Solid Electrolyte Interphase Engineering by Designing Cobalt‐Doped Ni₃S₂‐NF Anode for Sodium Metal Anode

Abstract Although sodium metal batteries (SMBs) are considered as promising candidates due to the abundant Na resources challenges still exist. In particular, the formation of dendrites caused by an unstable solid electrolyte interphase (SEI) layer can lead to battery short circuits or even fires. To solve the above problem, cobalt‐doped Ni 3 S 2 nanosheets were decorated onto a 3D nickel foam skeleton (Co‐Ni 3 S 2 ‐NF). The successful one‐step hydrothermal synthesis of Co‐Ni 3 S 2 ‐NF was evidenced by X‐ray photoelectron spectroscopic spectra and high‐resolution transmission electron microscopy lattice images. Experimental results showed that Co‐Ni 3 S 2 ‐NF provided a multitude of nucleation sites, stabilized the SEI layer, inhibited dendrites growth, and ensured uniform ions transfer. The aforementioned results were validated by ex situ electron microscopy images as well as optical microscopy images. This improved the cycling stability of SMBs with a high coulombic efficiency after 400 cycles at the condition of 2 mA cm −2 . When assembling Co‐Ni 3 S 2 ‐NF@Na into a full cell with Na 3 V 2 (PO 4 ) 3 , it also demonstrated excellent rate performance showing the outstanding cycling stability. This advancement offers new insights into the development of high performance anodes of SMBs.