Design of Cu‐Substituted O3‐Type NaFe_0.5Mn_0.5O₂ Cathode Materials for Sodium‐Ion Batteries

Abstract

O3-type Fe/Mn-based layered oxide cathode materials with abundant reserves have a promising prospect in sodium-ion batteries. However, the electrochemical reversibility of most O3-type Fe/Mn-based oxide cathode materials is still not high enough. Herein, the effect of different Cu contents on the electrochemical properties of O3-NaFe 0.50 Mn 0.50 O 2 materials is systematically investigated. The as-prepared NaFe 0.30 Mn 0.50 Cu 0.20 O 2 cathode achieves the synergistic optimization of the interface and bulk phase. It shows superior electrochemical performance, with an initial discharge specific capacity of 114 mAh g À 1 at 0.1 C, a capacity retention rate of 94 % after 100 cycles at 0.5 C, and excellent chemical stability in air and water. In addition, the sodium ion full battery based on NaFe 0.30 Mn 0.50 Cu 0.20 O 2 cathode and hard carbon anode has a capacity retention rate of 81 % after 100 cycles. This research provides a useful approach for the preparation of low-cost and high-performance O3-type layered cathode materials.

Unravelling air/moisture stability of cathode materials in sodium ion batteries: characterization, rational design, and perspectives

“…Zheng et al conducted an in-depth investigation into the controlled-atmosphere storage effects of O3-NaNi 0.5 Mn 0.5 O 2 , 45 a well-documented air-sensitive layered oxide known for its intricate structural degradation tendencies. 32,49 Through XRD analysis (Fig. 2a), it has been shown that O3-NaNi 0.5 Mn 0.5 O 2 experiences a phase transition from the O3 to P3 structure after 15 days of exposure to ambient air.…”

“…63–65 Moreover, FTIR proves invaluable in assessing the air stability of cathode materials. 49,59,60 Since Na 2 CO 3 or NaHCO 3 tends to form on particle surfaces in an amorphous state, detecting these species through XRD proves challenging. However, FTIR proves invaluable in observing carbonate presence on the surface, especially with increased hydration levels as shown in Fig.…”

“…As demonstrated in the previous sections, the composition significantly influences the air stability of materials and doping on both transition metal and sodium sites has proven to be an effective strategy for enhancing air and water stability. Several studies have identified the selection of low-valence cations, such as Li, 78,80,131,157 Cu, 49,153,154,162,163,170 and Mg, 36,181,187,188,190 as elements capable of enhancing stability. Among these, Cu was one of the earliest elements reported to exhibit improved air stability by various researchers, 156,172 with multiple studies demonstrating enhancement in different systems (see Table 3).…”