Construction of nitrogen-doped graphene quantum dot embedded NiGa layered double hydroxide for high-performance asymmetric supercapacitors

Layered double hydroxides (LDHs) are a promising positive electrode material for super-capacitors (SCs) due to multiple oxidation reduction states. However, the structure of LDH is prone to collapse during the redox reaction and has low conductivity, which further hinders the improvement of capacity performance. Here in, nitrogen-doped graphene quantum dot (N-GQD) is assembled on nickel gallium layered double hydroxide (NiGa-LDH) derived from two-dimension nickel metal organic frameworks (Ni-MOF) on nickel foam (NF) to prepare stable interlaced nano-sheets hybrid structures. As a result of the above synergies, the NiGa-LDH/N-GQD/NF electrode has a high specific capacitance of 2160 F g−1 at 1 A g−1 and good cycling stability with a capacity retention rate of 87.5% in 5000 cycles. In addition, we also make ASC device using NiGa-LDH/N-GQD/NF and Carbon NSs as positive/negative electrodes. The energy density of the assembled ASC device is 78.8 Wh kg−1 at power density of 1432.7 W kg−1, while the capacitance retention after 8000 cycles reaches 81.2%. Meanwhile, individually assembled ASC device can power multiple LEDs in parallel. This work provides an effective way to construct new electrode materials with high energy storage density, good cycling performance and power density by assembling quantum dots into LDH nano-sheets derived from MOF through reasonable design.