Slurry gelation in high-nickel cathode electrodes: Rheology and oxalic acid-based suppression

초록

Slurry gelation during cathode fabrication remains a critical challenge in lithium-ion battery manufacturing because it deteriorates the processability, induces a non-uniform electrode morphology, and degrades the electrochemical performance. This phenomenon is primarily attributed to residual lithium compounds on cathode particle surfaces, which create alkaline conditions that accelerate poly(vinylidene fluoride) (PVdF) dehydrofluorination and subsequent crosslinking. In this study, Ni-rich layered oxide cathodes are employed as a model system to elucidate the underlying gelation mechanism and identify effective mitigation strategies. Oxalic acid, introduced as a mild acid additive, is shown to suppress slurry gelation by neutralizing residual lithium species and reducing the slurry alkalinity. Time-dependent rheological measurements and optical observations reveal that oxalic acid inhibits PVdF degradation, thereby delaying gel formation. Spectroscopic analyses further confirm that this stabilization arises from the suppression of PVdF dehydrofluorination through the neutralization of residual lithium species. Consequently, electrochemical testing shows that the addition of oxalic acid preserves both the capacity retention and rate capability. These findings establish oxalic acid as a practical and effective strategy for stabilizing high-Ni cathode slurries and improving electrode manufacturability.

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