Embedded Fiber Optic Sensors for In Situ and In-Operando Monitoring of Advanced Batteries
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Embedded Fiber Optic Sensors for In Situ and In-Operando Monitoring of Advanced Batteries Julian Schwartz1, Kyle Arakaki1, Peter Kiesel1, Ajay Raghavan1, Wilko Sommer1, Alexander Lochbaum1, Anurag Ganguli2, Alex Hegyi1, Bhaskar Saha1, Chang-Jun Bae1, HoeJin Hah2, ChaeAh Kim2, and Mohamed Alamgir3 1 Palo Alto Research Center (PARC, a Xerox Company), Palo Alto, CA 94304, U.S.A. 2 LG Chem Research, Yuseong-gu, Daejeon, Korea. 3 LG Chem Power, Troy, MI 48083, U.S.A.
ABSTRACT Our team is developing an optically-based smart monitoring system prototype targeting batteries for advanced battery applications such as hybrid and electric vehicles (EVs). The system concept envisions fiber optic (FO) sensors embedded within Lithium (Li)-ion batteries to measure parameters indicative of cell state in conjunction with our low-cost, compact optical wavelength-shift detection technology and intelligent algorithms to enable effective real-time performance management and optimized battery design. Towards these goals, we have successfully made functional prototypes of Li-ion pouch cells with FO sensors embedded within the electrode stack during cell fabrication. The strong, interesting signals from these FO sensors obtained over charge-discharge cycles offer valuable information and features to enable more accurate cell state-of-charge (SOC) and state-of-health (SOH) estimation, and better understand cell electrochemical and aging processes. This paper presents initial results from these prototype cells and compares the results from internal FO signals to earlier results reported by our team on purely external configurations where the FO sensors were attached to the cell skin. Introduction Battery systems for electric vehicles, grid storage, and other emerging applications are presently limited by factors such as high costs, battery lifetime, driving range, and the susceptibility for unexpected failure. Effective control and management of cell charge and discharge by battery management systems (BMS) is essential for good performance [1]-[3]. The limitations of prevalent present-day BMS that rely on monitoring external performance parameters such as voltage, current, and temperature are well known. More informative embedded sensors are highly desirable, particularly for internal state monitoring, which could provide accurate state-of-charge (SOC) estimates and early indications of incipient problems, enabling much improved state-of-health (SOH) estimates for BMS. Fiber optic sensors are lightweight and thin, immune to electrostatic discharge, electromagnetic interference, can be protected with suitable coatings to withstand harsh environments, and can measure multiple parameters with high sensitivity, such as strain, temperature, pressure, and chemical composition in multiplexed configurations. All of these characteristics make them very attractive candidates for embedding as sensors in batteries. Within this project, we are exploring fiber Bragg gratings (FBGs) [4], a type of FO sensor to measure strain and temperature as an alternativ
