Direct Casted LLZO-LITFSI Composite Solid-State Electrolyte for Lithium Ion Batteries

Abstract

All-solid-state batteries (ASSBs) based on solid state electrolytes (SSE) has a promising future for safer lithium ion batteries (LIB) with high energy density. However, it has been challenging in large-scale fabricating an SSE separator with transport properties and comparable thickness to a traditional polypropylene separator used in lithium-ion batteries. This problem is especially exaggerated with oxide-based solid electrolytes, such as Li7-3xAlxLa3Zr2O12 (LLZO), where thin films with micrometer scale in thickness using scalable techniques have not been realized.LLZO SSE separator is commonly made by fabricating pellet and followed by sintering. The resulting film must be thick enough to provide reasonable mechanical strength. However, the thick SSE separator will cause high resistance and low energy density. Here we present a direct casting technique to coat ultrathin LLZO-LITFSI composite electrolyte on the LiFePO4 cathode. Through this technique, the electrolyte layers with different thickness ranging from 50 to 150 µm were prepared and studied electrochemically in ASSB using lithium as the anode. Without any further process and treatment, the ASSBs show a stable cycling performance with a reversible capacity >150 mA h/g (~90% of the theoretical value). This work provides a potential scale-up strategy to manufacture stable and ultrathin garnet-based SSE for all-solid-state batteries.AcknowledgementWe gratefully acknowledge the support from the U.S. Department of Energy's Vehicle Technologies Office. This work is conducted under the Cell Analysis, Modeling, and Prototyping (CAMP) Facility at Argonne National Laboratory. Argonne National Laboratory is operated for DOE office of Science by UChicago Argonne, LLC, under contract number DE-AC02-06CH11357.