Methyl propyl carbonate: A promising single solvent for Li-ion battery electrolytes

Methyl propyl carbonate (MPC) solutions containing Li salts can be used as a single-solvent electrolyte without addition of ethylene carbonate (EC). Graphite electrodes can be cycled at high reversible capacity in MPC solutions containing LiPF₆ and LiAsF₆. The use of acyclic, unsymmetric alkyl carbonate solvents, such as ethyl methyl carbonate (EMC) and MPC in Li-ion based electrolytes, increases the stability of the graphite electrode. Whereas a small amount of EC is still needed as cosolvent in EMC solutions to obtain stable surface films on graphite electrodes, we show here that the surface films produced on graphite in MPC solutions (without added EC) are highly stable, allowing reversible Li-ion intercalation. To understand this trend, we investigated the surface chemistry developed on lithium and carbon electrodes in MPC solutions in conjugation with electrochemical studies.