Highly Nanoporous\nNickel Foam as Current Collectors\nin 3D All-Solid-State Microsupercapacitors

This study reports\na streamlined method for producing\na highly\nnanoporous current collector with a substantial specific surface area,\nserving as an electrode for microsupercapacitors (MSCs). Initially,\ncommercial Ni foams are patterned into an interdigitated structure\nby laser cutting. Subsequently, the Ni foams are infused with NiO\nnanopowders through dip coating, sintering, and reduction in an H<sub>2</sub> atmosphere, followed by the growth of MnO<sub>2</sub> through\na redox reaction. The incorporation of NiO within this three-dimensional\nNi current collector results in notable porosity within the range\nof approximately 200–600 nm. Such a 3D, highly nanoporous electrode\ndramatically increases the specific surface area by 30 times and substantially\nboosts the amount of active material deposition, surpassing those\nof commercially available Ni foams. Performance evaluations of this\nhighly nanoporous electrode in a 1 M KOH solution demonstrate an areal\ncapacity of 19.3 F/cm<sup>2</sup>, retaining more than 95% capacitance\nat 5 mA/cm<sup>2</sup>, and exhibiting an energy density of 671 μW\nh/cm<sup>2</sup>, 25 times greater than commercial Ni foams. Moreover,\nin the realm of solid-state applications for MSCs, the remarkably\nhigh porous electrode achieves a commendable areal capacity of 7.22\nF/cm<sup>2</sup> and an energy density of 263.9 μW h/cm<sup>2</sup>, rendering it exceptionally suitable for use in MSC applications.