Chevy Bolt Fires Has Battery Industry Scrambling To Ensure EV Safety
The battery fires in some Chevrolet Bolt electric vehicles have caused a jolt among the more than 600 companies at this week's The Battery Show in Novi, Mich. near Detroit. Just as automakers step up EV production and try to convince consumers battery-powered vehicles are safe, companies involved in producing and testing cells are digging in to say they're doing everything they can to provide peace of mind among consumers through advance technologies.
“Safety is the number one target of everyone at the show,” said Fabrice Hudry, chief commercial officer at OneD Battery Sciences. “It's a nascent industry and we have to show the world it's can be safer, and should be safer, than an internal combustion engine vehicle.”
Perhaps the industry is simply ahead of itself, said Francis Wang, CEO at NanoGraf, a Chicago-based company developing high-density silicon battery anode material.
“Maybe this is an example, are we moving too fast. It's completely preventable. It's really driven, I think, by cost and excitement over EVs,” said Wang.
General Motors Co. attributes the battery fires in several Bolts to a pair of manufacturing defects by its supplier, LG Chem. Somehow those defective batteries made it into vehicles. GM GM -0.6% describes the defects as “a torn anode tab and folded separator – present in the same battery cell, which increases the risk of fire.” The automaker has recalled all model year 2017-2022 Bolt and Bolt EUV vehicles to replace their battery modules at an expected cost to GM of about $1 billion and paused production.
The key, according to representatives of several companies in the battery industry is to either catch the bad cells before they reach vehicle assembly lines or at least have the means to reduce or prevent thermal events after installation.
Early detection is the first step. At The Battery Show Atlanta-based Inficon Inc. unveiled a new system for detecting leaks in lithium ion battery cells. It's called the ELT 3000.
Leaks in a cell can lead to shortened battery life or fires since electrolytes within the batteries are highly flammable, according to Thomas Parker, Inficon Automotive Sales Market Manager.
Inficon says using a gas analyzer to detect solvents from the electrolyte the ELT 3000 can spot battery leaks 1,000 times smaller than other current system.
As it relates to the type of defect discovered in Bolt’s battery, “Our equipment will not tell you if the anode and cathode separator in here are good but what our equipment will tell you is if these tabs for the anode and cathode, if something is folded or misaligned, or you have a leak channel or the rolled edge isn't perfectly formed it will catch this,” Parker said as he demonstrated the ELT 3000.
Titan Advanced Energy Solutions comes at battery inspection from another angle. The Salem, Mass.-based company uses ultrasonic waves to detect flaws. Working in conjunction with a battery management system, or BMS, Titan's technology takes real time measurements of the ultrasonic signature of a battery and understands the differences in that signature as the battery cycles and then as defects occur, explained Maura Appleberry, technical product manager at Titan.
When the Bolt battery fires were discovered GM advised its customers, among other things, to limit the degree to which they should recharge their vehicles. Titan's Appleberry says her company's technology might relieve customers of that responsibility.
“So some of the recent events that happened the manufacturers have told their customers limit the charging to 80% state of charge. Don't charge all the way to 100%. That would be something we could tell the BMS instead of it being customer enforced. Where we could say, actually we need to ensure that the BMS needs to limit this voltage that it doesn't approach some sort of dangerous condition,” Appleberry said.
Robotics company Yaskawa America Inc. is receiving interest from battery manufacturers for robot-mounted cameras used to inspect batteries before they leave the factory, according to Kyo Nakamura, key account manager.
“Whether it's a manufacturer defect, let's say, the weld is not all the way through or dispensing so the glue is not completely sealed or the battery pack is not completely sealed, we're working with a camera company to inspect those defects,” said Nakamura at his company's display. “Basically you have to teach with something that is OK, not a reject. The camera takes a picture and if it does not match up to the picture that it has it's going to send us a fault message and it's up to the customer when we get an NG signal, no good signal, how do we work with that.”
Preventing battery fires can go as deep as the adhesives used to fuse components in the unit. This year Avery Dennison AVY -0.5% launched a portfolio of battery protection adhesive products aimed at reducing flammability.
“From a thermal runaway protection aspect we're bonding materials that are ceramic or mica, aero gel type of materials which are highly insulative and protective,” said Michael VanHaerents, Avery Dennison business development manager. “If one battery cell were to go bad and catch fire, you're trying to stop those battery cells from propagating to another cell to another cell to another cell and having a catastrophic event.”
Would Avery Dennison's adhesives have prevented fires such as those in the Chevy Bolt? “Yes,” said VanHaerents, “in conjunction with some of the other material manufacturers in ceramics and aero gels we work with.”
He stresses the importance of redundant safety measure since there's always the risk of a manufacturing defect slipping by internal battery management systems.
OneD's Fabrice Hudry is passionate about his company's Sinanode technology which produces silicon nanowires fused directly onto the commercial graphite particles used in the anodes of EV batteries. These technologies “supercharge” the amount of energy stored, the speed of charging, and power delivered.
What's the relationship to preventing battery fires?
“Whatever percentage of silicon in the battery that's one less weight of material that can be flammable and burn. We're talking about silicon representing 20% of the anode in the battery. That would not burn,” said Hudry.
NanoGraf's technology is also centered on silicon to create more energy dense batteries by replacing the more widely used graphite in anodes with silicon. Wang says the batteries offer 29% more run time than graphite-based batteries, and that has the U.S. military interested.
NanoGraf’s Francis Wang says the only way to ensure no batteries with defects reach consumers is to inspect every one of them before they leave the factory. That's the policy for batteries used in medical device implanted in humans, but not so in the cost-conscious auto industry.
“There's manufacturing processes, robot sensors, but what it comes down to is cost,” said Wang. “It's not like we can't do it, it's how much does it cost. I think everybody's been driving to that $100 per kilowatt hour. That's what happens when there's a ton of growth quickly and you're driven to cost and then something like this happens.”
And then there's the actual flat pouch battery form. They became popular at the turn of the 21st century when consumers demanded cellphones and laptop computers that were flat and thin.
“But is it safe for an electric vehicle?” Wang ponders. “Good question. We're gonna find out.”
Ed Garsten Forbes - Senior Contributor
