Biodegradable porous polylactic acid film as a separator for supercapacitors

A porous polylactic acid (PLA) film was investigated as a separator for supercapacitors (SCs) and compared with commercial separators, for example, NKK-MPF30AC and Celgard 2400. The porous PLA film was fabricated via a facile phase inversion method, and the cross-sectional scanning electron microscope images of the PLA separator film exhibited highly porous interconnected morphology for ion diffusion. The surface modification of separators was performed by radio frequency (RF) air plasma to improve wettability. The plasma modification enhanced the water uptake and swelling properties of the separators and decreased the water contact angles of PLA and Celgard 2400 films. The mechanical and dielectric properties of separators were also studied. The ionic conductivities of RF-PLA in 1 M H₂SO₄ and 1 M Na₂SO₄ were found to be 1.1 × 10⁻¹ S/cm and 0.6 × 10⁻² S/cm at room temperature, respectively. The electrochemical impedance spectroscopy of the RF-PLA SCs showed the lowest solution resistance and internal resistance.