Regulation of carbon distribution to construct high-sulfur-content cathode in lithium–sulfur batteries

Lithium–sulfur (Li–S) battery is regarded as one of the most promising next-generation energy storage systems due to the ultra-high theoretical energy density of 2600 Wh kg−1. To address the insulation nature of sulfur, nanocarbon composition is essential to afford acceptable cycling capacity but inevitably sacrifices the actual energy density under working conditions. Therefore, rational structural design of the carbon/sulfur composite cathode is of great significance to realize satisfactory electrochemical performances with limited carbon content. Herein, the cathode carbon distribution is rationally regulated to construct high-sulfur-content and high-performance Li–S batteries. Concretely, a double-layer carbon (DLC) cathode is prepared by fabricating a surface carbon layer on the carbon/sulfur composite. The surface carbon layer not only provides more electrochemically active surfaces, but also blocks the polysulfide shuttle. Consequently, the DLC configuration with an increased sulfur content by nearly 10 wt% renders an initial areal capacity of 3.40 mAh cm−2 and capacity retention of 83.8% during 50 cycles, which is about two times than that of the low-sulfur-content cathode. The strategy of carbon distribution regulation affords an effective pathway to construct advanced high-sulfur-content cathodes for practical high-energy-density Li–S batteries.