Ethyl methyl carbonate (EMC) is an asymmetric aliphatic organic carbonate. It is a colorless transparent liquid widely used as an excellent solvent for lithium-ion battery electrolytes. EMC increases the solubility of lithium ions improving the capacity density and power of batteries. This compound has excellent thermal conductivity and low electrical resistance, extending the working temperature range of electrolytes, improving lithium batteries' safety, and prolonging their service life. EMC is usually obtained by metal oxide-catalyzed transesterification over dimethyl carbonate and diethyl carbonate. High percentage yields are obtained if the reaction is carried out in liquid or vapor phase[1].
Ethyl methyl carbonate (EMC) is a colourless transparent liquid with a slightly irritating smell. Fusing point-55 ℃, 109 ℃ of boiling points, water-insoluble, be dissolved in the organic solvent such as alcohol or ether, be a kind of broad-spectrum asymmetric carbon acid ester. Because have methyl and ethyl simultaneously, so have the characteristic of methylcarbonate and diethyl carbonate concurrently, mainly as solvent and organic synthesis intermediate. Used in recent years, the water-insoluble electrolytic solvent of lithium cells has a feature that specific inductivity is significant, and viscosity is small, strong to lithium salts solvability, and can improve the life of the battery and safety performance.
Alkyl carbonates find applications as solvents for lithium-ion battery electrolytes, and the use of high-quality battery grade electrolytes having shallow water (<10 ppm) and acid (<10 ppm) contents are critical for achieving high electrochemical performance. Ethyl methyl carbonate is majorly utilized as a co-solvent in the nonaqueous electrolyte. It enhances the energy density and discharge capacity of lithium-ion batteries.
Non-aqueous solvent for Li-ion batteries
This product has been enhanced for energy efficiency.
Currently, the synthesis of Ethyl methyl carbonate in open literature can be mainly categorized into phosgene method, carbonyl oxide method, and transesterification method. EMC synthesis from transesterification of DMC and EtOH is known for its mild reaction conditions, ease of control, and low environmental pollution, making it the most promising process route. Ethyl methyl carbonate is selectively synthesized from dimethyl carbonate and ethanol via catalytic reactive distillation ( RD) over heterogeneous MgO/HZSM-5. It is shown that 2.3%MgO/HZSM-5 catalyst has high catalytic activity with 99.4% conversion of ethanol ( EtOH) and 98.1% selectivity to EMC in an RD column[3].
Ethyl methyl carbonate enables the largest reversible capacity, best cycle stability, highest cycle Coulombic efficiency, lowest onset potential, smallest polarization, lowest self-discharge rate, and best rate performance from graphite compared to dimethyl carbonate and diethyl carbonate. Ethyl methyl carbonate forms a thinner layer of cathode electrolyte interface on the graphite surface with fewer Li–F and ROCO2Li species than with dimethyl carbonate and diethyl carbonate[2].
[1] Guido N. Rimondino , Fabio E. Malanca, Jesús A. Vila . “Atmospheric oxidation of ethyl methyl carbonate: Kinetics and reaction mechanism.” Journal of Photochemistry and Photobiology A-chemistry 444 (2023): Article 114994.
[2] Yao Wang. “Unlocking the True Capability of Graphite-Based Dual-Ion Batteries with Ethyl Methyl Carbonate Electrolyte.” ACS Applied Energy Materials 2 10 (2019): 7512–7517.
[3] Prof. Jianhua Lv. “Selective Synthesis of Ethyl Methyl Carbonate via Catalytic Reactive Distillation over Heterogeneous MgO/HZSM-5.” ChemistrySelect 4 24 (2019): 7366–7370.
