[en] Transition metal nitrides (TMNs) are promising electrode materials for high-performance energy storage devices owing to their excellent conductivity, thermal stability, high theoretical capacity and excellent electrochemical activity. However, the structural instability present in the electrochemical reaction process significantly limits their widespread application. Herein, we present a V-Ni-based nitride heterojunction on carbon cloth (VN/Ni₃N-Ni/CC) as an active electrode material for flexible supercapacitors. The VN/Ni₃N-Ni/CC composite electrode was successfully fabricated through controllable nitridation of the corresponding vanadium-nickel oxide grown on carbon cloth (V-Ni-O/CC) precursors. The electrochemical results reveal that the areal capacitance of the VN/Ni₃N-Ni/CC based supercapacitor with a nitriding temperature of 400 C and a nitriding time of two hours can achieve a maximum areal capacitance of 845.63 mF cm^-2 at a current density of 0.5 mA cm^-2, and the electrode in the three-electrode system retains 86.1% of its initial capacitance value after 1500 cycles at a current density of 10 mA cm^-2. In addition, the assembled flexible all-solid-state symmetric supercapacitor using the VN/Ni₃N-Ni/CC electrode exhibits an areal capacitance ratio of 19.1 mF cm^-2 at a current density of 0.4 mA cm^-2 and excellent cycling stability. Moreover, it displays exceptional flexibility under different bending angles highlighting its potential for integration into flexible electronic devices. (authors)