Inlaid layered double hydroxides and MXene composite electrodes with high rate performance as asymmetric supercapacitors

Layered double hydroxides (LDHs) have attracted widespread attention due to the high electrochemical activity as energy reserves. Nevertheless, the problems of the self-stacking and low conductivity of LDHs limit their development on supercapacitor. In this paper, the NiAl-LDH (NA-LDH) with the large specific capacitance is embedded on the MXene (Ti₃C₂T_x) with excellent conductivity by facile electrostatic self-assembly process. The composite electrode shows a high specific capacitance (C_s,1276.83 F g⁻¹) at 1 A g⁻¹, when the mass ratio of MXene to NA-LDH is 3:7 (M3L7). Besides, M3L7 emerges a quite marvelous rate capability at 10 A g⁻¹. The capacitance retention rate reaches 92.3%, which is far higher of pristine NA-LDH material (27.7%). After 4000 cycles, M3L7 electrode represents outstanding capacitance retention of 81.16% at 6 A g⁻¹, which is superior to pure NA-LDH (58.1%). The enhanced electrochemical performance of this composite could be attributed to the combination of NA-LDH with large specific capacitance and wrinkled MXene, which increases the interfacial charge transfer performance. Furthermore, an aqueous asymmetric supercapacitor device assembled with M3L7 anode and activated carbon cathode shows a high energy density of 37.86 Wh kg⁻¹ at 1056.55 W kg⁻¹ and displays outstanding cycle stability with 86% capacitance retention after 4000 cycles and the morphology changes slightly. This electrode material has wide application prospects in the high-performance energy storage field.