Enhanced ionic conductivity in Na3Zr2Si2PO12 NASICON-type solid electrolytes by adding Mg2+-ions

• Published in: Journal of alloys and compounds Vol. 988; p. 174327
• Main Authors: Wang, Jiahui, Kang, Jingrui, Guo, Xu, Hu, Shuchen, Tang, Yi, Jin, Li, Wei, Xiaoyong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.06.2024
• Subjects: Bivalent element doping; Ionic conductivity; NASICON; Solid-state electrolytes; Solid-state electrolytes; NASICON; Bivalent element doping; Ionic conductivity
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2024.174327

The unique NASICON-type 3D structure of Na3Zr2Si2PO12 (NZSP) material offers ideal Na+ conductivity at high temperatures, making it a subject of widespread interest among researchers in fields such as solid state batteries and solid state capacitors. However, the low-symmetry monoclinic phase structure and high grain boundary resistance of NZSP limit its ionic conductivity and application at room temperature. In this work, we optimize Na+ conductivity of NZSP by doping bivalent Mg2+ (∼ 2.4 × 10−3 S/cm, when x = 0.25). The analysis reveals that this way increases the content of the R3c phase which has a higher ionic conductivity and reduces grain boundary resistance. Simultaneously, the internal voids of NZSP decrease along with the original square-like grain size. and the more spaces for Na+ transport are provided because the cell volume of NZSP can be effectively enhanced by doping Mg2+. In addition, the doped samples exhibit electronic conductivity 4–5 orders of magnitude lower than their ionic conductivity. This investigation provides some references for the mechanism of ionic conductivity regulation and the technical production of NASICON-type ceramic electrolyte. •Low-valent cation doping can increase Na+ concentration and carrier mobility.•Doping Mg2+ can effectively modulate the rhombohedral phase, increasing their conductivity.•Doping Mg2+ can effectively reduce grain size, and porosity, resulting in compact grain contact and facilitating Na+ conduction between grains.•The doped solid electrolyte remains a great ionic conductor (σionic ∼ 2.4 × 10−3 S/cm and σelectronic < 4.5 × 10−8 S/cm).