In Situ Construction of Sodiophilic Alloy Interface Enabled Homogenous Na Nucleation and Deposition for Sodium Metal Anode

Abstract

The sodium metal anode is a promising anode for the next generation of batteries because of its high specific capacity and abundant resources. However, the poor cyclic stability hinders its practical application. We report a facile strategy of in-situ constructing sodiophilic alloying sites for Na metal anodes by using Zn foil as the current collector, which enables smooth and compact deposition morphology and excellent cyclic stability. Zn current collector and the initial deposited Na generate a NaZn13 alloy interface, which can guide the subsequent plating/stripping behavior of Na. As a result, the sodium metal anode with Zn current collector exhibits ultrahigh stability with Coulombic efficiency (CE) of 99.87% (over 450 cycles at 1 mA cm-2 for 1 mAh cm-2). Furthermore, the impressive capacity retention (98.5% after 40 cycles at 0.5C) in Zn||NVP (Na3V2(PO4)3) batteries suggests anticipated application prospect of Zn current collector in anode-free sodium metal batteries, which opens up a new way for the development of the next generation of safe and efficient sodium metal anodes.

Facilitating Sodium Nucleation in Anode-Free Sodium Batteries

“…This peak does not align with other Na-containing species in the literature or with KLL peaks from elements in the samples, so its origin is unclear. Other works have observed the formation of a NaZn 13 alloy during Na deposition on Zn. , However, the associated Zn peak 1020.8 eV is not present in this experiment and may be due to differences in cycling parameters …”

“…Other works have observed the formation of a NaZn 13 alloy during Na deposition on Zn. 21,54 However, the associated Zn peak 1020.8 eV is not present in this experiment and may be due to differences in cycling parameters. 21 To summarize, the SEI on all CCs contained common species such as NaF, Na 2 O, Zn, and Cu, as well as ZnO and Cu 2 O that were also present depending on the CC.…”

“…21,54 However, the associated Zn peak 1020.8 eV is not present in this experiment and may be due to differences in cycling parameters. 21 To summarize, the SEI on all CCs contained common species such as NaF, Na 2 O, Zn, and Cu, as well as ZnO and Cu 2 O that were also present depending on the CC. As anticipated, as the CCs are washed, no NaPF 6 was identified on any CC.…”

“…To rectify this, the metal must be smoothly deposited to minimize solid electrolyte interphase (SEI) damage, a process which is dependent on widespread nucleation and even growth. ,, As the surface upon which nucleation takes place, the choice of the current collector (CC) material is therefore critical in cell performance. Recent approaches to improve metal nucleation and growth in anode-free cells include seeded or doped CCs, − porous or coated CCs, − solid-state electrolytes, , and alloy formation processes. − Many of these works touch on but do not fully utilize well-established nucleation theories to the greatest benefit for both understanding and improving performance. This work has been developed with these theories as a foundation and highlights their applicability.…”

Na metal anodes for liquid and solid-state Na batteries

“…In an anode-free configuration, the physiochemical properties of the current collector would largely affect the initial Na nucleation process and deposition morphology, which is highly relevant to the electrochemical performance of the batteries. [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] Another rising star is SSNMBs with enhanced energy density and safety, in which the flammable liquid electrolytes are replaced by non-flammable solid-state electrolytes (SSEs) (Fig. 1d).…”