Electrolyte compositions comprising novel fluorine-containing carboxylic acid ester solvents are described. The fluorine-containing carboxylic acid ester solvents are represented by the formula R1—C(O)O—R2, wherein R1 is CH3CH2— and R2 is —CH2CHF2, R1 is CH3— and R2 is —CH2CH2CHF2, R1 is CH3CH2— and R2 is —CH2CH2CHF2, R1 is CHF2CH2CH2— and R2 is —CH2CH3, or R1 is CHF2CH2— and R2 is —CH2CH3. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.