A highly reversible sodium metal anode by mitigating electrodeposition overpotential

Abstract

Metallic sodium is considered the most likely anode material to replace metallic lithium owing to its high theoretical capacity, abundant reserves, and low cost. However, the uneven deposition and agglomerate deposition of Na often result in low coulombic efficiency and inferior lifetime during cycling. Here, by phosphorizing treatment, a sodiophilic phosphorized copper mesh (PCM) has been achieved as the metallic sodium-host current collector for the first time; then through in situ electrochemical reaction construct, sodiophilic Na–Cu–P composite layer, which has a fast electronic/ionic conductivity and strong adsorption ability with sodium, thereby greatly mitigating electrodeposition overpotential for improving Na plating/stripping behaviors. Meanwhile, the cross-linked mesh skeleton significantly diminishes the local current density, thus achieving highly reversible Na plating/stripping behavior with dendrite-free and “dead Na”-free. Consequently, the PCM electrode can maintain a high coulombic efficiency (∼99.96%) over 1000 cycles at 5 mA cm⁻² and exhibit an ultra-low electrodeposition overpotential from 0.5 mA cm⁻² to 10 mA cm⁻² in a half-cell. Similarly, the symmetrical cell displays superior cycling stability with low overpotential. Furthermore, the PCM@Na anode delivers excellent cycling/rate performance when paired with Prussian blue (PB) cathode in full-cell.