Elucidating ionic-electronic transport in cation-disordered rocksalt cathodes.

High-capacity cation-disordered rocksalt (DRX) cathodes have created new opportunities for low-cost, high-energy-density lithium-ion batteries. By combining cationic and anionic redox reactions, Li-excess DRX cathodes can deliver capacities beyond those of conventional layered oxides. However, their practical implementation is still constrained by sluggish Li+ transport, intrinsically poor electronic conductivity, severe interfacial instability at high voltages, as well as the frequent demands for nanosized particles and large fractions of conductive carbon. In this review, we critically summarize recent progress in understanding ionic-electronic transport in DRX cathodes. We first discuss Li+ migration through 0-TM percolation networks, the influence of short-range ordering (SRO) and heterogeneous Li-site energy landscapes, and strategies for enhancing ionic transport through SRO regulation, δ-phase formation, partial disordering, and activation of additional diffusion pathways. Then electronic transport mechanisms are analyzed based on localized small-polaron hopping, and the electronic-structure and electrode-level approaches are reviewed for improving conductivity. Finally, design principles are proposed that balance Li+ percolation, electronic conduction, d0 transition-metal selection, local ordering, and interfacial stability, and future directions for scalable synthesis, electrolyte/interface engineering, all-solid-state batteries, advanced characterization, and data-driven materials discovery are outlined.