Coherent 1T‐Phase Surface Architecture Unlocks Ultrafast and Durable High‐Voltage LiCoO 2 Cathodes

ABSTRACT Nowadays, fast‐charging capability in battery materials is intensively pursued in both academia and industry, yet the crystallographic factors that fundamentally determine rapid Li + transport remain unclear. Here, we identify the theoretical structural capacity for collective Li + transport, defined by the availability of crystallographically accessible Li diffusion sites, as a decisive but previously underappreciated structural origin governing interfacial Li + transport, and introduce Li‐site density (ρ Li‐site ) as a quantitative descriptor to guide surface architecture design for accelerated Li + migration. Guided by this principle, we construct a coherent and fluorinated 1T‐Li 1 + x CoO 2 − y F y surface structure on LiCoO 2 , which simultaneously preserves crystallographic compatibility with the O3 matrix and provides an exceptionally high ρ Li‐site (∼48 sites·nm −3 ), substantially exceeding those of commonly employed frameworks (≤ 31 sites·nm −3 ). The modified cathode delivers unprecedented rate capability, achieving 183 and 175 mAh g −1 at 10C and 20C, respectively. In‐situ synchrotron x‐ray and neutron diffraction results further reveal that the 1T phase effectively suppressed O3 to H1‐3 phase transitions and stabilized oxygen frameworks, enabling outstanding cycling stability with 87% capacity retention after 500 cycles. This work establishes Li site density‐guided surface engineering as a general structural principle for simultaneously improving interfacial reaction kinetics and structural durability in high‐voltage layered oxide cathodes.