No abstract

Rational design, convenient fabrication, and application of double-shelled hollow architectures with well-defined morphology and multicompositions as electrodes for rechargeable batteries still remain great challenges. Herein, double-shelled Ni− Fe−P/N-doped carbon nanoboxes (defined as Ni−Fe−P/NC) were synthesized and then applied as electrode materials for potassiumion batteries (KIBs) and Li−S batteries, first. The unique architectures could not only alleviate volume changes and prevent aggregation of Ni−Fe−P/NC during cycling but could also provide efficient surface areas for infiltration of electrolyte. Additionally, nitrogen-doped carbon could improve the conductivity of the electrode. Hence, when these Ni−Fe−P/NC nanoboxes were applied as anode materials for KIBs, they delivered enhanced cycling stability (172.9 mA h g −1 after 1600 cycles at 500 mA g −1 and 115 mA h g −1 after 2600 cycles at 1000 mA g −1 ). Meanwhile, the Ni−Fe−P/NC could also be used as the sulfur host material for Li−S batteries; benefiting from its unique hollow structure, it can accommodate high sulfur loading and have strong chemical adsorption ability to polysulfides.

Lithium-sulfur batteries are considered to be one of the most promising energy-storage systems because of their high theoretical energy density, as well as low cost, nontoxicity and natural abundance of sulfur. However, their poor cycling stability mostly originates from the shuttling of polysulfides which hinders their future practical applications. Here, multi-shelled CoP nanospheres are designed as a coated separator material for Li-S batteries for the first time. Conductive CoP can efficiently anchor polysulfides not only owing to its polar character but also its partial natural surface oxidation feature as evidenced by XPS results, which further activates Co sites for chemically trapping polysulfides via strong Co-S bonding. Furthermore, the unique multi-shelled structure can capture polysulfides to alleviate the "shuttle effect". Consequently, the battery using a CoP coated separator exhibits outstanding cycling stability with a capacity degradation of 0.078% per cycle over 500 cycles at a current density of 1 C and excellent rate performance (725 mA h g-1 at 5 C). It is also worth noting that a high areal capacity of 3.2 mA h cm-2 can be achieved even with a sulfur loading of 3.24 mg cm-2. Our approach demonstrates the convenient fabrication and application potential for a multi-shelled CoP nanosphere modified separator for highly efficient Li-S batteries.

Coral-like NixCo1−xSe2 anode material with hierarchical architecture delivers ultralong cycle life and ultrahigh rate capability in SIBs.

The selection of routes is an important issue in wireless networks when network coding is used. Existing research formulate network-coding-aware routing as a linear optimization program. However, deploying such method in real wireless networks is impractical. To solve this issue, in this paper, a practical network-coding aware routing protocol is proposed for unicast sessions in wireless networks. The protocol is based on a novel routing metric design that captures the characteristics of network coding and unicast sessions. To ensure the novel routing metric can operate with practical and widely available path calculation mechanisms, a unique mapping process is used to map a real wireless network to a virtual network. The mapping process ensures that the paths with the biggest coding opportunities will be selected by commonly used path calculation mechanisms. Simulation results show that the proposed routing protocol is effective.