Warm Isostatic vs. Cold Uniaxial Pressing in All-Solid-State Battery Cathodes: Linking Microstructure, Transport, and Mechano-Electrochemical Response

Lithium-based all-solid-state batteries (ASSBs) are attracting increasing attention as nextgeneration energy storage systems. However, maintaining intimate solid–solid contact within NMC-based composite cathodes during repeated lithium extraction and insertion remains a major challenge. Because the stability of these contacts is largely determined by the electrode microstructure established during manufacturing, advanced pressing strategies are increasingly being explored to reduce residual porosity and promote homogeneous particle packing. Here, we compare warm isostatic pressing with conventional cold uniaxial pressing and investigate how the two processing routes affect electrochemical performance and the spatial distribution of mechanical stresses through a combined experimental and numerical approach based on 3Dresolved electrode manufacturing simulations and a fully coupled mechano-electrochemical model. Warm isostatically pressed cathode produces a denser and thinner cathode with reduced porosity, enhanced active material-solid electrolyte contact, improved ionic and electronic transport, and lower geometric. While both cathodes show comparable behavior at C/10, WIP maintains higher accessible capacity and more homogeneous active material utilization at C/2, supported by a more spatially distributed ionic current network. In contrast, hydrostatic-stress differences between WIP and CUP remain comparatively modest. These results establish a