Stress-modulated ionic transport limits composite cathode kinetics in solid-state batteries

High-energy all-solid-state batteries require thick composite cathodes, yet these architectures exhibit heterogeneous reaction distributions that limit performance. Here, we show that chemo-mechanical transport switching governs the spatiotemporal lithiation behaviour in such electrodes. By combining operando depth-resolved diffraction with microstructureresolved and multi-scale simulations, we link utilisation gradients to the dominant transport pathway and demonstrate that the reversal of reaction fronts between charge and discharge arises from dynamically evolving transport limitations. This switching originates from the coupled reconfiguration of electronic and ionic transport networks during cycling. Particle breathing and interfacial delamination disrupt electronic percolation, while stress-field interactions within the solid electrolyte introduce a mechanics-dependent limitation on ionic transport. This stress-limited ionic conduction, governed by the activation volume and elastic properties of the electrolyte, can reduce effective conductivity by orders of magnitude as cathode interparticle spacing decreases and stress fields begin to overlap at high activematerial loadings. Our findings establish a direct link between chemo-mechanical evolution and transport control in solid-state cathodes, and highlight the need for solid electrolytes with low pressure sensitivity and sufficient mechanical compliance to enable high-energy all-solid-state battery architectures.