Rationally constructing inexpensive sulfur hosts that have high electronic conductivity, large void space for sulfur, strong chemisorption, and rapid redox kinetics to polysulfides is critically important for their practical use in lithium–sulfur (Li–S) batteries. Herein, we have designed a multifunctional sulfur host based on yolk–shelled Fe2N@C nanoboxes (Fe2N@C NBs) through a strategy of etching combined with nitridation for high-rate and ultralong Li–S batteries. The highly conductive carbon shell physically confines the active material and provides efficient pathways for fast electron/ion transport. Meanwhile, the polar Fe2N core provides strong chemical bonding and effective catalytic activity for polysulfides, which is proved by density functional theory calculations and electrochemical analysis techniques. Benefiting from these merits, the S/Fe2N@C NBs electrode with a high sulfur content manifests a high specific capacity, superior rate capability, and long-term cycling stability. Specifically, even after 600 cycles at 1 C, a capacity of 881 mAh g–1 with an average fading rate of only 0.036% can be retained, which is among the best cycling performances reported. The strategy in this study provides an approach to the design and construction of yolk–shelled iron-based compounds@carbon nanoarchitectures as inexpensive and efficient sulfur hosts for realizing practically usable Li–S batteries.

We present here solution-processed photodetectors based on a methyl ammonium lead iodide perovskite (MAPbI3) and nanocrystalline graphite (NCG) hybrid composite. The highest responsivity of the best MAPbI3/NCG photodetector was 795 mA W(-1) at 500 nm visible light, which is almost twice as high as that of the NCG-free MAPbI3 photodetector (408 mA W(-1)). The enhanced performance of the MAPbI3/NCG photodetector arises from the improved charge extraction at the MAPbI3/NCG interface. The dependence of photodetector performance on the mass percentage of NCG (the ratio of NCG to MAPbI3) in the hybrid materials is also reported here, and is correlated to the fabrication process. Moreover, by comparing the responsivity of the devices with different channel lengths, we show that the performance of hybrid photodetectors can be further tuned by tailoring the channel length.

Rechargeable aqueous zinc-ion batteries (ZIBs) have been considered as a promising candidate for the large-scale energy storage device owing to their low cost and high safety. However, the practical application of aqueous ZIBs at low temperature environment is hindered by the freezing aqueous electrolytes, which leads to a sharp drop in ionic conductivity, and thereby a rapid deterioration of battery performance. Herein, a chaotropic salt electrolyte based on low concentration aqueous Zn(ClO 4 ) 2 with superior ionic conductivity under low temperature (4.23 mS/cm at À50 C) is reported. The anti-freezing methodology introduced here is completely different from conventional freezeresistant design of using "water-in-salt" electrolyte, cosolvents, or anti-freezing agent additives strategy. Experimental analysis and molecular dynamics simulations reveal that the as-prepared Zn(ClO 4 ) 2 electrolyte possesses faster ionic migration compared with other commonly used Zn-based salts (i.e., Zn (CF 3 SO 3 ) 2 and ZnSO 4 ) electrolyte. It is found that Zn(ClO 4 ) 2 electrolyte can suppress the ice crystal construction by forming more hydrogen bonds between solute ClO 4 À and solvent H 2 O molecules, thus leading to a superior anti-freezing property. The fabricated ZIBs using this aqueous electrolyte exhibits a dramatically enhanced specific capacity, remarkable rate capability, and great cycling stability over a wide temperature range, from À50 to 25 C. The aqueous ZIBs also exhibit an outstanding energy density of Guoshen Yang, Jialei Huang, and Xuhao Wan contributed equally to this work.

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