Printed Orthogonal Grid Electrode‐Based Flexible Pressure Sensor for Swelling Force Monitoring in LFP Batteries During Cycling and Thermal Runaway

ABSTRACT The swelling force evolution in lithium iron phosphate (LFP) batteries serves as a critical indicator of internal mechanical changes, providing valuable insights into battery degradation and safety risks. However, conventional flexible pressure sensors face significant challenges in battery expansion monitoring, including limited pressure range, insufficient cycling durability, and poor compatibility with commercial battery designs. In this study, we fabricated a thin‐film pressure sensor featuring orthogonal grid electrodes through screen‐printing crisscrossed electrode arrays between dual‐layer PET substrates. This grid‐contact mechanism effectively extends the sensor's pressure detection range. The optimized sensor demonstrates an extended pressure range (0–2 MPa) and excellent cycling stability (>3000 cycles), meeting the stringent requirements for long‐term battery monitoring. When attached to prismatic LFP battery cells, the sensor successfully captured dynamic swelling force variations during galvanostatic cycling at 0.3C, 0.5C, and 1.0C rates. Moreover, during overcharge‐induced thermal runaway tests, the sensor accurately monitored the swelling force evolution, with peak forces exceeding 5000 N during the thermal runaway phase. This work not only proposes a novel methodology to expand the measurement range of printed thin‐film sensors but also provides a scalable and cost‐effective solution for battery health monitoring.