NOVELTY - A nonaqueous electrolyte solution comprises 0.01-3 %mass organic or inorganic compound having an oxalic acid skeleton, and 0.01-5 %mass isocyanate compound(s) (I). The nonaqueous electrolyte solution is provided in an electrical storage device comprising a positive electrode, a negative electrode containing lithium titanate having ratio of specific surface area equivalent diameter (DBET) to crystallite diameter (DX) of 3 or less as a negative electrode active material, and nonaqueous electrolyte solution.    USE - Nonaqueous electrolyte solution is used for electrical storage device (claimed) for mobile telephone, notebook computer, and electric vehicles e.g. hybrid electric vehicle, plug-in hybrid electric vehicle and battery electric vehicles.    ADVANTAGE - The nonaqueous electrolyte solution improves electrochemical characteristics of electrical storage device in a wide temperature range such as low-temperature discharge characteristics after high temperature preservation.    DETAILED DESCRIPTION - A nonaqueous electrolyte solution comprises 0.01-3 %mass organic or inorganic compound having an oxalic acid skeleton, and 0.01-5 %mass isocyanate compound(s) of formula (I). The nonaqueous electrolyte solution is provided in an electrical storage device comprising a positive electrode, a negative electrode containing lithium titanate having ratio of the specific surface area equivalent diameter (DBET) as calculated from the specific surface area measured by the BET method to the crystallite diameter (DX) as calculated using the Scherrer equation from X-ray diffractometry result of 3 or less as a negative electrode active material, and nonaqueous electrolyte solution obtained by dissolving an electrolyte salt into a nonaqueous solvent.    X=-R1-N=C=O or -R1-O-C(=O)-R2;    R1=1-6C linear or branched alkylene optionally substituted by halo;and    R2=1-6C alkyl optionally substituted by halo, 2-6C alkenyl, or 6-12C aryl.    An INDEPENDENT CLAIM is included for electrical storage device.