Three-dimensional porous MXene-derived carbon/nickel-manganese double hydroxide composite for high-performance hybrid capacitor

A three-dimensional (3D) hierarchically MXene-derived carbon/nickel-manganese layered double hydroxide nanosheets composite (MDC/NiMn-LDH) is constructed by a facile in situ growth route. Such unique 3D structure could provide fast and short pathway for electron and ion transfer, but also sufficiently expose active area for redox reactions of NiMn-LDH. The electrochemical investigation indicates that the optimized MDC/Ni5Mn1-LDH composite delivers a high specific capacity of 228 mAh g(-1) at 1 A g(-1), remarkable rate capability with 158 mAh g(-1) retention at 10 A g(-1), and excellent cycling stability of 74% retention with 122 mAh g(-1) after 4500 cycle tests at 8 A g(-1). In addition, a high-performance alkaline hybrid capacitor is fabricated based on the MDC/Ni5Mn1-LDH positive electrode and the 3D ordered porous carbon nanosheets (aPCNs) negative electrode, which manifests a high energy density of 45.2 Wh kg(-1) at a power density of 802 W kg(-1).