Two-Layer Structured Cathodes for Solid State Batteries

Designing a robust cathode is one of the major objectives in R&D of lithium-ion batteries. The challenges only get amplified in case of solid state battery cells as the methods for introduction of electrolyte into the cathode structure need to be developed. Ideally, a cathode should support high energy density of a cell which implies necessity for high thickness. This requirement is not trivial to fulfil, both from the standpoint of manufacturing and from the standpoint of overcoming transport limitations in thick cathodes. In this work, inspired by the previous effort on graded porosity cathode design [1], we present a two-layer cathode based on LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622). The cathode is built using a densified “energy layer” as a support for the “power layer” in which high porosity and low tortuosity is achieved by the freeze tape casting technique. The distribution of the material in the two layers is guided by numerical simulations based on actual cathode microstructure. The performance of the structured cathodes containing Poly(ethylene oxide) (PEO) with lithium bis-trifluoromethanesulfonimide (LiTFSI) was experimentally investigated in cells containing metallic lithium counter electrode. The structured cathodes showed more than double capacity values and improved Coulombic efficiency compared to uniform cathodes of the same material loading. [1] Kalnaus, S., Livingston, K., Hawley, W.B., Wang, H., Li, J., 2021, “Design and processing for high performance Li ion battery electrodes with double-layer structure J Energy Storage 44 (2021) 103582. Acknowledgments: This research at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by Laboratory Directed Research and Development Program at ORNL.