P2-type Na0.67Fe0.3Mn0.3Co0.4O2 cathodes for high-performance sodium-ion batteries

Sodium-ion batteries have attracted increasing attention due to the preponderance of nontoxicity, naturally elemental abundance, and low cost of the metal sodium. However, the electrochemical performance, including rate capability and cycling performance of the cathodes are still the pivotal shortcomings for the large scale application. Herein, a series of layered Na0.67(Fe0.5Mn0.5)1-χCoχO2 (χ = 0, 0.2, 0.4, 0.5) used as cathodes for sodium-ion batteries were synthesized via a solid-state reaction. Owing to the Co-substitution into the Na0.67Fe0.5Mn0.5O2, the rate performance and capacity retention of the cathodes for sodium-ion batteries were significantly elevated. Compared to the Na0.67Fe0.5Mn0.5O2 cathode, the Na0.67Fe0.3Mn0.3Co0.4O2 cathode exhibited an exceptional capacity retention (retaining 85.5% of its initial capacity after 100 cycles at 1C), as well as excellent rate capabilities (136.7 mAh g−1 at 0.2C, and 81.1 mAh g−1 at 5C). Such an outstanding electrochemical performance endows the P2-type Na0.67Fe0.3Mn0.3Co0.4O2 to be a promising cathode material for high-performance sodium-ion batteries in the near future.