The electrochemical stability of copper substrate was studied in three different lithium-ion battery electrolytes. Cyclic voltammetry was used to study the oxidation-reduction behavior of copper in these electrolyte solutions. The reduction of electrolyte and its effect on the oxidation of copper was also studied. Bulk electrolysis was used to quantitatively study the dissolution of copper in dry electrolytes and in electrolytes doped with impurities of H2O or HE The stability of copper was closely related to the composition of the electrolytes. Impurities dramatically increased the oxidation tendency of copper.