Electrical conductivity and porosity in stainless steel 316L scaffolds for electrochemical devices fabricated using selective laser sintering

Highlights: • Metal parts of > 10% porosity can be fabricated using an energy density of 1.50 to 2.00 J/mm². • Two powder sintering mechanisms were observed; partial and complete melting. • Electrical conductivity reduced with porosity. • Poor particle-to-particle sintering is an additional source of internal resistance. • Porosity varies with height of the laser sintered parts; higher at the base and reducing towards the top surface. Battery electrode microstructures must be porous, to provide a large active surface area to facilitate fast charge transfer kinetics. In this work, we describe how a novel porous electrode scaffold, made from stainless steel 316L powder can be fabricated using selective laser sintering by proper selection of process parameters. Porosity, electrical conductivity and optical microscopy measurements were used to investigate the properties of fabricated samples. Our results show that a laser energy density between 1.50–2.00 J/mm² leads to a partial laser sintering mechanism where the powder particles are partially fused together, resulting in the fabrication of electrode scaffolds with 10% or higher porosity. The sample fabricated using 2.00 J/mm² energy density (60 W–1200 mm/s) exhibited a good electrical conductivity of 1.80 × 10⁶ S/m with 15.61% of porosity. Moreover, we have observed the porosity changes across height for the sample fabricated at 60 W and 600 mm/s, 5.70% from base and increasing to 7.12% and 9.89% for each 2.5 mm height towards the top surface offering graded properties ideal for electrochemical devices, due to the changing thermal boundary conditions. These highly porous electrode scaffolds can be used as an electrode in electrochemical devices, potentially improving energy density and life cycle.