先进原位表征“投射”全固态电池的失效机理
日期：2021/09/23 - 2021/09/23
学术讲座：先进原位表征“投射”全固态电池的失效机理
主讲人：Dr. Ziyang Ning, University of Oxford
时间：2021年9月23日（周四）上午9:00-10:00
地点：交大密西根学院龙宾楼四楼454会议室
讲座摘要
All-solid-state batteries could deliver a step change in energy density and improved safety through the use of an alkali metal anode and a ceramic electrolyte. However, dendrites form at the anode that penetrate the ceramic electrolyte is one of the greatest challenges facing solid-state batteries. While dendrite formation on charging directly leads to short-circuit and cell failure, the formation of voids on discharging can also lead to interfacial contact loss and trigger dendrite initiation. To enable the use of an energy dense alkali metal anode, voids and dendrites both need to be fundamentally understood.
The process of stripping has been investigated as a function of current density and stack pressure in both Li/Li6PS5Cl/Li and Na/Na-β’’-alumina/Na cells, revealing the dominant role of metal creep in preventing void accumulation and cell failure. By using a combination of 3-electrode cells, scanning electron microscopy and X-ray tomography, we show that there is a critical stripping current density, above which voids will not only form at the interface but increase in number and size on cycling, eventually leading to dendrite formation on charge. The combined effect of stack pressure and temperature have been studied to better understand and potentially eliminate void formation on stripping. We show that by applying high stack pressure, or moderate pressure at higher temperature, higher current densities can be achieved with stable cycling.
For a better mechanistic understanding of Li dendrites, in situ phase-contrast X-ray tomography combined with spatially mapped X-ray diffraction have been employed to follow the ingress of Li into the ceramic electrolytes during Li plating. The studies show the significance of spallation cracks in the ceramic electrolyte near the Li anode and the propagation of transverse cracks across the electrolyte to the counter electrode. The transverse cracks can cross the entire cell before the Li metal reaches the counter electrode, resulting in short circuit. A model of Li metal ingress will be discussed. It considers the mechanism of Li formation within the ceramic electrolyte, the role of porosity and the subsequent propagation of cracks and Li through the electrolyte.
主讲人简介
In 2017, Dr. Ning graduated from Department of Materials Science and Engineering at Shanghai Jiao Tong University with a B.E. degree in Materials Science and Engineering. After graduation, Dr. Ning joined Department of Materials at University of Oxford for his Ph.D. degree and studied the degradation mechanisms and failure analysis of all-solid-state batteries under Prof. James Marrow and Prof. Peter Bruce’s supervision. His research interests are among all-solid-state batteries, interfacial characterisations, development of advanced in operando methodology, and failure analysis, to aid the large-scale application of all-solid-state batteries.