An investigation of two dry processes: Fibrillation and electrostatic spray deposition for making high loading electrodes

Lithium-ion batteries (LIBs) are crucial for sustainable energy storage, especially for electric vehicles. Traditional slurry-casting methods face challenges such as uneven distribution of binders, which can negatively affect mechanical properties and electrochemical performance. In contrast, dry electrode manufacturing (DEM) can ensure uniform binder distribution and reduce manufacturing costs. Moreover, DEM can significantly reduce environmental impact by eliminating the use of solvents. This study compares two DEM approaches: “dry fibril” based on the fibrillation of polytetrafluoroethylene (PTFE) and electrostatic spray deposition (ESD) using PVDF as a binder for making high-loading LiNi₀.₉₀₆Co₀.₀₅Mn₀.₃₄Al₀.₀₁O₂ (NCMA) positive electrodes.The structural, mechanical, and electrochemical behavior of electrodes with a composition of 95:3:2 (NCMA: carbon black: binder), a loading of 6.00 mAh cm−2, and 35% porosity were examined using scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), microindentation, and X-ray photoelectron spectroscopy (XPS). SEM/EDS revealed that the dry fibril process produces a more interconnected microstructure. AFM and microindentation confirmed enhanced mechanical cohesion and improved electronic contact due to the entrapment of carbon black within the PTFE fibril network. Raman spectroscopy indicated differences in carbon distribution between the two electrodes. XPS showed differences in SEI composition between the two electrodes, suggesting varied interfacial chemistries. Electrochemical testing demonstrated that the dry fibril electrode outperforms the dry ESD electrode in long-term cycling, supporting the structural and transport advantages offered by the fibril-based architecture. This study provides a better understanding of the two dry processes for making high-loading electrodes.