Strongly coupled carbon quantum dots/NiCo-LDHs nanosheets on carbon cloth as electrode for high performance flexible supercapacitors

NiCo-LDHs is one of the most promising electrode materials for supercapacitors. However, the intrinsic low conductivity and the volume expansion/contraction still seriously limit the application of NiCo-LDHs in super capacitors. Herein, we constructed carbon quantum dots (CQDs)/NiCo-LDHs nanosheets heterostructures on carbon cloth (CQDs/NiCo-LDHs@CC) through a simple solvothermal method using CQDs-embedded Co-MOF as precursor. The in-situ implanting of CQDs not only can effectively improve the conductivity of the NiCo-LDHs but also boost the long-term structural stability of the flexible electrode through the morphological optimization of NiCo-LDHs. Benefit from the ingenious structural design and strong coupling between CQDs and NiCo-LDHs, the CQDs/NiCo-LDHs@CC electrode delivered a much-enhanced capacitance performance in 6 M KOH, including a large reversible specific capacitance of 2023 F g(-1) (5.22 F cm(-2)) at 5 mA cm(-2), superior rate capability with 84.3% capacitance retention at 30 mA cm(-2) and excellent cycle life. The flexible asymmetric supercapacitor device exhibited an energy density of 117.8 Wh kg(- 1) with a power density of 528.3 W kg(-1) at 2 mA cm(-2) using CQDs/NiCo-LDHs@CC as positive electrode and activated CC as negative electrode. This work provides a new opportunity for the development of nanocomposites with the in-situ implanting of CQDs to construct highperformance electrodes for flexible supercapacitors.