Efficient, Scalable Manufacturing of Solid-State Lithium Battery Cathodes Enabled by Radical Induced Cationic Frontal Polymerization

When incorporated into solid-state cathodes, polymer electrolytes (a.k.a. catholytes) accommodate volume expansion and provide low resistance interfaces required for high current densities (high power). Current manufacturing techniques employ large volumes of organic solvent in catholyte processing, however, requiring significant energy usage (over 40 percent of the total energy in electrode manufacturing), and leading to high manufacturing costs. This award supports research to study a novel manufacturing approach based on additive UV photopolymerization, which is solvent-free, eliminating the use of toxic organic solvents and lowering energy requirements by three orders of magnitude. This technology will establish the foundation for domestic manufacturing of next-generation solid-state battery cathodes, which is cost competitive due to the dramatically reduced solvent and energy usage, while also being safer for the environment and human health. It is expected to be a “drop-in” technology that can be implemented in existing electrode manufacturing facilities with relatively minor modifications – critical to the rapidly growing market for solid-state batteries where annual growth is forecasted to surpass 110 percent over the next decade. Beyond these technological advances, the award also provides education and fundamental research opportunities to support STEM outreach in the local Rochester, New York region.   The high-throughput manufacturing process is based upon radical-induced cationic frontal polymerization (RICFP). RICFP combines highly active thermal initiators with onium salt cationic photoinitiators to achieve photopolymerization over large length scales in filled composite materials. The exotherm of cationic chain propagation drives thermolysis of the thermal initiator, resulting in a thermal front that extends from the incident irradiation. RICFP overcomes two practical limitations in conventional UV and e-beam curing of lithium-ion battery electrodes – O2 inhibition, which requires a costly N2 purge to mitigate, and the scattering of incident UV radiation, which limits cure depths. To extend RICFP processing to solid state battery cathodes, high performance polymer catholyte materials amenable to RICFP will be developed. Specifically, copolymers of substituted epoxides and oxetanes will be prepared, extending RICFP to relatively underexplored linear copolymer compositions. Processing capabilities will be established for in situ fabrication of polymer catholytes within practical composite solid-state cathodes. Synthesis-structure-property relationships will be characterized experimentally to elucidate how the electrolyte formulations and processing conditions dictate critical electrochemical properties. After these materials discovery and process development efforts, scalable continuous manufacturing of solid-state cathodes via RICFP will be demonstrated, and the cathodes will be assembled into solid state lithium metal batteries to validate their energy storage performance against state-of-the-art cathodes prepared through conventional slurry coating. The material chemistry and processing knowledge will lead to high performance solid-state polymer catholytes that can be incorporated into lithium battery cathodes at scale via an industrially relevant manufacturing process. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2548367 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Wyatt Tenhaeff | Institution: University of Rochester, ROCHESTER, NY | Award Amount: $299,943 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2548367 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2548367.html