Large-Scale DFT Simulation of Li-atom Insertion and Extraction in Quinons@SWCNT Rechargeable Battery Cathodes
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.174
Large-Scale DFT Simulation of Li-atom Insertion and Extraction in Quinons@SWCNT Rechargeable Battery Cathodes Takahiro Tsuzuki1, Shuji Ogata1, and Masayuki Uranagase1 1
Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Nagoya, Aichi 466-8555, Japan
ABSTRACT The system of quinone molecules encapsulated in the single-wall carbon nanotube (SWCNT) has been proposed as a next-generation cathode electrode material for rechargeable battery. We investigate the complex interaction among the SWCNT, phenanthrene-quinone (PhQ), and Li atoms in the encapsulated system by using our original DFT code. We thereby find that the shape of the SWCNT changes significantly in the relaxed state depending on the extent of Li atoms inserted. The SWCNT shows a circular cylinder shape when no Li exists. With sufficient Li atoms inserted, the SWCNT is flattened. Substantial electron transfer from the PhQs to SWCNT is found. As for the dynamics of Li atoms in insertion or extraction process, we find that the Li atoms can take either of the two paths: one is along the inner wall of the SWCNT and the other is hopping on the PhQs. INTRODUCTION The lithium ion battery (LIB) is presently recognized as the indispensable energy storage device for portable electronic tools as the note-PC and cellular phone. The LIB is expected to be used also in heavy machines as the electric automobile. However, the current LIB has various deficiencies: for instance, it is expensive due to the containment of rare metals as Co in cathodes. Therefore, many researches have been putting great effort to develop a new electrode material with lower cost and improved performance. Recently the system of quinone molecules encapsulated in the SWCNT, which is free from rare metals, has been proposed as a next-generation cathode electrode material [1]. In the experiment [1], the phenanthrene-quinone (PhQ) was used. The PhQ molecule is composed of 14 C, 8 H, and 2 O atoms as drawn in Fig. 1(a); that is, it has 3 benzene rings. Single PhQ can capture as much as 2 Li atoms around the two O atoms as depicted in Fig. 1(b) through our simulation. Dissolution of the PhQ toward the electrolyte, which occurs for the simple aggregate, was suppressed significantly in the encapsulated system [1]. Despite the success of the encapsulated system as the electrode material, little is known about the configuration of the PhQs in the SWCNT and about the dynamics of Li-atoms in their insertion and extraction processes. Motivated by that, in the present study, we will address those issues through large-scale, first-principles molecular-dynamics simulation. We will consider the SWCNT with its diameter corresponding to the experimental value.
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