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Owing to the high energy density, lithium–sulfur batteries (LSBs) have attracted a lot of attention as a representative of new secondary batteries. However, LSBs also face some serious issues in practical applications such as the large volume expansion of S cathode, shuttle effect of lithium polysulfide (LPSs), and dendrite formation of lithium metal anode. In this work, hollow carbon sphere (HCS) was used as a framework, and CoSe2/Se nanorods were uniformly loaded on the HCS surface to form a 3D heterostructured composite (CS/Se/HCS). When used as an active sulfur host, the HCS is conducive to the transport of electrons and Li+; meanwhile, it can suppress the large volume expansion in the electrochemical performance. CoSe2 can effectively adsorb LPSs and accelerate the transformation of LPSs. We also investigated the effect of CoSe2/Se content on the electrochemical performance of the S electrode. Among different CS/Se/HCS samples, the CS/Se/HCS-0.3/S electrode exhibited the best electrochemical performance; at 1C rate, after 500 cycles, it presents a reversible capacity of 511 mA h g−1. This work provided a new idea for the combination of transition metal selenide and carbon materials, which can be used in LSBs and other energy storage devices. [ABSTRACT FROM AUTHOR]

The "shuttle effect", tardy reaction kinetics and volume change of sulfur cathode limit the wide application of Li-S batteries (LSBs). In this work, a composite of flower-like CoOOH decorating hierarchical porous carbon (CoOOH-HPC) was successfully synthesized and utilized as a sulfur host for LSBs. SEM and TEM images exhibited that the flower-like CoOOH formed by nanosheets was uniformly dispersed on the hierarchical porous carbon which was constructed by carbon spheres and nanotubes. Nitrogen adsorption/desorption isotherm and pore size distribution revealed that the ultrahigh specific surface area and suitable uniform mesopores of the CoOOH-HPC. Benefitting from the perfect combination of CoOOH and HPC, the CoOOH-HPC/S electrode delivered satisfactory electrochemical performance. It remained a discharge capacity of 550.9 mA h g−1 after 270 cycles at 0.5 C, with a low capacity decay rate of 0.017 % per cycle and a stable coulombic efficiency (over 96 %). Besides, the CoOOH-HPC/S electrode with a high sulfur loading of 2.8 mg cm−2 can demonstrate a discharge capacity of 357.91 mA h g−1 after 500 cycles, with the capacity decay rate of 0.08 % per cycle. This work provided a new method for preparing a variety of metal-based compound decorative hierarchical porous carbon composites, which can be used in LSBs and other energy storage and conversion devices. [Display omitted] • A composite sulphur host of CoOOH decorating hierarchical porous carbon (CoOOH-HPC) was synthesized. • The CoOOH-HPC exhibits ultrahigh specific surface area and suitable pore volume. • The perfect structure facilitates wetting of electrolyte and diffusion of electron/Li+ in solid phase • The CoOOH can adsorb the lithium polysulfide through chemical adsorption and accelerate the conversion of the lithium polysulfide to Li 2 S [ABSTRACT FROM AUTHOR]

[Display omitted] • Plum blossom-like CoSe 2 /N-doped carbon nanotubes S host was synthesized. • DFT calculation confirms the catalytic performance of CoSe 2 for Li 2 S x conversion. • The plum blossom-like structure is beneficial to the diffusion of electron/Li+. • DFT calculation confirms the chemical adsorption of CoSe 2 to Li 2 S x. • The CoSe 2 /hNCTs/S cathode delivers satisfactory lithium storage performance. Lithium-sulfur batteries (LSBs) have attracted wide attention as one of the most potential secondary batteries in the next generation. However, the low sulfur utilization, serious "shuttle effect", and large volume expansion of the sulfur cathode restrict the performance of LSBs. Here, CoSe 2 decorated hollow N-doped carbon nanotubes (CoSe 2 /hNCTs) were synthesized firstly, and then the CoSe 2 /hNCTs were used as a sulfur host to prepare a multifunctional CoSe 2 /hNCTs/S cathode. DFT calculations confirm that the CoSe 2 not only efficiently adsorbs lithium polysulfides (LiPSs), but also exhibits good catalytic performance for the conversion of LiPSs. SEM and TEM images indicate that the CoSe 2 uniformly disperses on the surface of the polypyrrole nanotube-derived hNCTs, like plum blossoms. The hNCTs with a morphology of plum blossom branches provide a high conductive network and prohibit large volume expansion during the electrochemical process. And the plum petal-like CoSe 2 on the hNCTs surface acts as a catalyst and an efficient polysulfides trap. The CoSe 2 /hNCTs/S cathode delivers a satisfactory lithium storage performance, which presents reversible capacities of 1156 and 640 mA h g−1 at 0.5 and 5C, respectively. Simultaneously, the cathode demonstrates excellent cycle stability with a slow capacity decay rate of 0.069% per cycle in 1000 cycles at 1C rate. This work provides a new idea for constructing composites of transition metal selenides and carbon materials, promoting the practical applications of LSBs. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multi-functional electrocatalyst of CoOOH/hollow carbon sphere (PHCS) was synthesized. • DFT calculation confirms the catalytic performance of CoOOH for Li 2 S x conversion. • DFT calculation certificates the promotion of CoOOH on OER reaction kinetic. • The CoOOH-PHCS cathode delivers satisfactory lithium storage performance. • The CoOOH-PHCS demonstrates excellent OER and ORR activity in the alkaline electrolyte. Materials with excellent electrocatalytic properties play an important role in the field of electrochemistry. In this work, a multi-function electrocatalyst of cobalt oxyhydroxide decorating homogeneous porous hollow carbon sphere (CoOOH-PHCS) was designed and fabricated. The CoOOH-PHCS can not only be used as an electrocatalyst to inhibit the shuttle effect in Li-S batteries (LSBs), but also can effectively accelerate the reaction kinetics in oxygen reduction/evolution reactions (ORR/OER). Meanwhile, density functional theory (DFT) calculations were performed to investigate the electrocatalytic activity of the CoOOH-PHCS. Benefiting from the synergy effect of CoOOH and PHCS, the CoOOH-HPC/S electrode exhibits a low capacity decay of 0.04% per cycle in 450 cycles at 1C. Meanwhile, the CoOOH-PHCS demonstrates excellent OER and ORR activity in the alkaline electrolyte. This work explores and reveals the application potential of CoOOH in electrocatalytic field. [ABSTRACT FROM AUTHOR]

In this work, a composite of cobalt metal nanoparticles/three-dimensional carbon/reduced graphene oxide (Co-3DC-rGO) was synthesized using corn husk, ZIF-67, and graphene oxide as precursors. The Co-3DC-rGO was used to modify commercial PP to prepare the Co-3DC-rGO/PP separator. The performance of Co-3DC-rGO/PP separator was evaluated in lithium-sulfur batteries (LSBs). SEM images exhibited that a three-dimensional carbon (3DC) skeleton was obtained by corn husk transformation, and the ZIF-67-derived cobalt-decorated carbon dodecahedrons were homogeneously filled into the hierarchical pores of the 3DC structure. TEM images displayed that Co metal nanoparticles can escape from ZIF-67 and scatter on the rGO nano-sheets and 3DC skeleton. Benefitting from the synergy effects of the 3D carbon skeleton, rGO, and Co metal nanoparticles, the electrochemical performance of LSBs with Co-3DC-rGO/PP separator is better than LSBs with commercial PP separator. When tested at 1C, the LSB with Co-3DC-rGO/PP separator presents a high stable reversible capacity of 516.3 mA h g−1 after 500 cycles. This research provides new ideas for the preparation of LSBs separator. [Display omitted] • Co/3D carbon/rGO decorated PP separator was prepared and used in Li-S batteries. • Co/3D carbon/rGO can inhibit the shuttle of lithium polysulfides to the Li anode. • Co/3D carbon/rGO accelerate the conversion of lithium polysulfides to Li2S. • The Li-S battery with Co/3DC/rGO/PP separator delivers excellent electrochemical performance. [ABSTRACT FROM AUTHOR]