2020 is never going to be remembered as a good year. As well as the personal health implications of the COVID-19 pandemic, many industries have been hit hard by nationwide lockdowns. This, unsurprisingly, includes the automobile industry, which has experienced a 20% decline in August 2020 compared to 2019. As if that wasn’t enough, the industry has faced additional problems in the electric vehicle market.
With a series of vehicle recalls from high profile auto manufacturers all pointing towards issues with battery overheating, is it time to go back to the drawing board with lithium-ion battery quality control?
The most recent automotive casualty of battery problems is General Motors after five Chevrolet Bolts caught fire. Investigations into the cause are in the early stages, but the fires originated in the batteries in all cases. As a result, GM are recalling almost 69,000 vehicles, covering models built from 2017 to 2019.
After a launch in just May 2020, Ford is recalling thousands of its hybrid Kugas after seven vehicle fires in Europe. The cause was attributed to the close proximity of the battery to the fuel tank, causing fires when the batteries overheated. And BMW and Mini are recalling or halting production of all petrol-electric models that were produced between 20th January and 18th September this year– affecting around 26,700 cars. The company cites battery fire risk as the reason and internal investigations have shown that the issue is due to foreign contaminants sealed into the battery during manufacture. The official statement from BMW reads:
"internal analysis has shown that in very rare cases particles may have entered the battery during the production process. When the battery is fully charged this could lead to a short circuit within the battery cells, which may lead to a fire.”
These issues point the finger at battery manufacturers and shares at LG Chem, the world’s largest EV battery manufacturer, fell by 4% after the GM announcement, and puts other lithium-ion battery manufacturers under an uncomfortable spotlight.
But electric is the way forward. The transport policies of many countries hinge on moving to a largely (if not completely) electric vehicle transport system within the next two decades. So while these problems may have hit consumer and investor confidence in the short term, longer term these issues must be overcome. The market for supplying batteries into EV is set to grow, therefore ensuring the quality and safety of the batteries supplied, especially in the light of market uneasiness, is paramount.
Not all of the investigations into battery fires within EVs have been completed, but the particle contaminant issue that is cited by BMW is a well-known phenomenon. Essentially, metal contaminants within the battery cells penetrate the cathode and the central separator, causing a short circuit within the battery. This causes overheating and ignition due to thermal runaway.
To reduce the likelihood of this mechanism occurring, battery manufacturers check the batteries during manufacture for the presence of metal particles. Typically, this is done using ICP-OES (Inductively coupled plasma atomic emission spectroscopy) or WDX (wavelength-dispersive X-ray spectroscopy). These methods are very good at determining the type and concentration of contaminants within a battery cell. But they are not useful for telling you the actual size and number of the particles. As metal contaminants are a problem over a given size, it’s essential to get a true picture of the size and distribution within the electrode plate, for example, to evaluate the risk of failure.
The EA8000 X-ray particle analyzer by Hitachi High-Tech overcomes the limitations of traditional ICP-OES and WDX techniques and delivers detailed information on the size, number, distribution and elemental type of metallic contaminants within LIB batteries and individual components.
Combining two advanced technologies – X-ray transmission spectroscopy and X-ray fluorescence – the EA8000 delivers high speed, automated analysis of metal contaminants within battery components, including electrode plates, separators and conductive materials, like carbon black. This information can be used for root cause analysis and to determine acceptable levels of particulates within the material. As the analysis is very fast, this technique can be used as a quality control method within routine production.
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To find out how the Hitachi EA8000 can help maintain quality and therefore fire risk in lithium-ion batteries, get in touch to arrange a demo.