Anion-Complementary Soft Solvation Electrolytes Stabilizing Dual Interfaces for High-Voltage Lithium Metal Batteries across Wide Temperatures Article Swipe
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· 2025
· Open Access
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· DOI: https://doi.org/10.1021/acsami.5c07417
· OA: W4414335978
Lithium metal batteries (LMBs) face severe interfacial degradation due to uncontrolled lithium dendrite growth and electrolyte decomposition. Conventional electrolytes fail to concurrently stabilize lithium metal anodes and high-voltage cathodes owing to competing parasitic reactions. Here, we report a softly solvating electrolyte composed of 1,3-dioxane (1,3-DX) and dual salts─lithium bis(fluorosulfonyl)imide/lithium hexafluorophosphate (LiFSI/LiPF<sub>6</sub>)─that leverages anion-complementary coordination to decouple interfacial requirements. The solvent's steric hindrance softens Li<sup>+</sup>-solvent interactions, enabling FSI<sup>-</sup> and PF<sub>6</sub><sup>-</sup> to spatially separate their interfacial functions: FSI<sup>-</sup> drives LiF-rich solid-electrolyte interphase (SEI) formation on Li metal, while PF<sub>6</sub><sup>-</sup> constructs a thin (<10 nm) cathode-electrolyte interphase (CEI) on LiNi<sub>0.5</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub>O<sub>2</sub> (NCM523) cathodes. Raman and <sup>17</sup>O NMR spectra confirm suppressed solvent coordination and anion-aggregate dominance. Li||NCM523 cells utilizing this electrolyte achieve over 80% capacity retention after 100 cycles at 4.3 V, with a high average Coulombic efficiency (CE) above 99.0%. Cross-sectional scanning electron microscopy/transmission electron microscopy (SEM/TEM) reveals crack-free cathodes and robust, homogeneous SEI and CEI layers. Remarkably, the Li||NCM523 cells maintain 36.9% capacity retention of their room-temperature performance (54.7 vs 148.3 mAh g<sup>-1</sup>) at 0.2 C and -30 °C, highlighting the electrolyte's low-temperature compatibility. This work establishes an anion-synergistic design strategy to reconcile bulk ion transport with dual electrodes.
