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.

Few-layered 2D analogs exhibit new physical/chemical properties, leading to a strong research interest and broad areas of application. Recently, lots of methods (such as ultrasonic and electrochemical methods) have already used to prepared 2D materials. However, these methods suffer from the drawbacks of low yield, high cost, or precarious state, which limit the large-scale applications. Inspired by the famous Scotch tape method, we develop a ball-milling with polymer “tape” method, fabricating few-atomic-layered material, showing the high-yield, low-cost, and much stability. As electrode material, ultrathin 2D materials can shorten the ion transfer pathway, contributing to the development of high-power batteries. Meanwhile, few-atomic-layered structure can expose more active sites to increase their capacity, showing special energy storage mechanism. We use the as-prepared few-atomic-layered Bi (FALB) and reduced oxide graphene composites as the anode for potassium/sodium-ion batteries (KIBs/NIBs). The sample achieves a high reversible capacity of 395 mAh g⁻¹ for KIBs, of which FALB contributes 438 mAh g⁻¹ (higher than the theoretical capacity of Bi, 386 mAh g⁻¹), and it carries outstanding cycle and rate performance in KIBs/NIBs.