Relationship between slurry dispersion and sheet structure in multi-component systems: a case study of cathodes for all-solid-state batteries

Abstract

Uniform dispersion in multi-component slurries is crucial for powder-based sheet fabrication but remains challenging, particularly in high-concentration systems. Existing evaluation methods may fail to adequately capture complex dispersion behaviors, limiting the design of stable, high-performance materials. This study investigated the relationship among particle dispersion, rheological properties, and the structural and electrical characteristics of cathode sheets for all-solid-state batteries, using particle concentration as a controlled variable. Slurries containing LiNi_0.8Mn_0.1Co_0.1O₂, Li₆.₂₅La₃Zr₂Al_0.25O₁₂, and acetylene black were prepared at concentrations of 30 to 45 vol%. Between 30 and 40 vol%, improved dispersion decreased the slurry’s relative viscosity ratio and increased the sheet packing fraction, resulting in lower sheet volume resistivity. However, at 45 vol%, the slurry exhibited the highest relative viscosity ratio—ordinarily interpreted as strong aggregation—and the highest sheet packing fraction, due to rapid network formation following effective dispersion. However, the sheet volume resistivity increased markedly, likely owing to excessive solid electrolyte dispersion disrupting the conductive network. These findings provide new insights and demonstrate that complementary methods are essential for accurately evaluating dispersion states in multi-component slurries. This knowledge can enhance the performance of sheet-formed bodies and optimize process control in multi-component slurry systems, such as those used in all-solid-state batteries.