Catalytic Pyroprotein Seed Layers for Sodium Metal Anodes.

We report a pyroprotein seed layer (PSL, ∼100 nm in thickness)-coated Cu foil electrode (PSL-Cu) demonstrating highly reversible Na metal storage behavior with a mean Coulombic efficiency (CE) of ∼99.96% over 300 cycles in a glyme-based electrolyte. Via a synergistic effect with the electrolyte, the carbonaceous thin film containing numerous nucleophilic active sites guides the homogeneous Na metal deposition/stripping process with the formation of numerous catalytic seeds, resulting in remarkably stable cycling and a low Na metal nucleation overpotential of ∼10 mV. In addition, the CE deviation values of the PSL-Cu electrode were ∼0.43% in several cell tests, demonstrating its reliable cycling behavior with low cell-to-cell variation. The practicality of PSL-Cu was further demonstrated via full-cell experiments with a polyanion cathode, in which it achieved a high specific power density and energy density of 3,800 W kg-1 and ∼402 W h kg-1, respectively. This work provides a simple process for the fabrication of a Na metal anode.