Composite polymer electrolytes with uniform distribution of ionic liquid-grafted ZIF-90 nanofillers for high-performance solid-state Li batteries

作者：Lei, Zhiwen; Shen, Jinlai; Wang, Jun; Qiu, Qi; Zhang, Guangzhao; Chi, Shang-Sen; Xu, Hongli; Li, Shuai; Zhang, Weide; Zhao, Yusheng; Deng, Yonghong^*; Wang, Chaoyang^*

来源：Chemical Engineering Journal, 2021, 412: 128733.

DOI：10.1016/j.cej.2021.128733

• Metal organic frameworks
• Zeolitic imidazolate framework
• Ionic liquid
• Poly (ethyleneoxide)
• Solid polymer electrolyte

The stable structure, high porosity and surface functionality endow metal organic frameworks (MOFs) nanoparticles as excellent nanofillers for high-performance poly (ethyleneoxide)-based solid polymer electrolytes (PEO SPEs). However, the agglomeration of MOFs severely limits their potential applications. Herein, a novel zeolitic imidazolate framework-90 nanofiller grafted with imidazole ionic liquid containing siloxane groups (ZIF90-g-IL) is prepared by dehydration condensation reaction, which enables the uniform distribution of the nanofiller in PEO SPEs. The resulting composite PEO SPE with ZIF-90-g-IL nanofillers delivers higher ionic conductivity of 1.17 x 10-4 S/cm at 30 ?C and lithium ion transference number of 0.44, wider electrochemical stability window of 4.8 V, and stronger ability to inhibit lithium dendrite growth than the PEO SPE with unmodified ZIF-90. The strong interaction of ZIF-90-g-IL with PEO is caused by the chelation of quaternary ammonium cations of ionic liquid groups on the ZIF-90-g-IL surface with oxygen containing a lone pair of electrons of PEO, resulting in a uniform distribution of the nanofillers in PEO. The LFP||Li half cells with the PEO/ZIF-90-g-IL SPE exhibit good cycling performance with 71% capacity retention (101 mAh g-1) after 500 cycles at 2C under 60 ?C, and show excellent cycling performance with 97.4% capacity retention (148 mAh g-1) after 30 cycles at 0.1C under 30 ?C. The composite SPE is also used for high-voltage NCM811||Li half cells. The capacity retention is 63% (99 mAh g-1) after 100 cycles at 0.1C under 60 ?C. The results imply ZIF-90-g-IL as effective nanofillers for SPEs showing a great potential application in all solid-state lithium metal batteries.