Novel composite electrolyte additive for enhancing the thermal and cycling stability of SiO/C anode Li-ion battery

Abstract

SiO/C anode materials have gained significant attention due to their high specific capacity and environmental friendliness in high-energy-density lithium-ion batteries (LIBs). However, due to the volume effect generated during the long-term cycle, the battery capacity will decay rapidly and cause thermal safety problems. PFPN/TTFEB is employed as a compound electrolyte additive in this study to enhance the electrochemical performance and safety of Li/SiO@C batteries. The blank control electrolyte (BE) is the commercial electrolyte, which is 1.0 M LiPF6 dissolved in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a 3:7 vol/vol ratio. The battery with the PFPN/TTFEB addition demonstrated a substantially higher capacity retention rate than the battery with BE, increasing from 45.23 % to 74.34 %, as indicated by the electrochemical and characterization test results. This suggests that the cycling stability of the battery was improved by the synergistic influence of ethoxy(pentafluoro)cyclotriphosphazene (PFPN) and tris(2,2,2-trifluoroethyl) borate (TTFEB). In addition, a LiF-rich solid electrolyte interphase layer was observed on the surface of the anode, increasing interface stability by reducing the direct contact between the electrolyte and electrode. Differential scanning calorimetry, thermogravimetric analysis, and thermokinetic analysis revealed that the addition of PFPN/TTFEB increased apparent activation energy from 439.56 to 1090.01 kJ/mol and increased initial exothermic reaction temperature from 233.67 to 292.83 °C. The thermal stability of the battery also considerably increased, and the exothermic reaction was substantially delayed. Overall, the multifunctional electrolyte additive developed in this study offers a feasible pathway for developing LIBs with excellent cycling performance and safety.