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By Bill Moore

The AllCells Way of Preventing Lithium Battery Self-Immolation

AllCells Technology Chairman and CEO Said al-Hallaj talks about his company's efforts to prevent lithium-ion battery thermal runaway through the use of a phase-change material that limits the damage to other cells in the pack.

Lithium-ion battery cells pack a lot of energy in a tiny package. While their energy per volume is a fraction of gasoline, if they catch fire, they can do a lot of damage as witnessed by the most recent fire in a stolen Tesla Model S or the near tragic battery fire in Boeing's 787 Dreamliner (see the destroyed battery at the bottom of the page).

Not that gasoline isn't dangerous. It is and there are many tens of thousands of cars destroyed every year when gasoline catches fire. But the last thing Boeing, Tesla or any company using lithium cells, especially large numbers of them in confined spaces, wants is for even one of the cells to short-circuit and going into what's called 'thermal runaway,' where the cell self-immolates and usually takes adjoining cells with it, creating a cascade effect that destroys the battery pack and potentially the vehicle, ship, or plane.

Companies from carmakers to plane builders usually deal with the problem in one of two ways. They use active temperature control measures that rely on the passage of either a tempered fluid or air to keep the batteries from overheating. And given the criticality of lithium-ion cells, especially during the charge cycle, each cell or module - a collection of cells - are separately monitored by the battery management system or BMS.

While these systems are mainly designed to prevent the untimely degradation of the cells due to overcharging or overheating, they don't, by themselves do much to prevent thermal runaway. Once a cell overheats and its internal electrolyte oxidizes, all hell, figuratively, breaks loose with molten metal temperatures reaching that of volcanic lava at more than 1000° C.

This is where AllCells Technology comes into the picture. The spin-off of the Illinois Institute of Technology, or IIT, discovered a proprietary phase change material that absorbs heat and disperses it, so that the damaged cell cannot reach critical temperature. They also physically isolate the cells - in this case, standard 18650 cylindrical cells like those used in laptop computers and in Tesla's Model S and Roadster electric cars. Their honeycomb-like packaging protects the cells, as seen in the image of one of their 'bricks' at the top of this article.

The beauty of AllCell's phase-change system is that it not only reduces the chance of thermal runaway, but provides passive heating and cooling of the cells, keeping them within their preferred temperature range without the need for cumbersome active systems.

In this nearly 45-minute audio dialogue with Dr. Said al-Hallaj, a former professor specializing in alternative energy systems at IIT in Chicago, we talk not only about their technology and the role it is playing in both the two-wheeled EV market and increasingly in the automotive space, we also talk about the challenges of running a battery business in today's skittish financial climate.

The bankruptcy and dime-on-the-dollar sales of companies like A123 and EnerDel have made banks and investors leery of any battery company. This makes it difficult for startups and even established enterprises to find the funds to grow. Even though AllCell doesn't make battery cells, unlike more vertically integrated firms like A123, which was sold to a Chinese company recently, they do build battery packs for clients, like Tesla Motors. As a result, they have become somewhat the victim of their own success as demand for their product is beginning to strain their resources. Al-Hallaj is turning to other funding methods to help the company respond to that demand, which is now starting to come from Europe, as well as North America.

One of those is government funding: in this case, to help develop a phase-change system that works with prismatic or flat pouch-type lithium cells, the kind preferred by most other auto manufacturers. For example, the Chevrolet Volt uses this type of cell, which has to be actively cooled. Early on, several Volts experienced their own 'thermal events' - one burning up, the others smoldering before be extinguished after being crashed by NHTSA testers. GM stepped in and beefed up the crash protection of the critical part o the battery pack. No Volts in private hands have caught fire, to our knowledge.

Beyond mobile applications in automobiles and electric two-wheelers, AllCells is also developing medium-sized grid energy storage units for the frequency regulation market, which with the rapid growth of renewable energy systems promises to be as important if not more so to the battery industry than electric cars.

You can listen to the 45-minute dialogue using the embedded MP3 player below the photo of the Boeing 787 batteries, or right click the link to download the 13.5MB fill if your browser doesn't support HTML5.

Boeing 787 lithium battery self-immolated during a flight in 2013

Times Article Viewed: 6517
Originally published: 20 Jul 2014

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