A hollow carbon foam with ultra-high sulfur loading for an integrated cathode of lithium–sulfur batteries

Abstract

Lithium–sulfur batteries are promising energy storage system with high energy density, however, for many years, the difficulty in combining good cycling performance and high sulfur loading have impeded their practical application. In this study, an ultra-light flexible carbon foam (MFC) with a 3D interconnected hollow network was prepared through a special heating program from melamine–formaldehyde foam. The MFC can be used as an efficient host material to achieve both ultra-high sulphur loading and good electrochemical performance in lithium–sulphur batteries. Without a conductive additive and a binder, the sulphur loading in the MFC-based cathode could easily reach up to 75%. The MFC contains a high content of N and O strongly absorbing the polysulfides and has a flexible and sparse skeleton accommodating large volume change during electrochemical reactions. To further improve the performance of the eletrode, GO or rGO was used to decorate the MFC skeleton. The MFC-based electrodes with 75% sulfur loading have excellent cycling performance. The initial capacity of the MFC–S, MFC–GO–S and MFC–rGO–S, based on the mass of the whole electrodes, are 1010.7 mA h g⁻¹, 1183.1 mA h g⁻¹ and 1134.6 mA h g⁻¹ at 0.1C, respectively. After the inevitable capacity fading in the first few cycles, the capacity retention is over 95% after 100 cycles compared with the 20th cycle. These results indicate that the carbon foam is an excellent choice for high sulphur loading Li–S batteries.