Interface-engineered hexagonal boron nitride modified PANI/MWCNTs nanocomposites for flexible symmetric supercapacitor in functionalized PVA/H2SO4 gel electrolyte

Developing energy storage devices that combine excellent electrochemical performance with mechanical compliance is critical for wearable and flexible electronics and cannot be achieved with traditional current collectors or leakage-prone liquid electrolytes. Herein, we describe a flexible all-solid-state supercapacitor based on a ternary nanocomposite electrode comprising polyaniline (PANI), multi-walled carbon nanotubes (MWCNTs), and hexagonal boron nitride nanosheets (h-BNNs). The current collector is made of copper foil coated with reduced graphene oxide (rGO), which enhances its Young's modulus and corrosion resistance under acidic conditions. In the composite, h-BNNs act as structural and thermal buffers that hinder MWCNTs restacking and dissipate Joule heat, protecting PANI from pulverization during redox cycling; MWCNTs form a percolating conductive network, and PANI provides pseudocapacitive charge storage. The developed electrodes are symmetrically paired with an h-BNN-functionalized poly (vinyl alcohol)/H 2 SO 4 gel electrolyte, in which the h-BNN filler facilitates Grotthuss-type proton hopping and overcomes the sluggish ion diffusion observed in solid-state electrolytes. The hierarchical, interconnected porous architecture delivers a high specific capacitance of 289 F/g at 5 mV/s, together with an energy density of 32.4 Wh/kg and a power density of 449.7 W/kg, while maintaining 91% capacitance retention after 5000 cycles. This synergistic composite design, comprising a mechanically reinforced current collector, a thermally stabilized pseudocapacitive composite, and a fast-ion-conducting gel electrolyte, provides a generalizable strategy to bridge the performance gap between liquid- and solid-state supercapacitors, thereby enabling flexible energy storage for next-generation wearable devices.