Dynamic pore-network evolution in mesoporous CMK3@S cathodes governing sulfur conversion and electrochemical accessibility

Abstract Mesoporous carbon architectures provide high surface accessibility and interconnected transport pathways for sulfur-based energy-storage materials. However, the initial pore structure may evolve during electrochemical operation due to solid-product formation, affecting ionic transport and sulfur utilization. In this study, the dynamic structure–transport–performance relationships governing sulfur conversion in mesoporous CMK3@S cathodes for potassium–sulfur batteries are investigated using a coupled porous-electrode model. The model framework describes the coupled evolution of K⁺ transport, polysulfide redistribution, sulfur-conversion kinetics, K₂S precipitation, connected porosity, tortuosity, interfacial accessibility, and spatial reaction redistribution. The model predictions were quantitatively evaluated against reported electrochemical characteristics and independently measured transport-related properties, showing deviations within an acceptable range for electrode-scale simulations. The validated framework predicts a nonlinear transition from distributed K₂S accommodation to connectivity-sensitive pore-network obstruction during discharge. According to the simulations, moderate precipitation can be accommodated by the mesoporous framework with limited transport penalty, whereas deposition near critical transport pathways results in accelerated loss of ionic accessibility. At the simulated advanced-discharge condition, the predicted mean precipitation-blocking index (PBI) reaches 0.69, accompanied by a transport-limitation index (TLI) of 0.74, a reaction uniformity index (RUI) of 0.49, an active-depth utilization (ADU) of 58.7%, and an accessible-capacity loss (ACL) of 28.7%. Sensitivity and uncertainty analyses based on the model further identify precipitation kinetics, initial pore accessibility, tortuosity, and ionic diffusivity as key parameters controlling structural–electrochemical evolution. These results suggest that maintaining connected transport pathways during solid-product formation is critical for improving the electrochemical accessibility of mesoporous sulfur cathodes and provide a mechanistic modeling perspective for the design of precipitation-tolerant carbon–sulfur electrode architectures.