Reactivity-Driven Metal-Adaptive Interphases for Dendrite-Free, High-Rate Alkali Metal Anodes.

Alkali metal anodes (e.g., Li and Na) require a solid-electrolyte interphase (SEI) customized to their physicomechanical and electrochemical demands; however, conventional SEI designs relying on generic "one-size-fits-all" approaches fail to fully address the metal-specific requirements. Herein, a metal-adaptive SEI reconstruction strategy is proposed to leverage the reactivity-guided diisopropoxy-bisethylacetoacetatotitanate (DPBT) coatings on alkali metal anodes (TC-Li/TC-Na). The resulting interphases both share a hierarchical architecture with an ultrathin titanate layer and a TiO2-based inner matrix connected through compositionally graded segments (Ti-O-M, M = Li/Na/C), yet demonstrate metal-specific structural differentiation. The moderate reactivity of Li facilitates the dense packing of larger TiO2 nanoparticles, forming a low-porosity, high-modulus layer that mechanically suppresses dendrites. Conversely, the more rapid reaction of Na instantly produces abundant gas bubbles and fosters a highly porous network with interconnected ultrasmall TiO2 nanoparticles, integrating moderate modulus with elevated surface roughness that dynamically accommodates volumetric strain and enhances interfacial activity. Consequently, the NCM811||TC-Li pouch cell achieves high-capacity retention (89.3%, 200 cycles, 456.8 Wh kg-1) under 0.2 C/0.5 C and stable operation under high capacity and high energy density of 11.1 Ah and 550.2 Wh kg-1, while NFM||TC-Na pouch cell deliveries exceptional cycling stability at 0.3 C/1 C (79.7% retention over 200 cycles).