Synergistic Crystallinity Reduction and Lewis Acidic Promotion by PVDF‐Al(OH) ₃ for High Room‐Temperature Ionic Conductivity in PEO‐Based Composite Quasi‐Solid Electrolytes

ABSTRACT

High‐energy‐density lithium metal batteries are of great interest as lithium‐ion batteries using graphite anodes are getting closer to their theoretical energy‐density limits. Poly(ethylene oxide) (PEO)‐based lithium metal batteries have the potential to achieve high energy density. However, their restricted electrochemically stable window, high operating temperature requirements, and low ionic conductivity in PEO limit their practical applicability. In this work, we combined polymer blending and organic‐inorganic composite modification to prepare a PEO/PVDF‐Al(OH) ₃ composite quasi‐solid electrolyte. PVDF is uniformly dispersed within PEO, effectively reducing PEO crystallinity, while the lewis acidity of Al(OH) ₃ promotes further dissociation of lithium salts. This enables PEO‐PNA3 to achieve an ionic conductivity of 2.72 × 10 ⁻⁴ S cm ⁻¹ at 20°C. More importantly, the presence of [NMP‐Li ⁺ ] coordination mechanism in the electrolyte ensures favorable contact between the electrode and electrolyte interface, thereby promoting Li ⁺ transfer at the interface. At room temperature (approximately 25°C), the assembled Li/PEO‐PNA3/Li symmetric battery demonstrated stable cycling for 900 h at a current density of 0.2 mA cm ⁻² , whilst the LFP/PEO‐PNA3/Li battery cycled over 120 times at 0.2C current density. This work provides an effective and scalable strategy for designing high‐performance PEO‐based composite quasi‐solid electrolyte, offering valuable insights for developing high‐energy‐density lithium metal batteries.