Low‐cost nickel‐based hydroxides with multiple valence states are excellent alternative supercapacitor (SC) electrode materials. However, their practical application is severely restricted by poor conductivity and unstable reaction kinetics. In this study, a highly interconnected nickel carbonate hydroxide nanosheet‐wire structure (Ni Ns‐w) was prepared by carefully controlling the urea content used during reflux synthesis. Compared to nickel hydroxide nanosheets, Ni Ns‐w has a high specific capacitance (1160.7 F g−1), high rate capability (611.9 F g−1 at 10 A g−1), and excellent cycling stability (80.43% capacitance retention after 5000 cycles) due to the intimate connection between the nanosheets and nanowires that provides an abundant carrier transport paths, high structural stability, and a large reaction area. At the same time, the carbonate ions further enhance the electrochemical properties by increasing the wettability of the electrode materials and reducing the polarization during charge‐discharge process. The corresponding asymmetric SC realized a high power density and a high energy density (9.0 kW kg−1 and 24.0 Wh kg−1, respectively). As a result, Ni Ns‐w is an excellent candidate material for use in energy storage cells.