Metal organic framework optimized hybrid solid polymer electrolytes with a high lithium-ion transference number and excellent electrochemical stability

Abstract

Solid polymer electrolytes (SPEs) have proved to be good alternatives to liquid electrolytes. However, their application is severely restricted by low ionic conductivity and poor mechanical strength. Here, NH₂-MIL-125 metal–organic frameworks (MOFs) are selected as additives to optimize the poly (ethylene oxide) (PEO)-based SPEs. Compared with PEO-LiTFSI electrolyte (PE), the prepared PEO-LiTFSI-10% NH₂-MIL-125 MOF electrolyte (PEM10) not only enhanced the ionic conductivity (3.4 × 10⁻³ S cm⁻¹ at 80 °C), but improved the stability of the electrochemical window and lithium-ion transference number (t_Li⁺). The assembled Li/PEM10/LiFePO₄ battery exhibited a specific discharge capacity of 162 mA h g⁻¹ and superior rate capability of up to 1 C. The assembled Li/PEM10/Li battery showed a stable low-potential cycle for 600 hours at a current density of 0.1 mA cm⁻². These results demonstrate that such a novel electrolyte membrane with excellent performance could be considered as a promising MOF-based SPE for all-solid-state batteries.