Succinonitrile as a Corrosion Inhibitor of Copper Current Collectors for Overdischarge Protection of Lithium Ion Batteries

Succinonitrile (SN) is investigated as an electrolyte additive for copper corrosion inhibition to provide overdischarge (OD) protection to lithium ion batteries (LIBs). The anodic Cu corrosion, occurring above 3.5 V (vs Li/Li(+)) in conventional LIB electrolytes, is suppressed until a voltage of 4.5 V is reached in the presence of SN. The corrosion inhibition by SN is ascribed to the formation of an SN-induced passive layer, which spontaneously develops on the copper surface during the first anodic scan. The passive layer is composed mainly of Cu(SN)2PF6 units, which is evidenced by Raman spectroscopy and electrochemical quartz crystal microbalance measurements. The effects of the SN additive on OD protection are confirmed by using 750 mAh pouch-type full cells of LiCoO2 and graphite with lithium metal as a reference electrode. Addition of SN completely prevents corrosion of the copper current collector in the full cell configuration, thereby tuning the LIB chemistry to be inherently immune to the OD abuses.