Drying-Driven Microstructural Reorganization as a Key Origin of Rate Limitation in Multi-Walled Carbon Nanotube-Based Thick Electrodes for Lithium-Ion Batteries

초록

Thick LiFePO4 (LFP) cathodes are increasingly being explored as a practical approach to enhancing the cell-level energy density of lithium-ion batteries (LIBs) by increasing areal loading. Carbon nanotubes (CNTs) are widely used as conductive agents to improve electronic connectivity compared to conventional 0D carbon black (CB) electrodes; however, thick CNT-based electrodes often suffer from severe rate-performance loss. In this study, the correlation between microstructure and electrochemical performance is quantitatively analyzed by varying the electrode areal loading while maintaining a fixed slurry formulation. The results demonstrate that CNT agglomeration becomes more pronounced in thicker electrodes, creating structural bottlenecks that restrict both electronic and ionic transport pathways. It is shown that even with identical slurry preparation, the final electrode architecture can be strongly influenced by drying-driven microstructural reorganization, with agglomeration becoming more severe as the thickness increases. Furthermore, a modest modification to the drying protocol that reduces the evaporation rate mitigates agglomeration and improves both transport metrics and rate capability. This study highlights that the drying process, together with slurry dispersion, is a critical determinant of the final microstructure and performance of CNT-based thick electrodes.

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