Solid-State Composite Cathodes with Polymer Catholytes—fabrication, performance, and challenges

Abstract

Solid-state batteries represent a key technology for expediting the electrification of the economy. Several major classes of solid-state electrolytes are under development, including polymers, oxide ceramics, sulfides, and halides. One of the biggest roadblocks to the commercialization of solid-state batteries is their cathode. In a traditional lithium-ion battery cathode, the active particles are bound together by a binder and soaked in the liquid electrolyte. In a solid-state battery, charge transfer in and out of the cathode is challenged by the solid-solid interface between the solid electrolyte and the cathode active particles. These challenges include limited ion transport rates, lithium dendrite growth, and capacity fade when integrated with high-voltage cathodes such as LiNi_xMnyCo_1−x–yO₂. This presentation will discuss the manufacturing and capacity fade analysis of solid-state composite cathodes made with polymer catholytes. We demonstrate that solvent-free, melt-processing using twin screw extrusion is a scalable manufacturing method that produces dense (near-zero porosity) and thick cathodes with high active material loadings (80 wt%). The microstructure of the melt-processed composite cathode exhibits several differences compared to that of traditional slurry-cast cathodes. Due to these microstructural differences, the melt-processed cathode mitigates lithium anode instability in polymer-based SSBs. In addition to cathode manufacturing, the capacity fade of polymer-based SSBs will also be discussed. We quantify the sources of capacity fade (ion transport limitation vs. interface instability) in composite cathodes made with a series of polymeric catholytes. The improved understanding of polymer-based cathodes will contribute to the optimized integration of solid cathodes into SSBs.

Biography

Chelsea Chen, Senior R&D Staff at Oak Ridge National Laboratory (ORNL), has extensive experience in polymers, composites, interfaces, electron microscopy and neutron/X-ray scattering. She leads programs in solid state batteries and polymer/composite electrolytes at ORNL. She earned her PhD in 2011 from the University of Michigan, Ann Arbor and pursued postdoctoral research at Lawrence Berkeley National Laboratory. Chen worked as a senior chemist at Dow Electronic Materials before joining ORNL in 2017. She has over 70 peer-reviewed publications and 3 issued patents. She received the 2022 American Chemical Society PMSE Division’s Young Investigator Award.