Understanding the Lithium Storage Mechanism in Core–Shell Fe₂O₃@C Hollow Nanospheres Derived from Metal–Organic Frameworks: An In operando Synchrotron Radiation Diffraction and in operando X-ray Absorption Spectroscopy Study

Abstract

In this work, a core-shell structure Fe2O3@C hollow nanospheres derived from metal-organic frameworks is used as anode material for Liion batteries. This material delivers reversible capacity of 928 mAh g-1 at 0.2 A g-1 in 1 M LiPF6 in ethylene carbonate: dimethyl carbonate=1:1. While1 M Lithium bis (trifluoromethane sulfonyl) imide is used as conductive salt, it delivers only 644 mAh g-1 at 0.2 A g-1. In operando synchrotron radiation diffraction revealed that the intermediate phases LixFe2O3 (R3 ̅ m, hexagonal) and LixFe2O3 (Fd3 ̅ m, Li-lean) form and subsequently convert to LixFe2O3 (Fd3 ̅ m, Li-rich), which finally transforms into Fe, Li2O, and LixFe2O3 (Fd3 ̅ m, X phase). During the de-lithiation process, the material does not return to the initial Fe2O3 structure. Instead, the partially de-lithiated Lix-1Fe2O3 (Fd3 ̅ m, X phase) and an amorphous metallic Fe phase remain. The Fe K-edge transition and the formation of Fe are confirmed by the in operando X-ray absorption spectroscopy measurement. Furthermore, the resistive contributions of this material in the two type of Li-salt are evaluated by electrochemical impedance spectroscopy, which highlight a different type of solid electrolyte interphase induced by the salt. This work provides fundamental insights on understanding the lithium-ion storage mechanism in conversion-type electrodes.

Effect of Continuous Capacity Rising Performed by FeS/Fe3C/C Composite Electrodes for Lithium‐Ion Batteries

“…This demonstrates that the FeS/Fe 3 C/C electrode has rapid electrochemical reaction kinetics, which benefits from the addition of the interconnected carbon balls. Moreover, the slope in the low‐frequency region for the FeS/Fe 3 C/C electrode is larger than that for the FeS electrode, which implies faster Li + mobility in the FeS/Fe 3 C/C electrode …”

“…Moreover,t he slope in the low-frequency region for the FeS/Fe 3 C/C electrode is larger than that for the FeS electrode, which implies faster Li + mobility in the FeS/Fe 3 C/C electrode. [43,44] Figure10d isplays R values as calculated with Relaxis 3s oftware in lithiationa nd delithiation conditions. The electrolyte resistance R el for the FeS/Fe 3 C/C electrode (11 W)i sa lmost unchanged upon cycling, whereas the R el for the FeS electrode first increases until the 100th cycle, then it remains quite stable at 8 W (Figure10a,d).…”

In-situ/operando characterization techniques in lithium-ion batteries and beyond

“…The conversion process and lithium storage mechanism of different metal oxides and carbon composite anode in lithium-ion batteries were researched likewise by in-situ XAS (Fig. 13(c)) [143][144][145][146][147][148]. In Li and coworker's work, the lithium storage performance of Fe 2 O 3 @C core-shell nanospheres was investigated by means of in-operando XAS as well as XRD.…”

“…In Li and coworker's work, the lithium storage performance of Fe 2 O 3 @C core-shell nanospheres was investigated by means of in-operando XAS as well as XRD. The Fe K-edge shifting corresponding to phase transition revealed by operando XRD, clearly showed the existence of intermediate Li x -Fe 2 O 3 phase [147]. With both high coulombic efficiencies and good mass transportation, RuO 2 attracted much attention within the metal-oxide anodes.…”

Macaroni‐Like Blue‐Gray Nb2O5 Nanotubes for High‐Reversible Lithium‐Ion Storage

“…[ 7 ] Thus, it is highly desirable to search for low‐cost anode materials with high specific capacity and long‐term cyclability. In this regard, transition‐metal oxides, such as MnOm, [ 8,9 ] MnO 2 , [ 10 ] Mn 3 O 4 , [ 11 ] Co 3 O 4 , [ 12,13 ] CuO, [ 14,15 ] Fe 3 O 4 , [ 16,17 ] and Fe 2 O 3 , [ 18,19 ] sulfides like Co 1− x S [ 20 ] and carbides [ 21,22 ] have been extensively exploited because of their high rechargeable capacities. Among them, Nb 2 O 5 is a potential material in energy storage like lithium‐/sodium‐ion batteries or supercapacitors, [ 23–30 ] except for its applications in photocatalytic, [ 31 ] electron transport layer in solar cell, [ 32,33 ] and electronic‐like electron field emitters.…”