Achieving Fast Charging and Superior Cycling Stability Single‐Crystal Ni‐Rich Cathodes by Ultrafast Aqueous Washing

ABSTRACT Single‐crystal Ni‐rich layered oxides represent ideal cathodes for high‐energy‐density lithium‐ion batteries due to their high compaction density and volumetric capacity. However, lithium‐excess high‐temperature synthesis generates substantial residual lithium compounds (RLCs; e.g., Li ₂ CO ₃ /LiOH) on particle surfaces. These RLCs elevate interfacial impedance, while protracted Li⁺ diffusion pathways in micrometer‐sized crystals collectively degrade fast‐charge capability and cycling stability. To address these challenges, we develop an efficient strategy employing 3‐min ultrafast washing followed by 600°C annealing for LiNi _0.85 Co _0.1 Mn _0.05 O ₂ single crystals. This approach achieves 80% capacity retention at 5 C charging meeting extreme fast‐charging targets while maintaining superior cycling stability at 1 C. The ultrafast wash removes 94.5% of surface RLCs while confining structural deterioration to a mere 2–4 nm rock‐salt reconstruction layer. Complementarily, in situ X‐ray diffraction (XRD) reveals that this attenuated surface rock‐salt phase enables smooth bulk phase transitions during Li ⁺ (de)intercalation, thereby enhancing structural reversibility, ionic conductivity, and long‐term stability.