Construction of three-dimensional ordered porous carbon bulk networks for high performance lithium-sulfur batteries

In order to suppress the shuttling of soluble lithium polysulfides in Li-S batteries and increase the conductivity of the sulfur cathode, here we report the design and synthesis of three-dimensional (3D) highly ordered porous carbon bulk network (PCBNs), using silica (SiO₂) nanospheres as removable hard templates and soluble starch as carbon source. After carbonization and template removal, the as-prepared PCBNs composed of interconnected hollow carbon balls exhibit large surface area (447.4 m²/g) and large pore volume (1.567 cm³/g), high graphitization degree and robust framework. Serving as an efficient sulfur host, PCBNs supported sulfur cathode (S@PCBNs with sulfur content of 72 wt%) delivers a high discharge capacity of 760 mA h/g after 150 cycles at 0.1 C and 455 mA h/g after 400 cycles at 1 C. The superior lithium storage properties is attributed to the novel hierarchical microstructure of the PCBNs, in which the large hollow space not only allows high loading of sulfur but also efficiently accommodates the large volumetric expansion. Moreover, the interconnected PCBNs with high conductivity can spatially confine the shuttling of soluble polysulfides and enhance the redox reaction kinetics.