Highly flexible, foldable and stretchable Ni-Co layered double hydroxide/polyaniline/bacterial cellulose electrodes for high-performance all-solid-state supercapacitors

A novel flexible nickel-cobalt layered double hydroxide/polyaniline/bacterial cellulose (NiCo-LDH/PANI/BC) electrode with both excellent electrochemical and mechanical performances is obtained through successively coating PANI and NiCo-LDH on BC. In addition to making the 3D open network (BC) conductive, the PANI layer also functions as a "nanoglue" to uniformly and robustly immobilize nanostructured NiCo-LDH onto the highly enlarged surface of PANI/BC nanofibers owing to its rough surface and hydrophilicity. Benefitting from the hierarchical structure with a 3D conductive network, unobstructed channels, numerous electroactive sites and induced synergistic effect, the NiCo-LDH/PANI/BC electrode shows excellent electrochemical performance in an aqueous electrolyte, exhibiting a high specific capacitance of 1690 F g^-1 (761 C g^-1) at 1 A g^-1, enhanced rate capability (778 F g^-1 or 350 C g^-1 at 15 A g^-1) and outstanding cycling stability (83.2% capacitance retention after 5000 cycles). Besides, the NiCo-LDH/PANI/BC also shows excellent foldability, high tensile strength (90.8 ± 4.9 MPa), high elongation at break (7.2 ± 0.7%) and outstanding electrochemical stability during bending and stretching. Moreover, a flexible all-solid-state supercapacitor is assembled with NiCo-LDH/PANI/BC as the positive electrode and N-doped carbonized BC/carbon cloth as the negative electrode, delivering a high energy density of 47.3 W h kg^-1 at a power density of 828.9 W kg^-1, and superior cycling stability (91.4% capacitance retention after 3000 cycles). Therefore, this work provides a new path for high-performance flexible energy storage devices and offers a new vision for uniformly and robustly assembling nanohybrids.