Synergistic Orbital Hybridization and Steric Shielding for Stabilizing High-Voltage Interfaces in 4.3 V Sodium-Ion Batteries.

High-voltage polyanionic cathodes, such as Na3V3(PO4)2F3 (NVPF), are pivotal for high-energy-density sodium-ion batteries but are fundamentally constrained by severe parasitic reactions at the desodiated interface. These reactions driven by unsaturated vanadium sites and solvent enrichment cause rapid capacity fade. Herein, we propose a molecular interfacial engineering strategy using rationally designed organic phosphate additives. These additives stabilize vanadium via π-d orbital hybridization and regulate the interfacial microenvironment through three-dimensional steric shielding, passivating reactive species, and suppressing solvent enrichment. Guided by a descriptor-driven screening process (Mulliken charge, van der Waals volume, O 2p band center, ΔE (O 2p band center-V 3d band center)), tris(trimethylsilyl) phosphate (TMSP) is identified as the optimal electrolyte modifier. The TMSP-tailored electrolyte promotes in situ formation of a thin, compact, and inorganic-rich interphase on both the NVPF cathode and the hard carbon (HC) anode, effectively mitigating vanadium species dissolution and parasitic side reactions. Consequently, the 4.3 V NVPF||HC pouch cell can deliver exceptional cycling stability, retaining 85.24% of its capacity after 1500 cycles (416.7 days) at 0.3 C, and achieve a high energy density of 161 Wh kg- 1. This work establishes a design principle that couples orbital hybridization with steric shielding to construct ultra-stable interfaces in high-voltage battery systems.