Surface-enriched Co engineering promoting electronic conductivity for single-crystalline Ni-based layered oxide cathodes

Single-crystalline layered oxides are at the forefront of the development of high-energy lithium-ion battery (LiB) electrode materials, offering prolonged durability by circumventing the crack-related structural reconstruction and mechanical collapse seen in their polycrystalline counterparts. However, the sluggish carrier transport in large-crystalline particles impedes their rate capability. While most research has prioritized improving ion diffusion, the pivotal role of electron transport in electrochemical kinetics has been relatively overlooked. Herein, we enhance the kinetics of charge transfer and inhibit Mn dissolution from the bulk lattice by modulating the cobalt concentration on the surface of a single-crystalline Ni-based layered oxide cathode, LiNi0.5Co0.2Mn0.3O2. Liquid pouch-type full cells employing surface Co-concentrated cathodes exhibit exceptional hightemperature (55 C) specific capacity (193.6 mAh g(-1) at 0.2C), capacity retention (90.1 % after 2000 cycles at 1 C), and impressive rate performance at 12C. Moreover, by utilizing the varying composition-related kinetics in the composite cathode of sulfide-based all-solid-state batteries (ASSBs), we find that surface-enriched Co modification enhances the electronic percolation within the composite cathode, significantly contributing to the rate performance of ASSBs, beyond the effect of ion diffusion. This research underscores the significance of electronic properties in single-crystalline layered oxides for achieving high-power LiBs and ASSBs.