Solid polymer electrolytes (SPEs)
of superior ionic conductivity,
long-term cycling stability, and good interface compatibility are
regarded as promising candidates to enable the practical applications
of solid lithium metal batteries (SLMBs). Here, a mixed-matrix SPE
(MMSE) with incorporated metal–organic frameworks (MOFs) and
ionic liquid is prepared. The dissociation of Li salt in MMSE can
be promoted effectively due to the introduction of MOF via the Fourier-transform infrared spectroscopy (FT-IR) analysis, density
functional theory calculation, and molecular dynamics simulation.
The as-formed MMSE exhibits an ultralow thickness of 20 μm with
a satisfactory ionic conductivity and lithium-ion transference number
(1.1 mS cm–1 at 30 °C, 0.72). The optimized
SLMBs with high-voltage LiMn0.75Fe0.25PO4 (LMFP) exhibit an excellent cyclability at 4.2 V under room
temperature. Moreover, Li/MMSE/LiFePO4 cells have desirable
cycle performance from −20 to 100 °C, and their capacity
remains 143.3 mA h g–1 after being cycled 300 times
at 10 C at 100 °C. The Li/LiFePO4 pouch cells also
show excellent safety under extreme conditions. The Li symmetric cells
can work steadily even at a supreme current density of 4 mA cm–2 at 100 °C. From the above analysis, these MMSEs
present new opportunities for the development of SLMBs with good electrochemical
properties.