<i>(Invited)</i> Dry-Process Processing Parameters for High-Energy Density Lithium-Ion Battery Electrodes

Dry-process electrode (DPE) manufacturing has emerged in the lithium-ion battery (LIB) space as a technology that enables the production of LIB electrodes through a series of powder-only techniques. This powder-only/dry-process production eliminates both the need for toxic solvents during slurry processing of electrodes and the need for energy- and time-intensive drying steps once electrodes have been coated onto a current collector. DPE manufacturing presents one of the few major opportunities in the past 25 years for both academic and industrial entities to realize a transformative change in lithium-ion chemistries, the raw materials that are in included in lithium-ion cells, how cells are manufactured, and how new cells/batteries come to market. Dry-process manufacturing can be a viable pathway to the development of thick LIB electrodes for high-capacity batteries used in electric vehicles, stationary storage, and electronics, among other applications. However, the technology readiness level (TRL) and manufacturing readiness level (MRL) of most entities fabricating DPEs is usually between 3-5, with only the most well-known players able to bring products containing dry-process electrodes to market. Additionally, tuning the manufacturing conditions to achieve optimal dry-process electrode loadings and microstructures that are free from defects is challenging. The lamination and calendering of the electrodes needs to be controlled to achieve uniform thickness, minimal or no secondary particle cracking, especially in the case for nickel manganese cobalt (NMC) materials, and favorable porosity and tortuosity that facilitates the application’s operating conditions while maximizing the cell’s cycle life. Navitas currently employs DPE fabrication at its Ann Arbor, MI facility using a 20mm twin-screw extruder (TSE) and has demonstrated thick cathodes and anodes between 5-10 mAh/cm 2 . The overall manufacturing readiness level of the process has been classified as a TRL/MRL 4 with Navitas having conducted formulation evaluations for active materials including lithium nickel manganese cobalt (NMC), lithium iron phosphate (LFP), sulfur-containing carbons, graphite, and silicon-graphite composites. The Navitas team has been able to explore several TSE screw parameters, TSE operating conditions, and calendering configurations that have enabled the production of high nickel (NMC811 and similar) dry-process cathodes that have reached over 500 cycles to 90% capacity retention in ~200mAh double-layer pouch cells and ~250 cycles (testing still on-going) in ~2Ah cells. The team will also discuss the considerations necessary for other electrode chemistries under manufacturing scale-up, such as graphite/silicon-graphite, and efforts being made to improve the manufacturability of sulfur-containing active materials in dry-process cathodes. Key words: solvent-free, dry-process, dry-process electrodes (DPEs), fibrillization, high nickel cathode, silicon-graphite anode, sulfur cathode, pouch cell, next generation lithium-ion batteries (NGLB), advanced dry-electrode process (ADEP)