Designing a Novel Electrolyte Na_3.2Hf₂Si_2.2P_0.8O_11.85F_0.3 for All‐Solid‐State Na‐O₂ Batteries

Abstract

their high ionic conductivity, good thermal stability, and high safety. [10,11] β″-Al 2 O 3 was the mostly studied sodium-ion conductor. And it had been successfully used in commercial sodium-sulfur batteries. [12] However, β″-Al 2 O 3 was sensitive to water, and the ionic conductivity decreased significantly after contacting with water, which severely limited its application in sodium-air batteries. Sulfide electrolytes had great advantages in ionic conductivity, but they are very easy to react with air and water. [13,14] NASICON electrolytes Na 1+x Zr 2 Si x P 3−x O 12 (0 ≤ x ≤ 3) had a high ionic conductivity, wide electrochemical window, and insensitive to water vapor, which helped them get a good application potential in sodium-air batteries. [15][16][17][18] In fact, NASICON electrolytes had been used in hybrid system sodium-air batteries. [19][20][21][22][23] However, the research of all-solid-state sodium-air batteries based on NASICON electrolyte was still insufficient and the catalytic mechanism in solid cathode was still unclear.Herein, we prepared an all-solid-state Na-O 2 battery based on elaborately designed NASICON electrolyte Na 3.2 Hf 2 Si 2.2 P 0.8 O 11.85 F 0.3 . Firstly, the conductivity of the electrolyte was regulated by F − -doping, and all the samples Na 3.2 Hf 2 Si 2.2 P 0.8 O 12−x F 2x (x = 0-0.25) were noted as NHSP-F 2x . The results proved that NHSP-F 0.3 electrolyte exhibited the highest ionic conductivity (2.39 × 10 −3 S cm −1 ) and the highest relative density than others. In addition, it is noteworthy that humidity has a significant influence on the performance of battery. The existence of water in atmosphere may change the path of cathodic reaction, which facilitated the generation of soluble discharge product (NaOH) and promoted reversible cycling performance. However, owing to NASICON electrolyte itself being hydrophilic, the water released during charging is unfavorable, and may reduce the sodium or discharge product percolate electrolyte. Therefore, how to ensure the compactness of electrolyte and the hydrophobicity of electrolyte/cathode interface is of great value for the development of all-solid-state sodium-air battery. This study provides important support for the research of all-solid-state sodium-air battery, and also has significant reference value for other solid-state metal-air batteries. Results and DiscussionAs shown in Figure 1a, the prepared electrolyte pellet is white and the diameter is about 1 cm. The NHSP-F 2x (x ≤ 0.25) electrolytes Sodium-air battery has great development potential due to its high energy density and high safety. However, most previous works are based on liquid electrolyte or polymer electrolyte, which will inevitably result in safety hazards such as electrolyte leakage and sodium dendrite growth. Herein, an all-solid-state Na-O 2 battery based on a well-designed NASICON-type electrolyte Na 3.2 Hf 2 Si 2.2 P 0.8 O 11.85 F 0.3 , which has high ionic conductivity (2.39 × 10 −3 S cm −1 ) and excellent chemical stability, is developed. Collabor...

Predicting the Na+ ion transport properties of NaSICON materials using density functional theory and Kinetic Monte Carlo

“…However, the values reported in different studies for the composition with M = Hf 4+ and x = 2.2 also vary, which could be due to similar reasons as those discussed above. 127,128 Besides, similar conductivities for the compounds with M = Zr 4+ , Hf 4+ have been reported in previous studies, which coincide with our results. 6,120,123,127,129 Overall, the good agreement of our results with the literature data conrms the suitability of this method for studying conductivity in NaSCIONtype structures.…”

“…12 Comparison of Na + conductivity s in dependence on (a and b) substitution content x and (c and d) temperature T of Na 1+x M 2 Si x P 3−x O 12 with (a) M = Zr 4+ , (b and c) M = Hf 4+ , and (d) M = Sn 4+ in 10 × 10 × 10 cells. Literature data of experimental studies3,72,74,79,127,128,130 as well as KMC simulations53 are shown.…”

Designing a Quasi-Liquid Alloy Interface for Solid Na-Ion Battery

“…In this work, we chose a NASICON-type Na 3 Hf 2 Si 2 PO 12 with a monoclinic structure as the electrolyte, and the conductivity can reach 1.4 × 10 –3 S cm –2 at room temperature (Figures S4–S6). , The sodium potassium alloy exhibits a good chemical stability with the Na 3 Hf 2 Si 2 PO 12 electrolyte, when we immersed a piece of solid electrolyte in Na–K liquid alloy for 24 h, there is no obvious ion exchange reaction occurred (Figure S7). We should note that the reaction may intensified during work process when interface polarization is enhanced .…”

Recent Progress on Honeycomb Layered Oxides as a Durable Cathode Material for Sodium‐Ion Batteries

“…[14][15][16] Recently, sodium-ion batteries (SIBs) have been put into use gradually for their abundant reserves and relatively good electrochemical performance. [17][18][19][20][21][22][23][24][25][26] What's more, the usage of cheap aluminum foil current collectors (cheaper than copper foil of LIBs) further reduces the production costs of SIBs, making the wide application of SIBs possible to reduce the energy crisis. [27][28][29] As one of the key components, the cathode material concerns the performance as well as cost of SIBs, which includes layered oxides, tunnel oxides, Prussian blue analogues, and polyanionic compounds.…”