Enhanced electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ cathode at high cutoff voltage by modifying electrode/electrolyte interface with lithium metasilicate

Developing high-voltage Li ion batteries (LIBs) is an important trend to meet the requirement of high energy density battery. However, high voltage will cause a series of problems harming the cycle performance of LIBs at the same time. This work is to investigate the effect of inorganic substance Li₂SiO₃ on the electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode at high cutoff voltage of 4.6 V. XRD result shows that the structure of NCM622 cathode material is not affected by mixing Li₂SiO₃. However, XPS and EIS tests indicate that Li₂SiO₃ has an evident influence on suppressing the decomposition of LiPF₆ and carbonate solvents at high voltage, reducing interfacial solid film impedance and modifying electrode/electrolyte interface. In addition, Li₂SiO₃ retards the transition metal dissolution by consuming HF. Therefore, it enhances the electrochemical properties of the NCM622 cathode significantly. The highest discharge capacity increases to 191.7 mA h g^-1 by mixing Li₂SiO₃, compared with the value of 180 mA h g^-1 in the case of NCM622 cathode. The NCM622 electrode mixed with Li₂SiO₃ also exhibits a better capacity retention of 73.4% after 200 cycles and a high rate capability at 20C with the value of 89 mA h g^-1, in contrast with 62.2% and 31 mA h g^-1 attained in the NCM622 cathode.