In-situ construction of 2D/2D Mo₂C-derived heterojunction optimizes ionic transport for high-performance lithium-ion...

The energy storage mechanism for MXenes depends largely on surface adsorption and pseudocapacitive nature and hence is limited by their natural capacity. To address this issue, the study proposes a novel method for preparing Mo₂C/MoO₃ 2D/2D heterostructured composites through controlled high-temperature oxidation of Mo₂CT_x. As-prepared heterostructure significantly accelerates lithium-ion transmission kinetics by suppression of the migration energy barrier, considerably boosting electrochemical performances. Specifically, discharge capability of Mo₂C/MoO₃-composite reaches appreciable level of 863 mAh g^-1, significantly outperforming pristine Mo₂CT_x (480 mAh g^-1), and good rate capability and long cycling lifetime. Such new 2D/2D architecture effectively suppresses volume expansion by cycling and enhances ionic conductivity. Through in-situ X-ray diffraction, there is an irreversible lithium-ion insertion process in Mo₂C/MoO₃ framework by the first cycling. Furthermore, theoretical calculation also confirms a reduced barrier of lithium-ion diffusion as 0.46 eV, consistent with good rate capability exhibited by this material. This work not only advances MXene-derived materials development but also enables fundamental understanding on high-performance design principle on anode for future lithium-ion battery developments.