With impact safety being a key challenge for the wider deployment of lithium-ion battery technology in electric automobile manufacture, scientists from Oak Ridge National Laboratory in the US have produced a prototype design that reduces the risk of their failure if an accident occurs. The modified design involves the addition of slits along the electrodes of the batteries, helping reduce the amount of housing materials used to protect the batteries from mechanical damage, an approach that is comparatively cheap and doesn’t need significant changes in production.
The study, which was reported in the journal Joule [Naguib et al. Joule (2017) DOI: 10.1016/j.joule.2017.11.003], offers a promising new manufacturing method that will enable portions of lithium-ion batteries to remain functional even if damaged sections have stopped functioning. As impact damage to a battery can create an internal electric short and also large currents that can ignite the battery, causing complete failure, the slits work to break up the electrodes into electrically isolated parts, or small fragments, before a short occurs. If a short still does take place, the fragments limit the current and heating around the short while keeping the rest of the battery functional although at a reduced capacity.
“With such an innovation, device manufacturers can reduce the weight and expense of heavy-duty containers that are normally needed to protect their batteries from mechanical abuse”Nancy Dudney
They tested their model against a regular lithium-ion battery by pressing a large metal ball into each. While the adapted battery became distorted but was able to continue to function at 93% of its original capacity, the same damage to a standard battery resulted in a full discharge and failure. As the electrode slits did not add much in the way of cost to the manufacture of the redesigned lithium-ion battery, and also didn’t mean that substantial changes were necessary for how the battery was produced, the team believe the technology could be scaled up in the future after further testing.
The findings may also offer battery designers another, innovative, way to incorporate safety into batteries without additional weight of enclosures and control devices. As researcher Nancy Dudney said “With such an innovation, device manufacturers can reduce the weight and expense of heavy-duty containers that are normally needed to protect their batteries from mechanical abuse”.
However, only a small number of cells have so far been tested, so many more are required for a wide range of duty cycles, and also to optimize the slit patterns for different types of deformation and scenarios, before the researchers can produce a scaled-up version of the battery.