Interface engineering is an effective approach to solve the knotty Li-dendrite issues in lithium-metal batteries, and yet the robust large-capacity Li anode(>20 mAh cm−2) working at ultrahigh rate density(>20 mA cm−2) is still rarely attained. Herein, an integrated Li-metal-based anode with a top-down composition gradient (Li2O-LiOH-Li3Sb/Li) is constructed through a thermal-induced reaction of molten Li with polyantimonic acid (PAA). Unexpectedly, the lattice-water-containing PAA is found in favor of a mild but homogeneous lithiation reaction, whilst accompanying by a spontaneous phase separation between the resulting Li2O, LiOH, and Li3Sb components due to their significant interfacial energy discrepancy. The consequent Li2O-enriched top layer affording high Young’s modulus (>10 GPa) and electron-shielding ability can effectually suppress the Li-dendrite growth, while the underlying LiOH-Li3Sb interphase as ionic channels homogenize Li+-flux distribution in turn enabling dendrite-free Lideposition in lithiophilic Li3Sb/Li bottom layer. With this free-standing integrated electrode, large-areal-capacity symmetrical cells (25 mAh cm−2) can maintain over 1280 h Li plating/stripping cycles at ultrahigh-current-density of 50 mA cm−2, and the full-cells paired with high-capacity LiCoO2 (3.5 mAh cm−2) exhibit improved cycling stability under practical low N/P ratio (1.33). Importantly, such robust integrated anode also showcases decent compatibility with gel-polymer/Li7La3Zr2O12 solid-state electrolytes, signifying the application potential in safe Li metal batteries.