Microcrack Arrays in Dense Graphene Films for Fast‐Ion‐Diffusion Supercapacitors

Abstract Laminated graphene film has great potential in compact high‐power capacitive energy storage owing to the high bulk density and opened architecture. However, the high‐power capability is usually limited by tortuous cross‐layer ion diffusion. Herein, microcrack arrays are fabricated in graphene films as fast ion diffusion channels, converting tortuous diffusion into straightforward diffusion while maintaining a high bulk density of 0.92 g cm −3 . Films with optimized microcrack arrays exhibit sixfold improved ion diffusion coefficient and high volumetric capacitance of 221 F cm −3 (240 F g −1 ), representing a critical breakthrough in optimizing ion diffusion toward compact energy storage. This microcrack design is also efficient for signal filtering. Microcracked graphene‐based supercapacitor with 30 µg cm −2 mass loading exhibits characteristic frequency up to 200 Hz with voltage window up to 4 V, showing high promise for compact, high‐capacitance alternating current (AC) filtering. Moreover, a renewable energy system is conducted using microcrack‐arrayed graphene supercapacitors as filter‐capacitor and energy buffer, filtering and storing the 50 Hz AC electricity from a wind generator into the constant direct current, stably powering 74 LEDs, demonstrating enormous potential in practical applications. More importantly, this microcracking approach is roll‐to‐roll producible, which is cost‐effective and highly promising for large‐scale manufacture.