Data‐Driven Ionization‐Energy Descriptor Enables Stable Cathode‐Electrolyte Interface in All‐Solid‐State Sodium‐Metal Batteries

ABSTRACT All‐solid‐state sodium‐metal batteries (ASSSMBs) hold great promise for large‐scale energy storage owing to their intrinsic safety, low cost, and high energy density, yet their practical deployment is hindered by poor cathode‐electrolyte contact and unstable interphases. Herein, we propose a descriptor‐guided strategy that integrates the minimum average local ionization energy (ALIEmin) with cation binding energy as dual screening criteria to establish a predictive solvent screening framework that enables high‐voltage tolerance (high ALIEmin) while promoting weak solvation (low binding energy), thereby enhancing anion participation during interphase formation. Guided by this framework, succinonitrile (SN) was identified as the optimal solvent, uniquely combining a high ALIEmin with a low Na + binding energy, thereby enabling both oxidative robustness and weak solvation. When SN‐based electrolytes serve as the interlayer in the NVP@NZSP||NZSP||Na cell, they drive the in situ formation of a uniform thin‐layer cathode‐electrolyte interface (CEI) rich in sodium fluoride. As a result, the optimized ASSSMB achieves long‐term cycling stability (97.7% capacity retention after 10,700 h at 0.1C) and high‐rate durability (94.5% after 2,100 cycles at 1C), outperforming previously reported NASICON‐based systems. This study positions physically interpretable molecular descriptors as a versatile approach for rational interphase design, advancing the development of stable interfaces in next‐generation solid‐state batteries.