報告題目：Stress relaxation and battery
報告人：姜漢卿教授 美國亞利桑那州立大學
時間：2017年7月3日（星期一）16：00-17：00
地點：玉泉校區教12-118
報告摘要：
The successful employment of Li metal anode in Li-ion or Li-S batteries is a critical step towards realizing a cell specific density beyond 500 Wh/kg, doubling the present battery performance. While considerable progress has been made in recent years to suppress Li dendrite growth via various approaches, the long-standing issue of Li dendrite formation upon cycling has fully addressed the problem under real operation conditions. One critical and fundamental aspect has not been explored and appreciated yet, namely, electroplating-induced stress has significant role on the morphology of plated Li, which is in fact ubiquitous in metal plating. For example, it is long known that compressive stress in Sn film causes the formation and growth of Sn whiskers. It is unclear the role of stress plays in Li dendrite growth and moreover, there is no effective approach to control the stress in plated Li to mitigate Li dendrite growth.
Here we present a mechanism to release the electroplating-induced compressive stress in Li during plating through soft electrodes. Our experimental observations show that the morphology of plated Li on thin copper current collector supported by soft electrodes is round hump while on the contrary, it is filamentary dendrite on Cu foil. These observations suggest a new mechanism to potentially mitigate Li dendritic growth from the root cause by releasing the electroplating-induced compressive stress. A 3D soft scaffold was fabricated to apply the stress relaxation mechanism on Li-metal batteries under large current density. Over 98% coulombic efficiency was achieved for over 100 cycles in a half-cell configuration, which overwhelmingly outperforms copper current collectors. Using lithium iron phosphate as the cathode, full-cell characterizations exhibit superior cyclic stability with over 99.8% coulombic efficiency. It is hoped that the findings in this work will inspire many further studies on stress relaxation during electrochemical plating by opening up an unexplored front in the extensive pursuit of effective ways to mitigating Li dendrite growth, and gain practical attention to implement this strategy for Li metal-based batteries and possibly other metallic electrode materials.
