Breaking boundaries in O3-type NaNi1/3Fe1/3Mn1/3O2 cathode materials for sodium-ion batteries: An industrially scalable reheating strategy for superior electrochemical performance

To address the challenges of air stability and slurry processability in layered transition metal oxide O3-type NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM) for sodium-ion batteries (SIBs), we have designed an innovative 500 °C reheating strategy. This method improves the surface properties of NFM without the need for additional coating layers, making it more efficient and suitable for large-scale applications. Pristine NFM (NFM-P) was first synthesized through a high-temperature solid-state method and then modified using this reheating approach (NFM-HT). This strategy significantly enhances air stability and electrochemical performance, yielding an initial discharge specific capacity of 151.46 mAh/g at 0.1C, with a remarkable capacity retention of 95.04% after 100 cycles at 0.5C. Additionally, a 1.7 Ah NFM||HC (hard carbon) pouch cell demonstrates excellent long-term cycling stability (94.64% retention after 500 cycles at 1C), superior rate capability (86.48% retention at 9C), and strong low-temperature performance (77% retention at − 25 °C, continuing power supply at − 40 °C). Notably, even when overcharged to 8.29 V, the pouch cell remained safe without combustion or explosion. This reheating strategy, which eliminates the need for a coating layer, offers a simpler, more scalable solution for industrial production while maintaining outstanding electrochemical performance. These results pave the way for broader commercial adoption of NFM materials.