<p>Among various energy storage devices, supercapacitors have garnered significant attention due to their unique advantages, including high power density, rapid charge–discharge capability, and long cycle life. However, conventional electrodes typically rely on non-conductive binders, which complicate the fabrication process, increase production costs, and limit pore structure tunability, ultimately reducing energy density. In this study, we developed a self-supporting paper-based electrode with tunable micro-/mesoporous structures by integrating the highly crystalline lamellar microfibril structure of lyocell fibers and the high aspect ratio of softwood pulp fibers, through a combination of wet papermaking, thermal carbonization, and phosphoric acid activation. The fibrillation behavior of lyocell fibers enhanced inter-fiber hydrogen bonding and phosphate ester linkage formation, facilitating ion transport within the electrode. By adjusting the beating revolutions and fiber composition, the micropore volume ratio (V &lt; sub &gt; mi &lt; /sub &gt; /V &lt; sub &gt; tot &lt; /sub &gt;) was effectively tuned between 18.2% and 67.7%. Softwood pulp fibers served as a reinforcing scaffold, significantly improving the mechanical strength and enabling the self-supporting property of the material. The resulting electrode exhibited a high specific surface area of 1876&#xa0;m²/g and delivered a specific capacitance of 225 F/g at 1 A/g in a three-electrode system, with a remarkable capacitance retention of 99.8% after 10,000 cycles. This work offers a promising strategy for the cost-effective and scalable fabrication of high-performance paper-based electrodes, demonstrating significant potential for application in energy storage systems.</p> Graphical abstract <p></p>