Modulating the Interlayer Spacing and Na⁺/Vacancy Disordering of P2-Na_0.67MnO₂ for Fast Diffusion and High-Rate Sodium Storage

Abstract

Modulating the interlayer spacing and Na + /vacancy disordering can significantly affect the electrochemical behavior of P2-type cathode materials. In this work, we prepare a series of P2-Na 0.67 MnO 2 cathodes (Na 0.67 Ni 0.2−x Mn 0.8 Mg x O 2 ) with varying doping amounts of Mg and Ni to realize the maximization of the interlayer spacing within the experimental range and optimize the Na + /vacancy ordering. Consequently, the as-prepared Na 0.67 Ni 0.1 Mn 0.8 Mg 0.1 O 2 illustrates an excellent rate performance of 193 mA h g −1 discharge capacity at 0.1 C (1 C = 180 mA g −1 ), and even at a high rate of 8 C, the battery can deliver a capacity of 70 mA h g −1 . The kinetics analysis indicates the raising of Na + mobility, which could due to the reduced Na + /vacancy ordering and the enhanced Na interlayer spacing. The codoping of Ni and Mg also enhances the stability of the layered structure, leading to improved cycling performance of 74.7% capacity retention after 100 cycles.

Strategies to Build High‐Rate Cathode Materials for Na‐Ion Batteries

“…Similar effect has also been exhibited in Cu‐doped Na 0.67 Ni 0.1 Cu 0.2 Mn 0.7 O 2 , Ca‐doped Na 5/8 Ca 1/24 CoO 2 , Li and Fe co‐doped Na[Li 0.05 (Ni 0.25 Fe 0.25 Mn 0.5 ) 0.95 ]O 2 . Another major role of element doping in layered oxides cathode materials is to modulate the interlayer spacing and suppress Na + /vacancy ordering . It is known that P2‐type cathodes have a larger Na layer spacing compared to O3‐materials, which can tolerate lattice distortion caused by the change of O−O bond length.…”

“…[62] Another major role of element doping in layered oxides cathode materials is to modulate the interlayer spacing and suppress Na + /vacancy ordering. [35,63,64] It is known that P2-type cathodes have a larger Na layer spacing compared to O3-materials, which can tolerate lattice distortion caused by the change of OÀ O bond length. Then, the larger Na layer spacing can effectively inhibit the migration of transition metal ions to alkali metal layers during charging and maintain the original structure.…”

O3‐Type Layered Ni‐Rich Oxide: A High‐Capacity and Superior‐Rate Cathode for Sodium‐Ion Batteries

“…Appealingly, the redox peaks at high‐voltage region (2.6–3.7 V) were very wide and weak, implying the suppressed phase transition in the Na‐NCM811 cathode. This observation may be ascribed to the trace Li‐O3 phase in Na‐NCM811, which can be acted as an excellent pillar to stabilize the layered structure and an effective dopant to disorder Na + /vacancy arrangement during Na + extraction/insertion . Therefore, this suppressed phase transition was expected to promote the cycling performance of cathode material.…”

Bilayered Potassium Vanadate K0.5V2O5 as Superior Cathode Material for Na‐Ion Batteries

“…This finding is in good correlation with the slight interlayer contraction combined with the increasing amount of Na. Scarce data are available on Na + mobility in sodiated oxides and bronzes, with very close values in the range 10 −12 –10 −10 cm 2 s −1 reported for Na 0.33 V 2 O 5 ,, Na x CoO 2 , and P2‐Na 0.67 MnO 2 …”