Silicon (Si) shows promise as an anode material in lithium-ion batteries due to its very high specific capacity. However, Si is highly brittle, and in an effort to prevent Si from fracturing, the research community has migrated from the use of Si films to Si nanoparticle based electrodes. However, such a strategy significantly reduces volumetric energy density due to the porosity of Si nanoparticle electrodes. Here we show that contrary to conventional wisdom, Si films can be stabilized by two strategies: (a) anchoring the Si films to a carbon nanotube macrofilm (CNM) current collector and (b) draping the films with a graphene monolayer. After electrochemical cycling, the graphene-coated Si films on CNM resembled a tough mud-cracked surface in which the graphene capping layer suppresses delamination and stabilizes the solid electrolyte interface. The graphene-draped Si films on CNM exhibit long cycle life (>1000 charge/discharge steps) with an average specific capacity of ∼806 mAh g. The volumetric capacity averaged over 1000 cycles of charge/discharge is ∼2821 mAh cm, which is 2 to 5 times higher than what is reported in the literature for Si nanoparticle based electrodes. The graphene-draped Si anode could also be successfully cycled against commercial cathodes in a full-cell configuration.

The next generation of deformable and shape-conformable electronics devices will need to be powered by batteries that are not only flexible but also foldable. Here we report a foldable lithium-sulfur (Li-S) rechargeable battery, with the highest areal capacity (∼3 mAh cm(-2)) reported to date among all types of foldable energy-storage devices. The key to this result lies in the use of fully foldable and superelastic carbon nanotube current-collector films and impregnation of the active materials (S and Li) into the current-collectors in a checkerboard pattern, enabling the battery to be folded along two mutually orthogonal directions. The carbon nanotube films also serve as the sulfur entrapment layer in the Li-S battery. The foldable battery showed <12% loss in specific capacity over 100 continuous folding and unfolding cycles. Such shape-conformable Li-S batteries with significantly greater energy density than traditional lithium-ion batteries could power the flexible and foldable devices of the future including laptops, cell phones, tablet computers, surgical tools, and implantable biomedical devices.

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As a key component of batteries, the electrolyte determines the ion transport and interface chemistry of the cathode and anode. In this work, we develop a dual-network structured hydrogel electrolyte composed of polyacrylamide (PAM), sodium alginate (SA) and potassium iodide (KI) for solid-state zinc-air/iodide hybrid batteries. The assembled hybrid battery shows excellent renewability and a long cycling life of 110 h with a high energy efficiency of 80 %. The ion-crosslinked dual-network structure endows the material with improved mechanical strength and increased ionic conductivity. More importantly, the introduction of iodine species not only offers more favorable cathodic kinetics of iodide/iodate redox than oxygen electrocatalysis but also regulates the solvation structure of zinc ions to ensure better interface stability. This work provides significant concepts for developing novel solidstate electrolytes to realize high-performance energy devices and technologies.

The frequent occurrence of chiral 1-substituted-1,2,3,4-tetrahydroisoquinoline (THIQ) ring systems in a large number of alkaloids possessing a broad spectrum of biological and pharmaceutical properties has led to significant increasing interest in their synthesis. [1] To date, most of the traditional synthetic approaches are based on procedures employing chiral building blocks, auxiliaries, or reagents. [2] Thus, with particular emphasis on economic and ecologically valuable processes, much effort has been directed toward the development of catalytic enantioselective transformations to access enantiomerically pure 1-substituted-THIQ frameworks with a high level of selectivity. [3] Among them, the asymmetric hydrogenation [4] and asymmetric transfer hydrogenation (ATH) [5] of 1-substituted-3,4-dihydroisoquinolines (DHIQs) [6] are powerful methods because they have an intrinsic operational efficiency and are highly atom economical. However, despite the significant advances produced in these areas over the last two decades, only relatively few catalyst systems operating with high selectivity have been reported so far in the literature for the reduction of 1-alkyl-3,4-DHIQs. [6h,i, 7d] Furthermore, and to the best of our knowledge, the asymmetric reduction of 1-aryl-substituted-3,4-DHIQs has only been sporadically described and still continues to be a challenge in the field of asymmetric hydrogenation. [7] To date, most of the existing catalytic systems are restricted to 1-phenyl-3,4-DHIQ as a model substrate and provide low to moderate catalytic efficiency. As far as the ATH of 1-aryl-substituted-3,4-DHIQs is concerned, only very few examples have been described. In 1999, Vedejs et al. [7c] reported the Ru II -catalyzed ATH of 1-aryl-substituted-3,4-DHIQ substrates. Although high enantioselectivity was achieved (up to 98.7 %), the method only tolerates a narrow range of ortho substituents, such as o-Br, o-NO 2 , and o-N(R)SO 2 Ar, with low to reasonable yields of 1-76 %. Asymmetric hydrogenation of 1-aryl-3,4-DHIQs using iri-dium complexes have been recently reported by Zhang et al. [7d] and our group, [7e] with enantioselectivities higher than 90 %. However, these two catalytic systems provide only moderate enantioselectivity for sterically hindered 1-(2'substituted-aryl)-3,4-DHIQs. Therefore, the development of highly enantioselective methods that allow rapid and efficient access to the valuable 1-aryl-tetrahydroisoquinoline scaffold remains highly desirable. As part of our ongoing research program toward the use of metal-catalyzed asymmetric reduction for the synthesis of biologically relevant targets, [8] and taking in account the scarce examples of ATH of arylsubstituted-dihydroquinoline derivatives, we report herein a general and highly enantioselective Ru-catalyzed transfer hydrogenation of 1-aryl-substituted-1,2,3,4-DHIQs under mild conditions leading to the corresponding THIQ derivatives with a broad substrate scope and enantioselectivities of up to 99 %.We first examined the ATH of 1-phenyl-3,4-di...

Lithium (Li) metal is promising in the next‐generation energy storage systems. However, its practical application is still hindered by the poor cycling performance and serious safety issues for the consequence of dendritic Li. Herein, a dendrite‐free Li/carbon nanotube (CNT) hybrid is proposed, which is fabricated by direct coating molten Li on CNTs, for Li‐metal batteries. The favorable thermodynamic and kinetic conditions are the powerful force to drive the rapid lift upwards and infusion of molten Li into CNTs network, which is the key to form a uniform metallic layer in Li/CNTs hybrid. The obtained hybrid indicates super‐stable functions even at an ultrahigh current density of 40 mA cm−2 for 2000 cycles with a stripping/plating capacity of 2 mAh cm−2 in symmetric cells. Subsequently, this hybrid also demonstrates a significantly decreased resistance, excellent cycling stability at high current density and flexibility in the full Li‐S battery. This work provides valuable concepts in fabricating Li anodes toward Li‐metal batteries and beyond for their high‐level services.

Asymmetric hydrogenation of 1-aryl-3,4-dihydroisoquinolines using the [IrCODCl](2)/(R)-3,5-diMe-Synphos catalyst is reported. Under mild reaction conditions, this atom-economical process provides easy access to a variety of enantioenriched 1-aryl-1,2,3,4-tetrahydroisoquinoline derivatives, which are important pharmacophores found in several pharmaceutical drug candidates, in high yields and enantiomeric excesses up to 99% after a single crystallization.