Lithium–Borate Interphase Enables High‐Rate and Long‐Lifespan Ni‐Rich Layered Oxide Cathodes

The growing demand for fast‐charging and high‐power electric vehicles is shifting Ni‐rich cathode design from maximizing energy density alone toward sustaining rapid Li‐ion transport over long cycling. LiNi x Co y Al z O 2 is well suited to this target because its Mn‐free, Al‐stabilized layered framework offers high capacity and structural robustness, yet residual alkaline lithium species on the particle surface compromise electrode processing, interfacial kinetics and long‐term durability. Here we convert these residual lithium species on LiNi 0.88 Co 0.09 Al 0.03 O 2 (NCA) surface into a functional lithium–borate interphase through a boric‐acid‐mediated surface reaction (NCA‐B). Rather than simply removing surface residues, this strategy suppresses parasitic interfacial chemistry while maintaining efficient Li‐ion transport. In Ah‐level NCA‐B||graphite pouch cells, the modified cathode retains 76.9% capacity after 2000 cycles at 1 C and sustains nearly decay‐free cycling for 2400 cycles under 1 C charge and 10 C discharge, with a voltage‐fade rate of 0.0375 mV per cycle. These results establish residual‐lithium conversion as a practical interfacial design principle for high‐rate, long‐life NCA batteries.