This is the prepeer reviewed version of the following CSIC

Catalytic Activity and Efficient Polar Tubular Nanostructure in … Urchin-like Metallic NiCo2Se4 for High Performance Lithium Sulfur Batteries … materials with high conductivity, such as porous structures of graphene,[8] carbon … Fermi level as it corresponds to a metal or a highly degenerated semiconductor (Figure S3 d).