Robust self-standing multiscale engineered Ni(OH)₂ film for flexible high-capacity supercapacitor

Flexible and multifunctional energy-storage devices are essential for commercial applications, where areal and volumetric capacitances play a pivotal role in enabling the miniaturization and integration of capacitive energy storage. However, the development of highly integrated practical capacitive components combining high areal/volumetric capacitance with robust mechanical properties remains a significant challenge. Here, we propose a multiscale architectural design for free-standing films comprising amorphous Ni(OH)₂ nanosheets supported on low-dimensional carbon substrates. The hierarchical structure of these membranes exhibits exceptional mechanical properties, including a tensile strength of 600 MPa, elongation of 5.12 %, and fracture absorption work of 1.644 kJ cm⁻³. The ultrathin Ni(OH)₂ nanosheets, characterized by high specific surface area and uniformly distributed pore structures, demonstrate outstanding electrochemical performance. Notably, the areal capacitance reaches 24.5 F cm⁻² (12.25 C cm⁻²), while the volumetric capacitance attains 3056 F cm⁻³ (1528 C cm⁻³). The scalable fabrication of these films offers a promising solution to address energy-storage challenges in electric vehicles and intelligent equipment.