<p>Supercapacitors are characterized by high safety, excellent rate performance, fast charging and discharging, long cycle life, and good cycling stability, making them ideal energy storage devices for applications ranging from portable electronic devices to renewable energy integration. As a kind of active materials for supercapacitors, LDHs have attracted much attention due to their tunable composition, efficient ion transport and abundant redox activity. In this study, Mn-doped (Mn)NiCo-LDH-X with 3D nanoflower structures are synthesized by a one-pot hydrothermal method. Most previously reported Mn-doped NiCo-LDHs are synthesized using MOF precursors and complex ion-exchange steps, which suffer from low yield, high cost, and poor scalability. In contrast, the strategy used in this work simplifies the synthesis by eliminating these steps, enabling better reproducibility and improved practicality. The introduction of Mn ions increases the degree of crystal defects and improves the electrical conductivity of the LDHs, which enhances their redox activity by promoting the diffusion of ions from the electrolyte to the surface of the electrodes. Due to the synergistic effect of the three transition metal ions, (Mn)NiCo-LDHs show a significant potential to be used as electrodes materials for supercapacitors, which can achieve a specific capacitance of 1709 F g⁻¹ at 1 A g⁻¹ and maintains a capacitance retention rate of 65.4% after 4000 cycles. Subsequently, the assembled (Mn)NiCo-LDH-1//AC asymmetric supercapacitor achieves an energy density of 43.8 W h kg⁻¹ at a power density of 750 W kg⁻¹.</p>