Prussian Blue@C Composite as an Ultrahigh‐Rate and Long‐Life Sodium‐Ion Battery Cathode

Abstract

Rechargeable sodium ion batteries (SIBs) are surfacing as promising candidates for applications in large-scale energy-storage systems. Prussian blue (PB) and its analogues (PBAs) have been considered as potential cathodes because of their rigid open framework and low-cost synthesis. Nevertheless, PBAs suffer from inferior rate capability and poor cycling stability resulting from the low electronic conductivity and defi ciencies in the PBAs framework. Herein, to understand the vacancy-impacted sodium storage and Na-insertion reaction kinetics, we report on an in-situ synthesized PB@C composite as a high-performance SIB cathode. Perfectly shaped, nanosized PB cubes were grown directly on carbon chains, assuring fast charge transfer and Na-ion diffusion. The existence of [Fe(CN) 6 ] vacancies in the PB crystal is found to greatly degrade the electrochemical activity of the Fe LS (C) redox couple via fi rst-principles computation. Superior reaction kinetics are demonstrated for the redox reactions of the Fe HS (N) couple, which rely on the partial insertion of Na ions to enhance the electron conduction. The synergistic effects of the structure and morphology results in the PB@C composite achieving an unprecedented rate capability and outstanding cycling stability (77.5 mAh g −1 at 90 C, 90 mAh g − 1 after 2000 cycles at 20 C with 90% % capacity retention).

Monoclinic Sodium Iron Hexacyanoferrate Cathode and Non-Flammable Glyme-Based Electrolyte for Inexpensive Sodium-Ion Batteries

“…The XRD plot looked almost identical to that reported for the monoclinic Na 2 Mn[Fe(CN) 6 ].1.87H 2 O and monoclinic Na 2 Mn 2 (CN) 6 .2H 2 O with the space group P2 1 /n. 27,40 In fact, the structural model proposed for M-Na 2-δ Mn[Fe(CN) 6 ].1.87H 2 O resulted in satisfactory fitting for the as-synthesized material with favorably low refinement reliability factors (R wp = 7.42%, R Bragg = 4.621%, χ 2 = 3.39%, and R exp = 2.19%) with similar lattice parameters: a = 10.45983 (56) Å, b = 7.51295 (42) Å, c = 7.27153 (48) Å and β = 92.7379 (33) • (refer to Table S2 for the atomic coordinates). 40 Henceforth, the assynthesized material shall be referred as M-Na 2 Fe 2 (CN) 6 .2H 2 O.…”

“…[24][25][26][27] Most of the PBAs which have been reported to store sodium have less Na content in the as-synthesized compounds (0 ≤ x ≤ 1) demonstrating a cubic structure with a space group Fm-3m. [28][29][30][31][32][33] This may become a disadvantage in a full cell formulation against a suitable anode as a full cell relies on the cathode supplying Na during the first charging (sodium extraction from cathode and insertion into the anode). An x = 1 value would mean that the practically achieved capacity of such a cathode would be half of its theoretical capacity (corresponding to the capacity for an analogous cathode with x = 2) in a practical full cell assuming no loss of Na due to surface passivation and 100% coulombic efficiency for both cathode and anode.…”

“…[28][29][30][31][32][33][34][35][36][37][38] Goodenough et al synthesized Na rich PBAs with x ≈ 2 at an elevated temperature of 140…”

Sodium‐Ion Batteries: From Academic Research to Practical Commercialization

“…These cathode materials include layer-structured transition metal oxides, [4][5][6] polyanionic-type compounds, [7,8] Prussian blue analogues, [9,10] and organic-based materials. [11,12] Meanwhile, significant progress has also been made on anode materials for SIBs, and various materials have been explored as promising candidates, including carbonaceous materials, [13][14][15] metals or alloys, [16][17][18][19][20] phosphorus, [21,22] phosphide, [23,24] oxides, [25,26] sulfides, [27,28] and phosphates.…”

MgFe 2 O 4 hollow microboxes derived from metal-organic-frameworks as anode material for sodium-ion batteries

“…The metal-organicframeworks (MOFs) assembled by clusters/metal ions coordinated to organic ligands, usually form a uniform size, and possess interior cavities and porous shells after heat treating [6,7]. For example, Prussian blue (PB) containing the (C"N) À anions has been proved to have a high energy density, a small volume change during cycling, and stable rate capability in Na half-cells [8,9].…”