High Sodium-Ion Conductivity in Interlocked Quaternary Chalcogenides Built with Supertetrahedral Building Units

Abstract

Herein, we report the syntheses, structure, Na-ion conductivity, and theoretical investigation of two moisture stable quaternary compounds, Na3ZnGaQ 4 (Q = S, Se). These compounds are synthesized using high-temperature solid-state synthesis routes employing polychalcogenide flux or by metathesis reactions. The crystal structure of these compounds is built up of a three-dimensional (3-D) network of corner-shared supertetrahedral (T2) units, where two such 3-D networks are interlocked. The d-block metal and the main group metal, Ga, occupy the same crystallographic site with a 1:1 ratio, making it a rare form of building unit. Band structure calculations show that both the compounds are wide band gap semiconductors with band gaps of 2.25 and 1.61 eV, respectively, for Na3ZnGaS4 (I) and Na3ZnGaSe4 (II), which are slightly underestimated compared to experimentally determined band gaps of 3.0 and 1.90 eV, respectively. I and II possess ionic conductivities of 3.74 × 10–4 and 0.12 mS/cm with activation energies of 0.42 and 0.38 eV, respectively, at 30 °C. Interestingly, I shows a significantly high ionic conductivity of 0.13 mS/cm at 30 °C upon exposure to air, which could be due to water adsorption on the surface or occlusion in the grain boundaries. Assuming the vacancy-assisted diffusion mechanism for ionic conductance, this difference is consistent with the difference on vacancy formation energies in these compounds, as predicted by DFT calculations. The bond valence sum map indicates that in both structures, the lowest energy diffusion path is one dimensional and it is along the c axis of the unit cell.

Vacancy-controlled quaternary sulfide Na3−xZn1−xGa1+xS4 with improved ionic conductivity and aqueous stability

“…two orders of magnitude higher (0.12 mS cm −1 ) than that of the former (0.37 mS cm −1 ). 40 Such a large difference in Na + conduction cannot be explained solely by a soer anionic sublattice in Na 3 ZnGaSe 4 , because the substitution of S with Se generally leads to a marginal increase in the s ion of SSEs. 26,28,41 For example, Bernges et al found that the concept of "the soer the lattice, the better" does not always hold true in the Li superionic conducting argyrodite Li 6 PS 5−x Se x Br.…”

“…These compounds were initially synthesized to investigate magnetic frustration and for the discovery of new functional materials that benet from unusual structural features. 38,39 Soon aer the introduction of these SSEs, Na + -conducting behaviors in Na 3 ZnGaS 4 and Na 3 ZnGaSe 4 were examined for possible use as Na + -conducting SSEs, 40 and s ion values of 0.37 mS cm −1 and 0.12 mS cm −1 were reported at RT, respectively. The authors addressed that a difference of ca.…”

Solid Li- and Na-Ion Electrolytes for Next Generation Rechargeable Batteries

“…95 Moreover, they also found that Na 3 ZnGaS 4 could have a higher ionic conductivity when exposed to air with a value of 0.13 mS/cm. 95 Figure 9 shows the Arrhenius plot for several solid state sodium-ion conductors. 93…”

“…Balijapelly et al recently revealed novel sulfide-based sodium electrolytes, Na 3 ZnGaS 4 and Na 3 ZnGaSe 4 , which had ionic conductivities of 3.74 × 10 –4 and 0.12 mS/cm at 30 °C, respectively . Moreover, they also found that Na 3 ZnGaS 4 could have a higher ionic conductivity when exposed to air with a value of 0.13 mS/cm Figure shows the Arrhenius plot for several solid state sodium-ion conductors …”

Sulfur-source-dependent phase-selective preparation of Cu3NiInSnS6 nanocrystals and their optical and magnetic properties

“…Multinary metal chalcogenide compounds have received considerable attention owing to their easily tunable structure, composition and morphology, as well as the resulting unique physical and chemical properties, [1][2][3][4][5][6] enabling extensive applications in many fields, such as photovoltaics, [7][8][9] illumination, 10 photocatalysis, [11][12][13] electrocatalysis, [14][15][16] sodium-ion batteries, 17,18 sensors, 3 biology, 19 medical 20 and so on. With the transition from the simplest binary elemental compositions to more complex multiple compositions through doping or alloying, the properties and applications of materials have undergone an interesting evolution, [21][22][23][24] such as ternary I-III-VI 2 group CuInS 2 (CIS) semiconductors, 25 I-III-VI 2 group alloyed Cu(In,Ga)(Se,S) 2 (CIGS) semiconductors, 26,27 and quaternary I 2 -II-IV-VI 4 group Cu 2 ZnSnS 4 (CZTS) semiconductors 28 etc., due to their ability to allow wide band gap modulation, high absorption coefficients, and lower toxicity compared with Cd/Pb compounds.…”