Effects of Electrolyte Additives on the Suppression of Mn Deposition on Edge Plane Graphite for Lithium-Ion Batteries

To suppress the degradation of graphite negative-electrodes that is caused by the dissolution of Mn-containing positive-electrode materials, the effects of additives that should strongly interact with Mn ion in electrolyte solution were examined. The edge plane of highly oriented pyrolytic graphite (HOPG) was used as a model graphite electrode, and its electrochemical properties were investigated by cyclic voltammetry and electrochemical impedance spectroscopy in Mn-ion-containing electrolyte solution. 100 ppm Mn ion dissolved in the electrolyte solution caused a significant decrease in redox currents due to the intercalation and de-intercalation reactions of Li + at an edge plane HOPG electrode, and a remarkable increase in interfacial resistance consisting of surface film resistance and charge transfer resistance due to Li + transfer at an interface between the electrode and electrolyte solution. This performance deterioration could be effectively suppressed by the addition of a certain type of cyclic ether to the electrolyte solution. The influence of the additive concentration on interfacial resistance was also investigated.