Composite electrode fabricated by MnO2 interlayer-directed electropolymerization of polyaniline on laser-induced graphene for flexible supercapacitors

Laser-induced graphene (LIG) features monolithic in-situ fabrication, inherent flexibility and a continuous graphitized conductive network, showing unique advantages for flexible integrated supercapacitor electrodes. However, its low areal double-layer capacitance cannot meet the energy demand of high-performance flexible devices. Direct electropolymerization of polyaniline (PANI) on LIG faces specific bottlenecks distinct from conventional carbon cloth substrates: the smooth graphitized surface and three-dimensional macroporous skeleton of LIG lead to random nucleation, severe agglomeration and weak interfacial adhesion of PANI, which hinder conformal growth of active materials inside pore channels and limit performance improvement. To address this issue, a sequential electropolymerization strategy is proposed using layered δ-MnO 2 as a structural template interlayer. Three-dimensional macroporous LIG is first fabricated on polyimide via defocused UV laser irradiation, followed by uniform deposition of ultrathin δ-MnO 2 nanoclusters as heterogeneous nucleation sites. The pre-built MnO 2 template guides uniform conformal growth of PANI nanospheres, strengthens interfacial charge transfer, and realizes synergistic pseudocapacitance from both components. The optimized electrode delivers an areal capacitance of 562.9 mF cm − 2 at 1 mA cm − 2 . The assembled all-solid-state flexible supercapacitor exhibits excellent rate capability and cycling stability (86.8% retention after 5000 cycles) and mechanical robustness (95% capacitance retention under 90° bending). This work provides an interface engineering strategy for constructing high-performance LIG-based flexible energy storage devices.