7
In Table 3 we can see LTO releases a lesser amount of
gas compared to the LFP 22650 type cell, but one must
recognize this is a larger type of battery with a displace-
ment volume nearly twice that of the LTO 18650. When
accounting for the unit energy of each cell, the LTO has the
highest amount of gases released, 0.94 L/Wh.
Thermal Runaway Pressures
Table 4 shows the results of maximum pressure measured
during thermal runaway by the DATAQ in addition to the
calculated ratio of free space to cell volume and the maxi-
mum pressure rise rates. All pressure measurements were
absolute. Figure 13 has the same data plotted to show the
inverse power relationship between the pressures observed
and the free space to cell volume. The line at 9.62 bar cor-
responds to the 125-psig limit set for MSHA-approved XP
enclosures. Using this line as a reference, one can determine
that an available free space of about 40 times the volume
of the LTO battery is needed to keep the pressures within
the necessary specifications. However, it was only when the
cells were placed in a 1,175 ml container that the pressure
remained under the 9.62 bar limit for all the observations,
which correlates to a free space per cell volume of 70.
Figure 11. Time plot of pressure rates and moles of vented
gas for a single LTO cell in a 1,175-ml container
Figure 12. Volume of vented gases versus the available free
space within the sealed container
Table 3. Summary of vented gas volumes
Cell type
Average Gas
Volume, L
Average Gas Vol per
Energy, L/Wh
LTO 2.9 0.94
NMC [14] 7.6 0.65
LFP [14] 4.4 0.36
Table 4. Summary of peak thermal runaway pressure
Free Space,
mL
Free Space /
Cell Vol
TR Pressure,
bar
Max Dp/dt,
bar/s
54.5 3.3 42.7 8.52
3.3 39.2 5.98
3.3 39.3 6.39
92.5 5.6 31.8 4.66
5.6 32.0 4.25
5.6 33.0 4.91
168.5 10.2 24.3 3.44
10.2 23.9 3.34
10.2 21.6 2.84
267.5 16.2 21.0 4.68
16.2 17.9 2.85
16.2 17.9 2.46
685.5 41.4 13.1 2.15
41.4 10.8 1.20
41.4 8.1 2.15
1158.5 70.0 5.3 0.51
70.0 5.4 0.46
70.0 5.6 0.56
2376.5 143.7 3.3 0.60
143.7 3.5 0.23
143.7 3.7 0.27
1125.4* 22.7* 14.7* 1.20*
22.7* 14.9* 1.36*
22.7* 14.8* 1.20*
*Triple-cell test
In Table 3 we can see LTO releases a lesser amount of
gas compared to the LFP 22650 type cell, but one must
recognize this is a larger type of battery with a displace-
ment volume nearly twice that of the LTO 18650. When
accounting for the unit energy of each cell, the LTO has the
highest amount of gases released, 0.94 L/Wh.
Thermal Runaway Pressures
Table 4 shows the results of maximum pressure measured
during thermal runaway by the DATAQ in addition to the
calculated ratio of free space to cell volume and the maxi-
mum pressure rise rates. All pressure measurements were
absolute. Figure 13 has the same data plotted to show the
inverse power relationship between the pressures observed
and the free space to cell volume. The line at 9.62 bar cor-
responds to the 125-psig limit set for MSHA-approved XP
enclosures. Using this line as a reference, one can determine
that an available free space of about 40 times the volume
of the LTO battery is needed to keep the pressures within
the necessary specifications. However, it was only when the
cells were placed in a 1,175 ml container that the pressure
remained under the 9.62 bar limit for all the observations,
which correlates to a free space per cell volume of 70.
Figure 11. Time plot of pressure rates and moles of vented
gas for a single LTO cell in a 1,175-ml container
Figure 12. Volume of vented gases versus the available free
space within the sealed container
Table 3. Summary of vented gas volumes
Cell type
Average Gas
Volume, L
Average Gas Vol per
Energy, L/Wh
LTO 2.9 0.94
NMC [14] 7.6 0.65
LFP [14] 4.4 0.36
Table 4. Summary of peak thermal runaway pressure
Free Space,
mL
Free Space /
Cell Vol
TR Pressure,
bar
Max Dp/dt,
bar/s
54.5 3.3 42.7 8.52
3.3 39.2 5.98
3.3 39.3 6.39
92.5 5.6 31.8 4.66
5.6 32.0 4.25
5.6 33.0 4.91
168.5 10.2 24.3 3.44
10.2 23.9 3.34
10.2 21.6 2.84
267.5 16.2 21.0 4.68
16.2 17.9 2.85
16.2 17.9 2.46
685.5 41.4 13.1 2.15
41.4 10.8 1.20
41.4 8.1 2.15
1158.5 70.0 5.3 0.51
70.0 5.4 0.46
70.0 5.6 0.56
2376.5 143.7 3.3 0.60
143.7 3.5 0.23
143.7 3.7 0.27
1125.4* 22.7* 14.7* 1.20*
22.7* 14.9* 1.36*
22.7* 14.8* 1.20*
*Triple-cell test