Venting is one of the most critical factors when preventing thermal propagation in lithium-ion batteries.
Yet, there are still many misconceptions about venting among manufacturers and engineers.
For example, we often hear the assumption that as long as a battery pack has adequate venting, the risks associated with thermal runaway are sufficiently addressed.
As we like to say around here, “You can’t ignore the physics.” The extreme temperatures inside the battery pack need to go somewhere.
That’s what setting proper venting pathways is all about. They help direct gases and ejecta away from vulnerable components while relieving potentially dangerous pressure buildup.
However, it’s essential that venting is considered from the beginning of your battery pack design and not treated as an afterthought just before your product launch.
Venting is the controlled or uncontrolled release of ejecta (gases, vapor, electrolyte, smoke, heat, or all of the above) from a Li-ion cell or battery pack.
Most battery cells have built-in mechanisms to release pressure when something goes wrong. But simply allowing gases to escape isn't enough. At the pack level, those gases and ejecta need to be directed safely away from neighboring cells and other sensitive components.
Controlled venting is good, but uncontrolled venting usually occurs when internal pressure rises because of:
During thermal runaway, cells can generate extremely hot gases and significant pressure that need somewhere to go.
It's important to remember that venting doesn't necessarily mean a battery has caught fire or entered thermal runaway. However, if those hot gases and ejecta aren't properly managed, they can create additional hazards and potentially trigger thermal runaway in neighboring cells.
So, why exactly do lithium-ion battery packs need to be designed with proper venting?
And more importantly, what’s at stake if they’re not?
There are two things to understand. The first is that venting works in tandem with other factors to prevent thermal runaway from spreading, including insulation, flame suppression, spacing, and more.
Second, while battery manufacturers work hard to prevent thermal runaway, cell failures can still happen. That's why it's important to design battery packs to safely manage these events when they occur.
Like we said—you can’t ignore the physics. That’s why venting is so important.
Without proper venting, pressure can build inside the battery pack, causing the enclosure to bulge, crack, or even rupture. Flammable gases can also accumulate, increasing the risk of fire or explosion if ignited.
However, venting comes with its own challenges. Poorly designed venting pathways can direct hot gases and ejecta toward neighboring cells or introduce oxygen that fuels combustion, potentially making thermal runaway propagation worse.
In severe cases, toxic or corrosive fumes can be released, causing property damage and putting people nearby at risk.
What’s more, even after the initial event appears to be over, damaged cells can remain dangerously hot and potentially reignite, creating additional risks for emergency responders.
That’s why proper venting is so critical. It's not just about letting gases escape. It's about managing pressure, heat, and ejecta to keep a single cell failure from becoming a much bigger problem.
We know how important venting is to battery safety, but what does it look like in practice? How do you ensure that your battery pack design is safe and effective?
Here are the critical factors for proper venting:
The pack includes engineered vents, rupture panels, or valves that open at a controlled pressure—providing a designated pathway for gases to escape rather than allowing the enclosure to rupture unexpectedly.
Hot gases and ejecta are directed toward designated outlets, away from neighboring cells, sensitive components, and people.
The enclosure is designed to prevent excessive pressure buildup that could cause the pack to burst or rupture during a cell-failure event.
Barriers, spacing, insulation, and cooling help keep one venting cell from triggering adjacent cells. Venting alone isn't enough to prevent thermal runaway from spreading but can help manage it if designed properly..
Temperature, voltage, pressure, smoke, or gas sensors can trigger charging shutdown, alarms, or system isolation.
Proper venting may produce hot, flammable, or toxic gases, so venting pathways must account for these hazards while avoiding restrictions or conditions that could make the situation worse.
XTS® can be configured by cell format, spacing, and architecture to fit your unique application:
Here’s how it works: XTS® is a proprietary phase change gel with very high thermal energy absorption around the onset temperature of thermal runaway. When it vaporizes, it has significant cooling capacity while also generating non-flammable gas that acts as a flame suppressant, diluting combustible gases and suppressing flames.
And the best part? XTS® is designed to work alongside engineered venting pathways, helping manage heat and ejecta without unnecessarily restricting gas flow. It helps reduce thermal exposure to neighboring cells, mitigate the effects of thermal runaway, and lower the risk of propagation throughout the battery pack.