High-performance flexible hybrid supercapacitor based on NiAl layered double hydroxide as a positive electrode and nitrogen-doped reduced graphene oxide as a negative electrode

Abstract

Herein, we investigated the influence of Fe, Cr and Al incorporation in Ni-based layered double hydroxides (LDHs) supported on nickel foam (NF) electrodes, prepared through a one-step hydrothermal, on their electrochemical performance. The resulting NiFe, NiCr and NiAl (LDHs) were further coated on carbon spheres (CS) supported on NF using a facile two-step hydrothermal process to produce NiFe LDHs@CS/NF, NiCr LDHs@CS/NF and NiAl LDHs@CS/NF. The performance of the prepared materials as binder-free electrodes in supercapacitors was assessed. Among all the prepared electrodes, NiAl LDHs@CS/NF electrode material achieved the largest areal capacity (1042.2 mC cm−2 at 1 mA cm−2), as compared to the areal capacity values attained by NiFe LDHs@CS/NF (705.8 mC cm−2) and NiCr LDHs@CS/NF (814.9 mC cm−2) at 1 mA cm−2. Therefore, a hybrid supercapacitor device comprising NiAl LDHs@CS/NF as the positive electrode and N-doped reduced graphene/NF as the negative electrode was successfully fabricated. The device exhibited favorable flexibility, good mechanical properties and stability; the areal capacity remained ∼75% and ∼67% of the original value after 5000 and 10,000 cycles, respectively. The hybrid supercapacitor attained an energy density of 43 μWh cm−2 at a power density of 0.805 mW cm−2 and was applied successfully to operate a home-made windmill device continuously for 32 s. Moreover, two flexible NiAl LDHs@CS/NF//N-rGO/NF hybrid supercapacitors, connected in series, were able to light up a green, a red and a yellow LED in parallel, lasting for 37 s, 542 s and 199 s, respectively, indicating their potential application for flexible energy storage devices.