Black phosphorus (BP) has been demonstrated
as a promising electrode
material for supercapacitors. Currently, the main limitation of its
practical application is the low electrical conductivity and poor
structure stability. Hence, BP-based supercapacitors usually severely
suffer from low capacitance and poor cycling stability. Herein, a
chemically bridged BP/conductive g-C3N4 (BP/c-C3N4) hybrid is developed via a facile ball-milling
method. Covalent P–C bonds are generated through the ball-milling
process, effectively preventing the structural distortion of BP induced
by ion transport and diffusion. In addition, the overall electrical
conductivity is significantly enhanced owing to the sufficient coupling
between BP and highly conductive c-C3N4. Moreover,
the imbalanced charge distribution around the C atom can induce the
generation of a local electric field, facilitating the charge transfer
behavior of the electrode material. As a result, the BP/c-C3N4-20:1 flexible supercapacitor (FSC) exhibits an outstanding
volumetric capacitance of 42.1 F/cm3 at 0.005 V/s, a high
energy density of 5.85 mW h/cm3, and a maximum power density
of 15.4 W/cm3. More importantly, the device delivers excellent
cycling stability with no capacitive loss after 30,000 cycles.