Shimoyamada Atsushi, Yamamoto Kazuo, Yoshida Ryuji, Kato Takehisa, Iriyama Yasutoshi, Hirayama Tsukasa
Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587, Japan
Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587, Japan.
Microscopy (Oxf). 2015 Dec;64(6):401-8. doi: 10.1093/jmicro/dfv050. Epub 2015 Sep 2.
All-solid-state Li-ion batteries (LIBs) with solid electrolytes are expected to be the next generation devices to overcome serious issues facing conventional LIBs with liquid electrolytes. However, the large Li-ion transfer resistance at the electrode/solid-electrolyte interfaces causes low power density and prevents practical use. In-situ-formed negative electrodes prepared by decomposing the solid electrolyte Li(1+x+3z)Alx(Ti,Ge)(2-x)Si(3z)P(3-z)O12 (LASGTP) with an excess Li-ion insertion reaction are effective electrodes providing low Li-ion transfer resistance at the interfaces. Prior to our work, however, it had still been unclear how the negative electrodes were formed in the parent solid electrolytes. Here, we succeeded in dynamically visualizing the formation by in situ spatially resolved electron energy-loss spectroscopy in a transmission electron microscope mode (SR-TEM-EELS). The Li-ions were gradually inserted into the solid electrolyte region around 400 nm from the negative current-collector/solid-electrolyte interface in the charge process. Some of the ions were then extracted in the discharge process, and the rest were diffused such that the distribution was almost flat, resulting in the negative electrodes. The redox reaction of Ti(4+)/Ti(3+) in the solid electrolyte was also observed in situ during the Li insertion/extraction processes. The in situ SR-TEM-EELS revealed the mechanism of the electrochemical reaction in solid-state batteries.
具有固体电解质的全固态锂离子电池有望成为克服传统液态电解质锂离子电池所面临严重问题的下一代设备。然而，电极/固体电解质界面处较大的锂离子转移电阻导致功率密度较低，并阻碍了其实际应用。通过过量锂离子插入反应分解固体电解质Li(1+x+3z)Alx(Ti,Ge)(2-x)Si(3z)P(3-z)O12（LASGTP）制备的原位形成负极是在界面处提供低锂离子转移电阻的有效电极。然而，在我们的工作之前，仍然不清楚负极是如何在母体固体电解质中形成的。在这里，我们通过透射电子显微镜模式下的原位空间分辨电子能量损失谱（SR-TEM-EELS）成功地动态观察到了其形成过程。在充电过程中，锂离子逐渐插入到距负极集流体/固体电解质界面约400nm处的固体电解质区域。然后在放电过程中一些离子被提取出来，其余的离子扩散使得分布几乎均匀，从而形成负极。在锂插入/提取过程中还原位观察到了固体电解质中Ti(4+)/Ti(3+)的氧化还原反应。原位SR-TEM-EELS揭示了固态电池中的电化学反应机理。
