Oxygen Defect and Cl<SUP>-</SUP>-Doped Modulated TiNb<sub>2</sub>O<sub>7</sub> Compound with High Rate Performance in Lithium-Ion Batteries
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(Published version)
Date
2023
Authors
Cui, P.
Zhang, P.
Chen, X.
Chen, X.
Wan, T.
Zhou, Y.
Su, M.
Liu, Y.
Xu, H.
Chu, D.
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Journal article
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ACS applied materials & interfaces, 2023; 15(37):43745-43755
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Abstract
TiNb<sub>2</sub>O<sub>7</sub> has attracted extensive attention from lithium-ion battery researchers due to its superior specific capacity and safety. However, its poor ion conductivity and electron conductivity hinder its further development. To improve the ion/electron transport of TiNb<sub>2</sub>O<sub>7</sub>, we report that chlorine doping and oxygen vacancy engineering regulate the energy band and crystal structure simultaneously through a simple solid-phase method. NH<sub>4</sub>Cl was used to realize Cl<sup>-</sup> doping and oxygen vacancy production. A Rietveld refinement demonstrates an effective substitution of Cl in the O sites of Nb-O octahedra, with an enlarged crystal plane spacing. The oxygen vacancies provide more active sites for lithium intercalation. The diffusion coefficient of Li<sup>+</sup> is inceased from 2.39 × 10<sup>-14</sup> to 1.50 × 10<sup>-13</sup> cm<sup>2</sup> s<sup>-1</sup>, which reveals the positive influence of Cl<sup>-</sup> doping and oxygen vacancies on the promoted Li<sup>+</sup> transport behavior. Charge compensation is introduced by the doping of Cl<sup>-</sup> and the generation of oxygen vacancies, leading to the formation of Ti<sup>3+</sup> and Nb<sup>4+</sup> and the adjustment of the electronic structure. DFT calculations reveal that TiNb<sub>2</sub>O<sub>7</sub> with Cl<sup>-</sup> doping and an O vacancy shows a metallic property with a finite value at the Fermi level, which is conducive to electron transfer in the electrode material. Benefiting from these advantages, the modified TiNb<sub>2</sub>O<sub>7</sub> presents superior rate performance with a commendable capacity of 172.82 mAh g<sup>-1</sup> at 50 C. This work provides guidance to design high-performance anode materials for high-rate lithium-ion batteries.
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Data source: Supporting information, https://doi.org/10.1021/acsami.3c08524
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Copyright 2023 American Chemical Society
Access Condition Notes: Accepted manuscript available after 1 October 2024