3d-transition metal (Fe, Co, Ni, and Mn)-based MXene materials have been predicted to demonstrate exceptional electrochemical performance because of their good electrical conductivity and the presence of metallic atoms with multiple charge states. However, until now, there have been no reports on MXenes based on Fe, Co, Ni, and Mn, due to the lack of 3d-metal-layered precursors. Herein, we successfully synthesized the first 3d-transition metal-based MXenes, Mn₂CT_x by exfoliating a layered precursor derived from the anti-perovskite bulk Mn₃GaC. The as-prepared Mn₂CT_x MXene nanosheets were employed as anode materials in lithium-ion batteries, which exhibited stable storage capacity of 764.7 mAh·g⁻¹ at 0.5 C, placing its storage capacities at an upper-middle level compared with other reported MXene materials as well as other Mn-based anode materials. Overall, this study opens a new avenue for MXene research by synthesizing 3d-transition metal-based MXenes for electrochemical applications.

Developing a simple scalable method to fabricate electrodes with high capacity and wide voltage range is desired for the real use of electrochemical supercapacitors. Herein, we synthesized amorphous NiCo-LDH nanosheets vertically aligned on activated carbon cloth substrate, which was in situ transformed from Co-metal–organic framework materials nano-columns by a simple ion exchange process at room temperature. Due to the amorphous and vertically aligned ultrathin structure of NiCo-LDH, the NiCo-LDH/activated carbon cloth composites present high areal capacities of 3770 and 1480 mF cm⁻² as cathode and anode at 2 mA cm⁻², and 79.5% and 80% capacity have been preserved at 50 mA cm⁻². In the meantime, they all showed excellent cycling performance with negligible change after >10000 cycles. By fabricating them into an asymmetric supercapacitor, the device achieves high energy densities (5.61 mWh cm⁻² and 0.352 mW cm⁻³). This work provides an innovative strategy for simplifying the design of supercapacitors as well as providing a new understanding of improving the rate capabilities/cycling stability of NiCo-LDH materials.