HKUST-1@IL-Li Solid-state Electrolyte with 3D Ionic Channels and Enhanced Fast Li+ Transport for Lithium Metal Batteries at High Temperature

Abstract

The challenge of safety problems in lithium batteries caused by conventional electrolytes at high temperatures is addressed in this study. A novel solid electrolyte (HKUST-1@IL-Li) was fabricated by immobilizing ionic liquid ([EMIM][TFSI]) in the nanopores of a HKUST-1 metal–organic framework. 3D angstrom-level ionic channels of the metal–organic framework (MOF) host were used to restrict electrolyte anions and acted as “highways” for fast Li+ transport. In addition, lower interfacial resistance between HKUST-1@IL-Li and electrodes was achieved by a wetted contact through open tunnels at the atomic scale. Excellent high thermal stability up to 300 °C and electrochemical properties are observed, including ionic conductivities and Li+ transference numbers of 0.68 × 10-4 S·cm-1 and 0.46, respectively, at 25 °C, and 6.85 × 10-4 S·cm-1 and 0.68, respectively, at 100 °C. A stable Li metal plating/stripping process was observed at 100 °C, suggesting an effectively suppressed growth of Li dendrites. The as-fabricated LiFePO4/HKUST-1@IL-Li/Li solid-state battery exhibits remarkable performance at high temperature with an initial discharge capacity of 144 mAh g-1 at 0.5 C and a high capacity retention of 92% after 100 cycles. Thus, the solid electrolyte in this study demonstrates promising applicability in lithium metal batteries with high performance under extreme thermal environmental conditions.

Ionic Liquid@Metal-Organic Framework as a Solid Electrolyte in a Lithium-Ion Battery: Current Performance and Perspective at Molecular Level

“…Li et al utilized a Li-[EMIM][TFSI]@HKUST-1 SSE for the development of fast lithium ion transport in LIBs at elevated temperatures [ 97 ]. This SSE has a high thermal stability (up to 300 °C) with a relatively good ionic conductivity and Li + transference number of 0.68 × 10 −4 S cm −1 and 0.46 at 25 °C, respectively.…”

Metal–organic framework-based solid-state electrolytes for all solid-state lithium metal batteries: a review

“…Based on the above studies, it can be concluded that the pore size of MOFs is one of the key factors in the encapsulation of ILs. The pore diameters of the MOFs mentioned above are as follows: UIO-67, tetrahedral and octahedral cages with diameters of 12 Å and 16 Å; UIO-66, tetrahedral and octahedral cages with diameters of 7.5 Å and 12 Å; HKUST-1, 74 pore diameter of about 8 Å; MOF-525(Cu), an aperture size of 12 × 7 Å, while the size of the cation and anion in the ionic liquid is [EMIM] + (7.6 × 4.3 Å) and [TFSI] − (7.9 × 2.9 Å). Obviously, UIO-67 has the largest pore size, thus the restriction effect on the IL is not obvious and has the lowest ion migration number.…”

Exploring ionic liquid-laden metal-organic framework composite materials as hybrid electrolytes in metal (ion) batteries

“…In the first cycle, a high irreversible capacity is observed, which is related to the formation of the solid electrolyte interface (SEI), but from the second cycle on, the capacity is practically constant, providing a reversible discharge capacity of 3,000 mAh g −1 at 0.1C. Cu (HKUST-1) ( Dutta and Kumar, 2019 ; Li et al, 2021 ), Cr (MIL-101) ( Xu et al, 2019 ) and Al (MIL-121) based MOFs ( Zettl and Hanzu, 2021 ) have also been studied as ionic conductors.…”