Understanding of TiO2/Co3O4-modified configuration strategy for stabilizing O3-type NaNi0.4Fe0.2Mn0.4O2 cathodes with enhanced long-term and rate performance

Sodium-ion batteries (SIBs) have recently gained wildly interest due to the abundance of sodium, lower production costs, and better low-temperature performance compared to lithium-ion batteries (LIBs). Among various cathode materials of SIBs, O3-type NaNi 0.4 Fe 0.2 Mn 0.4 O 2 (NFM424) demonstrates high capacity and ease of synthesis, yet suffers from structural degradation and sluggish Na + kinetics caused by large ionic radius and strong electrostatic interactions. To overcome these issues, a configuration strategy combined with TiO 2 and Co 3 O 4 by a simple solid-state reaction method was introduced to improve structural and electrochemical stability. XRD, SEM, TEM, and various electrochemical characterizations as well as TGA/DSC tests were conducted. The resulting NaNi 0.4 Fe 0.2 Mn 0.3 Co 0.05 Ti 0.05 O 2 (NFMCT) cathode mitigated Jahn-Teller distortions and Na + /vacancy ordering while enhancing phase integrity and diffusion pathways. The obtained NFMCT maintained 93.7 mAh·g −1 after 550 cycles at 1 C, with superior rate capabilities at 2 C and 5 C. These findings deepen the understanding of configuration strategy by using multi-element oxide and highlight a practical strategy for designing high-performance SIB cathodes.