Free-standing hybrid films comprising of ultra-dispersed titania nanocrystals and hierarchical conductive network for ex
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llege of Chemistry and Chemical Engineering, Qufu Normal University, Jingxuan West Road NO.57, Qufu 273165, China State Key Laboratory of New Ceramics and Fine Processing, and Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China 3 School of Materials Science and Engineering, Liaocheng University, Hunan Road No. 1, Liaocheng 252000, China 4 Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China 2
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 17 September 2020 / Revised: 28 October 2020 / Accepted: 5 November 2020
ABSTRACT The construction of advanced electrode materials is key to the field of energy storage. Herein, a free-standing anatase titania (TiO2) nanocrystal/carbon nanotube (CNT) film is reported using a simple and scalable sol-gel method, followed by calcination. This unique free-standing film comprises ultra-small TiO2 nanocrystals (~ 5.9 nm) and super-aligned CNTs, with ultra-dispersed TiO2 nanocrystals on the surfaces of the CNTs. On the one hand, these TiO2 nanocrystals can significantly decrease the diffusion distance of the charges and on the other hand, the cross-linked CNTs can act as a three-dimensional (3D) conductive network, allowing the fast transport of electrons. In addition, the film is free-standing, without requiring electrode fabrication and additional conductive agents and binders. Owing to these above synergistic effects, the film is directly used as an anode in Li-ion batteries, and delivers a high discharge capacity of ~ 105 mAh·g−1 at high rate of 60 C (1 C = 170 mA·g−1) and excellent cycling performance over 2,500 cycles at 30 C. These results indicate that the free-standing anatase TiO2 nanocrystal/CNT film affords a superior performance among the various TiO2 materials and can be a promising anode material for fast-charging Li-ion batteries. Moreover, the TiO2/CNT film exhibits an areal capacity of up to 2.4 mAh·cm−2, confirming the possibility of its practical use.
KEYWORDS carbon nanotubes, free-standing, high rate, Li-ion batteries, TiO2, ultra-small
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Introduction
With an increase in population and subsequent environmental deterioration, it is important to develop “green and clean” vehicles. Electric vehicles recognized by the international agencies can meet these requirements, which has led to a sharp increase in the global demand of these vehicles in recent years [1, 2]. Currently, Li-ion batteries with high energy densities and excellent cycling lives are considered as one of the most promising storage devices to use in the commercially available electric vehicles. However, these electric vehicles are still restricted by a limited driving-range. There are two methods to address this issue. One is to further increase the energy densities of the Li-ion batteries by using electrode materials with high specific capacities. For example, Li-ion batteries with high
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