Flexible supercapacitor (FSC), thanks to light weight, efficient power delivery and high safety, holds great potential in potable/wearable electronics, whose development would be accelerated by ideal electrode materials. Herein, we report a flexible binder-free electrode composed of polyaniline (PANI) nanofiber-lapped arrays in-situ grown on the molecular-modified carbon cloth (fCC) by a facile one-spot protocol. After optimization, PANI/fCC-2 electrode affords a high specific capacitance of 517.3 F g−1 at 1 A g−1, benefited from highly pseudocapacitive PANI and open channels favorable for rapid ion/electron transfer. Using this novel electrode, flexible quasi-solid-state SC with PVA/H2SO4 gel electrolyte displays a high energy density of 9.03 Wh kg−1 at a power density of 82.9 W kg−1 and is retained at 6.11 Wh kg−1 at 2784.3 W kg−1, with excellent rate capability (97.4% capacitance retention from 0.5 to 20 A g−1) and good cycling stability (79.5% retention over 10,000 cycles). Besides, such four devices in series can light up a light-emitting diode (LED) indicator as a proof of concept in real applications. Our research would provide a promising avenue to develop flexible integrated electrode for next-generation high-performance devices.