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To solve the slow kinetics of polysulfide conversion reaction in Li-S battery, many transition metal nitrides were developed for sulfur hosts. Herein, novel polyaniline-coated porous vanadium nitride (VN) microrods were synthesized via a calcination, washing and polyaniline-coating process, which served as sulfur host for Li-S battery exhibited high electrochemical performance. The porous VN microrods with high specific surface area provided enough interspace to overcome the volume change of the cathode. The outer layer of polyaniline as a conductive shell enhanced the cathode conductivity, effectively blocked the shuttle effect of polysulfides, thus improving the cycling capacity of Li-S battery. The cathode exhibited an initial capacity of 1007 mAh g−1 at 0.5 A g−1, and the reversible capacity remained at 735 mAh g−1 over 150 cycles. [ABSTRACT FROM AUTHOR]

Shuttle effect and slow redox reactions in Li-S battery limit its commercial application. Herein, TiN nanotubes with N-doped carbon coating (TiN/N-C NT) were obtained via MoO 3 nanorod template-assistant hydrothermal method and followed by polydopamine coating and carbonization/nitriding. When used as sulfur host, the tubular structure buffers the volume change in lithiation process and shortens Li+ transfer route. Consequently, the TiN/N-C NT cathode exhibits a high capacity of 1010.3 mAh g−1 over 100 cycles at 0.1 A g−1. It provides a low capacity decay rate of 0.057 % per cycle over 500 cycles at a high current density of 1.0 A g−1. This study provides a promising method for preparing high-performance Li-S battery. • Special TiN nanotubes coated with N-doped carbon layer were developed. • It involves template-assistant hydrothermal method, PDA coating and carbonization/nitriding. • TiN/N-C nanotubes exhibit high stable capacity and superior rate performance. • High performance is due to thier hollow structure and strong LiPSs chemisorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • BN nanocrystals merely and evenly anchored on carbon nanosheets were developed. • BN@CNs were synthesized via a mixing process and an in-situ nitriding strategy. • The BN/CNs-2/S cathode exhibits high stable capacity and high rate performance. • High performance is due to catalytic effect of BN and excellent conductivity of CNs. Sandwich structure of boron nitride (BN) nanocrystals wrapped with uniform interconnected N-doped carbon nanosheets (N-CNs) is prepared as a lithium-sulfur battery cathode material to overcome the sluggish redox reaction and severe "shuttle effect" of lithium polysulfides (LiPSs). The BN@N-CNs-2/S presents outstanding rate capacity of 528 mAh g−1 at 2 A g−1, with extended cycle life and sluggish capacity decrease rate of 0.026% per cycle at 2 A g−1 for more than 1000 cycles. Such high performance is a result of the unique sandwich structure of BN nanocrystals evenly compounded on N-CNs, which leads to uniform distribution of active sulfur species and effectively alleviates volume expansion in the cycling process. The BN@N-CNs sandwich structure possesses the key advantages of high conductivity of N-CNs, strong chemisorption and catalytic effect for LiPSs, which is demonstrated by theoretical calculations and cyclic voltammetry curves of the symmetrical cells. [ABSTRACT FROM AUTHOR]

The polysulfide shuttle phenomenon in the cycling process of lithium-sulfur (Li–S) batteries restricts their practical applications. Herein, polypyrrole (PPy) coated hollow cobalt manganate (CoMn 2 O 4) dodecahedrons were prepared via template method, which combines the advantages of manganese-based metal oxide and conductive polymer effectively. The CoMn 2 O 4 as bimetal oxides can trap the intermediate products and inhibit the dissolution of short chain polysulfides in the organic electrolyte. Moreover, the hollow dodecahedron structure provides enough space to alleviate volume change in the cycle process. Furthermore, the conductive PPy layer can enhance the conductivity of nanocomposite and suppress the shuttle effect in the electrolyte. The initial capacity of CoMn 2 O 4 /S@PPy cathode reaches up to 1407 mA h g-1 at 0.1 A g-1. The capacity retained ca.736 mA h g-1 at 0.1 A g-1 for 150 cycles and 659 mA h g-1 at 0.5 A g-1 when cycled 500 times, respectively, along with the Coulombic efficiency was over 99%. Owing to these outstanding electrochemical performances, the as-prepared nanocomposite is promising to be a superior sulfur host in the field of Li–S batteries. [ABSTRACT FROM AUTHOR]

• A special porous CoMn 2 O 4 nanocubes was developed. • It involves a template precipitation method and a subsequent annealing process. • The CoMn 2 O 4 /S@PPy nanocubes exhibit high stable capacity and rate performance. • High performance is due to bimetallic effect, porous structure and PPy coating. [Display omitted] Lithium–sulfur (Li–S) batteries suffer from the poor conductivity originated from sulfur and shuttle effect arisen from the polysulfides dissolution. Herein, cobalt manganate (CoMn 2 O 4) porous nanocubes coated with polypyrrole (PPy) as sulfur carrier are prepared using MnCO 3 nanocube template through a precipitation method and a subsequent annealing process. The unique approach can obtain porous CoMn 2 O 4 nanocubes with uniform morphology and abundant exposed active sites. The plentiful mesopores among the porous nanocubes are beneficial to accommodation of sulfur. In addition, the porous CoMn 2 O 4 nanocubes can trap polysulfides in the cycling process owing to the chemical bonds between CoMn 2 O 4 and polysulfides. Moreover, PPy coating severed as conductive layer not only enhances electrical conductivity of the cathode, but also confines polysulfides via the formation of N–Li–S bonds during cycling process. Therefore, the porous CoMn 2 O 4 /S@PPy nanocubes with 66.9% sulfur mass content delivered a capacity of 533 mAh g−1 over 500 cycles at 1 A g−1 with a capacity decay rate of 0.064% each cycle, and a Coulombic efficiency of 98%, suggesting the enhanced cycling performance of cathode. The facile template precipitation method combined with an annealing process contribute a new approach to synthesize unique porous CoMn 2 O 4 structure as sulfur carrier for Li–S batteries [ABSTRACT FROM AUTHOR]

• TiN nanocrystals merely and evenly anchored on carbon nanosheets were developed. • TiN@CNs were synthesized via a facile hydrolysis and an in-situ nitriding strategy. • The TiN/CNs-2/S cathode exhibits high stable capacity and high rate performance. • High performance is due to catalytic effect of TiN and excellent conductivity of CNs. The "shuttle effect" of lithium polysulfides (LiPSs) and sluggish redox reactions limit the application of Li−S batteries. In this study, titanium nitride (TiN) nanocrystals merely and evenly anchored on carbon nanosheets (TiN@CNs) are prepared by heat treating TiO 2 @CNs in flowing ammonia. TiN nanoparticles do not accumulate in places without CNs, which can alleviate volume expansion in cycling process. CNs with high conductivity and a large specific surface area can accelerate Li+ and electron transportation and accommodate a higher sulfur content. Moreover, TiN nanocrystals can effectively anchor polysulfides and accelerate the redox reaction, which can be explained by the adsorption experiment of LiPSs, X-ray photoelectron spectroscopy, and theoretical calculations. Thus, the TiN@CNs-2/S cathode delivers an initial capacity of 1273 mAh g−1 and remains at 908 mAh g−1 after 100 cycles for 0.5 A g−1. For the long-term cycle performance, the cathode exhibits a slow capacity decay rate of 0.035% per cycle over 1000 cycles at 2 A g−1. This novel structure has potential in the design of advanced performance Li−S batteries. Titanium nitride nanocrystals merely and evenly anchored on carbon nanosheets via heat treating TiO 2 /CNs in flowing ammonia, effectively anchor polysulfides and accelerate the redox reaction for Li−S batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

The applications of Li S batteries are restricted by the issues of the imperfect conductivity and severe volumetric change of active materials together with shuttle effect of lithium polysulfides, which requires a kind of material with appropriately multifunctional structure as sulfur host. Herein, an N–doped hierarchical porous carbon composite is synthesized via a high temperature carbonization method. The N–doped hierarchical porous carbon with a large number of micropores, mesopores and macropores provides the abundant interconnected network matrixes and high specific surface area, thus guaranteeing a high sulfur loading, and adapting the volumetric expansion during the lithium intercalation process. The macropore channels and conductive interconnected networks can accelerate the diffusion of electrons/ions among the cathode. Moreover, the mesopores and micropores besides the high amount N–doping accommodate high–level sulfur loading and immobilize lithium polysulfides via physical absorption and chemical confinement. The as–prepared N–doped hierarchical porous carbon compounded with sulfur as a cathode delivers a satisfactory initial capacity of 1285 mAh g−1 at 0.2 A g−1 and a reversible capacity of 517 mAh g−1 at 0.5 A g−1 over 1000 cycles, illustrating the improved electrochemical performances of the cathode. The high temperature carbonization method provides a new way to construct the hierarchical porous structured carbon with chemical doping. Unlabelled Image • N-doped hierarchical porous carbon was developed. • It has a large number of micropores, mesopores and macropores. • N-doped hierarchical porous carbon exhibit high capacity and rate performance. • High performance is ascribed to the porous hierarchical structure and N doping. [ABSTRACT FROM AUTHOR]