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 S_2-4 molecules into the pores of ultramicroporous carbon (UMC) can eliminate the dissolved polysulfides, thus completely inhibiting the shuttle effect. Nevertheless, the sulfur loading of S_2-4/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 S_2-4 electrode with good electrochemical performances. The 3D skeleton of MFC can hold massive S_2-4/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 S_2-4 and electrolyte, enhancing the utilization of S_2-4. With the MFC current collector, the S_2-4 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.