Operando monitoring of internal temperature in lithium-ion battery enabled by wireless implantable sensor with ultrasonic communication

Internal temperature of lithium-ion battery (LIB) plays an important role in understanding the battery dynamics. Implanting temperature sensor in the battery cell is an effective scheme for operando monitoring of the internal temperature. However, the implementation of wired sensor in the LIB raises the concern of battery safety due to the compromised structural integrity of battery case. In this study, we propose an implantable and wireless temperature sensor to continuously monitor the internal temperature in LIB. The sensor comprises of an ultrasonic communication module and a flexible resistance temperature detector, which transmits the temperature data in terms of resistance variation via ultrasonic wave with the resolution of ∼0.15 °C. The ultrasonic communication effectively eliminates the shielding effect caused by the metallic battery case, thereby enabling the transmission of internal temperature directly through the pouch cell. The sensor is experimentally implanted in a 1 Ah NCM/graphite pouch cell, which shows only a fade of 2.2 % in capacity and an increase of 2.1 % in internal resistance after 100 discharge-charge cycles at the rate of 1C. The implanted sensor is capable of not only continuously monitoring of the internal temperature during 100 discharge-charge cycles but also capturing the difference of temperature variation at the rates varying from 1C to 2C. Profiling of internal temperature in the thermal abuse test is also achieved with the implanted sensor, which illustrates the significant dependence of internal temperature on the battery dynamics associated with the thermal runaway process.