Silver-Quantum-Dot-Modified MoO ₃ and MnO ₂ Paper-Like Freestanding Films for Flexible Solid-State Asymmetric Supercapacitors

Free-standing paper-like thin-film electrodes have great potential to boost next-generation power sources with highly flexible, ultrathin, and lightweight requirements. In this work, silver-quantum-dot- (2–5 nm) modified transition metal oxide (including MoO ₃ and MnO ₂ ) paper-like electrodes are developed for energy storage applications. Benefitting from the ohmic contact at the interfaces between silver quantum dots and MoO ₃ nanobelts (or MnO ₂ nanowires) and the binder-free nature and 0D/1D/2D nanostructured 3D network of the fabricated electrodes, substantial improvements on the electrical conductivity, efficient ionic diffusion, and areal capacitances of the hybrid nanostructure electrodes are observed. With this proposed strategy, the constructed asymmetric supercapacitors, with Ag quantum dots/MoO ₃ “paper” as anode, Ag quantum dots/MnO ₂ “paper” as cathode, and neutral Na ₂ SO ₄ /polyvinyl alcohol hydrogel as electrolyte, exhibit significantly enhanced energy and power densities in comparison with those of the supercapacitors without modification of Ag quantum dots on electrodes; present excellent cycling stability at different current densities and good flexibility under various bending states; offer possibilities as high-performance power sources with low cost, high safety, and environmental friendly properties.