Moiré-superlattice MXenes enabled ultra-stable K-ion storage in neutral electrolyte

Ti₃C₂ MXene is an auspicious energy storage material due to its metallic conductivity and layered assembly. However, in the real working condition of electrochemical energy storage with long cycle charging–discharging, a structural collapse is usually caused by the stacking of its layers creating a large attenuation of specific capacitance. Inspired by the superlattice effect of magic angle graphene, we conducted microscopical regulation of rotation mismatch on the Ti₃C₂ lattice; consequently, a hexagonal few-layered Ti₃C₂ free-standing film constructed with Moiré-superlattices. Such finding not only solves the problem of Ti₃C₂ structural collapse but also dramatically improves the specific capacitance of Ti₃C₂ as a supercapacitor electrode under long cycle charging and discharging. The ultra-stable energy storage of this electrode material in a neutral aqueous electrolyte was realized. Moreover, the formation mechanism of rotating Moiré pattern is revealed through microscopy and microanalysis of the produced Moiré pattern, assisted with modeling and analyzing the underlying mechanism between the Moiré pattern and the rotation angle. Our work provides experimental and theoretical support for future construction of Moiré-superlattice structure for a wide range of MXene phases and is undoubtedly promoting the development of MXene materials in the field of energy storage.