Abstract: The present invention relates to an electrolyte additive including a compound represented by Chemical Formula 1, an electrolyte including the electrolyte additive, and a secondary battery including the electrolyte. Chemical Formula 1: R1 and R2 are each independently an alkylene group having 1-5 carbon atoms; E1 is a bond, an alkylene group having 1-3 carbon atoms, or a cyclic carbonyl group, ether group, or ester group having 2-5 carbon atoms; R3 is a substituted or unsubstituted linear or cyclic carbonate group, carbonyl group, ether group, phosphate group, sulfonate group, or sulfate group having 2-5 carbon atoms; the substitution refers to substitution with one or more selected from F, Cl, Br, and I or an alkenyl group having 1-3 carbon atoms; E2 is a bond or a saturated or unsaturated alkylene group or ether group having 1-3 carbon atoms; and n is 0 or 1.

Abstract: The present invention relates to an electrolyte additive including a compound containing a substituent represented by Chemical Formula 1, an electrolyte including the electrolyte additive, and a secondary battery including the electrolyte. Chemical Formula 1: In Chemical Formula 1, P and O are phosphorus and oxygen, respectively; A is a bond or oxygen; Q is oxygen or an unshared electron pair; R1, R2, R3, and R4 are each independently hydrogen, a linear or branched alkyl group having 1 to 10 carbon atoms, an alkenyl group, an alkynyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxyalkyl group, a fluoroalkyl, or a cyclic sulfate; optionally, R1 or R2 is connected to R3 or R4 to form a double bond or a ring; n is an integer from 0 to 3; and * is a binding position.

Abstract: The present invention relates to an electrolyte additive, a battery electrolyte including the electrolyte additive, and a secondary battery, and more particularly, to an electrolyte additive including a compound represented by Chemical Formula 1, an electrolyte including the electrolyte additive, and a secondary battery including the electrolyte. According to the present invention, due to low charging resistance, charging efficiency and output may be improved. In addition, the present invention has an effect of providing a secondary battery having a long lifespan and excellent capacity retention at high temperature.