Breaking the Durability–Power Trade‐Off: Boron‐Directed Faceted O3 Cathodes for High‐Rate Sodium‐Ion Batteries

ABSTRACT O3‐type layered cathodes for sodium‐ion batteries (NIBs) are promising cathodes, yet they are limited by irreversible phase transitions at high voltages, structural strain, and sluggish Na + transport, which compromise their cycling and rate performance. Here, a particle engineering strategy using boron oxide to simultaneously stabilize lattice framework, and regulate the crystal facet exposure is proposed. Boron oxide acts as a dual‐function additive, serving as both a flux that governs anisotropic crystal growth and a dopant that reinforces the metal–oxygen network through strong B─O bonding. This dual role drives the formation of submicron hexagonal platelets with a dominant (003) facet orientation and an enlarged Na‐layer spacing, resulting in fast in‐plane Na⁺ diffusion and exceptional structural integrity. Contrary to the conventional view that (003) planes are electrochemically inactive, controlled exposure of these facets suppresses interfacial degradation while maintaining high‐rate kinetics. The optimized boron‐modified cathode achieves excellent cycling stability, with 82.6% capacity retention after 400 cycles at 2C in full cells, together with superior high‐rate performance (92.0 mAh g −1 at 10C). This work illustrates facet engineering via boron modification as an effective and scalable route to reconcile the long‐standing durability–power trade‐off in O3‐type sodium layered oxides.