Transport characterization of solid-state Li2FeS2 cathodes from a porous electrode theory perspective

The abundance and cost of resources for current state-of-the-art cathode active materials makes the search for alternative cell chemistries inevitable. Nonetheless, especially in solid-state batteries, establishing new cell chemistries comes at the challenge of optimizing the transport of both charge carriers, electrons and ions, through the electrode. Limitations in transport of either species lead to underutilization of the electrode caused by insufficiently contacted particles and/or nonuniform reaction rates and state-of-charge gradients through the electrode. In this work, we investigate the capabilities of Li2FeS2 as alternative active material in all-solid-state cathodes by thorough investigation of the initial utilization and rate capability as a function of the cathode loading. The cathode loading is increased from 1.8 to 7.3 mAh·cm−2 by increasing the fraction of active material from 32 to 74 vol.%, and the thickness of the composite electrode from 73 to 145 μm. Careful characterization of the effective electronic and ionic transport, and consideration of the δ-parameter from porous electrode theory, guides the understanding of the electrode performances. With that, this work shows that Li2FeS2 solid-state cathodes with high areal loadings and gravimetric energy densities can be realized.