Rational design of hierarchical Ni(OH)2–MnO2 nanoflowers @Ti3C2Tx nanosheets heterostructure as advanced symmetric supercapacitors

MXenes, as a two-dimensional transition metal carbide or nitride based electrode material with excellent performance, shows excellent performance similar to graphene, which is considered as an ideal electrode material for supercapacitors. However, the application of two-dimensional lamellar Ti₃C₂Tx is limited by its low theoretical specific capacity and easy agglomeration between layers. Herein, through a simple hydrothermal synthesis strategy, we introduced three-dimensional (3D) Ni (OH)₂–MnO₂ nanoflowers between layered Ti₃C₂T_x sheets to form a unique 3D hierarchical pillared structure, which not only solves the problem of easy agglomeration between Ti₃C₂T_x layers, but also gives play to the advantage of Ni(OH)₂ and MnO₂ as the high specific capacitance of metal compounds, and this composite obtained shows the synergistic effect between components. In addition, due to its three-dimensional structure, Ni(OH)₂–MnO₂ nanoflowers can effectively hinder the accumulation of Ti₃C₂Tx nanosheets, thereby increasing their active electrochemical degree points and promoting the transport of electrolytes. Furthermore, the three-dimensional pillared Ni(OH)₂–MnO₂@Ti₃C₂Tx composite we prepared displays a large specific capacitance of 2523 F g⁻¹ at 2 mV s⁻¹. At the high current density of 10 A g⁻¹, after 10,000 cycles, the electrode material finally maintained 88.1% of the initial specific capacitance, which proved its remarkable cycle stability. Moreover, the energy density and power density of the symmetrical supercapacitor (SSC) made of this composite materials are 36.3 Wh kg⁻¹ and 421.5 W kg⁻¹, respectively. All above results indicate that the easy preparation method, low cost, Ni(OH)₂–MnO₂@Ti₃C₂Tx composites with excellent performance will be suitable for different application scenarios of multifunctional and digital supercapacitors.