CoNi–P/MXene With Yolk–Shell Hollow Structure as High‐Performance Supercapacitor Electrode Material

Transition metal phosphides exhibit high specific capacitance. However, their practical application is limited by volume expansion and structural instability during charging and discharging. In this study, a CoNi–P yolk–shell structure was synthesized using hydrothermal and calcination methods and combined with two‐dimensional titanium carbide (MXene) to construct a stable CoNi–P/MXene conductive network. The yolk–shell structure mitigates volume effects and shortens the electron transport path, while MXene enhances the structural stability and cycle life. The CoNi–P/MXene composite exhibits a specific capacitance of 964 F g ⁻¹ . In addition, adjusting the MXene content affects the electrochemical performance. Notably, an asymmetric supercapacitor using CoNi–P/MXene and activated carbon as the positive and negative electrodes, respectively, displays a capacitance retention rate of 90.1% after 16,000 cycles at a current density of 5 A g ⁻¹ and delivers an energy density of 44.64 Wh kg ⁻¹ at a power density of 800 W kg ⁻¹ . Therefore, the proposed CoNi–P/MXene electrode material shows excellent prospects for energy storage applications.