide theoretical guidance for the development of other alloy-based anode materials. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH
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    Bioinspired Underwater Adhesion to Rough Substrates by Cavity Collapse of Cupped Microstructures
    (Weinheim : Wiley-VCH, 2021) Wang, Yue; Hensel, René
    Underwater or wet adhesion is highly desirable for numerous applications but is counteracted by the liquids in the contact which weaken intermolecular attraction. The problem is exacerbated in conjunction with surface roughness when liquids partially remain in grooves or dimples of the substrate. In the present study, a cupped microstructure with a cavity inspired by suction organs of aquatic animals is proposed. The microstructures (cup radius of 100 µm) are made from polyurethane using two-photon lithography followed by replica molding. Adhesion to rough substrates is emulated experimentally by a micropatterned model substrate with varying channel widths. Pull-off stresses are found to be about 200 kPa, i.e., twice atmospheric pressure. Evaluation of force–displacement curves together with in situ observations reveal the adhesion mechanism, which involves adaptation to surface roughness and an elastic force induced by the collapse of the cavity that holds sealed contact with the substrate during retraction. This new microarchitecture may pave the way for next generation microstructures applicable to real, rough surfaces under wet conditions.