Lithium-sulfur batteries have been investigated as promising electrochemical-energy storage systems owing to their high theoretical energy density. Sulfur-based cathodes must not only be highly conductive to enhance the utilization of sulfur, but also effectively confine polysulfides to mitigate their dissolution. A new physical and chemical entrapment strategy is based on a highly efficient sulfur host, namely hollow carbon nanofibers (HCFs) filled with MnO2 nanosheets. Benefiting from both the HCFs and birnessite-type MnO2 nanosheets, the MnO2 @HCF hybrid host not only facilitates electron and ion transfer during the redox reactions, but also efficiently prevents polysulfide dissolution. With a high sulfur content of 71 wt % in the composite and an areal sulfur mass loading of 3.5 mg cm(-2) in the electrode, the MnO2 @HCF/S electrode delivered a specific capacity of 1161 mAh g(-1) (4.1 mAh cm(-2) ) at 0.05 C and maintained a stable cycling performance at 0.5 C over 300 cycles.

Lithium–sulfur batteries show advantages for next-generation electrical energy storage due to their high energy density and cost effectiveness. Enhancing the conductivity of the sulfur cathode and moderating the dissolution of lithium polysulfides are two key factors for the success of lithium–sulfur batteries. Here we report a sulfur host that overcomes both obstacles at once. With inherent metallic conductivity and strong adsorption capability for lithium-polysulfides, titanium monoxide@carbon hollow nanospheres can not only generate sufficient electrical contact to the insulating sulfur for high capacity, but also effectively confine lithium-polysulfides for prolonged cycle life. Additionally, the designed composite cathode further maximizes the lithium-polysulfide restriction capability by using the polar shells to prevent their outward diffusion, which avoids the need for chemically bonding all lithium-polysulfides on the surfaces of polar particles.

Owing to the overwhelming advantage in energy density, lithium–sulfur (Li–S) battery is a promising next-generation electrochemical energy storage system. Despite many efforts in pursuing long cycle life, relatively little emphasis has been placed on increasing the areal energy density. Herein, we have designed and developed a ‘pie' structured electrode, which provides an excellent balance between gravimetric and areal energy densities. Combining lotus root-like multichannel carbon nanofibers ‘filling' and amino-functionalized graphene ‘crust', the free-standing paper electrode (S mass loading: 3.6 mg cm−2) delivers high specific capacity of 1,314 mAh g−1 (4.7 mAh cm−2) at 0.1 C (0.6 mA cm−2) accompanied with good cycling stability. Moreover, the areal capacity can be further boosted to more than 8 mAh cm−2 by stacking three layers of paper electrodes with S mass loading of 10.8 mg cm−2.

Lithium-sulfur (Li-S) batteries have been considered as a promising candidate for next-generation electrochemical energy-storage technologies because of their overwhelming advantages in energy density. Suppression of the polysulfide dissolution while maintaining a high sulfur utilization is the main challenge for Li-S batteries. Here, we have designed and synthesized double-shelled nanocages with two shells of cobalt hydroxide and layered double hydroxides (CH@LDH) as a conceptually new sulfur host for Li-S batteries. Specifically, the hollow CH@LDH polyhedra with complex shell structures not only maximize the advantages of hollow nanostructures for encapsulating a high content of sulfur (75 wt %), but also provide sufficient self-functionalized surfaces for chemically bonding with polysulfides to suppress their outward dissolution. When evaluated as cathode material for Li-S batteries, the CH@LDH/S composite shows a significantly improved electrochemical performance.

Delicate design of nanostructures for oxygen‐evolution electrocatalysts is an important strategy for accelerating the reaction kinetics of water splitting. In this work, Ni–Fe layered‐double‐hydroxide (LDH) nanocages with tunable shells are synthesized via a facile one‐pot self‐templating method. The number of shells can be precisely controlled by regulating the template etching at the interface. Benefiting from the double‐shelled structure with large electroactive surface area and optimized chemical composition, the hierarchical Ni–Fe LDH nanocages exhibit appealing electrocatalytic activity for the oxygen evolution reaction in alkaline electrolyte. Particularly, double‐shelled Ni–Fe LDH nanocages can achieve a current density of 20 mA cm−2 at a low overpotential of 246 mV with excellent stability.

compositions have been extensively investigated. Many approaches, including chemical vapor deposition, [12,13] pyrolysis of metal complexes, [14,15] and carburization of the mixed Mo/W-based compounds and carbon sources, have been developed. [16,17] However, these traditional methods usually suffer from the inevitable aggregation and/or uncontrollable particle sintering with excessive growth at high temperatures, which may lead to the loss of active sites. [6,16,18] To further improve the electrocatalytic performance, three main strategies have been developed as follows: i) nanostructuring to provide larger specific surface areas and expose more active sites; [8,14] ii) doping of heteroatoms to modify the electronic state of the metal elements; [12,19] iii) compositing with carbon-based materials to improve the conductivity and stability of carbides. [20][21][22] Nevertheless, construction of ultrafine dual-phase carbides within nitrogen-rich carbon matrix has rarely been reported until now. [8,23] Recently, metal-organic frameworks (MOFs) have been regarded as the ideal reactive precursors to establish welldefined nanocrystals due to their highly ordered porous structures and diversified metal nodes/organic ligands. [24][25][26] In this work, Zn-based zeolitic imidazolate framework (ZIF-8) substituted with MO 4 units (denoted as ZIF-8-MO 4 , M = Mo or W) dodecahedrons are obtained through an anion exchange reaction between the Zn(imidazolate) 4 2− units in ZIF-8 and MO 4 2− anions in inorganic salts. Their similar four-connected open frameworks ensure the reaction possible. [27] Benefiting from the internal long-range ordered Zn-O-M connectivity, high carbon/nitrogen content, low boiling point of Zn, and high porosity of ZIF-8, the in situ generated carbides are evenly dispersed within the PNCDs in the form of ultrafine nanocrystals. The ultrafine nanocrystals confined within this porous nanostructure results in the strong contact between the carbides and the conductive carbon support, which not only provides more stable active sites but also facilitates the electron transport in the HER process. [18,21,28] Besides, the abundant nitrogen dopants can function as electron acceptors to assist the carbon atoms in the metal lattice, which is immensely conducive to enhance the catalytic activity. [16] Benefiting from the advantages of ultrafine nanocrystals and porous nitrogen-doped Designing novel non-noble electrocatalysts with controlled structures and composition remains a great challenge for efficient hydrogen evolution reaction (HER). Herein, a rational synthesis of ultrafine carbide nanocrystals confined in porous nitrogen-doped carbon dodecahedrons (PNCDs) by annealing functional zeolitic imidazolate framework (ZIF-8) with molybdate or tungstate is reported. By controlling the substitution amount of MO 4 units (M = Mo or W) in the ZIF-8 framework, dual-phase carbide nanocrystals confined in PNCDs (denoted as MC-M 2 C/PNCDs) can be obtained, which exhibit superior activity toward the HER to the single-phased MC...

A pyrolyzed polyacrylonitrile/selenium disulfide composite cathode manifests high performance for both lithium and sodium storage.

This work proposes a hierarchically structured cathode that simultaneously tackles several problems associated with high-sulfur-loading electrodes for lithium-sulfur batteries. This work overcomes the major limitations associated with other host materials of sulfur, and opens up new prospects for constructing more efficient nanostructures for moderating the diffusion loss of polysulfides and enhancing the reaction kinetics of sulfur. We hope this work will inspire scientists to develop better batteries to satisfy the world demand for energy storage.