Multiscale Investigation into Chemically Stable NASICON Solid Electrolyte in Acidic Solutions

Minjie Hou; Xiecheng Yang; Feng Liang; Peng Dong; Yuneng Chen; Jinran Li; Kunfeng Chen; Yongnian Dai; Dongfeng Xue

doi:10.1021/acsami.1c07601

Multiscale Investigation into Chemically Stable NASICON Solid Electrolyte in Acidic Solutions

ACS Appl Mater Interfaces. 2021 Jul 21;13(28):33262-33271. doi: 10.1021/acsami.1c07601. Epub 2021 Jul 2.

Authors

Minjie Hou¹, Xiecheng Yang¹, Feng Liang^{1

2}, Peng Dong¹, Yuneng Chen¹, Jinran Li¹, Kunfeng Chen³, Yongnian Dai¹, Dongfeng Xue⁴

Affiliations

¹ Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China.
² State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, China.
³ State Key Laboratory of Crystal Materials Shandong University, Jinan 250100, China.
⁴ Multiscale Crystal Materials Research Center, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.

PMID: 34213896
DOI: 10.1021/acsami.1c07601

Abstract

Natrium superionic conductor (NASICON) solid electrolyte has been attracting wide attention due to its high ionic conductivity, low cost, and environmental friendliness. In this work, the chemical stability of the NASICON solid electrolyte with the composition of Na₃Zr₂Si₂PO₁₂ was evaluated in acidic solutions with different pH values, and the corrosion mechanism of the NASICON solid electrolyte was revealed at the multiscale level. Variations in bulk impedance, grain boundary impedance, and surface crack impedance with immersion time were determined by an AC impedance method. Comprehensive studies upon scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) etching, X-ray diffraction (XRD), and Raman spectroscopy, the morphological transformation, degradation limit depth, Cl^- penetration effect, and proton exchange between H₃O⁺ and Na⁺ were examined ranging from macro- and meso- to microscales, respectively. With the decrease of the pH of the solution, the exchange rate between H₃O⁺ and Na⁺ protons increases. The lack of Na⁺ within the crystallographic lattice leads to the shrinkage of phosphorus-oxygen tetrahedra, which is the main reason for the decrease of unit cell volume, grain refinement, and surface cracks gradually. This work features multiscale characterizations of crystal structure, grain boundaries, surface morphology changes, and Na⁺ transport, which deepens our physicochemical understanding of solid electrolytes with high chemical stability.

Keywords: NASICON; corrosion mechanism; multiscale; solid electrolyte; stability.