Temperature is the key monitoring measurement of lithium-ion battery condition monitoring, and it plays a very important role in battery life prediction, thermal runaway warning, and thermal management decision making. Therefore, this paper mainly summarizes the research status of internal temperature monitoring (ITM) method for lithium-ion batteries. Firstly, the lithium-ion battery ITM methods are divided into three types, namely temperature sensor, battery thermal model, and electrochemical impedance spectroscopy (EIS) types. The measurement principle, implementation difficulty, and measurement effect of the above ITM methods are different. The advantages and disadvantages of these methods are analyzed and pointed out. In particular, the five latest ITM methods based on negative temperature coefficient (NTC) temperature sensor, optical fiber sensor, ultrasonic wireless sensor, electrochemical thermal coupling model, and multi-frequency EIS are introduced. Finally, based on the existing research, the future development trend of the above five methods is discussed.

Lithium-ion batteries (LIBs) are widely used in the fields of consumer electronics, new energy vehicles, and grid energy storage due to their high energy density and long cycle life. However, how to effectively evaluate the State of Charge (SOC), State of Health (SOH), and overcharging behavior of batteries has become a key issue in improving battery safety and lifespan. Acoustic sensing technology, as an advanced non-destructive monitoring method, achieves real-time monitoring of the internal state of batteries and accurate evaluation of key parameters through ultrasonic testing technology and acoustic emission technology. This article systematically reviews the research progress of acoustic sensing technology in SOC, SOH, and overcharge behavior evaluation of LIBs, analyzes its working principle and application advantages, and explores future optimization directions and industrialization prospects. Acoustic sensing technology provides important support for building efficient and safe battery management systems.