Lithium-ion batteries are everywhere, from electric vehicles to your phone, but the electronics component can fail in big ways. In fact, the battery continues to be a bit of a mystery.
"We are still in a learning process," said Roeland Bisschop, project manager at RISE Research Institutes of Sweden , in a live presentation Tech Briefs presentation this month. "There are still many things that we don't understand about lithium-ion batteries."
Collaborating with industry, academia, and the public sector, RISE Research tests the limits of technologies, including batteries.
When you exceed the safe operating conditions of a cell, you may end up with a thermal runaway, an event characterized by increasingly elevated temperatures.
If pressure builds up in the battery cell, the heat could lead to a rupture in the battery casing, which releases flammable, toxic gases that may or may not ignite.
To reduce these kinds of explosive risks, testing must be performed to ensure these batteries are safe in the event of thermal runaway, says Bisschop, and simulation can fill in the gaps where testing isn't possible.
In a live Tech Briefs presentation titled Reducing Battery Thermal Runaway Risks Through Testing and Simulation, a reader asked:
"How do you ensure that runaway is contained to as few cells as possible and does not go beyond the module?"
Read Bisschop's edited response below.
Roeland Bisschop, Project Manager, RISE: I think it will depend on the combination of both testing and performing simulations, to have an understanding of the characteristics of your specific battery cell that you're using and the challenges that you're facing and if it may fail. Regardless, you should be designing your systems, expecting that one of your cells may fail at some point in time.
When it comes to specifics: One can look at distancing between the cells, applying some heat sinks in your battery modules, or in between the cells, or having some emergency cooling systems. In our specific tests, we looked at injecting fire-suppressant agents directly into a battery pack, and that way we were able to reduce the risk for thermal runaway propagation, but that's kind of a last-resort method.
How have you dealt with thermal runaway risks? Share your questions and comments below.
Transcript
00:00:01 hi everybody my name is Adam remel I'm an application engineer for ozen engineering and today I'm going be giving you a brief introduction to the um to how to model structural deformation and thermal abuse um of a battery using antis tools so some quick uh quick introduction to some to battery and thermal runaway so thermal runaway in
00:00:23 batteries is caused by some sort of external abuse that can be from external heating overcharging um or like what I'm going to show you today some sort of impact uh this causes some internal events um and specifically exothermic reactions within the battery which causes the temperature to increase and um if the exothermic reactions if the heat generation of
00:00:46 those reactions exceed the rate at which the battery can dissipate the heat then you lead to Thermal runaway so um there's three main steps um to model this um it is a very complicated process so we have to break it down so in Step number one we model the structural impact in Step number two we capture the physical characteristics of that damaged Zone and then step
00:01:12 number three we use that information um for the electrochemical thermal modeling so for this example I have a six cell battery and what I'm using is I'm going to using antis workbench LSD to model that that battery being impacted by a a a sphere the sphere is given initial velocity and um just ran into the battery and we look at the deoration caused by
00:01:39 that so here are the results from that simulation uh you can see in the top right the uh displacement caused by the impact and that's really what we're going to use uh to uh look at the damage caused by this impact and see the effects of that so once you do have some sort of damage to the battery this is kind of what's Happening inside the battery uh
00:02:04 so in an ideal battery you have a positive electrode some sort of separator and then the negative electrode and when you undergo some when the battery under go some sort of damage uh you get some sort of break in that separator and that allows a large amount of current um to pass from the positive to negative electrode resulting in those exothermic reactions that I talked about
00:02:25 which causes the temperature to go up so there are several steps uh once we have that uh displacement damage to the battery there are several steps to measure or to simulate the electrochemical thermal simulation part of this problem step number one is to run the thermal abuse model with the msmd battery model turned on um and this
00:02:48 portion is done in fluent um and so this is one of the battery models that fluent has there's a few of them uh but for this example we're going to be showing you how to run the msmd battery model uh so once you have that turned on step number two is that you simulate it until a battery stop condition is met several ways to Define this um but the idea here is that you're looking for when the
00:03:12 battery has lost most of its potential so normally one of the most common ways to model this is when the voltage difference between the positive and Ne negative electrodes uh drops below a certain point for example uh after that point has been met you uh turn off the electric omic and short circuit heat sources or you turn those to zero and you run the thermal
00:03:38 abuse model Standalone um the IDE is here is you're turning off those exothermic reactions you're not looking for those anymore and now we just want to see what happens uh to the temperature as a result of those reactions the next step is that you run the thermal abuse model with a with a small time step and finally when the thermal abuse heat Source terms approach
00:04:00 zero you can increase the time step and solve for the thermal behavior of the cells so this is what that looks like this is a contour of the temperature so we can see at the point of impact the temperature goes up heats up the entire battery um and then over time eventually this starts dropping back down again just due to uh convection here we have a plot of the uh
00:04:30 volume averaged uh temperatures of each cell so we can see that the temperatures of the cells get up to about 900 degrees Kelvin and that's about it so uh thank you for for watching this video has been brought to you by ozen engineering we use physics based simulation to solve multi-disciplinary engineering problems we specialize in FAA cfd and electromagnetics if you'd like to learn
00:04:55 more you can email us at info@ oink.com call our office phone number or visit our website at www.en in.com
