SUN Yuanyuan, WU Haiying, LUO Xuan, CHEN Cheng, YAN Xiaodan, GUO Jiali, ZHANG Lingzhi
A nitrile-containing organodisiloxane compound 2-methyl-4-(1,1,3,3,3-pentamethyldisiloxane) butanenitrile (DSMCN) was designed and synthesized as an efficient electrolyte additive for improving the electrochemical performance of high energy density NCM811 batteries. The oxidation potential of the compound was tested using linear scanning voltammetry (LSV), and the electrochemical performances of NCM811 cells with DSMCN additive, including the cycling, rate and high-temperature performance were investigated and compared with those with the base electrolytes without DSMCN. The results demonstrated that the capacity retention of NCM811/Li half cells at room temperature was improved from 80.93% of the base electrolyte to 94.89% after 200 cycles at 1 C, while the capacity retention at a high temperature of 55 ℃ was increased from 59.52% to 88.09%. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests revealed that DSMCN participates in forming a more stable, uniform, and dense cathode electrolyte interphase layer on the NCM811 electrode surface, which leads to improved electrochemical kinetics, reduced interfacial impedance, and enhanced Li+ diffusion and charge transfer at the electrode/electrolyte interface under both normal and high-temperature conditions, thereby improving the electrochemical performance of NCM811 batteries.