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It should work if you tin both of the surfaces then add more solder as necessary. A perfect guide is here:https://www.instructables.com/id/How-to-solder-the-secrets-of-good-soldering/
well not necessarily, if you are wanting 12v then the MAXIMUM voltage should be 12.6v as if overcharged lithium ion battery's are not very forgiving, furthermore you will need holders or solder wires to it and also a charging port but theoretically attaching wires works too but is not very user friendly at all. if you could tell me what it is you were wanting the battery for then i may be able to help a bit better.
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