One‐Step Synthesis of Highly Oxygen‐Deficient Lithium Titanate Oxide with Conformal Amorphous Carbon Coating as Anode Material for Lithium Ion Batteries

Abstract

incorporation of conductive agents, [9][10][11] doping of metal ions, [12][13][14] and nanonization, that is, reduction in particle size. [15,16] Although all of these methods yielded notable results, our proposed alternative synthesis is greatly on-par, in addition to being a one-pot, facile, and inexpensive process which requires no additional precursors and processing-a very favorable route with manufacturing considerations.Chiang and co-workers summarized available electronic conductivity data for LTO, in which the defective-LTO (with oxygen vacancies) was of the highest reported electronic conductivity. [17] Therefore, it has gotten great interest and numerous researchers had engineered processes to generate oxygen vacancies in the LTO structure. [18][19][20] With amorphous carbon coating, Chen and co-workers demonstrated lower Li ion (Li + ) interfacial transfer resistance which dramatically enhanced the battery performance. [21] Altogether achieving a "double" effect, Wang et al. introduced nanosized LTO with surface modifications of Ti (III) and carbon with improved surface conductivity and restricted particle growth due to the carbonization of polyaniline (PANI); [22] however, they were not able to maximize the effects of oxygen vacancies by generating a low level; and their nonuniform carbon layers can possibly impede Li + transport, especially when graphitized. [23] Finally, the importance of these modifications in relation to the Li + interfacial charge-transfer resistance was not highlighted in the aforementioned studies.Herein, we propose a one-pot, facile, and extremely inexpensive strategy by using conventional solid-state precursors of lithium carbonate (Li 2 CO 3 ) and titanium oxide (TiO 2 ) in an ethanol solution, through which a high level of oxygen vacancies and conformal amorphous carbon coating were simultaneously achieved. The formation mechanism of the one-pot synthesized, highly oxygen-deficient, and amorphous-carbon-coated LTO, as well as the origin of its superior electrochemical properties, are elaborated with the aid of the ab initio calculation. The enhanced interfacial electrochemical properties as well as the stabilization of highly oxygen-deficient structure are attributed to the conformal amorphous carbon. The dramatic reduction of overall resistance was in the Li + interfacial charge transfer, which sheds light to an emerging importance of interfacial modification, is highlighted in this paper.The lithium titanate defect spinel, Li 4 Ti 5 O 12 (LTO), is a promising "zero-strain" anode material for lithium-ion batteries in cycling-demanding applications. However, the low-rate capability limits its range of applications. Surface modifications, for example, coating and defect engineering, play an intriguing role in interfacial electrochemical processes. Herein, a novel synthesis of highly oxygen-deficient "defective-LTO" anode material with highrate performance is reported. It is synthesized using conventional precursors via a one-pot thermal reduction process. A high level of ox...

Higher Than 90% Initial Coulombic Efficiency with Staghorn‐Coral‐Like 3D Porous LiFeO2−x as Anode Materials for Li‐Ion Batteries

“…17–0938). By careful examination of the XRD profiles, appreciable broadening and low‐angle shifting for the P‐LiFeO 2− x sample can be found compared to the B‐LiFeO 2 sample, indicating smaller particle/grain size and larger lattice parameters, [ 30 ] respectively. Rietveld analyses showed a good fitting with α‐LiFeO 2 structure (Figure S5, Supporting Information) and determined that the mean grain sizes were ≈40 nm for P‐LiFeO 2− x and 115 nm for B‐LiFeO 2 (Table S1, Supporting Information), and the corresponding lattice parameters were 4.198 and 4.160 Å (Table S2, Supporting Information), respectively.…”

Mobile Small Polarons Qualitatively Explain Conductivity in Lithium Titanium Oxide Battery Electrodes

“…For the in-plane conductivity we thus find a value of 95.3 mS/cm, while the significantly higher out-of-plane hopping barrier results in a much smaller conductivity of 17×10 −6 mS/cm. To put these results into context, even our lower bound for the conductivity of reduced LTO is already five orders of magnitude higher than the pristine material, 30 while our ideal upper bound is of the order of the ion conductivities in currently employed electrolytes. 31 Note that the estimate for the ideal conductivity rests on the assumption that there are no other, significantly higher barriers along the whole pathway of charge percolation through the crystal.…”

Synthesis and Progress of New Oxygen‐Vacant Electrode Materials for High‐Energy Rechargeable Battery Applications

“…C) Diagrammatic sketch of the defective LTO in the modified reactions under autogenic pressure at elevated temperatures (m‐RAPET) process. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

“…Similar to lithium‐ion batteries (LIBs), oxygen defects greatly improve the electrochemical performance of SIBs. Rechargeable lithium–oxygen (Li–O 2 ) batteries with nonaqueous electrolytes have been a focus of research in recent years due to their extremely high energy densities, which offer great possibilities for application as storage units in electric vehicles and application in electrical grids . Some developments regarding oxygen‐vacant materials, selected from the past years, are demonstrated in Figure .…”