Study of TiO₂-Coated α-Fe₂O₃ Composites and the Oxygen-Defects Effect on the Application as the Anode Materials of High-Performance Li-Ion Batteries

Abstract

TiO 2 -coated Fe 2 O 3 composites exhibiting high electrochemical stability with oxygen defects were synthesized as the anode materials of Li-ion batteries using an easy sol−gel method. The industrial submicron-sized Fe 2 O 3 with no special shape and commercial tetrabutyl titanate were adopted as raw materials. The phase structures, morphologies, and elements distribution on the surface were characterized by X-ray diffraction analysis, electron paramagnetic resonance, scanning electron microscopy, X-ray photoelectron spectroscopy, and so forth. Results indicated that TiO 2 was well coated on the surface of raw Fe 2 O 3 with an average thickness of 5.5 nm, and the oxygen defects were successfully introduced into the composites with the reduction treatment. Electrochemical characterization indicated that TiO 2 coating was beneficial to the cycle performance of Fe 2 O 3 . The coating layer significantly improved the electronic conductivity and cycling stability of the Fe 2 O 3 anode material, as theoretically supported by the density functional theory calculation. Moreover, the introduction of oxygen defects in samples resulted in more excellent cycling stability compared to that in samples without reduction. The reduced Fe 2 O 3 @0.2TiO 2 sample exhibited a specific discharge capacity of 405.6 mA h•g −1 after 150 cycles, which effectively improved the intrinsic cycling performance of Fe 2 O 3 , and a corresponding discharge capacity of 50 mA h•g −1 after 30 cycles.

Design and synthesis of yolk–shell Fe2O3/N-doped carbon nanospindles with rich oxygen vacancies for robust lithium storage

“…It has been demonstrated that oxygen vacancies, not only facilitate faster charge transport kinetics, but are also beneficial to retain the integrity of the electrode structure, thus enhancing the electrochemical activity. 22 As shown in Fig. 4, the morphologies and microstructure of the Fe 2 O 3 spindles, Fe 2 O 3 @SiO 2 , Fe 2 O 3 @SiO 2 @PDA and YS-Fe 2 O 3 @NC composites, were examined by SEM and TEM.…”

“…19,20 Oxygen vacancies in transition metal oxides are significant owing to their role as electron donors. 21 For example, Ma et al 22 reported a yolk@shell structure of TiO 2 @Fe 2 O 3 with oxygen vacancies for LIBs. These oxygen vacancies in Fe 2 O 3 served as shallow donors, and effectively improved the electronic properties of Fe 2 O 3 nanostructures, leading to excellent rate capability and superior cycling stability.…”

Two‐in‐one shell configuration for bimetal selenides toward fast sodium storage within broadened voltage windows

“…On proof of this concept, herein, we report a twoin-one shell configuration of carbon and titanium dioxide for bimetal selenides to achieve fast and stable sodium storage within broadened voltage windows. Titanium dioxide quantum dots with high ionic conductivity and the "zero-strain" characteristic are expected to allow fast pass-through and uptake of Na + without degrading the structure, [32][33][34] while the conductive amorphous carbon could construct a fast electric path. 35 Therefore, the structurally engineered Ni-CoSe 2 anode, integrating the merits of titanium dioxide quantum dots/amorphous carbon hybridized shell (Ni-CoSe 2 @TQDs/AC), can not only effectively buffer the strain and maintain the structural integrity but also allow fast and reversible transport of electrons/ions, resulting in increased reaction kinetics and high rate of Na storage.…”

In situencapsulation of iron oxide nanoparticles into nitrogen-doped carbon nanotubes as anodic electrode materials of lithium ion batteries

“…4a). 15 It was noticed that Fe 2+ also existed in the sample, which may be attributed to the considerable number of defect sites with low oxygen coordination bonds. Based on the different electronic states of N heteroatoms, the deconvoluted N 1s high-resolution spectrum contains peaks at 404.3 401.7, 400.9 and 398.7 eV representing four N species, which can be assigned as pyridinic oxide (16%), graphitic-N (21%), pyrrolic-N (25%) and pyridinic-N (38%), respectively (Fig.…”

“…10 Recently, various strategies have been developed to improve the electrochemical performances of transition-metal oxides, such as structural amelioration (e.g. monophasic and polyphasic synthesis), 11 crystallinity modulation (single crystal, polycrystal or amorphism), 12,13 defect engineering (surface and crystal heteroatom doping), [14][15][16] composition modification (hybridization with carbon or metal, changing the element valence, or reducing the inserted Li content), [17][18][19] morphological control (zero-, one-, two-, and three-dimensional structures, nanostructuring, porosity, structural hierarchy, and surface and interface regulation) [20][21][22] and so forth. These strategies inspired us to rationally design and synthesize an anode material system with a unique structure and morphology to enhance the electrochemical performance.…”