Research Progress on Sodium Chloride Solid Electrolytes

doi:10.15541/jim20250307

Abstract

Abstract:

Sodium-ion batteries are widely considered a promising alternative to lithium-ion batteries owing to their low cost and the abundance of sodium resources. Advances in development and application of all-solid-state sodium-ion batteries (ASSBs) critically depend on the availability of solid electrolytes that combine high ionic conductivity with wide electrochemical stability window. Among various solid electrolytes, chloride solid electrolytes have attracted considerable attention in recent years due to their high ionic conductivity, high oxidation potential and favorable deformability. This review provides a comprehensive overview of development of sodium chloride solid electrolytes, emphasizing interplay of chemical composition, crystal structure and ionic conductivity, and further examining how modification approaches, including cation/anion doping, amorphization and heterostructure engineering, govern their ionic transport behavior. In addition, this review also evaluates the electrochemical stability of sodium chloride solid electrolytes, and their chemical and electrochemical compatibility with common cathode materials, which are crucial for enabling practical cell configurations. The interfacial degradation mechanisms that arise at the interface with sodium metal anode are also analyzed, and recent advances in chloride-based ASSBs are concisely reviewed. Finally, key challenges that hinder practical deployment of chloride-based ASSBs are highlighted, and prospective research directions are proposed, which are expected to provide valuable insights to guide future application of chloride solid electrolytes in energy conversion and storage technologies.

Key words: solid electrolyte, ionic conductivity, chloride, ion transport, solid-state battery, review

CLC Number:

TM911

PENG Dezhao, LI Rui, WANG Wenhong, WANG Zirui, ZHANG Zhizhen. Research Progress on Sodium Chloride Solid Electrolytes[J]. Journal of Inorganic Materials, 2026, 41(4): 409-420.

Figures/Tables 8

Fig. 1 Development timeline of sodium chloride solid electrolytes

Fig. 2 Crystal structures of different sodium chloride solid electrolytes (a) NaMCl4; (b) Na2MCl4; (c) NaMCl6; (d) Na2MCl6; (e) Na3MCl6 (P21/n); (f) Na3MCl6 ($\text{R}\overline{3}$); (g) Na3MCl6 ($\text{P}\overline{3}1\text{c}$); (h) UCl3

Fig. 3 Ion transport properties of NaMCl6 solid electrolytes[52] (a) Arrhenius plots of NaTaCl6 and NaNbCl6; (b, c) Atomic trajectories of Na and Cl atoms from ab initio molecular dynamics (AIMD) simulations for (b) NaTaCl6 and (c) NaNbCl6

Fig. 4 Phase diagram, ion transport properties and structures of Na3-xMCl6-x/Na2-xMCl6-x solid electrolytes[36,59] (a) Phase diagram of NaCl-YCl3-ZrCl4[59]; (b) Transmission electron microscope image of Na0.625Y0.25Zr0.75Cl4.375[59]; (c) Selected area electron diffraction pattern of Na0.625Y0.25Zr0.75Cl4.375[59]; (d) Ionic conductivity and activation energy of NaxZrCl4+x at 25 ℃[36]; (e, f) Na+ and vacancy contents in (e) Na2ZrCl6 and (f) Na0.5ZrCl4.5[36]; (g) Energy profiles along the Na+ transport pathways in Na0.5ZrCl4.5[36]; (h) Crystal structure of Na0.5ZrCl4.5[36]

Fig. 5 Ion transport property and structure of xNa2O2-HfCl4 solid electrolytes[39] (a) Arrhenius plots of xNa2O2-HfCl4; (b) Wavelet-transformed EXAFS contour plots of Na2O2-HfCl4 at Hf L3-edge[39];(c) AIMD-generated structure of amorphous Na2O2-HfCl4 at 500 K[39]

Fig. 6 Ion transport property and structure of xUCl3-(1-x)NaTaCl6 solid electrolytes[69] (a) Arrhenius plots of 0.62Na0.75Sm1.75Cl6-0.38NaTaCl6 and 0.57Na0.75La1.75Cl6-0.43NaTaCl6; (b, c) Transmission electron microscope images of 0.62Na0.75Sm1.75Cl6-0.38NaTaCl6

Fig. 7 Electrochemical stability of sodium chloride solid electrolytes and their compatibilities with electrode materials[36,71,74] (a) Calculated electrochemical stability windows of Na-M-X ternary compounds, including fluorides, chlorides, bromides, iodides, oxides, and sulfides[71]; (b) Calculated reaction energies between different cathodes and solid electrolytes for Na3YCl6 (NYC), Na3YBr6 (NYB), Na3PS4 (NPS), and Na10GeP2S12 (NGPS)[71]; (c) Calculated reaction energies between Na0.5ZrCl4.5, Na0.5ZrCl4F0.5 solid electrolytes and Na3V2(PO4)3 (NVP) cathode, Na anode and Na15Sn4 anode[36]; (d) Impedance evolution of Na9Sn4|Na2.25Y0.25Zr0.75Cl6|Na cells with the time increasing[74]; (e) Zr3d and Y3d XPS spectra of Na2.25Y0.25Zr0.75Cl6 obtained from Na9Sn4|Na2.25Y0.25Zr0.75Cl6|Na cells after charging and discharging[74]

Fig. 8 Electrochemical performance of chloride all-solid-state sodium-ion batteries[36-37,39,59] (a) Schematic illustration of halide-based all-solid-state battery[36]; (b) Long cycling profiles of NaCrO2|Na2.25Y0.25Zr0.75Cl6|Na2(B10H10)0.5(B12H12)0.5|Na9Sn4 cells[59]; (c) Charge-discharge curves of Na3V2(PO4)3|NaTaCl6|Na3PS4|Na15Sn4 cells during cycling[37];(d) Long cycling profiles of Na3V2(PO4)3|NaTaCl6|Na3PS4|Na15Sn4 cells[37]; (e) Charge-discharge curves of Na0.85Mn0.5Ni0.4Fe0.1O2|Na2O2-HfCl4|Na3PS4|Na15Sn4 cells with different rate currents[39] and corresponding (f) long cycling profiles[39]

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