NOVELTY - The separator-electrolyte layer product comprises: a porous thin-film separator (12) consisting of a porous polymer film, a porous mat, fabric, and/or paper made of polymer or glass fibers, where the separator has thickness of less than 500 mu m; and a non-flammable quasi-solid electrolyte (16) containing lithium salt dissolved in a first liquid solvent up to a lithium salt concentration of more than 3 M (mole/l). The porous thin-film separator is coated with the electrolyte so that the separator-electrolyte layer product exhibits a vapor pressure of less than 0.01 kPa when measured at 20 degrees C.    USE - The separator-electrolyte layer product is useful for a lithium battery (claimed), which is useful in an electric vehicle, a hybrid electric vehicle, and a portable electronic device such as laptop computers and mobile phones.    ADVANTAGE - The separator-electrolyte layer product has non-flammable, safe, and high-performing electrolyte, thus simply and cost-effectively preventing potential lithium metal dendrite-induced internal short circuit and thermal runaway problems in the battery, and enables the battery to exhibit an exceptionally high specific energy or high energy density, good resistance to dendrite formation, prolonged service life and high level of safety.    DETAILED DESCRIPTION - The separator-electrolyte layer product comprises: a porous thin-film separator (12) consisting of a porous polymer film, a porous mat, fabric, and/or paper made of polymer or glass fibers, where the separator has a thickness of less than 500 mu m and pores to allow for lithium ion migration; and a non-flammable quasi-solid electrolyte (16) containing a lithium salt dissolved in a first liquid solvent up to a lithium salt concentration of more than 3 M (mole/l). The porous thin-film separator is coated with the quasi-solid electrolyte so that the separator-electrolyte layer product exhibits a vapor pressure of less than 0.01 kPa when measured at 20 degrees C, a vapor pressure of less than 60% of the vapor pressure of the first liquid solvent alone, a flash point of at least 20 degrees C higher than a flash point of the first liquid solvent alone, a flash point of higher than 150 degrees C, or no detectable flash point. The lithium salt concentration is greater than 8.5 M and/or greater than a molecular ratio of 0.5. The electrolyte has a lithium ion transference number of greater than 0.7. The first liquid solvent contains a mixture of an organic liquid solvent and an ionic liquid solvent, where an organic liquid solvent-to-ionic liquid solvent ratio is greater than 1/1. The product is in a roll form. The first liquid solvent contains a mixture of a volatile organic solvent and an ionic liquid or a less volatile organic solvent. The porous thin-film separator contains electro-spun polymer nano-fibers.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a roll-to-roll electrolyte-separator production system.    Feeder roller (10)    Porous thin-film separator (12)    Dispenser (14)    Non-flammable quasi-solid electrolyte (16)    Winding roller. (24)