Electrolyte having eutectic mixture and nitrile compound, and electrochemical device containing the same

An electrolyte, comprising:

• (a) a eutectic mixture of an amide compound represented by the following chemical formula 1 or 2 and an ionizable lithium salt;
• and
• (b) a nitrile compound:
• where R, R1 and R2 are hydrogen, halogen or any one selected from the group consisting of alkyl group, alkylamine group, alkenyl group, alkoxy group, alkoxyalkyl group and aryl group, which is unsubstituted or substituted with halogen and has 1 to 20 carbons, independently, and
• X is any one selected from the group consisting of silicon, oxygen, nitrogen, phosphorus and sulfur, wherein i) m is 1 when X is oxygen or sulfur, ii) m is 2 when X is nitrogen or phosphorus, and iii) m is 3 when X is silicon,
• where R and R1 is hydrogen, or any one selected from the group consisting of alkyl group, alkylamine group, alkenyl group, aryl group, alkoxy group, alkoxyalkyl group and allyl group, which is unsubstituted or substituted with halogen and has 1 to 20 carbons, independently,
• X is any one selected from the group consisting of silicon, oxygen, nitrogen, phosphorus and sulfur, wherein i) m is 0 (zero) when X is oxygen or sulfur, ii) m is 1 when X is nitrogen or phosphorus, and iii) m is 2 when X is silicon, and
• n is an integer of 1 to 10.