Lithium-sulfur (Li-S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg −1 and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co-doped hierarchically porous graphitic carbon network developed through a freeze-drying method (denoted as 3D Cu@ NC-F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li-S batteries. The porous carbon network consisting of 2D cross-linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N-doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC-F network, the in situ grown copper sulfide (Cu x S) embedded within Cu x S@NC/S-F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the Cu x S@NC/S-F composites' electrode exhibits an initial capacity of 1432 mAh g −1 and maintains 1169 mAh g −1 after 120 cycles, with a coulombic efficiency of nearly 100%. development of advanced energy storage systems. Li-S batteries have been considered a new generation energy storage system because of their high theoretical energy density of 2600 Wh kg −1 and theoretical specific capacity of 1675 mAh g −1 , [1] and the merits of safe, low-cost and nonpolluting also make these batteries an exceptional storage system. To date, researchers' knowledge of boosting the energy density of Li-S batteries has resulted in an increase in energy density to 500 Wh kg −1 or more. However, a series of problems inherent in Li-S batteries remain unsolved, such as the low conductivity of sulfur (5 × 10 −30 S cm −1 at 25 °C) and its discharge products (Li 2 S/Li 2 S 2 ), [2] the solubility and shuttle effect of long-chain LiPS intermediates (Li 2 S n , 4 ≤ n ≤ 8), and large volume expansion of ≈80% cause low sulfur utilization, rapid capacity fading, and poor rate-performance and low coulombic efficiency, which still limit practical applications of Li-S batteries. [3,4] At the current stage of Li-S battery research, research has been concentrated on reducing the shuttle effect by advancing electrolyte additives, [5] optimizing cathode structures, [6] using modified separators or bifunctional interlayers, [7,8] and devising protective anode structures, [9] to enable sufficient protection and Lithium-Sulfur BatteriesThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

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3D pomegranate-like TiN@graphene composites as novel sulfur host materials can effectively improve the electrochemical properties of Li–S systems.

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The cheap, environment-friendly and renewable biomass is a promising raw material to prepare the carbon-based composites for the lithium-ion batteries. Herein, the loofah spongederived hollow carbon fibers (LDHCF) were obtained by the activation and carbonization process of biomass loofah sponges. The LDHCF with the porous structure shows the high surface area and active sites. When LDHCF were coated with SnO 2 nanoparticles via the hydrothermal method, the SnO 2 / LDHCF composite as anode material exhibits a reversible capacity of 562.1 mAh g À1 at 0.2 A g À1 after 100 cycles and the columbic efficiency is 99.0% due to the good conductivity, buffer effect of LDHCF, and high theoretical specific capacity of SnO 2 . Such the structure not only proves a novel high-quality carbon template/matrix, but also provides a preferable way to make sustainable anodes in electrochemical energy storage and economical multi-functional carbon-based hybrids available for other practical applications.[a] Y.