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.