Dual-carbon decorated Na3Mn2(P2O7)(PO4) nanocomposite via freeze drying: A zero-strain cathode material for sodium ion batteries

Preparation and electrochemical performance of nanowire-shaped Na3Mn2−xFex(P2O7)(PO4) for sodium-ion and lithium-ion batteries

“…7 shows, Mn ion can be detected on the sides that have no direct contact with the electrode. Compared to the non-doped Na 3 Mn 2 (P 2 O 7 )(PO 4 ), 22 the dissolution is suppressed by Fe doping and carbon coating.…”

Revealing the phase evolution in Fe-based polyanionic cathode materials for low-cost and high-performance sodium-ion batteries: the case of Na4FexP4O12+x (2≤x≤4)

“…Notably, one polyanionic cathode of Na 3 Fe 2 (PO 4 )P 2 O 7 was reported in the past few years, which can be rewritten as Na 4 Fe 2.67 P 4 O 14.67 with the same composition of Na 4 Fe x P 4 O 12 + x when x is 2.67. [29][30][31] However, the crystallographic data and structure of Na 3 Fe 2 (PO 4 )P 2 O 7 are still not available. According to the relation of formation energy in Fig.…”

“…One sample is located at x = 2.70, which has the same diffraction peak and element ratio as the Na 3 Fe 2 (PO 4 )P 2 O 7 (Na 4 Fe 2.67 P 4 O 14.67 ) materials. [29][30][31] The XRD can be accurately re ned using the phase of NFPO and NFPP with a low Rwp of 2.04% (Figure S2), implying that the material with the composition of Na 3 Fe 2 (PO 4 )P 2 O 7 is a two-phase mixture. Another sample is located at x = 3.31 (Na 4 Fe 3.31 P 4 O 15.31 ), which is re ned as a mixture of NFPP and NFP (Figure S3).…”

“…In contrast, the threephase mixture is usually formed by a solid-state method or Na 4 P 2 O 7 as raw material due to the inhomogeneous ion distribution. [29,30] Besides, when the NFPP sample is synthesized according to the stoichiometric ratio (Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 ), it inescapably contains an NFP impure phase with a weight fraction of about 4% (Fig. 2g and Figure S4).…”

Revealing the Phase Evolution in Na4FexP4O12+x (2 ≤ x ≤ 4) Cathode Materials

“…It is worth noting that there is no three-phase coexistence region in the Na 4 Fe x P 4 O 12+ x system, which benefits from the optimal experimental scheme. In contrast, the three-phase mixture is usually formed by a solid-state method or Na 4 P 2 O 7 as raw material due to the inhomogeneous ion distribution. , Besides, when the NFPP sample is synthesized according to the stoichiometric ratio (Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 ), it inescapably contains an NFP impure phase with a weight fraction of about 4% (Figure S4). This phenomenon has been widely reported in previous works. − Surprisingly, a high phase-pure NFPP can be obtained when x is 2.91, and the Rietveld refinements results of Na 4 Fe 2.91 P 4 O 14.91 ( x = 2.91) show that a few Fe vacancies exist in the structure (Figure S5 and Table S5).…”