M A Koronfel, A Omirkhan, H Yadegari, D Thornton, W Xue, J S Zhang, L Guo, J Nelson Weker, J F W Mosselemans, M Kulzick, I E L Stephens, M P Ryan
Copper is used as the anode current collector in lithium-ion batteries, as well as the electrode itself in other types of lithium batteries. It is nominally a stable material in the organic electrolytes under normal battery operating potentials. Copper dissolution in lithium battery electrolytes has been extensively shown to occur at potentials attainable only in over-discharge conditions. However, in this work, copper dissolution is shown to occur even under normal cycling conditions, contrary to thermodynamic prediction. Utilising the high chemical sensitivity of X-ray absorption spectroscopy, copper oxidation state and concentration are quantified in operando. The results raise concerns about the impact of copper on battery efficiency, lifetime and safety, along with resulting implications on battery cycling.