N-doped carbon nanosheets/vanadium nitride nanoparticles (N-CNS/VNNPs) are synthesized via a novel method combining surface-initiated in-situ intercalative polymerization and thermal-treatment process in NH3/N2 atmosphere. The pH value of the synthesis system plays a critical role in constructing the structure and enhancing electrochemical performance for N-CNS/VNNPs, which are characterized by SEM, TEM, XRD, and XPS, and measured by electrochemical station, respectively. The results show that N-CNS/VNNPs materials consist of 2D N-doped carbon nanosheets and 0D VN nanoparticles. With the pH value decreasing from 2 to 0, the sizes of both carbon nanosheets and VN nanoparticles decreased to smaller in nanoscale. The maximum specific capacitance of 280 F g-1 at the current density of 1 A g-1 for N-CNS/VNNPs is achieved in three-electrode configuration. The asymmetric energy device of Ni(OH)2||N-CNS/VNNPs offers a specific capacitance of 89.6 F g-1 and retention of 60% at 2.7 A g-1 after 5000 cycles. The maximum energy density of Ni(OH)2 ||N-CNS/VNNPs asymmetric energy device is as high as 29.5 Wh kg-1.