Fast Na ion dynamics in Nb5+ bearing Na3+xZr2Si2+xP1−xO12

Florian Stainer*, Alexander Moritz Kügerl, Lukas Ladenstein, Katharina Hogrefe, Bernhard Gadermaier, H. Martin R. Wilkening

*Corresponding author for this work

Research output: Contribution to conferencePosterpeer-review


Electrochemical systems such as Li-ion batteries have become an integral part, not only in the affluent societies, to power mobile devices. Over the next years they will also be used to stationary store electricity converted from intermittent energy sources such as wind, tidal or solar power. Considering electric vehicles or small electronic devices, Li-ion batteries clearly dominate the market. However, socio-economic considerations do already point away from the Li-ion technology to batteries relying on other charge carriers such as Na+, being small enough to be quite mobile in condensed matter. The high natural abundance of Na allows the development of sustainable large-scale stationary storage systems. Compared to the current ones using Li+, Na-ion batteries are facing the same safety problems if flammable, liquid blends are used as electrolytes. While ceramic, i.e., solid, Na+ electrolytes are expected to be much safer, they usually suffer from significantly lower ionic conductivity as compared to their liquid counterparts. Fortunately, the group of ceramic Na superionic conductors (NASICONs) comprises many intriguing candidates with high Na+ ion conductivities, being almost on a par with some liquids.
NZSP (Na3+xZr2Si2+xP1−xO12) ranks among the most promising NaSICON materials to develop all-solid-state Na+ ion batteries. Importantly, its moderate ionic conductivity in the order of 0.1 mScm-1 can be increased further and fine-tuned by varying its original composition and by taking advantage of clever substitution strategies. Here, we systematically analysed the influence of aliovalent substitution on ionic conductivity of mechanosynthesized Na3+xZr2Si2+xP1−xO12. For this purpose, we partly replaced Zr4+ by Nb5+ and studied the resulting effect on the Na+ ionic transport properties with broadband impedance spectroscopy, electric modulus spectroscopy and nuclear magnetic resonance (NMR) operating at both micro- and macroscopic length scales.
We found that increasing the Na content from x = 0 to x = 0.4 enhances the bulk, that is, the intragrain conductivity, resulting in a total conductivity of approximately 0.4 mS cm−1. The exchange of Zr4+ by 2 % Nb5+ leads to a further significant increase of the bulk conductivity to 6.5 mS cm−1; the total conductivity turned out to be in the order of 1.6 mS cm−1 (20 °C). Local Na ion hopping barriers (0.31(3) eV and values as low as 0.09(1) eV) as determined by 23Na NMR will be compared with those from conductivity measurements being sensitive to macroscopic transport. Importantly, the 23Na NMR spin-lattice relaxation rates (1/T1) reveal a shallow rate peak (log(1/T1) vs 1/T) near room temperature pointing to extremely rapid 23Na spin fluctuations comparable to those in thiophosphates such as Li6PS5Br.
Original languageGerman
Number of pages1
Publication statusPublished - 6 Oct 2022
EventInternational Battery Association Hybrid Conference 2022 - Bled, Bled, Slovenia
Duration: 2 Oct 20227 Oct 2022


ConferenceInternational Battery Association Hybrid Conference 2022
Abbreviated titleIBA 2022
Internet address

Fields of Expertise

  • Advanced Materials Science

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