Lithium ion battery electrolyte additive

An electrochemical energy storage device electrolyte comprising:

• an aprotic organic solvent system;
• a metal salt;
• and at least one silyl-based compound additive according to the formula:
• wherein:
• X is independently oxygen or sulfur;
• wherein at least one X is sulfur;
• m and n are either 0, 1, 2 or 3;
• wherein m and n must sum equal to 3;
• R1 and R2 are independently C1-C12 substituted or unsubstituted alkyl groups, or C6-C14 aryl groups;
• wherein the hydrogen atoms can be unsubstituted or can be a halogen, alkyl, alkoxy, perfluorinated alkyl, silyl, siloxy, silane, sulfoxide, amide, azo, ether, and thioether group or combinations thereof;
• and
• R3, R4, R5 are independently selected from hydrogen, C1-C12 alkyl groups, heteroalkyl groups, perfluoroalkyl groups, alkenyl groups, phenyl or alkoxy groups.