Capturing the differences between lithiation and sodiation of nanostructured TiS2 electrodes
Capturing the differences between lithiation and sodiation of nanostructured TiS2 electrodes
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DOI：
10.1016/j.nanoen.2019.06.016
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发表时间：
2019-09
期刊：
影响因子：
17.6
通讯作者：
P. Hu;Bo Wang;Dongdong Xiao;K. Aifantis
中科院分区：
文献类型：
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作者：
P. Hu;Bo Wang;Dongdong Xiao;K. Aifantis
本研究选择tis2作为模型电极材料，研究了钠离子电池层状阴极的电化学性能和力学性能之间的关系。采用NaFP6in EC/DMC作为电解液，可以获得文献中记录的最有希望的电化学性能，即0.2 C时的可逆容量为203 mAh g - 1at， 10 C时的可逆容量为88 mAh g - 1at，在50次循环中容量保持率为92%。尽管性能很好，但在长期循环过程中，容量仍然会衰减。原位x射线衍射和高分辨率透射电镜成像显示，tis2沿方向发生了17.7%的大膨胀，在钠化/脱钠过程中发生了不可逆的相变，导致了严重的机械应变和晶内裂纹。相比之下，tis2在锂离子电池中的机械稳定性明显更高。实验结果在连续介质力学模型中得到解释，该模型揭示了离子插入tis2和原始tis2之间的最大有效冯米塞斯应力在钠化过程中比锂化过程中高出约四倍，这表明电极在钠化过程中更容易失效/断裂。
In this study TiS2is chosen as a model electrode material to investigate the relationship between the electrochemical and mechanical performance of layered cathodes for Na-ion batteries. Employing NaFP6in EC/DMC as the electrolyte allowed for the most promising electrochemical properties recorded in the literature, namely a reversible capacity of 203 mAh g−1at 0.2 C and 88 mAh g−1at 10 C with a capacity retention of 92% over 50 cycles. Despite this promising performance the capacity still decayed during long term cycling. In-situ x-ray diffraction and high-resolution transmission electron microscopy imaging revealed that TiS2underwent a large expansion of 17.7% along thecdirection and irreversible phase transformations took place during the sodiation/de-sodiation process, which lead to severe mechanical strains and intragranular cracks. In comparison, the mechanical stability of TiS2in Li-ion cells was significantly higher. The experimental results are interpreted within a continuum mechanics model which revealed that the maximum effective von Mises stress that is present at the interface between the ion-intercalated TiS2and pristine TiS2is about four times higher during sodiation than lithiation indicating that the electrode is more susceptible to failure/fracture during sodiation.