Fiber optical sensors for enhanced battery safety

Over the last years, battery safety becomes more and more important due to the wide spread of high-capacity lithium ion batteries applied in e.g. consumer electronics and electrical power storages for vehicles or stationary energy storage systems. However, for these types of batteries, malfunctions could be highly dangerous and all aspects of safety issues are not sufficiently considered, yet. Therefore, the improvement of the battery safety behavior is one of the most important issues discussed in actual research projects. In this paper the application of fiber optical sensors for enhanced battery safety is presented. The temperature is one of the most critical parameters indicating a failure of the cell, but even state-to-the-art battery management systems (BMS) are not able to monitor and interpret the distributed temperature field of a total battery storage system sufficiently. Furthermore, the volume expansion of the battery cell, which could be monitored by the strain on the cells' surfaces, is one additional parameter not considered up to now. Both parameters could be simultaneous monitored by fiber optical sensor arrays, consisting of discrete fiber Bragg grating (FBG) elements. The FBG sensors are directly attached on the surface of the cell, recording the temperature as well as the strain distribution highly accurate and close-meshed. Failures and malfunction such as overcharging, gassing, and thermal runaway can be early predicted and avoided to extend the battery lifetime and enhance the operational battery safety. Moreover, battery aging effects lead to variations in the volume change behavior which can be detected additionally. Hence, a battery fully equipped with fiber optical sensor arrays in combination with an appropriate BMS enables a safe and continuous utilization of the energy storage system even under harsh conditions like rapid charging.