The Coulombic efficiency of metal deposition/stripping can be improved while also preventing dendrite formation and growth by an improved electrolyte composition. The electrolyte composition also reduces the risk of flammability. The electrolyte composition includes a polymer and/or additives to form high quality SEI layers on the anode surface and to prevent further reactions between metal and electrolyte components. The electrolyte composition further includes additives to suppress dendrite growth during charge/discharge processes. The electrolyte composition can also be applied to lithium and other kinds of energy storage devices.
ACKNOWLEDGMENT OF GOVERNMENT SUPPORT
 This invention was made with government support under Contract DE-AC0576RLO1830 awarded by the U.S. Department of Energy. The government has certain rights in the invention.