context: For the former, metal Ni and Cu are the common conductivity improvers and can be introduced into the sulfur cathode through a straightforward addition and/or interfusion. For example, Manthiram's group presented a pie-like electrode that consists of nickel foam as a “filling” and an outer carbon shell as a “crust” for facilitating the utilization of sulfur cathodes. Copper powder was introduced into the sulfur cathode by Jia et al. through partially replacing the sulfur contained active material with Cu during the manufacture procedure of the working electrode. Very similarly, Guo and coworkers recently reported the preparation of a CNT/graphene–S–Al3Ni2 cathode with a 3D network structure using 10 wt% Al3Ni2 powder to displace the CNT/graphene–S active material, where the Al in the Al3Ni2 provides an efficient channel for fast electron and ion transfer in the three dimensions, especially along the vertical direction of the cathode. Furthermore, Zheng et al. demonstrated a copper-stabilized sulfur–microporous carbon composite synthesized by uniformly dispersing 10% highly electronically conductive Cu nanoparticles into microporous carbon (MC), followed by wet-impregnation of S. To obtain highly dispersed Cu, commercial MC with a high surface area is first selected as the matrix and carrier. An ultrasonic-assisted multiple wetness impregnation and synchro-dry method is then applied to load 50% Cu(NO3)2 ethanol alcohol solution in MC and evaporate the solvent. This process is repeated until a certain amount of Cu(NO3)2 is added to MC. Finally, Cu nanoparticles anchored in the MC are gained by the reduction of the dry precursor at 200 °C for 1 h under an argon mixed with 5% hydrogen environment. Interestingly, the Cu content in MC can be easily adjusted by controlling the amount of Cu(NO3)2 addition via impregnation times.
answer: sulfur