Disrupting the crack-delithiation feedback loop in dry-processed high-nickel cathodes through early-stage granule engineering

초록

Solvent-free dry electrode processing with polytetrafluoroethylene (PTFE) fibrillation offers a cleaner, scalable route to lithium-ion battery manufacturing, but the high mechanical pressure required for fibrillation fractures cathode active material (CAM) particles during fabrication, and the resulting defects drive non-uniform Li+ extraction in a self-reinforcing damage cascade. An early granulation step disrupts this cascade at its origin. In the pre-granulation process (PGP), a PTFE fibril network forms inside cohesive LiNi0.8Co0.15Al0.05O2 (NCA) granules; during kneading and calendering, the fibril-bridged granules deform controllably, absorbing and redistributing applied stress so that individual secondary particles are protected. The resulting granule-induced dry electrode (GIDE) inherits a uniform microstructure that supports spatially homogeneous Li+ extraction. Density functional theory and molecular dynamics suggest that this homogeneity preserves lattice ductility and reduces internal von Mises stress, which is expected to suppress the local stress concentrations that nucleate cracks. Electron microscopy before and after cycling, with electrochemical analysis, validates the mechanism. GIDE delivers a 77% lower charge-transfer resistance, 230% greater toughness, and 86% capacity retention after 100 half-cell cycles at 0.5C and 10 mAh cm−2 loading, whereas the conventional dry electrode (CDE) fails at 60 cycles. NCA||graphite full cells retain 86.1% capacity over 300 cycles. The granule-mediated strategy breaks the self-reinforcing degradation cycle and provides a scalable route to robust dry-processed cathodes.

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