Influence of Iron‐Based Metal–Organic Frameworks With Different Ligands on the Performance of Poly(Ethylene Oxide) Composite Solid Electrolyte

ABSTRACT Poly(ethylene oxide) (PEO)‐based solid electrolytes have attracted widespread attention due to their excellent electrochemical stability and remarkable solubility for lithium salts. However, the relatively low ionic conductivity of PEO‐based solid‐state batteries at room temperature causing insufficient capacity seriously hinders their commercial application. Herein, a new composite solid electrolyte is explored using metal–organic frameworks (MOFs), named as NH ₂ ‐MIL‐88, to incorporate in PEO. The metal centers in MOFs can effectively anchor TFSI ⁻ through strong Lewis acid–base interactions, and combined with the hydrogen bonding between the NH ₂ in NH ₂ ‐MIL‐88 and TFSI ⁻ , this dual mechanism synergistically promotes the dissociation of lithium salt, leading to a higher concentration of free Li ⁺ . Consequently, the ionic conductivity of the 5 wt.% NH ₂ ‐MIL‐88|PEO|LiTFSI (5‐NPL) composite solid electrolyte reaches 1.64 × 10 ⁻⁴ S cm ⁻¹ at 60°C. The electrochemical windows reaches 5.18 V. Moreover, at a rate of 0.2 C, the first‐cycle discharge specific capacity of Li//5‐NPL//LFP reaches 163.3 mAh g ⁻¹ , demonstrating the considerable research potential and promising commercial prospects.