Dual‐Strategy of Cation‐Doping and Nanoengineering Enables Fast and Stable Sodium‐Ion Storage in a Novel Fe/Mn‐Based Layered Oxide Cathode

Abstract

Iron/manganese‐based layered transition metal oxides have risen to prominence as prospective cathodes for sodium‐ion batteries (SIBs) owing to their abundant resources and high theoretical specific capacities, yet they still suffer from rapid capacity fading. Herein, a dual‐strategy is developed to boost the Na‐storage performance of the Fe/Mn‐based layered oxide cathode by copper (Cu) doping and nanoengineering. The P2‐Na 0.76 Cu 0.22 Fe 0.30 Mn 0.48 O 2 cathode material synthesized by electrospinning exhibits the pearl necklace‐like hierarchical nanostructures assembled by nanograins with sizes of 50–150 nm. The synergistic effects of Cu doping and nanotechnology enable high Na + coefficients and low ionic migration energy barrier, as well as highly reversible structure evolution and Cu/Fe/Mn valence variation upon repeated sodium insertion/extraction; thus, the P2‐Na 0.76 Cu 0.22 Fe 0.30 Mn 0.48 O 2 nano‐necklaces yield fabulous rate capability (125.4 mA h g −1 at 0.1 C with 56.5 mA h g −1 at 20 C) and excellent cyclic stability (≈79% capacity retention after 300 cycles). Additionally, a promising energy density of 177.4 Wh kg −1 is demonstrated in a prototype soft‐package Na‐ion full battery constructed by the tailored nano‐necklaces cathode and hard carbon anode. This work symbolizes a step forward in the development of Fe/Mn‐based layered oxides as high‐performance cathodes for SIBs.

Boosting the Redox Kinetics of High‐Voltage P2‐Type Cathode by Radially Oriented {010} Exposed Nanoplates for High‐Power Sodium‐Ion Batteries

“…The obtained large capacity and high voltage of the full cell at high rates ensure that an energy density of ≈165 Wh kg −1 can be maintained even at 10 C in Figure 7f (corresponding to state‐of‐the‐art power density of ≈1650 W kg −1 ). The energy density and power density of this P2‐NaNCMO//hard carbon are compared with those previously reported in literatures, [ 55–64 ] as shown in Figure 7g and Table S2, Supporting Information. This P2‐NaNCMO//hard carbon full cell shows a higher energy density and a higher power density.…”

Research progress in O3-type phase Fe/Mn/Cu-based layered cathode materials for sodium ion batteries

“…Nano engineering technology can also improve the Na + storage performance of Fe–Mn-based oxide cathodes. Shen et al 144 synthesized a Na 0.76 Cu 0.22 Fe 0.30 Mn 0.48 O 2 cathode material by electrospinning, which achieved a higher Na + coefficient (the D Na + values of Na 0.76 Cu 0.22 Fe 0.30 Mn 0.48 O 2 (10 −10 to 10 −11 cm 2 s −1 ) than the Cu-free Na 2/3 Fe 1/2 Mn 1/2 O 2 cathode (10 −11 to 10 −12 cm 2 s −1 )) and reversible structural evolution during insertion/extraction of Na + . Pearl necklace-like hierarchical nanostructures were assembled from nanograins with sizes of 50–150 nm, which could expose more active sites for favourable contact with the electrolyte and shortening the distance for Na + diffusion (Fig.…”

Iron‐Based Layered Cathodes for Sodium‐Ion Batteries

“…[50] Coupling Cu with FeÀ Mn based layered oxides is another milestone that offers a new choice of cathode materials to build cost-effective SIBs. [126][127][128][129][130][131][132] Note that, CuÀ FeÀ Mn ternary oxides, such as P2type Na 7/9 Cu 2/9 Fe 1/9 Mn 2/3 O 2 and O3-type Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 O 2 , exhibit outstanding stabilities even when soaked in water, which is mainly attributed to the incorporation of Cu and the resulted higher average sodium-storage voltages. [53,127] By integrating Cu 2 + /Cu 3 + and Fe 3 + /Fe 4 + redox couples, P2-type Na 7/9 Cu 2/9 Fe 1/9 Mn 2/3 O 2 delivers a reversible capacity of 89 mAh g À 1 (0.1 C within 4.2-2.5 V) with an average discharge voltage of 3.6 V, while O3-type Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 O 2 yields over 100 mAh g À 1 (0.1 C within 4.05-2.5 V) with an average voltage of 3.2 V (Figure 12a, b).…”