Mechanical Properties of Lithium Metal for Next Generation Batteries

Recent technological innovations such as electrified vehicles and personal electronics have enabled by meaningful advances in lithium ion batteries. Due to long term investment in battery materials and manufacturing, this technology has improved at a relatively steady 8% per year (in terms of specific energy, Wh/kg) since introduction in 1991. To increase the rate of electrified vehicle adoption, revolutionary improvements in battery technology are needed beyond what is currently available. Currently, three chemistries comprise the next generation battery direction; solid-state (SS), lithium-sulfur and lithium-air. All of these chemistries would benefit from the use of lithium metal anodes as one of the primary means of improving energy density. A SS separator of comparable dimensions as a conventional polyolefin separator could lead to ~100% improvement in cell energy density by enabling metallic lithium anodes [1]. Despite the considerable interest and dependence on lithium anodes in future generation batteries, its mechanical properties are poorly understood. The successful integration of pure lithium metal anodes will require understanding and predicting its mechanical behavior under static and cycling conditions. Recently our group investigated the elastic, plastic and creep behavior or lithium metal [2]. This presentation will extend the scope from our previous study emphasizing general property characterization to more battery specific mechanical environments, specifically aspect ratio and strain speed. Modern lithium ion battery electrodes having large surface area to volume ratios yielding low aspect ratios which are very different than traditional mechanical testing (i.e. 2 to 4). Additionally there is growing interest in fast charge/discharge, resulting in relatively short periods of mechanical compression, again different from traditional strain speeds (i.e. 1x10 -3 sec -1 ). The impact of aspect ratio and strain rate on lithium’s mechanical properties will be shown. REFERENCES [1] Albertus, P. et al. Nature Energy, 3 ( 2018 ) 16-21. [2] Masias, A. et al. J. Mat. Sci. , 54(3) ( 2018 ), 2585-2600.