Alternate Integration of Vertically Oriented CuSe@FeOOH and CuSe@MnOOH Hybrid Nanosheets Frameworks for Flexible In-Plane Asymmetric Micro-supercapacitors

Two-dimensional transition metal oxyhydroxide (MOOH) nanostructures show great potential for application in catalysis, sensing, secondary batteries, and supercapacitors fields. Nonetheless, it is still a challenge to orient and hybridize MOOH nanosheets with carbon-free conductive materials (e.g., CuSe), and their uses in flexible in-plane asymmetric microsupercapacitors (AMSCs) are not explored. Herein, vertically oriented CuSe@FeOOH and CuSe@MnOOH hybrid nanosheet frameworks are alternately integrated on Au interdigital electrodes/polyethylene terephthalate substrate through a successive electrodeposition strategy without any template. Because of the unique geometric motifs and composition combination, those hybrid nanosheets frameworks exhibit greatly enhanced specific capacitance (543.9 F g-1 for CuSe@FeOOH, 422.9 F g-1 for CuSe@MnOOH). An in-plane AMSCs (CuSe@FeOOH//CuSe@MnOOH) is directly assembled by using poly(vinyl alcohol)-LiCl gel as the electrolyte. The as-fabricated AMSCs manifests large areal capacitance (20.47 mF cm-2), remarkable cycle stability (95% remained after 32 »000 cycles), excellent flexibility and mechanical stability. Moreover, it also exhibits a high volumetric energy density of 16.0 mW h cm-3 and a power density of 1299.4 mW cm-3, outperforming most recently reported in-plane microsupercapacitors. This work may promote the development of MOOH-based two-dimensional heteronanostructures and accelerate their applications in flexible energy storage or other clean energy fields.