(Invited) An Investigation of Electrodes Made Using Two Dry Processes: Fibrillation and Electrostatic Spray Deposition

Lithium-ion batteries (LIBs) are crucial for sustainable energy storage, especially in electric vehicles. Traditional slurry-casting methods encounter challenges such as uneven distribution of binders and carbon additives, which can negatively affect mechanical properties and electrochemical performance. In contrast, dry electrode processing presents a promising alternative by ensuring uniform binder distribution and reducing manufacturing costs. Furthermore, using a dry process, producing large-scale LIB electrodes can significantly reduce environmental impact, eliminating the need for solvents. This study compares two dry fabrication methods: Dry fibril using the fibrillation behavior of polytetrafluoroethylene (PTFE) binder and electrostatic spray deposition (ESD) using PVDF as a binder to examine their impact on the production of high-loading Lithium Nickel Cobalt Aluminum Oxide (NCMA) positive electrodes. We investigated electrodes of the composition 95:3:2 (NCMA: CB: binder), corresponding to CB/binder mass ratios of 1.5:1. The final electrode loading was set at 6.00 mAh/cm 2 and porosity at 35 ± 1%. The surface and cross-section morphologies of the electrodes were characterized using a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The electrode film was further examined using atomic force microscopy (AFM) and nanoindentation, providing a detailed understanding of their electronic and mechanical properties. The electrochemical performance of the electrodes was evaluated in a half-cell configuration. Dry fibril electrodes show a more uniform and highly conductive electronic network because the PTFE fibrils effectively entrap carbon black (CB) particles. Ionic and electronic resistance measurements revealed that the dry fibril process significantly reduces electronic resistance, leading to enhanced electronic conductivity. Moreover, these electrodes exhibit greater mechanical flexibility, characterized by a lower elastic modulus and hardness compared to dry ESD electrodes. Their flexibility makes dry fibril electrodes better suited for withstanding mechanical deformation in LIBs. The SEM/ESD and AFM studies showed that dry fibril electrodes have a more interconnected structure due to PTFE’s fibrillation, while ESD electrodes tend to exhibit smoother but less conductive surfaces. This study provides a better understanding of the two dry processes used to manufacture high-loading electrodes.