6
The venting temperature of the cell normally occurred
between 155 and 165 °C with an observed maximum of
about 171 °C. Figure 9 demonstrates the accelerated tem-
perature rise observed by the LTO cells during TR with
observed maximum temperatures of the gases and cell sur-
faces of 265 °C and 450 °C, respectively.
In some instances, during TR, the thermocouple loses
contact with the cell’s surface and the recorded tempera-
ture reflects the gas temperature in the sealed container as
opposed to the actual surface temperature of the cell. In all
recorded data, the temperature never exceeded the autoig-
nition temperature of methane at 600 °C.
Gas Generation
When the LIB’s surface reaches a critical temperature, gas
production from the cell begins, along with excess heat. A
positive feedback loop grows at an exponential rate resulting
in thermal runaway. This crucial temperature was found to
be around 160 °C for these LTO cells. A venting event nor-
mally occurs at this temperature and a sudden release of gas
enters the container. During this time, we see an increase in
the pressure rate resulting from additional moles of gas and
heat that are expelled into the container. In some instances,
it is also possible to measure adiabatic cooling of the cell’s
surface temperature as shown in Figure 10, which depicts a
snapshot of a single LTO cell in a 1,175-ml container.
As the cell continues to heat, releasing more gas and
heat, the pressure in the canister increases rapidly until TR
occurs. Utilizing the free volume of the sealed container
and the ideal gas law, the moles of gas are computed as a
function of heating time from the recorded gas temperature
and pressure. An example of this is shown in a 1,175-ml
container in Figure 11 where spikes in the pressure rate can
be seen as moles of gas are released during the venting and
thermal runaway events with the peak mole released occur-
ring at the latter.
A slight drop in the moles can be seen and is likely due
to the condensation of less volatile gases as the container
and the gas begin to cool. The calculated moles were also
used to estimate the volume of gasses released. The esti-
mated equivalent volume of gases, which were considered
to be at ambient temperature and pressure (22 °C and 1
bar), released by the cells was calculated by taking the vol-
umes generated one minute after peak pressure and sub-
tracting the amount calculated at the venting event. The
resulting gas volumes were plotted against the amount of
free space in the container as shown in Figure 12.
Researchers discovered that, as indicated in Figure 12,
the amount of gas the LTO cells generated tended to rise
with canister volume in agreement with Le Chatelier’s prin-
ciple to a maximum of 3.8 L for a single-cell and 11.0 L for
the triple-cell configurations. An increase in volume results
in a drop in pressure, which favors the side of the chemi-
cal reaction equilibrium with more moles. The triple-cell
configuration also shows the expected volume of gas that
would be anticipated. The average volume of vented gas,
however, is slightly elevated at 3.4 L per cell compared to
the 2.9 L per cell for tests in the single-cell configuration.
Table 3 shows the average results compared to other past
studies conducted in a similar configuration along with the
volume of gasses released per their respective energy levels.
Figure 9. Peak gas and cell temperatures associated with
thermal runway
Figure 10. Pressure and temperature time plots of a single
LTO in a 1,175-ml containera
The venting temperature of the cell normally occurred
between 155 and 165 °C with an observed maximum of
about 171 °C. Figure 9 demonstrates the accelerated tem-
perature rise observed by the LTO cells during TR with
observed maximum temperatures of the gases and cell sur-
faces of 265 °C and 450 °C, respectively.
In some instances, during TR, the thermocouple loses
contact with the cell’s surface and the recorded tempera-
ture reflects the gas temperature in the sealed container as
opposed to the actual surface temperature of the cell. In all
recorded data, the temperature never exceeded the autoig-
nition temperature of methane at 600 °C.
Gas Generation
When the LIB’s surface reaches a critical temperature, gas
production from the cell begins, along with excess heat. A
positive feedback loop grows at an exponential rate resulting
in thermal runaway. This crucial temperature was found to
be around 160 °C for these LTO cells. A venting event nor-
mally occurs at this temperature and a sudden release of gas
enters the container. During this time, we see an increase in
the pressure rate resulting from additional moles of gas and
heat that are expelled into the container. In some instances,
it is also possible to measure adiabatic cooling of the cell’s
surface temperature as shown in Figure 10, which depicts a
snapshot of a single LTO cell in a 1,175-ml container.
As the cell continues to heat, releasing more gas and
heat, the pressure in the canister increases rapidly until TR
occurs. Utilizing the free volume of the sealed container
and the ideal gas law, the moles of gas are computed as a
function of heating time from the recorded gas temperature
and pressure. An example of this is shown in a 1,175-ml
container in Figure 11 where spikes in the pressure rate can
be seen as moles of gas are released during the venting and
thermal runaway events with the peak mole released occur-
ring at the latter.
A slight drop in the moles can be seen and is likely due
to the condensation of less volatile gases as the container
and the gas begin to cool. The calculated moles were also
used to estimate the volume of gasses released. The esti-
mated equivalent volume of gases, which were considered
to be at ambient temperature and pressure (22 °C and 1
bar), released by the cells was calculated by taking the vol-
umes generated one minute after peak pressure and sub-
tracting the amount calculated at the venting event. The
resulting gas volumes were plotted against the amount of
free space in the container as shown in Figure 12.
Researchers discovered that, as indicated in Figure 12,
the amount of gas the LTO cells generated tended to rise
with canister volume in agreement with Le Chatelier’s prin-
ciple to a maximum of 3.8 L for a single-cell and 11.0 L for
the triple-cell configurations. An increase in volume results
in a drop in pressure, which favors the side of the chemi-
cal reaction equilibrium with more moles. The triple-cell
configuration also shows the expected volume of gas that
would be anticipated. The average volume of vented gas,
however, is slightly elevated at 3.4 L per cell compared to
the 2.9 L per cell for tests in the single-cell configuration.
Table 3 shows the average results compared to other past
studies conducted in a similar configuration along with the
volume of gasses released per their respective energy levels.
Figure 9. Peak gas and cell temperatures associated with
thermal runway
Figure 10. Pressure and temperature time plots of a single
LTO in a 1,175-ml containera