Quantitative analysis of electronic and ionic conductivity trade-offs in all-solid-state battery cathodes with CNT conductive additives

While sulfide-based all-solid-state batteries (ASSBs) are considered a promising next-generation energy storage solution for the growing electric vehicle market, their commercialization remains hampered by limitations in composite cathode performance, primarily due to insufficient electronic and ionic percolation. To facilitate the electronic percolation, one-dimensional conductive agents (CAs) have been proposed to establish a more effective electronic network within the electrodes. However, the specific effects of carbon additives on electronic and ionic conductivities within cathodes remain insufficiently understood due to the experimental challenges associated with deconvoluting overpotentials. Herein, we systematically investigate the influence of CA dimension and surface characteristics on rate capability. A physics-based pseudo-two-dimensional model was developed to deconvolute overpotentials, revealing that excess carbon nanotubes lead to high ionic overpotentials despite reduced electronic resistance. These findings highlight the importance of balancing electronic and ionic conductivities, providing guidance for optimizing cathode design and high performance ASSBs.