Introduction of In-situ Formed Ag Nucleation Layer to Suppress Dendritic Growth in Anode-Free Seawater Batteries

Abstract

The development of sodium metal batteries (SMBs) is severely challenged by sodium dendrite formation, which arises from highly non-uniform Na plating/stripping and parasitic reactions between sodium metal and the electrolyte. In this work, we propose an in-situ strategy to construct a silver (Ag) nucleation interphase on a Ni foam current collector, enabling uniform Na metal formation from an anode-free configuration. The sodiophilic Ag layer provides a high density of nucleation sites that direct homogeneous Na deposition, while the high electronic conductivity of Ag homogenizes the local electric field and accelerates Na⁺ transfer kinetics, collectively enabling smooth Na plating in anode- free batteries.

As a result, the half cells deliver a high Coulombic efficiency (CE) of 99.5% at 1 mA cm⁻² and exhibit excellent cycling stability over 420 cycles, accompanied by a substantial reduced overpotentials and highly reversible Na plating/stripping behavior. As predicted, applying the electrolyte-driven in situ Ag- coating concept to an anode-free seawater battery configuration leads to significantly enhanced electrochemical performance. The anode-free seawater battery exhibits an impressive average capacity retention rate of 93.3% over 100 cycles.

Overall, this study elucidates both the fabrication strategy and the governing role of the Ag nucleation interphase in Na deposition behavior and demonstrates the feasibility of high-areal-capacity anode-free seawater batteries.