Dimensionality Control of Li Transport by MOFs Based Quasi-Solid to Solid Electrolyte (Q-SSEs) for Li−Metal Batteries

Nowadays, lithium-ion batteries (LIBs) are widely used in all walks of life and play a very important role. As complex systems composed of multiple materials with diverse chemical compositions, where different electrochemical reactions take place, battery interfaces are essential for determining the operation, performance, durability and safety of the battery. This work, set out to study the incorporation of lithium bis(fluorosulfonyl)amide (LiFSI) doped 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][TFSI]) ionic liquid into an archetype Ti-based Metal Organic Framework (MOF) ((Ti) MIL125−NH₂) to create a solid to quasi-solid (depending on the amount of IL in the system), and how it affects not only ionic transport but also the structural properties of the IL/MOF electrolyte. Remarkably high ionic conductivity values (2.13×10⁻³ S ⋅ cm⁻¹ at room temperature) as well as a lithium transference number (t_Li=0.58) were achieved, supported by pulsed field gradient (PFG) NMR experiments. Electrochemical characterization revealed reversible plating-stripping of lithium and lower overpotential after 750 h at 50 °C. Additionally, a proof-of-concept solid state battery was fabricated resulting in a discharge capacity of 160 mAh ⋅ g⁻¹ at 50 °C and 0.1 C rate after 50 cycles. This work presents a suitable strategy to dendrite suppression capability, allowing its implementation as interface modifiers in next-generation solid-state batteries.