In-operando evaluation of the effect of vinylene carbonate on the insulating character of the solid electrolyte interphase

• The amount of VC (2% and 5% vol.) present in solution did not influence the final insulating character of the SEI;
• Earlier decomposition of VC leads to the formation of an electronically insulating layer starting from 1.3 V vs. Li/Li+;
• The early VC decomposition does not lead to the formation of a homogeneous insulating SEI layer;
• To form a homogeneous insulating SEI cathodic potentials below 0.8 V vs. Li/Li+ have to be reached even in presence of VC.

The solid electrolyte interphase (SEI) is an electronic insulating layer which highly affects the performance of lithium-ion batteries, especially when electrodes with low (de-)intercalation potentials such as graphite are employed. The formation of the SEI was investigated in-operando on graphite when vinylene carbonate (VC) was present as an additive in solution using feedback-mode SECM. The potential at which the surface started to become insulating was at 0.8 V vs. Li/Li+ in VC-free electrolytes, while it was at 1.3 V in VC-containing electrolytes. Nevertheless, potentials more cathodic than 0.8 V have to be reached to form a homogeneous SEI. No influence in the electronic properties of the formed SEI with different concentrations of VC was observed.