您将学到什么：
- 研究人员如何使用X射线显微图像成像在充电/放电期间看电池内部。
- Results obtained using the synchrotron-based technology.
在研发，测试和评估方面，电池单元出现了有趣的困境。一侧，很容易观察到它们最重要的终端电压，电流流量和温度参数。另一方面，他们的内部状况和工作非常困难，尤其是在实时。但是，了解内部发生的事情对于改善电池性能和进步至关重要。
Now, a multi-institution team led by a group at Georgia Institute of Technology (Georgia Tech) including Argonne National Laboratory has advanced a technique for looking inside the battery cell while it’s being charged and discharged. This X-ray microtomography imaging is similar to a medical CAT scan (note:in operandorefers to a scan while the test subject is “operating” and fully functioning rather than non-functioningin situor “on site”).
The team was able to observe the internal “evolution” of the materials inside solid-state lithium batteries, which use solid materials to replace the flammable liquid electrolytes in existing lithium-ion batteries. They created detailed, three-dimensional information that could help improve the reliability and performance of the batteries.
TheOperandosynchrotron X-ray “computed-microtomography” imaging revealed how the dynamic changes of electrode materials at lithium/solid-electrolyte interfaces determine the behavior of solid-state batteries. The researchers found that battery operation caused voids to form at the interface, creating a loss of contact that was the primary cause of failure in the cells.
They noted that despite progress in solid-state battery engineering, any advanced understanding of the chemo-mechanical phenomena that controls electrochemical behavior and stability at solid-solid interfaces remains limited compared to solid-liquid interfaces. Using synchrotron-based X-ray computed microtomography, they investigated the changes in lithium/solid-state electrolyte interfaces during battery cycling in a test cell at relatively high current densities of 1 mA/cm2and 4 mA/cm2(Fig. 1)。
1.此处显示的单元格的较小，修改的版本用于在循环过程中对这些材料进行图像。
这些测试提供了对空隙形成，相间生长和体积变化之间复杂相互作用的见解，所有这些都决定了细胞行为。他们能够直接和动态地可视化锂剥离过程中空隙的形成，并发现锂和固态电解质之间的接触接线丧失（li10SnP2S12) was the primary cause of cell failure(Fig. 2)。
2. Operando X-ray imaging of cells at two current densities. (a) Schematic of the custom X-ray tomography cell used to cycle Li/LSPS/Li cells during operando experiments. (b-c) Galvanostatic voltage curves measured during operando experiments at 4 mA/cm2and 1 mA/cm2， 分别。（D-E）在4 mA/cm循环之前重建的横截面图像2and 1 mA/cm2。深色对比的区域是锂电极，而灰度是LSPS电解质。（f）以1 mA/cm循环之前的LI/LSP界面放大了LI/LSP的界面2, taken from the blue-boxed region in (e). Voids in the left half of the image are overlaid with red for easier visualization, and the red dashed line on the left side demarcates the interphase boundary. The right half of the image is unmarked. (g-h) The same cross-sectional images as those shown in (d-e) after the electrochemical cycling procedure shown in (b-c). The formation of a darker gray interphase can be seen at the interfaces, along with morphological changes in the lithium electrodes. (i) Magnified cross-section of the same interface as shown in (f) after one full cycle at 1 mA/cm2。The volume of voids at the interface has increased significantly (overlaid with red on the left half of the image), along with growth of the interphase (demarcated by the red dashed line in the left half of the image).
They were also able to construct a three-dimensional view of the lithium/solid-electrolyte interface within the battery(Fig. 3)。
3. A three-dimensional view of the lithium/solid-electrolyte interface within the battery was reconstructed with X-ray tomography.
团队负责人Matthew McDowell是George W. Woodruff机械工程学院和材料科学与工程学院的助理教授，他说：“我们能够确切地了解界面处的空隙和位置，然后将其与之相关联，然后将其联系起来电池性能。”
Details of the project with numerous charts, data, process arrangement, and conclusions are in theirNature Materialspaper “使用Operando X射线断层扫描将空隙和相间演变与固态电池中的电化学联系起来“ 随着补充信息。The primary paper is behind a paywall, but it’s also available这里。该研究使用了Argonne National Laboratory运营的高级光子来源的资源。
Reference
NPGAsia Materials, “原位/基于锂离子电池研究的基于基于同步加速器的X射线X射线技术”（2018）
