A study on thermal performance of batteries using thermal imaging and infrared radiation

This study attempted to improve the performance of pouch-type lithium iron phosphate battery (LiFePO4) through analysis on its degradation mechanism at a high rate (10 C) for the purpose of observing resistance and electrochemical changes in each material when a battery was manufactured considering the low electrical conductivity and of lithium iron phosphate and properties of cathode materials. For this, the life and safety of lithium batteries are evaluated after forming dendrites through the reduction of lithium at the negative electrode (graphite) as resistance in LiFePO4. The components of LiFePO4, which generate this kind of resistance includes tab, electrolytes, cathode active materials, anode active materials, binders and conductive materials. The main cathode (lithium-ion phosphate) and anode (natural graphite) materials were fabricated in 90% and 96% respectively, using conductive materials and binders. For a case, a 20 Ah Al pouch was fabricated. A full cell was fabricated with the best materials and components through analysis on resistance characteristic. Then, LiFePO4 was thermally safer with a long lifespan than the conventional high-rate output. For analysis on materials, in addition, basic material analysis was performed through impedance, X-ray diffraction (XRD), X-Scan and field emission scanning electron (FESEM). After tracing heat generated within the battery using infrared radiation (IR), the degree of degradation was examined. Then, the degradation rates of lithium batteries and reliability of measurements were comparatively assessed. When analyzed with an infrared camera, temperature rapidly rose up to over 80 °C during charge and discharge. A battery was fabricated using an industrial engineering method which can secure internal resistance-lowering slurry and coating dispersion processes and reduce resistance in the binder and tab joint. As a result, it was able to substitute conventional LiFePO4 with high internal resistance, disperse heat inside the cell and increase its lifespan.