Flexible, yet robust polyaniline coated foamed polylactic acid composite electrodes for high-performance supercapacitors

Polylactic acid (PLA) has promising potentials for transient electronic applications due to its biodegradability and biocompatibility, which is expected to help alleviate electronic waste disposal problems. Recently, PLA has been used as the polymer substrate to fabricate green and flexible supercapacitors (SCs). However, the intrinsic fracture textile and limited electroactive materials deposited on the PLA substrate resulting in poor energy storage performance still remain challenging. Herein, a facile approach has been proposed to prepare flexible, yet robust electrodes of polyaniline coated on foamed PLA (PANI-fo-PLA). Aniline monomers were directly polymerized on the porous foamed PLA (fo-PLA) which was prepared via a simple nonsolvent-induced-phase-separation (NIPS) method. The fo-PLA endows the PANI-fo-PLA electrode with superior flexibility (a fracture strain of 34.70%) and high mechanical strength (a fracture strength of 77.80 MPa) which are significantly higher than those values of solvent-cast PLA films; meanwhile, the porous structure provides rich sites for the growth of PANI, which thus significantly increases the loadings of electroactive materials, and facilitates the ion transportation during the energy storage process. Employing PVA/H2SO4 as the gel electrolyte, the symmetric PANI-fo-PLA//PANI-fo-PLA SC delivers a high areal capacitance of 27.73 mF cm−2 (@0.05 mA cm−2), which is more than one hundred times higher than that of the SC based on electrodes of PANI grown on non-porous PLA film. The SC retains 66.29% of its original capacitance even bent at 90°, demonstrating its great potentials for flexible wearable electronics. Moreover, the PANI-PLA can be readily degraded in alkaline solutions within 2 h under sonication. This work paves the way to fabricate flexible, transient, and high performance energy storage devices from PLA.Graphical abstractA flexible, robust, and degradable PANI-fo-PLA electrode with high electrochemical energy storage performance has been prepared via a both time- and energy- saving approach.