Opto-chemical sensors for direct measurement of state of energy in electric battery cells

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The battery pack is the main source of energy in electric vehicles (EVs) and its management plays a big role in promoting widespread adoption of EVs by consumers. Determination of the true chemical state of energy (SOE) of individual battery cells is needed to enable real-time battery pack performance management while predicting degradation and failure. Currently, performance management is done using parameters such as current, voltage and surface temperature, provided by electrical sensors collocated in groups of cells rather than in every single cell in the pack; through this approach, certain parameters, such as the exact amount of chemical energy left in a single cell or its state of health (SOH) cannot be revealed. Additionally, variations in cell internal operating temperature influence the kinetics of the chemical process within it, causing cell degradation or directly influencing the SOE. Potential failure and premature cell degradation are usually avoided by not operating the cells to their full capacity and over-engineering the battery packs. The long-term goal of this research program is to develop a new sensing framework for EVs battery packs using fiber optic (FO) sensors leading to a more effective management of their performance. To do so, the applicant has identified the following short-term objectives: (1) Development of viable fabrication methods for multifunctional FO sensors for direct measurement of SOE and internal temperature of battery cells: an embedded opto-chemical FO sensor developed by the applicant to monitor internal cell energy will be multiplexed to allow internal temperature sensing within the same fiber; (2) Modeling and validation of multifunctional opto-chemical sensors for direct measurement of SOE and temperature: the modeling will focus on (i) using the sensor data to better estimate the SOE of the cell; and (ii) monitoring drifts or changes in the intercalation stage transitions together with temperature variations to estimate SOH. The models will be validated using current industrial benchmarks; and (3) Implementation and packaging of embedded multifunctional opto-chemical FO sensors: a demonstrated compact LED-based optical system interrogator with signal amplification circuitry will be multiplexed to simultaneously measure SOE and internal temperature for accurate estimation of SOH of individual cells, crucial for real-time EV battery pack monitoring. This will enable new management strategies that will lead to safer and optimal utilization of true cell capacity which will improve costly conservative design of battery packs, thus helping to accelerate mass consumer adoption of EVs. The applicant's proven record and state-of-the-art sensor development laboratory will provide HQP with the necessary tools to succeed in achieving the above research objectives and will help position Canada as a global leader in EVs technology.