Fabrication of composite positive electrode sheet with high active material content and effect of fabrication pressure for all-solid-state battery

The development of a fabrication process for sheet-type all-solid-state batteries with high energy density is critical for industrial applications. In this study, we systematically investigate the fabrication process of cells using composite positive electrode sheets with a high ratio of active materials. n-Decane was selected as a suitable solvent for the slurry because it has a sufficiently low vapor pressure and does not affect the ionic conductivity of solid electrolytes. In addition, the pre-densification of the composite positive electrode sheets was found to be effective in improving the cell performance. Suitable fabrication pressures were also determined. The cells fabricated under low-pressure conditions exhibited higher discharge capacities despite the higher internal resistance. Finally, our study revealed that the fracturing of LiNi1/3Co1/3Mn1/3O2 (NCM) occurs under high-pressure fabrication conditions because of the compression between the closely located NCM particles, resulting in the cleavage of the ionic and electronic conduction pathways.