Investigation on the Structure and Properties of Na3.1Zr1.55Si2.3P0.7O11 as a Solid Electrolyte and Its Application in a Seawater Battery

Wooseok Go; Jongwoo Kim; Jinho Pyo; Jeffrey B Wolfenstine; Youngsik Kim

doi:10.1021/acsami.1c17338

Investigation on the Structure and Properties of Na_3.1Zr_1.55Si_2.3P_0.7O₁₁ as a Solid Electrolyte and Its Application in a Seawater Battery

ACS Appl Mater Interfaces. 2021 Nov 10;13(44):52727-52735. doi: 10.1021/acsami.1c17338. Epub 2021 Oct 27.

Authors

Wooseok Go¹, Jongwoo Kim¹, Jinho Pyo¹, Jeffrey B Wolfenstine², Youngsik Kim^{1

3}

Affiliations

¹ School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 44919, Republic of Korea.
² Solid Ionic Consulting, Seattle, Washington 98115, United States.
³ Energy Materials and Devices Lab, 4TOONE Corporation, UNIST-gil 50, Ulsan 44919, Republic of Korea.

PMID: 34705430
DOI: 10.1021/acsami.1c17338

Abstract

The ionic conductivity, bend strength, and electrochemical performance in a seawater battery (SWB) of an Na_3.1Zr_1.55Si_2.3P_0.7O₁₁ (vA-NASICON) solid electrolyte were compared to those of Na₃Zr₂Si₂PO₁₂ (H-NASICON). vA-NASICON exhibited three times higher total ionic conductivity (8.6 × 10^-4 S/cm) than H-NASICON (2.9 × 10^-4 S/cm). This is due to the higher bulk ionic conductivity and lower grain boundary resistance of vA-NASICON. The higher bulk conductivity of vA-NASICON is a result of its higher Na content, leading to a larger concentration of charge carriers and/or the formation of a higher conductive rhombohedral phase. The lower grain boundary resistance of vA-NASICON is a result of its larger grain size and reduced ZrO₂ content. The bend strength of vA-NASICON (95 MPa) was 30% higher than that of the H-NASICON ceramic. The higher bend strength of vA-NASICON was attributed to its reduced ZrO₂ secondary phase (1.1 vol %) compared to that of H-NASICON (2.6 vol %). When the vA-NASICON ceramic was tested in the SWB as a solid electrolyte, an 8.27% improved voltage efficiency and 81% higher power output were demonstrated, compared to those of H-NASICON, as a result of its higher total ionic conductivity and mechanical strength. At the same time, the vA-NASICON membrane revealed comparable cycle life (1000 h) to that of H-NASICON. These results suggest that vA-NASICON can be a better alternative than H-NASICON for use in the SWB.

Keywords: NASICON; ceramic; ionic conductivity; seawater battery; solid electrolyte.