Han Jin,Niu Yubin,Zhang Yan,Jiang Jian,Bao Shu-juan,Xu Maowen
Novel O3-type Na 0.8 Ni 0.6 Sb 0.4 O 2 is successfully fabricated via a solid-state method and further firstly used as cathode material for sodium-ion batteries (SIBs). The as-obtained material delivers a high capacity of ~107.3 mAh g −1 in the voltage range of 2–4.5 V with two discharge plateaus at 3.24 and 3.62 V, and exhibits a good capacity retention (98.5 mAh g −1 at the rate of 0.2 C after 100 cycles).
The pursuit of advanced battery chemistries with enhanced energy density necessitates the exploration of new materials, a process intricately tied to synthesis science. Despite the promise of O3-type sodium oxygen anionic redox cathodes as high-capacity materials, their development has been severely hindered by a lack of understanding regarding synthetic mechanisms. Here, we elucidate the pivotal role of atmospheric conditions, particularly oxygen content, in the synthesis of such materials by synchronizing multiple operando characterization techniques to monitor changes in both solid and gaseous components. Utilizing the O3-Na[Li 1/3 Mn 2/3 ]O 2 system as a model, we demonstrate that a low oxygen environment is essential and the reaction is highly complex as evidenced by multiple oxygen uptake and release processes, resulting in numerous intermediates. This behavior contrasts sharply with Na-Mn-O and Li-Mn-O ternary systems which show less significant oxygen dynamics, underscoring the unique reaction mechanism within the Na-Li-Mn-O system. We further adopt a dynamic controlled atmosphere approach to modulate oxygen concentration and demonstrate successful synthesis of Ti-substituted NaLi 1/3 Mn 2/3- x Ti x O 2 materials, all exhibiting capacities surpassing 190 mAh g -1 . Our findings highlight the importance of the atmospheric conditions for the synthesis of oxide cathode materials and these fundamental insights unlock avenues for developing novel high-energy-density sodium-ion battery chemistries.
O3-type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM) is recognized as a highly promising cathode material for sodium-ion batteries owing to its cost-effectiveness, substantial theoretical capacity, and facile synthesis. Nevertheless, this material suffers from rapid capacity decay caused by structural degradation and irreversible phase transitions at high voltages (> 4.0 V vs. Na + /Na). Herein, partial substitution of Fe 3+ sites with Ti 4+ in the transition metal layer was implemented. Systematic investigations via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) reveal that Ti substitution effectively stabilizes the layered framework by suppressing detrimental phase transitions through enhanced structural pillar effects. The optimized NaNi 1/3 Fe 0.23 Mn 1/3 Ti 0.1 O 2 delivers a specific capacity of 144.1 mAh g −1 within 2.0–4.2 V at 0.1 C, demonstrating 71.3% capacity retention after 100 cycles at 1 C (130 mA g −1 ). This work establishes a viable strategy for enhancing structural stability in O3-type cathodes through selective cation substitution. Graphical
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