An asymmetric supercapacitor with ultra-high energy density and long cycle life based on La(OH)3 nano-spindles and nano-rods anchored on reduced graphene oxide

Abstract

The reduced graphene oxide (rGO)/La(OH)3 composite is prepared by a simple microwave-assisted synthesis method. The micromorphology of La(OH)3 is the spindle-like and rod-like architectures through the field emission scanning electron microscope and transmission electron microscope. The obtained rGO/La(OH)3 displays a maximum specific capacitance of 757 F g−1 at a current density of 0.5 A g−1. An asymmetric supercapacitor of rGO/La(OH)3||rGO is assembled, which exhibits an energy density of 90.5 Wh kg−1 at a power density of 100 W kg−1. In addition, the capacitance retention ratio of the rGO/La(OH)3||rGO reaches 91.8% at a current density of 1 A g−1 after 10,000 charge/discharge cycles. Ultrahigh energy density and a long cycle life are attributed to the rGO which provides conductive substrates, and the anchoring of a thin, homogeneous, and conformal La(OH)3 layer on the surface of the rGO, which shortens ion transportation paths. The rGO/La(OH)3||rGO is a promising device for supercapacitors.