Interest in non-flammable solid-state battery electrolytes continues to grow as they hold promise for batteries with increased safety, reliability, and energy density. They are nonflammable, stable over a wide temperature range, have a large electrochemical window, and potentially allow for the use of metallic Li anodes [1].

One particular solid-state electrolyte is the Lithium-rich anti-perovskite (LiRAP) with the formula Li₃OX where X is a halogen or a mixture of halogens. Conductivities of >1 mS/cm were previously reported [2]. Interest in the material grew as the conductivity varied with different processing conditions thus opening the door to improvement with structura tweaking and optimization [3].

Whenever new a lithium compound is discovered in the battery field, interest in a sodium analog also arises. Na-ion batteries are considered a possible lower-cost alternative to lithium ion batteries due to the abundance of sodium. The conductivity of various Na-rich anti-perovskite (NaRAP) compounds with varying halogens were also previously reported [4]. 

Here we compare different synthesis methods for the Na₃OBr compound, namely conventional cold-pressed sintering and spark plasma sintering. Spark plasma sintering enables a shorter processing time and more tightly-packed, dense pellets [5]. We report that the Na ionic conductivity for Na₃OBr remained at similar values regardless of the synthesis method.

Acknowledgements

This work was supported by the National Science Foundation under grant number ACI-1053575.

References

[1] Thangadurai, V., Pinzaru, D., Narayanan, S., Baral, A. “Fast Solid State Li Ion Conducting Garnet-Type Structure Metal Oxides for Energy Storage”. J. Phys. Chem. Lett., 2015, 6 (2), pp 292–299. doi: 10.1021/jz501828v

[2] Wang, Y, Richards, W. D., Ong, S. P., Miara, L. J., Kim, J. C., Mo, Y., and Ceder, G. “Design principles for solid-state lithium superionic conductors”. Nature Materials, 2015, 14, pp 1026-1031. doi: 10.1038/nmat4369

[3] Deng, Z., Radhakrishnan, B., Ong, S. P. “Rational Composition Optimization of the Lithium-Rich Li3Ocl1-xBrx Anti-Perovskite Superionic Conductors”. Chem. Mater. 2015, 27 (10), pp 3749-3755. doi: 10.1021/acs.chemmater.5b00988

[4] Wang, Y., Wang, Q., Liu, Z., Zhou, Z., Li, S., Zhu, J., Zou, R., Wang, Y., Lin, J., Zhao, Y.  “Structural manipulation approaches towards enhanced sodium ionic conductivity in Na-rich antiperovskites.” J. Power Sources 2015, 293, pp 735–740. doi: 10.1016/j.jpowsour.2015.06.002

[5] Sairam, K., Sonber, J. K., Murthy, T.S.R.Ch., Subramanian, C., Fotedar, R. K., Nanekar, P., Hubli, R.C. “Influence of spark plasma sintering parameters on densification and mechanical properties of boron carbide”. Int. Journal of Refractory Metals and Hard Materials, 2013, 42, pp 185-192. doi: 10.1016/j.ijrmhm.2013.09.004