유연 리튬 폴리머 이차전지의 기계적 변형에 따른 성능 및 안전성 평가

Purpose: Flexible lithium-ion batteries have been used as energy sources for wearable and flexible devices. However, their reliability in mechanical stress environments must be guaranteed for them to be stably used in these applications. In this study, the effect of mechanical fatigue on the performance and safety of a lithium polymer battery, which is a flexible lithium-ion battery, was investigated.
Methods: Mechanical fatigue tests were conducted under bending, torsion, and wrinkling (i.e., a combination of bending and torsion) modes at various fatigue rates and strains. The capacity degradation of these fatigued flexible lithium-ion batteries was evaluated using the charge–discharge test. Their safety was assessed using various environmental and electrical misuse tests in accordance with existing standards.
Results: The capacity degradation of all fatigued batteries was greater than that of the undeformed battery. In particular, the torsion and wrinkling stress had a greater effect on capacity degradation. The environmental and electrical misuse tests revealed that leakage, explosion, and ignition phenomena were not caused by mechanical fatigue.
Conclusion: Mechanical fatigue stress can be concluded to be the main factor affecting the performance degradation of flexible lithium-ion batteries. Furthermore, further studies are required to determine the root causes of this significant performance degradation.