Development of a Chemically Resistant Coating for a novel Fiber Optic Temperature Sensor embedded in Lithium-ion Batteries

M.R. Rameez, C. Ukata, A. Ghannoum, P. Nieva
University of Waterloo,

Keywords: optical fiber, temperature sensing, PMMA, AL-2233, lithium-ion batteries


Lithium-Ion batteries are ubiquitous in modern day life, with their market value set to reach more than USD 65 billion in 2023 [1]. Temperature is a key parameter in the safe operation of lithium-ion batteries [2]. Yet to monitor battery temperature, we are still reliant on using sensors which are often attached to the outside of the battery casing. Developing a method which accurately but also safely measures the temperature of a lithium-ion battery is paramount as more and more devices become mobile and hence reliant on lithium-ion battery technology. This is especially important as demonstrated by the global recall of the Samsung Galaxy Note 7 which was caused by overheating batteries and estimated to have cost over USD 5 billion [3]. An intensity based Optical fiber temperature sensor has been considered as the ideal candidate for internal monitoring of temperature. Optical fibers are relatively cheap, lightweight, and reliable. To enhance the temperature sensitivity of an optical fiber a thin coating of PMMA is applied on and etched region of the fiber where the cladding has been removed. PMMA has the desirable reflectivity which varies with respect to temperature [4]. However, PMMA is chemically susceptible to the organic electrolyte solution found inside lithium-ion batteries. To counteract this, a chemically resistant coating is required to protect the PMMA layer. The present work investigates the application of a Teflon-like fluoropolymer coating solution known as AL-2233 [5] to coat the PMMA layer. The coating process is achieved through dipping, which can also be integrated into a continuous process for large scale production. The coating thickness and temperature sensitivity relative to non-coated sensors will be presented in this work. Please refer to the extended abstract for a graph (Fig. 1) demonstrating the performance of a PMMA coated optical fiber with temperature and a diagram outlining the fabrication steps of the chemically resistant temperature sensor (Fig. 2). [1] Zion Market Research, “Projected lithium ion battery market size worldwide in 2016 and 2022 (in billion U.S. dollars),” 2018. [2] P. G. Balakrishnan, R. Ramesh, and T. Prem Kumar, “Safety mechanisms in lithium-ion batteries,” Journal of Power Sources, vol. 155, no. 2, pp. 401–414, Apr. 2006. [3] “Samsung Explains Note 7 Battery Explosions, And Turns Crisis Into Opportunity.” [Online]. Available: [Accessed: 31-Jan-2019]. [4] S. N. Kasarova, N. G. Sultanova, and I. D. Nikolov, “Temperature dependence of refractive characteristics of optical plastics,” Journal of Physics: Conference Series, vol. 253, p. 012028, Nov. 2010. [5] AngströmLink, “AL-2233 Optical Coating,” 2016.