The present invention provide a non-aqueous electrolyte for use in static or non-flowing rechargeable electrochemical cells or batteries, wherein the electrolyte comprises a first deep eutectic solvent comprises a zinc salt, a second deep eutectic solvent comprising one or more quaternary ammonium salts, and a hydrogen bond donor. Another aspect of the present invention also provides a non-flowing rechargeable electrochemical cell that employs the non-aqueous electrolyte of the present invention.