2,6-Diaminoanthraquinone modified MXene (Ti₃C₂T_x)/graphene as the negative electrode materials for ionic liquid-based asymmetric supercapacitors

Due to insufficient energy density, supercapacitors (SCs) with preeminent-power and long cycle stability cannot be implemented in some practical applications. Exploring hybrid materials with redox activity to emerge high specific capacitance in ionic liquid (IL) electrolytes can solve this problem. Herein, we report a redox-organic molecule 2,6-diaminoanthraquinone (DAAQ) modified MXene (2,6-Diaminoanthraquinone modified MXene (Ti₃C₂T_x)/graphene as the negative electrode materials for ionic liquid-based asymmetric supercapacitors)/Graphene (DAAQ-M/G) composite material. With the assist of graphene oxide (GO), MXene and graphene fabricate a three-dimensional (3D) interconnected structure as a conductive framework, which inhibits self-stacking of MXene monolayers and ensures high electronic conductivity. Meanwhile, DAAQ is loaded onto the M/G framework through covalent/non-covalent functionalization. The DAAQ as a spacer effectively enlarges the interlayer spacing of MXene nanosheets, and meanwhile produces reversible redox reactions during charge/discharge processes to provide additional Faradaic contribution to capacity. Therefore, the specific capacitance (capacity) of the DAAQ-M/G as the negative electrode material reaches to 226 F g^-1 (306 C g^-1) at 1 A g^-1 in 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF₄) electrolyte. Furthermore, an asymmetric supercapacitor (ASC) is assembled using DAAQ-M/G as the negative electrode and self-prepared organic molecule hydroquinone modified reduced graphene oxide (HQ- RGO) material as the positive electrode, with a high energy density of 43 Wh kg^-1 at high power density of 1669 W kg^-1. The ASC can maintain 80% of initial specific capacitance after 9000 cycles. This research can provide better support to develop advanced organic molecules-modified MXene composite materials for ionic liquid-based SCs.