Lithium-Ion
Batteries
Rechargeable lithium-ion (“li-ion”)
batteries (comprised of cells in which lithium ions move from a negative
electrode through an electrolyte to a positive electrode during discharge—and
the other way around when charging) were first described conceptually in the
1970s.
Following initial prototype
development in the 1980s, li-ion batteries became commercially viable in
subsequent decades, and they are now commonly used in a variety of portable
consumer electronic devices, including cell phones, laptops, and tablets.
Li-ion batteries also provide power
for a broad array of automotive, aerospace, and commercial energy applications,
such as electric vehicles (i.e., cars, trucks, buses, and trains), drones and
satellites, and battery energy storage systems (or “BESS”, which enable power
system operators and utilities to store energy—including that generated from
renewable power sources—for later discharge and distribution as demand
necessitates).
Analysts expect that the global size
of the lithium-ion battery market will grow from some $40 billion in 2021 to
over $115 billion by 2030, as users increasingly appreciate li-ion batteries
for their rechargeability, large storage capacity, slow loss of charge when not
in use, and high power to weight ratio.
However, those involved with li-ion
battery production and usage must live with the inherent safety hazards
involved with these batteries, as their electrolytes are flammable by nature,
which can, at high temperatures, lead to fires and explosions.
Thermal
Runaway Can Impact Lithium-ion Battery Safety
In 2019, a battery failure at an
Arizona BESS facility operated by the Arizona Public Service (“APS”) utility
resulted in an explosion that caused serious injuries to a number of
firefighters. The APS site housed over 10,000 lithium-ion battery cells in 27
battery racks within a relatively small battery storage enclosure.
Authorities believe that the
explosion, which they attributed to a chain reaction process knows as “thermal
runaway”, was initiated by a failure in just one li-ion battery cell, which
leaked explosive gas which, in turn, combusted as soon as the firefighters,
responding to an alarm and reports of gas clouds emanating from the structure,
opened the door and let oxygen into the storage enclosure.
Described simply, thermal runaway is
an exothermic reaction in which li-ion battery cell temperatures rise rapidly
in an uncontrollable self-exacerbating fashion. As cell temperatures rise,
flammable and/or toxic gasses are vented (that is, “off-gassed”) from the
battery.
While the gasses may not ignite
immediately, the risk for a potential gas explosion remains. Ultimately,
pressure from the buildup of gas can cause the cell to rupture and release
toxic or explosive gasses (most commonly, carbon dioxide, carbon monoxide,
fluorine, hydrogen, and methane, though there may be others).
An after-incident report
commissioned by APS and released in 2020 listed a number of incidents from
2006-2017 involving thermal runaway events in lithium-ion batteries, including
one on a tugboat in 2012 and another on a Boeing 787 in 2013.
There have been other such events as
well including, memorably, a 2017 fire and explosion in Houston, TX on a train
car that was transporting lithium-ion batteries to a recycling facility. The
explosion broke windows in nearby buildings and, reportedly, sent a chemical
stench throughout downtown Houston.
Off-Gas
Monitoring Can Reduce the Risk of Thermal Runaway
Lithium-ion battery off-gassing, and
subsequent thermal runaway, can occur due to manufacturing defects, mechanical
damage or failures, overvoltage, excessive heat, or improper handling or
storage.
Unfortunately, without reliable gas
detectors in place, there is no sure way to know, until it is too late (i.e.,
when thermal runaway has actually started), that battery cells have in fact
begun to off-gas.
To detect off-gasses, and protect
against thermal runaway, best practices call for manufacturers, researchers,
facility operators, storers, transporters, and others working with li-ion
batteries to install high-quality gas detection monitors.
The gas detectors should
continuously monitor all relevant areas and, if off-gas concentrations are
detected, activate alarms and turn on ventilation systems.
PureAire
Monitoring Systems
PureAire Monitoring Systems’
ST-48 Gas Detector tracks levels of toxic
and/or combustible off-gasses including, but not limited to, carbon dioxide,
carbon monoxide, fluorine, hydrogen, and methane.
The ST-48 is housed in a NEMA 7
explosion-proof enclosure suitable for Class 1, Divisions 1 and 2, Groups A, B,
C, and D, making it ideal for locations (including li-ion storage facilities
and electric vehicle manufacturing plants) where toxic and/or combustible
gasses may accumulate.
PureAire’s ST-48 Gas Detector offers
continuous readings of toxic and/or combustible gasses and features an
easy-to-read screen, which displays current gas levels, in either parts per
million (ppm) or lower explosive limit (LEL), for at-a-glance observation.
In the event of an accumulation of
off-gasses to an unsafe level, the Detector will set off an alarm, complete
with horns and flashing lights, alerting personnel to evacuate the area and
contact appropriate first responders.
Importantly, the PureAire Gas
Detector can be programmed to tie into ventilation systems when off-gas levels
reach a user-selectable ppm or LEL, so that the gasses can be flushed before
human life is jeopardized.