Effect of LiPO2F2 Electrolyte Additive on Surface Electrical Properties of LiNi0.6Co0.2Mn0.2O2 Cathode

The electrolyte additive of LiPO2F2 was injected into 18,650 Li ion battery cells composed of LiNi0.6Co0.2Mn0.2O2/graphite at 25 °C to avoid the formation of the undesirable solid electrolyte interface (SEI) layer. The potential distribution on the cathode surface was studied using electric force microscopy. The average potential distribution on the surface of the cathode in the cell where the additive LiPO2F2 was injected showed ~ 100 mV higher potential than the average potential on the surface of the cathode in the cell without the additive. X-ray photoemission spectroscopy results showed that the average potential distribution characteristics were correlated with the chemical composition of the surface reactants. These results indicate that the LiPO2F2 additive controls the formation of the SEI layer on the surface of the LiNi0.6Co0.2Mn0.2O2 cathode during the electrochemical reaction in the cell and has the decisive effect of inhibiting the decomposition of LiPF6, which is the main component of the electrolyte solution. In this study, the addition of the LiPO2F2 additive to the electrolyte improves the electrochemical performance of the Li ion battery by improving the surface potential of the cathode surface and controlling the formation of the SEI layer on the surface of the LiNi0.6Co0.2Mn0.2O2 cathode.