Thick electrode design for lithium-ion batteries from an ion-electron coupled transport perspective: from independent regulation to cooperative design

Thick electrodes can boost energy density and lower costs in lithium-ion batteries without altering chemistries, but they impede ion and electron transport, causing kinetic degradation. This work reviews multiscale kinetic optimization strategies and clarifies the fundamental limitations of independently enhancing ionic or electronic transport. By introducing the coupled ion-electron transfer theory, it demonstrates that reactions are governed by the spatiotemporal coordination of ion and electron transport, rather than either pathway alone. From a macro-flux perspective, transport mismatch is amplified in thick electrodes, resulting in spatially shifting reaction-inactive regions across the thickness. A reformulated Damköhler number incorporating both transport pathways defines a hybrid ion-electron control zone for uniform reactions. Based on this framework, dual-continuous, spatially decoupled networks and spatially coupled mixed ion-electron conductors are proposed as rational design principles. This work shifts thick-electrode design from empirical structural tuning toward mechanism-based system engineering.