Metal-organic framework (MIL-101Fe) - incorporated composite polymer electrolytes for all solid-state lithium-ion batteries

Solid polymer electrolyte emerges as an attractive candidate for all solid-state lithium batteries (ASSLBs). Nevertheless, the drawbacks of low ionic conductivity and poor mechanical property hinder the commercial application. Herein, the metal-organic framework (MOFs) is introduced into polyethylene oxide (PEO) to produce composite polymer electrolytes (CPEs) for ASSLBs. It is disclosed that the MIL-101(Fe) with porous structure effectively lowers glass transition temperature, and restricts the migration of anions of PEO, resulting in high Li⁺ transference number (0.47) and the significantly improved ionic conductivities of 4.78 × 10⁻³ S cm⁻¹ at 80 °C. Moreover, the CPE with 10 wt% MIL-101(Fe) exhibits a widened electrochemical stability window (5.25 V), enhanced thermal stability to 380 °C and improved tensile strength of 0.62 MPa. The solid-state LiFePO₄|10 wt% MOF/PEO|Li battery delivers an improved discharge capacity of 16a5.49 mAh g⁻¹ at 0.1C and 50 °C with a capacity retention of 87.9 % after 80 cycles. After cycling at a high current of 0.5C and 50 °C for 80 cycles, the battery delivers a capacity retention of 93.8 %. These results demonstrate that MIL-101(Fe) - incorporated PEO is a promising solid electrolyte for safe and long-life batteries.