Converting a Commercial Separator into a Thin‐film Multi‐Layer Hybrid Solid Electrolyte for Li Metal Batteries

Abstract

AbstractTo address the manifold challenges solid electrolytes (SE) do face in NMC‖Lithium metal batteries, we demonstrate that these can be overcome by converting a commercial Celgard 2500 separator into a jack of all trades hybrid solid electrolyte (HSE). This approach follows a multi‐layer electrolyte strategy, to better cope with the very different chemistries of the cathode, the bulk electrolyte material, and the Li metal anode. A cathode‐facing electrolyte layer based on lithium aluminum titanium phosphate (LATP) provides a high voltage stability of ≥4.5 V. High mechanical strength of the overall thin film electrolyte (≤50 μm) is achieved with a middle layer based on Celgard 2500. The layer on the anode side, based on polyethylene oxide (PEO), allows stable cycling of the lithium metal. High Coulombic efficiencies in NMC622‖Li metal cells (99.9 %) and LFP‖Li metal cells (99.9 %) enable long term cycling with high‐capacity retention of 46 % and 52 % after 1,000 cycles, respectively.