A Flexible Thin-Film Temperature Sensor Based on a SnO ₂ /RGO Composite Material for Lithium-Ion Battery Temperature Monitoring

Temperature monitoring serves as an effective safety measure for lithium batteries. However, conventional temperature sensing technologies face limitations in dynamic monitoring applications due to insufficient flexibility, poor adhesion to curved surfaces, and challenges in achieving multipoint measurements. Consequently, this work investigates a flexible thin-film temperature sensor based on a SnO 2 /RGO composite material, fabricated via a simple one-step hydrothermal process. The sensor enables temperature monitoring at multiple locations on the lithium battery surface, thereby more accurately reflecting the temperature distribution across the battery surface. The temperature sensor exhibits a highly linear (99.64%) negative temperature coefficient (NTC) characteristic over the range of 10–100 °C, along with high sensitivity (−0.766%/°C) and excellent cyclic stability. We used the fabricated temperature sensor to the surface of a pouch lithium battery for monitoring surface temperatures under both nonabuse and abuse conditions. The experimental results demonstrate that the sensor effectively captures temperature changes at different locations on the battery surface during actual nonabuse and abuse conditions, offering experimental validation supporting the advancement of flexible thin-film temperature sensors for lithium-ion battery temperature monitoring applications.