Title: Safety and Quality Issues of Counterfeit Lithium-Ion Cells
Authors: Tapesh Joshi, Saad Azam, Daniel Juarez-Robles, and Judith A. Jeevarajan*
First author’s institution: UL Research Institutes
Cover image source: Raimond Spekking
From consumer electronics, to cars, to storing renewable energy for the grid, lithium-ion batteries have enjoyed immense popularity coupled with decreasing costs. This popularity, however, has attracted counterfeiters who sell battery cells without the same performance metrics or safety profile as established suppliers, often through online sales with misleading brand information.
Lithium ion batteries have two major safety mechanisms. One is a polymer on the ends of the battery with a positive temperature coefficient. If the battery begins to heat up, for example because there was an external short circuit that is forcing unexpected current through the battery, this polymer will increase in temperature. The increase in temperature causes the conductivity of the polymer to drop rapidly and slows the current. The second is a current intercept device. This is two disks connected loosely to the cell by a small point in their center. If the battery starts creating gases because of a runaway reaction, the disks will be pushed away from the cell. This will stop the current. Without these devices, batteries may experience catastrophic failure or even catch fires.
In a recent paper in ACS Energy Letters tested 3 lithium ion batteries. One was from an established manufacturer and two were counterfeits. Testing the capacity of the counterfeits revealed that they performed far worse than was claimed. In some cases, the claimed capacity was greater than possible for a battery of the size purchased. They also noticed changes in the dimensions and materials of the cell and changes in the font or wording included on the counterfeit cells. The counterfeit cells were found to be lacking both the positive temperature coefficient and the current intercept device.
Figure 1: Lithium ion batteries like this one have multiple components when fully assembled to protect from safety hazards (Source).
The cells were then tested under conditions that could cause failure. When the cells were overcharged, the legitimate cell did not exhibit any failure or safety hazards, but the two counterfeit cells leaked electrolyte and produced smoke. When they were subjected to a short circuit, the high-quality cell heated up moderately before stabilizing, but the low quality cells heated up considerably and leaked contents and caught fire respectively.
To avoid the safety hazards of counterfeit cells, the authors recommend those who are capable of doing so test the power density and capacity of cells to verify they match the legitimate producers metrics and that users be wary of signs of counterfeiting including changes in text or font or size of the battery.