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Lithium‐sulfur (Li‐S) batteries are one of the most promising high‐energy‐density storage systems. However, serious capacity attenuation and poor cycling stability induced by the shuttle effect of polysulfide intermediates can impede the practical application of Li‐S batteries. Herein we report a novel sulfur cathode by intertwining multi‐walled carbon nanotubes (CNTs) and porous boron nitride fibers (BNFs) for the subsequent loading of sulfur. This structural design enables trapping of active sulfur and serves to localize the soluble polysulfide within the cathode region, leading to low active material loss. Compared with CNTs/S, CNTs/BNFs/S cathodes deliver a high initial capacity of 1222 mAh g−1 at 0.1 C. Upon increasing the current density to 4 C, the cell retained a capacity of 482 mAh g−1 after 500 cycles with a capacity decay of only 0.044 % per cycle. The design of CNTs/BNFs/S gives new insight on how to optimize cathodes for Li‐S batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • The N pr -CNs is synthesized by pre-pelletizing and subsequent pyrolysis process. • The N pr -CNs have dominate pyrrolic N-doping, unique structure and electronic state. • It can inhibit the shuttle effect and improve redox kinetics by synergistic effect. • The Li-S cell with N pr -CNs/PP deliver high discharge capacity of 932 mAh g−1 at 1C. The practical applications of lithium-sulfur (Li-S) batteries are rather limited by the shuttle effect of lithium polysulfides (LiPSs) and sluggish redox reaction kinetics. Here, a kind of pyrrolic-N-rich carbon nanosheets (N pr -CNs) are prepared by introducing melamine cyanurate (MCA) into the carbonization process of polyacrylonitrile (PAN). As a mediator in Li-S batteries, hierarchical pores, dominant pyrrolic-N-doping, disorder/defective structures and unique electronic states endow N pr -CNs with synergistic adsorption-catalysis function for S species. Specifically, they can effectively inhibit LiPSs shuttle, catalyze the conversion of both liquid-phase LiPSs and solid-phase Li 2 S, reduce the charge transfer resistance and enhance Li-ions migration rate. Hence, it can make the Li-S batteries deliver excellent rate performance and cycling stability. The battery can reach ultrahigh discharge capacity of 932.0 mAh g−1 at the beginning under current density of 1C and even liberate a capacity as high as 1109.4 mAh g−1 at 0.2C with high sulfur loading of 3.8 mg cm−2. [ABSTRACT FROM AUTHOR]

[Display omitted] • BNNSs/rGO heterostructure is synthesized by self-assembly crosslinking approach. • The mediator can suppress the shuttle effect of LiPSs by superior adsorption. • It can markedly catalyze the conversion of liquid-phase LiPSs and solid-phase Li 2 S. • BNNSs/rGO-based Li-S batteries show improved electrochemical reaction kinetics. Lithium-sulfur (Li-S) battery with high theoretical specific capacity (1675 mAh/g), has been deemed as one of the most potential candidates of secondary energy storage system. However, the large-scale applications of Li-S batteries have been obstructed by internally sluggish multi-step redox reaction and terrible shuttle effect of lithium polysulfides (LiPSs). Herein, boron nitride nanosheets/reduced graphene oxide (BNNSs/rGO) heterostructure prepared by self-assembly crosslinking method has been designed to modify commercial separator for Li-S batteries. The hierarchical pores, physical and chemical cross-links within heterostructure can significantly enhance the adsorption capacity for LiPSs, uniquely physical and electronic interaction between BNNSs and rGO can effectively catalyze the conversion of sulfurated species. Benefiting from the synergistic adsorption-catalysis effect, BNNSs/rGO not only greatly inhibits the shuttle behaviors, but also considerably accelerates the electrochemical reaction kinetics for LiPSs and Li 2 S. Attributed to these merits, Li-S battery with BNNSs/rGO heterostructure mediator delivers superiorly reversible capacity as high as 915.0 mAh/g at 1 C. Even at high sulfur loading of 3.9 mg cm−2, the cell delivers ultra-stable specific capacity of 629.1 mAh/g at 1 C, and still maintains 605.5 mAh/g over 500 cycles corresponding to a capacity fade of merely 0.0075% per cycle. [ABSTRACT FROM AUTHOR]

[Display omitted] • B/N co-doping rGO/BNNSs heterostructure is prepared by an in-situ reaction strategy. • The heterostructure has fast thermal diffusion and strong LiPSs-blocking capability. • It can significantly enhance the catalytic conversion of both LiPSs and Li 2 S. • The heterostructure-based Li-S cell delivers advanced rate and cycling performances. The practical applications of lithium-sulfur (Li-S) batteries are obstructed by low sulfur utilization and poor cycling stability caused by notorious shuttle effect of soluble lithium polysulfide (LiPSs) and sluggish redox reaction kinetics. Herein, a creative B/N co-doping reduced graphene oxide/boron nitride nanosheets (B/N co-doping rGO/BNNSs) heterostructure prepared by a facile in-situ pyrolysis reaction strategy, is rationally designed as a multifunctional coating for high-performance Li-S batteries. The modified separator with B/N co-doping rGO/BNNSs displays excellent flexibility, thermal conductivity and electrolyte wettability. The superior shielding effect to LiPSs provided by the high density of B-N, B-C and C-N polar bonds and hierarchical pore structures, not only enhance the utilization of sulfur but also prevent the Li-anode from corrosion by LiPSs. Meanwhile, the improved electrochemical kinetics resulting from B/N co-doping sites and rGO/BNNSs heterostructure, effectively promote Li-ions diffusion and catalyze the redox kinetics of Li 2 S and LiPSs. Encouraged by the synergistic effect, the Li-S battery with B/N co-doping rGO/BNNSs coating shows a reversible capacity of 966.6 mAh g−1 at 1C. Upon increased current density of 4C, a desirable initial discharge capacity of 741.5 mAh g-1can be acquired with ultralow capacity decay of 0.015% per cycle after 500 cycles. Even under high sulfur areal loading configuration, the cell still has remarkable cycling stability. The fundamental explorations on inhibiting LiPSs shuttle and promoting various sulfur species conversion demonstrate the great potential of B/N co-doping rGO/BNNSs in practical Li-S batteries. [ABSTRACT FROM AUTHOR]

• Well-honeycombed rGO framework was gained via a PMMA-sphere-assisted template method. • Ultrafine S was uniformly distributed onto the rGO frameworks to form ideal 3D-C/S. • 3D-C/S cathodes for Li-S batteries showed capacity of initial 732 mAh g−1 at 1C. • 3D-C/S cathodes maintained capacity of 442 mAh g−1 at high 4C after 200 cycles. • Their capacity fade rates were 0.16% at 1C and 0.1% at 4C per cycle for 200 cycles. Lithium-sulfur (Li–S) batteries have been recognized as one of the most promising lithium-ion power sources. However, their commercial application is greatly hindered by the incompletely used active materials and unsatisfactory cyclability. Herein, a novel well-honeycombed porous graphene framework (3D-G) was developed using a PMMA-sphere-assisted vacuum filtration method, and used as an advanced sulfur host for enhancing Li–S battery performance. The unique well-honeycombed porous graphene framework not only enhances the electronic conductivity of Li–S cathodes, but also provides numerous active sites for sulfur adsorption. Moreover, the ultrafine sulfur uniformly embedded into the well-honeycombed porous graphene framework increases the utilization of active materials. Benefiting from these synergistic features, 3D-G/S cathodes exhibit excellent electrochemical performance, such as long-cycling stability with a ultra-low capacity fading of 0.099% per cycle over 200 cycles at a high current density, holding great promise for development of practically viable Li–S batteries. [ABSTRACT FROM AUTHOR]