Interdigital electrodes of air@NiO porous nanoshells for high performance microsupercapacitors by thermally-assisted...

Microsupercapacitors of air@NiO porous nanoshells are manufactured by a novel thermally-assisted 3D printing process. It entails the use of printing inks of the moderate solid content of CNT-PS@Ni-precursor-nanoparticle mixture, a real-time heating substrate to print 3D interdigital electrodes, and subsequent thermal annealing to convert PS@Ni-precursor particles into air@NiO porous nanoshells. The microstructure of 3D printed electrodes is characterized by air@NiO porous nanoshells being well dispersed in the CNT network. The CNT network provides a fast electronic migration path and meanwhile ensures the mechanical integrity of electrodes to prevent the fracture and/or collapsing of electrode structures during 3D printing manufacturing and charging/discharging cycles. The air@NiO porous nanoshells, manufactured in our labs, consist of randomly oriented nanosheets and offer superb charge storage via redox reactions. The metal layer is sputtered indiscriminately on the surface of interdigital electrodes and substrate before it is peeled off with electrolyte film and electrodes. The proposed tactic resolves problems connected with the tedious courses of traditional lithography and the delamination at the interface of active materials and collectors from mechanical stress. Experiments were conducted to study the performance of the microsupercapacitors (i.e. areal capacitances, energy and power densities) as a function of printing parameters, such as electrode heights, embedded amount of air@NiO porous nanoshells and the thickness of the metal layer on the electrochemical characteristics. The thickness of as-printed electrodes reaches up to 117 μm, which is vital in ensuring high energy density and is beyond the reach of any other technology. Moreover, the 3D printedmicrosupercapacitors of air@NiO porous nanoshells show excellent cycle stability and deliver an excellent areal capacitance of 56.7 mF cm^-2, about a magnitude or two higher than that of C-based counterparts.