Metal-Organic Framework Glass as a Functional Filler Enables Enhanced Performance of Solid-State Polymer Electrolytes for Lithium Metal Batteries

JW Ding and T Du and EH Thomsen and D Andresen and MR Fischer and AK Moller and AR Petersen and AK Pedersen and LR Jensen and SW Wang and MM Smedskjaer, ADVANCED SCIENCE (2023).

DOI: 10.1002/advs.202306698

Polymers are promising candidates as solid-state electrolytes due to their performance and processability, but fillers play a critical role in adjusting the polymer network structure and electrochemical, thermal, and mechanical properties. Most fillers studied so far are anisotropic, limiting the possibility of homogeneous ion transport. Here, applying metal-organic framework (MOF) glass as an isotropic functional filler, solid-state polyethylene oxide (PEO) electrolytes are prepared. Calorimetric and diffusion kinetics tests show that the MOF glass addition reduces the glass transition temperature of the polymer phase, improving the mobility of the polymer chains, and thereby facilitating lithium (Li) ion transport. By also incorporating the lithium salt and ionic liquid (IL), Li-Li symmetric cell tests of the PEO-lithium salt- MOF glass-IL electrolyte reveal low overpotential, indicating low interfacial impedance. Simulations show that the isotropic structure of the MOF glass facilitates the wettability of the IL by enhancing interfacial interactions, leading to a less confined IL structure that promotes Li-ion mobility. Finally, the obtained electrolyte is used to construct Li-lithium iron phosphate full batteries that feature high cycle stability and rate capability. This work therefore demonstrates how an isotropic functional filler can be used to enhance the electrochemical performance of solid-state polymer electrolytes. A metal-organic framework (MOF) glass is used as a functional filler to construct solid-state polymer electrolytes. Experiments and simulations demonstrate the advantages of the isotropic and grain boundary-free structure of the MOF glass, facilitating wettability and in turn enhanced interfacial interaction. The advanced glassy MOF can then be used to make high-performance lithium metal batteries.image

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