General Motors Co has expanded the recall of its Chevrolet Bolt electrical autos as a consequence of a danger of fireplace from the pouch-type lithium-ion battery cells made by South Korea’s LG.
The recall, the second main one involving batteries made by LG Chem’s battery unit LG Energy Solution (LGES) underscores the challenges dealing with battery corporations in making a secure product to energy electrical vehicles.
HOW DOES A LITHIUM-ION BATTERY WORK?
Cells come in several sizes and styles, however most have three key parts: Electrodes, electrolyte and separator.
Electrodes retailer the lithium. The electrolyte carries the lithium ions between electrodes. The separator retains the optimistic electrode from coming in touch with the damaging electrode.
Energy, within the type of electrical energy, is discharged from the battery cell when lithium ions move from the damaging electrode, or anode, to the optimistic electrode, or cathode. When the cell is charging, these ions move in the other way, from cathode to anode.
WHY DO LI-ION BATTERIES POSE A FIRE RISK?
Lithium-ion batteries, whether or not they’re utilized in vehicles or digital gadgets, can catch fireplace if they’ve been improperly manufactured or broken, or if the software program that operates the battery shouldn’t be designed appropriately.
The main weak spot of lithium-ion batteries in electrical vehicles is using natural liquid electrolytes, that are unstable and flammable when working at excessive temperatures. An exterior power equivalent to a crash may result in chemical leakage.
“For EV fires, it is all the time been very troublesome to pinpoint the precise root explanation for the fireplace, as a result of this can be very troublesome to ‘re-enact’ the fireplace incident with the identical circumstances,” stated Kim Pil-soo, automotive engineering professor at Daelim University.
Also authorities, automobile makers and battery makers typically don’t disclose what the precise security danger is.
WHAT CAUSED THE FIRES ON BOLTS AND KONAS?
In February, South Korea’s transport ministry stated some defects had been present in some battery cells manufactured on the LGES China manufacturing facility and utilized in Hyundai Motor’s electrical vehicles, together with the Kona EV. Hyundai’s recall value about 1 trillion gained ($854 million).
GM stated the batteries provided by LG for the Bolt EV and Bolt EUV might have two manufacturing defects – a torn anode tab and folded separator – current in the identical battery cell, which will increase the chance of fireplace.
For a factbox on main battery fires:
ARE POUCH-TYPE BATTERIES MORE VULNERABLE?
All three varieties of lithium-ion batteries at the moment utilized in electrical vehicles – cylindrical, prismatic and pouch-type – are essentially the identical in performance, however every has professionals and cons.
Cylindrical and prismatic batteries are cased in exhausting supplies. Pouch-types use sealed versatile foils and are protected by skinny metallic luggage.
The know-how utilized in cylindrical batteries is outdated and yields constant outcomes. These cells can stand up to excessive inside strain with out deforming. They are additionally cheaper, making them ultimate for mass manufacturing. But they’re heavier and their form stops cells from being packed as densely as with different battery kinds. Tesla Inc principally used cylindrical batteries, some provided by LGES.
Prismatic batteries are thought of safer and lighter than cylindrical cells and, as a result of they’re rectangular, may be extra densely packed. They optimize house higher than cylindrical cells, however are sometimes dearer and have a shorter life cycle. They may swell.
Compared with cylindrical and prismatic cells, pouch-type battery cells enable for lighter and thinner cell fabrication, and design flexibility for various capacities and house necessities for various automobile fashions. However, they’re weak to swelling, and are extra weak in crashes, posing a larger fireplace danger.
GM and Hyundai Motor use pouch battery cells from LG Energy Solution (previously LG Chem). Volkswagen stated earlier this yr it might shift away from pouch-style cells made by LG and SK Innovation Co Ltd to prismatic know-how.
ARE THERE OTHER SOLUTIONS?
Companies equivalent to China’s BYD Co produce EV battery cells that use lithium iron phosphate cathodes, that are much less susceptible to catching fireplace, however should not capable of retailer as a lot vitality as customary cells that use nickel cobalt manganese cathodes.
Others together with GM are testing totally different chemistries equivalent to nickel-cobalt-manganese-aluminum (NCMA) know-how, which use much less cobalt, making the cells extra secure and cheaper.
Chinese battery maker CATL unveiled final month a sodium-ion battery that doesn’t comprise lithium, cobalt or nickel.
A variety of corporations together with Toyota Motor Corp are additionally growing battery cells with solid-state electrolytes, which might decrease overheating points and fireplace dangers, however might take one other three to 5 years to commercialize.