Perforated structure optimization and mechanical behavior analysis of polypropylene-based composite current collector substrates for high-energy-density lithium-ion batteries

Lithium-ion batteries widely adopt composite current collectors to improve energy density and safety. Perforation is one approach used to modify the structure of these current collectors. However, the introduction of holes may reduce the mechanical property of the polymer substrate. This study employs finite element simulation to investigate the effects of hole diameter, hole density, and hole arrangement on the tensile behavior of polypropylene substrates in the machine direction (MD) and transverse direction (TD). The results show clear transition intervals within the selected parameter ranges. Increasing the hole diameter reduces the effective material area and increases the local stress concentration. In the hole density series, the perforated region becomes denser as the spacing decreases and the number of holes increases. The increase in hole density is accompanied by an increase in open area fraction. The resulting degradation therefore reflects the mechanical response of the selected hole density configurations. The staggered arrangement produces a more dispersed damage distribution and delays the formation of a continuous numerical damage path. Compared with the rectangular arrangement, it increases the tensile strength by 15.5% in MD and 10.9% in TD. The corresponding increases in elongation at break are 33.2% and 31.9%. These results clarify the mechanical response of perforated PP substrates and provide a basis for the further electrical and mechanical optimization of composite current collectors.