Performance of thin-film lithium energy cells under uniaxial pressure

Abstract

The objective of this study was two-fold. The first objective was to determine if the all-solid-state thin-film lithium energy cells could withstand the minimal 550 kPa uniaxial pressure required for composite manufacturing, which both specimens successfully did. The second objective was to determine the upper boundary uniaxial pressure limit of operation for the all-solid-state thin-film lithium energy cells. The two all-solid- state thin-film lithium energy cells tested in the present study under uniaxial pressure performed well even when subjected to uniaxial pressures up to about 2.0 MPa. However, pressures higher than this value led to their degradation. The observed degradation was due to the mechanical failure of the sealant. Above this pressure, the sealant was squeezed out of the space between the two mica substrates and the lithium-metal anode layer, which in turn allowed the ambient air to penetrate into the energy cell core, thus leading to the rapid degradation of the charge and discharge performance and the ultimate demise of the energy cell. We found out that, within the observed range, uniformly distributed packaging characteristics, we found that allsolid- state thin-film energy cells charge/discharge cycles under upwardly increasing uniform uniaxial pressure are extraordinarily robust and resilient to the effects of uniaxial, uniformly distributed uniaxial pressure had little or no effect on the charge/discharge performance of the all-solid-state thin-film lithium energy cells. Other power charge/draws outside of 1 mAh were not of interest in this study for the reasons already pointed out, albeit that they may be considered for future studies. Apart from other considerations for failure due to the current and constant power charge/sink of 1mAh. If the overall structure of the energy cell is mechanically robust, i.e., of high structural integrity, the maximum pressure that can be imposed is expected to be much higher than the maximum values noted earlier. The present study indicates that all-solidstate thin-film energy cells can be used as an integral part of a load-bearing multifunctional, smart material structure if their packaging is of sufficiently high structural integrity. Hence, the goal of using fiber reinforced laminated composites as the packaging material for all-solid-state thin-film batteries in multifunctional smart materials structures is well within reach.