Enhancing the Interfacial Stability of Thin Solid Polymer Electrolyte with Fluorinated Covalent Organic Framework Nanosheets.

Liu, Tao; Zhong, Yuan; Gao, Xiangyu; Jiang, Jun; Jiang, Lingyi; He, Boying; Liu, Yichen; Ling, Zhiyi et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Thin poly(ethylene oxide) (PEO)-based electrolytes with higher energy density face challenges such as low ionic conductivity, deterioration of lithium dendrites, and severe side reactions. To address these issues, a surface modification strategy was developed to enhance the electrode-electrolyte interfacial stability by introducing fluorinated covalent organic framework nanosheets (CONs) to construct a thin PEO-based electrolyte with a mere 14 μm thickness. Characterization and DFT calculation indicated that the CON layer promotes concentration enrichment and averaging of free Li<sup>+</sup> and mitigates side reactions at the interface. The electrode/electrolyte interface stability is significantly improved compared to the unmodified group (Li symmetric cells stabilized for more than 1000 h, and the full cell of LiFePO<sub>4</sub>∥Li exhibited a satisfactory capacity retention of 97.3% at 0.5 C after 150 cycles at 60 °C. This interface modification strategy provides a valuable reference for applying thin polymer electrolytes in high-energy solid-state lithium metal batteries.