Hierarchically Porous Multilayered Carbon Barriers for High-Performance Li-S Batteries

As one of the most promising energy storage devices, the practical application of lithium-sulfur batteries is limited by the low electrical conductivity of sulfur and the notable "shuttle effects" of sulfur-based electrodes. In this work, we describe a hierarchically porous N-doped zeolitic imidazolate framework-8 (ZIF-8)-derived carbon nanosphere (N-ZDC) with an outer shell and an inner honeycomb-like interconnected nanosheet network as sulfur host material for high-performance and long-term lithium-sulfur batteries. The N-ZDC serves as multilayered barrier against the dissolution of lithium polysulfides. The porously inner interconnected carbon network of the N-ZDC facilitates the electron and ion transportation, ensures a high sulfur loading, and accommodates a volume expansion of the sulfur species. As a result, the optimized N-ZDC⁴ /S electrodes displayed high initial specific capacities of 1343, 1182, and 698 mAh g^-1 at 0.5, 1, and 2 C, respectively, and an ultraslow capacity decay of only 0.048 % per cycle at 2 C over 800 cycles. Even with a high sulfur loading of 3.1 mg cm^-2 , N-ZDC⁴ /S still delivered a reversible capacity of 956 mAh g^-1 and stabilizes at 544 mAh g^-1 after 500 cycles at 0.5 C, revealing the great potential of the novel carbon nanospheres for energy storage application.