Double Paddle‐Wheel Enhanced Sodium Ion Conduction in an Antiperovskite Solid Electrolyte (Adv. Energy Mater. 7/2023)

On the Origin of the Non‐Arrhenius Na‐ion Conductivity in Na3OBr

“…Some studies attributed these peaks to melting of the antiperovskite phases and others to anion disordering. [14,16,17,19] Except for this peak, no other peaks were observed in the DSC plot during heating to 300 °C. Additionally, the bulk material remains solid up to 300 °C, which is confirmed by variable temperature synchrotron XRD, Figure 2b, meaning that the peak does not correspond to the melting of Na 3 OBr.…”

“…For antiperovskite compositions with cluster anions like Na 3 O(NO 2 ) and Na 2 (NH 2 )(BH 4 ), deviation from Arrhenius behaviour is often assigned to activation of the cluster anion rotations and correlated motion between these rotations and the translating cation. [17,18] For the compositions with single halide anions, such behaviour is usually attributed to structural instability, which includes phase transitions, order-disorder transitions of the ion sublattice, and crystal melting. [16,24,25] Zheng et al argued that the non-Arrhenius behaviour observed in K 3 OI could be related to the effect of K vacancies on the ion kinetics of the system.…”

On the Origin of the Non‐Arrhenius Na‐ion Conductivity in Na3OBr

“…For antiperovskite compositions with cluster anions like Na 3 O(NO 2 ) and Na 2 (NH 2 )(BH 4 ), deviation from Arrhenius behaviour is often assigned to activation of the cluster anion rotations and correlated motion between these rotations and the translating cation. [17,18] For the compositions with single halide anions, such behaviour is usually attributed to structural instability, which includes phase transitions, order-disorder transitions of the ion sublattice, and crystal melting. [16,24,25] Zheng et al argued that the non-Arrhenius behaviour observed in K 3 OI could be related to the effect of K vacancies on the ion kinetics of the system.…”

“…[ 10 , 11 , 15 ] Interestingly, non‐Arrhenius behaviour resulting in a decrease in activation energy for ion conduction above 250 °C has been observed across different antiperovskite compositions (Li, K and Na). [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ] The origin of this behaviour is not yet well understood. For antiperovskite compositions with cluster anions like Na 3 O(NO 2 ) and Na 2 (NH 2 )(BH 4 ), deviation from Arrhenius behaviour is often assigned to activation of the cluster anion rotations and correlated motion between these rotations and the translating cation.…”

“…For antiperovskite compositions with cluster anions like Na 3 O(NO 2 ) and Na 2 (NH 2 )(BH 4 ), deviation from Arrhenius behaviour is often assigned to activation of the cluster anion rotations and correlated motion between these rotations and the translating cation. [ 17 , 18 ]…”