Distributed internal thermal monitoring of lithium ion batteries with fibre sensors

Real-time monitoring of the thermal characteristics of a lithium ion battery under electrical excitation, is a key requirement that underpins the safe operation of the battery; its reliability and life. Further, it facilitates the design of many supporting elements of the battery system, including the thermal management strategy and the algorithms that comprise the battery management system. The novelty of this study is advanced distributed thermal monitoring from external to embedded measurement for future smart battery and management. Rayleigh scattering based optical fibre sensors are known to be robust and able to operate when immersed in electrolyte, they have a small physical size and are able to provide a measurement of temperature with a spatial resolution of circa 2.6 mm. The spatial distribution of the temperature profile, arising from the complexity and variations within the cell is investigated. The results show that the peak temperature between the cell core and surface, along the cell length can be as high as 9.7 °C for 1C discharge. This paper provides a detailed explanation of the cell modification method, instrumentation process and the fundamental principles of in-cell optical measurement. Results are presented and discussed within the context of enhanced battery thermal management and improved system safety that are applicable to the application of lithium ion batteries across a number of domains including automotive and aerospace.