Electrolyte additive composition, electrolyte and lithium secondary battery

The invention relates to an electrolyte additive composition, an electrolyte and a lithium secondary battery. The electrolyte additive composition comprises a fluorine-containing pyridine compound with a structure as shown in a formula (I) and a phosphite ester compound with a structure as shown in a formula (II), wherein R1, R2, R3 and R4 are respectively and independently selected from hydrogen, halogen, C1-C20 alkyl, halogenated C1-C20 alkyl, C6-C26 aryl, halogenated C6-C26 aryl, amino, isocyano or alkoxy; r < 5 >, R < 6 > and R < 7 > are independently selected from alkyl groups with 1 to 20 carbon atoms, halogenated alkyl groups with 1 to 20 carbon atoms, aryl groups with 6 to 26 carbon atoms and halogenated aryl groups with 6 to 26 carbon atoms respectively; the mass ratio of the fluorine-containing pyridine compound to the phosphite ester compound is (3-10): 1. The electrolyte additive composition can improve the high-temperature performance of the battery and inhibit the acidity and chromaticity of the