Ultrahigh Energy Density Realized by a Single-Layer β-Co(OH)2 All-Solid-State Asymmetric Supercapacitor

A conceptually new all-solid-state asymmetric supercapacitor based on atomically thin sheets is presented which offers the opportunity to optimize supercapacitor properties on an atomic level. As a prototype, beta-Co(OH)(2) single layers with five-atoms layer thickness were synthesized through an oriented-attachment strategy. The increased density- of-states and 100% exposed hydrogen atoms endow the bCo( OH)(2) single-layers-based electrode with a large capacitance of 2028 Fg(-1). The corresponding all-solid-state asymmetric supercapacitor achieves a high cell voltage of 1.8 V and an exceptional energy density of 98.9 Whkg(-1) at an ultrahigh power density of 17981 Wkg(-1). Also, this integrated nanodevice exhibits excellent cyclability with 93.2% capacitance retention after 10000 cycles, holding great promise for constructing high-energy storage nanodevices.