Operando Thermo-Electrochemical Diagnostics with Au, TiO2, and LiFePO4 as Reference Electrodes in Li-Ion Pouch Cells

Thermo-electrochemical monitoring of state-of-the-art rechargeable Li-ion batteries during operation is critical for safety and reliability, yet it remains quite limited, relying on conventional full cell measurements with in situ techniques lagging behind. Here, the feasibility of incorporating Au, LiFePO4, and TiO2 electrochemical sensors into commercially available pouch cells, in conjunction with thermocouples to track the cell behavior during galvanostatic cycling at varying operating temperatures is demonstrated. It is found that Au provides the best in operando based electrochemical diagnostics for stable thermo-electrochemical performance via long-term cyclability (>1000 h), differential capacity curves, and at 25, 40, and 60 degrees C, followed by TiO2, and LiFePO4. Furthermore, cell temperature changes are analyzed alongside reference electrode readings, demonstrating the advantages of the complementary nature of these techniques for cell thermodynamics. Collectively, these findings offer deep insight into an improved battery management approach for next-generation lithium-ion energy storage systems.