Difunctional NH2-modified MOF supporting plentiful ion channels and stable LiF-rich SEI construction via organocatalysis for all-solid-state lithium metal batteries

Abstract

As an essential part of the performance improvement of lithium metal batteries, the acquisition of dense (LiF-rich solid electrolyte interphase (SEI)) has always been an urgent problem to be solved. Herein, we synthesized Zeolitic Imidazolate Frameworks (ZIFs) modified by two different functional groups (–NH2, –CH3) and used them as the fillers of polyethylene oxide (PEO) composite solid electrolytes to explore the catalytic effect of groups on LiF generation at the Li/electrolytes interface. In a LiFePO4||SPE||Li cell test, the PEO-ZIF-NH2 with LiF-rich SEI exhibits enhanced cycling performance, which was 3.8 times longer than that of PEO-ZIF-CH3. The formation mechanism of LiF-rich SEI was investigated using first-principles calculation, revealing that ZIFs-NH2 makes the C–F bond in TFSI– longer compared with ZIFs-CH3, which leads to easier breakage of the C–F bond and promoted the formation of LiF. The simple design idea of using organic catalysis to generate more stable SEI provides a new aspect for preparing high-performance lithium metal batteries.