Inexpensive sensor gives advance warning of lithium-ion battery failure

Scientists at the Johns Hopkins University Applied Physics Laboratory have developed an inexpensive sensor that can warn of impending catastrophic failure in lithium-ion batteries.

The novel sensor device 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. The team believes the breakthrough could put an end to battery malfunction, which typically results from thermal runaway - a self-perpetuating condition that occurs once a cell reaches a critical temperature. "An abnormally high internal cell temperature is a nearly universal manifestation of something going awry with the cell," explained inventor Rengaswamy Srinivasan. "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 his colleagues discovered that a very small alternating current, when applied to a lithium-ion battery at specific frequencies, is modified by the cell in a way that is directly related 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," Srinivasan noted. "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 are able to register that any change has taken place." APL's sensor is designed to operate through a simple electrical connection at the positive and negative terminals of the cell using power from the battery it is monitoring. Ultimately, the team believes it could enable battery management systems to more closely manage battery performance and, more importantly, detect unsafe thermal conditions at the critical moment before the cell vents or sets itself and the battery on fire. Srinivasan concluded: "By integrating this technology into their products, manufacturers of batteries, battery management systems and battery solution providers can increase both the safety and performance of their products."