Gas sensors are poised to see increasing adoption in battery packs in electric vehicles and energy storage systems. Gas sensors, such as those for hydrogen, carbon dioxide, and volatile organic compounds (VOCs), can provide earlier warnings of thermal runaway events in battery packs than conventional sensors allow. This, in turn, can help prevent or mitigate battery fires and explosive events, which remain a significant issue for electric vehicles and energy storage systems.
The battery pack gas sensor market is expected to exceed US$157.1 million by 2036. The new report from market intelligence firm IDTechEx, “Advanced Battery Pack Sensors and Remote Monitoring 2026-2036: Technologies, Markets and Forecasts”, explains more.
An Introduction to Thermal Runaway and Cell Venting
Thermal runaway describes a chain reaction of exothermic reactions that can occur in cells when sufficient temperature is reached or cell damage occurs, for example, through unusually high currents. It can be broken down into several stages, which become apparent as different temperatures are reached within the cell.
To prevent thermal runaway from propagating between cells, thermal management, including cooling systems, is employed; however, these measures are not always successful in containing thermal runaway events. This is especially true for delayed runaway events, in which battery fires occur hours after use, while conventional sensors are non-operational (e.g. when an electric vehicle is parked).
Cell venting is likely the indirect cause of delayed runaway events. During the early stages of thermal runaway, gases are produced through the decomposition of the cell components, including the liquid electrolyte. These gases include hydrogen, carbon dioxide, and various volatile organic compounds, including hydrocarbons and electrolyte vapours.
Cell venting occurs when sufficient gas builds up within a cell, and is a safety measure that reduces cell pressure and prevents further cell damage and complete thermal runaway. However, these gases still have to go somewhere – into the battery pack enclosure.
The build-up of toxic and flammable gases in the battery pack enclosure can lead to corrosion of battery pack packaging and components, as well as potential combustion, which in turn can cause other cells to enter thermal runaway.
Currently, most battery management systems (BMSs) do not track cell venting events or the presence of toxic and flammable gases within the battery pack.
The Solution: Gas Sensors
Gas sensors are well placed as a solution to this problem. By direct detection of dangerous gases, including hydrogen, carbon dioxide and volatile organic compounds, not only can even earlier warning of thermal runaway be provided (up to half an hour before battery fire, compared to five-ten minutes for conventional sensors), but the build-up of these gases within the pack enclosure can be monitored, to prevent dangerous conditions from forming.
Electrolyte vapour detection provides the earliest warning of thermal runaway, as electrolyte vaporisation is one of the earliest stages of thermal runaway.
Typically, sensors operate based on a chemiresistive principle, where the presence of the target gas triggers a reaction on the sensor’s surface, which in turn alters its resistance.
This change in resistance is directly measurable through the application of a small current. The downside of the chemiresistive approach is that sensor lifetime is often limited; however, by using a self-contained reference probe, it can be extended sufficiently to allow for practical use. Nexceris is a major player in this area.
Hydrogen sensing is also a compelling technology, as hydrogen is produced soon after electrolyte vaporisation. Hydrogen sensors are often based on principles of thermal conductivity.
Air with higher concentrations of hydrogen will have a higher thermal conductivity. By measuring the heat loss through a sensor probe and comparing it to a reference sample of air, the concentration of hydrogen can be measured. Amphenol Advanced Sensors is a major player in this space.
Carbon dioxide detection is usually more expensive than hydrogen or volatile organic compound detection, as the best sensors are based on non-dispersive infrared spectroscopy, which requires an infrared light source, miniaturised for use in the battery pack.
However, players in the energy storage systems space, which use specific battery chemistries that produce large volumes of carbon dioxide, have still shown interest in this technology.
Other gas sensing technologies include hydrocarbon sensing and carbon monoxide sensing, but both of these tend to be more niche and require the use of low-lifetime chemiresistors.
Gas Sensor Conclusions
Gas sensors are well-positioned to penetrate the battery pack sensors market. They are expected to see increasing adoption over the next decade, especially once regulations come into place that encourage their usage.
IDTechEx predicts that by 2036, gas sensors will represent over 50% of advanced sensor deployments in battery packs.