This title appears in the Scientific Report : 2019 

The re-discovery of NASICON materials
Ma, Qianli (Corresponding author)
Tsai, Chih-Long / Tietz, Frank / Guillon, Olivier
Werkstoffsynthese und Herstellungsverfahren; IEK-1
2019
The 22nd International Conference on Solid State Ionics 22nd International Conference on Solid State Ionics, PyeongChang (Korea), 2019-06-16 - 2019-06-21
Conference Presentation
Electrochemical Storage
Despite of huge efforts, the lack of suitable candidate for electrolytes still impedes the development of all-solid-state Na batteries. Na3+xZr2Si2+xP1-xO12 (-0.2 ≤ x ≤ 0.2) are the very first composition series of NASICONs discovered 40 years ago and were reported having a total Na-ion conductivity of ~10-4 S cm-1 at room temperature. In the present study, this composition series is reconsidered and the focusing range of stoichiometry has been varied from x = 0 to x = 0.6. A solution-assisted solid-state reaction method is applied for powder preparation. Surprisingly, a total conductivity of over 5 × 10-3 S cm-1 is achieved for Na3.4Zr2Si2.4P0.6O12 (NZSP) at 25 °C, which is the best value of all reported polycrystalline Na-ion conductors. A bulk conductivity of about 1.5 × 10-2 S cm-1 is also revealed by high frequency impedance spectroscopy up to 3 GHz for NZSP at 25 °C. The parameters influencing the total conductivity are discussed in detail. Benefitted from the superior total conductivity of NZSP, symmetric cells of Na/NZSP/Na and full-ceramic cells of Na3V2P3O12 (NVP)/NZSP/NVP have been fabricated and tested at room temperature with good cycling performance.