Effects of Tensile Stress on Energy Storage and Dielectric Properties of <scp>BOPP</scp> Film

ABSTRACT Dielectric films are subjected to continuous tensile stresses after being manufactured into capacitors, which can pose significant challenges for long‐term performance and reliability. In this paper, the influence of tensile stress during winding of biaxially oriented polypropylene (BOPP) film on energy storage and dielectric properties is analyzed. Experimental results indicate that a tensile stress of 12 MPa causes a 6.9% reduction in breakdown strength. In addition, the discharge energy density and charge–discharge efficiency are reduced to 2.44 J/cm 3 and 72.87% at 600 kV/mm, compared with 4.62 J/cm 3 and 88.36% at 700 kV/mm for the pristine film. Under applied tensile stress, the structural integrity of the grain region in BOPP film is compromised, resulting in a slight decrease in crystallinity and melting temperature. These microstructural changes lead to an increase in leakage current, dielectric loss, and free volume, while simultaneously reducing the density and level of deep traps capable of capturing charge carriers. This study provides a meaningful reference for studying the evolution of the physical properties of dielectric materials for energy storage and revealing the mechanism of performance degradation.