One-step in situ construction of interface-coupled MXene@FeZnCo-LDH heterostructures for high-performance supercapacitors

MXene-based electrodes offer rapid electron transport but often suffer from nanosheet restacking and limited electrolyte-accessible active sites. Here, MXene@MZnCo layered double hydroxide composites (MXene@MZnCo-LDH; M = Fe, Ni, Mn, and Al) were synthesized by a one-step in situ hydrothermal route to clarify how third-metal incorporation regulates structure, interfacial electronic properties, and charge storage. Among the four composites, the Fe-containing MXene@FeZnCo-LDH composite (MFZC) showed the highest surface area of 132 m2/g, a more continuous mesoporous structure, and lower charge-transfer resistance. After optimizing the MXene feed amount, MFZC-3 achieved 2210 F/g at 1 A/g, retained 66.10% of its capacitance at 10 A/g, and maintained 76.85% of its initial capacitance after 10,000 cycles. Kinetic analysis revealed that the charge-storage behavior arose from the combined effects of diffusion-limited and capacitive processes, while the capacitive fraction gradually increased with increasing scan rate. First-principles calculations revealed interfacial charge redistribution between MXene and FeZnCo-LDH. The asymmetric AC//MFZC-3 cell sustained 1.5 V operation, delivered 59.6 Wh/kg at 750 W/kg, and retained 73.53% of its initial capacitance after 10,000 cycles, indicating that third-metal regulation and interfacial coupling can improve MXene/LDH-based supercapacitor electrodes.