Navigating Inner Helmholtz Plane Reactions Enables Robust Lithium Metal Anodes for 500 Wh kg‑1 Pouch Cells

Stabilizing Li metal anodes remains a central challenge due to the difficulty of establishing the stable electrode/electrolyte interface, arising from dynamic potential fluctuations within the inner Helmholtz plane. Here, we propose a preoccupancy-guided interfacial regulation strategy that decouples electric-field effects from interfacial reduction processes. A Schiff-base polymer with terminal C–F fragments spontaneously establishes a preferential surface-normal orientation across the inner Helmholtz plane, thereby defining a preoccupied and spatially confined interfacial environment that suppresses solvent access to the Li surface. Coupled with the electron-withdrawing effect of its fluorinated moieties, the interfacial electronic environment is modulated, facilitating the preferential formation of a LiF-rich interphase on Li metal. Meanwhile, the abundant F/N coordination sites in the unreacted polymer serve as a soft organic outer layer that accelerates Li-ion desolvation and diffusion. Benefiting from these features, the fine-tuned solid electrolyte interphase integrates chemical stability, mechanical robustness, and efficient Li-ion transport, enabling the fabricated 4.81 Ah pouch cell to deliver an energy density of 502.43 Wh kg–1 and maintain ∼90.06% of its initial capacity after 240 cycles. Our findings reveal that precise tuning of the chemical environment within the inner Helmholtz plane effectively suppresses uncontrolled electrochemical-derived interphase formation, paving the way toward the rational design of a stable Li metal/electrolyte interface.