Self-Transformed MOF-on-MXene Heterostructure as an Ion-Expedited Interphase toward Low-Temperature Multivalent Metal Batteries.

Rechargeable aqueous multivalent metal batteries (AMMBs) are promising for next-generation safe energy storage systems owing to their high energy density and cost-effectiveness. However, strong ion-dipole interactions hinder desolvation and diffusion, resulting in large energy barriers and sluggish kinetics. To address these kinetic limitations, we develop a catalytic heterostructure comprising a porous, electron-delocalized metal-organic framework (MOF) integrated with MXene. This heterostructure is fabricated via partial self-transformation of Ti3C2Tx MXene into Ti-MOF (NH2-MOF-MXene), forming a Ti-MOF-MXene heterostructure. Acting as a kinetic promoter, it weakens electrostatic ion-dipole interactions, thereby accelerating interfacial Zn2+/Al3+ desolvation and diffusion while inhibiting dendrite formation, as confirmed by spectroscopic and electrochemical measurements. Moreover, the porous structure and electron-delocalized -NH2 polar groups effectively suppress active water formation from the solvation shell, thus inhibiting the hydrogen evolution reaction (HER). Consequently, symmetric Zn cells incorporating the NH2-MOF-MXene heterostructure achieve dendrite-free Zn plating with an extended lifespan of approximately 1000 h and high Coulombic efficiency under low temperatures (0 °C and -20 °C). Similarly, symmetric Al//Al cells incorporating the same heterostructure operate with reduced overpotentials and show improved stability from 100 to 220 h compared with bare Al//Al cells. These results establish an electron-delocalization pathway toward high-performance AMMBs.