1
24-087
Thermal Runaway Pressures as a Function of Free
Space in Sealed Containers for Lithium Titanate Cells
Connor B. Brown, Thomas H. Dubaniewicz,
Teresa Barone, and Richard A. Thomas
Pittsburgh Mining Research Division, National
Institute for Occupational Safety and Health,
Pittsburgh, USA
ABSTRACT
Electric vehicles powered by lithium-ion (Li-ion) batteries
are being developed by mining vehicle manufacturers as a
replacement for diesel-powered vehicles. Explosion-proof
(XP) enclosures are frequently employed to enclose elec-
trical ignition sources in gaseous underground mines to
prevent the spread of an internal methane-air explosion to
a nearby explosive atmosphere. Due to thermal runaway
(TR), Li-ion batteries have the potential to cause pres-
surized explosions in an enclosed structure. Past research
has shown the potential for well-confined Li-ion cell TR
to drive pressures beyond the conventional pressure speci-
fication for XP enclosures. Researchers at the National
Institute for Occupational Safety and Health (NIOSH)
used an Accelerating Rate Calorimeter (ARC) to induce
thermal runaway of Lithium Titanate or Lithium Titanium
Oxide (LTO) type 18650 cells enclosed within containers
with various volumes and found an inverse power relation-
ship between the TR pressure and available free space. The
results were similar in magnitude to that of lithium iron
phosphate (LFP) cells, which were used in prior testing.
Temperatures, gas amounts, and TR pressure-rise rates
were also recorded. The data indicate that with enough free
space, the pressures can be lowered below the conventional
pressure specification for XP enclosures.
INTRODUCTION
It has been known that the use of diesel-powered equip-
ment results in generating diesel particulate matter (DPM)
which is a known carcinogen [1]. Past NIOSH research has
shown that underground mineworkers are at particular risk
of DPM exposure [2]. Mine operators can attempt to miti-
gate this risk by providing enough ventilation to dilute the
DPM below safe limits. The hierarchy of controls dictates
the elimination of the DPM source as the best way to con-
trol the risk. For this reason, among others, mine vehicle
manufacturers are developing battery electric vehicle (BEV)
versions of their current equipment. Due to their high
energy density, lithium-ion batteries (LIB) are one of the
most common choices for manufacturers of BEVs when
they transition away from diesel-powered vehicles [3]. Due
to the high energy demands in mining, BEVs utilize a vast
number of individual battery cells wired in series and par-
allel to achieve the necessary voltage and current require-
ments, normally in the range of hundreds of kilowatt-hours
of capacity.
In the consumer sector, there have been several acci-
dents involving a Li-ion battery in everything from small
portable devices to large commuter transports to entire
cargo ships [4–6]. Events of LIB failures in mines have also
occurred [7 &8]. Accidents of lithium-ion battery TR in
mines will become more prominent and more ubiquitous
24-087
Thermal Runaway Pressures as a Function of Free
Space in Sealed Containers for Lithium Titanate Cells
Connor B. Brown, Thomas H. Dubaniewicz,
Teresa Barone, and Richard A. Thomas
Pittsburgh Mining Research Division, National
Institute for Occupational Safety and Health,
Pittsburgh, USA
ABSTRACT
Electric vehicles powered by lithium-ion (Li-ion) batteries
are being developed by mining vehicle manufacturers as a
replacement for diesel-powered vehicles. Explosion-proof
(XP) enclosures are frequently employed to enclose elec-
trical ignition sources in gaseous underground mines to
prevent the spread of an internal methane-air explosion to
a nearby explosive atmosphere. Due to thermal runaway
(TR), Li-ion batteries have the potential to cause pres-
surized explosions in an enclosed structure. Past research
has shown the potential for well-confined Li-ion cell TR
to drive pressures beyond the conventional pressure speci-
fication for XP enclosures. Researchers at the National
Institute for Occupational Safety and Health (NIOSH)
used an Accelerating Rate Calorimeter (ARC) to induce
thermal runaway of Lithium Titanate or Lithium Titanium
Oxide (LTO) type 18650 cells enclosed within containers
with various volumes and found an inverse power relation-
ship between the TR pressure and available free space. The
results were similar in magnitude to that of lithium iron
phosphate (LFP) cells, which were used in prior testing.
Temperatures, gas amounts, and TR pressure-rise rates
were also recorded. The data indicate that with enough free
space, the pressures can be lowered below the conventional
pressure specification for XP enclosures.
INTRODUCTION
It has been known that the use of diesel-powered equip-
ment results in generating diesel particulate matter (DPM)
which is a known carcinogen [1]. Past NIOSH research has
shown that underground mineworkers are at particular risk
of DPM exposure [2]. Mine operators can attempt to miti-
gate this risk by providing enough ventilation to dilute the
DPM below safe limits. The hierarchy of controls dictates
the elimination of the DPM source as the best way to con-
trol the risk. For this reason, among others, mine vehicle
manufacturers are developing battery electric vehicle (BEV)
versions of their current equipment. Due to their high
energy density, lithium-ion batteries (LIB) are one of the
most common choices for manufacturers of BEVs when
they transition away from diesel-powered vehicles [3]. Due
to the high energy demands in mining, BEVs utilize a vast
number of individual battery cells wired in series and par-
allel to achieve the necessary voltage and current require-
ments, normally in the range of hundreds of kilowatt-hours
of capacity.
In the consumer sector, there have been several acci-
dents involving a Li-ion battery in everything from small
portable devices to large commuter transports to entire
cargo ships [4–6]. Events of LIB failures in mines have also
occurred [7 &8]. Accidents of lithium-ion battery TR in
mines will become more prominent and more ubiquitous