Ce-Substituted Nanograin Na₃Zr₂Si₂PO₁₂ Prepared by LF-FSP as Sodium-Ion Conductors

Abstract

The urgent need for high-performance solid electrolytes has aroused considerable focus on NASICON ceramics. Optimization of processing routes to dense, defect-free materials has yet to receive sufficient attention to date. Although traditional solid-state reaction methods followed by repetitive ball milling and sintering up to 10 h above 1200 °C are common place, the resulting average particle sizes are usually too large to produce dense, robust structures because of excessive grain growth. In this study, nanopowders (NPs) are produced, which offer a superior opportunity to make dense, high-phasepurity sintered bodies. Here, we report on the effect of sintering conditions on the microstructures and phase of Ce 4+ -substituted NASICON samples, Na 3 Ce x Zr 2−x Si 2 PO 12 (x = 0, 0.1, 0.2, 0.3). NPs permit processing fine-grained solid-state electrolytes with 98% relative density at 1100 °C/5 h. In addition, Rietveld refinement was applied to evaluate 3-D Na-ion diffusion channels among different NASICON samples. Also, it is found that adding 5 at % Ce 4+ does not change the phase structure but dramatically enlarges the Na + diffusion "bottleneck" from 5.4 to 5.6 Å 2 . This may be one reason for these samples to exhibit conductivities of 2.4 × 10 −2 S cm −1 at 140 °C.

NASICON‐Type Na3Zr2Si2PO12 Solid‐State Electrolytes for Sodium Batteries**

“…After calcination at 700°C for 12 h, the powders started to crystallize into the ideal NASICON structure, and a well crystalized monoclinic NASICON was obtained with the ionic conductivity of 1.03 × 10 À 3 S cm À 1 at 25°C. Liu et al [39] prepared Na 3 Ce x Zr 2À x Si 2 PO 12 (x = 0-0.3) nano-powders by Liquid-Feed Flame Spray Pyrolysis (LF-FSP) method, and the as-synthesized Na 3 Ce 0.1 Zr 1.9 Si 2 PO 12 possessed a high total ionic conductivity of 2.4 × 10 À 2 S cm À 1 with a relative high packing density of~98 %.…”

Progress and Challenges for All‐Solid‐State Sodium Batteries

“…A similar effect was achieved by Ce 4+ ‐doped NZSP (Figure 7c). [ 65 ] Other ions, such as Mg 2+ , [ 66 ] Ni, [ 59 ] La 3+ , [ 67 ] Zn 2+ , [ 68 ] Y 3+ , and Nb 5+ , [ 69 ] have also been doped in NZSP, and a high ionic conductivity up to 3.4 × 10 −3 S cm −1 at RT was obtained. The similar effect can also be achieved by shifting the Si/P ratio and increasing the Na content accordingly, [ 70 ] but this has not been systematically investigated.…”

“…Reproduced with permission. [ 65 ] Copyright 2020, American Chemical Society. d) SEM image of microwave‐sintered NZSP electrolytes at 850 °C.…”

Theoretical and Experimental Studies of ion Transport in Mixed Polyanion Solid Electrolytes

“…The fitting of Nyquist plot was carried out using ZView software. For x = 1.5, the equivalent circuit used was based on semicircle phenomena as seen in other reports, 28,59,[84][85][86] with R1 representing the contact resistance, parallel of CPE1 and R2…”