Enriched carbon dots/graphene microfibers towards high-performance micro-supercapacitors

Methods allowing high-performance fiber-shaped micro-supercapacitors (micro-SCs) to be produced in a controllable manner are potentially important for portable and wearable electronics. Currently, their low energy density and mechanical strength pose critical challenges for fiber-shaped SCs, which severely discourages their practical applications. Herein, we propose a new dot-sheet structured integration of carbon dots (CDs) with graphene to construct high-performance CDs/graphene fiber-based micro-SCs via a microfluidic strategy. The micro-SCs produced using solid-state acid and organic electrolytes show great enhancement in energy storage abilities, including larger capacitance (area specific capacitance, 607 mF cm^-2; mass specific capacitance, 91.9 F g^-1), long-term bending durability (2000 cycles) and high energy densities (67.37 μW h cm^-2). Their remarkable performance results from dot-sheet structured electrodes with larger specific-surface-area (SSA, 435.1 m² g^-1), more ionic channels (average pore size of 2.5 nm) and high mechanical strength, creating a highly effective utilization ratio of SSA (96%) for faster and greater ion accumulation. Additionally, CDs also contribute 22.1% of the improvement to capacitance. Based on these superior achievements, we utilize micro-SCs to power CD-based white LEDs, a smart watch and miniaturized traffic lights, which will guide the development of the next generation of wearable electronics.