Carbon quantum dots boosted structure stability of nickel cobalt layered double hydroxides nanosheets electrodeposited on carbon cloth for energy storage

Flexible energy storage devices have gained a wide concern in latest years owing to their portable and practical characteristics. However, the capacitance decay of flexible energy storage devices and short cycle life limit their development. To solve these problems, we develop a simple electrodeposition method to enhance the electro-chemical activity and structural stability of the nickel cobalt layered double hydroxides (NiCoLDH) nanosheet arrays on carbon cloth (CC) by rational introduction of carbon quantum dots (CQD). Due to the induced effect and toughening effect of CQD, the obtained CQD modified NiCoLDH nanosheet arrays on CC electrode (CQD/ NiCoLDH@CC) not only exposes more active sites of NiCoLDH nanosheets to improve their electrochemical capacity, but also makes their structure more stable to enhance their cycle life. The optimized electrode of CQD/ NiCoLDH-3@CC can release a high specific capacitance of 1587.1 F g-1 at 1 A g-1 and maintain 1281.2 F g-1 at 20 A g-1, as well as good cycling stability with 60.1% capacitance retention after 10,000 cycles at 10 A g-1. The assembled flexible aqueous asymmetric CQD/NiCoLDH-3@CC//activated CC supercapacitor shows a high en-ergy density of 0.37 mWh cm-2 with the power density of 3.79 mW cm-2 at 5 mA cm-2. This work provides new insight into the designing of pseudocapacitive materials for energy storage.