| 摘要 |
PROBLEM TO BE SOLVED: To obtain high capacity, high volume energy density, and excellent low temperature characteristics by mixing at least one different kind of nonaqueous solvent to a mixture of ethylene carbonate and dimethyl carbonate of characteristic composition and a specified weight ratio as the nonaqueous solvent, and forming a battery in a flat shape having a thickness less than specified. SOLUTION: As the electrolyte of a nonaqueous system secondary battery, a nonaqueous electrolyte containing a lithium salt in a nonaqueous solvent mainly comprising ethylene carbonate(EC) and dimethyl carbonate(DMC) is used. The total content of EC and DMC is 55-90%, preferably 60-90% based on the weight of the total solvent. DMC/EC (weight ratio) is 1 or more but preferably 3 or less. Methyl ethyl carbonate is added to EC and DMC as a third component to improve low temperature characteristics. The nonaqueous system secondary battery is formed in a flat shape having a thickness less than 12 mm. |
