Harnessing Free-Standing Flexible Dual Carbon Lithium-Ion Capacitors with Carbon Fiber–Pitch Composite Electrodes

Dual carbon lithium-ion capacitors (DC-LICs) have emerged as a promising solution to reconcile the disparity between high-energy-density lithium-ion batteries (LIBs) and high-power-density supercapacitors (SCs). However, the kinetic discrepancy between the two electrodes limits their applications. This research focuses on synthesizing and optimizing carbon-based anode and cathode materials from a widely abundant petroleum pitch precursor and carbon fiber (CF) mat current collector. The anode is developed through hydrothermal-calcination of pitch and thiourea, followed by a coating of hydrothermal-derived carbon using additional pitch (without binder and additional carbon black). At the same time, the cathode is activated carbon obtained by KOH activation. Herein, the utilization of N, S-doped carbon coated on CF (CFP8) as an anode can tackle the high rate performance of the activated carbon cathode (ACP8). Further, using CF as a current collector makes this LIC device flexible and more sustainable. Thus, the optimized DC-LICs (1.5:1 mass ratio) exhibit a superior energy density of 63 Wh kg^–1 at a high power density of 8300 W kg^–1. Besides, this CF-based flexible DC-LIC device exhibits 75% retention in capacity even after 10 000 cycles. Thus, this finding emphasizes the potential of DC-LICs, highlighting the improved energy, self-discharge, and leakage current compared with traditional supercapacitors.