Effect of Li plating during formation of lithium ion batteries on their cycling performance and thermal safety

The presented work focuses on the effect of different applied C-rates within the formation procedure on the performance and the thermal safety of lithium ion battery cells. The formation procedure is based on constant-current constant-voltage charging and constant-current discharging. Here, two different formation procedures were used characterized by the applied current rate of either 0.2C or 2C. The cells were investigated via electrochemical, microscopic and spectroscopic methods. Applying a C-rate of 2C shortens the formation to 1.5 h compared to 10.5 h at 0.2C for one formation cycle. However, also the occurrence of Li plating with an amount corresponding to (7.8 ± 0.3) mAh g−1NMC was observed. Based on those results, thermal safety properties of cells after 0.2C or 2C formation was analyzed under quasi-adiabatic conditions in an accelerated rate calorimeter. Within the margin of error, no influence of the C-rate during formation on the thermal safety could be detected. In addition, no difference in cell cycling performance could be observed. Therefore, the here determined amount of Li plating originating solely from the formation process does not lead to significant differences in cycling performance and thermal safety behavior for the here considered lithium ion battery cells. •Faster formation current rate is leading to Li plating in LIBs.•8 mAh g−1NMC of Li plating quantified by NMR spectroscopy and ICP-OES.•Small amount of Li plating without effect on performance and safety properties.•Li plating occurring during formation not necessarily obstacle for fast formation.