Lithium−sulfur (Li−S) batteries have attracted considerable attention due to their high specific capacity, low cost, and eco-friendly raw material. However, the insulating property of sulfur and dissolution of lithium polysulfides (LiPSs) lead to rapid capacity decay and low Coulombic efficiency. In this work, we smartly synthesized a composite material as the host material of active S by a facile one-step pyrolysis method. It was composed of in-situ-grown carbon nanotubes (CNTs) and CoP particles inside the porous carbon cages (denoted as CoP-CNT@ C). The CNT networks in porous carbon cages can improve the conductivity of the cathode, while the CoP particles are capable of enhancing the adsorption of LiPSs, thereby effectively mitigating the "shuttle effect". Moreover, the porous structure of the carbon cages could effectively store the elemental sulfur. As a matter of fact, the Li−S battery based on the CoP-CNT@C/S cathode exhibited an ultrahigh initial specific capacity of 1456.8 mAh g −1 at 0.1C and superior performance (663.3 mAh g −1 ) at a high current rate of 3C. It is worth mentioning that a capacity of 473.9 mAh g −1 has been retained after 750 cycles tested at 0.5C, indicating the outstanding stability of the Li−S battery based on the CoP-CNT@C/S cathode. Overall, the CoP-CNT@C composite prepared is promising for the application of Li−S batteries as the host material.

Nanocarbons (NCs) consisting of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) were coated on the surface of nickel foam (NF) via a chemical vapor deposition method. The CNFs formed conductive networks on NF, while the CNTs grew perpendicular to the surface of the CNFs, accompanied with the formation of Ni nanoparticles (Ni NPs) at the end of CNTs. The unique Ni-NCs-coated NF with a porous structure was applied as the three-dimensional (3D) current collector of lithium–sulfur (Li–S) batteries, which provided enough space to accommodate the electrode materials inside itself. Therefore, the 3D interconnected conductive framework of the coated NF collector merged in the electrode materials shortened the path of electron transport, and the generated Ni NPs could adsorb lithium polysulfides (LiPSs) and effectively accelerated the conversion kinetics of LiPSs as well, thereby suppressing the “shuttle effect”. Moreover, the rigid framework of NF would also constrain the movement of the electrode compositions, which benefited the stability of the Li–S batteries. As a matter of fact, the Li–S battery based on the Ni-NCs-coated NF collector delivered an initial discharge capacity as high as 1472 mAh g–1 at 0.1C and outstanding high rate capability at 3C (802 mAh g–1). Additionally, low decay rates of 0.067 and 0.08% at 0.2C (300 cycles) and 0.5C (500 cycles) have been obtained, respectively. Overall, our prepared Ni-NCs-coated NF collector is promising for the application in high-performance Li–S batteries.

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Preparation of GQDs for application in cell imaging.