First-principles XANES simulation for oxygen-related defects in Si-O amorphous materials
First-principles XANES simulation for oxygen-related defects in Si-O amorphous materials
复制标题
DOI：
10.1016/j.commatsci.2021.110555
复制
发表时间：
2021-08
影响因子：
3.3
通讯作者：
Wataru Katayama;T. Tamura;Yuya Nishino;Hirose Takakazu-
中科院分区：
文献类型：
--
作者：
Wataru Katayama;T. Tamura;Yuya Nishino;Hirose Takakazu-
为了了解锂离子电池非晶态负SiO(a-SiO)电极在初始充电过程中的化学反应，我们用第一原理投影增广波(PAW)方法模拟了氧化硅晶体和玻璃中氧过剩缺陷的OK边X射线吸收近边结构(XANES)谱。氧过量缺陷，包括氧桥键(OBB)和过氧键(POL)组态，重现了在所制备的a-SiO材料的实验光谱中观察到的预边峰。结果表明，对OBB和POL构型有贡献的电子态是OO键的σ∗态，对于O2分子是OO键的π∗态。这些缺陷的形成能分布在非晶态结构中，在a-SiO中发现了形成能较小的POL组态。此外，O2分子可以存在于a-SiO_2中，而a-SiO_2中的O2分子则结合到键合网络中。通过Li+离子的插入，前缘峰消失，在高能区出现弱峰。这与所制备的a-SiO_2的O-K边X射线衍射峰在初始充电过程中消失的实验结果相一致。A-SiO中的POL构型与Li+离子在初始充电过程中的化学反应被认为对改善循环特性起到了重要作用。
To understand the chemical reaction during the initial charging in an amorphous negative SiO (a-SiO) electrode for Li-ion batteries, we simulated the O K-edge X-ray absorption near-edge structure (XANES) spectra for oxygen-excess defects in silicon oxide crystals and glasses using the first-principles projector augmented-wave (PAW) method. Oxygen-excess defects, including the oxygen bridge-bonded (OBB) and peroxy linkage (POL) configurations, reproduce the pre-edge peak observed in the experimental spectrum of the as-prepared a-SiO material. It was found that the electronic states contributing to the pre-edge peaks are the σ∗ state of the OO bond for the OBB and POL configurations, and the π∗ state of the OO bond for an O 2 molecule. The formation energy of these defects is distributed within the amorphous structure, and POL configurations with small formation energies were found in a-SiO. In addition, O 2 molecules can exist in a-SiO 2, whereas those in a-SiO are incorporated into the bond network. Through the insertion of Li+ ions, the pre-edge peak disappears, and weak peaks appear in the higher-energy region. These correspond to the experimental results in which the pre-edge peak in the O K-edge XANES of the as-prepared a-SiO disappeared during the initial charging. The chemical reaction between POL configurations in a-SiO and Li+ ions during the initial charging is thought to play an important role in improving cycle characteristics.