The rapid development of wearable, highly integrated, and flexible electronics has stimulated great demand for on-chip and miniaturized energy storage devices. By virtue of their high power density and long cycle life, micro-supercapacitors (MSCs), especially those with interdigital structures, have attracted considerable attention. In recent years, tremendous theoretical and experimental explorations have been carried out on the structures and electrode materials of MSCs, aiming to obtain better mechanical and electrochemical properties. The high-performance MSCs can be used in many fields, such as energy storage and medical assistant examination. Here, this review focuses on the recent progress of advanced MSCs in fabrication strategies, structural design, electrode materials design and function, and integrated applications, where typical examples are highlighted and analyzed. Furthermore, the current challenges and future development directions of advanced MSCs are also discussed.

Flexible supercapacitors have shown enormous potential for portable electronic devices. Herein, hierarchical 3D all-carbon electrode materials are prepared by assembling N-doped graphene quantum dots (N-GQDs) on carbonized MOF materials (cZIF-8) interweaved with carbon nanotubes (CNTs) for flexible all-solid-state supercapacitors. In this ternary electrode, cZIF-8 provides a large accessible surface area, CNTs act as the electrical conductive network, and N-GQDs serve as highly pseudocapactive materials. Due to the synergistic effect and hierarchical assembly of these components, N-GQD@cZIF-8/CNT electrodes exhibit a high specific capacitance of 540 F g at 0.5 A g in a 1 m H SO electrolyte and excellent cycle stability with 90.9% capacity retention over 8000 cycles. The assembled supercapacitor possesses an energy density of 18.75 Wh kg with a power density of 108.7 W kg . Meanwhile, three supercapacitors connected in series can power light-emitting diodes for 20 min. All-solid-state N-GQD@cZIF-8/CNT flexible supercapacitor exhibits an energy density of 14 Wh kg with a power density of 89.3 W kg , while the capacitance retention after 5000 cycles reaches 82%. This work provides an effective way to construct novel electrode materials with high energy storage density as well as good cycling performance and power density for high-performance energy storage devices via the rational design.

Hierarchical N-doped porous carbon has been prepared by assembling N-doped graphene quantum dots (N-GQDs) onto a carbonized metal–organic framework (cMOF-5) and used as an electrode material for supercapacitors.