周晓亚

Parasitic reactions between polysulfides, electrolytes, and Li metal need to be mitigated in Li–S batteries. Here, a new class of concentrated siloxane‐based electrolytes is reported, which can regulate the hidden solvation‐ion‐exchange process and thus simultaneously suppress Li dendrite and polysulfides dissolution, demonstrating significant improvement over the widely reported ether‐based electrolytes in terms of cycle stability, coulombic efficiency, and flammability.

Abstract

Lithium–sulfur batteries are attractive for automobile and grid applications due to their high theoretical energy density and the abundance of sulfur. Despite the significant progress in cathode development, lithium metal degradation and the polysulfide shuttle remain two critical challenges in the practical application of Li–S batteries. Development of advanced electrolytes has become a promising strategy to simultaneously suppress lithium dendrite formation and prevent polysulfide dissolution. Here, a new class of concentrated siloxane‐based electrolytes, demonstrating significantly improved performance over the widely investigated ether‐based electrolytes are reported in terms of stabilizing the sulfur cathode and Li metal anode as well as minimizing flammability. Through a combination of experimental and computational investigation, it is found that siloxane solvents can effectively regulate a hidden solvation‐ion‐exchange process in the concentrated electrolytes that results from the interactions between cations/anions (e.g., Li⁺, TFSI⁻, and S²⁻) and solvents. As a result, it could invoke a quasi‐solid‐solid lithiation and enable reversible Li plating/stripping and robust solid‐electrolyte interphase chemistries. The solvation‐ion‐exchange process in the concentrated electrolytes is a key factor in understanding and designing electrolytes for other high‐energy lithium metal batteries.

Liquid metal based materials offer distinct advantages for the fabrication of island‐bridge electrochemical electronics. This study describes a novel approachmerging the unique advantages of deterministic architectures with stress‐enduring nanoengineered inks, supported with dynamic electrical anchors inside the percolated network. Versatile applications with various functional materials are also demonstrated by printing epidermal biofuel cells tested successfully on human subjects.

Abstract

The adoption of epidermal electronics into everyday life requires new design and fabrication paradigms, transitioning away from traditional rigid, bulky electronics towards soft devices that adapt with high intimacy to the human body. Here, a new strategy is reported for fabricating achieving highly stretchable “island‐bridge” (IB) electrochemical devices based on thick‐film printing process involving merging the deterministic IB architecture with stress‐enduring composite silver (Ag) inks based on eutectic gallium‐indium particles (EGaInPs) as dynamic electrical anchors within the inside the percolated network. The fabrication of free‐standing soft Ag‐EGaInPs‐based serpentine “bridges” enables the printed microstructures to maintain mechanical and electrical properties under an extreme (≈800%) strain. Coupling these highly stretchable “bridges” with rigid multifunctional “island” electrodes allows the realization of electrochemical devices that can sustain high mechanical deformation while displaying an extremely attractive and stable electrochemical performance. The advantages and practical utility of the new printed Ag‐liquid metal‐based island‐bridge designs are discussed and illustrated using a wearable biofuel cell. Such new scalable and tunable fabrication strategy will allow to incorporate a wide range of materials into a single device towards a wide range of applications in wearable electronics.

A unique approach for precisely locating dental lesion sites, including those hidden and often overlooked by dentists, is developed by Cuiping Zhou, Yu Shrike Zhang, Jianhua Zhou, and co‐workers, reported in article number https://doi.org/10.1002/adma.2020000602000060, who use a fluorescent mouthguard consisting of a nanocomposite of zinc oxide and poly(dimethylsiloxane) to detect local release of volatile sulfur compounds. The low cost, long‐term stability, and good patient compliance of the mouthguard enable widely applicable, preliminary, yet accurate screening of dental lesions prior to dental clinics and routine physical examinations.

Metal‐organic framework derived micro/nano‐structured Ni₂P/Ni hybrids with a porous carbon coating are successfully prepared. As hydrogen evolution reaction catalysts, both experimental and computational results verify that the strong synergistic effect between Ni₂P and Ni renders an enhanced electrocatalytic performance. As anode for Li‐ion batteries, the well‐organized micro/nano‐structure and the conductive Ni core jointly promote the electrochemical reaction kinetics.

Abstract

The construction of bifunctional electrode materials for hydrogen evolution reaction (HER) and lithium‐ion batteries (LIBs) has been a hot topic of research. Herein, metal–organic frameworks (MOFs) derived micro‐/nanostructured Ni₂P/Ni hybrids with a porous carbon coating (denoted as Ni₂P/Ni@C) are prepared using a feasible pyrolysis–phosphidation strategy. On the one hand, the optimal Ni₂P/Ni@C catalyst exhibits superior HER performance with a low overpotential of 149 mV versus a reversible hydrogen electrode (RHE) at 10 mA cm⁻² and excellent durability. The density functional theory computations verify that the strong synergistic effect between Ni₂P and Ni could optimize the electronic structure, thus rendering the enhanced electrocatalytic performance. On the other hand, the Ni₂P/Ni@C electrode displays a reversible capacity of 597 mAh g⁻¹ after 1000 cycles at 1000 mA g⁻¹ and improved rate capability as an anode for LIBs, owing to the well‐organized micro‐/nanostructure and conductive Ni core. In addition, the electrochemical reaction mechanism of the Ni₂P/Ni@C electrode upon lithiation/delithiation is investigated in detail via ex situ X‐ray powder diffraction and X‐ray photoelectron spectroscopy methods. It is expected that the facile and controllable approach can be extended to fabricate other MOF‐based metal phosphides/metal hybrids for electrochemical energy storage and conversion systems.