Abnormally Low Activation Energy in Cubic Na₃SbS₄ Superionic Conductors

Abstract

Inorganic Na-ion superionic conductors play a vital role in all-solid-state Na batteries that operate at room temperature. Sodium thioantimonate (Na3SbS4), a popular sulfide-based solid electrolyte, has attracted serious attention due to its advantages of high ionic conductivity at room temperature and impressive chemical stability under ambient conditions. Much research detailing Na3SbS4 focused on its synthetic approaches and interfacial stability against Na metal, yet, there is limited information elucidating a fundamental understanding of the Na-ion diffusion mechanisms in Na3SbS4 with different crystal structures (e.g., tetragonal and cubic). Herein, we combine real-time electrochemical impedance measurements with theoretical simulations based on density functional theory and in situ quasi-elastic neutron scattering to study the Na-ion conductive properties of Na3SbS4 during its phase transition from a tetragonal to cubic structure. Although there is a slight change in the lattice parameters, the energy barrier for Na-ion diffusion in the tetragonal structure was determined to be much larger (5–10 times) than that in the cubic structure from both theoretical and experimental perspectives. The high degree of symmetry in cubic Na3SbS4 leads to less interatomic correlations between Na and S­(Sb) atoms, a shorter jump distance (2.85 Å), and a larger diffusion coefficient. This research provides insight into understanding the Na-ion diffusion in solid electrolytes with phase transitions and provides fundamental guidance for designing novel solid-state Na-ion conductors.

Preparation and electrochemical properties of ionic-liquid-modified Na3SbS4 membrane composite electrolytes

“…demonstrates the Arrhenius conductivity plot. The activation energy calculated from the fitting result is E a = 0.23 eV, which is in consistent with the value of tetragonal Na 3 SbS 4 reported previously [46,47]. Therefore, Na 3 SbS 4 prepared via the solution method could be tetragonal.…”

Effective Approaches of Improving the Performance of Chalcogenide Solid Electrolytes for All-Solid-State Sodium-Ion Batteries

“…Ion doping and substitution are common methods of material modification (Bo et al, 2016;Kato et al, 2016;Richards et al, 2016;Krauskopf et al, 2017;Rao et al, 2017;Wang et al, 2017;Mahmoud et al, 2019;Wan et al, 2020;Zhang et al, 2020). Cation ion doping into the P site or halogen doping into the S site can introduce vacancies to improve the ionic conductivity of the CSEs (Zhang et al, 2015;Bo et al, 2016;Wang et al, 2016;Krauskopf et al, 2017Krauskopf et al, , 2018aYu et al, 2017).…”

“…Moreover, inorganic solid electrolytes include Na-β-Al 2 O 3 , NASICON (Na super ionic conductor), borohydride, and chalcogenide. At present, chalcogenide solid electrolytes (CSEs) are mainly divided into four categories: Na 3 MS 4 (M = P, Sb) series (Tanibata et al, 2017;Krauskopf et al, 2018a;Noi et al, 2018;Takeuchi et al, 2018;Zhao et al, 2018;Zhang et al, 2020), Na 3 MSe 4 (M = P, Sb) series (Bo et al, 2016;Mahmoud et al, 2019), Na m M x P y X 12 (M = Si, Ge, Sn; X = S, Se; 10 ≤ m ≤ 11; x/y = 1/2 or 2) series (Kato et al, 2016;Richards et al, 2016;Wan et al, 2020), and Na 7 P 3 X 11 (X = O, S, Se) series (Wang et al, 2017). The most common in the Na 3 MS 4 (M = P, Sb) series is Na 3 PS 4 , which has two crystal forms: tetragonal (P −4 21 c; a = b = 0.69520 nm, c = 0.70757 nm) and cubic (I −4 3 m; a = b = c = 0.70699 nm) (Tanibata et al, 2017;Krauskopf et al, 2018a;Takeuchi et al, 2018;Zhao et al, 2018).…”

Heavily Tungsten‐Doped Sodium Thioantimonate Solid‐State Electrolytes with Exceptionally Low Activation Energy for Ionic Diffusion

“…Progress in Na and K metal anodes and related solid‐state ionic conductors [35–37] provide a potential path for safe sodium metal batteries and possibly potassium metal batteries. SSE and all solid state batteries (ASSBs) based sodium thioantimonate (Na 3 SbS 4 ) and related Na 3 PnS 4 (Pn=P, As, Sb) are attracting interest due to their ambient temperature ionic conductivity [36–65] . The undoped Na 3 SbS 4 has been reported to achieve 0.6 mS/cm in its room temperature (RT) tetragonal phase, [66] with markedly increased conductivity occurring in the elevated temperature phases [53, 67] .…”

“…SSE and all solid state batteries (ASSBs) based sodium thioantimonate (Na 3 SbS 4 ) and related Na 3 PnS 4 (Pn=P, As, Sb) are attracting interest due to their ambient temperature ionic conductivity [36–65] . The undoped Na 3 SbS 4 has been reported to achieve 0.6 mS/cm in its room temperature (RT) tetragonal phase, [66] with markedly increased conductivity occurring in the elevated temperature phases [53, 67] . Authors reported that light W‐doping at the Sb sites (Na 2.88 W 0.12 Sb 0.88 S 4 and Na 2.9 W 0.1 Sb 0.9 S 4 ) can stabilize the high temperature cubic structure at ambient temperature, boosting the RT ionic conductivity to 41(±8) mS/cm [36, 37] …”