Excellent Comprehensive Performance of Na‐Based Layered Oxide Benefiting from the Synergetic Contributions of Multimetal Ions

Abstract

Na‐ion batteries are promising for large‐scale energy storage applications, but few cathode materials can be practically used because of the significant difficulty in synthesizing an electrode material with superior comprehensive performance. Herein, an effective strategy based on synergetic contributions of rationally selected metal ions is applied to design layered oxides with excellent electrochemical performances. The power of this strategy is demonstrated by the superior properties of as‐obtained NaFe0.45Co0.5Mg0.05O2 with 139.9 mA h g−1 of reversible capacity, 3.1 V of average voltage, 96.6% of initial Coulombic efficiency, and 73.9 mA h g−1 of capacity at 10 C rate, which benefit from the synergetic effect of Fe3+ (high redox potential), Co3+ (good kinetics), and inactive Mg2+ with compatible radii (stabilizing structure). Moreover, it is clarified that the superior property is not the simple superposition of performance for layered oxides with single metal ions. With the assistance of density functional theory calculations, it is evidenced that the wide capacity range (>70%) of prismatic Na+‐occupied sites during sodiation/desodiation is responsible for its high rate performance. This rational strategy of designing high‐performance cathodes based on the synergetic effect of various metal ions might be a powerful step forward in the development of new Na‐ion‐insertion cathodes.

Direct Observation of Alternating Octahedral and Prismatic Sodium Layers in O3‐Type Transition Metal Oxides

“…This gliding leads to a much more complex set of phase transformations for NaTMO2 than that for the Li compounds. [7][8][9][10] While most of these transformations appear reversible upon Na extraction and insertion, the hysteresis, inhomogeneity, and stresses associated with the more complex phase transitions in layered Na cathodes can lead to long term stability issues. Understanding these phases is particularly important as Na cathodes need to be charged to a relatively higher level of alkali extraction than Li compounds to make them competitive in light of their lower cell voltage.…”

Layered Oxide Cathodes for Sodium‐Ion Batteries: Phase Transition, Air Stability, and Performance

“…Moreover, with the assistance of DFT calculations (Figure 9b), it is evidenced that the wide capacity range (>70%) of prismatic Na + -occupied sites during Na-(de)intercalation is key factors for its high rate capability. [191] Adv. Energy Mater.…”

Structural Insight into Layer Gliding and Lattice Distortion in Layered Manganese Oxide Electrodes for Potassium‐Ion Batteries

“…[24,[42][43][44][45][46] Further, the minor stability issues of this electrode may be overcome through optimization, such as was achieved for graphitic electrodes used in LIBs which exhibited relatively large instability in the early stages of the technology. We hope that these mechanistic insights will motivate the further improvement of this material in the future, with the doping level yet to be optimized.…”

“…The high toxicity of cobalt also motivates the future exploration of safer and potentially cost‐effective alternative dopants in this material, noting that cobalt is used extensively in many commercial LIB electrodes. Inspired by the ternary materials that successfully led LIB and SIB development, a prospective strategy for designing high‐performance PIB electrodes may lie in the introduction of another inactive metal ion such as Mg 2+ , Zn 2+ , Ni 3+ , or Cr 3+ , to further stabilize the structure . Further, the minor stability issues of this electrode may be overcome through optimization, such as was achieved for graphitic electrodes used in LIBs which exhibited relatively large instability in the early stages of the technology .…”