Urchin-shaped NiCo 2 Se 4 (u-NCSe) nanostructures as efficient sulfur hosts are synthesized to overcome the limitations of lithium-sulfur batteries (LSBs). u-NCSe provides a beneficial hollow structure to relieve volumetric expansion, a superior electrical conductivity to improve electron transfer, a high polarity to promote absorption of lithium polysulfides (LiPS), and outstanding electrocatalytic activity to accelerate LiPS conversion kinetics. Owing to these excellent qualities as cathode for LSBs, S@u-NCSe delivers outstanding initial capacities up to 1403 mAh g −1 at 0.1 C and retains 626 mAh g −1 at 5 C with exceptional rate performance. More significantly, a very low capacity decay rate of only 0.016% per cycle is obtained after 2000 cycles at 3 C. Even at high sulfur loading (3.2 mg cm −2 ), a reversible capacity of 557 mAh g −1 is delivered after 600 cycles at 1 C. Density functional theory calculations further confirm the strong interaction between NCSe and LiPS, and cytotoxicity measurements prove the biocompatibility of NCSe. This work not only demonstrates that transition metal selenides can be promising candidates as sulfur host materials, but also provides a strategy for the rational design and the development of LSBs with long-life and high-rate electrochemical performance.

The development of cost-effective oxygen evolution catalysts is of capital importance for the deployment of large scale energy storage systems based on metal-air batteries and reversible fuel cells. In this direction, a wide range of materials have been explored, especially in more favorable alkaline conditions, and several metal chalcogenides have particularly demonstrated excellent performances. However, chalcogenides are thermodynamically less stable than the corresponding oxides and hydroxides under oxidizing potentials in alkaline media. While this instability in some cases has prevented the application of chalcogenides as oxygen evolution catalysts, and it has been disregarded in some other, we propose to use it in our favor to produce high performance oxygen evolution catalysts. We characterize here the in situ chemical, structural and morphological transformation during the oxygen evolution reaction (OER) in alkaline media of Cu2S into CuO nanowires (NWs), mediating the intermediate formation of Cu(OH)2. We also test their OER activity and stability under OER operation in alkaline media, and compare them with the OER performance of Cu(OH)2 and CuO nanostructures directly grown on the surface of a copper mesh. We demonstrate here that CuO produced during OER from Cu 2 S displays an extraordinary electrocatalytic performance toward OER, well above that of CuO and Cu(OH)2 synthesized mediating no OER in situ transformation.3

Original measurement data are available upon reasonable request.

The inhibition of this polysulfide shuttle effect and the promotion of the redox reaction kinetics remains as the key material challenges of lithium-sulfur batteries (LSBs) to be urgently solved.Here we report a new architecture for the cathode material based on nanoreactor of ZnSe/Ndoped hollow carbon (ZnSe/NHC). This material combination and the hollow geometry provide three key benefits to the LSBs cathode: i) The combination of lithiophilic sites of NHC and sulfiphilic sites of ZnSe effectively trap LiPS as demonstrated by experimental results and density functional theory (DFT) calculations; ii) In part related to this promoted adsorption, the ZnSe/NHC material combination is able to facilitate the Li + diffusion, thus promoting the redox reaction kinetics; iii) The hollow nanoreactor design traps LiPS and accommodates volumetric expansion preventing the cathode material decomposition. As a result, LSBs cathodes based on this hybrid material, S@ZnSe/NHC, are characterized by high initial capacities, 1475 mAh g −1 at 0.1 C and 542 mAh g −1 at 3 C, and excellent rate capability. Besides, these cathodes deliver stable operation with only 0.022% capacity decay per cycle after 800 cycles at 3 C. Even at high sulfur loading of 3.2 mg cm −2 , a reversible capacity of 540.5 mAh g −1 is delivered after 600 cycles at 1 C. Overall, this work not only further demonstrates the large potential of transitionmetal selenides as cathode materials in LSBs, but also demonstrates the nanoreactor design to be a highly suitable architecture to enhance cycle stability.

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Ni–Co–Sn alloys show improved performance toward the methanol oxidation reaction in alkaline media.

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