Preparation of poly(ionic liquid) composite quasi-solid electrolyte by incorporating metal − organic framework filler decorated with ionic liquid for lithium batteries

Poly(ionic liquids) (PILs) electrolytes combine the advantages of ionic liquids and polymers and have been widely studied to boost the performance of lithium batteries . However, one main problem that most of PILs electrolytes encounter is the tradeoff between mechanical integrity and high ionic conductivity . Therefore, elevating ionic conductivity is still a problem to be solved urgently. In this work, ether group-functionalized PIL is synthesized and an ionic liquid (IL) decorated metal−organic framework (MOF) filler IL@UIO-66 is prepared. Subsequently, one composite polymer electrolytes (MCPEs) involving IL@UIO-66 and PIL are built via solution-casting approach. The as-prepared optimal MCPE membranes with 10% IL@UIO-66 (MCPE-10%) express higher ionic conductivity as high as 2.06 × 10 −4  S cm −1 and larger lithium ion transference number of 0.49 at 30 °C than the electrolytes without filler (CPE). Comparing with CPE, the thermal stability of MCPE-10% is significantly improved to 300 °C by IL@UIO-66 and the electrochemical stability of MCPE-10% with an oxidation potential of 5.10 V vs. Li + /Li is almost unaffected. Besides, the interfacial stability between MCPE-10% and lithium electrode is improved. The assembled LiFePO 4 /MCPE-10%/Li cells show a promising rate and cycle performance at 25 °C. They show an initial discharge capacity of 123 mAh g −1 at current density of 0.5C, and their discharge capacity retention is up to 95% after 100 cycles with coulombic efficiency higher than 99%.