Biomass-derived carbon dots regulating nickel cobalt layered double hydroxide from 2D nanosheets to 3D flower-like spheres as electrodes for enhanced asymmetric supercapacitors

[Display omitted] •Nickel cobalt layered double hydroxide regulated by fungus bran-derived carbon dots are firstly synthesized.•Carbon dots are used for the adjustment of 2D nanosheets to 3D flower-like spheres.•The spherical morphology provides more electro-active sites.•An asymmetric supercapacitor device shows higher energy density. Layered double hydroxides (LDHs) often require the use of carbon materials to improve their stability, conductivity, and specific surface area to accommodate new directions in the development of high-performance energy storage materials. Herein, 2D nickel cobalt layered double hydroxide (NCLDH) nanosheets are regulated to form 3D flower-like spheres by fungus bran-derived carbon dots (CDs) via an in situ growth method. The prepared sample (CDs/NCLDH) shows abundant accessible active sites and favorable electrical conductivity, which is aided by strong interactions between CDs and NCLDH. The optimized CDs/NCLDH exhibits significantly enhanced electrochemical performances, including ultrahigh specific capacitance (2100F g−1 at 1 A g−1) and a great rate capability, which are two times higher than those of the NCLDH electrode. Additionally, the asymmetric supercapacitor device assembled with the CDs/NCLDH positive electrode and the fungus bran-derived activated carbon (FBC) negative electrode achieves a superior energy density of 52.5 Wh kg−1 at an ultrahigh powder density of 750 W kg−1. With their simple synthesis method and excellent electrochemical performance, the role of the CDs provides new insights for the development of LDHs with improved performance.