Hierarchical Free‐Standing Carbon‐Nanotube Paper Electrodes with Ultrahigh Sulfur‐Loading for Lithium–Sulfur Batteries

The rational combination of conductive nanocarbon with sulfur leads to the formation of composite cathodes that can take full advantage of each building block; this is an effective way to construct cathode materials for lithium–sulfur (Li–S) batteries with high energy density. Generally, the areal sulfur-loading amount is less than 2.0 mg cm−2, resulting in a low areal capacity far below the acceptable value for practical applications. In this contribution, a hierarchical free-standing carbon nanotube (CNT)-S paper electrode with an ultrahigh sulfur-loading of 6.3 mg cm−2 is fabricated using a facile bottom–up strategy. In the CNT–S paper electrode, short multi-walled CNTs are employed as the short-range electrical conductive framework for sulfur accommodation, while the super-long CNTs serve as both the long-range conductive network and the intercrossed mechanical scaffold. An initial discharge capacity of 6.2 mA·h cm−2 (995 mA·h g−1), a 60% utilization of sulfur, and a slow cyclic fading rate of 0.20%/cycle within the initial 150 cycles at a low current density of 0.05 C are achieved. The areal capacity can be further increased to 15.1 mA·h cm−2 by stacking three CNT–S paper electrodes—resulting in an areal sulfur-loading of 17.3 mg cm−2—for the cathode of a Li–S cell. The as-obtained free-standing paper electrode are of low cost and provide high energy density, making them promising for flexible electronic devices based on Li–S batteries.