In situ preparation of nitrogen-doped carbon nanotubes on carbon cloth surface as binder-free flexible electrode materials for supercapacitors

It is very important to develop electrode materials with good mechanical flexibility and excellent electrochemical performance to adapt to the development of flexible electronic devices, and the preparation of non-binder flexible electrode is a good strategy. In this work, nitrogen-doped carbon nanotubes (N-CNT) were grown in situ on the surface of carbon cloth (CC) by a simple method and directly used as binder-free electrodes for supercapacitors. The electrochemical tests show that the electrode can achieve an areal capacitance of 4081.6 mF/cm² when the ampere density is set at 2mA/cm², and when the ampere density is promoted 10 times to 20mA/cm², this electrode can still retain 72.8% of the areal capacitance at 2mA/cm². The flexible electrode can also retain 90.3% of an areal capacitance after 5000 recharge/discharge cycles at a set ampere density of 10 mA/cm² and 97.6% of its areal capacitance after 50 bending cycles. The electrode was assembled into a symmetrical supercapacitor for electrochemical performance testing, and an areal capacitance of 572.6 mF/cm² can be maintained when the ampere density is set at 2 mA/cm², and an energy density of 79.53 and 40.28 µWh/cm² at a power density of 1000 and 10,000µW/cm², separately. The excellent electrochemical performance is mainly attributed to the following three points: (1) No binder is used to avoid the problems that affect the conductivity and utilization rate of active substances caused by the binder. (2) The electrode material has a large specific surface area and has more active sites for electrochemical reaction. (3) The presence of N and O is of great help to improve the electrochemical performance of the electrode material.