Facile and scalable fabrication of flexible micro-supercapacitor with high volumetric performance based on ultrathin Co(OH)2 nanosheets

Abstract

The rapid miniaturization of portable and wearable electronics has gained increasing demand for flexible and high-performance microscale energy storage devices such as micro-supercapacitors (MSCs) that provide flexibility and portability. Volumetric capacitance is the most significant metric for miniaturized capacitive energy storage units due to the limitations in device volume and active surface area. Herein, we have used an ultrathin (3.5 nm) two-dimensional (2D) Co(OH)₂ nanosheet (NS) as an electrode material to fabricate a flexible, solid-state MSC on micropatterned laser-scribed graphene (LSG). On account of the combination of ultrathin morphology, in-plane geometry of interdigitated microelectrodes, and highly conductive and robust interaction of ultrathin Co(OH)₂ NS and LSG, the Co(OH)₂ NS-LSG-based micro-supercapacitor (CN-LSG MSC) exhibits high rate-capability and delivers a superior volumetric capacitance of 258 F cm⁻³ at 13 A cm⁻³ current density. Moreover, the CN-LSG MSC device achieved an excellent energy density of 22 mW h cm⁻³ at a power density of 6.8 W cm⁻³ with a remarkable cyclic stability of 96.4% even after 20 000 charge–discharge cycles. The fabricated CN-LSG MSC exhibits unaffected mechanical flexibility under different bending deformations. Additionally, we have demonstrated the possibility of integrating a CN-LSG MSC by connecting it in series and parallel configurations, which amplifies the operating voltage and output current, respectively. Therefore, the present research work opens a new avenue for the simple and scalable manufacture of ultrathin film-based MSCs promising for various lightweight, miniaturized, flexible, and wearable electronics.