| CPC H01M 50/129 (2021.01) [H01M 10/0525 (2013.01); H01M 10/0569 (2013.01); H01M 50/121 (2021.01); H01M 2300/0028 (2013.01)] | 4 Claims |
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1. A secondary battery comprising:
outer package members each having flexibility, the outer package members each including a thermal-fusion-bonding layer; and
a battery device contained in an inside of the outer package members, the battery device including a positive electrode, a negative electrode, and an electrolytic solution, wherein
the outer package members are sealed at a thermal-fusion-bonding part, the thermal-fusion-bonding part being formed by the thermal-fusion-bonding layers being thermal-fusion-bonded to each other,
the thermal-fusion-bonding layer includes polypropylene,
the electrolytic solution includes a solvent and an electrolyte salt,
the solvent includes a chain carboxylic acid ester,
the thermal-fusion-bonding layer has a thickness of greater than or equal to 25 micrometers and less than or equal to 60 micrometers,
the thermal-fusion-bonding part has a length of greater than or equal to 160 millimeters and less than or equal to 650 millimeters,
the thermal-fusion-bonding part has a width of greater than or equal to 3 millimeters and less than or equal to 6 millimeters,
a dimensional ratio defined by the thickness of the thermal-fusion-bonding layer, the length of the thermal-fusion-bonding part, and the width of the thermal-fusion-bonding part satisfies a condition represented by Expression (1),
a drawn amount of the outer package members is less than or equal to 7.8 millimeters, and
a content of the chain carboxylic acid ester in the solvent is greater than or equal to 30 volume percent and less than or equal to 60 volume percent,
0.16≤(T×L)/W≤0.32 (1)
where
(T×L)/W is the dimensional ratio,
T is the thickness in centimeters of the thermal-fusion-bonding layer,
L is the length in centimeters of the thermal-fusion-bonding part, and
W is the width in centimeters of the thermal-fusion-bonding part.
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