Monitoring lithium metal plating/stripping in anode free//NMC811 battery by in-situ X-rays diffraction

One of the main limitations to the application of anode free lithium battery is low Coulombic efficiency, this loss of capacity is due to irreversible processes, mainly the formation of dead lithium, the instability of electrolyte, etc. In this work, conventional x-ray diffraction technique was employed to monitor the lithium metal plating and stripping during cycling between 4.3 and 3 V using cells composed of 5 μm thick copper current collector and LiN0.8Co0.1Mn0.1O2 cathode. We have observed that the lithium metal was not completely stripped off from the copper substrate at the end of discharge at a slow cycling rate of C/24 even in the first 2 cycles. In addition, the lithium metal was still seen following a constant voltage period of 3V despite at its reduced amount. The observation of this unreacted lithium metal unveils one of the important degradation mechanisms of anode free lithium battery, thus provides essential information for finding solution to reduce/eliminate “dead” lithium metal and prolonging cycling life.