Regulation Engineering of Alkali Metal Interlayer Pillar in P2-Type Cathode for Ultra-High Rate and Long-Term Cycling Sodium-Ion Batteries

Layered oxides have attracted significant attention as cathodes for sodium-ion batteries (SIBs) due to their compositional versatility and tuneable electrochemical performance. However, these materials still face challenges such as structural phase transitions, Na⁺/vacancy ordering, and Jahn-Teller distortion effect, resulting in severe capacity decay and sluggish ion kinetics. We develop a novel Cu/Y dual-doping strategy that leads to the formation of "Na-Y" interlayer aggregates, which act as structural pillars within alkali metal layers, enhancing structural stability and disrupting the ordered arrangement of Na⁺/vacancies. This disruption leads to a unique coexistence of ordered and disordered Na⁺/vacancy states with near-zero strain, which significantly improves Na⁺ diffusion kinetics. This structural innovation not only mitigates the unfavorable P2-O2 phase transition but also facilitates rapid ion transport. As a result, the doped material demonstrates exceptional electrochemical performance, including an ultra-long cycle life of 3000 cycles at 10 C and an outstanding high-rate capability of ~70 mAh g^-1 at 50 C. The discovery of this novel interlayer pillar, along with its role in modulating Na⁺/vacancy arrangements, provides a fresh perspective on engineering layered oxides. It opens up promising new pathways for the structural design of advanced cathode materials toward efficient, stable, and high-rate SIBs.