Preparation and electrochemical performance of nanowire-shaped Na₃Mn_2−xFe_x(P₂O₇)(PO₄) for sodium-ion and lithium-ion batteries

Abstract

A series of Fe-doped Na3Mn2-xFex(P2O7)(PO4) (x = 0.0, 0.2, 0.4) (abbreviated as NMFP-0/NMFP-0.2/NMFP-0.4) compounds have been successfully prepared by using sol-gel method. The Rietveld refinement results indicate that single-phase Na3Mn2-xFex(P2O7)(PO4)...

Manganese‐based polyanionic cathodes for sodium‐ion batteries

“…Optimally, acceptable results can be obtained when the Mn/Fe ratio is 1:1 (Figure 8e) [78] . Moreover, these resulting binary phases follow the same single-phase reaction mechanism as Na 3 Mn 2 PO 4 P 2 O 7 [78,150] . For Na 2+2z Mn 2−z (SO 4 ) 3−x (SeO 4 ) x using monoclinic C2/c alluaudite-type structure, it can be regarded as a derivative obtained by partial substitution of SO 4 2− in Na 2 Mn 2 (SO 4 ) 3 with SeO 4 2− .…”

“…Such electrode materials usually contain two or more polyanionic units, and the pairing of different anion groups can broaden the structural and redox potential diversity. For Mn-based materials, Na 3 MnPO 4 CO 3 [79,[140][141][142][143][144][145][146] , Na 4 Mn 3−x M x (PO 4 ) 2 P 2 O 7 (M is one or more of Fe, Co and Ni, 0 ≤ x < 3) [70][71][72][73][74][75][147][148][149] , Na 3 Mn 2−x Fe x PO 4 P 2 O 7 (0 ≤ x < 2) [76][77][78]150] , and Na 2+2z Mn 2−z (SO 4 ) 3−x (SeO 4 ) x [151] have been reported so far.…”

“…Suffice it to say that the key challenge facing Mn-based polyanions is that materials with excellent properties are not so easy to synthesize, which may be one of the reasons for the slow progress in the research of such materials; after all, it is not good to be surrounded by negative energy all the time. To modify the electrochemical properties of Mn-based polyanions, nanostructure design is a successful attempt, such as hollow spheres, nanofibers, and hydrangeas [25,56,99,150] .…”

“…Optimally, acceptable results can be obtained when the Mn/Fe ratio is 1:1 (Figure 8e) [ 78 ] . Moreover, these resulting binary phases follow the same single‐phase reaction mechanism as Na 3 Mn 2 PO 4 P 2 O 7 [ 78,150 ] .…”

Structurally Modulated Na4–xFe3–xVx(PO4)2P2O7 by Vanadium Doping for Long-Life Sodium-Ion Batteries

“…The low cost, high stability, and wide distribution of feedstock costs offered by sodium-ion batteries (SIBs) make them well-suited for fulfilling the demands of large-scale electrochemical energy storage systems. − However, SIBs still have great challenges; despite having the same working principle as lithium-ion batteries (LIBs), they are limited by the ionic radius (Na + : 1.02 Å; Li + : 0.76 Å), which leads to poor de-embedding capability. Therefore, there is a need to develop more suitable electrode materials to fulfill large-scale storage requirements. − In recent years, there has been a progression in sodium-ion cathode materials, with the emergence of various materials including transition-metal oxides, − polyanion materials, − and Prussian analogues. − Iron-based polyanion materials with low raw material cost, high thermal stability, and environmental friendliness have gained a lot of attention for their advantages. − Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (NFPP, theoretical capacity: 129 mA h g –1 ) was connected by combining [PO 4 ] and [P 2 O 7 ] groups with [FeO 6 ] octahedra, based on the redox Fe 2+ /Fe 3+ (average working voltage: 3.1 V), to realize the de-embedding of Na + in the cathode. Kim et al reported NFPP as a sodium-ion cathode material with a high reversible capacity of 113.5 mA h g –1 , marking the first discovery of such quality.…”