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USA: Electrical test predicts catastrophic Li-ion cell failure

US scientists claim to have developed a purely electrical test that can warn of impending catastrophic failure in lithium-ion batteries.

“The sensor is based on the researchers’ discovery of an intrinsic relationship between the internal temperature of lithium-ion cells and an easily measured electrical parameter of the cell,” said Johns Hopkins University.

Abused Li-ion cells have infamously exciting failure modes.

“An abnormally high internal cell temperature is a nearly universal manifestation of something going awry with the cell,” said Rengaswamy Srinivasan of the university’s Applied Physics Laboratory. “These changes can occur within seconds, leading to a potentially catastrophic event if corrective measures are not taken immediately. When things start to go wrong inside the cell, time is not on your side.”

Srinivasan and colleagues discovered that there is a phase shift of a few degrees between a “small” alternating current at a few tens of Hz applied to the cell’s terminals, and the resulting voltage waveform.

The phase shift is related by a simple curve to the temperature of the critical electrochemical interface between the electrodes and the electrolyte.

“We discovered that we can measure the temperature of the protective layers between the electrodes and the electrolyte of the battery during normal operation,” said Srinivasan. “These layers are where the conditions that lead to thermal runaway and catastrophic cell failure begin. This discovery enables us to detect potentially unsafe thermal conditions before surface-mounted temperature sensors, which are the current state of the art, are able to register that any change has taken place.”

Publications (below) reveal that temperature has been measured between -20 and 65°C on cells of capacity 2.3, 4.4 and 53Ahr.


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