Interface Modification and Performance of Sodium Metal Anode Based on Electrolyte Regulation

doi:10.15541/jim20250448

Abstract

Abstract:

Sodium metal is an ideal alternative to lithium metal anodes due to its abundant resources, high theoretical specific capacity, and low redox potential. However, the practical application of sodium metal anodes is still hindered by severe challenges such as dendrite growth and interfacial instability. To address the issues of high solvation energy barriers, sluggish interfacial kinetics, and facile dendrite formation in traditional carbonate-based electrolytes, this study proposes a “strong-weak solvent” strategy. By introducing a weakly solvating cyclic ether solvent, 1,3-dioxolane (DOL), into strongly polar carbonate solvents, combined with the regulatory effect of PF₆^- anions, a stable sodium metal anode interface was constructed. The results show that the low binding energy of DOL significantly reduces the interfacial transport barrier of Na⁺, increasing the ionic conductivity of the electrolyte to 9.31 mS·cm^-1 and effectively suppressing dendrite growth. In the NaPF₆-based electrolyte system, PF₆^- anions, with a concentrated lowest unoccupied molecular orbital (LUMO) energy level of −0.639 eV, preferentially decompose to form an inorganic-rich solid electrolyte interface (SEI) layer, exhibiting excellent interfacial stability and cycling performance. The modified electrolyte maintains a wide electrochemical window (~4.21 V) inherent to the carbonate system while significantly reducing the polarization voltage in Na||Na symmetric cells. A full cell with the Na₃V₂(PO₄)₃||Na configuration demonstrates a high capacity retention of 92.1% after 1600 cycles at 2C rate (1C=120 mA·g^-1). This study provides new insights into achieving highly stable sodium metal anodes through synergistic regulation of the solvation structure and anion chemistry.

Key words: sodium metal anode, cyclic ether, solvation structure, synergistic regulation

CLC Number:

TM912

LIANG Qinqin, MENG Ying, LI Dandan, HAN Fangyuan, YU Min, TANG Bin, LUO Zongchang, LI Jianxin. Interface Modification and Performance of Sodium Metal Anode Based on Electrolyte Regulation[J]. Journal of Inorganic Materials, 2026, 41(9): 1193-1200.

Figures/Tables 7

Fig. 1 (a) Desolvation energies of different solvents and (b) electrostatic potential distributions of solvent molecules THF: Tetrahydrofuran; FEC: Fluoroethylene carbonate; ESP: Electrostatic potential

Fig. 2 Raman spectra of NP, NDP and HNP electrolytes

Fig. 3 (a) LSV curves and (b) Tafel plots of NP and NDP electrolytes

Fig. 4 Interfacial behavior and plating/stripping stability of sodium metal anodes in NP and NDP electrolytes (a) Room-temperature EIS spectra of Na||Na symmetric cells; Current-time profiles of (b) Na|NP|Na and (c) Na|NDP|Na symmetric cells with insets showing impedance spectra of the corresponding cells before and after polarization; (d) Sodium plating/stripping cycling performance with different electrolytes and (e) the corresponding enlarged views; (f) SEM images of sodium metal electrodes after cycling in cells with different electrolytes. Colorful figures are available on website

Fig. 5 Electrochemical kinetics and cycling stabilities of Na||Na3V2(PO4)3 cells in NP and NDP electrolytes (a) EIS spectra; (b) Rate performance; (c) Charge-discharge cycling at room temperature; (d) Charge-discharge voltage profiles at different cycle numbers; Charge-discharge cycling at (e) 60 and (f) −20 ℃. Colorful figures are available on website

Fig. 6 Theoretical calculations and interfacial chemical analysis of DOL-NaPF6 interactions (a) LUMO energy levels of PF6-, DOL and their solvation complex; (b) Binding energies between NaPF6 and DOL before and after interaction, along with the corresponding changes in the LUMO energy levels of NaPF6-DOL; (c) C1s, (d) O1s, and (e) F1s XPS spectra of interfacial Na electrodes of Na‖Na symmetric cells with NP and NDP electrolytes after 50 cycles

Fig. 7 Schematic illustration of solvation structure regulation and the formation of a stable SEI film on sodium metal anodes in the NDP electrolyte

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