Steve Gibson from Security Now provided two excellent sources this week explaining what’s happening when lithium ion batteries fail.
From Paul O’Shea, Editor, Power Electronics News interviewing Nadim Maluf, CEO of Qnovo, and Robert Nalesnik, VP of Marketing for Qnovo.
Now, let’s examine one particular manufacturing defect in which a slight misalignment between the anode and cathode occurs during the assembly process. The same structure as above now has the anode layer shifted slightly to the right. At the misaligned edge, the requisite overlap of the anode relative to the cathode is now diminished or even possibly eliminated. The anode/cathode ratio at this spot drops below the requisite limit for ensuring safety. The result is the onset of lithium metal at this edge. The lithium metal forms on the anode edge. As the lithium metal grows in size and thickness, it ultimately punctures the separator and causes an electrical short between the anode and cathode. Boom! There is a catastrophic failure.
The tolerance requirements in the manufacturing of lithium-ion batteries have risen sharply with increasing energy density. Short of using new materials (which still do not exist in commercial deployment), increasing the energy density means reducing all the extra space inside the battery that is not made of anode and cathode materials. These are the only two materials that store energy; n> everything else is just overhead. They are still needed for other functions and safety, but they do not contribute to storing electrical charge. Therefore, battery designers keep reducing this overhead and, in the process, make the manufacturing tolerances even tighter. That is a recipe for many disasters to come unless we start adding a lot more intelligence to the battery to avoid and mitigate these undesired situations.
From the Qnovo blog.