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反复充放电循环过程中碳包覆SiO和锂掺杂碳包覆SiO的结构和相变的比较

 

摘要

碳涂层SiOSiO-C)是一种高容量的负极材料,在初始充放电循环中会经历明显的容量下降。相反,最近开发的掺锂的SiOCLiSiOC)的电容降明显较小。为了解释这种差异,我们通过比较它们的Si结构和从固态幻角旋转核磁共振和Si K边缘X射线吸收获得的电子状态,对与这些材料的充放电循环相关的结构和相变进行了详细的研究及精细的结构测量。结果表明,在SiOC的情况下,充电过程中产生的Li4SiO4在初始充放电循环中的放电过程中会部分分解。这些生成和分解行为在前20个周期中最为强烈。我们认为,这种现象是在SiO-C初始循环中观察到不可逆容量增加的原因。另外,我们证实,LiSiOC的成分Li2SiO3在电化学上相对稳定,尽管其中一些在充放电循环中逐渐转变为Li4SiO4。一开始就存在Li2SiO3,这意味着与SiOC相比,充电过程中生成的Li4SiO4更少,我们相信这可以解释为在LiSiOC的初始循环中容量没有明显下降。


期刊摘要原文:

Comparison of the Structure and Phase Changes of Carbon-Coated SiO and Li-Doped Carbon-Coated SiO During Repeated Charge–Discharge Cycling

Takakazu Hirose, Kohta Takahashi, Takumi Matsuno, Yusuke Osawa, Masahiro Furuya, Reiko Sakai, Chinami Matsui and Hiroyuki Koide

Published 24 August 2020 ? ? 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited
Journal of The Electrochemical SocietyVolume 167Number 12 

Abstract

Carbon-coated SiO (SiO–C), which is a high-capacity anode material, experiences a significant capacity drop in the initial charge–discharge cycles. In contrast, Li-doped SiO–C (Li–SiO–C), which has been recently developed, exhibits a significantly smaller capacity drop. To explain this difference, we performed a detailed investigation of the structures and phase changes associated with the charge–discharge cycling of these materials by comparing their Si structures and electronic states obtained from solid-state magic-angle spinning nuclear magnetic resonance and Si K-edge X-ray absorption fine structure measurements. The results show that, in the case of SiO–C, the Li4SiO4 generated during charge is partially decomposed during discharge in the initial charge–discharge cycles. These generation and decomposition behaviors are most intense during the first 20 cycles. We believe that this phenomenon is the cause of the increased irreversible capacity observed in the initial cycles of SiO–C. In addition, we confirmed that Li2SiO3, a component of Li–SiO–C, is relatively stable electrochemically, although some of it gradually converts into Li4SiO4 during charge–discharge cycling. The presence of Li2SiO3 at the outset implies that less Li4SiO4 is generated during charging compared to SiO–C, which we believe explains the lack of a significant capacity drop in the initial cycles of Li–SiO–C.

下载文献原文

Hirose_2020_J._Electrochem._Soc._167_120523.pdf

2020年08月26日

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