A Honeycomb-like Co@N-C Composite for Ultrahigh Sulfur Loading Li-S Batteries.

Abstract

Because of the high theoretical capacity of 1675 mAh g-1 and high energy density of 2600 Wh kg-1, respectively, lithium-sulfur batteries are attracting intense interest. However, it remains an enormous challenge to realize high utilizations and loadings of sulfur in cathodes for the practical applications of Li-S batteries. Herein, we design a quasi-2D Co@N-C composite with honeycomb architecture as a multifunctional sulfur host via a simple sacrificial templates method. The cellular flake with large surface area and honeycomb architecture can encapsulate much more sulfur, leading to high sulfur content (HSC) composites, and by stacking these HSC flakes, a high sulfur loading (HSL) electrode can be realized due to their high layer bulk density. Compared to our previous work in multifunctional Co-N-C composites, the cellular Co@N-C composite displays a distinct enhancement in the sulfur content, sulfur loading, cycle stability, and rate performance. Benefiting from the cellular morphology, a composite with an HSC of 93.6 wt % and an electrode with an HSL of 7.5 mg cm-2 can be obtained simultaneously, which exhibited excellent rate performance up to 10 C (3.6 mg cm-2) and great cycling stability.