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5 – Applications
Exercise 5.14 – The sodium-sulfur battery
A – Solid electrolyte of sodium-sulfur (Na-S) battery
The solid electrolyte used in a sodium-sulfur battery belongs to the family of
sodium β alumina.
1. Give the chemical formula for sodium β alumina.
2. Figure 96 shows the structure of sodium β alumina in perspective view and
in the [001] projection. Specify the majority ionic conducting species and
the structural characteristic that leads to the high ionic conductivity in this
family of electrolytes.
D
E
ĺ F
ĺ F
$O
1D
2
<
9
Figure 96 – Representation of (a) the unit cell of sodium β alumina
(from Kennedy, 1977) and (b) the [001] projection (from Déportes et al., 1994).
3. Comment on figure 97, which shows the activation energy of the ionic
conductivity as a function of ionic radius of the charge carrier. What do we
observe in terms of ionic conductivity if we increase the hydrostatic pressure
on the crystal along the c
→
axis?
5 – Applications
Exercise 5.14 – The sodium-sulfur battery
A – Solid electrolyte of sodium-sulfur (Na-S) battery
The solid electrolyte used in a sodium-sulfur battery belongs to the family of
sodium β alumina.
1. Give the chemical formula for sodium β alumina.
2. Figure 96 shows the structure of sodium β alumina in perspective view and
in the [001] projection. Specify the majority ionic conducting species and
the structural characteristic that leads to the high ionic conductivity in this
family of electrolytes.
D
E
ĺ F
ĺ F
$O
1D
2
<
9
Figure 96 – Representation of (a) the unit cell of sodium β alumina
(from Kennedy, 1977) and (b) the [001] projection (from Déportes et al., 1994).
3. Comment on figure 97, which shows the activation energy of the ionic
conductivity as a function of ionic radius of the charge carrier. What do we
observe in terms of ionic conductivity if we increase the hydrostatic pressure
on the crystal along the c
→
axis?