Recently, research group from Xiamen University led by the iChEM researcher Prof. Nanfeng Zheng and Prof. Xiaoliang Fang developed a novel carbon-sulfur cathode for lithium-sulfur (Li-S) batteries. They successfully synthesized 3D hierarchical porous graphene-like nanosheets as the sulfur host materials for high-performance Li-S batteries. This work has recently been published as a cover article in Adv. Funct. Mater. (Adv. Funct. Mater. 2016, 26, 8952-8959).

Li-S batteries have attracted great interest owing to their high theoretical capacity of 1675 mAh g^-1 and low costs. Until now, the practical application of Li-S batteries is still suffering from several problems of the sulfur cathode, including the low conductivities of sulfur, the capacity loss induced by the dissolution of polysulfide intermediates, and the large volumetric change of sulfur during charge/discharge process. In past few years, the utilization of porous carbon nanomaterials as hosts for sulfur loading have been considered to be one of the most promising route to overcome these problems. It is noteworthy that most of the reported carbon-sulfur cathodes were constructed with the low sulfur content (< 70 wt%), which offset the energy density advantage of sulfur cathodes. unfortunately, the high loading of insulating sulfur inevitably leads to low specific capacities, poor rate properties, and rapid capacity loss.

To address this challenge, the team led by Profs. Nanfeng Zheng and Xiaoliang Fang designed a facile templating route to fabricate hierarchical porous carbon rods constructed by vertically oriented porous graphene-like nanosheets (HPCR). Compared with the 1D porous microrods and 2D porous nanosheets, 3D hierarchically structured HPCR can significantly improve the sulfur utilization due to its high specific surface area (2226 cm² g^-1), ultralarge pore volume (4.3 cm3 g^-1), and ideal ion transfer pathways. When used as sulfur cathode, the HPCR-S composite with 78.9 wt% sulfur exhibits excellent rate performance (646 mAh g^-1 at 5 C, 1 C = 1675 mA g^-1) and cycling stability (700 mAh g^-1 after 300 cycles at 1 C). Even with a sulfur content of 88.8 wt%, the HPCR-S composite still delivers a good rate performance (545 mAh g^-1 at 3 C) and cycling stability (632 mAh g^-1 after 200 cycles at 1 C). Since the overall sulfur content in the cathode reached 71 wt%, the corresponding volumetric capacity is calculated to be 880 mAh cm^-3 after 200 cycles at 1 C. This work not only opened new opportunities for high-energy-density Li-S batteries, but also provided promising materials for other research fields, such as supercapacitors, catalyst supporters, and pollutant removal.

This work was supported by MOST of China, NSFC, State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Engineering Research Center for Nano-Preparation Technology of Fujian Province.

The link to this paper: http://onlinelibrary.wiley.com/doi/10.1002/adfm.201601897/epdf