Large temperature difference arises in big-size Li-ion cells (e.g. 94Ah Samsung cells) due to low thermal conductivity of battery materials, especially under extreme conditions like high C rate operation at low temperatures or abuse conditions [1]. Previous research [2,3] has attempted to embed micro thermocouples in 18650-format cylindrical cells (1.6 Ah) and demonstrated that internal temperature sensing is more useful than surface temperature sensing in early detection of abnormal thermal behaviors for safety enhancement. For practical applications of this technique, internal temperature sensors must be robust and durable to survive battery life cycle and must be low cost. In this study we developed a new resistance temperature device (RTD) based on nickel foil that meets both criteria. Embedded in 10Ah pouch cells, these in-cell temperature sensors still function well after the cells experienced 2,500 cycles. It is believed that low-cost, durable and reliable in-cell temperature sensors have finally arrived to enable substantial improvement in the Li-ion battery’s high-temperature safety and thermal management.

References:

1. X.G. Yang, T. Liu and C.Y. Wang, Innovative heating of large-size automotive Li-ion cells, Journal of Power Sources, accepted for publication, 2017.
2. G.S. Zhang, L. Cao, S. Ge, C.Y. Wang, C. E. Shaffer and C. D. Rahn. In situ measurement of radial temperature distributions in cylindrical Li-ion cells, Journal of The Electrochemical Society, 2014, 161: A1499-A1507
3. G.S. Zhang, L. Cao, S. Ge, C. Y. Wang, C. E. Shaffer and C. D. Rahn. Reaction temperature sensing (RTS)-based control for Li-ion battery safety, Scientific Reports, 2015, 5: 18237