Three-Dimensional Carbon Current Collector Promises Small Sulfur Molecule Cathode with High Areal Loading for Lithium–Sulfur Batteries

With the high energy density of 2600 W h kg–1, lithium–sulfur (Li–S) batteries have been considered as one of the most promising energy storage systems. However, the serious capacity fading resulting from the shuttle effect hinders its commercial application. Encapsulating small S2–4 molecules into the pores of ultramicroporous carbon (UMC) can eliminate the dissolved polysulfides, thus completely inhibiting the shuttle effect. Nevertheless, the sulfur loading of S2–4/UMC is usually not higher than 1 mg cm–2 because of the limited pore volume of UMC, which is a great challenge for small sulfur cathode. In this paper, by applying ultralight 3D melamine formaldehyde-based carbon foam (MFC) as a current collector, we dramatically enhanced the areal sulfur loading of the S2–4 electrode with good electrochemical performances. The 3D skeleton of MFC can hold massive S2–4/UMC composites and act as a conductive network for the fast transfer of electrons and Li+ ions. Furthermore, it can serve as an electrolyte reservoir to make a sufficient contact between S2–4 and electrolyte, enhancing the utilization of S2–4. With the MFC current collector, the S2–4 electrode reaches an areal sulfur loading of 4.2 mg cm–2 and performs a capacity of 839.8 mA h g–1 as well as a capacity retention of 82.5% after 100 cycles. The 3D MFC current collector provides a new insight for the application of Li–S batteries with high areal small sulfur loading and excellent cycle stability.