Constructing Mechanical–Chemical Stability via Multiphase Riveting and Interface Optimization Toward Layer‐structured Oxide Cathode Material

Abstract Manganese‐based layer‐structured oxide materials are considered as one of the most competitive cathode materials for sodium‐ion batteries due to their low cost and efficient sodium intercalation chemistry. Their electrochemical performance, however, is hindered by mechanical and chemical failures stemming from weak interlayer interactions, the Jahn–Teller effect of Mn 3+ and unstable surfaces. To address these issues, a quenching method was employed to fabricate a robust multiphase structure with a fluorine and dislocation‐rich surface. Through the accumulation of dislocations and the interlocking of multiphase structures, the mechanical stability of the material during (de)sodiation processes is enhanced, while the surface fluorine anchoring further strengthens the chemical stability. Even after 200 cycles at 0.5 C and 1 C within the voltage range of 1.5–4.5 V, the designed composite material P2/P3/O3‐Na 0.89 Ni 0.3 Mn 0.55 Cu 0.1 Ti 0.05 O 1.94 F 0.06 exhibits impressive capacity retention rates of 87.17% and 90.4%, respectively. This work exemplifies the important role of simultaneous design of mechano‐chemically coupled materials for the development of high performances cathode materials.