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

Abstract

To 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 52% and 46% after 1,000 cycles, respectively.