Highly foldable and free-standing supercapacitor based on hierarchical and hollow MOF-anchored cellulose acetate carbon nanofibers

Flexible electrode materials have achieved great breakthroughs during the past decades. However, many challenges remain such as how to overcome the frangibility and enhance the flexibility, and advance the high specific capacitance. We fabricated a free-standing, foldable, and conductive cellulose acetate (CA)-based metal-organic framework (MOF) composites by facile electrospinning carbonization and co-precipitation method. The sustainable cellulose derivative provides a flexible matrix, which contains hierarchically porous and ample redox activities. The intermolecular interaction is enhanced for coordination between exposed hydroxyl on deacetylated CA and metal ions, thus reduce the fracture of the CA nanofibers. Importantly, multi-layer heterojunction structure and honeycomb-like MOF nanosheets with reversibly flexible deformation create interlamellar pathways to improve the bending resistance of nanofibers. The controlled Co/Zn ion concentration could effectively modulate spatial distribution of Co/Zn MOF to thus generate different conductive channels. The asymmetric flexible supercapacitor based on Ni/Co LDH@ Co/Zn NC@CDCP-N electrode material gives high specific capacitance (175.2 F g⁻¹ at 1 A g⁻¹) and outstanding energy density (54.8 W h kg⁻¹) at high power density (985.5W kg⁻¹). Our work paves a way to facile fabrication of flexible and free-standing electrode materials for practical flexible energy storage, such as artificial electronic skin and soft wearable electronics.