Design of Scalable and Flexible Supercapacitors Based on Mulberry Paper: Optimizing Electrochemical Performance and Reliability

Paper-based supercapacitors are emerging as promising alternatives for next-generation wearable energy storage applications, attributed to their renewable feedstocks, scalability, flexibility, and lightweight properties. However, the inherent limited electrochemical conductivity and poor stability of paper remain significant challenges for making high-performance applications. In this study, we designed a scalable and flexible supercapacitor utilizing carbonized mulberry paper (cMP) to overcome these limitations. Electrochemical performance was maximized through the development of TiO₂ nanoparticles strongly bonded to reduced graphene oxide on the surface of cMP fibers, which increased from 8.5 to 153 mF cm^-2 at a scan rate of 5.0 mV s^-1. The strongly bonded structure also improved electrochemical reliability. During long-term charge-discharge cycling tests, the designed electrode maintained 75% of its capacitance after 3000 cycles at 1.0 mA cm^-2 and demonstrated an impressive retention of 80% at 8.0 mA cm^-2. A large-scale flexible supercapacitor was realized by utilizing an electrode that demonstrated outstanding electrochemical performance and reliability. A large-area supercapacitor with a 40 cm² electrode was successfully implemented, achieving a discharge time retention of 95.6% and capacitance retention of 99.3% even under repetitive twisting and bending. These engineering results unveil possibilities for scalable and flexible supercapacitors.