High-Performance Flexible Supercapacitors Using Diamond Cloth

A flexible supercapacitor is expected to possess a high power density and excellent cycling life and thus is a promising candidate for energy storage units in wearable and portable electronic devices. However, the drawback of a low energy density must be solved. In this context, a novel two-dimensional flexible capacitor material, diamond cloth, is proposed, which was prepared by overgrowing carbon cloth with a thin boron-doped diamond (BDD) film with the aid of a microwave plasma-enhanced chemical vapor deposition technique. As characterized by means of field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, such a diamond cloth features the characteristics of both conductive diamond films and carbon cloth. Namely, the exceptional chemical stability and good conductivity of the BDD film are combined with the high flexibility of carbon cloth, making diamond cloth a perfect capacitor electrode and exhibiting superior capacitance retention and cycling stability. An assembled symmetrical pseudocapacitor exhibits a specific capacitance of 81.94 mF cm–2 at a scan rate of 10 mV s–1, an extremely excellent capacitance retention of 99.59% even after 10,000 charging/discharging cycles, a maximal energy density of 45.96 μWh cm–2, and a maximal power density of 67.93 mW cm–2. Its performance exceeds that of most reported carbon-based supercapacitors. Furthermore, it demonstrates excellent mechanical flexibility, featuring the consistency of capacitance at different bending angles and the minimum capacitance retention of 97.14% for 500 bending cycles. Therefore, diamond cloth holds great potential for constructing energy storage units in wearable and portable electronic devices.