Trace Y Doping Regulated Bulk/Interfacial Reactions of P2‐Layered Oxides for Ultrahigh‐Rate Sodium‐Ion Batteries

Abstract

AbstractP2‐phase layered cathodes play a pivotal role in sodium‐ion batteries due to their efficient Na+ intercalation chemistry. However, limited by crystal disintegration and interfacial instability, bulk and interfacial failure plague their electrochemical performance. To address these challenges, a structural enhancement combined with surface modification is achieved through trace Y doping. Based on a synergistic combination of experimental results and density functional theory (DFT) calculations, the introduction of partial Y ions at the Na site (2d) acts as a stabilizing pillar, mitigating the electrostatic repulsions between adjacent TMO2 slabs and thereby relieving internal structural stress. Furthermore, the presence of Y effectively optimizes the Ni 3d‐O 2p hybridization, resulting in enhanced electronic conductivity and a notable rapid charging ability, with a capacity of 77.3 mA h g−1 at 40 C. Concurrently, the introduction of Y also induces the formation of perovskite nano‐islands, which serve to minimize side reactions and modulate interfacial diffusion. As a result, the refined P2‐Na0.65 Y0.025[Ni0.33Mn0.67]O2 cathode material exhibits an exceptionally low volume variation (≈1.99%), an impressive capacity retention of 83.3% even at −40 °C after1500 cycles at 1 C.