Lithium-ion batteries (LIB) are used in a broad field of applications due to their high energy and power density. Ensuring their safety and continuous performance under various conditions is crucial. Here, in-operando monitoring of internal parameters such as temperature, state of charge (SOC), and state of health (SOH) is essential. However, nowadays battery management systems typically focus on external parameters while neglecting internal changes.
Our work addresses this gap by integrating sensors directly into LIBs to monitor internal parameters. In particular, we focus on internal temperature changes using either integrated glass fibre or temperature sensors, and on changes of the individual electrode potentials using reference electrodes. Both internal temperature and electrode potentials are critical factors regarding battery safety, health, and lifetime.
Monitoring internal temperature includes both average values and distribution within the cell, which is achieved by placing sensors at specific positions. This allows for direct observation of temperature changes during operation and therewith in-situ detection of critical temperatures. Additionally, monitoring of individual electrode potentials provides insights into safety-critical phenomena that cannot be detected by measuring only the voltage difference between the anode and cathode. For instance, reference electrodes can detect Li-plating, at an early stage. The latter not only reduces battery lifetime but might even induce short circuits.
We give insights into the integration processes of our sensors and demonstrate real-time monitoring of temperature and electrode potentials. Furthermore, we show that our sensor integration approach significantly contributes to enhancing the ability to detect safety-critical states and to improve the safety of LIBs.