NiMnCr layered double hydroxide-carbon spheres modified Ni foam: An efficient positive electrode for hybrid supercapacitors

New electrode composite materials, consisting of NiMnCr layered double hydroxides (LDHs) coated on carbon spheres (CS) supported on nickel foam (NiMnCr [email protected]/NF), were synthesized using a two step hydrothermal process. The obtained binder-free NiMnCr [email protected]/NF composite was investigated as a positive electrode for supercapacitors and achieved a high specific capacity of 569 C g−1 at 3 A g−1; this value was ~6.5 times that of CS/NF (87.9 C g−1 at 3 A g−1) and ~3.3 times that of NiMnCr LDHs/NF composite (173.2 C g−1 at 3 A g−1). The NiMnCr [email protected]/NF composite retained ~76% of its original capacity after 10,000 cycles, much better than ~54% achieved by NiMnCr LDHs/NF composite, suggesting good reversibility and stability. Furthermore, a hybrid supercapacitor was fabricated using NiMnCr [email protected]/NF as the positive electrode and FeOOH nanorods deposited on NF (FeOOH/NF) as the negative electrode. The hybrid supercapacitor displayed an energy density of 48 Wh kg−1 at a power density of 402.7 W kg−1. A home-designed windmill device was successfully driven by the as-fabricated supercapacitor device for about 25 s. Additionally, two as-fabricated hybrid supercapacitor cells in series were used to light up a yellow LED and a red LED in parallel for ~111 s and ~343 s, respectively. Taken together, these results indicate that the developed electrodes hold a promising potential in energy storage application.